Vol. 27 No. 2 2025 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.
OBRABOTKAMETALLOV Vol. 27 No. 2 2025 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Ukraine: Sergiy V. Kovalevskyy, D.Sc. (Engineering), Professor, Vice Rector for Research and Academic Aff airs, Donbass State Engineering Academy, Kramatorsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary
Vol. 27 No. 2 2025 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Sundukov S.K., Nigmetzyanov R.I., Prikhodko V.M., Fatyukhin D.S., Koldyushov V.K. Comparison of ultrasonic surface treatment methods applied to additively manufactured Ti-6Al-4V alloy................................................................ 6 Kate N., Kulkarni A.P., Dama Y.B. A comparative evaluation of friction and wear in alternative materials for brake friction composites............................................................................................................................................................... 29 Naumov S.V., Panov D.O., Sokolovsky V.S., Chernichenko R.S., Salishchev G.A., Belinin D.S., Lukianov V.V. Microstructure and mechanical properties of Ti2AlNb-based alloy weld joints as a function of gas tungsten arc welding parameters............................................................................................................................................................................. 43 Jatti V.S., Singarajan V., SaiyathibrahimA., Jatti V.S., KrishnanM.R., Jatti S.V. Enhancement of EDM performance for NiTi, NiCu, and BeCu alloys using a multi-criteria approach based on utility function................................................ 57 Stelmakov V.A., Gimadeev M.R., Nikitenko A.V. Ensuring hole shape accuracy in fi nish machining using boring...... 89 EQUIPMENT. INSTRUMENTS Patil N., Agarwal S., Kulkarni A.P., Saraf A., Rane M., Dama Y.B. Experimental investigation of graphene oxide-based nano cutting fl uid in drilling of aluminum matrix composite reinforced with SiC particles under nano-MQL conditions............................................................................................................................................................................. 103 Gimadeev M.R., Stelmakov V.A., Nikitenko A.V., Uliskov M.V. Prediction of surface roughness in milling with a ball end tool using an artifi cial neural network................................................................................................................. 126 Osipovich K.O., Sidorov E.A., Chumaevskii A.V., Nikonov S.N., Kolubaev E.A. Manufacturing conditions of bimetallic samples based on iron and copper alloys by wire-feed electron beam additive manufacturing......................... 142 Babaev A.S., Savchenko N.L., Kozlov V.N., Semenov A.R., Grigoriev M.V. Performance of Y-TZP-Al2O3 composite ceramics in dry high-speed turning of thermally hardened steel 0.4 C-Cr (AISI 5135)...................................................... 159 MATERIAL SCIENCE Sokolov R.A., Muratov K.R., Mamadaliev R.A. Morphological changes of deformed structural steel surface in corrosive environment......................................................................................................................................................... 174 Chernichenko R.S., Panov D.O., Naumov S.V., Kudryavtsev E.A., Salishchev G.A., Pertsev A.S. Eff ect of heterogeneous structure on mechanical behavior of austenitic stainless steel subjected to novel thermomechanical processing............................................................................................................................................................................. 189 Panov D.O., Chernichenko R.S., Naumov S.V., Kudryavtsev E.A., Salishchev G.A., Pertsev A.S. Eff ect of cold radial forging on structure, texture and mechanical properties of lightweight austenitic steel................................................ 206 Deshpande A., Kulkarni A.P., Anerao P., Deshpande L., Somatkar A. Integrated numerical and experimental investigation of tribological performance of PTFE based composite material.................................................................... 219 Vorontsov A.V., Panfi lov A.O., Nikolaeva A.V., Cheremnov A.V., Knyazhev E.O. Eff ect of impact processing on the structure and properties of nickel alloy ZhS6U produced by casting and electron beam additive manufacturing........ 238 Misochenko A.A. Martensitic transformations in TiNi-based alloys during rolling with pulsed current........................... 255 EDITORIALMATERIALS 270 FOUNDERS MATERIALS 279 CONTENTS
