Laser Powder Bed Fusion of Defect-Free NiTi Shape Memory Alloy Parts with Superior Tensile Superelasticity

Laser powder bed fusion is a promising additive manufacturing technique for the fabrication of NiTi shape memory alloy parts with complex geometries that are otherwise difficult to fabricate through traditional processing methods. The particularly attractive biomedical applications alloys, such as stents, implants, and dental surgical devices, where primarily superelastic effect exploited. However, few additively manufactured have been reported exhibit superelasticity under tension in as-printed condition, without post-fabrication heat treatment, due either persistent porosity formation or brittleness from oxidation during printing, both. In this study, were fabricated using laser consistently exhibited room temperature tensile up 6% almost twice maximum value literature. This was achieved by eliminating cracks use optimized parameters, carefully tailoring evaporation Ni Ni-rich feedstock, controlling printing chamber oxygen content. Crystallographic texture analysis demonstrated had strong preferential superelasticity, factor needs be considered when shaped subjected combined loadings. Transmission electron microscopy investigations revealed presence nano-sized oxide particles precipitates parts, which play role improved suppressing inelastic accommodation mechanisms martensitic transformation. Graphical Abstract .