Table of contents

The 13th International Conference on Rapidly Quenched and Metastable Materials (RQ13) took place in Dresden, Germany, 24–29 August 2008. It belongs to the triennial series of RQ meetings with a long tradition, starting in 1970 – Brela, 1975 – Boston, 1978 – Brighton, 1981 – Sendai, 1984 – Würzburg, 1987 – Montreal, 1990 – Stockholm, 1993 – Sendai, 1996 – Bratislava, 1999 – Bangalore, 2002 – Oxford, 2005 – Jeju Island. RQ13 was hosted by the Leibniz Institute of Solid State and Materials Research, IFW Dresden.

Research on rapidly quenched and metastable materials is stimulated by the high demand for new materials with unique mechanical, chemical and physical properties. Topics of RQ13 conference have fallen into three parts: synthesis and processing, materials and properties, and applications of rapidly quenched and metastable materials.

These topics cover exiting developments from the traditional field of rapidly quenched metals to newly emerging areas such as bulk metallic glasses and nanostructured materials. As such, the presentations reported on recent experimental and theoretical achievements in the fields of metastable materials, quasicrystals, nanometer-scale materials, magnetic materials, metallic glasses, solid state reaction, undercooling and modeling. As in the previous proceedings (RQ12), the largest number of papers is dedicated to bulk metallic glasses and magnetic materials. With respect to property characterization and applications, there are great attempts for use and application of these materials, particularly for bulk metallic glasses, as well as for further design and optimization of properties.

The RQ13 conference attracted a total of 381 abstracts submitted by scientists from 38 different countries. The conference included 8 plenary talks and 25 invited keynote talks. In addition, 163 regular oral contributions were presented and more than 180 posters were presented. It was a particular highlight of the conference that Dr Ho Sou Chen was awarded the RQ distinguished Fellowship Award for his pioneering research on rapidly quenched and metastable materials and his outstanding contributions to the expansion of the RQ community.

It is our pleasure to thank the members of the International Advisory Committee for their valuable help, especially for proposals for plenary and keynote speakers. 129 abstracts were submitted for publication and 119 papers were accepted to be included in the Proceedings. All the papers were reviewed. We would like to express our thanks to all referees for their efficient and prompt efforts. We acknowledge particularly support from the German Society of Research (DFG), the European Office of Aerospace Research and Development, the Dresden University of Technology and the Leibniz Institute for Solid State and Materials Research in Dresden. Finally we are grateful for industrial support from ZOZ, Alfa Aeser, AXO Dresden, Edmund Bühler, Evico magnetics, Goodfellow, RSP and Light Metals Centre.

The International Advisory Committee met during the conference and decided to convene the next conference in Brazil, in August 2011. We wish the organizers of RQ14 great success and look forward to meeting you in Brazil.

Ludwig Schultz (FW Dresden) Jürgen Eckert (IFW Dresden) Livio Battezzati (Universita di Torino) Mihai Stoica^* (IFW Dresden) Guest Editors Dresden, 5 December 2008 (^*Corresponding author; e-mail address: m.stoica@ifw-dresden.de)

Alloy optimization in the Ni_80-xCr_xP₁₆B₄ (x = 9–30 at%) alloy system was conducted in order to achieve low T_g, T_x and a large ΔT_x. From this study, the Ni₆₅Cr₁₅P₁₆B₄ glassy alloy was found to be the optimal alloy. The static and potentiodynamic corrosion behaviours of this alloy were measured. As a result of polarization measurements, it was found that the current density of the non-polished glassy alloy sample was smaller than that of a SUS316L sample. By contrast, the current density of the surface-polished glassy sample was slightly larger than that of the SUS316L sample in the voltage range of 0.3–0.8 V. A bipolar plate was successfully produced by hot-pressing the glassy alloy sheet in a supercooled liquid state. The I-V characteristics of a single cell with the glassy bipolar plates were measured.

Fabrication conditions of the Pd₄₇Ni₄₇Si₆ amorphous ribbons designed for functional application as a filler metal in joining metallic elements have been developed. Particular attention in developing fabrication technology was drawn to the question of elimination of ribbon contamination with carbon, the presence of which has disadvantageous effect on the quality of the amorphous PdNiSi brazes. Thermodynamic properties of the PdNiSi braze were examined and its characteristic temperatures T_S and T_L have been determined. Density and resistivity of the ribbons have been measured. Moreover, brazing tests were conducted using the brazing alloys fabricated under this work, designed for joining such metals as ST3S constructional steel, tungsten, molybdenum and tantalum. The strength tests were also carried out confirming very good functional properties of the developed brazing alloy.

We have clarified relation between embrittlement behavior and crystallization or structural relaxation behavior of Zr₅₅Cu₃₀Al₁₀Ni₅ and Ti_47.4Cu₄₂Zr_5.3TM_5.3(TM = Ni, Co, Fe) metallic glasses. The embrittled samples were prepared by isothermal annealing at various temperatures and times. The embrittlement behavior of the metallic glasses was compared with the crystallization and structural relaxation behavior estimated by kinetic calculation. In the present study, we have clarified as follows, (1) The Zr₅₅Cu₃₀Al₁₀Ni₅ metallic glass becomes brittle with precipitation of crystal, and the behavior agrees with the kinetic calculation of crystallization. (2) The Ti_47.4Cu₄₂Zr_5.3Ni_5.3 metallic glass is embrittled with structural relaxation, and the behavior agrees with the kinetic calculation using DSC-heat flow of glass transition. (3) The Ti_47.4Cu₄₂Zr_5.3TM_5.3(TM = Co, Fe) metallic glasses are also embrittled with structural relaxation, although embrittlement behavior of these glasses is influenced more sensitively by the structural relaxation compared with the Ti_47.4Cu₄₂Zr_5.3Ni_5.3metallic glass.

The electromagnetic (EM) wave absorption properties with a variation of crystallization temperature have been investigated in a sheet-type absorber made of the amorphous Fe₇₃Si₁₆B₇Nb₃Cu₁Finemet powder. With the variation of the annealing temperature, the magnetic and dielectric properties of the crystallized Fe-based absorber with a nano-structure were changed. The complex permittivity increased with increasing the annealing temperature, whereas the complex permeability was maximized after annealing at 530°C for 1 hour. The absolute value of the reflection parameter, |S₁₁|, increased with increasing annealing temperature of the nanocrystalline alloy powder. On the contrary, the transmission one, |S₂₁|, showed the highest value after annealing at 530°C for 1 hour, which is regarded as the optimum temperature for the improvement of EM wave absorption properties.

In this work, the effect of laser welding on the microstructure was studied for three Advanced High Strength Steels: transformation induced plasticity steel (TRIP), dual phase steel (DP) and martensitic steel. Two sheets of the same steel were laser welded and a microstructural study was performed by optical microscopy, scanning electron microscopy and X-ray diffraction. For all samples the welded zone was constituted by martensite and the heat affected zone shows a continuous change in microstructure depending on temperatures reached and on the different cooling rates. The change in mechanical properties in the welded area was followed by Vickers micro-hardness measurements. Quasi binary phase diagrams were calculated and, according to position of T₀ lines, it was deduced that austenite is the primary phase forming during rapid solidification for all steels.

The reduction of total vehicle weight and lowering of moving masses within the engine are key elements to overcome future emission challenges of the automotive industry. Within a German BMBF funded project the melt spinning technology will be driven to a series production status. The very fast cooling condition of the melt leads to a nano-structure of the aluminium material. This results in new material properties of known alloys. The strength increases dramatically without lowered forming behaviour. With this process the freedom of designing complex alloys is very flexible. Different alloys have been investigated for several applications, where high strength at room and elevated temperatures and/or high wear resistance is required. This paper presents some results regarding the processing, microstructure and mechanical properties of a developed Al-Ni-Fe alloy. This joined research project with partners from the automotive industry as well as automotive suppliers and universities is funded by the German BMBF "NanoMobile" Program under Project number 03X3008.

TiMn alloy was prepared by mechanical alloying and subsequently consolidated by spark plasma sintering (SPS) technique for exploration of biomedical applications. The microstructures, mechanical properties and cytotoxicity of the TiMn alloys were investigated in comparison with the pure Ti and Mn metals. Ti8Mn and Ti12Mn alloys with high relative density (99%) were prepared by mechanical alloying for 60 h and SPS at 700 °C for 5 min. The doping of Mn in Ti has decreased the transformation temperature from α to β phase, increased the relative density and enhanced the hardness of the Ti metal significantly. The Ti8Mn alloys showed 86% cell viability which was comparable to that of the pure Ti (93%). The Mn can be used as a good alloying element for biomedical Ti metal, and the Ti8Mn alloy could have a potential use as bone substitutes and dental implants.

The corrosion behaviour of (Ni₆₀Nb₄₀) and Ni-Nb-M (M = Zr, Mo, Ta & Pd) meltspun ribbons was studied by electrochemical and chemical methods at PEMFC environments. The doping of Mo, Pd and Ta decreased the corrosion and passivation current densities, whereas the addition of Zr induced the opposite effect. To understand the change of corrosion behaviour induced by these additional elements, the surface composition and surface oxide layer thickness were analyzed by XPS method.

We are proposing global carbon dioxide recycling to use solar energy for all people in the whole world. The electricity will be generated by solar cell in the deserts and used for production of hydrogen by seawater electrolysis at the nearby desert coasts. Hydrogen with no existing infrastructures for transportation and combustion will be converted to methane at the desert coasts by the reaction with carbon dioxide captured by energy consumers. Among systems in global carbon dioxide recycling, seawater electrolysis and carbon dioxide methanation have not been performed industrially. We tailored anodes for oxygen evolution without chlorine formation in seawater electrolysis, effective cathodes for hydrogen production and catalysts for methane formation by the reaction of carbon dioxide with hydrogen.

Magnetoelastic anisotropies arising from substrate induced strains provide a way to optimize the magnetic properties of nanoparticles. A possible way to induce such anisotropies is the deposition of clusters on substrates which are deformed or otherwise expanded subsequently. However, the experimental determination of strain in nanoparticles is complicated by the low diffraction intensities. We used the molecular dynamics simulation technique to determine the deformation of Co particles deposited on Cu substrates. Co particles of 4.5 nm diameter with fcc structure were built using a Wulff construction and subsequently deposited with their (111) or (100) facets on (100) oriented Cu substrates with a kinetic energy of 10meV/atom at temperatures of 10 K or 300 K. After the deposition, the lattice parameter of the Cu substrate has been increased continuously. It is found that significant strain in the Co particles can only be obtained in the case of (100) facets on (100) surfaces at low temperatures.

Molecular dynamics simulation has been performed to investigate the structural properties of superionic phase for (Ag_xCu_x-1)Br of x<0.5, which contains two kinds of cations, Ag⁺ and Cu⁺. Ag⁺ and Cu⁺ ions show different distribution in superionic phase. Concentration dependence also can be observed in the distribution of cations and their pair distribution functions.

The catalytic potency and the existence of irreversible H-sorption induced by the addition of various 3d transition elements and noble metals in Ni₆₇Zr₃₃ glassy alloy are investigated. The cyclic H-absorption and desorption are monitored by in situ resistance measurements. While the periods of H-absorption and desorption are significantly shortened in the case of Pd and Cr addition, this effect is not detectable in the case Pt or Cu alloying. The resulting resistance increase due to H-absorption is highly composition specific, and no reasonable explanation was found for the correlation between the magnitude of resistance change and the chemical properties of alloying element. Opposite to the variety of catalytic effects, the irreversible H-trapping can be detected in each alloy by the resistance measurements, which indicates the dominant role of Zr host metal in this phenomenon.

In this contribution, the influence of hydrogen absorption and low temperature treatments (77K) on the evolution of amorphous Curie temperature shift (δT_C^am) is investigated in some of FeNi and Fe-based glasses. T_C shifts of both types of alloys are surprisingly stable at higher temperatures and behave as a structural imprint in the investigated samples. The origin of these structural imprints is analyzed on the basis of Bethe-Slater conception, supposing the existence of quenched-in phase reminiscences in glassy alloys, being inherited from the super-cooled melt.

