International audienceAs expected from the alloy design procedure, combined Twinning Induced Plasticity (TWIP) and Transformation Induced Plasticity (TRIP) effects are activated in a metastable β Ti-12(wt.%)Mo alloy. In-situ Synchrotron X-ray diffraction (XRD), electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) observations were carried out to investigate the deformation mechanisms and microstructure evolution sequence. In the early deformation stage, primary strain/stress induced phase transformations (β->ω and β->α'') and primary mechanical twinning ({332}<113> and {112}<111>) are simultaneously activated. Secondary martensitic phase transformation and secondary mechanical twinning are then triggered in the twinned β zones. The {332}<113> twinning and the subsequence secondary mechanisms dominate the early stage deformation process. The evolution of the deformation microstructure results in a high strain hardening rate (~2GPa) bringing about high tensile strength (~1GPa) and large uniform elongation (> 0.38)

In this work, the superelastic behavior of a new metastable β Ti-20Zr-3Mo-3Sn (at.%) biomedical alloy displaying stress-induced α" martensitic transformation (SIM) was investigated by cyclic tensile tests, electron back-scattered diffraction (EBSD) and in situ synchrotron X-ray diffraction (SXRD) for 3 different solution treatment temperatures: 700°C, 800°C and 900°C. The EBSD observations revealed that the Ti-20Zr-3Mo-3Sn alloy showed a strong dependence of the solution treatment temperatures on crystallographic texture. SXRD diffraction profiles acquired under cyclic loading/unloading tensile tests clearly illustrated the reversible SIM α" transformation. In addition, the lattice parameters of β and SIM α" phases were measured for each cycle in order to establish the evolution of lattice parameters during the deformation and to calculate the maximum transformation strain for any crystallographic direction. A high recovery strain of 3.5% was obtained by tensile test after a solution treatment at 700°C for 30 minutes. This high recovery strain is due to the fact that the maximum transformation strain is obtained along the tensile direction displaying the favorable <011> β {100} β recrystallization texture. The performance of the Ti-20Zr-3Mo-3Sn alloy is discussed and compared with other superelastic alloys such as NiTi and (Ti-Nb)-based alloys.