Functional properties and microstructure of TiNi alloy during multiple martensitic transformations

The influence of multiple martensitic transformations on the functional properties and microstructure of the equiatomic TiNi alloy is considered. An analysis of mechanical tests showed that in the CG and UFG state in the Ti_50.0Ni_50.0 alloy as a result of thermal cycling with an increase in the number of cycles, a monotonic increase in the yield strength is caused by phase hardening. Moreover, in the UFG state, the yield strength increases by 185 MPa, which is 67.5 MPa more than the increase in σ_YS in the CG state. In this case, ductility remains at the level of 40%, which is somewhat lower than ductility in the CG state (∼ 60%). The phase yield stress and the estimated reactive stress of the CG and UFG states as a result of the TC also increase, with σ_reac UFG reaching 830 MPa. The increase in the yield strength of the CG state in an overgrown alloy is 113 MPa, while in the UFG it is 155 MPa, in addition, an increase in the estimated reactive stress and the reversible deformation with an increase in the number of thermal cycling cycles.