Strain rate effects on deformation and martensitic transformation in NiTi alloys fabricated by additive manufacturing under quasi-static tension

Laser Powder Bed Fusion (LPBF) has emerged as a promising technique for fabricating NiTi shape memory alloy (SMA) components, providing potential personalized customization in medical implants. In this study, in-situ synchrotron-based high-energy X-ray diffraction was employed to investigate the deformation behavior and stress-induced martensitic transformation (SIMT) of LPBF-fabricated polycrystalline NiTi under quasi-static uniaxial tension at varying strain rates. The results indicate that the printed NiTi alloy demonstrated a texture characterized by the coexistence of ⟨001⟩ and ⟨110⟩ austenitic orientations. The transformation behavior was highly dependent on both the strain rate. Notably, the (110) A planes showed a marked sensitivity to changes in lattice strain and the evolution of applied stress, whereas the (200)A planes exhibited a more stable response. Furthermore, an increased strain rate led to a more rapid rise in dislocation density.