Microstructure and mechanical property of rolled-weld magnesium alloy AZ31

Highlights: ► A combined cold-rolling and welding technique is applied to Mg alloy AZ31. ► The effect of SRX on HAZ and mechanical property of the joints is investigated. ► The effect of cold rolling on mechanical property of the joints is investigated. ► The SRX processes in HAZ are analyzed by thermodynamic theories and models. -- Abstract: In this paper, a combined cold-rolling and welding technique was applied to magnesium alloy AZ31 in order to investigate the effect of cold rolling and static recrystallization on microstructures evolution and mechanical properties of the welded joints. The results showed that the 7% rolled-weld sample obtained the highest tensile strength (252 MPa) and strength coefficient (87.6%). With the increase of rolling strain, the average grain size decreased in heat affected zone due to the effect of static recrystallization. The recovery, recrystallization nuclei, and grain growth processes in heat affected zone during welding were analyzed by thermodynamic theories and models, respectively. However, abnormal voids and intergranular fracture behavior were found in the 10% rolled-weld joints after tensile test, which was mainly attributed to the gas inclusions, initial micro-voids and high residual stress in base metal.