Laser welding of NiTi shape memory alloy: a review

NiTi shape memory alloys (SMA) are broadly employed in multifunctional systems in several industrial domains, like aerospace, automotive, biomedical and power plants. Their functional properties, which include shape memory effect (SME) and superelasticity (SE), offer a particular flexibility to design many smart components. However, scientists and practitioners are still facing some restrictions in machining processes and joining techniques of NiTi SMAs to both similar and dissimilar materials. Compared to other procedures, laser welding is an economical and reliable joining technique for NiTi SMAs. Nevertheless, it is considered a challenging technique, with many obstacles still to overcome to achieve welded joints characterized by the necessary strength and the required functionalities. In this respect, the present work investigates the effects of laser welding process on the functional properties of NiTi and related alloys. Mechanical, microstructural, and metallurgical effects of the process are reported, as well. Lastly, the impact of the post-weld heat treatment (PWHT) is studied as an effective solution to improve the downsides of the laser welding process.