Dissimilar welding of NiTi and stainless steel (SS) for multifunctional device fabrication is challenging due to the brittle nature of intermetallic compounds (IMCs) that are formed in the weld zone. In this work, Ni and Nb interlayers were applied for the resistance spot welding (RSW) of NiTi and SS to replace the harmful Fe₂Ti phase and to restrict the mixing of dissimilar molten metals, respectively. Microstructural evolutions and mechanical properties of the joints were investigated. It was shown that a conventional weld nugget was created in the absence of any interlayer in the welded joint suffering from traversed cracks due to the formation of brittle IMCs network in the fusion zone (FZ). By the addition of Ni from the interlayer, Fe₂Ti dominated weld nugget was efficaciously replaced by Ni₃Ti phase; however, the presence of the large pore and cracks reduced the effective joining area. The use of a Nb interlayer resulted in a fundamentally different joint, in which FZs at NiTi and SS sides separated by the unmolten Nb would suppress the mixing of dissimilar molten metals. Nb-containing eutectic structures with low brittleness formed at the interfaces, contributing to the enhancement of joint strength (increased by 38% on fracture load and 460% on energy absorption). A high-melting-point interlayer showed great potential to realize a reliable and high-performing RSWed NiTi-SS joint.

由于焊接区形成的金属间化合物 (IMC) 具有脆性，用于多功能器件制造的 NiTi 和不锈钢 (SS) 异种材料焊接具有挑战性。在这项工作中，Ni 和 Nb 中间层分别应用于 NiTi 和 SS 的电阻点焊（RSW）中，以取代有害的 Fe ₂ Ti 相并限制异种熔融金属的混合。研究了接头的微观结构演变和机械性能。结果表明，传统的焊核是在焊接接头中没有任何中间层的情况下产生的，由于在熔合区 (FZ) 中形成了脆性 IMC 网络，因此会出现横向裂纹。通过从中间层添加Ni，Fe ₂以Ti为主的焊核被Ni ₃ Ti相有效取代；然而，大孔隙和裂纹的存在减少了有效连接面积。使用 Nb 夹层会产生根本不同的接头，其中 NiTi 和 SS 侧的 FZ 被未熔化的 Nb 隔开，从而抑制不同种熔融金属的混合。在界面处形成低脆性的含铌共晶组织，有助于提高接头强度（断裂载荷增加38％，能量吸收增加460％）。高熔点中间层显示出实现可靠且高性能的 RSWed NiTi-SS 接头的巨大潜力。