Martensitic transformations and functional properties of thermally and thermomechanically treated Ti–Ni–Nb-based alloys

The aim of the present work is the detailed investigation of the structure, martensitic transformations and functional properties of the wide-hysteresis Ti–Ni–Nb-based shape memory alloys intended for the thermomechanical coupling (TMC) development. The 45Ti–45Ni–10Nb and 42.5Ti–46.5Ni–8Nb–3Zr (at.%) alloys have been studied. Zr addition results in martensitic hysteresis widening that promotes an improvement of the material functional properties. High-temperature thermomechanical treatment (HTMT) is an effective method for the optimization of Ti–Ni–Nb-based shape memory alloys properties. HTMT increases recovery strain and shape recovery rate as well as provides a favorable effect on the recovery stress generation and relaxation. The alloys compositions and treatments which allow designing the room-temperature-stored TMCs for tubes or pipes joints, reliable within the temperature range above −60 °C and easily dismantled when cooling in liquid nitrogen, have been proposed.