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Abstract: The structure and microhardness of the Ti50Pd30Ni20(at %) alloy with a high-temperature shape memory effect have been comprehensively studied. The investigations have been carried out on the alloy samples cut from a 2.09-mm-thick strip in the initial state and after heat treatment under different conditions. Data on the elemental and phase compositions, microstructure, grain size, and microhardness have been obtained. It has been found that the main phase of the Ti50Pd30Ni20(at %) alloy in the initial state and after heat treatment is a solid solution based on the TiPd (B19) phase in a low-temperature martensitic state with an orthorhombic crystal lattice; Ni is introduced in the TiPd (B19) phase with the formation of a solid solution with it. Heat treatment barely changes the parameters aexp, bexp, and cexpas compared with the initial state; i.e., the crystal lattice distortions caused by defects are minor, and the changes in the crystal lattice parameters a, b, and cas compared with the reference values are caused mainly by the deviation of the alloy composition from the stoichiometric one and by the formation of a solid solution based on the TiPd (B19) phase.

Abstract: The properties of the Ni50Ti47.5Hf2.5alloy 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 AsSME= 137°C and AfSME= 150°C have been determined. These values are acceptable for creating the required depressurization device. The maximum εSMEand ηSMEvalues 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.

Abstract: The properties of Ti50Pd50high-temperature shape memory alloy were studied comprehensively on samples made from a strip with thickness of 4.14 mm in the initial state and after various annealing modes and deformation induced conditions. The data on elemental and local phase composition, the structure, the microhardness, the temperatures of phase transformations, and the mechanical and thermomechanical properties were obtained. We found that the best average shape memory values εSME= 2.5% and ηSME= 0.29 were obtained for alloy samples after annealing (730°C, 1 min → quenching in water → annealing at 400°C, 1 h → cooling with furnace) upon heating to a temperature of T= 650°C (stable end of SME manifestation) after preliminary induced tensile deformation at TD= (540–530)°C (after heating to T= 620°C) at a rate of \documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\dot {\varepsilon }$$\end{document}≈ 1.2 × 10–3s–1for the same total induced strain εtot= 10%. In this case, the temperatures of start and finish of the main form recovery are Аs SME= 568°С and Аf SME= 579°С. These shape recovery temperatures are acceptable for an alloy used for safety devices. The size of the shape memory effect and the degree of its recovery, however, are insufficient to create safety devices, for example, a cutting type, in which the temperature-sensitive elements will have a plate shape.