Martensitic Transformations and Inelastic Properties of TiNi Alloy Undergoing abc Pressing at 300°C

The effect of multi-axis forging (abc pressing) at 300°C on the temperatures of martensitic transformations and inelastic properties (effects of superelasticity and the shape memory) is explored in Ti49.8Ni50.2 (at %) alloy samples. It is found that the temperature of the onset of direct martensitic transformation B2 → R remains virtually the same after abc pressing. This temperature is equal to 63 ± 1°C. At the same time, the temperature of the end of the direct martensitic transformation to the B19′ structure decreases by 41 ± 1°C. The temperatures of the beginning and the end of the reverse martensitic transformation B19′ → B2 decrease by 18 and 13°C, respectively. It is found that, after abc pressing at 300°C, the alloy samples retain inelastic properties, having values (regardless of the given true strain e) comparable with the value of the inelastic properties of the coarse-grained samples. In all samples under study, the maximum value of the reversible inelastic strain reaches ~18% and is observed at 16–24% of the determined plastic torsional strain.