钕对Mg7Zn2Al镁合金显微组织及力学性能的影响

采用光学显微镜、XRD、SEM和万能实验机等手段研究了稀土Nd(0.3%,0.6%,0.9%)对Mg7Zn2Al镁合金显微组织和力学性能的影响。结果表明:Mg7Zn2Al镁合金中添加Nd后,显微组织中有针状或棒状的Al2Nd和AlNd等稀土相生成,合金中的共晶组织(α-Mg+Mg32(Al,Zn)49+Mg7Zn3)得到了明显细化;但是α-Mg有粗化趋势,呈现发达的树枝状或胞状,共晶相由粗大连续的网状变为细小的块状或颗粒状分布在树枝晶的一次枝晶臂或二次枝晶臂的间隙。随着Nd含量的增加,合金的抗拉强度和延伸率呈逐渐下降趋势,显微组织的粗化是造成合金拉伸性能降低的主要原因,而硬度没有明显的变化。

Effect of Rare Earth Neodymium on Microstructure and Mechanical Properties of Mg7Zn2Al Magnesium Alloy

The effect of Nd(0.3%,0.6%,0.9%) on microstructure and mechanical properties of Mg7Zn2Al magnesium alloy were studied by the methods of OM,XRD,SEM and universal testing machine.The results indicated that some need-like or rod-like Al2Nd and AlNd phases were formed after adding Nd,meanwhile,the eutectic structures(α-Mg+Mg32(Al,Zn)49+Mg7Zn3) were refined.However,the α-Mg was coarsening,which presented as the developed dendrites and cystiform.The fine particle eutectic phases which transformed from bulky continuous structure were distributed in the space of primary and second dendritic arm.The tensile strength and elongation of alloys were declined gradually when Nd content increased.The coarsening of microstructure was the mainly reason for the tensile properties of alloys,but the hardness had no apparently change.