Effects of thermomechanical process on the microstructure and mechanical properties of a fully martensitic titanium-based biomedical alloy

Thermomechanical treatments have been proved to be an efficient way to improve superelastic properties of metastable beta type titanium alloys through several studies. In this paper, this treatment routes, already performed on superelastic alloys, are applied to the Ti-24Nb alloy (at%) consisting of a pure martensite alpha '' microstructure. By short-time annealing treatments performed on the heavily deformed material, an interesting combination of a large recoverable strain of about 2.5%, a low elastic modulus (35 GPa) and a high strength (900 MPa) was achieved. These properties are shown to be due to a complex microstructure consisting of the precipitation of nanoscale (alpha+omega) phases in ultrafine 13 grains. This microstructure allows a superelastic behavior through stress-induced alpha '' martensitic transformation. In this study, the microstructures were characterized by X-ray diffraction and transmission electron microscopy and the evolution of the elastic modulus and the strain recovery as a function of the applied strain was investigated through loading-unloading tensile tests. (C) 2012 Elsevier Ltd. All rights reserved.