Effect of full melt temperature sintering and semi-melt heat preservation sintering on microstructure and mechanical properties of Ti3SiC2/Cu composites

The influence of sintering parameters on the microstructure, phase composition and mechanical property of the Ti3SiC2/Cu composites sintered by spark plasma sintering technique was investigated and the related sintering mechanism was clarified in detail. Results indicated that during the heating process, one part of the high energy adsorbed by the composites let Cu melt and fill the gaps inside the composites. Meanwhile, there’s different molten condition about Cu duel to different heating temperature that cause Cu fill in the most space between Ti3SiC2 particles. The other part of the energy caused to the local high temperature, contributing for the chemical reaction and the formation of TiCx and Cu3Si. Therefore, at the same heating rate, the composites showed better mechanical property and higher density with a longer heating time. The heating stage played an important role in the change of the mechanical property, microstructure and volume of the composites. During the holding stage, because the amount of the reactants significantly decreased, the related chemical reaction got slow and the energy needed during this stage was lower than that during the heating stage. And the particle of Ti3SiC2 need more time for moving to the space of Cu. Therefore, the higher the holding temperature, the more significant was the diffusion of the phases. The more uniform the phases, the higher was the density. When heating temperature (higher than holding temperature) cause Cu complete melt and holding temperature keep the Cu in semi-melt, there will be a more effective sintering method.


Introduction
Ti 3 SiC 2 was a ternary layered compound.Its layered crystal structure and high temperature resistance endowed it good high temperature tribological property [1,2], good machinability, mechanical property and chemical stability, making it widely used in industry [3].However, Ti 3 SiC 2 polycrystalline block samples were prepared by reactive hot-pressing method at 40 MPa and 1600 °C.The compressive strength of Ti 3 SiC 2 was 600 MPa at room temperature, which decreased to 260 MPa at air temperature of 1300 °C, and the hardness was 4 GPa [4].Although the high temperature-load curve has significant plastic behavior, the failure at room temperature is still brittle.As a solid lubrication composite material, the strength and hardness of Ti 3 SiC 2 need to be further improved.
In the process optimization of additive manufacturing, the microstructure, residual stress and density uniformity of the part are controlled by establishing a model and adjusting the preparation parameters, which involve phase transitions between powder, liquid and block [5,6].This method by adjusting the preparation parameters and establishing the model provides a reference for improving the tribological properties of Ti 3 SiC 2 .Recent years, researchers attempted to prepare Ti 3 SiC 2 based composites by adding an enhanced phase.Benamor et al [7] investigated the effect of adding enhanced phases or solid lubricants on the high temperature tribological behavior of Ti 3 SiC 2 and they improved the tribological property by optimizing the composition and preparation process.The sintering processes and the related sintering mechanisms of the Ti 3 SiC 2 based composites were widely studied [8][9][10][11][12][13][14].Zhou et al [15] studied the chemical reaction and temperature during the preparation of the Ti 3 SiC 2 based composites.The results indicated that the preparation process and the related chemical reactions significantly affected the property of the as-synthesized composites.Chen et al [16] investigated the chemical reactions and atomic diffusion between Ti 3 SiC 2 and the enhanced phase, and they found that the decomposition of Ti 3 SiC 2 and the diffusion of Si atoms played an important role in the combination of the composites.Due to the improvement of the property of the composites by adding enhanced phases, the as-obtained composites had good industrial applications [17][18][19].Thus, it can be seen that the purpose of changing phase and increasing mechanical properties can be achieved by adding reinforcement phase and regulating sintering parameters, which makes the original excellent tribological properties of Ti 3 SiC 2 better applied to more complex environments.
Based on the good tribological property, high temperature resistance and resistant to thermal shock of Ti 3 SiC 2 , researchers tried to explore the friction and wear behavior of Ti 3 SiC 2 in high temperature by adding enhanced phases [20][21][22][23][24]. Dang et al [25] investigated the tribological and mechanical properties of Ti 3 SiC 2 /Cu composites.They discovered that the friction coefficient and wear rate of the composites were lower than that of Ti 3 SiC 2 , which was attributed to the fixing effect of the hard TiC x , Ti 5 Si 3 C y and Cu 3 Si, suppressing the abrasive friction and wear.However, at higher temperatures (from room temperature to 600 °C), the friction coefficient and wear rate of the composites were higher than that at room temperature.It was thought that plastic flow and tribo-oxidation wear accompanied by material transfer, caused to the higher friction and wear at high temperatures.Zhang et al [26] investigated the microstructure, mechanical property and tribological behaviors of Ti 3 SiC 2 /Cu composites (TSC-Cu).They found that the TSC-Cu was composed of Ti 3 SiC 2 , TiC and Cu 3 Si, and Cu 3 Si uniformly distributed along the grain boundary of Ti 3 SiC 2 .The addition of Cu improved the hardness and compressive strength of TSC-Cu, but it's the flexural strength is decreased.Moreover, in comparison with polycrystalline Ti 3 SiC 2 , the average friction coefficient of TSC-Cu at 25 °C-400 °C was higher but it was lower at 600 °C-800 °C.It was suggested that the synergistic lubrication of the tribo-oxidation film containing TiO 2 , SiO 2 and CuO was beneficial for its low friction.Additionally, the wear rate of TSC-Cu was significantly lower than that of polycrystalline Ti 3 SiC 2 , which was owing to the surface strengthening of the as-formed hard TiC product.Although Cu has been widely studied as a strengthening phase, how to effectively improve the diffusion uniformity of Cu, reduce the porosity and the internal change mechanism of Cu in different sintering stage need to be further elaborated.
The sintering parameters and different sintering stages directly affected the microstructure and property of materials.On the other hand, the friction and wear behavior of materials had a direct relationship with its microstructure, sintering method and property.In order to prepare the Ti 3 SiC 2 /Cu composites and adjust its property, it was necessary to know the controlled parameters and the related physical and chemical changes during the preparation of Ti 3 SiC 2 /Cu composites [26,27].By adding the soft metal Cu into Ti 3 SiC 2 was demonstrated as an effective way to improve the relative density, hardness and compressive strength of Ti 3 SiC 2 .Thus, the wear resistance of the Ti 3 SiC 2 /Cu composites was expected to be higher than that of polycrystalline Ti 3 SiC 2 .Zhang et al explored the change of the axial dimension of Ti 3 SiC 2 /Cu composites during the preparation by SPS technique and they discovered that the heating stage and the holding stage obviously affected the axial dimension of the composites [28].To reveal the effect of these two stages on the physical and chemical changes of the composites, the heating stage and holding stage were separately investigated in this study.Moreover, the effect of these two stages on the microstructure, phase composition and mechanical property of the composites was investigated, and the related sintering mechanism was discussed.It is of great significance to obtain the mechanism of different sintering stages to improve the sintering efficiency, improve or regulate the mechanical properties and microstructure of sintered materials.

