Laser welding of TiNi shape memory alloy and stainless steel using Ni interlayer

Welding and Joining of NiTi Shape Memory Alloys: A Review

“…For the Ni interlayer [176], it was observed that the dilution of the FZ occurred by increasing the interlayer thickness (ranging from 10 to 100 µm), as depicted in Fig. 46.…”

“…Similarly to Pouquet et al [172] the use of filler materials between NiTi and stainless steel in butt joint configuration was performed by Li et al in [19,176,177] using Co, Ni and Cu interlayers, respectively. In these studies a similar finding is observed: interlayers can promote better mechanical properties of the welded joints as they reduce the amount of brittle precipitates, such as: Fe ?2 Ti or Cr ?2 Ti.…”

“…Such a precise control of the conditions to promote a sound joining between NiTi and stainless steel was already achieved by some authors [17,19,173,174,176,177]. Vannod et al [17] presented a very in-depth study on the characterization of NiTi/ stainless steels joints using wires.…”

“…Aside from Ti ?2 Ni, other intermetallics were also found to exist in the FZ of the laser joints, namely: Ni ?3 Ti [132,133,148,149], and Ni ?4 Ti ?3 precipitates [150,167]. The presence of Ni-rich precipitates in the HAZ due to laser welding must be more carefully analysed as the thermo-mechanical history of the base material has a significant role on the onset for the precipitation to occur.…”

“…Li et al [150] laser butt welded Ti-rich NiTi using a pure Copper interlayer between the interfaces to be joined. Structural analysis by micro X-ray diffraction revealed the presence of Ni ?4 Ti ?3 and a significant amount of intermetallics Cu-based compounds: CuTi, Cu ?4 Ti ?3 , Ti ?4 Cu ?3 and Cu ?3 Ti ?2 .…”