OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 3 2022 Deformability of TiNiHf shape memory alloy under rolling with pulsed current Vladimir Stolyarov 1, a, *, Vladimir Andreev2, b, Roman Karelin2, 3, c, Umar Ugurchiev1, d, Vladimir Cherkasov3, e, Victor Komarov2, 3, f, Vladimir Yusupov2, g 1 Mechanical Engineering Research Institute of RAS, 4 M. Kharitonyevskiy Pereulok, Moscow, 101990, Russian Federation 2 Baikov Institute of Metallurgy and Materials Science, 49 Leninskiy Prospekt, Moscow, 119334, Russian Federation 3 National University of Science and Technology MISIS, 4/1 Leninskiy Prospekt, 119049, Russian Federation a https://orcid.org/0000-0001-7604-3961, vlstol@mail.ru, b https://orcid.org/0000-0003-3937-1952, andreev.icmateks@gmail.com, c https://orcid.org/0000-0002-4795-8668, rdkarelin@gmail.com, d https://orcid.org/0000-0003-2072-6354, umar77@bk.ru, e https://orcid.org/0000-0002-5450-3565, v.basenchikov@yandex.ru, f https://orcid.org/0000-0003-4710-3739, vickomarov@gmail.com, g https://orcid.org/0000-0002-0640-2217, vsyusupov@mail.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. 2022 vol. 24 no. 3 pp. 66–75 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2022-24.3-66-75 ART I CLE I NFO Article history: Received: 27 April 2022 Revised: 06 May 2022 Accepted: 18 June 2022 Available online: 15 September 2022 Keywords: Shape memory alloys Rolling Pulse current Structure Deformability Hardness Funding The study was carried out within the framework of the state task of IMET RAS No. 075-00715-22-00. ABSTRACT Introduction. The deformation capacity of materials is one of the main mechanical characteristics that determine the possibility of its production using various technological processes for metal forming. Among intermetallic compounds, a special role belongs to alloys with a high-temperature shape memory effect (SME) based on TiNi with the addition hafnium. Most of these alloys are not only diffi cult to deform, but also quite brittle. Therefore, the development of any technological schemes to increase the deformation capacity of these alloys is relevant. The purpose of the work: to study the deformation capacity and the possibility of using electric pulsed current during cold rolling of the TiNiHf alloy. This processing method has not previously been applied to these alloys. In this work, the deformation capacity during cold rolling of a strip 2 mm thick made of a hardto-deform high-temperature TiNi-based shape memory alloy with the addition of hafnium is studied. To increase the deformability, an external action in the form of a high-density pulsed current of more than 200 A/mm2 is investigated. The research methods are: X-ray analysis to assess the initial phase state; analysis of the evolution of true and engineering deformation to failure (appearance of visible macrocracks in the deformation zone); optical microscopy with magnifi cation from 50 to 100 and measurement of Vickers hardness at room temperature. Results and discussion. An increase in the deformability under the infl uence of a pulsed current compared to rolling without current and the achievement of a maximum strain of 1.7 (true) and 85% (engineering) are established. The initial coarse-grained equiaxed martensitic microstructure (50 μm) is transformed into a microstructure elongated along the rolling direction, while the hardness increases by 50%. The absence of noticeable structural changes and the observed hardening may indicate a nonthermal effect of the current in increasing the deformability. Thus, the results of the conducted studies indicate the prospects of the method of rolling with a current of a hard-to-deform TiNiHf shape memory alloy as a method of metal forming. For citation: Stolyarov V.V., Andreev V.A., Karelin R.D., Ugurchiev U.Kh., Cherkasov V.V., Komarov V.S., Yusupov V.S. Deformability of TiNiHf shape memory alloy under rolling with pulsed current. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2022, vol. 24, no. 3, pp. 66–75. DOI: 10.17212/1994-6309-2022-24.3-66-75. (In Russian). ______ * Corresponding author Stolyarov Vladimir V., D.Sc. (Engineering), Professor Mechanical Engineering Research Institute of RAS, 4 M. Kharitonyevskiy Pereulok, 101990, Moscow, Russian Federation Tel.: 8 (915) 294-69-41, e-mail: vlstol@mail.ru Introduction The deformability is one of the mechanical characteristics that determines the ability of solid materials to change its shape and size under the infl uence of external factors, including forming processes. This characteristic affects the operational behavior of the deformed material and is especially relevant for the development of production technologies associated with rolling, pressing, drawing, upsetting. For various
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