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
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 effect (EPE). Studies on the application of EPE include rolling [10, 11], drawing [12], bending [13], microforming [12, 14], extrusion [15], and compression [16]. However, deformation behavior studies of various materials (pure metals and alloys) under tension are the most widely used [14, 17]. The specific deformation behavior of shape memory alloys, and their differences from traditional metals under tension with current, is detailed in [8, 18]. Studies on TiNi samples during rolling with current have shown an increase in deformability [19, 20] and mechanical properties [21]. In addition, it has been shown that it is possible to obtain a nanostructure (NS) [19] and increase the reversible strain and superelasticity [22] by using pulsed current-assisted rolling. The formation of NS is also possible in these alloys by using electric pulse treatment instead of traditional post-deformation annealing [23]. The specific effects of the electric current on the structure in various deformation schemes in different metals and alloys are described in [24, 25]. It is noted that the supply of electrical energy usually leads to structural changes, such as a decrease in dislocation density [26], the appearance of twins [27], dynamic recrystallization [28], grain refinement [29], the evolution of crystallographic texture [30], and the formation of oriented microstructures [31, 32], as well as particle redistribution and aging [33]. However, in shape memory alloys, the current can also affect the martensitic transformations (MTs). The possibility of controlling phase transformations by using current during rolling is shown in [34]. This paper compares the appearance of MTs in TiNi alloy after cold rolling and pulsed current-assisted rolling. At the same time, there is a lower intensity of deformation processes (relaxation mechanism) when using electrical current. For example, it has been shown that cold rolling can lead to MT suppression, while using current at the same strain leads to its manifestation. Although the heating during rolling with current of TiNi alloys (at a density of no more than 100 A/ mm2, a rate of 5 cm/sec, and a sample length of 10 cm) does not exceed 50-70 °C [35], it is localized and insignificant for the dynamic recrystallization processes. However, this temperature can have a significant effect on the MTs, which are the main characteristics of shape memory alloys. The purpose of thiswork is to study the features of thermal and strain-inducedmartensitic transformations in TiNi-based alloys during rolling with electrical current. To achieve this purpose, the following tasks were solved during the research: – analyzing thermal martensitic transformations in Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys after pulsed currentassisted rolling to various strains using calorimetry; – analyzing deformation-induced martensitic transformations in Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys during pulsed current-assisted rolling using X-ray diffraction phase analysis; – analyzing structural states in Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys during pulsed current-assisted rolling. Research methods The objects of the study were hot-rolled bars with a diameter of 6 mm and a length of 100 mm, made from Ti50.0Ni50.0 and Ti49.2Ni50.8 alloys. The average grain size in the initial state was 30 μm for Ti50.0Ni50.0 and 60 μm for Ti49.2Ni50.8. After quenching from 800 °C in water, the alloys exhibited a predominant structure of B19’ martensite and B2 austenite, respectively, at room temperature (Tr). The characteristic temperatures of the martensitic transformations are shown in Table. The samples were subjected to rolling with electrical current at room temperature until they reached true strains of ε = 0.4, 0.8, and 1.4 (ε = ln(S0/Sf), where ε is the true strain, and S0 and Sf are the initial and final cross-sectional