Abstract: In order to solve the problems that poor coordinated deformation of the dissimilar composite metal with large rolling reduction, difficulty in removing the interfacial oxide film and controlling the formation of intermetallic compounds(IMCs) in the fabrication process of Magnesium/Aluminum alloy composite plate by traditional hot rolling, a new method of rolling-welding process assisted by high-frequency pulse current is proposed for preparing magnesium/aluminum alloy composite plates. The interfacial morphologies and bonding strength of the composite plate are investigated under pulse current of 30 kHz, 400 A and 50%duty cycle that was loaded for 120 s with the different rolling reduction parameters. The results show that the shear strength of composite plate is the highest and up to 27.87 MPa when the rolling reduction is 16.8%. In addition, different degrees of molten liquid metals are extruded at the bonding interface in various rolling reduction. The IMCs transition layer is thick and reaches to 7.8 μm, and the interfacial morphology presents an obvious “toothed” structure when the rolling reduction is low(the rolling reductions are 16.8%and 22.3%). Accompanied by increasing of the rolling reduction, the thinner IMCs layers are reserved at the interface and also a flat interface is obtained. Comprehensive analysis shows that the Magnesium/Aluminum alloy composite plates can be fabricated by a low rolling reduction with the assistance of high-frequency pulse current, and the interfacial bonding mechanism can be summarized as follows: the metallurgical bonding mechanism of local high temperature at the bonding interface of Magnesium/Aluminum leads to part of base metal molten brazing and mutual atomic diffusion bonding. This can be contributed to the local high temperature of the bonding interface and exceeds the eutectic phase of the Mg-Al phase diagram above the eutectic point. On the one hand, the local temperature rise is due to an increase in contact resistance at the bonding interface. On the other hand, localized high temperatures are caused by skin-setting effects the skin and adjacent effects of high-frequency pulse current.

Key words: Mg/Al alloy composite plate, high frequency pulse current, rolling-welding composite forming, localized metal melting, metallurgical bonding mechanism