Study On Microstructures And Mechanical Properties Of Stirring Cast SiCp/2024 Composites

Particle reinforced aluminum matrix composites exhibit unusual combinations of mechanical, physical properties such as high specific strength and modulus, good wear resistance and low cost, widely used in aerospace, automotive, electronics and other industrial fields. In this paper, The SiCp/2024 composites were prepared by stir casting process, the effect of stir process parameters on particle distribution in the composite, effect of hot extrusion on the microstructures and mechanical properties, and SiCp/2024 composite heat treatment process were studied, the conclusions are drawn as follows:(1) Stirring speed and stirring time significantly effect on the distribution of SiC particles during stir casting process, higher stirring speed or longer stir time would help to improve the dispersion of particles, but if the stirring speed is too high or mixed too long will cause serious Inspiratory problem and particle would easy reunioned. Reasonable stir composite process as follows:stir temperature 680℃-700℃, stirring speed 300rpm, stirring time 15min. SiC particles alloy in an even distribution in the matrix, most of the particles along the grain boundaries, small number of particle distribution inside the grains, There were coarse second-phase distribution of non-continuous form on grain boundaries.(2) After hot extrusion process, SiC particles were fractured, improved uniform distribution, loose, holes and other defects inside of the composite basically eliminated, hot extrusion significantly increase the density of the composite; SiC particles deflected under the action of shear stress during the extrusion process, particle length axis tends to parallel with the extrusion direction and the composite was obvious characteristic banded structure along the flow direction.(3) SiC reinforced aluminum matrix composites were be provided with obvious hardening effect. the higher aging temperature accelerated aging process of the matrix, so that peak aging were presented itself early. After 495℃×45min+177℃X 17h heat treatment process, the matrix dispersed elongated rod phase S '(A12CuMg)as the size of 300-400nm,mechanical properties of the composite as follows:σb=430MPa,σ0.2=345MPa,δ=6.7%。The main fracture mode of SiCp/2024 composites was the fracture of SiC particles, SiC/Al of interfacial debonding, matrix plastic fracture. After hot extrusion SiC/Al interface debonding fracture were more less, hot extrusion deformation would help improve SiC particles and matrix alloy interface strength.