OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 of deformation microbands (microband-induced plasticity ‑ MBIP) [5, 6], on the one hand. On the other hand, during heating of such materials, an aging phenomenon is observed ‑ precipitation of nanoparticles of κ’- carbides, B2- and/or DO3- phases [7–10], which is accompanied by significant strengthening and a decrease in ductility. The structure formation of LWASs during cold plastic deformation has currently been studied mainly in cold rolling and uniaxial tension [5, 11–13]. The high stacking fault energy (SFE) of such materials (60‑120 mJ/m2) at room temperature determines dislocation slip as the main mechanism of plastic deformation [1]. In this case, the phenomenon of short-range ordering due to alloying with aluminum causes deformation due to the formation of microbands in the {111} planes. It has been established that at early stages of deformation (ε up to 10 %) in Fe-28Mn-10Al-1C steel a Taylor lattice is formed from dislocation microbands of two different systems [5]. With an increase in the degree of deformation, an accumulation of misorientation occurs between the domains of the Taylor lattice, which after ε = 60 % leads to the fragmentation of initial austenitic grains. Meanwhile, there are other methods of severe plastic deformation without cracking, for example, radial forging [14, 15]. Recently, it has been shown that cold radial forging with high degrees of deformation (to 90 %) resulted in the development of heterogeneous structures in austenitic alloys [16–18]. This phenomenon is caused by the non-uniform distribution of the operating stresses and temperatures across the rod cross-section during deformation processing. Thus, high compressive stresses act in the rod edge, and moderate tensile stresses are predicted in the rod core. In addition, due to external water cooling and deformation-induced internal heating of the rod core, a gradient in the temperature distribution across the cross-section is observed. However, the effect of radial forging on the microstructure and mechanical properties of LWASs requires separate consideration. The purpose of this work is to study the evolution of the microstructure, texture, and mechanical properties of the lightweight austenitic steel Fe-21Mn-6Al-1C subjected to cold radial forging. To achieve this purpose, the following objectives were addressed: - to determine the effect of the degree of deformation on the microstructure in the cross-section of the rod; – to determine the effect of the degree of deformation on the texture in the cross-section of the rod; – to study the distribution of microhardness in the cross-section of the rod after cold radial forging (CRF); – to determine the effect of the degree of deformation on the mechanical properties of the material after cold radial forging (CRF). Methods The object of the study was the lightweight austenitic steel Fe-21Mn-6Al-1C in the form of rods with an experimental composition including the following components (wt. %): 19.76 % Mn; 6.08 % Al; 0.25 % Ni; 1.01 % C; 0.004 % P; 0.004 % S; Fe – balance. The initial ingot was obtained from pure materials by vacuum arc melting. Then, the ingot was subjected to hot working in the temperature range of 900–1,100 °C in order to obtain a rod for subsequent cold radial forging. The rod with a diameter of 39 mm was annealed (austenitized) at 1,050 °C for 2 hours with cooling in water. The rod was subsequently cold radially forged using a radial forging machine with a feed rate of 180 mm/min, a striker frequency of 1,000 strokes per minute (spm), and a rotation speed of 25 rpm. During the deformation process, the rod was water cooled. Four stages of forging were carried out: from ~39 mm to ~34 mm, from ~34 mm to ~29 mm, from ~29 mm to ~24 mm, from ~24 mm to ~18 mm, which amounted to ~20 %, ~40 %, ~60 % and ~80 % of the relative deformation, respectively. The microstructure was examined in the cross section of the rod on thin foils using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Specimens 0.3 mm thick were cut using an electrical discharge machine, thinned to 0.1 mm by grinding on abrasive paper and polished in an electrolyte (electrolyte composition: 5 % perchloric acid, 35 % butanol and 60 % methanol) at room
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