Microstructure characteristics and superelastic properties of novel Ti–Cr–Sn superelastic alloys

Microstructures, texture, lattice deformation strain, and superelastic properties of four kinds of near β type Ti–Cr–Sn novel superelastic alloys were systematically investigated, i.e., Ti-2.5Cr-8.5Sn, Ti-3.0Cr-7.5Sn, Ti-3.5Cr-7.0Sn, and Ti-4.0Cr-6.5Sn (at.%). All the alloys after the solution-treatment at 1273 K followed by water quenching consisted of equiaxed β single phase grains at room temperature in addition to athermal ω phase particles. Mechanical tests revealed the largest superplastic recovery strains (excluding elastic strain) of 4.0% in Ti-4.0Cr-6.5Sn alloy. This is partially due to the large lattice deformation strain ∼6.32% and its well-developed 112β⟨110⟩β texture component when tensile test exqmined along the rolling direction (RD). Moreover, up to 100 cyclic loading-unloading tensile tests revealed that both Ti-4.0Cr-6.0Sn and Ti-2.5Cr-8.5 Sn alloys maintained almost perfect and large shape recovery strain (including elastic strain) over 4.5% without any additional thermo-mechanical treatment. Besides, the starting stress for inducing martensitic transformation in Ti-4.0Cr-6.5Sn alloy kept higher than 200 MPa during the 100 cycles. Based on these superior superelastic properties, it is concluded that these Ti–Cr–Sn superelastic alloys become practical alternatives to replace Ti–Ni not only for biomedical applications but industrial applications.