Zn对Mg-9Al合金凝固行为的影响

研究了Zn元素对Mg-9Akl合金的凝固行为，尤其是对热裂倾向性的影响。通过热分析手段考察合金的凝固特征。用热裂环法评价合金的热裂倾向性，引入了热裂倾向性（HSC）因子的概念。并通过金相观察、扫描电镜和电子探针对合金的凝固、热裂行为进行了研究。研究发现，在凝固过程中An,Al元素由于晶间偏析而在晶界富集。Zn元素的加入，增加了晶界低熔点相的量，并降低了其熔点，从而明显增加了合金的热裂倾向性。Mg-9Al-xZn合金的热凝产生于凝固后期，呈沿晶断裂。加入Zn元素对Mg-9Al合金的晶粒有细化作用。

Effects of Zn on the Solidification Behavior of Mg-9Al Alloys

The effects of Zn on the solidification behavior, especially hot tear susceptility of Mg 9Al were examined. The solidification characteristics of the alloy were examined by thermal analysis. Crack rings sample was applied to estimate the hot tear susceptility of the alloy with introduction of the HSC(hot tear susceptility coefficient) concept. The solidification and hot tear behavior of the alloy were studied by optical microscopy, SEM and probe. The results showed that Zn and Al enriched in grain boundary due to the intercrystalline segregation during solidification process were increased with Zn addition to enhance the phase formation with low melting point and in turn to enhance the hot tear susceptility of the alloy. The hot tear originates at the later period solidification and propagates along grain boundary for Mg 9Al x Zn alloy. Zn addition can refine the grain of the Mg 9Al.