Study on Solidification Behavior and Hot Tearing Susceptibility of Mg–2xY–xNi ALLOYS

Abstract

Mg–2xY–xTM(Zn,Cu,Ni) alloys reinforced with LPSO have outstanding mechanical properties, but there is less research on Mg–2xY–xNi hot tearing sensitivity. Therefore, based on Clyne Davies Model and Newton Baseline Method, the hot tearing tendency of Mg–2xY–xNi alloys with x = 0.5, 1, 1.5, 2.0, 2.5 wt% was quantified, and the tendency was further verified by the tearing evaluation of “T” shaped castings. The results show that the hot tearing susceptibility (HTS) decreases with the increase in x. Especially when x ≥ 1.5 wt%, and the HTS of Mg–Y–Ni alloys is even lower than that of Mg–Y–Zn alloys. The analysis of solidification microstructure evolution reveals that with the increase in x, the grain refinement and equiaxed tendency of α-Mg increases, and the solid fraction increases when dendrites are coherent, and the feeding stage of residual liquid phase between dendrites is shortened, which is an important reason for the decrease in hot tearing tendency. The analysis of phase transformation shows that with the increase in x, the residual liquid phase between α grains increases, which has better feeding effect on solidification, while the precipitation amount of LPSO phase which has coherent relationship with α increases, and its bridging effect on inhibiting grain boundary cracking is enhanced, which is another reason for reducing the HTS.