Maximisation of the ratio of microhardness to the Young's modulus of Ti-12Mo-13Nb alloy through microstructure changes

Alloys for orthopaedic and dentistry applications require high mechanical strength and a low Young's modulus to avoid stress shielding. Metastable beta titanium alloys appear to fulfil these requirements. This study investigated the correlation of phases precipitated in a Ti-12Mo-13Nb alloy with changes in hardness and the Young's modulus. The alloy was produced by arc melting under an argon atmosphere, after which, it was heat treated and cold forged.. Two different routes of heat treatment were employed. Phase transformations were studied by employing X-ray diffraction and transmission electron microscopy. Property characterisation was based on Vickers microhardness tests and Young's modulus measurements. The highest ratio of microhardness to the Young's modulus was obtained using thermomechanical treatment, which consists of heating at 1000 degrees C for 24 h, water quenching, cold forging to reduce 80% of the area, and ageing at 500 degrees C for 24 h, where the final microstructure consisted of an alpha phase dispersed in a beta matrix. The alpha phase appeared in two different forms: as fine lamellas (with 240 +/- 100 nm length) and massive particles of 200-500 nm size. (c) 2013 Elsevier B.V. All rights reserved.