采用搅拌摩擦焊工艺对4mm厚的压铸态AZ91D镁合金进行对接工艺实验,搅拌头旋转速率1500 r/min,焊接速率120mm/min；使用光学显微镜和扫描电镜对焊接接头微观组织进行了研究.结果表明:焊缝外观成形美观,但内部存在贯穿型隧道状孔洞缺陷；焊核区为典型的变形-再结晶组织,为细小、均匀的等轴晶；机械热影响区为变形-部分再结晶组织,热影响区组织形貌与母材相近但伴有轻微的长大现象；焊核区与机械-热影响区的过渡具有以下特征:在前进侧呈现“突变”特征,在后退侧呈现“渐变”特征.%Die casting plates of AZ91D magnesium alloy, with thickness of 4mm, were welded by friction stir welding, with a rotating speed of 1500r/min and welding speed of 120mm/min. The joint mi-crostructure was studied by OM and SEM. The results show that the appearance of the welding joint is good, but there is a tunnel defect in the joint. The joint microstructure exhibits noticeable deformation characteristics: the grains of weld nugget zone are fine and recrystallized. Thermo-mechanically affected zone shows partially recrystallized microstructure. The microstructure of heat affected zone is similar to that of the base metal while the grains are a little coarser. Moreover, the transition between the weld nugget zone and the thermo-mechanically affected zone in the advancing side is discontinuous, while that in the retreating side is gradient.
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