The microstructure and the tensile properties of a spray-formed and extruded Al- 9Si-4Cu-1Fe alloy were investigated. Manganese (0.3, 1, 2 in wt%) was added to the alloy to avoid the formation of the needle-like β-AlFeSi intermetallic phases that are highly detrimental to the alloy's ductility. The deposits were extruded at 623K with a n area reduction of 5 to 1. Small faceted dispersoids surrounding the equiaxial α-Al matrix, mainly in the form of silicon particles, were identified by SEM-EDS, as well as the Mn-containing α-Al15(Fe,Mn)3Si2 phase. The presence of the needle-like β-Al(Fe,Mn)Si was scanty, even with the lowest Mn content. The room temperature tensile tests of all the extruded alloys showed a significant increase in elongation to fracture when compared with the values observed fo r the as-spray formed deposits.This result can be ascribed to the elimination of porosity promoted by the extrusion process and to the smaller grain size of the extruded samples.

PUBLISHER'S NOTE

This article by Benetti et al was published in error, it was a duplicate of article 012114 which appears later in this volume, the duplicate PDF and references have been deleted. The missing article by S Jayalakshmi, E Fleury and D J Sordelet, which forms part of the section HYDROGEN IN METASTABLE ALLOYS, now appears at the end of the volume (012120).

We describe in the present work the production of bulk Mg hydrides by hydrogenation treatment of samples processed by severe plastic deformation. The compact bulk samples of Mg-Fe have been obtained by high pressure torsion. The ternary complex Mg₂FeH₆ and the binary MgH₂hydrides have been synthesized by hydrogenation treatment at 350°C, at 3 MPa during 24 h. The average grain refinement after HPT was modest as estimated by XRD. A comparison between the XRD patterns of the powders and of the HPT samples showed the formation, as expected, of a preferred orientation in the latter. The XRD of the hydride HPT samples (H-HPT) showed the presence of Mg, Fe, MgH₂ and Mg₂FeH₆. The first de-hydrating reaction of the alloys (after H-HPT) was studied by differential scanning calorimetry (DSC). These results showed a reduction in the hydrogen dessorption temperature in comparison with commercial MgH₂, indicating thermodynamic destabilization of the hydrides as a result of the high density of dislocations in the H-HPT samples.

The addition of Al to Mg has been indicated as a suitable way to destabilise the hydride phase, in order to bring the absorption and desorption reactions close to reasonable temperatures and pressure values for hydrogen storage. Rapid solidification is known to refine the microstructure of Mg-Al alloys and it might improve the H₂ absorption/desorption kinetics. In this paper, the interaction of H₂ with rapidly solidified Mg-Al alloys have been studied for three different composition: Mg_38.5Al_61.5, Mg₆₉Al₃₁ and Mg₇₂Al₂₈. For Mg₇₂Al₂₈, no significant changes in the microstructure have been obtained by rapid solidification. In Mg₆₉Al₃₁, a significant grain refinement has been observed, whereas, for Mg_38.5Al_61.5, the formation of a metastable hexagonal phase has been found. In all cases, a disproportionation reaction has been observed after H₂ absorption, leading to MgH₂. After heating up to 430 °C the hydrogenated samples, a main desorption reaction from MgH₂ has been observed, which brings again to the starting phases. Experimental results have been discussed on the basis of a thermodynamic assessment of the Mg-Al-H system.

Glass formation by mechanical milling was achieved in a multicomponent Ni-based alloy system. It was found that the milling time required for forming a fully glassy phase decreased with the increase in Zr content. The enhanced atomic size mismatch of constituents was responsible for the increase of glass forming ability of these alloys. The transformation from crystalline to glassy phase might be due to the destabilization of crystalline phase, induced by a combination of factors involving refinement of grain size, high pressure exerted to powders during repeated collision, and elastic mismatch energy.

Blended elemental Cr-B and Mo-B powders in atomic ratio of 67:33, 50:50, and 20:80 were subjected to mechanical alloying up to 60 h and subsequent heat treatment to investigate effect of composition and heat treatment on the phase formation of Cr-B and Mo-B powders. It was studied by X-ray diffraction and differential thermal analysis. Mechanical alloying these powder mixtures for 60 h leads essentially to a amorphous structure except for the Mo₂₀B₈₀ powder, which creates a partially amorphous MoB₄ structure. Annealing at lower temperatures relieves the strains cumulative in the milled powders and creates no new phase. The structures obtained after annealing the milled powders at higher temperature vary and depend on the overall composition of the powder mixtures. Annealing the milled Mo-B powders having greater Mo content ends up with a dissociation reaction at higher temperature.

Nanostructured Al-Mg powders with 10 to 90 at.% Mg have been produced by mechanical alloying (MA) of elemental powder mixtures and mechanical milling (MM) of prealloyed ingots. Although the solid-state transformations induced by MA and MM occur by different mechanisms due to the different starting materials used, the present results indicate that MA and MM of Al-Mg powders with the same composition lead to the formation of the same phase(s). Solid solubility extension far beyond the room temperature equilibrium value (~1 at.% Mg) was achieved by both MA and MM in the range 10 – 40 at.% Mg. The milled powders with compositions between 50 and 70 at.% Mg display the formation of single-phase γ-Al₁₂Mg₁₇, revealing that solid-state processing suppresses the formation of β-Al₃Mg₂ and hcp Mg in this composition range. No formation of β-Al₃Mg₂ was observed during milling for the entire composition range studied. Finally, in the range 80 – 90 at.% Mg, MA as well as MM lead to the formation of two-phase nanostructured powders containing γ-Al₁₂Mg₁₇ and hcp Mg.

This study examined the behavior of amorphous Mg-Cu-Ti based alloys synthesized by mechanical alloying technique. The microstructural evolution during mechanical alloying of the mixed powders was investigated by both X-ray diffraction and scanning electron microscopy. The phase stabilities of the as-milled powders were analyzed by the differential scanning calorimetry. Differential thermal analysis on the 12-h milled ternary Mg-Cu-Ti powders reveals endothermic peaks in the Mg₄₀Cu₄₀Ti₂₀ and Mg₄₀Cu₃₅Ti₂₅ at around 550 K and no such a peak is observed in the another ternary compositions. For the ternary and quaternary Mg-Cu-Ti based alloys, several amorphous powders were found to exhibit a wide supercooled liquid region before crystallization. The temperature interval of the supercooled liquid region defined by the difference between Tg and Tx, i.e. Tx-Tg, is 54K for Mg₄₀Cu₄₀Ti₂₀, 53K for Mg₄₀Cu₃₅Ti₂₅, 51K for Mg₄₀Cu₃₅Ti₂₃B₂, 62 K for Mg₄₀Cu₃₅Ti₂₁Sn₄, and 74 K for Mg₄₀Cu₃₅Ti₂₁Ni₅. As the results demonstrated, the small addition of Sn and Ni significantly improved the glass forming ability of the Mg-Cu-Ti based amorphous alloys.

Investigation of the phase formation during mechanical alloying (MA) was systematically performed in the Ti-O system. Powder mixtures of Ti and TiO₂ with various compositions and single-phase Ti₂O, α-TiO and α-Ti₂O₃ powders were respectively subjected to planetary ball milling. According to X-ray diffractometry, high-temperature phases such as α-Ti solid solution, β-TiO and γ-Ti2O3 were observed for Ti-33 at%O (after 4 h of MA), 40–55 at%O (8 h) and 60 at%O (4 h), respectively. The metastable phase formations are discussed from various viewpoints including local pressure, local temperature, point defects, impurity and repeated deformation. The phase formations by MA are explained by primitive unit cell volume of the crystal structure as an indicator.

High-pressure reactive milling under hydrogen atmosphere is used for the one-step synthesis of doped sodium alanate. In-situ monitoring of the pressure and the temperature inside the vial gives a direct feedback about the reactions occurring during the milling. This information is used to study the influence of the dopant during synthesis, e.g. the amount of dopant added. The study of the pressure variations during milling is a reliable tool for screening the efficiency of different dopants.

Two applied samples preparation techniques (rapid quenching from the melt and mechanical alloying) resulted in the formation of fully amorphous Cu₄₇Ti₃₄Zr₁₁Ni₈ and Cu₄₇Ti₃₄Sn₁₁Ni₈ alloys. However, a significant differences in thermal stability and crystallization behaviour have been found, depending not only on the alloy composition, but on the fabrication method as well. MA powders of both alloys studied revealed one dominating DSC exothermic effect. Zr-containing ribbon showed four exothermic effects, while Sncontaining one – only two overlapping peaks. In the case of ribbons it was found that replacing Zr by Sn did not influenced the crystallization temperature or supercooled liquid region, however, the activation energy of crystallization increased significantly, from 190 to 223 kJmol^-1. Opposite behaviour was observed for MA powders. Introducing Sn into the alloy instead of Zr resulted in a considerably increase of the crystallization temperature (from 783 to 826 K), simultaneously the activation energy for crystallization remained the same.

Al₆₇Cu₂₀Cr₁₃ and Al₇₅Cu₁₀Cr₁₅ alloys were produced by mechanical alloying from elemental powders. As-milled samples consist of the initial elemental phases. Phase transformations at heating were analyzed by differential scanning calorimetry and X-ray diffraction analysis. Annealing of as-milled powders in the temperature range of 500 to 550 °C results in the formation of binary and ternary compounds including the decagonal quasicrystalline phase that was found to be stable at least up to 800 °C.

We focus on the synthetic path of nanostructured Ni-Sn and Co-Sn systems by mechanical alloying. A similar reaction path seems to characterize the process for both the systems: the formation of intermediate, metastable, Sn rich phases has been evidenced, not provided for by the corresponding equilibrium phase diagrams. Their crystallographic and thermodynamic properties were evaluated through a structural and calorimetric investigation. Further mechanical processing induced structural evolutions by the progressive alloys enrichment in Ni and Co respectively, according to the stoichiometric constraints. Quantitative assessment of relative abundance of crystallographic phases let us investigate the alloying kinetics. By resorting to a previously developed procedure we evaluated collision frequency and impact energy. Then the analytical solution of the kinetic curves allowed us to relate the conversion degree to the effective collisions undergone by each powder particle.

Nanocrystalline Fe with carbon concentrations of 0.2 wt.% and 0.4 wt.% was prepared by the mechanical alloying technique. The grain size after milling for 100 h was 22 and 17 nm for 0.2 and 0.4 wt.% C, which shows the carbon addition is beneficial in getting smaller nano-crystalline grain size. Consolidation into bulk shape with a relative density above 98% was performed with the spark plasma sintering technique at 650, 675, 700 and 730 °C. A maximum compression strength of approximately 2000 MPa was obtained for 650 °C consolidation sample with an absolute lack of plasticity, whereas a strength to plasticity balance could be obtained by increasing the temperature. Detailed microstructural analysis has been done with scanning electron microscopy and transmission electron microscopy. The microstructure shows a bimodal grain size distribution with a fine dispersion of oxide particles having a size ranging from 20 to 200 nm and cementite particles having a size range from 100 to 500 nm depending on the sintering temperature. The presence of oxide particles along with bimodal grain distribution resulted in a high yield strength value of 1620 MPa and high plasticity of 45%.

