Effect of Cr additions on the phase constituent, mechanical properties, and shape memory effect of near-eutectoid Ti-4Au towards the biomaterial applications

A series study of the ternary near-eutectoid Ti-Au-Cr shape memory alloys (SMA) at the Ti-rich corner was explored in this work towards the applications of biomedical materials. Fundamental analysis, such as microstructures, phase constitutions, lattice parameters, and mechanical properties of the specimens, were examined along with their functional properties, such as shape memory effect (SME) and superelasticity (SE). Most of the alloys possess good cold-workability except for those with great amounts of precipitates of the brittle Ti3Au at the high Au addition specimens. The Ti-4Au-8Cr alloy excelled in strength while the Ti-2Au-8Cr alloy surpassed other alloys in ductility. Most of the specimens possess SME as well as pseu-doelasticity and/or superelasticity indicating the functionality of the Ti-Au-Cr alloys towards biomedical applications. The discrimination between the alpha'-martensite phase and the alpha ''-martensite phase was conducted by the TEM observation. The alpha'-martensite phase, which unexpectedly performed SME in this study was determined to locate exactly at the boundary of the alpha'-martensite regime and the alpha ''-martensite regime. The SME of the alloys, which were composed of the alpha'-martensite phase, were thus deduced to originate from the similarity of the alpha'-martensite and the alpha ''-martensite. (C) 2021 Elsevier B.V. All rights reserved.