Distribution characteristics of interfacial reaction layer and its effect in resistance spot welded Ti/Q235 joint with an interlayer of niobium

The distribution characteristics of reaction layer in the welding interfacial zone of the joint between pure titanium and Q235 steel welded by using resistance spot welding with an interlayer of niobium. The tensile shear load of joints welded under varying conditions of welding current, welding time, and interlayer thickness was experimentally investigated. As the welding current increases and the welding time extends, the tensile shear load of the joint initially increased and subsequently decreased. The maximum tensile shear load of 6.17 kN was achieved in the joint welded under the welding conditions of 16 kA welding current and 300 ms welding time. At the Nb/steel interface zone of the joint, Fe–Nb intermetallic compounds were formed, whereas a β-Ti layer developed at the Nb/Ti interface zone. The results revealed that the non-breakable Nb interlayer effectively inhibited the diffusion of Ti atoms toward the steel side and prevented the formation of Ti–Fe intermetallic compounds in the Ti/Q235 joint.