Short-term annealing treatment on wide-temperature-range superelastic cycle and microstructure of Ti-11Nb-18Zr-3Sn alloy

In this study, the effects of short-term annealing treatment on the microstructure, mechanical properties and superelasticity of a Ti-11Nb-18Zr-3Sn alloy were investigated by electron backscatter diffraction (EBSD), transmission electron microscopy (TEM) and temperature-varying tensile test. The cold-rolled foil underwent annealing at temperatures ranging from 753 K to 1023 K. All annealed specimens had β as the dominant phase at room temperature, with a minor α phase detected in the 753 K and 823 K samples. The annealed alloy featured a bimodal grain size distribution and a strong {hkl}_β< 101̅>_β-type recrystallization texture. Except for the 753 K-annealed specimen, all other specimens showed a double yielding tension phenomenon at room-temperature. Ten superelastic cyclic tests were conducted on the alloy within the temperature range of 153 K to 373 K. The specimen annealed at 823 K exhibited favorable superelasticity and cyclic stability, with a superelastic strain of 3.8% achieved at 273 K. This excellent performance is mainly attributed to its favorable preferred orientation and stable microstructure.