对 AZ91D 压铸镁合金进行 GTAW 焊接，对一组试样熔池施加介入性机械搅拌，另一组试样则无机械搅拌；焊后对两组试样分别用光学显微镜和扫描电镜观察焊缝气孔形貌和分布、焊缝微观组织，并采用基于 Matlab 软件二次开发的图像分析程序识别和计算焊缝气孔率。结果表明，介入性机械搅拌除改善焊缝成形外观、细化焊缝微观组织外，明显降低了焊缝气孔尺寸和焊缝气孔率；降低气孔率的主要机理应该是搅拌加强了熔池金属液流动和气泡的运动，使气泡上浮和逸出速度加快。
Two groups of die cast AZ91D magnesium alloy were welded by gas tungsten arc welding (GTAW). Interventional mechanical stirring was used to stir the welding pool in one group,and was not used in the other group.The porosity and the microstructure in the welding joint were investigated by optical microscopy (OM) and scanning electron microscopy (SEM).The porosity ratio was identified and calculated by a program based on the Matlab software.The results indicate that the interventional mechanical stirring decreases the ratio and the size of the porosity,with an effect of improving the appearance and the microstructure of the weld joints, the main reason of which was that the interventional mechanical stirring promotes the flow of liquid metal and the motion of bubbles,resulting in accelerating the float and escape of bubbles.
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