areas before and after rolling, respectively). Rolling was carried out on a rolling mill with calibrated rolls, using a single compression of 50 μm per pass and a rolling rate of 5 cm/s. The caliber sizes ranged from 1 to 7 mm. The rolling mill was equipped with a pulsed current generator. The current pulses were applied to the deformation zone using a sliding contact (negative pole) and to one of the rolls (positive pole), as shown in Fig. 1, with a frequency of 1,000 Hz and a duty cycle of 10. The amplitude current density was j = 100 A/mm2, and the pulse duration was 100 × 10−6 s. Sample heating was monitored using an alumel-chromel thermocouple while passing current without deformation. The temperature increase was no more than 50-70 °C. The sample was under current for no more than 2 seconds. After each pass, the
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Characteristic temperatures of martensitic transformations Alloy Initial processing Direct martensitic transformation C2→B19ˊ Reverse martensitic transformation B19ˊ →C2 Phase composition at room temperature Ms, °С Mf, °С As, °С Af, °С Ti49.2Ni50.8 Quenching (water) 800 ºС (1 hour) −5 ̊ −37 −5 17 austenite C2 Ti50.0Ni50.0 45 25 58 77 martensite C19ˊ Ms, °С – the direct martensitic transformation (B2→B19’) start temperature; Mf, °С – the direct martensitic transformation finish temperature; As, °С – the reverse martensitic transformation (B2→B19’) start temperature; Af, °С – the reverse martensitic transformation finish temperature. samples were cooled in water to avoid additional current heating. Post-deformation annealing, when necessary, was carried out at 450 °C for 1 hour after rolling. Thermal martensitic transformation temperatures were studied by differential scanning calorimetry (DSC) using a Mettler Toledo 822e apparatus. Calorimetric curves were obtained in the temperature range from −150 to 150 °C with a heating/cooling rate of 10 °C/min. Strain-induced martensitic transformations were studied by performing phase analysis on the samples after rolling with current to different strains. X-ray diffraction phase analysis was performed using an ARL X’TRA X-ray diffractometer (Switzerland) with Cu Kα radiation in the angle range 2θ = 15-100° with a step size of Δθ = 0.05° and an exposure time of 5 s at a voltage U = 40 kV and a current I = 40 mA. Qualitative phase assessment was carried out using the WinXRD computer software package (ARL X’tra software) by comparing it with the database of the International Centre for Diffraction Data (ICDD) PDF-2 [36]. Structural studies after rolling were carried out by transmission electron microscopy (TEM) using a high-resolution JEM 2100 microscope from JEOL (Japan) at a maximum accelerating voltage of 200 kV. Results and discussion The calorimetric studies of the Ti50.0Ni50.0 alloy after pulsed current-assisted rolling and annealing at 450 ℃ showed the presence of a two-stage MT with an intermediate R-phase (Fig. 2, a). This phase is common in nickel- enriched alloys [37], but some authors observe it in Ti50.0Ni50.0 alloys and attribute its presence to high internal stresses, for example, after thermal cycling [38] or plastic deformation [39]. In the Ti49.2Ni50.8 alloy, the R-phase is observed immediately after annealing in the undeformed state, and it is associated with the presence of Ti3Ni4 particles [37]. While there is no shift in the B2→R MT start temperatures, a shift in the R→B19’ start temperature is noticeable (Fig. 2, b). This effect, where the pulsed current expands the R-phase temperature range, is also observed when comparing MTs with the initial undeformed state. Acharacteristic feature of TiNi-based alloys is that MTs manifest not only during cooling and heating but also during deformation [37]. According to X-ray diffraction analysis, all peaks in the diffraction pattern of the Ti50.0Ni50.0 alloy in the initial quenched state correspond to the B19’ martensitic phase with a monoclinic lattice (Fig. 3, a). Cold rolling without current leads to a reverse martensitic transformation. Consequently, Fig. 1. Schematic of current supply circuit: 1 – mill rolls; 2 – cylindrical sample; 3 – feed table (sliding contact); 4 – pulsed current source; 5 – current lines
