Zn interlayer and tool offset effects on IMC formation and strength of AA5083/AZ91Mg joints via friction stir vibration welding

The study of the joint between AA5083 aluminum alloy and AZ91 magnesium alloy is of significant importance due to the growing demand for lightweight, high-performance materials. Zn-added, friction stir vibration welding (FSVW) was applied to enhance the joint quality of AA5083/AZ91Mg biomaterial composites under different tool offset conditions. The effects of mechanical vibration during FSW (FSVW), with and without a Zn interlayer, were simulated and validated experimentally. The numerical and experimental results showed good agreement. Compared to conventional FSW, FSVW with a Zn interlayer refined the weld zone (WZ) microstructure, improved mechanical properties, reduced residual stress and metallurgical defects, and produced thinner and more uniformly distributed Mg-Zn intermetallic compounds (IMCs), instead of the brittle Al–Mg IMCs. Residual stress analysis revealed tensile stress near the tool area and compressive stress beyond it, with overall lower stress observed in FSV welded samples containing a Zn interlayer. The best results were achieved with tool offsets toward the aluminum or magnesium sides. The maximum hardness and tensile strength in the optimized weld reached 230 HV and 190 MPa, respectively. Improved material mixing and mechanical interlocking at the interface contributed to enhanced joint toughness.