Fe /Fe₃O₄ (magnetite) powders obtained by ball milling at room temperature, undergo an incomplete redox reaction with formation of FeO. This reaction is favoured due to the high energy developed during the milling and alloying. Concurrent effects of the milling, such as grain refinement down to the nanometric scale lead at the end of the milling processes to a mixed multiphased nanopowder, with a homogeneous dispersion of Fe and Fe oxide grains. Such ferromagnetic – antiferromagnetic systems are extensively studied due to their exchange bias properties, extremely useful in technological applications. We study the phase transformation that leads to a multiphased metal / oxide microstructure with an energydispersive in-situ X-ray diffraction experiment using the synchrotron radiation. This study allows direct collection of X-ray spectra after few minutes exposure, at selected temperatures, ranging between 20°C and 1000°C. Magnetic behavior has been studied for as-milled and annealed samples and the obtained magnetic parameters are correlated to the microstructure and phase composition at each stage of annealing. A significant exchange bias effect, related to FeO content, is observed for as-milled sample, the effect being less pronounced upon annealing the nanogranular powder.

High energy mechanical milling (HEMM) of a mixture of Cu powder and Al₂O₃ nanopowder has been used to produce Cu-(2.5-10)vol.%Al₂O₃ nanocomposite powders with a ultrafine grained or nanocrystalline Cu matrix. The microstructure and microhardness of the as-milled powder particles and the thermal stability and microhardness change of the nanocomposite powder particles caused by annealing at temperatures up to 500^oC have been studied. It is shown that HEMM can be effectively used to disperse (2.5-10)vol.% Al₂O₃ nanoparticles into a ultrafine grained or nanocrystalline Cu matrix. Using larger diameter balls or increasing the volume fraction of Al₂O₃ nanoparticles to 7.5% or higher allows synthesis of Cu-Al₂O₃ nanocomposite powders with nanocrystalline Cu matrix. Refining the microstructure of the Cu matrix and increasing the volume fraction of Al₂O₃ nanoparticles in the nanocomposite both increase the thermal stability of the nanocomposite structure.

The static mechanical properties of a Ca₄₈Mg₂₇Cu₂₅ bulk metallic glass were investigated using a technique of ultrasonic measurement and compressive test. The Young's modulus (E), Poisson's ratio (v), shear modulus (G) and bulk modulus (B) for the Ca₄₈Mg₂₇Cu₂₅ alloy at room temperature are significantly smaller than those for Zr- and Pd- based bulk metallic glasses. The values of E, v, G and B for the Ca₄₈Mg₂₇Cu₂₅ alloy are 29.8GPa, 0.230, 12.1GPa and 18.4GPa, respectively. The results of compression test for the Ca₄₈Mg₂₇Cu₂₅ alloy have been also described.

For thick-section components such as headers and pipes of the power plants, high creep rupture strength and oxidation resistance are required. It is known that the addition of boron can improve the creep strength and oxidation resistance through the stabilization of M₂₃C₆ carbides in the vicinity of prior austenite grain boundaries. In this study, the effect of boron addition with the range of 0.0033~0.0133 wt% on the creep behavior of 9Cr-1.5Mo steel was investigated. Small punch creep tests were carried out to investigate the effect of boron addition on creep properties. Microstructure observation was performed to analyze the effect of boron addition on creep strength and rupture life. Also, the relationship between the minimum creep rate and the amount of boron addition were analyzed. The addition of boron is beneficial in lowering the steady-state creep rate.

A water quenching method is used to produce as-cast Zr₄₈Cu₃₆Al₈Ag₈ rods with diameters from 20 mm to 25 mm. The microstructures of the as-cast samples were investigated by X-ray diffraction, optical microscopy and scanning electron microscopy. Furthermore, the crystallization behavior of the Zr₄₈Cu₃₆Al₈Ag₈ glassy alloy was examined by XRD and transmission electron microscopy. Based on the results obtained one can assume that the simultaneous precipitation of the Zr₂Cu+AlCu₂Zr eutectic phases is the possible reason for the high stabilization of the quaternary Zr₄₈Cu₃₆Al₈Ag₈ supercooled liquid.

Several preparation methods are available for the production of amorphous alloys. During the experiment described in this paper (Cu₅₈Zr₄₂)100-xAl_x (x = 0-14,8; in at%) amorphous alloys were prepared by casting and ball-milling. The ingots were produced by arc melting. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mould. The microstructures of these samples were defined by SEM. The amorphous samples were analysed by DSC and the activation energy of the crystallization processes was calculated from the measured temperatures. The master alloys of identical composition were milled by ball-mill for different periods of time. The powders were analysed by XRD in order to define the amorphous fractions.

The thermal stability, crystallization behaviour and glass forming ability of Cu-Zr-Ag system have been investigated on the basis of a ternary phase diagram. We altered the concentration of the alloys from the Cu₅₈Zr₄₂ to the concentration of the deep eutectic point of the Cu-Zr-Ag ternary system and we calculated the glass forming ability parameters. This paper summerises the results of the procedure during which Cu-Zr-Ag amorphous alloys with different Ag content (0-25%) were prepared by casting and ball-milling. Wedge-shaped samples were prepared from the ingots by centrifugal casting into copper mold. The supercooled liquid region (ΔT_x) exceeded 75K. Following the characterization of the cast alloys, master alloys of identical composition were milled in a Fritsch Pulverisette 2 ball-mill. The powders, milled for various periods of time were analysed by XRD in order to define the amorphous fraction.

The present work investigated effects of Nb (1-5 at.%) on CuZrAlAg bulk metallic glasses. The addition of Nb did not change the amorphous structure but affected the thermal behaviors significantly. The corrosion resistances of the BMGs with addition of 5 at% Nb in 0.5 N H₂SO₄ solutions was the best among the samples. Pin-on-disk measurements showed that the hardest sample, viz. the one with 3 at% Nb exhibited the best wear resistance. Mechanical properties were also investigated using a nanoindentation technique. It was found that the addition of Nb may improved corrosion resistance and wear resistance of the Cu-based BMG, but not in a simple and systematic manner.

In the last years new type Cu-Hf-Al ternary alloys were developed with high glass forming ability and ductility. The addition of Al to Cu-Hf alloys results in improvements in glass formation, thermal stability and mechanical properties of these alloys. We have investigated new Cu-based bulk amorphous alloys in Cu-Hf-Al ternary system. The alloys with Cu₄₉Hf₄₂Al₉, Cu₄₆Hf₄₅Al₉, Cu₅₀Hf_42.5Al_7.5 and Cu₅₀Hf₄₅Al₅ compositions were prepared by arc melting. The samples were made by centrifugal casting and were investigated by X-ray diffraction method. Thermodynamic properties were examined by differential scanning calorimetry and the structure of the crystallising phases by scanning electron microscopy. The determination of liquidus temperatures of alloys were measured by differential thermal analysis.

The relationship between metallic glass properties and the cooling behavior of Zr₆₅Cu_27.5Al_7.5, Zr₅₈Cu₃₃Al₉ and Zr₅₀Cu_39.3Al_10.7 alloys was investigated using an electromagnetic levitation heater combined with a spin coater style quenching system. The quenching process was monitored by the high-speed camera and the thermospot sensors. About forty millimeters amorphous disks were obtained. The maximum temperatures and the maximum cooling rates at the center of the disk were 500°C and 30% higher than the values at the 15mm outer from the center position. Cooling process affected the glass-forming abilities. The temperature differences between the glass transition and crystallization onset temperatures (ΔTx) of the center position were 10 to 20% higher than those in the outer.

The casting in complex shapes (tubullar) and the main magnetic properties of bulk metallic glasses (BMG) alloys from the ferromagnetic Fe-Cr-Ni-Ga-P-Si-C system, with a small adittion of Ni (3%) were studied. Samples as rods and sockets having the thickness up to 1 mm were obtained from master alloys by melt injection by low cooling rates into a Cu mold and annealed in order to ensure adequate magnetic requirements. The structure was examined by X-ray diffraction (XRD) and the basic magnetic properties (coercivity, magnetic remanence, initial susceptibility, etc.) were determined by conventional low frequency induction method. The experimental investigations on producing of BMG ferromagnetic alloys with 3% Ni show the possibility to obtain magnetic shields of complex shape with satisfactory magnetic properties. The presence of Ni does not affect the glass forming ability, but reduce the shielding capacity.

The results of the investigations of alloys of compositions Ni₅₈Nb_x(ZrTi)_39-xAl_y and Ni₅₈Nb_x(ZrTi)_32-yAl_y with x = 10, 25 and y = 3, 7 respectively, are presented. The structure of the all melt spun ribbons was amorphous, however the crystallization process proceeded in a very different way in the ribbons with x = 10, y = 7 and ribbons with x = 25 and y = 3. In the first compositions typical primary crystallization of the 50 nm grains of the NiTi(Zr) cubic phase was observed while the ribbons containing 25 at.% of Nb and 3 at.% of Al revealed very stable thermally amorphous phase, nano-crystallizing at the range of primary crystallization but preserving large fraction of the amorphous phase high above the primary crystallization temperature. The tensile curves were determined for ribbons of both compositions and were different, but revealed quite large range of the plastic elongation. The HREM experiments did not reveal any crystallization in the shear bands, after the fracture of the ribbons.

In this work the effect of 1 % at additions of Ti or In on structural and thermal properties of the Au₄₉Ag_5.5Pd_2.3Cu_26.9Si_16.3 [1] alloy is presented. Formation of a glassy phase was confirmed using X-ray diffraction for rods up to 3 mm in diameter. Data on glass transition, T_g, and crystallization, T_x, temperatures as well as on colour and Vickers microhardness are reported.

Thermal stability, structure, and magnetic properties of bulk type Ci_88.3Al₂Ga₁P_4.35B_4.35 alloy in ribbon form have been studied using differential thermal analysis, x-ray diffraction and magnetic measurements. Results reveal that crystallization peak temperature (T_x) and Curie temperature (T_c) of the as-cast alloy are respectively 513 and 370 °C. Crystallization of the specimen starts after annealing at 460 °C and α-Fe is precipitated out. Annealing at temperatures higher than 515 °C, produces apart from α-Fe, hard magnetic precipitants (Fe₂B, Fe₃B), which deteriorate the soft magnetic properties. Lowest coercive field – 9.8 A/m, highest saturation of induction – 1.55 Tesla and best losses – 0.42 W/kg (at 50 Hz and 0.4 kA/m) were obtained for as-cast specimen. Observed good soft magnetic properties of these low cost cast-iron based alloys suggest perspective applications of these soft magnetic alloys as an alternative to the conventional Fe-Si electrical steel and Mn-Zn ferrites.

A Zr-based bulk metallic glass of Zr70Ni20Al10 has an excellent glass-forming ability (GFA), and can form a massive bulk glass by simple water-quenching. In order to clarify the role of electronic structure in this excellent GFA of Zr70Ni20Al10 glass by comparing to the Zr70Ni30 reference glass, having a worse GFA, valence-band photoemission spectra were measured with changing the incident photon energy using synchrotron radiation at BL7 of HiSOR. We have also measured Ni 3p, Zr 3d and Zr 4p core-level photoemission spectra of the Zr70Ni20Al10 glass, and compared them to those of the Zr70Ni30 reference glass. The shifts of the binding energies in every core-level are observed, indicating changes of the chemical nature by replacing the Ni atoms with Al atoms.

{[(Fe_0.5Co_0.5)_0.75Si_0.05B_0.20]_0.96Nb_0.04}_100-xCu_x (x = 0, 1, 1.5 and 2) alloys with different rapid solidification conditions were prepared by copper mold casting and melt spinning. The structures, the thermal and the magnetic properties were studied by X-ray diffraction, differential scanning calorimetry and vibrating sample magnetometry, respectively. Minor Cu addition obviously depresses the glass-forming ability of the alloys (critical glassy diameter d_c < 1 mm) compared with [(Fe_0.5Co_0.5)_0.75Si_0.05B_0.20]₉₆ Nb⁴ (d_c = 3 mm). The effect of Cu addition on the evolution of crystalline phases corresponding to different rapid solidification conditions was evaluated. The existence of (Fe,Co), (Fe,Co)₃B, (Fe,Co)₂B and (Fe,Co)₂₃B₆ crystalline phases in {[(Fe_0.5Co_0.5)_0.75Si_0.05B_0.20]_0.96 Nb_0.04}_100-x Cu_x alloys influences the saturation magnetization compared with the corresponding glassy alloys.