Experiment
2.1.Samples preparation Ti 3 SiC 2 /Cu composites were synthesized by using powder mixture of Ti 3 SiC 2 (average particle size: 38 μm, 98% purity, 11 technology Co., Ltd, Jilin, China) and Cu (average particle size: 74 μm, 99.9% purity, Macklin Biochemical Co., Ltd, Shanghai, China).The SEM results of the original powders of Ti 3 SiC 2 and Cu are shown in figure 1.The volume fracture of Cu in the composites was 15%.The mixture was mixed by a ball-milling machine (PMQD2LB, Nanjing Chishun Technology Development Co., Ltd, Nanjing, China) with a rotational speed of 150 rpm and a ratio of ball to powder of 3 for 6 h.Then the mixture was loaded into a graphite mold with an outer diameter of f70 mm × 50 mm and an inner diameter of f25 mm × 50 mm.Finally, the samples were sintered by a spark plasma sintering (SPS, Model Labox-350, Xinxie, Japan) system under a pressure of 35 MPa in vacuum.The sintering temperature was analyzed by an infrared thermometer attached to the SPS system and automatically recorded since 570 °C.As shown in figure 2, the sintering process of the composites was proceeded in two modes (mode1 and mode 2).In mode 1 (see figure 2(a)), the composites were obtained by heating to different sintering temperatures (T 1 -T 3 ) at a heating rate of 50 °C min −1 and then directly cooling with the furnace.In mode 2 (see figure 2(b)), the composites were synthesized by heating to 1050 °C (When the temperature rises to 1050 °C, the Cu begins to overflow) at a heating rate of 50 °C min −1 , then holding at different temperatures (T 4 -T 6 ) for 20 min and finally cooling with the furnace.

