激光焊接AZ31B镁合金接头微观组织特征

采用YAG激光器焊接Z31B镁合金，利用金相显微镜、电子探针、X射线、扫描电镜、硬度仪分别研究了激光焊接接头的微观组织、元素分布、断口形貌、硬度变化。结果表明，AZ31B镁合金激光焊接接头没有明显的热影响区，焊缝狭窄，接头成形好，焊缝为细小的等轴晶，但靠近上表面存在大晶粒；没有发现区域偏析，无脆晶相(Mg17Al12)存在；镁的蒸发损失导致焊缝金属中铝含量的升高，而锌基本不变，同时熔深方向镁的损失增大；断口表现为混合断裂，没有气孔和裂纹存在；硬度沿熔深方向变大。

Micro structure character of YAG laser welding AZ31B Mg ahoy

The YAG laser was used to weld AZ31B Mg alloy. Themicrostrueture, element profile, fracture surface and hardness were investi-gated by the metal phase microscopy, electron probe microanaiysis, scan-ning electron microscope , X - ray and hardness instrument. The resultsshow that favorable joint can be obtained, which heat-affected zone is notevident, and weld is narrow and the grains of fusion zone (FZ)are fineequlaxed- grain. Besides, element segregation and Mgl7 All2 phase cannot be found in FZ. Vaporizing of Mg element led to the increasing of A1content, but Zn content is constant. At the same time, the Mg element lossincreases at direction of fusion depth. The fracture shows quasi-cleavage,which does not exist porosity and crack. The hardness increases at fusiondepth direction.