Ce/Ca对AZ91D镁合金组织与力学性能的影响

Effects of Ce/Ca on Microstructure and Mechanical Properties of AZ91D Magnesium Alloy

利用光学金相显微镜和XRD分析了分别加入0.7wt%Ce和0.7wt%Ca后AZ91D镁合金的显微组织和相成分,测试了合金的室温拉伸力学性能和硬度。结果表明,加入0.7wt%Ce后,合金组织中生成杆状化合物Al4Ce相,而加入0.7wt%Ca后,合金组织中无新相生成,Ca主要固溶于β相中;合金组织中的Al4Ce相是在晶间共晶反应时形成的,而Ca原子容易偏聚在生长枝晶前沿,阻碍枝晶的自由生长,从而细化合金铸态组织;0.7wt%Ce和0.7wt%Ca的加入均能提高合金的室温综合力学性能,且Ce的提高程度要高于Ca的提高程度。

Microstructures and phase compositions of AZ91D alloys after adding 0.7 wt%Ce and 0.7 wt%Ca respectively were observed by using optical microscope and XRD, meanwhile their mechanical properties and hardness at ambient temperature were tested. The results show that a rodlike compound Al4Ce phase is formed in the alloy after adding 0.7 wt%Ce, however,there is no new phase is found after adding 0.7 wt%Ca and Ca is mainly dissolved in β phase. During eutectic solidification, Al4Ce phase is formed at the grain boundary and Ca atoms are easy to enrich in the front edge of the growth dendrite, thus the free growth of the dendrite is hindered in degree and ascast microstructures are refined. The additions of 0.7 wt%Ce and 0.7 wt%Ca can improve the whole mechanical properties of the alloys and the improvement degree of Ce is higher than that of Ca.