Orientation dependence of superelasticity in quenched high-nickel Ti-51.8Ni single crystals

The orientation dependence of the functional and mechanical properties of quenched Ti-51.8at.%Ni single crystals, undergoing a strain-glass transition upon cooling/heating was investigated. It was found that a compressive stress above 800 MPa leads to the B2-B19′ martensitic transformation (MT), regardless of orientation. In the high-strength [0 0 1]-orientation, superelasticity (SE) was observed at 203–248 K, with a reversible strain of 2.3%. Degradation of SE at deforming stresses σ > 1000 MPa was associated with the formation of {1 1 3}B2 twins during the reverse MT. In the low-strength 111--orientation, the formation of stress-induced B19′-martensite occurred simultaneously with the plastic deformation of the B2-phase (due to the formation of reorientation bands and dislocation slip) and a reversible strain was not observed.