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The coefficient of thermal expansion and thermal strain response behaviour of SiCp/Cu composites prepared by spark plasma sintering (SPS) and pressureless infiltration were studied. The CTEs decreased with increasing reinforcement content. For a fixed SiC content, pressurelessly infiltrated specimens exhibited lower CTE than the SPS specimens. The CTEs of SPS specimens agreed well with the ROM model while the CTE of pressurelessly infiltrated specimens was close to Kerner's predictions. The strain hysteresis loops were developed during thermal cycling. The residual stress increased with increasing reinforcement content. The SPS specimens experienced large dimensional change due to the weak interfacial bond while the pressurelessly infiltrated specimens showed negligible strain hysteresis. The interfacial condition has a pronounced effect on the strain hysteresis behaviour. The improved interfacial bond was beneficial to the decreasing of the CTE and improving the dimensional stability of the composite. [ABSTRACT FROM AUTHOR]

The mechanical alloying (MA) is a non-equilibrium powder processing technology and has been applied to many systems, including amorphous alloys, extended solid solutions, metastable crystalline phase and nanocrystalline materials. In this study, the microstructural evolution and phase transformation of W:2Si powder prepared by MA were investigated by XRD and SEM. The results showed that the supersaturated W(Si) solid solution was formed in succession as the intermediate products of MA of W/Si mixture. Then, a mixture of WSi2 microcrystallites and supersaturated W(Si) solid solution was observed. The final product was amorphous WSi2. The total energy of W:2Si powder mixture was raised by MA; thus crystalline WSi2 can be obtained by heat treatment of as milled W(Si) solid solution powder or amorphous WSi2 powder. The formation mechanism of WSi2 during MA was an atomic diffusion process. WSi2 can be synthesised more easily by filling the vial with one-third fill rather than two-third fill. [ABSTRACT FROM AUTHOR]

SiCp/Cu composites with high reinforcement content (56–65 vol.-%) were fabricated by spontaneously infiltrating copper alloy into porous SiC preform obtained by powder injection moulding. The main influencing factors of the preparation of the preform and the infiltration behaviour of various preforms were studied. The results indicate that the viscosity increases with an increase in powder loading or decreases with an increase in particle size. The feedstocks with bimodal mixture exhibit low viscosity due to the improvement in packing efficiency. When small particles or bimodal mixture with large size ratio were used, the preforms were difficult to be fully infiltrated. The preforms debound in air exhibit lower infiltration rate than the ones debound in vacuum due to the reduction of porosity and the poor wettability between the oxidised layer and copper alloy. Kinetic analysis on the infiltration curves yielded activation energies of 253 kJ mol–1. [ABSTRACT FROM AUTHOR]