Thermomechanical analysis of ultrasonically welded copper-magnesium sheets with Ni and Zn interlayers

Abstract

This paper presents a thermo-mechanical analysis of ultrasonically welded Cu-Mg sheets with incorporation of Ni and Zn interlayers. The experimental and simulation methods were employed to investigate the thermal mechanisms during welding process. The analysis reveals the variation in interface temperatures, acoustic softening effects and heat fields related to plastic deformation. The accuracy of simulation model is validated through these findings. Microscopic analysis indicates that after 0.4 sec of welding, Ni interlayer on Mg sheet at the center of joint interface partially melts and forms a liquid phase. The average friction coefficient at the weld interface is approximately 0.5. The maximum temperature at the interface can exceed 600 °C and approach the melting point of welded sheets. Plastic deformation begins after 0.45 sec and occurs mainly at Mg sheet interface. The grain size of Mg alloy at interface in this experiment ranges from 4 to 5 μm which is notably finer than the average grain size of 20 μm observed in base materials. The distribution and intensity of deformation fields provide valuable insights into how the Ni and Zn interlayers influence the mechanical integrity and overall performance of weld. Ni interlayer significantly improves mechanical properties of Cu-Mg welded joints, achieving higher load-bearing capacity (7865 N vs. 3688 N), tensile strength (80.23 MPa to 1821.26 MPa vs. 885.15 MPa to 1318.05 MPa) and fracture resistance (8.23 MPa to 1350.55 MPa vs. 6.20 MPa to 350.48 MPa) compared to Zn interlayer.