Mechanical properties and microstructures of β Ti–25Nb–11Sn ternary alloy for biomedical applications

The mechanical properties and microstructures of β Ti–25%Nb–11%Sn ternary alloy rods were investigated for biomedical applications as a function of heat treatment temperature after swaging by an 86% reduction in cross-section area. An as-swaged rod consisting of a β (bcc) single phase shows a low Youngʹs modulus of 53 GPa, which is interpreted in terms of both the metastable composition of the β alloy undergoing neither an athermal ω transformation nor a deformation-induced ω transformation and < 110>texture development during swaging. Heat treatment at 673 K (400 °C) for 2 h leads to a high strength of approximately 1330 MPa and a high spring-back ratio of yield stress to Youngʹs modulus over 15 × 10− 3, with acceptable elongation. This high strength is attributable to needle-like α precipitates, which are identified by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and high-resolution electron microscopy (HREM).