Microstructure of Welded Joint of Die-cast AZ91D Alloy Plates Welded by TIG
As-cast AZ91D alloy plate with 3 mm thickness was welded by both sides using TIG.The welding process was that the current of first side was AC 120A and that of reverse side was 80A,90A and 100A,the welding speed and protection gas flow was constant.After welding,the cross-sections of the sample were prepared using standard procedures.The microstructure was investigated by optical microscopy.The results show that the surface appearance of the weld beads is not good,there are some visible defects;with the increase of electric current of reverse side,the amount of the continuous β-Mg17Al12 phase decrease,while the amount of the granular β-Mg17Al12 phase increase.