A mechanical comparison of alpha and beta phase biomedical TiTa lattice structures

Abstract

Recent orthopaedic implant alloy design has focused on β-type Ti alloys, as the body centred cubic (BCC) crystal structure has the tendency to be characterised by a low elastic modulus. Nevertheless, the currently most used metal is Ti-6Al-4V, which mainly retains a hexagonal closed packed (HCP) crystal structure when produced by additive manufacturing. The benefits and disadvantages of the mechanical response of each crystal structure for implant applications is yet to be explored. Utilising the TiTa alloy system, low modulus Ti25Ta and Ti65Ta lattices were additively manufactured with opposing crystal structures of α′ martensite (HCP) and β grains (BCC). The lattices showed similar tensile, compressive and high cycle fatigue behaviour, indicating that the α' alloy was mechanically equal to the β alloy for implant applications. The mechanical properties of both the TiTa lattices were also superior to identically manufactured lattices in Ti-6Al-4V in both as-built and heat treated conditions.