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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 cexp as 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 c as 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 FROM AUTHOR]

The properties of the Ni50Ti47.5Hf2.5 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 AsSME = 137°C and AfSME = 150°C have been determined. These values are acceptable for creating the required depressurization device. The maximum εSME and ηSME 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. [ABSTRACT FROM AUTHOR]

The properties of an Ni49.5Ti48Hf2.5 high-temperature shape memory effect alloy are comprehensively studied on samples made of a 2.34-mm-thick strip after high-temperature vacuum annealing (850°C, 1 h). The elemental, phase compositions and structure of the alloy are analyzed. The results of studying the phase transformation temperatures and the mechanical and thermomechanical characteristics of the alloy are presented. The results of studying the local phase composition of the alloy samples demonstrate that their matrix is formed by a solid solution of alloy elements (Ti, Ni, Hf). X-ray diffraction analysis demonstrates that the main phase of the samples is titanium nickelide in the low-temperature TiNi martensitic state (B19') with a monoclinically distorted orthorhombic crystal lattice. The best average shape memory characteristics (εSME = 4.4%, ηSME = 53%) are obtained for alloy samples subjected to preliminarily induced total strain εt = 11% in the temperature Td range from –5 to 23°C at a strain rate ≈ 2.8 × 10–3 s–1. Here, the average temperatures of the onset and end of the main shape recovery are AsSME = 133°C and AfSME = 149°C. These thermomechanical characteristics are acceptable for the alloy chosen to create safety devices of, e.g., a pushing type. [ABSTRACT FROM AUTHOR]

The properties of Ti50Pd50 high-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 ≈ 1.2 × 10–3 s–1 for 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. [ABSTRACT FROM AUTHOR]

Integrated studies of the structure and microhardness of Ti50Pd40Ni10 alloy (at %) with a high-temperature shape memory effect have been carried out. The studies have been performed on alloy specimens cut from a rod 5.86 mm in diameter in the initial state and after various heat-treatment conditions. Data on the elemental and phase compositions, microstructure, grain size, and microhardness have been obtained. It has been suggested from the results of the studies of local phase composition of the alloy that ductility characteristics and, consequently, the shape memory effect of the specimens fabricated from a rod would be less than those of the specimens fabricated from a strip. It has been determined from the results of metallographic studies that the lowest microhardness of the rod alloy is intrinsic after annealing in vacuum at 850°C for 1 h and cooling with the furnace. Then, it could be suggested that residual strain and shape memory effect would be the greatest under these conditions. The results of structural studies of the Ti50Pd40Ni10 alloy (at %) will be considered by the authors in the development of various safety devices in nuclear power plants. [ABSTRACT FROM AUTHOR]