In order to produce centimetre-sized bulk glassy alloys (BMGs), various cast techniques have been developed. We succeed in the development of cap casting and enveloped casting technique to accomplish the fabrication of centimetre sized BMGs. The former has an advantage to increase cooling rate and the later has an advantage to joint another materials instead of welding. This paper presents the production of a glassy Zr₅₅Cu₃₀Ni₅Al₁₀ alloy rod with a diameter of 32 mm and joined glassy Zr₅₅Cu₃₀Ni₅Al₁₀ alloy parts with another materials for industrial applications.

We examined the solidification morphology and structure of arc-melted Zr₅₀Cu₄₀Al₁₀ glass-forming alloys. Since the crystal growth rate is much lower than the velocity of isothermal plane of glass transition temperature (T_g), arc-melted Zr₅₀Cu₄₀Al₁₀ alloy sometimes reveals glassy phase at finally solidified region (top-side) after crystal growth (bottom side). Vitrification in front of the crystalline solidification interface of arc-melted Zr₅₀Cu₄₀Al₁₀ alloy Zr can be seen when the crystal phase is an Al-supersaturated B2-type ZrCu phase.

Molecular dynamics simulations based on plastic crystal model were performed for the Fe_69.0Nb_10.3B_20.7 and Zr_57.1Ni_28.6Al_14.3 alloys to investigate their forming ability and features of the noncrystalline structures. The Fe_69.0Nb_10.3B_20.7 and Zr_57.1Ni_28.6Al_14.3 alloys were created from C₆Cr₂₃ and Ti₄Ni₂O structures, respectively, by assuming the presence of hypothetical clusters in the crystalline structures under a treatment that the clusters and glue atoms are regarded as the components. The analysis with total pair-distribution function, g(r), revealed that these alloys have high tendencies to form noncrystalline structures while their partial g(r) profiles for pairs among components showed the presence of medium range order. Cluster packed structures from bcc derivative compounds cause high forming ability of noncrystalline structure and the medium range order in the noncrystalline structure.

The phase components and microstructure of as-cast Ti_41.5Cu_37.5Ni_7.5Zr_2.5Sn₅Hf₅Si₁ glass forming alloy was investigated by differential scanning calorimetry (DSC), scanning electron microscopy and in-situ neutron diffraction studies. For diameters above 3 mm the samples present small crystals identified as the Ti₅Sn₃Cu and cubic Ti(CuNi) phases. Crystallization studies in the DSC furnace and in-situ neutron diffraction reveal that the cubic titanium phase is TiNi(Cu) with the Pm-3m space group and not the β-Ti phase. The evolution of phases above T_γ show that the TiNi phase is metastable and decomposes at Tx=727 K to form the γ-TiCu phase. The Ti₅Sn₃Cu phase does not evolve in this temperature range. At room temperature by compression measurements, the alloy with 2 mm diameter shows a high failure limit of 2120 MPa with 2,1% of plasticity.

We summarize the structural features of several Cu-based alloys known so far having high glass-forming ability and investigate the influence of Ag addition on their crystallization behavior. According to synchrotron-beam X-ray radiation studies, an oC68 Cu₁₀Zr₇ phase is found to be a good approximant to the Cu-Zr-Ti and Cu-Zr-Ag glassy phases. The structure of the bulk glassy Cu₃₆Zr₄₈Al₈Ag₈ and Cu₄₄Ag₁₅Zr₃₆Ti₅ alloy samples studied by high-resolution TEM was found to contain well developed medium-range order zones and nanoparticles, respectively. An influence of the cooling rate on the structure and properties of the Cu-based glassy alloys on heating was also studied. The crystallization kinetics of Cu₅₅Zr₄₅, Cu₅₀Zr₅₀, Cu_55-xZr₄₅Ag_x (x = 0, 10, 20), Cu₄₄Ag₁₅Zr₃₆Ti₅, Cu₄₅Zr₄₅Al₅Ag₅ and Cu₃₆Zr₄₈Al₈Ag₈ glassy alloys was also analyzed substantially. Cu₃₅Zr₄₅Ag₂₀ alloy was found to exhibit possible phase separation upon heating within a supercooled liquid region.

Bulk metallic glass formations have been explored in Fe-B-Si-Nb alloy system using the so-called atomic cluster line approach in combination with minor alloying guideline. The atomic cluster line refers to a straight line linking binary cluster to the third element in a ternary system. The basic ternary compositions in Fe-B-Si system are determined by the inetersection points of two cluster lines, namely Fe-B cluster to Si and Fe-Si cluster to B, and then further alloyed with 3-5 at. % Nb for enhancing glass forming abilities. BMG rods with a diameter of 3 mm are formed under the case of minor Nb alloying the basic intersecting compositions of Fe₈B₃-Si with Fe₁₂Si-B and Fe₈B₂-Si with Fe₉Si-B. The BMGs also exhibit high Vickers hardness (H_v) of 1130-1164 and high Young's modulous (E) of 170-180 GPa

Microwave (MW) processing is emerging as an innovative and highly effective material processing method offering many advantages over conventional methods especially for sintering application. In the present study, using a mixed powder of the Ni₅₅Nb₂₅Ti₁₅Pt₅metallic glassy powder prepared by an argon gas atomization process blended with 50 vol.% Sn powder, the MW-induced heating and sintering were carried out by a single-mode 2.45 GHz MW applicator in a magnetic field maximum. The structure and thermal stability of the sintered glassy composite specimens were investigated. The addition of Sn particles enhanced densification of the sintered Ni-based metallic glassy alloy powders.

The kinetics of volume relaxation for Pd₄₆Cu_35.5P_18.5 and Pt₆₀Ni₁₅P₂₅ BMGs were investigated by high-resolution density experiments at room temperature. The distinct two- steps relaxation behavior was observed for as-quenched BMGs. After pre-annealing as- quenched Pd₄₆Cu_35.5P_18.5 BMG in the supercooled liquid region, the relaxation process changed into a single relaxation process well described by a stretched exponential relaxation function. Meanwhile, the pre-annealed Pt₆₀Ni₁₅P₂₅ BMG still remained a two-steps relaxation behavior. The volume relaxation data of as-quenched Pt₆₀Ni₁₅P₂₅ BMG was analyzed on the base of the structural inhomogeneity composed of volume compression and expansion regions in the like sites during structural relaxation.

Bulk Metallic Glass (BMG) alloy with the composition of Zr₅₅Cu₃₀Al₁₀Ni₅ was deposited by sputtering as thin films on several different engineering polymers and polymer composites. Polycarbonate, polymethyl methacrylate, polyamide 12, polyarylamide (50GF=50 % glass fibers), polyphenylene sulfide (30GF) and polybutylene terephthalate (30GF) were used as substrates. The microstructure of the deposited BMG coatings was studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results of XRD and SEM studies were consistent with amorphous microstructure. Elemental compositions of the coatings were verified by energy dispersive spectroscopy (EDS). Mechanical properties of the coatings were compared to copper mould cast BMG using nano- indentation tests with similar results. According to the cross-cut tape tests good adhesion was achieved between the studied BMG alloy and all other polymer substrates except polycarbonate. Nano-indentation results showed similar mechanical properties for coating and cast BMG. The results of this study look promising as they open new opportunities for BMG- polymer composite applications.

Bulk metallic glass (BMG) with high corrosion resistance and high oxidation resistance was synthesized in the Ni-Nb-Sb system with the diameter of 3mm. The glass transition temperature (T_g), the reduced glass transition temperature (T_rg=T_g/T_l) and supercooled liquid span (ΔT_x) are 873K, 0.59 and 54K, respectively. These thermal data indicate that this kind of Ni-based glass can maintain its stable amorphous state and resist crystallization in a rather wide temperature region. Electrochemical measurements indicate that it shows high corrosion resistance in aggressive hydrochloric acid solution with 1N and 6N concentration, respectively, at room temperature. Surface forms stable passive film and presents low current density. The oxidation kinetics follows a parabolic rate law at 853K. The x-ray diffraction pattern showed that the oxide layer is composed of Nb₂O₅, Ni₃Nb and metallic Ni. The oxide surface morphologies showed that a layer of compact oxide film formed, which shows no obvious grain boundary.

The present work reported the application of electropulsing technique (EPT) for improving plasticity of a Zr₆₂Al₁₉Ni₁₉ bulk metallic glass. After the elecropulsing with a small current of 5A, no obvious crystallization was observed in X-ray diffraction (XRD) patterns. Results of differential scanning calorimetry (DSC) measurements indicated that the glass transition temperature was reduced from 698K to 691K. Room-temperature uniaxial compression tests revealed that the treated BMG showed larger plastic deformation up to 6%, compared with less than 2% plasticity of untreated sample, at a 1×10^-4 s^-1 strain rate. SEM observation showed that the sample after electropulsing treatment show significant difference in the distribution of shear bands from that of the untreated one.

Cu-Hf-Ti amorphous alloys are high strength and wear resistant materials. Master alloys of Cu_57.5Hf_27.5Ti₁₅ and Cu_57.5Hf₂₅Ti_17.5 ternary alloys have been prepared by arc melting, and wedge and rod shaped samples have been cast by centrifugal casting. Liquidus and solidus temperatures of the alloys were determined by DTA. The fully amorphous size was determined by X-ray diffraction. Thermodynamic properties of the amorphous alloys were studied by DSC measurements and Kissinger analyses were performed.

In order to study local structure in Pd_42.5Ni_7.5Cu₃₀P₂₀ excellent bulk metallic glass-former, an anomalous x-ray scattering (AXS) experiment was performed at energies close to the Pd, Ni and Cu K absorption edges together with the reference Pd₄₀Ni₄₀P₂₀ and Pd₄₀Cu₄₀P₂₀ glasses at the beamline BM02 of the ESRF. The differential structure factors, Δ_iS(Q), were obtained with a good statistical quality. A small shoulder observed at about 19 nm^-1 in S(Q) becomes prominent in Δ_PdS(Q), indicating a Pd-Pd atomic correlation of 0.32 nm. This pre-shoulder was not observed in Pd₄₀Ni₄₀P₂₀ bulk glass having a slightly worse critical-cooling-rate, but in Pd₄₀Cu₄₀P₂₀ glass ribbon available by only ultrafast quenching. It is suggested that covalently bonded Pd-P-Pd connection with an almost right bond angle would be formed by replacing the Ni with the Cu atoms. From the obtaining differential pair distribution function around the Pd K edge, Δ_Pdg(r), the first peak position in Pd_42.5Ni_7.5Cu₃₀P₂₀ shows a longest atomic distance among the glasses and the width of the first peak is slightly narrower than that in Pd₄₀Cu₄₀P₂₀. Thus, a more uniform atomic arrangement around Pd atoms with a loose packing, i.e., a longer and uniform Pd sublattice, is expected for Pd_42.5Ni_7.5Cu₃₀P₂₀ compared to the other two reference glasses.

A levitation method using the alternating and the static magnetic fields suppresses convection in a levitated melt and consequently enables us to measure crystal growth velocity as low as 0.5 mm/s in the undercooled melt. Crystal growth velocities of the constituent phases in the bulk-glass-forming Zr-Ni-Al and Zr-Cu-Al alloys were measured. The growth velocities at the bulk-glass-forming compositions in the Zr-Ni-Al and the Zr-Cu-Al alloys were as low as 1mm/s even if the undercooling exceeded 100K. The interface kinetics and the solute transport of rejected elements resulted in the low growth velocities. The BMG formation in the metal mould casting can be explained by considering the competition between the crystal growth and the glass transition.

