Research and development on Ni-free, Ti-based super-elastic
and shape memory alloys is still in progress. Selected Ni-free shape
memory alloys, which generally also exhibit super-elasticity, are
listed in Table 3 [99], along with selected Ni-free Ti alloys which
exhibit super-elasticity. They are broadly divided into four groups:
Ti–Nb system alloys [100–112], Ti–Mo system alloys [113–117],
Ti–Ta system alloys [118], and Ti–Cr system alloys [119]. These
are all b-type Ti alloys with a single metastable b phase with a suitable
stability to enhance deformation-induced martensite
formation.