Mechanical property
The relative density of the as-obtained composites was determined by Archimedes' method.The Vicker hardness of the composites was analyzed in a MHVD-50AP microhardness tester (Shanghai Jujing Precision Instrument Manufacturing Co., Ltd, Shanghai, China) at a load of 1 kg with a dwell time of 10 s.The compressive strength of the composites was conducted on a WDW-100 universal materials testing machine (Jinan Hansen Precision Instrument Co., Ltd, Jinan, China) using cylinder specimens with a size of f4 mm × 10 mm at a loading speed of 0.2 kN s −1 .Detailed parameters of compressive testing with respective labeling are shown in table 1.

Analysis
The as-synthesized Ti 3 SiC 2 /Cu composites were polished using 0.5 um polishing paste by an automatic polishing machine (AutoMetTM 250, Yigong Testing and Measuring Instrument Co., Ltd Shanghai, China) for microscopic evaluation.In order to expose the grains, the polished samples were etched using a 1:1:1 by volume HF: HNO 3 : H 2 O solution and observed under optical microscopy (MDJ-DM, Chongqing Auto Optical  Instrument Co., Ltd, Chongqing, China).The microstructure and compression fracture morphology of Ti 3 SiC 2 /Cu composites was observed by scanning electron microscopy (SEM, JSM-6510LA, JEOL Japan Electronics Co., Ltd, Zhaodao, Japan) equipped with energy dispersive spectroscopy (EDS).X-ray diffraction (XRD) analysis was carried out on a DX-2700B diffractometer (Dandong Haoyuan Instrument Co., Ltd, Dandong, China) with Cu Kα radiation at a scanning rate of 4.8°min −1 to identify the phase composition of Ti 3 SiC 2 /Cu composites.

. Phase composition and microstructure
The XRD patterns of the Ti 3 SiC 2 /Cu composites synthesized in mode 1 were shown in figure 3. The result showed that the intensity of the diffraction peaks of the composites changed but its phase composition was identical.Before the mixed powder sintering, the phase composition consists of the mixed powder contains only Ti 3 SiC 2 and Cu.When the sintering temperature was 950 °C, the phase composition of the composites was apparently different from that of the original powder.As seen in figure 3, a new phase, Cu 3 Si, appeared.According to the sintering characteristic of SPS, it was inferred that when the sintering temperature was 950 °C, phase transformation happened in the local area of the particles.Thus, the melting of Cu and the diffusion of Si occurred, and the reaction of Cu and Si formed Cu 3 Si.According to the change of the intensity of the diffraction peak of the composites, the formation of new phase was accompanied with the growth of crystals and the lattice distortion of the original phase.It was speculated that with the increase of the heating time, high-energy arc led to the local melting inside the composites and surface activation of the original Ti 3 SiC 2 powder.The Si atoms continuously migrated to the melting Cu, and Ti 3 SiC 2 underwent lattice distortion and finally decomposed.
The microstructure of the Ti 3 SiC 2 /Cu composites obtained in mode 1 was shown in figure 4. As seen in figure 4 and table 2, the pore area ratio of the as-synthesized composites was affected by the sintering temperature if the heating rate was equal.The higher the sintering temperature, the smaller the pore area ratio of the composites were.According to the figure 5 and table 2, the irregular spreading area of light color is Cu.When the sintering temperature was 950 °C, the agglomeration of Cu inside the composites was obvious (see figure 4(d)).With the increase of the sintering temperature, the agglomeration of Cu was decreased, and the diffusion range and uniformity of Cu increased (see insert figure of figures 4(d)-(f)).When the sintering temperature was 1000 °C and 1050 °C, the agglomeration of Cu disappeared, and Cu was uniformly distributed  (see figures 4(e) and (f)).Thus, it was thought that when the sintering temperature was higher, the agglomeration of Cu was inhibited.On the other hand, the result indicates that the higher sintering temperature was favorable for the diffusion and the uniform distribution of Cu.Therefore, it was concluded that the sintering temperature significantly affected the porosity and the distribution of the second phase of the composites.The mapping of elemental distribution of the Ti 3 SiC 2 /Cu composites obtained in mode 1 was shown in figure 5.It was seen from figure 5 that both Ti and Cu were independently distributed in the composites.Si distributed in the same area with Ti and Cu.Moreover, the figure 5 shows that the content of Si distributing in the area of Ti was brighter and there was obvious difference in the content of Si distributing in the area of Ti.Si was relatively uniformly distributed in Cu.Al was originated from the raw mixture of Ti 3 SiC 2 .It was indicated that the diffusion of atoms and the related chemical reaction occurred during the heating process.

