OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 2 2025 that with increasing degree of CRF, pronounced textural gradients develop. These texture gradients are due to the fact that a sharp two-component axial texture <111>//RA and <100>//RA, is formed in the center of the rods, which weakens towards the edge. It should be noted that the shear texture B/B ̅develops at the edge of the rod after 40 % CRF and higher [19, 20]. The distribution of microhardness in the cross section of the rods shows the development of a gradient structure during CRF (Fig. 5). In the case of the initial state with a homogeneous structure, a uniform distribution of microhardness is observed across the cross-section of the rods of both steels. 20 % CRF is accompanied by a general increase in the hardness of the program steel. However, the hardness of the rod edge increases to a greater extent. Texture analysis showed a relatively uniform distribution of grains with <111>//RA and <100>//RA orientations across the section after 20 % CRF, i.e. this factor does not have a significant effect. Meanwhile, the increased density of microbands and mechanical twins is observed at the edge (Fig. 3), which is due to high strain accumulation in this place and determines an increased level of hardness. These structural changes also affect the results of uniaxial tensile tests of samples cut from the center and edge of rods of both steels. At the same time, the strength of the edge material of the rods was significantly higher than that of the material from the center (Table). Plasticity at the edge was lower mainly due to a decrease in uniform elongation due to the accumulation of a higher density of crystalline structure defects (Fig. 3). Further 40-85 % CRF is accompanied by an increase in the microhardness of the rods. After 40 % CRF, the previously obtained microhardness gradient is smoothed out (Fig. 5). Subsequent 60-85 % CRF leads to the formation of the microhardness peak in the center of the studied rod. The results of the quantitative analysis of the microstructure of the studied steels showed that after 40-60 % CRF, an increased density of lattice defects is still observed at the edge of the rod compared to the core (Fig. 3). Additionally, a pronounced gradient of the volume fraction of austenite grains with the <111>//RA orientation is formed across the rod cross-section (Fig. 4). Thus, in the center of the rod, a high proportion (up to 70 %) of grains with the <111>//RA orientation is observed. Due to the active development of shear bands at the edge of the rod, the shear texture B/B ̅is formed. In this case, the determining factor in the occurrence of a microhardness gradient is the texture gradient, since such grains with the orientation <111>//RA perform a low value of the Schmid factor for mechanical twinning and dislocation slip (Fig. 8). The highest level of the Schmid factor is observed in grains with the orientation <100>//RA, however, the proportion of such crystals in the center of the rod does not exceed 18 %. The observed changes in the microstructure and texture during CRF of the studied steels to 40-85 % deformation are accompanied by a change in the ratio between the strength and ductility of the center and edge of the rod (Fig. 6). In this case, the highest strength and the lowest ductility are found in the material from the center of the rod. Following CRF to a b с Fig. 8. Orientation map of austenitic grains with orientations <111>//BA and <100>//BA (a), grain distribution based on Schmid factor for dislocation slip (b) and mechanical twinning (c) of Fe-21Mn-6Al-1C steel after CRF with ε = 60% in the center of the rod
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