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 a b Fig. 2. Phase transitions in Ti50.0Ni50.0 (a) and Ti49.2Ni50.8 (b) alloys after current-assisted rolling in the annealed state (450 °C) a b Fig. 3. X-ray diffraction analysis results for Ti50.0Ni50.0 alloy after quenching (a) and cold rolling without current to ε=0.7 (b) with the overlay of tabular data corresponding to the C19ˊ phase (green lines)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 B2 austenite becomes the main phase, although martensitic peaks are present in small amounts (Fig. 3, b). This reverse MT is typical for the alloy in the martensitic state after large strain [40], and it is associated with an increase in dislocation density, which stabilizes the austenite [41]. The reverse transformation from martensite to austenite induced by strain was first observed in [42] and later confirmed in [43]. This transformation is observed after large plastic deformations and precedes the onset of amorphization. The authors attribute the phenomenon to a change from sliding and twinning mechanisms to rotational deformation modes. According to [40], the B2 phase is more resistant to large strain, while the B19’ phase is susceptible to disordering with the accumulation of crystalline structure defects. The reverse strain-induced MT, “martensite B19’ → austenite B2” is also observed after pulsed currentassisted rolling to a small strain (ε = 0.4) in the Ti50.0Ni50.0 alloy. The B2 phase becomes the dominant phase (Fig. 4). In addition to the reasons mentioned above, it should be noted that short-term, localized electrical heating is possible in this study. This localized heating may be sufficient to induce the “martensite B19’ → austenite B2” transformation, because the characteristic temperatures of MTs are sensitive to even small amounts of heat, and the Af temperature after rolling does not exceed 58 °C (Fig. 2, a). A further increase in strain up to ε = 0.8 in the Ti50.0Ni50.0 alloy during pulsed current-assisted rolling leads to a stress increase in the newly formed austenitic phase. The accumulation of these stresses provides a mechanism for the direct MT (austenite B2 → martensite B19’) to occur. Concurrently, there is a noticeable increase in the relative intensity of the martensitic diffraction pattern peaks, indicating an increasing proportion of the martensitic phase (Fig. 4). A subsequent increase in strain to ε = 1.4 again results in the main peak from the B2 phase becoming the most pronounced. This indicates a reverse straininduced MT from the previously formed martensite, themechanisms of which are dominated by the thermal action of the current. Thus, a cyclical martensitic transformation is observed in the Ti50.0Ni50.0 alloy during pulsed current-assisted rolling. The underlying reason is the alternating dominance of deformation mechanisms (stress increase in the austenitic phase due to strain) and heating from the pulsed current. In the Ti50.0Ni50.0 alloy, B2 austenite remained the dominant phase during pulsed current-assisted rolling, as it was in the initial quenched state (Fig. 5). There was no evidence of strain-induced martensite, which is typically observed in Ni-rich alloys during deformation [37]. Such strain-induced martensite usually results from a shift in the reverse MT temperatures to higher values (the effect of martensite stabilization by preliminary deformation [44]). A possible reason for its absence during rolling with current may be short-term, localized heating. Apparently, in this case, the thermal effect of the current dominates the mechanisms of strain-induced martensite formation, leading to high-temperature B2 austenite stabilization. A notable feature of the diffraction patterns from samples after rolling with current is the broadening of the main B2 (110) peak (Fig. 5, b, inset). This broadening is due to an increase in defects with increasing strain, as well as the presence of a pronounced peak corresponding to titanium oxides. In this case, the broadening of the main peak is logically associated with an increase in microstrains in the crystal lattice due to deformation. Oxide particles are frequently observed and studied by other authors in shape memory alloys [37, 45]. These particles enter the alloy during the smelting stage and are almost always present in Fig. 4. X-ray