A review of NiTi shape memory alloy as a smart material produced by additive manufacturing

Abstract

Nitinol (nickel-titanium or Ni-Ti) is one of the most utilized alloys exhibiting the Shape Memory Effect, which makes it possible to use it in many applications, such as aerospace, automotive, biomedical and others. The development of Additive Manufacturing technologies allows creating the latest time-dependent 4D products from nitinol that can realize the Shape Memory Effect after 3D-printing, which in the future will further increase the use of nitinol. However, processing nitinol is highly sensitive to compositional and thermal changes, affecting the final phase structure and thus temperature of the martensitic transformation. This paper presents a review of various effects of composition and 3D-printing process parameters on changes in transformation characteristics, as well as possible methods for their prevention and post-process heat treatments. It is reported that only by precise process and temperature control it is possible to create 4D products with the ability to realize the multi-stage shape memory effect. Finally, the paper discusses the various application of 3D-printed Nitinol and its advantages as compared to conventional processing routes.