Microstructure And Properties Of High Pressure Solidified Double-scale SiC_p Particles Reinforced Al-20Si Composites

SiC_p particle reinforced aluminum matrix composites have the characteristics of light weight,high thermal conductivity,low thermal expansion coefficient,high hardness,high wear resistance and corrosion resistance,which make it have important application value in the field of electronic packaging.GPa-grade high-pressure solidification technology can significantly change the solidification behavior of materials,affecting the structure of materials and affecting the properties of materials.There are huge differences in the mechanism and effect of micron-sized and nano-sized particles on the microstructure and properties of materials.In this paper,SiC_p particle reinforced Al-20Si composites were studied.The coagulation pressure(1GPa,2GPa,3GPa),and 80?m+30nm biscale SiC_p particle components were studied:{[15%?m+(0%,2%,3%,4%)nm],[(0%,10%,15%,20%]+3%}on the solidification microstructure and phase composition of the composite and the mechanical properties and thermal properties of the composite The law of influence of performance.The microstructure of the composites solidified under different pressures shows that the primary phase is primary Si when the pressure is 1,2GPa,and its size decreases with the increase of solidification pressure.When the pressure is 3GPa,the primary phase changes into dendritic?-Al.As the solidification pressure increases,the eutectic Si gradually refines and the morphology changes from long needle to short rod.With the increase of micron-sized SiC_p content,the volume fraction and size of primary Si increase,the size of primary?-Al decreases,and the branching phenomenon of eutectic Si increases.With the increase of nano-scale SiC_p particles,the initial The size of the crystalline Si is reduced,and the fineness of the eutectic Si is increased,and the distribution is more continuous.The mechanical properties of the composites show that the density of the composites increases with the increase of solidification pressure.Under the same solidification pressure,the density of the materials decreases with the increase of the content of micro-particles.Ascending and rising.The solidification structure of the material is refined and the primary phase changes under high pressure.The hardness,strength and plasticity of the composite increase with the increase of solidification pressure.The hardness and flexural strength of the composites with 3GPa coagulation pressure(15%+3%)increased by 142%and 79%,respectively,compared with 1GPa.Under the same solidification pressure,the hardness and flexural strength of the composites increased with the increase of the content of micron SiC_p particles,and the plasticity became smaller.With the increase of the content of nano-SiC_p particles,the hardness and plasticity of the composites increased,and the bending strength did not change significantly.At 3GPa,(20%+3%)material obtained a maximum hardness of285.4,(15%+2%)material obtained the maximum bending strength of 424.85MPa and the highest plasticity.The effects of coagulation pressure and dual-scale particle composition on the thermal properties of SiC_p/Al-20Si composites were also investigated.The coefficient of thermal expansion of the material in the interval from room temperature to 180°C decreases as the solidification pressure increases.Above 180°C,due to the precipitation of Si,the coefficient of thermal expansion will have a peak in the range of 232°C-300°C.The higher the solidification pressure,the lower the peak corresponding temperature and the larger the peak value.The solidification pressure increases the interfacial force and dislocation,and enhances the scattering of electrons and phonons.The thermal conductivity of the material decreases with the increase of the solidification pressure.When the solidification pressure is 3GPa,the content of micron SiC_p particles increases.The coefficient of thermal expansion decreases,and the thermal conductivity decreases.As the content of nano-SiC_p particles increases,the thermal expansion coefficient increases slightly and the thermal conductivity increases.