OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 strategies for increasing strength characteristics often lead to a significant decrease in impact strength and ductility [4–6]. For example, processing an AISI 304 austenitic stainless steel by cold rolling can increase the yield strength by more than twofold (from 640 MPa to 1,450 MPa). At the same time, a critical decrease in elongation to failure to 1 % is observed [7]. In this case, the change in mechanical properties is caused not only by strain hardening but also by the formation of deformation-induced martensite (α’). According to Ref. [6], deformation-induced martensite (α’/ε) can act as a site for crack nucleation because it is a brittle product of phase transformation, which also causes a decrease in impact toughness and ductility, simultaneously with an increase in strength characteristics [8]. In this case, the crack can propagate both within the martensite itself and along the interface between the deformation-induced martensite and the austenitic matrix [9]. In recent years, it has been shown that increasing strength properties without loss of ductility in austenitic steels is possible through the formation of heterogeneous structures [9–15]. A heterogeneous condition is understood as a structure that consists of structural elements of different sizes or chemical composition, which significantly impacts the mechanical properties of the material [16]. Such structures include heterogeneous lamellar structures [17], gradient structures [18], bimodal structures, etc. Thus, it is shown [17] that titanium samples with a heterogeneous lamellar structure formed during asymmetric rolling and subsequent recrystallization annealing exhibit strength at the level of samples with an ultrafinegrained (UFG) structure and ductility comparable to a material with a coarse-grained structure. AISI 304 steel samples with a gradient structure consisting of a central layer with microtwins and nanotwins in the subsurface layers have a yield strength of 820 MPa and a uniform elongation of 53 % [18]. In contrast, samples of such steel with a homogeneous structure demonstrate a yield strength of 268 MPa and a uniform elongation of 63 %. The literature reports on the production of heterogeneous structures in rod blanks using cold radial forging (CRF) [10, 19–22]. It has been shown that the CRF of rods made of AISI 316Ti steel to a 95 % area reduction leads to the formation of a heterogeneous structure in the cross-section. Notably, increasing the area reduction from 40 % to 80 % positively affects the material’s strength characteristics. Specifically, a 15 % increase in yield strength is observed, while ductility remains at the same level. Furthermore, lowtemperature heat treatment at 400–600°C of the CRF rod causes a significant increase in the yield strength (from 1,077 to 1,310 MPa) [22]. Along with this, an increase in the elongation to failure from 9 % to 11 % is observed. It is important to note that structural heterogeneity is preserved after low-temperature heat treatment. Despite the existing research on the formation of heterogeneous structures during CRF, the underlying mechanisms responsible for improving mechanical properties through heterostructuring treatment remain unclear. The purpose of this work is to study the effect of heterogeneity obtained during CRF and subsequent heat treatment on the mechanical properties of 0.08 C-17 Cr-13 Ni-2 Mn-Ti austenitic stainless steel. To achieve this purpose, the following tasks were set during the study: – to study the effect of thermomechanical processing on the formation of heterogeneous structure and texture in the rod; – to study the effect of the heterogeneous structure obtained during thermomechanical processing on the mechanical properties of the material under study. Methods 0.08 C-17 Cr-13 Ni-2 Mn-Ti austenitic stainless steel was selected as the subject of research in the present study. The chemical composition of the studied steel included the following elements (wt. %): 0.08% C, 16.4% Cr, 12.3% Ni, 2.18% Mo, 1.28% Mn, 0.42% Si, 0.2% Ti, with Fe as the balance. The original rod was obtained by CRF to a 95 % area reduction using a forging machine with radially moving dies. CRF was carried out using the following parameters: a strike frequency of 1,000 strikes per minute, a feed speed of 180 millimeters per minute, and a rotation speed of 25 rotations per minute. To prevent overheating of the workpiece during CRF, the rod was cooled by an external water supply. The state
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