A novel laser welding method for the reliable joining of NiTi/301SS

In this paper, a novel laser welding method with Nb/Cu multi-interlayer was developed for improving the mechanical properties of NiTi/301SS joint. A hybrid joint consisting three metallurgical joining zones was obtained based on different welding mechanisms through a single pass welding. The self-fusion welding was formed on the Nb interlayer, and the fusion zone was composed of Nb-based solution. NiTi and Nb were well bonded by eutectic reaction, and the NiTi/Nb interface contained Nb-based solution, NiTi phase and Nb-NiTi eutectic structure. Nb and 301SS were joined by brazing because of the melting of Cu, and the Nb/Cu/301SS interface consisted of Nb-, Cu-, and Fe-based solutions and a little Fe7Nb6 intermetallic. The strength and ductility of the joints with interlayer were 126% and 188% higher than the joints without interlayer, respectively. The use of Nb/Cu multi-interlayer completely prevented the formation of Ti-Fe and TixNiy IMCs, which can improve significantly mechanical properties of joints.