Table of contents

Preface

The seminar "Development of Materials Science in Research and Education", held on 4-8 September 2017 in Kežmarské Žlaby (Slovakia-High Tatras), was already the twenty seventh in the series started at Gabcíkovo in 1991 by the initiative of the Czech and Slovak Association for Crystal Growth and the Slovak Expert Group of Solid State Chemistry and Physics. The objective of this meeting offered an opportunity to Czech and Slovak teachers and scientists as well as guests from other countries who are working in the field of Materials Science to present their recent results and experience and to exchange new ideas and information.

The scientific sessions covered the following topics on materials science:

• Trends in development of materials research

• Education of materials science at the universities

• Information about the research programmes of individual institutions

• Information about equipment for preparation and characterization of materials

• Results of materials research

This workshop was aimed at creation of a stimulating atmosphere of cooperation and at the support of patient dissemination of scientific ideas and propagation of materials science in education. At the seminar, 38 participants presented 36 interesting talks.

Editors

Kežmarské Žľaby, 4 - 8 September 2017

List of Organizers, Under the auspices, SCIENTIFIC COMMITTEE, ORGANIZING COMMITTEE, SPONSORS OF DMSRE 2017 SEMINAR are available in this PDF.

All papers published in this volume of IOP Conference Series: Materials Science and Engineering have been peer reviewed through processes administered by the proceedings Editors. Reviews were conducted by expert referees to the professional and scientific standards expected of a proceedings journal published by IOP Publishing.

Nucleation studies of undercooled metallic melts are of essential interest for the understanding of phase selection, growth kinetics and microstructure development during their rapid non-equilibrium solidification. The paper deals with the modelling of nucleation processes and microstructure development in the hypoeutectic tool steel Ch12MF4 with the chemical composition of 2.37% C, 12.06 % Cr, 1.2% Mo, 4.0% V and balance Fe [wt. %] in the process of nitrogen gas atomization. Based on the classical theory of homogeneous nucleation, the nucleation temperature of molten rapidly cooled spherical particles from this alloy with diameter from 40 μm to 600 μm in the gas atomization process is calculated using various estimations of parameters influencing the nucleation process – the Gibbs free energy difference between solid and liquid phases and the solid/liquid interfacial energy. Results of numerical calculations are compared with experimentally measured nucleation temperatures during levitation experiments and microstructures developed in rapidly solidified powder particles from the investigated alloy.

The Sn–Zn–Al alloys are one of significant candidates in the proposal of alternative lead-free solders for higher temperature soldering. This paper deals with the study of the aluminum–tin–zinc system. Twenty Sn–Zn–Al alloys together with six binary Sn–Zn alloys were prepared and studied experimentally. Alloys were prepared from pure Sn, Zn and Al (melting and cooling in a vacuum resistance furnace). The specimens were studied metallographically including the micro-hardness measurements, complete chemical analysis (ICP-AES, OES), X-ray micro-analysis of alloys by SEM and EDX in order to determine the composition and identification of individual phases. Significant temperatures and enthalpies of phase transformations were determined by DTA. After long-term annealing of selected alloys in vacuum followed by quenching the structural and chemical microanalyses of the present phases and their limit concentrations were carried out. The achieved results were compared with the thermodynamic modelling of the ternary Sn–Zn–Al system (computer programs THERMOCALC, MTDATA, PANDAT and databases CALPHAD, COST). Electrical resistivity, density, magnetic susceptibility and wettability of Sn–Zn–Al solders were measured as well.

Both, the ecological production and operation of vehicles demand using such materials for deformation zones' structural parts, which show some specific properties and use innovative technologies to process them. Specific requirements for functionality (strength, stiffness, deformation work, fatigue properties) are closely linked to processability (formability). In the paper are presented results for multiphase TRIP steel RAK40/70 when welded by pulse solid-state fiber laser YLS-5000. Based on microstructure analysis in the fusion zone and heat affected zone the welding parameters were optimised. The influence of laser welding on the strength and deformation properties was verified by characteristics of strength, stiffness and deformation work, as they were calculated from mechanical properties measured by tensile test and three-point bending test. The knowledge gathered in the field of laser welding influence on the strength and deformation properties of multiphase TRIP steel RAK40/70 should help designers when design the lightweight structural parts of the car body.

Thin films of erbium doped YbAG were prepared by spin-coating on fused silica substrates. The effect of two parameters on the microstructure of resulting films was observed: addition of a sintering agent (TEOS) to the solution deposited and crystallization under decreased atmosphere (100 mbar). All prepared samples were polycrystalline single phase YbAG. When comparing the reference (TEOS-free) samples crystallized in ambient pressure, the films with TEOS in a combination with decreased pressure during the crystallization had a smaller crystallite size and finer surface, as confirmed by AFM and Williamson–Hall analyses. A higher amount of TEOS caused cracking of the films though. All films containing TEOS were one-mode waveguides in the NIR region. This paper shows a way to modify microstructure of a waveguiding film via addition of a sintering agent without destroying the waveguiding ability.

