Effects of Melt Ultrasonic Treatment and Forming Processes on Thermo-Physical Properties of SiC_p/Mg and (SiC_p+Mg2Si)/Mg Composites

摘要

The 10 vol% SiC_p/Mg composites were prepared by external addition and stirring-casting method, and the hybrid reinforced (10 vol% SiC_p+10 vol% Mg2Si)/Mg composites were prepared by combining in-situ method. The effects of melt ultrasonic treatment (UT) and forming processes on the thermophysical properties of the two composites were studied. The results show that UT can effectively disperse SiC particles in molten magnesium and reduce the casting porosity, while squeeze casting can significantly reduce the porosity of the composites, which can also significantly improve the thermal conductivity. The thermal conductivity (λ.) of 10 vol.% SiC_p/Mg composites squeeze casted after UT was 135.3 W/(m·K), and the average coefficient of thermal expansion (CTE) was 19.95×10~(-6) K~(-1) at 323-373 K. Compared with gravity casting, the λ was increased by 17% and the CTE was reduced by 0.8%. The λ of (SiC_p+Mg2Si)/Mg composite squeeze casted after UT was 132.4 W/(m·K), and the CTE was 18.95×10~(-6) K~(-1), which is 27% lower than the CTE of pure magnesium.