Hot tearing behavior and microstructure mechanism of Mg-6.5Zn-xY-0.5Zr alloys

Hot tearing behavior and microstructure mechanism of Mg-6.5Zn-xY-0.5Zr (x = 1, 2, 4 and 6) alloys are investigated. The predicted and measured hot tearing susceptibility are in the following order: Mg-6.5Zn-2Y-0.5Zr > Mg-6.5Zn-1Y-0.5Zr > Mg-6.5Zn-4Y-0.5Zr > Mg-6.5Zn-6Y-0.5Zr. The microstructure mechanism of hot tearing was analyzed by x-ray diffraction, electron back scatter diffraction and scanning electron microscopy. The results illustrated that hot tearing susceptibility of the alloy only containing I-phase is lower than that of the alloy containing I-phase and less W-phase, and higher than the alloys containing I-phase and more W-phase. The hot tearing susceptibility of the alloys containing I-phase and W-phase will be decreased with the increase of the amount of W-phase. In addition, the hot tearing susceptibility of the alloys dominated by liquid film theory is higher than that dominated by dendritic bridging theory.