Microstructure And Properties Of SiC Particles Reinforced Al-Si Composite Solidified Under High Pressure

Silicon carbide particle reinforced aluminum-silicon composites are not only high-strength,wear-resistant,low-expansion,excellent electrical and thermal conductivity,but also have good casting properties,and have broad application prospects in automotive manufacturing,military technology,aerospace industry and microelectronics packaging.The thermodynamic and kinetic states of alloy solidification under high pressure conditions will be greatly affected,and the phase composition and microscopic morphology of the composite will change accordingly.In this paper,SiCp/Al-Si composites were fabricated on Al-Si alloys using sub-micron Si C particles with a size of 500 nm and a volume fraction of 20 vol.%.Different pressures(1GPa,2GPa,3GPa)and different Al-Si matrix(Al-20 Si,Al-30 Si,Al-40 Si,Al-50Si)on the microstructure and composition phase of SiCp/Al-Si composites.When SiCp/Al-20 Si composite material is solidified at 1 GPa pressure,the solid solubility of Si in Al is 0.34%.When solidified at 3 GPa pressure,the solid solubility of Si in Al is 7.82%.With the increase of pressure,Si is more and more dissolved in Al,replacing the Al atoms to form a substitutional solid solution.The diffraction peak of the Al phase in the XRD pattern moves to a high angle as the pressure increases.The 1GPa pressure solidification structure contains more spherical primary crystal Silicon.After solidification at 2GPa,there is less primary crystal Silicon and the surface is facet.After the 3GPa solidification,primary crystal silicon is no longer present.After artificial aging of SiCp/Al-20 Si composites under high pressure solidification,Si precipitates out of high-pressure solidified Al(Si)supersaturated solid solutions.The size of the precipitated phase after 3 GPa solidified composites was larger than that of 1 GPa precipitated after solidification.The diffraction peak intensity of the Al phase after aging is decreased,and the diffraction peak of the Al phase is shifted to a low angle,and the intensity of the diffraction peak of the Si phase is increased as compared with that before aging.The density and mechanical properties of the composites after high pressure solidification show that the density increases with the increase of solidification pressure.The density of SiCp/Al-20 Si composites increases from 97.1% at 1 GPa pressure solidification to.98.6% under 3 GPa pressure solidification.Under the same solidification pressure,as the Si content of the matrix alloy increases,the density increases and the hardness increases.Due to the higher density and solid solubility obtained under high pressure,the composite material with the same composition will increase in hardness as the solidification pressure increases.After 3GPa solidification,the compression performance of 3GPa of SiCp/Al-20 Si composites is better,and thecompressive strength is improved by 27% and 25% respectively compared with 1GPa and 2GPa.With the increase of Si content in the matrix,the hardness and compressive strength of the composites solidified under the same pressure increase.When 2GPa and 3GPa high pressure solidified Al-20 Si matrix composites were aged at 160°C for 6 hours aging,the compressive strength was increased from 571 MPa and 714 MPa to 598 MPa and 750 MPa,respectively.