diffraction analysis results for Ti50.0Ni50.0 alloy after current-assisted rolling to various strain levels (ε)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 a b Fig. 5. X-ray diffraction analysis results for Ti49.2Ni50.8 alloy after quenching from 800 °C in water (a) and currentassisted rolling to ε=0.4 (b) with an overlay of tabular data corresponding to the B2 phase (red lines) and Ti4Ni2O particles (green lines); inset: comparison of the broadening of the main B2 (110) peak after quenching (blue) and current-assisted rolling, ε=0.4 (grey) its composition. The broadening of the corresponding X-ray peak may indicate their crushing by pulsed current-assisted rolling, but the thermal effect of the current is insufficient to dissolve them. Microstructural studies using TEM reveal significant fragmentation of the initial grains after pulsed current-assisted rolling up to ε = 0.4 in the Ti49.2Ni50.8 alloy (Fig. 6, a). Deformation shear bands are observed within the structure, primarily oriented along the rolling direction. The thickness of these bands ranges from approximately 500 nm (most commonly observed) (Fig. 6, b) to 30 nm (Fig. 6, c). After straining to ε = 1.4, the microstructure exhibits a similar grain morphology but is more homogeneous. In this condition, thin shear bands (approximately 20-30 nm thick) are observed within wider (400-500 nm) deformation bands (Fig. 6, d). Fig. 7 presents the TEM results for the Ti50.0Ni50.0 alloy during pulsed current-assisted rolling up to ε = 0.8 and 1.4. These results indicate that deformation in this alloy occurs through twinning of the initial martensitic plates. The bright-field structure image after straining to ε = 0.8 is characterized by the presence of thin (20-30 nm) deformation bands. The electron diffraction pattern exhibits double reflections (Fig. 7, a). As strain increases to ε = 1.4, the deformation bands become even thinner, reaching thicknesses of less than 10 nm. The electron diffraction pattern corresponding to this state is characterized by reflections that are elongated along a circle, indicating strong lattice distortions after pulsed current-assisted rolling. The arrangement of the rings is typical for the B2 austenite phase; however, some areas exhibit martensitic reflections (reflections with similar interplanar distances near (110)) (Fig. 7, b). A comparison of the deformation process during pulsed current-assisted rolling for the TiNi-based alloys, considering their initial austenitic and martensitic structures, reveals that the Ti50.0Ni50.0 alloy undergoes more intense deformation. This observation is supported by the results of X-ray diffraction analysis. Thus, a characteristic feature of structure formation in the Ti50.0Ni50.0 alloy is the cyclical nature of the direct and reverse “martensite → austenite → martensite” transformations during pulsed currentassisted rolling. A possible explanation for this phenomenon is the alternating dominance of strain-induced martensitic transformation mechanisms and the localized influence of the thermal action of the current on the characteristic martensitic transformation temperatures. In contrast, a special characteristic of the effect of pulsed current during rolling on martensitic transformations in the Ti49.2Ni50.8 alloy is the absence of strain-induced martensite B19’ and the stabilization of the high-temperature austenitic B2 phase. These distinct features of MT manifestation can be utilized to control the structural and phase state of shape memory alloys in order to maximize functional properties such as reversible strain, recovery stress, and superelasticity.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 a b c d Fig. 6. Transmission electron microscopy images of Ti49.2Ni50.8 alloy after current-assisted rolling to ε=0.4 at various magnifications: ×6000 (a), ×8000 (b), ×30000 (c); and to ε =1.4 (d) a b Fig. 7. Transmission electron microscopy images of Ti50.0Ni50.0 alloy during current-assisted rolling: to ε = 0.8 (a); to ε = 1.4 (b)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 Conclusion – Pulsed current-assisted rolling and post-deformation annealing at 450 ℃ alters the direct thermal martensitic transformation pathway upon cooling, from B2 → B19’ to B2 → R → B19’, in both the initially single-phase