Mg/Al异种材料点焊接头显微组织研究

Research on Microstructure of Spot Welded Joint with Mg/Al Dissimilar Materials

采用三相次级整流电阻焊机,对2mm厚AZ31B镁合金和LF6铝合金进行点焊试验,并采用扫描电镜、能谱分析、X射线衍射和显微硬度测试等方法,对Mg/Al异种材料电阻点焊接头进行了研究。结果表明,点焊熔核呈帽形,熔核组织形态以细小的等轴树枝晶为主,熔核边缘存在少量的柱状晶。Mg/Al点焊中Al原子的扩散速度远远大于Mg原子,在靠近镁侧形成了Mg17Al12金属间化合物层,其硬度高达251HV。

Three-phase secondary rectification welding machine was used to weld 2mm thick AZ31B magnesium alloy and LF6 aluminum alloy.Scanning electron microscopy（SEM） and X-ray diffraction（XRD） were used to observe the microstructure of spot welding joints,and micro-hardness was tested.The results show that a cap-like nugget is obtained in Mg/Al dissimilar materials spot welding.Small equiaxed dendrites oriented microstructure distributes in the center of nugget morphology,and at the nugget edge present small amounts of columnar grain.In the Mg/Al dissimilar materials resistance spot welding the diffusion rate of Al atoms is fasten than the Mg atoms,and inter-metallic compound layer Mg17Al12 is observed in the weld nugget near Mg side.Its hardness reaches 251HV.