Abnormal macropore formation during double-sided gas tungsten arc welding of magnesium AZ91D alloy

作者：Shen Jun^*; You Guoqiang; Long Siyuan; Pan Fusheng

来源：Materials Characterization, 2008, 59(8): 1059-1065.

DOI：10.1016/j.matchar.2007.08.021

• magnesium AZ91D alloy
• macropore
• gas tungsten arc welding
• partially melted zone

One of the major concerns during gas tungsten arc (GTA) welding of cast magnesium alloys is the presence of large macroporosity in weldments, normally thought to occur from the presence of gas in the castings. In this study, a double-sided GTA welding process was adopted to join wrought magnesium AZ91D alloy plates. Micropores were formed in the weld zone of the first side that was welded, due to precipitation of H(2) as the mushy zone freezes. When the reverse side was welded, the heat generated caused the mushy zone in the initial weld to reform. The micropores in the initial weld then coalesced and expanded to form macropores by means of gas expansion through small holes that are present at the grain boundaries in the partially melted zone. Macropores in the partially melted zone increase with increased heat input, so that when a filler metal is used the macropores are smaller in number and in size.

• 出版日期2008-8
• 单位重庆大学