变形镁合金熔焊接头组织特征分析

Microstructure feature analysis of fusion welded joint of wrought Mg-alloy

摘要: 采用光学显微镜、X射线衍射仪(XRD)和电子探针(EPMA)等分析测试手段,对变形镁合金AZ31B的TIG焊接头进行了微观组织观察、相组成和微区成分分析试验。结果发现在熔焊条件下AZ31B镁合金焊缝附近的纤维组织消失,在焊缝区出现了细晶粒,而热影响区(HAZ)的晶粒明显粗大。进一步研究发现焊缝区的晶粒主要呈细小的等轴晶,室温组织是由δ-Mg相和γ-Mg₁₇Al₁₂化合物两相组成。分析还发现焊缝区的Mg含量低于母材,而Al的含量则高于母材;电子探针分析发现Mg、Al、Zn元素存在成分偏析现象。

Abstract: In this paper,the microstructures,phase constituent and micro zone analysis of AZ31B wrought Mg alloy welded joint were investigated by optical microscope,XRD and EPMA.The results showed that the fibrous structure of AZ31B Mg alloy disappeared;the fine crystal grain appeared in weld metal and the microstructure of heat affected zone (HAZ) obviously became coarse.The fine equiaxed grains were observed in the weld metal,the microstructure at room temperature consists of δ-Mg phase and compound of γ-Mg₁₇Al₁₂.It found the Mg content in the weld metal is lower than parent metal,however,Al content is higher than parent metal,at the same time there are the segregation of Mg,Al and Zn elements in weld metal.