Present status and future trend of friction stir-based fabrication of NiTinol: a review

NiTinol has emerged as a popular candidate in different fields of the manufacturing industry because of its unique properties. Different studies have revealed that NiTinol has a good shape memory effect (SME), superelasticity (SE), biocompatibility, and corrosion resistance property; the machinability and formability issues of NiTinol are posing challenges to the widespread use of the alloy. Fabrication of NiTinol without sacrificing its superior characteristics would help to extend its application in different industries. A solid-state friction-based fabrication method, namely, friction stir processing (FSP) and friction stir welding (FSW), can retain the superior properties of NiTinol after fabrication. This study summarizes the research in the field of solid-state fabrication of NiTinol in similar and dissimilar material combinations. Selection of different process parameters, material composition, complex material flow, and cooling of the weld nuggets play important roles in controlling different properties of the fabricated components. An emphasis is given to identifying different recent challenges to enhance subsurface and surface properties, mechanical properties, chemical compositions, and thermomechanical properties of the fabricated alloy. As many of the drawbacks of the fusion-based fabrication methods of NiTinol are overcome by the FSW process and the overall thermomechanical, mechanical, and corrosion resistance properties of the FSW-ed NiTinol are good enough, this method of fabrication for NiTinol is gaining interest in many fields. The future scope of the research in the field of solid-state additive manufacturing of NiTinol will also be addressed in this review.