Study on the Hot Tearing Susceptibility of Mg-4Zn-xSn-1Ca Alloys

Based on the Clyne-Davies hot tearing prediction model, the effect of Sn addition on the hot tearing susceptibility (HTS) of Mg-4Zn-xSn-1Ca (x=0, 0.5, 1.0, 2.0 wt%) alloy was studied using T-shaped hot tearing mold at a pouring temperature of 700 degrees C and a mold temperature of 270 degrees C. The dendrite coherency temperature was obtained by means of differential thermal analysis. The Phase transformation, microstructure, and morphology of the crack zone of Mg-4Zn-xSn-0.6Zr alloys were investigated via scanning electron microscopy and optical microscopy. Mg-4Zn-xSn-1Ca alloys were found to be composed of alpha-Mg, Ca2Mg6Zn3, and CaMgSn phases. The appropriate Sn addition was shown to be an effective way for refining grains, decreasing the dendrite coherency temperature and increasing the liquid film thickness, which could reduce the HTS of the Mg-4Zn-xSn-0.6Zr alloys. However, excessive Sn content made the acicular CaMgSn phases gather together to form a network structure, which affected feeding of the residual liquid phase and increased the alloy's HTS. In studied alloys, the HTS followed a sequence of CSC (Mg-4Zn-1Ca)>CSC (Mg-4Zn-0.5Sn-1Ca)> CSC (Mg-4Zn-2Sn-1Ca)> CSC (Mg-4Zn-1Sn-1Ca).

Automated summary

The effect of Sn addition on the hot tearing susceptibility of Mg-4Zn-xSn-0.6Zr alloy was studied. It was found that appropriate Sn addition could reduce the hot tearing susceptibility, while excessive Sn content increased it.