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
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