Hybrid joining mechanism of rivet plug oscillating laser welding for dual-phase steel and magnesium alloy

Abstract

A novel hybrid joining method of rivet plug oscillating laser welding (RPOLW) was explored for joining DP590 dual-phase steel to AZ31B magnesium alloy. Microstructure, mechanical properties, and fracture mode of joints were analyzed, and force field, temperature, and flow field of molten pool were simulated. The results showed that the RPOLW joint presented the characteristic of asymmetrical double molten pool. The load-bearing areas of the joint were categorized into the metallurgical joining area and the riveting joining area. Meanwhile, the metallurgical joining area was the core load-bearing area of the joint, which was composed of a mixed-phase zone and an Al-rich zone. The tensile-shear load of RPOLW joint reached 2.2 kN at the optimal parameter, which was 36% higher than that of riveting joint. The heat accumulation in left molten pool resulted in a greater penetration depth of this side, the mixed-phase zone and Al-rich zone of the left molten pool were more evenly distributed. However, Al-rich zone was embedded in mixed-phase zone in the right molten pool, which was caused by the migration of the flow-field center. Consequently, the fracture position of joint was transferred to the mixed-phase zone in left molten pool.