A comparative investigation for the effect of Mo and Nb on novel Ti–Zr-Hf based superelastic alloys

In this work, the newly developed biomedical superelastic (Ti–30Zr-13Hf)-2Mo–4Sn (at.%, Ti301324 for short) and (Ti–28Zr-12Hf)-8Nb–4Sn (at.%, Ti281284 for short) alloys are investigated by cyclic tensile tests, electron back-scattered diffraction (EBSD), transmission electron microscopy (TEM), and in situ synchrotron X-ray diffraction (SXRD) after solution treatment at 700 °C for 30 min. Both of the alloys reveal the same beneficial <110> β type texture and omega-free microstructure. However, the Ti301324 alloy displays recovery strain of 3.9 %, which is higher than the Ti281284 one (3.1 %). This improvement is due to the solid solution strengthening effect of Mo. Furthermore, the reversible stress-induced martensitic (SIM) α" transformation was evidenced by in situ SXRD intuitively, and Ti301324 specimen reveals favorable transformation strain than Ti281284 alloy. This study gives a good guidance to develop high-performance biomedical superelastic titanium alloys.