SLM Additive Manufacturing of NiTi Porous Implants: A Review of Constitutive Models, Finite Element Simulations, Manufacturing, Heat Treatment, Mechanical, and Biomedical Studies

Nitinol shape memory alloy is a biocompatible material that is suitable for biomedical applications due to its superelasticity, shape memory effect, good corrosion and fatigue resistance, and sound damping properties. With the selective laser melting (SLM) additive manufacturing process, it is possible to produce customized NiTi implants in the form of porous metamaterials with complex geometries. This paper presents a review of modeling, production, and application of NiTi implants. First, the fundamentals of shape memory alloys and the SLM process are summarized. Then, the effects of the SLM process on the transformation temperatures and the impacts of Heat treatments on these temperatures for additive manufactured parts are discussed. Next, a review of recent experimental works on the mechanical properties of NiTi lattice structures are presented regarding the required functional properties of orthopedic implants. Also, in vitro and in vivo biological studies of NiTi implants are reviewed. Finally, constitutive models developed for SMAs are presented and finite element simulations of NiTi lattice structures are discussed.