Experimental and Numerical Evaluation of Diffusion Welding of ۷۰۷۵ Aluminum and AZ۳۱ Magnesium Alloys

In the present study, AZ۳۱ magnesium alloy was bonded to ۷۰۷۵ aluminum alloy at different temperatures (۳۹۳, ۴۰۲, ۴۱۲, and ۴۲۱ °C) and diffrent holding times (۲۵, ۶۰, and ۱۲۰ min) through diffusion bonding. Moreover, axial loads of ۱۲, ۲۹, ۳۸, and ۸۰ 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 ۲۹ MPa at different temperatures of ۴۰۲, ۴۱۲, and ۴۲۱ °C, Interfacial Transition Zone (ITZ) with thicknesses of ۲۱.۲۶, ۲۱.۹۶, and ۲۲.۶۰ μm, respectively, was formed. Further, the maximum amount of the bond strength (۳۰ MPa), resulting from the proper coalescence of metal surfaces, was obtained at ۴۰۲ °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-۳D 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.

Keywords:

Diffusion welding , Aluminum Alloy , Magnesium alloy , Microstructure , FEM , effective stress