Sintering behaviors of the as-synthesized composites obtained in mode 1
In order to observe the sintering changes of materials more directly, the sintering parameters of Ti 3 SiC 2 /Cu composites obtained in mode 1 can be seen in figure 6.In the beginning, the axial dimension of the composites fluctuated, which was owing to the effect of high-energy arc releasing by the sintering system.The powder granules were rapidly heated by high-energy arc in the touchpoint.When the temperature reached 800 °C, the axial dimension of the composites showed a monotonical decreasing tendency and its fluctuation was not obvious, which resulted from the melting and flowing of Cu due to high temperature and high-energy arc.It was indicated that the change of material organization was significant during the heating process.Additionally, the axial dimension of the composites was not positive or negative correlation with the change of temperature.Simultaneously, peaks of current and voltage fluctuations were identical with these of axial dimension.Therefore, it was deduced that the macro size of the composites was influenced by the sintering temperature and the major factors included the temperature, the current, the voltage, and the related physical and chemical changes.The higher ending temperature, obviously, make higher melting extent of Cu causing different mobility.

Mechanical property of the composites obtained in mode 1
The relative density and hardness of the as-synthesized composites obtained in mode 1 were shown in figure 7. It was seen from figure 7 that with the increase of the sintering temperature, the relative density of the composites increased.Specifically, when the sintering temperatures were 950 °C and 1000 °C, the relative density of the composites was about 95%.When the sintering temperature was 1050 °C, the relative density of the composites was higher and reached 99%.It was guessed that higher temperature was beneficial for increasing the relative density of the composites.According to the density formula , m V ( ) r = the density of the materials relied on the mass and the volume.If the mass was constant, the density was not linear to the volume, indicating that the relative density of the material was not only affected by the variation of porosity, but also depended on the change of the volume due to the changing of the phase composition during the heating process.With the increase of the sintering temperature from 950 °C to 1050 °C, the hardness of the composites evidently increased from 2.8 GPa to 9.12 GPa.It was thought that both the phase composition of the composites and the binding strength of these phases significantly changed.

Sintering with a holding stage 3.2.1. Phase composition and microstructure
The XRD patterns of the Ti 3 SiC 2 /Cu composites synthesized in mode 2 were shown in figure 8. Before the mixed powder sintering, the phase composition consists of the mixed powder contains only Ti 3 SiC 2 and Cu.As seen in figure 8, when the composites were holding at different temperatures, the phase composition was identical.Interestingly, the intensity of the diffraction peak at 45°of the composites obtained by holding at 1050 °C for 20 min was clearly different from that of the composites obtained by holding at 950 °C and 1000 °C for 20 min.Compared the XRD results of the composites obtained in mode 1 (see figure 3) and mode 2 (see 8), it was demonstrated that the phase composition of the composites obtained in mode 2 was relatively stable.Therefore, it was speculated that during the holding stage, the phase composition of the composites did not obviously change, but the content of the existed phases varied and a densification process occurred.
The microstructure of the Ti 3 SiC 2 /Cu composites obtained in mode 2 was shown in figure 9.It was clearly seen from figure 9 and table 3 that all the pores area ratio were almost the same for all the composites obtained in mode 2. It was indicated that the physical change of the composites was not obvious during the holding stage.The distribution of Cu was relatively uniform and there was no obvious agglomeration of Cu.Therefore, it was concluded that the holding stage took a little part in the diffusion and the composition of phases.
The mapping of elemental distribution of the Ti 3 SiC 2 /Cu composites obtained in mode 2 was shown in figure 10.It was seen from figure 10 and table 3 that the distribution of Cu was relatively uniform and there was no obvious agglomeration of Cu at different holding temperatures.The mapping of elemental distribution of the Ti 3 SiC 2 /Cu composites obtained in mode 1 and mode 2 are similar.Specifically, both Ti and Cu were independently distributed in the composites.Si distributed in the same area with Ti and Cu.Moreover, the content of Si distributing in the area of Ti was brighter than Cu and there was obvious difference in the content of Si distributing in the different area of Ti.Si was relatively uniformly distributed in Cu.Al was originated from the raw mixture of Ti 3 SiC 2 .It was indicated that substance transfer occurred during the heating stage, which  originated from the diffusion and the related chemical reaction of Si atoms in Cu, and the reaction between occurred Ti 3 SiC 2 and adjacent Ti 3 C 2 skeleton during the heating process.During the holding stage, the diffusion of Cu was not obvious and it was relatively uniformly distributed in the composites.

