The resistance spot welding between commercially pure titanium and stainless steel was achieved using an aluminum alloy insert. The interfacial microstructure and mechanical properties of the joint were investigated. The maximum tensile shear load of 5.38 kN was obtained from the Ti/SUS304 joint welded at the welding current of 10 KA. The results reveal that the property of the Ti/SUS304 joint can be improved by using an aluminum alloy insert between Ti and SUS304 sheet.

In order to obtain better understanding of the friction stir weldability of the magnesium alloy and provide some foundational information for improving mechanical properties of retardant magnesium alloy joints. A retardant magnesium alloy was weld using the method of friction stir welding. The influence of welding parameters on the strength of the joint was investigated. The maximum strength of 230 MPa was obtained from the joint welded at the tool rotational speed of 1000 r/min and welding speed of 750 mm/min.

In order to obtain better understanding of the resistance spot weldability of magnesium alloy and provide some foundational information for improving mechanical properties of the magnesium alloy joint, the influencing factors of pore formation during resistance spot welding of magnesium alloy, such as preexisting pores in base material, hydrogen rejection, shrinkage strain and expulsion, were analyzed; the corresponding restraining measures were discussed. The analyses reveal that the shrinkage strain and expulsion are important factors in contributing to the formation of pores during resistance spot welding of magnesium alloy, and that the pore formation could be suppressed by adjusting welding parameters.

A new technique of thermal compensation resistance spot welding was used to weld light metal such as aluminum alloy sheet and magnesium alloy. The effects of welding parameters on the tensile shear strength of joint and nugget diameter were investigated. The tensile shear load and nugget of the joint increased with the increasing of welding time, whereas that of the joint decreased with the increasing of electrode force. The joint with the maximum tensile shear load of approximately 5 kN was obtained at the condition of 12 kA and 11 kA welding current for aluminum alloy and magnesium alloy, respectively. The results reveal that the thermal compensation resistance spot welding is a feasible method to weld aluminum alloy and magnesium alloy..

The diffusion welding between aluminum alloy and steel was achieved in this study. The influence of welding temperature on the interfacial microstructure and tensile shear strength of the joint were investigated. The joint with 101.3 MPa was obtained under the condition of the welding temperature of 525 °C. The results reveal that the reaction layer thickness increases with the increasing of welding temperatures and that the reaction layer consists of Al5Fe2 and Al13Fe4 formed in the interface. The strength of the joint is related to the reaction layer thickness and when the reaction layer thickness was approximately 0.8 μm, the value of the joint strength reached maximum.