Orientation Dependence of Cyclic Stability of Superelasticity of Ti_50.2Ni_49.8 Alloy Single Crystals under Compression

The effect of marforming (low-temperature compression deformation of В19ꞌ-martensite at 203 K and subsequent annealing at 713 K for 0.5 h) on superelasticity (SE), temperature range of SE, and cyclic stability of superelastic behavior at 323 K are studied on [001]_В2 and \([\bar {1}12]\) _В2 single crystals of the Ti_50.2Ni_49.8 (at %) alloy under compression. It is shown that marforming leads to an increase in the offset yield strength σ_0.1 of the high-temperature В2-phase and to the development of SE, which was not observed in quenched crystals. The orientation dependence of the SE temperature range and the cyclic stability of superelastic behavior, which is determined by the orientation dependence of the σ_0.1 stresses of the В2-phase, is established. The maximum SE temperature range is 87 K, and the cyclic stability of superelastic behavior at a temperature of 323 K is found in the [001]_В2 orientation with a high σ_0.1 stress level of the В2-phase.