Characterization of the stress-induced martensitic transformation in a Ti-Zr-Nb-Sn biomedical alloy manufactured by laser powder bed fusion

A new potentially biocompatible Ti-22Zr-7Nb-2Sn (at.%) alloy was prepared by laser powder bed fusion (L-PBF) directly from pure elemental powders ( in situ alloying ) . The manufactured alloy was characterized in its as-fabricated state by cyclic tensile tests, X-ray diffraction (XRD), transmission electron microscopy (TEM) observations and electron back-scattered diffraction (EBSD). The as-fabricated microstructure is dual-phased, composed of both β and α″ phases, with a majority of β phase. Cyclic tensile tests show high strain-hardening, with a maximum strain-hardening rate of approximately 14 GPa. The post deformation microstructure is studied to highlight the deformation mechanisms of the present alloy and exhibits a large fraction of stress-induced martensitic α″ phase, which formed from the parent β phase according to the standard orientation relationship (OR) during tensile test. The identification of the martensitic variants, their interfaces with the parent phase and the twinning relationships between them are reported in this study based on crystallographic investigations. In view of all these results, a deformation sequence of the Ti-22Zr-7Nb-2Sn (at.%) alloy is proposed.