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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.

Aluminum alloy A5052 and low-carbon steel (SPCC) was welded using resistance spot welding with a cover plate. The interfacial microstructure was observed using electron microscopy. A thick two-layered reaction layer contains Fe2Al5 and FeAl3was observed at the welding interface, respectively. Mechanical property analysis suggested that the reaction layer has no effect on the tensile shear strength of the A5052/SPCC joint and affects the cross tension strength of the joint.

In order to obtain a robust dissimilar joint between titanium and aluminum alloy, a method of resistance spot welding with a cover plate were used to weld two kinds of material. The interfacial microstructure was observed using transmission electron microscopy. The effects of welding parameters on the mechanical properties of the joint were investigated. An approximately 160 nm thick layer of Al solid solution supersaturated with Ti was observed at the welding interface, in which contain the precipitates TiAl3. Mechanical property analysis suggests that the reaction layer has no effect on the tensile shear load of the joint.

The effects of Ni on the properties of the Sn-2.5Ag-0.7Cu-0.1Re solder alloy and its creep properties of solder joints are researched. The results show that with adding 0.05wt% Ni in the Sn-2.5Ag-0.7Cu-0.1Re solder alloy, the elongation can be sharply improved without decreasing its tensile strength and it is 1.4 times higher than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. Accordingly the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints is the longest, which is 13.3 times longer than that of Sn-2.5Ag-0.7Cu-0.1Re and is also longer than that of the commercial Sn-3.8Ag-0.7Cu solder alloy. In the same environmental conditions, the creep rupture life of Sn-2.5Ag-0.7Cu-0.1Re-0.05Ni solder joints can sharply decrease with increasing the temperature and stress.