Mg₆₀Cu₃₀Gd₁₀ and Mg₆₀Cu₃₀Gd_1.5Nd_8.5 ribbons were obtained by melt spinning. For both compositions, a fully amorphous phase was found and a clear Tg was observed. In-situ XRD measurements were carried out during heating of ribbons at the ID11 synchrotron beamline of ESRF, Grenoble (France). In order to identify the crystallisation products, an annealed Mg₆₀Cu₃₀Gd₁₀ master alloy was analysed by SEM/EDS and XRD. The existence of new ternary compounds (MgCu₄Gd and Mg₂CuGd) in the Mg-Cu-Gd system is suggested.

The most notable property of bulk metallic glasses is their ultrahigh (near theoretical) strength and hardness. Because many of known BMGs miss tensile plasticity and thus exhibit catastrophic failure upon tension it is of great importance to understand deformation mechanisms involved and thus improve their performance. Time-resolved in-situ x-ray diffraction experiments may nowadays be performed at high-brilliance synchrotron radiation sources for a variety of conditions. An example is provided, concerning mapping of the strain distribution in tensile stressed Zr-based BMG by in-situ hard x-ray diffraction.

The bulk amorphous ferromagnets Nd₆₀Fe₃₀Al₁₀ and Nd₆₀Fe₂₀Co₁₀Al₁₀ exhibit hard magnetic properties, and time dependent magnetisation measurements have been performed to explore similarities and differences between them. Magnetic viscosity measurements on the major hysteresis loop of Nd₆₀Fe₃₀Al₁₀ are reported, along with data for both alloys showing the behaviour of the irreversible magnetic susceptibility. The fluctuation field, H_f, for each alloy is determined. A focus of the study is investigation of the anomalous magnetic viscosity i.e. non-monotonic behaviour of the time dependent magnetisation (where a peak is observed in the magnetisation), on the recoil curve that leads to the dc demagnetised state. Data showing non-monotonic behaviour in both Nd₆₀Fe₃₀Al₁₀ and Nd₆₀Fe₂₀Co₁₀Al₁₀ is presented. The non-monotonic behaviour is interpreted using the Preisach model, as it predicts a simple functional relationship between the time taken to reach a peak and the applied magnetic field. The experimental data is in good agreement with this simple relationship.

Hard magnetic thick ribbon samples of a series of Pr_9-xDy_xFe₆₀Co₁₃Zr_1+yTi_3-yB₁₄ alloys (where x=0;1 and y=0;1) (having average thicknesses t_r of~ 140 µm) were produced directly by the melt-spinning technique under an Ar atmosphere. The phase constitution of the samples in the as-cast state was determined by X-ray diffractomety and Mössbauer spectroscopy. Hysteresis loops measurements at room temperature indicated very good hard magnetic properties for the alloys, which the coercivity attaining a maximum values of 1.58 MA/m. This is comparable with the coercivities of commercial NdFeB magnets based on melt spun ribbon and with those for nanocrystalline Nd-Fe-B magnets produces by other processes such as mechanical alloying or HDDR.

The soft magnetic Fe₇₃Si₁₆B₇Nb₃Cu₁(at%) powder with nanocrytalline structure and the dielectric BaTiO₃ powders with different sizes and shapes were mixed to be cast as the absorbing sheets with polymer-based binders and solvent. Absorbing properties, such as complex permittivity and complex permeability of the powder sheets, were measured using a network analyzer and an impedance analyzer. As a result, Fe-based nanocrystalline powder sheets mixed with the nano-sized BaTiO₃showed the improved characteristics as electromagnetic wave absorbers at the high frequency of ∼10 GHz. Accordingly, it can be concluded that the characteristics of dielectric BaTi₃ particles affected the electromagnetic wave absorbing properties of Fe-based nanocrystalline P/M sheets.

This work was aimed at investigating the FeNiMoB type alloys exhibiting relatively high saturation magnetostriction after suitable heat treatment, which makes them suitable for application in force sensors. Crystallization process of amorphous alloy was examined by DSC. Temperatures and enthalpies of both stages of crystallization were determined from DSC upon continuous heating from a room temperature to 993 K with constant heating rate of 20 K/min. Next, samples were isothermally annealed under longitudinal and transverse magnetic fields within the temperature range of 623–833 K for 1 h under Ar protective atmosphere. Structure of the alloys was checked by means of XRD and TEM. After annealing, the AC (50 Hz) magnetic properties (coercivity, magnetic induction) were determined using a computerized hysteresis loop tracer. An effect of the annealing temperature, induced magnetic anisotropy and of the applied compressive stresses on the dynamic magnetic properties of the alloys was studied within a frequency range from 50 Hz to 50 kHz. Our studies confirmed that the Fe-Ni-Mo-B alloy annealed at 653 K is the most suitable for application in force sensors. Moreover, the results obtained indicate that for the measurements of compressive stresses below 0.3 MPa it is more advantageous to use the cores with longitudinal anisotropy, whereas the cores with a transverse magnetic anisotropy are more suitable for application at the compressive stresses over 0.3 MPa.

The nanocrystalline cores made from rapidly-quenched amorphous ribbons are increasingly used in power electronics, particularly in high-frequency and high-temperature applications. Under this work, the influence of ribbon thickness and of an emulsion coating applied between ribbon coils on soft magnetic properties of nanocrystalline toroidal cores made from this ribbon was investigated. The amorphous ribbons of different thickness were cast by rapid-quenching from the FeCuNbSiB and FeCoNbBP alloys and next toroidal cores were wound from them. The cores were prepared with and without the use of an emulsion insulation and subjected to thermo-magnetic treatment conducted under protective atmosphere of argon. Next, soft magnetic properties of the cores were measured within a frequency range from 50 Hz to 300 kHz. It was found that the ribbon thickness and the use of ribbon coating influence soft magnetic properties of both studied alloys.

The crystallization effect of Fe-based nanocrystalline on the electromagnetic (EM) wave absorption behavior has been investigated. Amorphous ribbons were annealed at temperatures ranging from 500°C to 650°C for 1 hour to investigate the crystallization behavior. The grain size was in the range from 10 to 20nm as the specimen was annealed under 600°C, while it significantly increased when annealed above the temperature. The initial permeability increased with volume fraction of bcc-Fe(Si) phase and showed a maximum at f_c∼0.77. The optimized magnetic properties of nanocrystalline ribbons can be acquired when they were crystallized at 550-560°C for 1 hour. However, the EM wave absorption properties in a sheet made of the nanocrystalline powder was greatest in the specimen crystallized at 510°C for 1hour annealing, indicating that the pulverization and milling process lowered the optimum crystallization condition.

The effects of Fe replacement by Ni on the formation of nanocrystalline structure and on the magnetic and mechanical properties were investigated in the series of (Fe_1-xNi_x)₈₁Nb₇B₁₂ (x=0, 0.14, 0.25, 0.33 and 0.5) alloys. The analysis of phase evolution upon primary crystallization indicates that with an increase of Ni content in the samples the nanocrystalline grains exhibit transition from BCC-phase to a mixed state with coexistence of BCC- and FCC-phase and finally the FCC-FeNi phase is formed. The value of the Curie temperature of the amorphous phase, T_C(am), increases with an addition of Ni. We show that a replacement of Fe by Ni results in an improved magnetic softness and it has a beneficial effect on the bend ductility of amorphous and nanocrystalline samples.

The phase transformation and magnetic entropy change (ΔS_M) in the Ni₅₅Mn₂₀Ga₂₅ Heusler alloy has been studied. The temperature dependence of magnetization study shows the direct transition from ferromagnetic martensitic phase to paramagnetic austenitic phase occurred at 353 K. By compositional tuning the first order martensitic transformation (T_M ∼200 K for parent compound Ni₂MnGa) and second order magnetic phase transition temperatures (T_C ∼375 K for parent compound Ni₂MnGa) can be merged. This occurs for Ni₅₅Mn₂₀Ga₂₅ alloy at 353 K. The magnetic entropy change, ΔS_M-value of -7.0 Jkg^-1K^-1 has been obtained in a field change of 1.2 T. The origin of enhancement in ΔS_M -value is attributed to the essential coincidence of T_M and T_C.

Soft magnetic metallic glasses or their corresponding nanocrystalline counterparts based on Fe and on Ni frequently exhibit different magnetic properties. This work is devoted to rapidly quenched (Fe-Ni)₈₁Nb₇B₁₂ ribbon system with the ratio of Ni/Fe being 0, 1/6, 1/3, 1/2, 1, 2 and 3 prepared by planar flow casting. Using temperature dependencies of dilatation, the Curie temperature T_C and structural transitions (glass transition, crystallization) were determined. Direct measurement of magnetostriction was employed to determine the values of saturation magnetostriction λ_S at room temperature. The values for as-quenched samples with low Ni-content (0, 1/6) clearly indicate the proximity of T_C to room temperature and thus the values of λ_S are low. The highest value of λ_S observed for Ni/Fe = 1/3 is 15.86 ppm. Increasing Ni-content leads to decrease of λ_S down to 1 ppm for Ni/Fe = 3, in accord with its negative value observed in pure Ni.

Magnetic properties of Fe-B-Nd-Nb quaternary alloys were investigated in terms of the Fe concentration and the quenching rate. High energy products reaching 98 kJ/m³ with high coercivities of 570-750 kA/m were obtained by a conventional rapid quenching technique followed by heat treatment. The nanocomposite magnets are attractive for future applications since their magnetic performance can be improved by optimization of the quenching rate and the heat treatment condition.

The effects of nozzle-wheel gap size and annealing temperature on magnetic properties of FeSiB amorphous alloy strips fabricated by the PFC method were investigated. 50mm wide amorphous alloy strips were prepared by single-roll PFC equipment with various nozzle-wheel gap sizes and annealing temperatures. The decreasing nozzle-wheel gap size improved the magnetic properties of amorphous alloy strips by decreasing the eddy current losses and the easy magnetization. In addition, magnetic properties of annealed amorphous alloy strips primarily depended on size and volume fraction of nano-sized crystallites, which were closely related to annealing temperature.

Paper presents the results of magnetoelastic investigation carried out on the ribbon ring-shaped samples made of Fe₈₁Si₄B₁₄ amorphous alloy. Samples were subjected to different thermal treatment in magnetic field to reduce value of residual stresses generated during the rapid quenching process as well as induce anisotropy. Under the influence of compressive stresses, the shape of hysteresis loop changes significantly for all investigated samples. The highest stress sensitivity was observed for sample annealed in the magnetic field perpendicular to the ribbon direction. In this case flux density B increased from 75 mT to 205 mT under compressive stress up to 10 MPa.

Recently, nanocrystalline Fe-Cu-B and Fe-Cu-Si-B soft magnetic alloys with high saturation magnetic flux density more than 1.8 T and low coercivity of about 6 A m^-1 were developed by annealing melt-quenched alloys containing 1.3 -1.5 at % Cu and 0 – 7 at % Si. In this work, the magnetic properties of annealed Fe_77.5-xCu_xSi_15.5B₇ alloys with high Si content prepared by melt spinning are reported. The appropriate Cu content in this alloy system shifted to Cu content higher than that of the reported Fe-Cu-Si-B alloys with high B_s. The annealed alloy with x = 2.0 showed the H_c of about 10 A m^-1, the B₈₀₀₀ of 1.47 T, and low magnetostriction of +4.8 x 10^-6.

The effects of additional C, P or Si on the structure and magnetic properties of melt-spun Fe₅₅Pt₂₅B₂₀ alloy have been investigated. The mixed structure consisting of amorphous and fcc-FePt phases was formed for the Fe₅₅Pt₂₅B₁₈M₂ (M=B, C or Si) alloys. Addition of 2at.% of P increased the amorphous-forming ability of the Fe-Pt-B alloy, leading to the formation of an amorphous phase in the M=P alloy. A homogeneous nanocomposite structure consisting of hard L1₀-FePt and soft Fe₂B magnetic phases with average grain sizes of ∼ 40 nm was formed in all the melt-spun alloys annealed at 825 K for 900 s. The good hard magnetic properties with high coercivity of over 540 kA /m were obtained for the M = C or P nanocomposite alloys.

