Particle Breakage,Mechanical And Thermal Properties Of SiC_p/Al Matrix Composites Prepared By High Pressure Torsion

With high modulus,high strength,high thermal conductivity,low expansion performance,SiCP/Al composites have been widely used in aerospace,transportation,electronic packaging and other fields,but SiCP/Al matrix composites prepared by traditional methods have some disadvantages such as non-uniform microstructure,poor interfacial bonding,so secondary operation are necessary.SiC particles and Al powder can be directly consolidated into bulk SiCP/Al composites that have high properties by high pressure torsion(HPT)for its high hydrostatic pressure and high shear deformation capacity,so HPT process has high application prospect in composite preparation field.But HPT leads to SiC particles breakage easily for the reason of high pressure and shear deformation,the distribution of broken SiC particles and SiC-Al interface affect the mechnical and thermal properties directly.In this article,SiC_P/Al composites have been prepared by HPT process on the condition of different pressure and torsion numbers,the effects of process parameters on SiC particle breakage and SiC-Al interface were studied,the mechnical and thermal properties were investigated.The results show that the greater HPT pressure,the greater degree of SiC particle breakage and more particles,but the distribution of broken particles is non-uniform.With the increase of HPT turns,the average particle size decreases,number of small SiC particle increases,the particle breakage phenomenon is more obviously.New SiC-Al interface formed in SiC_P/Al composites,new interface is clear and there is no reaction products,inter-diffusion of Al and Si atoms occurred in new interface,the width of diffusion zone increases with the growth of torsion turns.High density lattice defects appeared in Al grains near the new interface,increasing torsion numbers leads to the growth of lattice distortion that results in the increase of diffusion zone width.Although the particle breakage is serious,the mechanical properties of samples are not decreased but increased.Increasing pressure results in the growth of microhardness.With the rise of torsion numbers,microhardness and tensile strength grow continuously,and elongation is increased;the number of dimples increased in fracture morphology and matrix tearing edge is more obvious,sample of higher torsion turns has better plasticity.The coefficient of thermal expansion(CTE)of higher pressure samples is lower and has better dimensional stability,the dimensional stability of 1Gpa sample is thebest one.Samples of higher turns have lower CTE and better dimensional stability.The thermal conductivity of samples with different pressure increases first and then decreases with the increase of HPT pressure,the thermal conductivity of 1Gpa sample is the maximum.The thermal conductivity of samples with different pressure increases first and then decreases with the increase of HPT pressure,among them1 Gpa sample is the maximum.With the rise of torsion turns,the thermal conductivity of samples increases obviously and then decreases slightly,the recrystallization temperature decreases and the stored energy increases continuously.