martensitic (Ti50.0Ni50.0) and austenitic (Ti49.2Ni50.8) alloys in the quenched state. Increasing the strain during pulsed current-assisted rolling expands the temperature range over which the R-phase exists. – A cyclic strain-induced “martensite → austenite → martensite” transformation was detected in the Ti50.0Ni50.0 alloy during pulsed current-assisted rolling. This behavior is attributed to the alternating dominance of deformationmechanisms and the localized thermal influence of the current on the characteristic martensitic transformation temperatures. – The effect of pulsed current-assisted rolling on martensitic transformations in the Ti49.2Ni50.8 alloy is characterized by the absence of strain-induced B19’ martensite and the stabilization of the high-temperature austenitic B2 phase. References 1. Brailovski V., Prokoshkin S., Terriault P., Trochu F. Shape memory alloys: fundamentals, modelling and applications. Montreal, University of Quebec, 2003. 844 p. 2. Tsuchiya K., Ahadi A. Anomalous properties of TiNi processed by severe plastic deformation. Sun Q., Matsui R., Takeda K., Pieczyska E. (eds.). Advances in Shape Memory Materials. Advanced Structured Materials, vol. 73. Cham, Springer, 2017, pp. 191–201. DOI: 10.1007/978-3-319-53306-3_14. 3. Andreev V.A., Karelin R.D., Komarov V.S., Cherkasov V.V., Dormidontov N.A., Laisheva N.V., Yusupov V.S. Influence of rotary forging and post-deformation annealing on mechanical and functional properties of titanium nickelide. Metallurgist, 2024, vol. 67, pp. 1912–1919. DOI: 10.1007/s11015-024-01688-4. 4. Shuitcev A.V., Ren Y., Gunderov D.V., Vasin R.N., Li L., Valiev R.Z., Zheng Y.F., Tong Y.X. Grain growth in Ni50Ti30Hf20 high-temperature shape memory alloy processed by high-pressure torsion. Materials Science and Engineering: A, 2024, vol. 918, p. 147478. DOI: 10.1016/j.msea.2024.147478. 5. Andreev V.A., Yusupov V.S., Perkas M.M., Yakushevich N.V. Goryachaya rotatsionnaya kovka prutkov diametrom 2–20 mm iz splavov s pamyat’yu formy na osnove nikelida titana [Hot rotary forging of bars with a diameter of 2–20 mm from shape memory alloys based on titanium nickelide]. Perspektivnye materialy i tekhnologii. V 2 t. T. 1 [Promising materials and technologies. In 2 vol. Vol. 1]. Vitebsk, Vitebsk State Technological University Publ., 2017, pp. 61–69. 6. Andreev V.A., Karelin R.D., Komarov V.S. Cherkasov V.V., Dormidontov N.A., Laisheva N.V., Yusupov V.S. Vliyanie rezhimov rotatsionnoi kovki i posledeformatsionnoi termicheskoi obrabotki na mekhanicheskie i funktsional’nye svoistva nikelida titana [Influence of rotary forging and post-deformation heat treatment on mechanical and functional properties of titanium nickelide]. Metallurg = Metallurgist, 2023, no. 12, pp. 87–92. DOI: 10.52351/00260827_2023_12_87. (In Russian). 7. LotkovA.I., GrishkovV.N., BaturinA.A., Dudarev E.F., ZhapovaD.Yu., TimkinV.N. Vliyanie teploi deformatsii metodom abc-pressovaniya na mekhanicheskie svoistva nikelida titana [The effect of warm deformation by abcpressing method on mechanical properties of titanium nickelide]. Pis’ma o materialakh = Letters on Materials, 2015, vol. 5 (2), pp. 170–174. DOI: 10.22226/2410-3535-2015-2-170–174. (In Russian). 8. Fedotkin A.A., Stolyarov V.V. Osobennosti deformatsionnogo povedeniya nanostrukturnykh titanovykh splavov pri rastyazhenii pod deistviem impul’snogo toka [Features of the deformation behavior of nanostructured titanium alloys under tension under the action of pulsed current]. Mashinostroenie i inzhenernoe obrazovanie = Mechanical Engineering and Engineering Education, 2012, no. 1 (30), pp. 28–35. 9. Misochenko A.A., Fedotkin A.A., Stolyarov V.V. Influence of grain size and electric current regimes on deformation behavior under tension of shape memory alloy TI49,3NI50,7. Materials Today: Proceedings, 2017, vol. 4 (3), pp. 4753–4757. DOI: 10.1016/j.matpr.2017.04.065. 10. Stolyarov V.V. Elektroplasticheskii effekt v krupnozernistom i ul’tramelkozernistom titane [The electroplastic effect in coarse-grained and ultrafine-grained titanium]. Zavodskaya laboratoriya. Diagnostika materialov = Industrial laboratory. Diagnostics of materials, 2023, vol. 89 (8), pp. 62–66. DOI: 10.26896/1028-6861-2023-89-862-66. (In Russian).
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