Magnetic power losses of [(Fe_1-xCo_x)₇₅B₂₀Si₅]₉₃Nb₄Y₃ (x = 0, 0.2, 0.4) metallic glasses have been investigated. Bulk samples were prepared by water-cooled Cu-mold injection casting technique with shapes of cylinders (0.8 mm diameter and 30 mm length) and toroids (10 mm external diameter and 0.5 mm thickness). Ribbons prepared by the melt- spinning technique were also analyzed. Glassy structures were confirmed by the presence of a main halo in XRD and by crystallization signal in DSC. Power losses were studied with a digital wattmeter over a range of frequencies from 1 to 400 Hz at selected peak inductions. Ribbons show smaller losses than bulk samples, presenting 24.5 J/m³ at 50 Hz and 0.65 T peak induction. It was observed that the Co addition reduces significantly the power losses. A separation theory was applied in order to explain the square root behavior of the measured power losses as a function of frequency and the results are in good agreement with the experimental data. The magnetic data were used to identify the presence of crystalline inclusions in the magnetic bulk metallic glasses. The effect of sample shape and composition on magnetic properties will be discussed.

Magneto-thermo-gravimetric (MTG) technique is highly informative about the changes in the magnetic state, as well as structural changes in a system, which cannot be often noticed in calorimetric measurements. We demonstrate the versatility of this technique in determining the magnetic transition temperature, and the subsequent crystallization process in a (Fe_0.72B_0.24Nb_0.04)_95.5Y_4.5 Bulk Metallic Glass (BMG). MTG and DSC analyses were carried out at the heating rate of 0.67 K/s from RT ~ 1170 K. As a result of the repeated MTG measurements, a magnetic 2nd amorphous phase was observed in the BMG sample, which could be the first measurement for the Magnetic Short Range Ordering (MSRO). Consequently, the MTG measurement is proved as the most convenient method for determining the various structural and magnetic transitions in a glassy material.

FeCuNbSiB-ribbons with optimized nanocrystalline microstructure possess a unique combination of near-zero magnetostriction, high saturation induction and low magnetization losses. Due to the absence of distinct intrinsic anisotropies, the magnetization curve can be adjusted by field-annealing to square or flat shape. It is well known that excess losses are an important loss component of soft magnets with square hysteresis loop. Yet, even cores of flat type loop can show significant excess losses. The paper reviews the loss mechanisms for excess losses in nanocrystalline soft magnets on the basis of Kerr-microscopy observation and loss theory and compares it to amorphous materials.

Addition of nanosized intermetallic or metallic phases into corundum considerably raises mechanical behavior of the material. In this work, the nanocomposites of α-Al²O³/intermetallic and α-Al²O³/metal systems were obtained by mechanochemical reduction of α-Fe²O³ by Al (and by solid solution of Al in Fe). The mechanochemical reduction process of hematite by various amount of metal-reducer was studied by IR and Mössbauer spectroscopies, and by X-ray synchrotron radiation diffraction technique.

The Fe48.75Pt26.25B₂₅ powder was prepared by high-energy ball milling of the crystalline melt-spun ribbon. The X-ray diffraction and transmission Mössbauer spectroscopy measurements allowed the identification of the tetragonal FePt and orthorhombic FeB phases in the as-quenched alloy. The ball milling of the ribbon led to the transformation of the ordered tetragonal FePt phase into a disordered cubic FePt solid solution with the average crystallites size of about 15 nm. Annealing of the as-milled powder recovered the nanocrystalline tetragonal FePt phase. Differences in magnetic properties between the as-milled and annealed powders were revealed by hysteresis loop and magnetization vs. temperature measurements.

Influence of controlled Co addition on structural and magnetic properties of (Fe100-x Co_x)₇₈Si₉Nb₃B₉Cu₁ (x = 0, 20, 40, 60) alloys has been studied using DTA, XRD, magnetic measurements and Mössbauer spectroscopy. Results show that the variation of Co content affects the stability of the alloy against crystallization. Volume fraction of the nanograins varies only slightly and remains around 60 %. The corresponding grain diameter ranges between 13 to 15 nm. Obtained lattice parameter values suggest that the studied nanocrystalline samples consist of bcc Co-Fe phase with Si impurities, with Co content ranging between 38 to 61 % and Si content ranging between 7 to 15 %. Coercive field for as-cast specimens practically does not change with increase of Co content whereas for annealed samples it exhibits appreciable increases. Mössbauer measurements show that with increase of Co content, there is a change in: the environment around Fe-atom; spin texture and disorder in the studied specimens.

Bulk samples were prepared by in-situ devitrification and consolidation of gas atomized Al₈₇Ni₈La₅ amorphous powder. Consolidation was carried out at different temperatures by spark plasma sintering, which leads to highly dense bulk specimens with a microstructure consisting of fcc aluminum together with Al₁₁La₃ and Al₃Ni intermetallic compounds. The consolidated powder displays a remarkably high compression stress, which depends on the sintering temperature and ranges between 900 and 1000 MPa, combined with plastic strain varying between 10 and 20 %. These results indicate that the mechanical properties of the samples can be tuned within a wide range of strength and ductility as a function of the sintering temperature used.

The process of mechanochemical interaction of SiO₂ with Al was studied. The mechanical activation of the SiO₂/Al mixture results in a decrease of the temperature of chemical interaction of SiO₂ with Al from 1100°C to about 600°C. The mechanochemically prepared SiO₂/Al may serve as a precursor for Si/Al₂O₃ composites formed by subsequent self- propagating high-temperature synthesis (SHS). For the first time, the SHS process (reduction of SiO₂ by Al) was followed in-situ by the time-resolved X-ray synchrotron diffraction.

This paper will review selected aspects of the processingstructureproperty relationships in ultrafine grained (ufg- grain sizes 100 to 500 nm) and nanocrystalline (nc- grain sizes < 100 nm) materials. Of the various processing methods to obtain fine grain size materials, the two that have provided bulk artifactfree samples are electrodeposition and severe plastic deformation. The processing methods and important variables will be described for these techniques. Since the stability of the nanocrystalline microstructure is important for both processing (e.g. consolidation of powders) and elevated temperature mechanical property studies, the stability of nanocrystalline grain sizes as influenced by solute additions will be discussed. While hardness and strength usually increase with decreasing grain size, ductility is typically poor. There are now, however, a number of examples of nanocrystalline materials which combine high strength with good ductility. An example from the author's laboratory on nanocrystalline Cu with optimized mechanical properties will be presented.

Cu-10vol.%Al₂O₃ nanocomposite powders were produced using two high energy milling routes and heat treated at 150, 300, 400 and 500°C for 1 hour, respectively, to determine the thermal stability of the microstructure and the micohardness change of the materials as a function of the annealing temperature. Annealing of the as-milled powders at 150°C caused recovery and recrystallisation that leads to significant decrease in dislocation density and slight decrease of microhardness. Increasing the annealing temperature to 400°C causes slight coarsening of the Cu grains and corresponding slight decrease of microhardness. Further increasing the annealing temperature to 500°C causes significant coarsening of the Cu grains and cause significant decrease in microhardness. The effects of different factors on the thermal stability and micohardness change of the Cu-Al₂O₃ are discussed.

In this study, several ways of bulk nanocrystalline Al-based alloys' production by high-pressure compaction of powders were explored. The effect of chemical composition and compaction parameters on the structure, quality and mechanical properties of the bulk samples was studied. Bulk nanocrystalline Al-Mm-Ni-(Fe,Co) alloys were prepared by ball-milling of amorphous ribbons followed by consolidation. The maximum microhardness (540 HV0.1) was achieved for the samples compacted at 275 °C under 7.7 GPa (which resulted in an amorphous bulk) and nanocrystallised at 235 °C for 20 min. Another group of the produced materials were bulk nanocrystalline Al-Si-(Ni,Fe)-Mm alloys obtained by ball-milling of nanocrystalline ribbons and consolidation. The hardness of these samples achieved the value five times higher (350HV) than that of commercial 4xxx series Al alloys. Nanocrystalline Al-based alloys were also prepared by mechanical alloying followed by hot-pressing. In this group of materials, there were Al-Fe alloys containing 50-85 at.% of Al and ternary or quaternary Al-Fe-(Ti, Si, Ni, Mg, B) alloys. Microhardness of these alloys was in the range of 613 – 1235 HV0.2, depending on the composition.

AgI-AgMoO₄ materials were obtained by rapid quenching method. Their structures were investigated by X-ray spectroscopy and Scanning Electron Microscopy (SEM). Additionally the compressibility of the amorphous samples was investigated. A relation between electrical and mechanical properties was suggested. It was also found that short range order of amorphous samples changes with composition.

Pure tensile and combined torsion-tension deformation has been investigated for three Al-Mg alloys: (Al+0.50wt%Mg), (Al+0.85wt%Mg) and (Al+1.60wt%Mg). Plastic instability behavior is observed in the case of combined torsion-tension deformation. The onset and disappearance of this instability is found to depend on some parameters as applied axial tensile stress, working temperature and sample grain diameters. The influence of plastic deformation on the electrical resistivity for such materials has been investigated at room temperature. Both torsion-tension deformation and electrical resistivity were found to decrease on plastic straining for samples as received, and pre-annealed from 373 till 573 K, and then it increased for samples pre-annealed at 673 K and 773 K. The results show negative tensile strain (ΔL/L₀) for samples annealed in the temperature range of the first annealing stage which is inferred to hardening due to internal stresses formed on clustering of Mg atoms at grain boundaries as well as the formation of Luders bands at the grain boundaries during twisting. The positive result observed for samples pre-annealed at higher temperature is attributed to dispersion of Mg precipitates inside the grains during the recrystallization process.

Following the discovery of Coulomb oscillation by the proton tunneling in Ni-Nb- Zr-H glassy alloys, we investigated the temperature-dependent hydrogen effect for dc electric conduction of the (Ni₃₆Nb₂₄Zr₄₀)_100-xH_x (0≤x≤15.7) glassy alloys. Electric current-induced voltage oscillation at 660 kHz and evidence of the Coulomb staircase of I-V characteristics show Coulomb oscillation in nanoscopic size tunnel junctions arranged in a low-capacitance, based on proton resonance among the multiple-junctions of the glassy alloys in the temperature range of 240 K to 6 K.

The analysis of magnetocaloric effect in microcrystalline and nanocrystalline TbFe₁₁Ti and TbFe₈Ti intermetallic compounds was carried out. It was found that the dependence between the reduction of the grain size below a single domain size and value of magnetocaloric effect has a complicated nature. Probably, it is connected with the influence of intergrain exchange interaction in nanocrystalline alloys.

The relationship between mechanical properties, the glass transition temperature and the heat content needed to reach it is discussed for various glass-formers to prove aspects of the mechanism of shear band propagation. Temperature profiles around shear bands are determined by means of finite element modelling. The results are used to interpret serrations and the effect of specimen size.

The aim of this work is to compare the isothermal crystallization kinetics in stoichiometric Ge:Sb:Te as well as in un-doped and Ge doped Sb:Te eutectic films. Experimental results have shown a different crystallization mechanism in the investigated films. In Ge₂Sb₂Te₅ and Ge₁Sb₂Te₄ films the analysis of the kinetic results showed that at the beginning of crystallisation a metastable phase appeared with the Ge₁Sb₄Te₇ composition, this is followed by the nucleation and growth of the stable fcc phase up to full crystallization. In contrast Ge₄Sb₁Te₅ films show diffusion control growing from small dimension grains with decreasing nucleation rate. Sb:Te eutectic films doped by Ge have shown that the addition of Ge increased the effective activation energy of crystallization, but the mechanism of crystallization (diffusion-controlled growth of particles of appreciable initial volume) did not depend on Ge concentration.

