The Melt Treatment Process Of SIC Particulate-Reinforced Aluminum Alloy

SiCp / Al composites have been one of most hot researches for its high specific strength, high specific stiffness, low coefficient of thermal expansion, excellent wear and corrosion resistance characteristics. Combined with the problem of low densification of the SiCp/A357 composites fabricated by the technology of semi-solid stirring in this paper, and the best process will be made for exploring the effect on the density of the 15vol.% SiCp/A357 composites by means of static vacuum degassing and mixing vacuum degassing.The study found that the densification of 15vol.SiCp/A357 composites could be enhanced when increasing the degassing temperature, prolonging the degassing time and increasing degree of vacuum. The densification increased from 94.06% to 98.03% at the best static degassing process however the SiC particles tended to get together. The densification could reach to 98.95% and SiC particles distributed symmetrically by mixing vacuum degassing which was better than static vacuum degassing. The bubble was rising with the melt for the effect of electromagnetic stirring at mixing vacuum degassing, and it ruptures at some degree of vacuum when reaching to bath surface. At the same time, the agglomeration of SiC particles is alleviated and became symmetrical for the effect of shearing action of mixing power.The research of mechanical properties shows that the elastic modulus of SiCp/A357 composites increases with the increase of the volume fraction of SiC particles. The ability for SiCp/A357 composites to resist external deformation is improved due to the high modulus SiC particles added which can bear load with the matrix alloy. With the SiC particles added, the densification of the SiCp/A357 composites firstly increases and then decreases that primarily dues to dual role of SiC particle reinforced but weakened by stomatas. The extension rate of the high volume SiCp/A357 composites is lower than the matrix alloy and represents brittle fracture.The mechanical properties of the composites can be improved by static vacuum degassing and mixing vacuum degassing. The tensile strength of the 15vol.SiCp/A357 composites was higher after mixing vacuum degassing which increased from 283MPa to 319MPa by T6 treatment and the elastic modulus increased from 83GPa to 96GPa. The mechanical properties of the composites improves when its densification increases that leads to the load can be continuously passed between the matrix alloy and the particles for the reducing effective load bearing area of pores which makes the stress concentration areas smaller.