Improving weld strength of arc-assisted ultrasonic seam welded Mg/Al joint with Sn interlayer

Highlights: • Mg and Al alloys were successfully joined by arc-assisted ultrasonic seam welding. • Sn interlayer was used to restrain the formation of brittle MgAl IMCs. • Effects of GTAW current on microstructure and mechanical properties were studies. • The maximum peak load with Sn interlayer was 1.3 kN, which was about 30% increase. Welding of Mg and Al alloys is hugely challenging due to the formation of hard and brittle MgAl intermetallic compounds (IMCs). In this research, gas tungsten arc welding (GTAW) assisted hybrid ultrasonic seam welding with Sn interlayer was designed to join Mg to Al alloys. Effects of Sn interlayer and GTAW current on the microstructure and mechanical properties of the joints were investigated in detail. The results indicated that Sn interlayer could restrain the formation of MgAl IMCs, which were replaced by Mg₂Sn and Sn-based solid solution. The peak load of the joints increased with the GTAW current increasing and then decreased dramatically at higher GTAW current. The maximum peak load of the joints with Sn interlayer was approximately 1.3 kN, which about 30% increase over the joints without Sn interlayer. All the joint failures occurred by the interface mode at the Al/Sn interface and the fracture patterns exhibited entirely brittle fracture mode with cleavage facet feature surface.