An ordered B2 intermetallic compound with composition Ti₄₅Zr₃₈Al₁₇ was prepared by copper mold casting. The density of the alloy is 5.078 g/cm³, whereas the Poisson's ratio and the Young's modulus are 0.38 and 70 GPa, respectively. Room temperature compression tests show good mechanical properties, namely, a high strength of 1650 MPa combined with a plastic strain of about 19.5 %. These parameters make the material an interesting candidate for biomedical applications like prostheses. Structure investigations reveal that during compression the alloy undergoes a martensitic transformation which proceeds from the parent B2 structure to the orthorhombic B19 structure through an intermediate step involving a hexagonal phase.

In the present study, in order to find out an grain refinement mechanism, 0.1wt.% Al-10wt.%Ti master alloy was added into A3003 alloy melt contained in graphite crucible and in alumina crucible, and then the melt holding time at 750°C was systematically changed from 1 min up to 120 min. It is interesting to note that the grain refinement and fading phenomena remarkably depend on the crucible material. The fading effect in the specimens using alumina crucible can be explained as the result of TiAl₃ phase dissolution into molten aluminium matrix. In the specimens using graphite crucible, the grain refinement was occurred gradually with increasing holding time. It was suggest that the continuous grain refinement is due to transition of refinement mechanism from TiAl₃ phase to TiC phase. It can be mentioned that the TiC formed from titanium and carbon solute in the aluminium melt, which came from the Al-10Ti alloy and the graphite crucible.

Formation of phases in the course of crystallization from amorphous state in rapidly quenched Fe-Ni-Nb-B was investigated with respect to the ratio of Fe/Ni and content of B in a wide compositional interval. A transition from nanocrystalline bcc-Fe formed during first crystallization stage into fcc-FeNi and Fe₂₃B₆ fcc-type structure with large unit cell accompanied by a distinct change in the transformation kinetics was observed with increasing Ni content. The emergence of these phases during (nano)crystallization is investigated with respect to the changes of local order induced by large variations of Fe/Ni and to the presence of large atoms of Nb. Diverse methods of high-resolution structure characterisation are used to identify and quantify phases with similar interplanar spacing. A deviation from a typical two-stage pattern leading to a rapid single-stage crystallization with direct formation of stable phases, incidentally present also in the structure of the precursor master alloys, is interpreted within the framework of a model of cluster structure of amorphous state. Links between the expected local ordering in amorphous state and the structure of crystallizing phases are followed and compared with similar phenomena observed in Nb-containing Co-rich Fe-Co-Nb-B system.

Effect of the melt ejection temperature on the microstructures of (Fe_xCu_1-x)₆₂Si₁₃B₉Al₈Ni₆Y₂ (x=0.48, 0.60 and 0.71) alloys was investigated. Rapid cooling of the examined alloys from the temperature range conventional to single-phase amorphous alloys brought about a non-uniform microstructure due to a liquid/liquid phase separation prior to cooling. The systems with a miscibility gap need to be heated over a critical temperature where homogeneous liquid exists. Microstructures of the ribbons melt spun from the homogeneous melt region are characterized by presence of the spherical precipitates distributed in homogeneous matrix. Both, precipitates and matrix, can constitute either the Fe-rich or the Cu-rich phases depending on the alloy composition. The studies confirmed amorphous nature of the Fe-rich phases, both matrix and precipitates whereas the Cu-rich liquid crystallized due to lower glass forming ability.

Six Cu_100-xZr_x amorphous alloys (x in the range 35.7 - 60 at. percent) were prepared via chill block melt spinning (CBMS) method under low pressure Helium atmosphere. Their crystallization and viscous flow behavior was studied with the aid of Perkin Elmer DSC 2C and Perkin Elmer TMS 2 devices, respectively. The viscous flow temperature dependencies at a heating rate of 20 K min^-1 were interpreted on the basis of the f ree volume model. The DSC and TMS data were used to determine the fragility number m of Angell in three different ways as a function of alloy composition. It has been shown that the fragility number goes over a maximum and has a minimum at x very near to the alloy composition Cu₆₄Zr₃₆ in good agreement with the results of Donghua Xu et al. and Wang D et al. The experimental techniques and model interpretation used provide a tool for understanding the glass forming ability (GFA) and relaxation phenomena in metallic glasses.

Al₈₅Ce₈Ni₅Co₂ metallic glass ribbon was devitrified by heat treatments just below its glass transition temperature and by severe plastic deformation applying ball milling and high pressure torsion. Evolution of the microstructure, thermal stability and further thermal history were compared for the different devitrification processes. Based on this mapping of phase selection processes, microstructural changes can be predicted for high temperature and/or high stress compaction which are often required for application of this light weight alloy.

The structure formation in hypereutectic Al-Sc and hyperperitectic Al-Zr, Al-Hf alloys with concentration of alloying element up to 1.3 at.% have been studied under conditions far from thermodynamical equilibrium depending on cooling rate and quenching temperature. The co-operative growth structures are solidified with cooling rate of 10²-10³ K/s regardless of overheating and under cooling rate of 10⁵-10⁶ K/s at small overheating. The phase compound of these structures is α-solid solutions and phase with L1₂-ordered structure or two solid solutions with different concentrations of alloying element. The large overheating leads to formation of α-solid solution anomalously supersaturated under cooling rate of 10⁵-10⁶ K/s.

The effect of Al and Zr on the viscosity of the supercooled liquid in melt-spun Zr-Ti-Nb-Cu-Ni-Al glassy ribbons has been evaluated by parallel plate rheometry. The change of composition drastically affects the viscosity of the samples. The viscosity of the supercooled liquid and the fragility parameter (D*) increase with increasing Al or decreasing Zr contents, indicating an improved glass-forming ability. At the same time, the temperature of the glass transition shifts to higher values. A clear correlation between fragility parameter and glass transition has been found. This correlation provides a guide for the estimation of D* for this particular system when the glass transition is known.

Silver based alloys are used widely when brazing copper based alloys. Due to its high cost, researchers try to obtain silver free brazing alloys, in the shape of amorphous structure ribbons, avoiding thus the formation of intermetallic compounds that diminish its ductility and plasticity. In this paper, the authors present their results in trying to obtain brazing alloys from the Cu-Zn-Ni-P family, ribbon shaped with amorphous structure, using the melt spinning method. The amorphous character of the processed alloy is emphasized by X-Ray diffraction, and the brazed joints made with the alloy were submitted to metallographic analysis and shearing tests.

In this paper, the microstructures developed in highly undercooled samples from Cr-Mo-V tool steel of ledeburite type during non-equilibrium solidification in levitation and on a copper substrate are compared. The microstructures in spherical samples solidified during levitation are dependent on the level of undercooling reached prior to spontaneous nucleation. In the whole volume of a single rapidly solidified sample, microstructures are quasi-homogeneous. Rapidly solidified splat samples were prepared using copper substrate solidification from the melt with various initial undercooling. As an example, the microstructure in the sample solidified from the initial undercooling of 100 K with morphologically different microstructural regions is presented. Carbides of solidification origin with different size, morphology and location were found in samples solidified in levitation and on a substrate as well.

There are no reported Al-rich alloys that are both easy glass formers upon melt-spinning processing without RE additions and have a crystallization temperature sufficiently high to ensure long metastable life times at room temperature. A representative of a new family of ternary Al-based glasses is described here that contains Ni and Ta with total additive element concentration as low as 15 at % and its devitrification characteristics are reported. Using the melt-spinning technique under protective atmosphere, the alloy Al₈₅Ni₉Ta₆ easily forms a ductile glass, with the crystallization onset temperature Tx = 370°C, enthalpy of transformation ΔH = 68 J/g and an activation energy of crystallization Ea = 266.83 kJ/mole, i.e., 2.76 eV.

Less expansion and more shrinkage along the ribbon axis than transverse to the axis is generally observed during temperature cycle when the dilatation of as-cast ribbons is measured. This anisotropy is seen to relax together with modest as-cast magnetic anisotropy if the sample has been cycled up to ∼400°C prior to the test. Often but not always, the as-cast magnetic anisotropy shows the sign as expected after tensile stress annealing. During ribbon solidification, tensile stress can create anelastic strain or even structural anisotropy which results in both the observed anisotropies. Ribbons quenched on air are known to bear some macroscopic heterogeneity which acts by forces between surfaces and ribbon interior. These forces could interfere with the relaxation of the as-cast anisotropies. Tests show that the interference is weak and the heterogeneity acts isotropic in the ribbon plane and induces magnetic anisotropy of its own.

Fe-6.5wt%Si high silicon steel has superior magenitic properties. However, such high Si content results inroom-temperature embrittlement and poor workability due to the formation of ordered intermetallic phases. Zone Melting Liquid Metal Cooling directional solidification technique was employed to produce the Fe-6.5wt%Si alloy with columnar-grained structures. The cooling rate of directional solidificationplays a critical role in maintaining the grain growth, and the rate around 3 K/s is an optimum conditionto form columnar-grained structure and to improve its ductility.

In this work, structural and magnetic properties of metastable Nd-rich Nd₈₀Fe₂₀ binary and (Nd-Ga)₈₀Fe₂₀ ternary alloys are investigated. The specimens were prepared at different cooling rates, varying from 5 to 150 K/s by using copper mold casting and at 10⁶ K/s by melt spinning. Specimens with different dimensions were prepared in order to change the cooling rate. The aim of the present work was to characterize a metastable hard magnetic phase referred to as 'A1' in Nd₈₀Fe₂₀ alloys, which forms as a part of the fine eutectic depending on the cooling rate. In order to stabilize the formation of A1, (Nd100-xGa_x)₈₀Fe₂₀ (x = 5, 10, 15) alloys were rapidly cooled at a solidification rate of ≤ 150 K/s.

Effect of the quenching wheel velocity in the range 20.7-26.5 m/s on the cooling rate as well as on the structure and microtopology of the contact surfaces of the glass-forming FeNiPB melt-spun ribbons has been experimentally studied. Both the values of the cooling rate and heat transfer coefficient at the wheel-ribbon interface estimated from the temperature vs. time curves recorded during melt spinning runs are in the ranges (1.6-5.2)×10⁶ K/s and (2.8-5.2)×10⁵ Wm^-2K^-1, respectively, for ribbon thicknesses of 31.4-22.0 μm. It was found that the density of the air pockets at the underside surface of ribbons decreases while its average depth remains essentially unchanged with the wheel velocity. Using the surface quality parameters the values of the heat transfer coefficient in the areas of direct ribbon-wheel contact were evaluated to be ranging from 5.75 to 6.65×10⁵ Wm^-2K^-1.

Aluminum-Silicon alloys are sought in a large number of automotive and aerospace applications due to their low coefficient of thermal expansion and high wear resistance. The present study focused on structural transformations as a function of the temperature of rapidly solidified hypereutectic Al_100-xSi_x (x = 12, 22 and 40) alloys. Different structures out of equilibrium have been obtained after casting in sand, graphite and copper moulds and by melt spinning. The retained Si content in supersaturated alpha Al and the precipitation of Si is discussed in the light of the dilatometer studies [1, 2, 3] complemented by metallographic microscopy, XRD and DSC [4] measurements. A Kissinger analysis was used to determine the activation energy for the precipitation of supersaturated Si content.

The microstructural and mechanical characterizations of the rapidly solidified Nb₂₀Ti₄₀Ni₄₀ (at%) hydrogen permeation alloy have been performed. An as-melt spun ribbon consists of an amorphous phase with sound bending ductility. The successive crystallization of B2-TiNi and bcc-Nb solid solution phases takes place during heating. The amorphous phase is stable in the specimens annealed below 773 K. The specimens annealed from 798 to 923 K are quite brittle, although those consist of fine equiaxed grains less than 50 nm. With annealing above 948 K for prolonged periods the grain size is increased to about 150 nm or more and the hardness is decreased about 260 Hv or less. Consequently, the ductility is recovered. The fracture toughness of as-melt spun and annealed ribbons is also investigated by the micromechanical test.

