Deformation Characterization, Twinning Behavior and Mechanical Properties of Dissimilar Friction-Stir-Welded AM60/AZ31 Alloys Joint During the Three-Point Bending

The AZ31 and AM60 alloys were used for dissimilar friction stir welding (FSW) in this study. The microstructure characteristics of the joint and its three-point bending performance were investigated. The electron backscattered diffraction results showed that the grains in the nugget zone (NZ) were more uniform and refined to a certain extent after FSW, but the grain size of AM60 in the NZ was larger than that of AZ31. The texture was strong locally in the NZ and presented a symmetric distribution characteristic from the advancing side to the retreating side. There were special texture features in the joint, resulting in the occurrence of severe strain localization during the bending process compared with the base materials, which can be well explained by the calculated Schmid factor in terms of the assumed stress state for bending. The bending tests revealed that the joint presented good bending properties compared with AZ31 BM. The bending fracture morphologies suggested that the fracture tended to the NZ interface on the AZ31 side, which was mainly due to the higher SF for basal slip and dislocation concentration degree in the region, and the relatively lower bending strength of AZ31 metal.

Automated summary

The study investigated dissimilar friction stir welding using AZ31 and AM60 alloys, revealing that the grain size in the joint was more uniform and refined after welding, although AM60 had larger grains compared to AZ31. The presence of special texture features in the joint led to severe strain localization during bending.