Effect of Al Content on the Solidification Behaviors of Mg-Al Alloys

The variations in force, displacement and temperature over time during solidification and subsequent cooling processes were measured by a force-tested module and a displacement-tested module, respectively. Then, the effects of Al content (0, 5, 10, 15, 19 and 22 wt%) on the solidification behaviors of as-cast Mg-Al binary alloys were obtained. The results showed that the expansion behavior in the mushy zone gave rise to a large change in displacement but a relatively slight change in compressive force. With increasing Al content, the changes of the maximum expansion velocity and maximum compressive force followed the ? shapes, with the largest values of 13.44 x 10(-3) mm s(-1) and 74.4 N in the as-cast Mg-10 wt% Al alloy, respectively. But the critical Al content for the solidification shrinkage behavior of the as-cast Mg-Al alloy was 15 wt%. That is, with increasing Al content, the mean solidification shrinkage velocity in the mushy zone after expansion decreased significantly on the condition of Al addition being < 15 wt%, while decreased slightly if the Al addition was > 15 wt%. Furthermore, the effect of Al content on the hot cracking tendency of Mg-Al alloys also followed the ? shape, with the highest accumulating stress coefficient of 1.90 x 10(-4 )MPa center dot(s degrees C)(-1) in the Mg-15 wt% Al alloy.

Automated summary

The force, displacement, and temperature variations during solidification and cooling processes of Mg-Al alloy were measured. The effect of Al content on solidification behavior, solidification shrinkage behavior, and hot cracking tendency was investigated.