Mechanical properties and underlying deformation mechanisms of a β-titanium alloy processed by laser powder bed fusion for biomedical applications

A low-elastic-modulus metastable β-Ti–Nb–Zr alloy was fabricated by Laser Powder Bed Fusion (LPBF) for potential biomedical applications. Post-heat treatment was applied to the as-built state, and the mechanical behaviors of both alloys were compared. The as-built alloy mainly consists of the β phase, with an ω phase. Synchrotron X-ray diffraction indicates that the ω phase is suppressed after heat treatment (550 °C for 1 h), and a small amount of α -HCP precipitates form within the β matrix. Tensile testing at room temperature shows discontinuous yielding with upper and lower yield stresses of 733 MPa and 711 MPa, followed by hardening that delays fracture. In situ TEM revealed screw dislocation cross-slip, causing localized deformation and softening. Strain hardening resumes with dislocation multiplication, leading to high ductility. The heat-treated alloy reaches only 21% of the as-built's elongation and deforms mainly via {332}〈113〉 twinning. Despite limited ductility, its elastic modulus is about 39±2 GPa, compared to 56±2 GPa for the as-built.