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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]

Abstract—The influence of annealing at 600°C on the mechanical and thermomechanical characteristics of a Ti50Pd30Ni20 alloy with high-temperature shape memory effect (SME) is studied. The best strength (σu = 1030 ± 140 MPa) and plastic ( = 11.5 ± 6.0%, δres = 6 ± 4%) characteristics have been obtained after annealing at 600°C. The maximum thermally recoverable strain (εSME = 4.3%) and the maximum degree of shape recovery (ηSME = 67%) are achieved after annealing at 600°C after preliminary induced tensile deformation at temperatures td =235–230°C and a strain rate ≈ 2.8 × 10–3 s–1; in this case, the reverse martensitic transformation temperatures characterizing the main shape recovery are AsSME = 220°C and AfSME = 249°C. Taking into account the studies carried out before, we found that the martensitic transformation temperatures increase almost linearly and, conversely, the SME and the degrees of shape recovery decrease as the titanium nickelide is alloyed with palladium in the content range from 30 to 50 at %. Linear regression equations are derived. The results obtained are used for designing safety devices of, e.g., crosscutting and pushing types. [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 a Ti50Pd40Ni10 alloy (at %) with a high-temperature shape memory effect (SME) are studied on samples manufactured from a 2.04-mm-thick strip after various annealing and strain-creation conditions. Data on the elemental and local phase compositions, the grain sizes and the microhardness, the phase transformation temperatures, and the mechanical and thermomechanical characteristics have been obtained. The best average shape memory characteristics (εSME = 4.3%, ηSME = 0.57) are found to be obtained for the alloy samples subjected to vacuum annealing (600°C, 1 h) on heating to 500°C (stable end of SME) after the tensile strain preliminarily induced at a temperature of 380–370°C (after heating to 450°C) at a rate ≈ 3.1 × 10–3 s–1 and the same degree of total induced strain εt = 11%. In this case, the average temperatures of the start and finish of the main shape recovery are As SME = 418°C and Af SME = 435°C, respectively. These thermomechanical characteristics are acceptable for an alloy chosen for creation of safety devices, e.g., of a cutting type, in which thermosensitive elements have a tray shape. [ABSTRACT FROM AUTHOR]

The properties of the Ti50Pd40Ni10 (at %) alloy showing the high-temperature shape memory effect are studied in detail using samples made of a 5.86 mm bar under various conditions of annealing and induced deformation. The data on the phase transformation temperatures and the mechanical and thermomechanical characteristics of the alloy are obtained. The range of phase transformations occurs in the range from Mf = 360°C to Af = 439°C. These are acceptable values for creating the required safety device. The maximum values of the shape memory effect and the degree of shape recovery are 2.4 and 43%, respectively. This is not sufficient to create a functional security device. Thus, the selection of annealing modes and conditions for inducing deformation are not a successful way to substantially increase the thermomechanical characteristics of the alloy. Higher values of thermomechanical characteristics have previously been obtained using samples cut from a strip with a thickness of 2.04 mm. Therefore, operating elements of safety devices designed for nuclear power facilities will be further manufactured from the strip. [ABSTRACT FROM AUTHOR]

Abstract—Complex studies of the properties of the Ti50Pd40Ni10 alloy (at %) with a high-temperature shape memory effect have been performed using specimens prepared from a 5.86-mm bar in the initial annealed state. Information on the temperatures of phase transformations and mechanical and thermomechanical characteristics of the alloy have been obtained. The maximum values of the shape-memory effect and of the degree of shape recovery were 1.5 and 21%, respectively. This is insufficient to create workable safety devices at this stage. The thermomechanical characteristics determined in this study are comparable with the data we obtained earlier on samples cut out from a 2.04-mm-thick strip. In spite of the rather low values of the thermomechanical characteristics obtained at the first stage of research, this alloy is a promising material, and if obtaining optimum values of working characteristics by varying manufacturing conditions and regimes of heat treatment and deformation, it can be used to create working elements of various safety devices for objects of nuclear power engineering. [ABSTRACT FROM AUTHOR]