Ca对AZ91D合金抗热裂性能的影响及其机制

Effects and Mechanism of Ca on Hot Crack Resistant Property of AZ91D Alloy

利用金相、扫瞄电镜及热分析等研究了添加Ca对AZ91D合金抗热裂性能的影响及其机制,结果表明:随着Ca添加量增加(≤1 0%Ca),抗热裂性能变差。其热裂机制为:添加钙,导致Al2Ca相在晶界析出并生长,同时促进离异共晶,降低了合金熔体的填充能力;含钙相在晶间呈网状分布,降低了晶间液膜的界面张力;从而导致合金抗热裂性能的下降。

The influence and mechanism of calcium on hot crack resistant property of AZ91D alloy were investigated in this article by optical microscopy, scan electron microscope and thermal analysis. It has been shown that with the quantity of added Ca (≤1.0wt%Ca) increased, the hot crack resistant property of AZ91D alloy decreased. The related hot crack mechanism is as followed: Ca promotes the formation and aggregation of Al_2Ca phase in grain boundaries, intensifies the tendency of divorced eutectic, lowers the filling ability of the melt. Besides, the reticular Ca contained phases distribute along grain boundaries thus lower the boundary tension of the melt between grain boundaries. These factors induce the decline of hot crack resistant property of AZ91D alloy.