OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Martensitic transformations in TiNi-based alloys during rolling with pulsed current Anna Misochenko a, * A.A. Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences, 4 Maly Kharitonievsky per., Moscow, 101990, Russian Federation a https://orcid.org/0000-0002-2885-1996, ls3216@yandex.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2025 vol. 27 no. 2 pp. 255–269 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2025-27.2-255-269 ART I CLE I NFO Article history: Received: 11 December 2024 Revised: 09 January 2025 Accepted: 10 April 2025 Available online: 15 June 2025 Keywords: TiNi-based alloys Pulsed current Current-assisted rolling Martensitic transformations X-ray diffraction analysis Austenite stabilization Cyclic martensitic transformation ABSTRACT Introduction. Shape memory alloys based on TiNi possess a set of properties, including biocompatibility, corrosion resistance, low density, high specific strength, thermal stability, shape memory effect, and superelasticity. A significant number of studies are currently dedicated to various deformation methods of processing such materials, aiming to enhance their mechanical properties and shape memory characteristics. One such method is plastic deformation with the simultaneous application of pulsed current. Since the shape memory properties in TiNi-based alloys are due to the presence of thermoelastic martensitic transformations, the combined effect of deformation and current on these transformations is of particular interest. The purpose of this work is to investigate the characteristics of thermal and deformation-induced martensitic transformations in Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys during rolling with simultaneous application of pulsed current. Research methods. The paper analyzes samples of Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys after rolling with pulsed current at a density of 100 A/mm², a pulse duration of 100 μs, a pulse ratio of 10 to various strain levels (ε = 0; 0.4; 0.8; 1.2). The study of the staging of martensitic transformations was carried out using differential scanning calorimetry at a heating/cooling rate of 10 °C/min in the temperature range of −150 to +150 °C. The phase composition was studied by X-ray diffraction analysis using Cu-Kα radiation at U = 40 kV and I = 40 mA in the angular range of 2θ=15 to 100 ° with a step size of Δθ = 0.05° and an exposure time of 5 s. Results and discussion. The results show that current-assisted rolling leads to the manifestation of a two-stage direct martensitic transformation during cooling in both alloys. Furthermore, increasing the strain level broadens the temperature range of the R-phase existence. The possibility of stabilizing the high-temperature austenitic B2 phase in the Ti49.2Ni50.8 alloy, as well as the emergence of a cyclically occurring deformation-induced “martensite-austenite-martensite” transformation in the Ti50.0Ni50.0 alloy, are demonstrated. Possible mechanisms for these features are discussed. For citation: Misochenko A.A. Martensitic transformations in TiNi-based alloys during rolling with pulsed current. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2025, vol. 27, no. 2, pp. 255–269. DOI: 10.17212/19946309-2025-27.2-255-269. (In Russian). ______ * Corresponding author Misochenko Anna., Ph.D. (Engineering), Senior Researcher A. A. Blagonravov Mechanical Engineering Research Institute of the Russian Academy of Sciences, 4 Maly Kharitonievsky per., 101990, Moscow, Russian Federation Tel.: +7 916 361-48-63, e-mail: ls3216@yandex.ru Introduction TiNi-basedshapememoryalloyspossessauniqueset ofproperties, includinglowdensity, biocompatibility, corrosion resistance, high specific strength, ductility, and strain reversibility under heating (shape memory) and upon unloading without heating (superelasticity) [1]. A large number of studies are currently devoted to various deformation methods in order to improve the mechanical and shape memory properties of such materials [2-4]. However, traditional metal forming processes without heating often lead to the destruction of these alloys. Therefore, the current standard technology for manufacturing semi-finished products from these alloys involves the use of warm and hot deformation [5, 6]. In turn, increasing the deformation temperature leads to a decrease in strength [6, 7]. Some works [8, 9] indicate that it is possible to avoid this problem when using pulsed electric current during plastic deformation, which leverages the electroplastic
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