Microstructure Characteristics and Properties of Mg/Al Dissimilar Metals Made by Cold Metal Transfer Welding with ER4043 Filler Metal

AZ31B magnesium alloy and 6061 aluminum alloy were joined in stable welding process by cold metal transfer welding with ER4043 as filler metal. The microstructure, morphology and phase composition of the welded joints were studied by OM, SEM, EDX and XRD. The results show that weld metal and aluminum substrate are combined with a good interface, while weld metal and Mg substrate are combined with a epitaxial solidification area where the intermetallic compounds of Mg2Al3, Mg17Al12 and Mg2Si are generated. The micro-hardness distribution shows a decreasing trend from Mg side to Al side in the weld. The joint is brittle fractured in the fusion zone of Mg side, where plenty of Mg2Si, Mg2Al3 and Mg17Al12 are distributed continuously.