Mechanical and Thermomechanical Characteristics of the Ni₅₀Ti_47.5Hf_2.5 Alloy with a High-Temperature Shape Memory Effect

The properties of the Ni₅₀Ti_47.5Hf_2.5 alloy with a high-temperature shape memory effect have been comprehensively studied on samples made from a 2.34-mm-thick strip in the initial state and after high-temperature annealing in vacuum. Data on the elemental and phase compositions and structural state have been obtained. The results of investigations of the phase transformation temperatures and the mechanical and thermomechanical characteristics of the alloy are reported. Using annealing and selecting the strain-inducing conditions, the shape recovery temperatures A_{s SME} = 137°C and A_{f SME} = 150°C have been determined. These values are acceptable for creating the required depressurization device. The maximum ε_SME and η_SME values have been found to be 3.4 and 43%, respectively. These are not very large values for creating an efficient depressurization device for nuclear power plants. The desired displacement values in such a device can be obtained by optimizing the geometry of a thermosensitive element.