基于搅拌摩擦焊驱动模式分析压铸态AZ91D镁合金接头隧道状缺陷形成原因

Study the tunnel defects of die casting AZ91D magnesium alloy with FSW drive model

采用不同焊接规范对压铸态AZ91D镁合金进行搅拌摩擦焊连接,并采用光学显微镜、扫描电镜等方式对焊缝接头微观形貌进行研究。结果表明,焊接速率高于60mm/min时,焊缝中均产生贯穿型隧道状缺陷,缺陷位于焊缝前进侧冠状区与环形区交界处;随着焊接速率的增大,缺陷有逐渐向焊缝底部延伸的趋势。分析认为该缺陷的形成机理如下:冠状区塑性材料同时受到搅拌针和轴肩共同作用,环形区塑性材料主要受到搅拌针作用,致使环形区与冠状区结合处呈现出流动差异性,导致在前进侧产生隧道状缺陷。

Die casting plates of AZ91D magnesium alloy, were welded by friction stir welding, with different welding pammeter, then study the microstructure by OM and SEM. The results show that AZ91D plates with thickness of 4mm, were welded by friction stir welding,when weld speed over 60mm/min,and the joint are easier to generate through type tunnel defects, which was usually locate in the boundary between crown zone and ring zone of advancing side, then spread to the bottom of weld followed by the weld speed increasing. The formation mechanism of the defect as follows： crown area plastic material are drived by shoulder and tool pin,but the ring area plastic material were drived just by tool pin. The different driving mode, which can be caused flow differences between crown zone and ring zone. This phenomenon will be product through type tunnel defects.