At present, the number of optical cables in nuclear power plants has been increasing. Fiber optic cables are commonly used at nuclear power plants in instrumentation and control systems but they are usually used in environments without radiation. Nevertheless, currently, the number of applications in NPP containment with radiation is increasing. One of the most prevalent effects of radiation exposure is an increase of signal attenuation (signal loss). This is the result of fiber darkening due to radiation exposure and it is the main limitation factor in application of fiber optics in radiation environment. However, after the irradiation, the fiber optics go through a "recovery process" during which the optical properties improve again; i.e. attenuation decreases. However, we have found cable, where the expected healing process after few days changed its trend and the attenuation increased again to a value well above the attenuation just after the irradiation. This paper describes experiments that were carried out to explain this unusual recovery behaviour.

Kinetic equations are numerically solved within standard nucleation model to determine the size distribution of nuclei in small volumes near critical undercooling. Critical undercooling, when first nuclei are detected within the system, depends on the droplet volume. The size distribution of nuclei reaches the stationary value after some time delay and decreases with nucleus size. Only a certain maximum size of nuclei is reached in small volumes near critical undercooling. As a model system, we selected recently studied nucleation in Ni droplet [J. Bokeloh et al., Phys. Rev. Let. 107 (2011) 145701] due to available experimental and simulation data. However, using these data for sample masses from 23 μg up to 63 mg (corresponding to experiments) leads to the size distribution of nuclei, when no critical nuclei in Ni droplet are formed (the number of critical nuclei < 1). If one takes into account the size dependence of the interfacial energy, the size distribution of nuclei increases to reasonable values. In lower volumes (V ≤ 10^-9 m³) nucleus size reaches some maximum extreme size, which quickly increases with undercooling. Supercritical clusters continue their growth only if the number of critical nuclei is sufficiently high.

The positive effect of the hydrogen on hot deformation behaviour at 700 and 750 °C was investigated after thermal hydrogen treatment of Ti6Al4V and Ti26Nb alloys. Comparing the results obtained for the non-hydrogenated and hydrogenated specimens of both alloys, it was found that the hydrogen content as high as 1325 wt. ppm has an obvious benefit effect on high temperature deformation behaviour in the Ti6Al4V alloy by stabilizing beta phase and lowering thermal deformation resistance. In the case of Ti26Nb alloy the hydrogen content of 2572 wt. ppm suppressed stress instabilities during hot compression but slightly increased thermal deformation resistance. The microstructure study was performed before and after the isothermal compression tests on the specimens in hydrogenated as well as in non-hydrogenated condition. The hydrogen amounts in the specimens were measured by means of an analyser LECO RH600.

Superelastic behavior of off-stoichiometric NiTi alloys is significantly affected by microstructure changes due to heat treatment. Applying appropriate thermal treatments important effects on microstructural changes, transformation temperatures and thermomechanical properties of final NiTi products can be achieved. The experimental samples of NiTi alloy with 55.8 wt.% Ni were submitted to heat treatment and the microstructures before and after the treatment were observed. The thermal regimes consisted of annealing treatment at 600 °C for 1 hour followed by water quenching and of ageing at eight different temperatures (250, 270, 290, 300, 350, 400, 450 and 500 °C) for 30 minutes. Microstructure features studied by means of optical and scanning electron microscopies, EDX microanalyses, X-ray diffraction analyses and microhardness measurement, have shown that higher ageing temperatures led to microstructure changes and corresponding increase in microhardness.

The present work was focused on the properties of porous Ti6Al4V specimens processed by selective laser melting (SLM) and tested in tension and compression before and after heat treatment. The SLM samples were annealed at 955 °C, water quenched and aged at 600 °C with following air cooling. The values of the mechanical tests showed that the samples exhibited high mechanical properties. The anisotropy of tensile and compressive strength was observed, which was related to the occurrence of voids. The plastic properties of specimens were improved by means of the heat treatment that led to the transformation of martensitic to lamellar structure composed of α + β phases. The microstructure of SLM samples were evaluated before and after the heat treatment. The brittle nature of failures of non-heat treated samples can be explained by synergy of martensite presence, microcracks and residual stresses produced by SLM.

The development of composite materials and the related design and manufacturing technologies is one of the most important advances in the history of materials. Composites are multifunctional materials having unprecedented mechanical and physical properties that can be tailored to meet the requirements of a particular application. Ageing is also important and it is defined as the process of deterioration of engineering materials resulting from the combined effects of atmospheric radiation, heat, oxygen, water, micro-organisms and other atmospheric factors. The present article deals with monitoring the changes in the mechanical properties of composites with polymer matrix. The composite was formed from the PA matrix and glass fibers (GF). The composite contains 10, 20 and 30 % of glass fibers. The mechanical properties were evaluated on samples of the composite before and after UV radiation on the sample. Light microscopy was evaluated distribution of glass fibers in the polymer matrix and the presence of cracks caused by UV radiation.

