High-Productivity Forge Welding of AZ80 Magnesium Alloy to A2024 Aluminum Alloy Using an AC Servo Press

Abstract

We have developed a high-productivity dissimilar bonding technology intended for the automobile sector, which is increasingly becoming multimaterial oriented. The forge-welding process, which involves diffusion bonding with plastic deformation in the open air, was used to bond AZ80 magnesium (Mg) alloy with A2024 aluminum (Al) alloy with a pure titanium (Ti) sheet interlayer using a high-speed, high-precision AC servo press. The influences of the preheat temperature, Ti sheet thickness, and the pressure holding time on the tensile strength were surveyed. In addition, the influence of the polishing of the bonding surfaces was examined. A pressure holding time of 0.1 seconds with a cycle time of less than 2 seconds provided high-strength bonding. Furthermore, a high-strength bond could be achieved with a Ti sheet thickness of only 0.3 mm and without needing polishing before bonding or heat treatment after bonding. Cross-sectional textures of the macro- and micro-fracture surfaces and elemental analyses of the bonded interface were examined. The fracture side of the bonded interface, the Ti-Mg alloy side, had a thin (ca. 5 nm) Ti-Al reaction layer (RL), which confirmed a diffusion bonding mechanism between the Ti and Al elements present in the Mg alloy. Despite processing in air with an extremely short processing time, this impacting press method provided good plastic deformability and sufficient elemental diffusion to result in high-strength bonding with a tensile strength ranging from 130 to 150 MPa.