Sintering behaviors of the as-synthesized composites obtained in mode 2
The sintering parameters of Ti 3 SiC 2 /Cu composites obtained in mode 2 was seen in figure 11.As seen in figure 11, the change of the axial dimension increased with the increase of the holding temperature in mode 2. At the same sintering temperature, the change of the axial dimension of the composites was almost the same (see figure 11(d)).Moreover, the change of the axial dimension of the composites increased with the increase of the holding temperature (see figure 11(d)).In comparison, the change of the axial dimension of the composites during the holding stage was lower than that during the heating stage.Thus, it was thought that during the  Table 3. Pore area ratio and elements atomic ratio of Ti 3 SiC 2 /Cu composites in sintering mode II.

Final temperature of sintering mode 2
The pore area ratio in figure 9 The proportion of each element in figure 10 950(a) 0.0155 32.4%Ti, 13.5Si%, 29.3C%, 13.5Cu%, 8.3O%, 3.0Al% 1000(b) 0.0114 34.0%Ti, 13.4Si%, 28.9C%, 11.9Cu%, 8.9O%, 2.9Al% 1050(c) 0.0183 35.4%Ti, 13.6Si%, 29.7C%, 10.4Cu%, 8.0O%, 2.9Al% sintering of the composites, the axial shrinkage occurred both in the heating stage and in the holding stage and it was significantly affected by the heating stage.Additionally, the change of the axial dimension during the holding stage decreased with time (see figures 11(a)-(c)).When the temperature and the current were steady, the physical and chemical change got slow and slow, which indicated that the filling of the pores of the composites tended to be saturated.It was worth noting that the axial shrinkage of the composites during the heating stage was higher than that of the composites during the holding stage if the sintering temperature was lower than the holding temperature and the heating time was shorter than the holding time.Considering that the current and the temperature were the main parameters in this study, it was deduced that the current took an important part in the heating process.Additionally, the work from the current during the heating process must be higher than the energy loss during the sintering process, which indicated that the accumulation of internal energy occurred during the sintering of the composites, facilitating the chemical reactions between constituents.This explained to a certain extent that the change of the phase composition during the heating stage was apparent than that during the holding stage.

Mechanical property of the composites obtained in mode 2
The relative density, compressive strength and hardness of the as-synthesized composites obtained in mode 2 were shown in figure 12.There was no obvious difference between the relative density of the as-synthesized composites obtained in mode 2. Among them, the composites obtained by holding at 1050 °C for 20 min exhibited the highest relative density (about 97.34%).As for the compressive strength, with the increase of the holding temperature, the compressive strength of the composites increased, and the composites obtained by holding at 1050 °C for 20 min showed the highest compressive strength of 1950 MPa.There was also no obvious difference between the hardness of the as-synthesized composites obtained in mode 2. Among them, the composites obtained by holding at 1050 °C for 20 min exhibited the highest hardness about 9.21 GPa.Conclusively, the relative density, compressive strength and hardness of the composites showed an upward trend with the increase of the holding temperature.The relative density and hardness of the composites obtained by holding at 1000 °C for 20 min were lowest among three composites.The fluctuation of the mechanical property of the composites obtained by holding at 1000 °C for 20 min was attributed to the following factors.On one hand, the agglomeration of Ti 3 SiC 2 at 1000 °C was weaker than that at 950 °C.Simultaneously, the melting of Cu at 1000 °C was stronger than that at 950 °C and the diffusion of Cu was limited.On the other hand, the testing area of the hardness testing was too small.Thus, the distribution of different phases and their difference in hardness led to the fluctuation of their mechanical property.
The compressive fracture morphology of the as-synthesized composites in mode 2 was shown in figure 13.As seen in figure 13, the main fracture characteristics included textured transgranular fracture (1), Ti 3 SiC 2 grain pull-out (2), planar transgranular fracture (3), convex transgranular fracture (4) and intergranular fracture (5).The appearance of the transgranular fracture was originated from the following reason.The composites were subjected to the shear effect from the surrounding grains, thus the Ti 3 SiC 2 grains fractured along its normal direction of the plane.Moreover, the main component of the composites was Ti 3 SiC 2 grains and some of these grains were easily agglomerated together with limited binding strength.When the force was applied on the composites, the interface of these grains was extremely easy to separate, forming the intergranular fracture.