LiNbO₃ co-doped with Er³⁺ and Yb³⁺ belongs among the most promising materials in photonics. In the form of thin films on a suitable substrate, it can be used as an active waveguide. Only few articles have been published concerning the deposition of such thin layers using a sol-gel method. Our aim was to test polyethylene glycol (PEG) as a watersoluble polymer in solutions to be deposited by spin-coating on sapphire substrates. Two heat treatment regimes were tested after single layers were deposited. Photoluminescence in a range of 1450–1650 nm was measured and the final films exhibited emission spectra with 6 local maxima. The deposited (Er³⁺/Yb³⁺):LiNbO₃ films were also characterized by m-line spectroscopy. In the NIR range, the films behaved as one-mode waveguides. This nonhydrolytic sol-gel method based on PEG thus represents one of few methods applicable in LiNbO₃ waveguiding films preparation.

Novel technique for identifying and quantification of local deformation phenomena in continuum model of grained solid structure is presented in this paper. We propose a method that combines deformation properties of structure with the changes of grains geometry deformed under the influence of local force. Experimental analyses of grains shapes subjected to a local force show a specific spatially oriented prolongation of grains in direction determined by applied force. However the volume of each grain is retained during the force application in case of plastic deformation. Character of individual grain prolongation depends on the initial shape of grain and direction of loading force. There is a definite relationship between the change in grain shape and nature of the driving deformation force. We contribute to the revealing of mentioned relationship because of we propose and analyze a method for quantification of the effect of grain shape modification on the basis of grain deformation. Quantitative analysis of local deformation in grained structure can be realized in a perspective using mentioned method. Map of local deformation data in grained system can be constructed in this way and next the local deformation dynamics analysis can be performed. However precision of mentioned analysis must be proven by evaluating of its practical predictive performance in future.

Nowadays, the laser technology is used in a wide spectrum of applications, especially in engineering, electronics, medicine, automotive, aeronautic or military industries. In the field of mechanical engineering, the laser technology reaches the biggest increase in the automotive industry, mainly due to the introduction of automation utilizing 5-axial movements. Modelling and numerical simulation of laser welding processes has been exploited with many advantages for the investigation of physical principles and complex phenomena connected with this joining technology. The paper is focused on the application of numerical simulation to the design of welding parameters for the circumferential laser welding of thin-walled exhaust pipes from theAISI 304 steel for automotive industry. Using the developed and experimentally verified simulation model for laser welding of tubes, the influence of welding parameters including the laser velocity from 30 mm.s⁻¹ to 60 mm.s⁻¹ and the laser power from 500 W to 1200 W on the temperature fields and dimensions of fusion zone was investigated using the program code ANSYS. Based on obtained results, the welding schedule for the laser beam welding of thin-walled tubes from the AISI 304 steel was suggested.

The sustainable development consists of the effort of replacing commonly used polymer materials for the biodegradable ones. They do not have sufficient physical and mechanical properties, therefore they have to be modified by producing various ratio mixtures or with the additives. Improving their processability and properties is an important challenge to be afforded before using these materials on the market. One way to improve the properties of these materials is to prepare their blends [1]. The most common way of the preparation of packaging materials is the injection moulding, where the crystallization of material is very important. That is the reason the crystallization has become one of the most studied characteristics of biodegradable blends based on PLA / PHB. The work is a contribution to works that deal with the description of the structure of PLA / PHB blends, which have been modified by the addition of various types of additives, mainly nucleating agents and plasticizers [2]. The films of these blends keep approximately unchanged mechanical properties after two weeks of storage. The presence of plasticizer (ATBC) and nucleating agent (BN) has no significant impact on the processing stability of PLA/PHB blends. The results show that the combination of the plasticizer and nucleating agent greatly affects the process of crystallization of PLA/PHB blends as well as the ratio of polymers and the heat treatment process.

The paper deals with the numerical modelling and simulation of loads arising during the milling process and their impact on the deformations and stresses developed in the frame of construction of hobby milling machine. Based on the prepared simulation model, the loads during the machining with feed rates in different directions were considered in order to find out the critical loading and its influence on the machine frame deformation. The impact of the frame deformations on the displacement of a tip of the tool, and thus the accuracy of the machining process was evaluated. Results of initial numerical simulations provided also the information about the components of the construction that need to be modified during the optimization of the designed construction and/or the development of a new prototype.

Due to suitable mechanical properties, satisfactory corrosion resistance and relatively low cost, austenitic stainless steels are important biomaterials for manufacture of implants and various medical instruments and devices. Their corrosion properties and biocompatibility are significantly affected by protective passive surface film quality, which depends on used mechanical and chemical surface treatment. This article deals with corrosion resistance of AISI 316L stainless steel, which is the most widely used Cr-Ni-Mo austenitic biomaterial. Corrosion behaviour of five various surfaces (original, electropolished, three surfaces with combined treatment finished by electropolishing) is evaluated on the bases of cyclic potentiodynamic polarization tests performed in physiological solution at the temperature of 37± 0.5 °C.