X-ray diffraction measurement was performed on an Mg₅₀Ni₅₀ amorphous alloy prepared by mechanical alloying under an Ar atmosphere. Reverse Monte Carlo (RMC) simulation based on the X-ray diffraction data was used to construct a three-dimensional atomic arrangement of the amorphous alloy. In addition, the local environments around the Mg and Ni atoms were investigated by using Voronoi polyhedral analysis on the RMC configuration. The results show that isosahedral structures are predominant around the Mg and Ni atoms in Mg₅₀Ni₅₀, although prismatic local structures are present around some of the Ni atoms.

We have investigated special effect related to the crystalline phases at the surface layers of as-quenched FeMoCuB ribbons prepared by planar flow casting using several experimental methods. These effects contradict the usual pattern of surface crystallinity formation due to insufficient quenching rates or glass forming ability. Influence of substitution of Fe by Co and varying B in the basic system (Fe_1-xCo_x)_79-yMo₈Cu₁B_12+y on these effects as well as influence of flux-melting prior to rapid quenching were analyzed. Disappearance of surface crystallinity with simultaneous addition of Co and B was observed. Similar effect was obtained also by using flux-melting of the master alloy prior to rapid quenching. Possible micromechanisms leading to this behavior were discussed. The evolution of surface structure was monitored in detail during in-situ linear heating in the temperature range 300K-1080K via 2D X-ray diffraction patterns using synchrotron radiation.

Important energy and time savings can be achieved with the thermal treatment of materials by replacing conventional heating methods with microwave heating. The nanocrystallization of Co-Fe-W-B amorphous alloy powders under microwave irradiation was followed for the first time by in situ time-resolved synchrotron radiation powder diffraction. It is shown that even a very short exposure to the electromagnetic field (single pulse microwave application) typically of the order of a few seconds is sufficient to obtain the bulk nano-crystalline state. A metastable high-temperature Co-W-B orthorhombic phase forms during the microwave heating, which gradually transforms to the tetragonal Co₂B stable phase.

Single crystals of a half-metallic ferromagnetic compound CrO₂ were synthesized using controlled thermal evaporation of CrO₃ in an autoclave at 1.5 bar pressure at moderate temperature 673 K. These CrO₂ crystals lay in a Rutile tetragonal crystal structure of D¹⁴_4h:P4₂/mnm space group, with lattice parameters a = 0.4423 nm and c = 0.2918 nm. The lattice volume 0.0571 nm³ determines 4.88 g/cm³ density, assuming a lattice consisting of two CrO₂ formula units. Scanning electron microscopic images reveal rectangular bars of single CrO₂ crystals of 6.0-8.0 μm lengths and 1.0-1.5 μm widths. When heating in ambient air pressure the crystals relieve part of the oxygen according to the CrO₂ → Cr₂O₃ phase transformation with a sharp peak in the first derivative of the thermogravimetric curve at temperature as early as 570 K, with a partial mass loss of 1.2%. A complete transformation appears around 775 K, with 3.0% mass loss. The CrO₂ → Cr₂O₃ conversion reflects in a sharp endothermic peak in DTA at 576 K. The CrO₂ crystals have the saturation magnetization of 68 emu/g, coercivity ~340 Oe, and remanent magnetization ~ 61 emu/g at room temperature.

The phases and their stability in Al₇₀Ti₃₀, Al₇₅Ti₂₅ and Al₈₀ Ti₂₀ planar flow cast ribbons and their master alloys have been studied. Analyses are based on the XRD and DTA measurements. In all samples the high-temperature Al₁₁Ti₅ and Al₅Ti₂ superstructures (1d-APSs) have been present. The stable low-temperature phases Al₂Ti, Al₃Ti and Al have been identified, too. The 1d-APSs being formed as first during the quenching persist for considerable time also at low temperatures. During heating in reverse, only the 1d-APSs remain before melting, being formed after large superheating from all low-temperature phases in Al₇₀Ti₃₀ and Al₇₅Ti₂₅ alloys. The phase Al₁₁Ti₅ is reported in the Al₃Ti and more Al-rich alloys for the first time.

The study of the temperature and time viscosity dependences of the amorphizing Co_65.5Fe_6.5Si₁₈B₁₀, Co_65.5Cr_6.5Si₁₈B₁₀, Co₆₉Cr₃Si₁₈B₁₀ melts has been performed. It has been shown that the temperature and time viscosity dependences for each alloy are of the same nature. The anomaly attended by the changing of the energy activation of the viscous flow has been first determined in the viscosity polytherms under heating conditions in the vicinity of t* (t* is the characteristic temperature for each alloy, i.e. the temperature of the anomaly on the polytherm of the viscosity). This anomaly is caused by the change of the short-ordering type in the liquid phase in this temperature region as well as by the transition of its low-temperature structure into the high-temperature one. The latter being further cooled is retained up to the solidification temperatures and results in the viscosity hysteresis. It has been shown that the decrease of the alloying element concentration results in a substantial displacement of the anomaly temperature, t*, to the lower temperature region (t*=1360°C for Co_65.5Fe_6.5Si₁₈B₁₀, Co_65.5Cr_6.5Si₁₈B₁₀ and 1220°C for Co₆₉Cr₃Si₁₈B₁₀).

Cu-based amorphous (Cu₅₄Zr₂₂Ti₁₈Ni₆) coating was produced through cold spraying as a new fabrication process. The microstructure and macroscopic properties of the amorphous coating layer were investigated and compared with those of the cold-sprayed, pure Cu coating. Amorphous powder was prepared via gas atomization, and Al 6061 was used as the substrate plate. The X-ray diffraction results showed that Cu-based amorphous powder could be successfully deposited through cold spraying sans any crystallization. The Cu-based amorphous coating layer (300-400 μm thick) had 4.87% porosity. The hardness of the Cu-based amorphous coating was 412.8 H_v or 68% of the hardness of the injection-casted bulk amorphous material. The wear resistance of the Cu-based amorphous coating was found to be three times higher than that of the pure Cu coating. The results of the 3-point bending test showed that the adhesion strength of the Cu-based amorphous coating layer was higher than the pure Cu coating. The hard Cu-based amorphous particle was also observed to be able to deform soft substrate easily through particle collisions; thus generating strong adhesion between the coating and substrate. Note, however, that the amorphous coating layer unexpectedly showed lower corrosion resistance than the pure Cu coating, possibly due to the higher porosity of the cold-sprayed amorphous coating.

The microstructure and the tensile properties of a spray-formed and extruded Al-9Si-4Cu-1Fe alloy were investigated. Manganese (0.3, 1, 2 in wt%) was added to the alloy to avoid the formation of the needle-like β-AlFeSi intermetallic phases that are highly detrimental to the alloy's ductility. The deposits were extruded at 623K with a n area reduction of 5 to 1. Small faceted dispersoids surrounding the equiaxial α-Al matrix, mainly in the form of silicon particles, were identified by SEM-EDS, as well as the Mn-containing α-Al15(Fe,Mn)3Si2 phase. The presence of the needle-like β-Al(Fe,Mn)Si was scanty, even with the lowest Mn content. The room temperature tensile tests of all the extruded alloys showed a significant increase in elongation to fracture when compared with the values observed fo r the as-spray formed deposits.This result can be ascribed to the elimination of porosity promoted by the extrusion process and to the smaller grain size of the extruded samples.

For the description of the ion-ion interaction in a transition metal the method of pair potential calculation introduced by Wills and Harrison is used. The potential is represented as a sum of the s-electron and d-electron contributions. The first is calculated in the framework of the Bretonnet and Silbert local model pseudopotential. On the basis of this approximation the thermodynamic properties are calculated by using the variational method of the thermodynamic perturbation theory. The formalism is applied to calculate the free energy of mixing for the Fe-Ni liquid system at different compositions and temperatures. An agreement with the available experimental data is quite satisfactory.

The energy saving produced by the equalization of Fermi energies of a crystal and its melt is determined by adding a negative fraction _sl(T) of the fusion heat to the Gibbs free energy change ΔG_2ls associated to a charged crystal formation in glass-forming melts. In bulk metallic glasses, _ls(T_m) is larger than 1 at the melting temperature T_m and only determined by the knowledge of the free volume disappearance temperature. When the unmelted intrinsic crystals have a radius R_nm much smaller than the critical radius R*_2ls, _sl(T) is strongly reduced by the quantification of electronic levels in the large electrostatic potential created by the electron transfer from the crystal to the melt. The reduced value _nm0 of _sl(T_m) for R_nm=3.2E-10m in Zr_41.2Ti_13.8Cu_12.5Ni₁₀Be_22.5 is determined by comparing the experimental Time-Temperature-Transformation diagram measured by electrostatic levitation to the calculated one. It exactly corresponds to the first energy level of one s state electron moving in the same spherical attractive potential and in vacuum in spite of the fact that, in a metal, the charge screening is built by many-body effects.

Bulk samples of Cu₈₄Co₁₆ composition were undercooled and rapidly solidified using the electromagnetic levitation technique under a static magnetic field of 2 T. A droplet-shaped microstructure was frozen in due to metastable phase separation in the undercooled liquid. A singular droplet size distribution was determined for the minority Co-rich phase, which differed from a bimodal one observed in the samples levitated without the static magnetic field. Such an effect of the magnetic field was found to be similar to that of reduced gravity of parabolic flights.

Non-equilibrium solidification of undercooled Ti-Al-Nb melts with compositions around the border of the α-Ti/β-Ti phase domains are investigated using the electromagnetic levitation technique. Detailed thermal histories of rapid recalescence processes acquired with a high time-resolution by a fast responding photo-diode are compared to in situ analyses of the solidified structures by using energy dispersive x-ray diffraction. The primary formation of the β-Ti phase is observed independent on the undercooling level up to a maximum undercooling of 300 K at compositions near the border of the α-Ti regime. On cooling the primary phase completely transforms into the α-Ti phase from which γ-TiAl precipitates at considerably lower temperatures.

We report on investigations on the atomic dynamics in melts of different binary Zr-Ni alloys and of the ternary glass-forming Zr₆₀Ni₂₅Al₁₅ alloy. The liquids are containerlessly processed in an electromagnetic levitator that is combined with quasielastic neutron scattering at the time of flight spectrometer TOFTOF of the FRM II. Ni self-diffusion coefficients are determined that exhibit an Arrhenius-type temperature dependence with comparatively large activation energies ranging between 0.64 and 0.90 eV. Although glass forming abilities and melting temperatures for these alloys exhibit large differences, the absolute values of the self-diffusion coefficients are similar at same temperature.

The high temperature properties of hydrogenated Ti₅₀Zr₂₅Co₂₅ ribbons were investigated up to 380°C. As indicated by tensile tests at room temperature, hydrogen-induced strengthening occurred until ∼21 at.% hydrogen. At this range of hydrogen concentration (Hconc) varying from 0 to ∼21 at.%, tensile tests conducted at high temperatures (300 to 400°C; strain rate: 10^-4s^-1) showed that in addition to enhancement in strength, elongation larger than 20% was obtained. The temperature range at which such property improvements occurred depends on the hydrogen concentration. The change in the mechanical properties in this range of Hconc and temperature is attributed to the corresponding changes in the thermal behaviour of the alloy, along with the inherent structural modifications induced by hydrogen addition.

This article has been retracted at the request of the corresponding author due to substantial overlap with a previously published paper

Glassy Solidification Criterion of Zr₅₀Cu₄₀Al₁₀ Alloy Materials Transactions, Vol. 48, No. 6 (2007) pp. 1363 to 1372 Special Issue on Materials Science of Bulk Metallic Glasses-VII

The corresponding author acknowledges that this article was submitted to the RQ13 proceedings by him without the knowledge of or consultation with the co-authors and apologises accordingly.

Published 2 November 2010