Effect of vibration and interlayer metal on intermetallic formation, mechanical behavior, and tribological properties in friction stir welded Al-Zn-Mg dissimilar joint

This study investigates the effects of mechanical vibration and Zn-based interlayer metals on the formation of Al-Mg intermetallic compounds (IMCs) during friction stir welding (FSW) of dissimilar Al-Zn-Mg joints. Microstructure evolution, mechanical properties (hardness, tensile strength, and fracture behavior), and tribological performance were evaluated across the whole joint and three distinct weld regions: upper, middle, and bottom. Results show that the bottom region exhibits the poorest mechanical properties and thickest IMC layers due to inadequate material mixing, while the upper region demonstrates superior characteristics. The introduction of vibration and Zn interlayer significantly reduces Al-Mg IMC thickness, promoting the formation of Mg-Zn IMCs. Grain refinement, particularly on the Mg side, was observed due to enhanced material interlocking and severe plastic deformation. Tribological analysis revealed that dominant wear mechanisms included adhesion, delamination, plastic deformation, and abrasion. Increasing vibration frequency (35–70 Hz) led to reduced coefficient of friction, wear volume, and wear rate, enhancing overall wear resistance of the weld zone. This work can provide important theoretical support for the engineering application of high-performance dissimilar Al-Mg alloys in different resources development.