The Research Of Mg/Al Spot Welding With Transition Layer

Because magnesium alloy and aluminum are widely used in various fields, and with the development of modern industry and scientific progress, a single metal magnesium alloy and aluminum welding has been unable to meet the practical engineering applications. However, as the physical and chemical properties of magnesium, aluminum large difference between the welding magnesium/aluminum dissimilar material joints obtained poor performance. Therefore, the mechanism of this topic magnesium/aluminum resistance spot welding joints based on the transition layer of zinc launched a study of the system.Through the study of this subject magnesium/aluminum direct resistance spot welding, the maximum tensile shear of connectors is only3.8KN, scan the joint fracture can be observed like a lot of cleavage steps, have not obvious dimple appeared, phase analysis of the joint discovery of magnesium/aluminum resistance spot welding at the joints between the MgAl and Mg17Al12have other hard and brittle intermetallic compound formation.The mechanism of the transition layer of zinc magnesium/aluminum resistance point-based research, get the joints in the welding current27.4KA, electrode force8.5KN,26cycles weld time conditions by orthogonal joints pull shear maximum4.96KN. Through the joint micro-hardness testing phase analysis and cross-section obtained in the joint at some nugget brittle phase formation,The other area than the nugget hardness values and lower side of the fracture in the magnesium matrix and the Mg composition MgZn2, the aluminum side of the fracture Al matrix, MgZn2and Al5Mg11Zn4composition. Connector nugget of the microstructure is composed of columnar grains and equiaxed, as the transition layer of zinc added, First, An intermediate layer between the zinc and base metal interface formation of solid phase diffusion, in the Mg-Al interface is generated by the first Mg-Zn eutectic compound and Al5Mg11Zn4compounds, and with increasing time of welding electrode under the action of pressure, part of the molten liquid metal zinc to protect joints of oxide, when the temperature reaches the melting point of magnesium alloy fittings and aluminum joints began to form nugget, However, because the buffer layer of zinc the reaction was complete, the small joints of the intermetallic compound Mg17Al12, MgAl and other generates, which was significantly better than the performance of the connector so that the magnesium/aluminum direct resistance spot welding.