AZ31B变形镁合金激光-MIG复合焊焊接组织和性能分析

Microstructure and Properties of Welding Joints for Lase-MIG Welding of AZ3B Transformative Magnesium

采用激光-MIG复合焊对10mm厚的AZ31B变形镁合金进行焊接。利用光学显微镜、扫描电镜、X射线衍射仪等手段分析了焊接接头的外观和截面特征、显微组织、元素分布、焊缝物相和断口形貌等，并检测了接头区域硬度和接头强度。试验结果表明：采用激光-MIG复合焊能获得成形美观的焊缝，无明显的缺陷；焊缝热影响最大宽度位于激光区，约为100μm，焊缝组织为15～25μm的等轴晶粒；相比于母材，焊缝区的镁元素出现烧损，铝和锰元素的比例有一定增加；焊缝区主要为Mg，Al和少量的MgO相。焊接接头硬度值较均匀；焊缝抗拉强度达到222MPa，断口形貌为混合断裂断口。

The transformative magnesium of 10mm thick AZ3B was welded by the lase-MIG welding. The appearance,the macrophotograph, the microstructure, the Alloy elements profile and the patterns of welded joint was analyzed by means of OM , SEM, X-ray diffraction ,etc. The hardness and the strength of welded joint was measured. The result showed that the appearance was perfection by the lase-MIG welding;, the width of heat affected zone（HAZ） is less than 10 0μm, Within welding joint, there were columnar grains of 15 - 25μm; the proportion of Al and Mn element was increased ,becase Mg element was lossed by high welding temperature in the welding zone. There were Mg,Al and a little MgO in the welding zone. Hardness of the welding joint is almost uniformity. The strenghth of welding joint was 222MPa, and the microstructure of fracture is the section of mix fracture.