Experimental and Numerical Evaluation of Diffusion Welding of 7075 Aluminum and AZ31 Magnesium Alloys

In the present study, AZ31 magnesium alloy was bonded to 7075 aluminum alloy at different temperatures (393, 402, 412, and 421 °C) and diffrent holding times (25, 60, and 120 min) through diffusion bonding. Moreover, axial loads of 12, 29, 38, and 80 MPa accompanied by vacuum condition were employed during the bonding. The experimental and numerical results of the successful joints confirmed the existence of different reactive layers in diffusion zones and formation of the predicted intermetallic compounds. Findings showed that by applying a pressure of 29 MPa at different temperatures of 402, 412, and 421 °C, Interfacial Transition Zone (ITZ) with thicknesses of 21.26, 21.96, and 22.60 μm, respectively, was formed. Further, the maximum amount of the bond strength (30 MPa), resulting from the proper coalescence of metal surfaces, was obtained at 402 °C. Although the hardness of ITZ was found to be greater than that of the base metals, it could increase even more mainly as a result of an increase in the bonding temperature. Moreover, the results of simulation, using DEFORM-3D software, indicated that the ITZ had different mechanical properties from base metals and that by analyzing the effective stress, the Mg alloy specimen was more deformed than Al alloy during the joining process.