The sintering mechanism of the as-synthesized composites
As shown in figure 14, during the heating stage, high-energy arc was formed due to the pulsed current and worked at the point of contact of powders.The surface of Cu and the contact parts between Cu and Ti 3 SiC 2 locally melted due to the high-energy arc.The melting Cu was extruded into the gaps between Ti 3 SiC 2 grains, leading to the axial shrinkage of the composites.In the meantime, the Si atoms inside Ti 3 SiC 2 grains diffused into Cu and reacted with it at a certain temperature.Additionally, the diffusion of Si atoms on the surface of Ti 3 SiC 2 particles caused to the distortion of lattice, leading to the increase of its atomic strain energy.Therefore, the Ti 3 C 2 skeleton forms TiC x .During the heating stage, the pulsed current was large and Cu inside the composites aggregated together.Under the strong effect of high-energy arc, Cu rapidly melted and filled into the gaps during the heating stage.Thus, a rapid axial shrinkage of the composites occurred during the heating stage.Additionally, at different heating temperatures, the porosity and agglomeration of the composites varied.Duel to different ending temperature (950 °C, 1000 °C, 1050 °C), there is different melting extent of Cu causing different mobility for filling the hole between Ti 3 SiC 2 particle.
The work of the pulsed current during the holding stage was stable and lower than that of the pulsed current during the heating stage.Moreover, Cu diffused to more area and the contact area of Cu and was Ti 3 SiC 2 larger.The above reasons contributed to the lower melting rate and deformation efficiency of Cu during the holding stage, reducing the rate of the axial shrinkage.Additionally, Cu reacted with a large amount of Si atoms during the holding stage.However, Si atoms in Ti 3 SiC 2 grains decreased and Ti 3 SiC 2 grains decomposed into TiC x .Thus, the diffusion and reaction rate of Cu and Si substantially decreased.Meanwhile, the high temperature during the holding stage was benefit for the uniform distribution of the phase composition of the composites.Pressure and appropriate holding temperature supply such a condition for the Ti 3 SiC 2 particle moving to the space of molten Cu by enough time holding time.

Conclusions
Ti 3 SiC 2 /Cu composites were synthesized by spark plasma sintering technique and the effect of the heating stage and the holding stage on the microstructure, phase composition and mechanical property of the as-obtained composites was investigated.Additionally, the sintering mechanism of the as-synthesized composites was proposed.The results indicated that the heating stage took an important part in the microstructure and microstructure of the composites while the holding stage was benefit for the densification of the composites.The fracture mode of the as-synthesized composites included transgranular fracture and intergranular fracture.As a main part of sintering process, increasing the ending temperature of the heating stage to a temperature higher than the holding stage will effectively improve the sintering efficiency for relative density, compression strength, homogeneity and hardness.

Figure 3 .
Figure 3. XRD patterns of Ti 3 SiC 2 /Cu composites and mixed powder of Ti 3 SiC 2 &Cu obtained in mode 1.

Figure 7 .
Figure 7. Relative density and hardness of Ti 3 SiC 2 /Cu composites obtained in mode 1.

Figure 8 .
Figure 8. XRD patterns of Ti 3 SiC 2 /Cu composites and mixed powder of Ti 3 SiC 2 &Cu obtained in mode 2.

Figure 11 .
Figure 11.The variation of the sintering parameters (including current, temperature and axial dimension) of Ti 3 SiC 2 /Cu composites obtained in mode 2 with time: (a) at 950 °C, (b) at 1000 °C, (c) at 1050 °C, and (d) the variation of axial shrinkage with temperature during the heating and holding stages.

Figure 12 .
Figure 12.Relative density, compressive strength and hardness of Ti 3 SiC 2 /Cu composites obtained in mode 2.

Table 2 .
Pore area ratio and elements atomic ratio of Ti 3 SiC 2 /Cu composites in sintering mode I.