An approach to enhancement of Mg alloy joint performance by additional pass of friction stir processing

Profuse extension twins were successfully introduced to the whole stir zone of friction stir welded AZ31 alloy, and the joint turned out to be a two-layered structure after an additional pass of friction stir processing with a different tool under appropriate parameters. The detailed twinning characteristics and resultant texture evolution in various regions were then investigated. The strengthening effect of twin lamellae and the weakened strain localization in deformation gave rise to a significant improvement of joint mechanical properties. The yield strength of the joint was raised from 96 MPa to 122 MPa and the tensile strength was enhanced to be roughly equal to that of the base material with no reduction of elongation.