The microstructure and mechanical properties of Fe-18Mn-0.6C and Fe-18Mn-0.4C steels subjected to rolling with a total reduction of 60% at temperatures of 773 K to 1373 K were investigated. Warm rolling at temperatures of 773-1073 K resulted in flattened grain structure with the transverse grain size of 7 µm, whereas hot rolling at 1073-1373 K was accompanied by the dynamic recrystallization leading to almost equiaxed grains, the size of which increased with temperature. Internal stresses and corresponding dislocation densities increased as the rolling temperature decreased. The steel with higher carbon content exhibited finer grains and higher dislocation density after rolling. A decrease in the rolling temperature from 1373 K to 773 K resulted in a significant increase in the yield strength from about 300-400 MPa to 850-950 MPa, while ultimate tensile strength increased from 1000-1100 MPa to 1200-1300 MPa (the higher strength corresponds to higher carbon content). On the other hand, the total elongation decreased from approx. 85% in the Fe-18Mn-0.6C steel and from 65% in the Fe-18Mn-0.4C steel to approx. 30% in the both steels as the rolling temperature decreased from 1373 K to 773 K. The difference in the tensile behavior at room temperature was attributed to the variation in the deformation mechanisms. Namely, mechanical twinning operated in the both steels during tension, whereas ε-martensite formation took place in the Fe-18Mn-0.4C steel.

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The deformation microstructures and mechanical properties were studied in a medium-Mn austenitic steel subjected to warm-to-hot rolling. During warm rolling at temperatures of T < 1073 K the structural changes were controlled by dynamic and static recovery leading to a pancaked work-hardened microstructure, during hot rolling at T ‡ 1073 K-by discontinuous dynamic and post-dynamic recrystallization resulting in equiaxed grains. The grain size decreased while the dislocation density increased with a decrease in rolling temperature. A decrease in rolling temperature enhanced the texture development, which consisted of relatively strong Brass, S and P components. The Brass component exhibited the strongest temperature dependence. A decrease in rolling temperature resulted in significant strengthening of the steel. The yield strength increased from 340 to 950 MPa as rolling temperature decreased from 1373 K to 773 K. Both the grain refinement and the work-hardening contributed to the strengthening.

Two Fe–18%Mn steels with carbon content of 0.4 or 0.6% C are hot rolled at 1150 °C with 60% reduction followed by thermo‐mechanical processing under conditions of warm or hot rolling at 500 or 1100 °C, respectively, with a reduction of 60%. The uniform microstructures consisting of equiaxed grains with an average size of 34 and 26 μm are produced by hot rolling in the Fe–18Mn–0.4 C and Fe–18Mn–0.6 C steels, respectively. In contrast, the warm rolling results in the deformation microstructures composed of pancaked grains elongated in the rolling direction with mean transverse grain sizes of 14 and 10 μm in the Fe–18Mn–0.4 C and Fe–18Mn–0.6 C steels, respectively. Both the hot and warm rolling improve the mechanical properties of the present steels. A decrease in the rolling temperature results in significant increase in the yield strength, which comprises 300–360 MPa after rolling at 1100 °C and 850–950 MPa after rolling at 500 °C, although the ultimate tensile strength does not increase substantially (1000 and 1300 MPa after hot and warm rolling, respectively). The steel with higher carbon content is characterized by somewhat higher strength after warm/hot rolling.

The deformation behavior of 18%Mn twinning‐induced plasticity (TWIP) steels with 0.4%C or 0.6%C is studied by means of isothermal compression tests in the temperature range of 973–1373 K at the strain rates of 10−3–10−1 s−1. The hot working is accompanied by the development of discontinuous dynamic recrystallization (DRX), which is commonly advanced by an increase in deformation temperature and/or a decrease in strain rate. A decrease in the carbon content promotes the DRX development, though the flow stresses scarcely depend on the carbon content. The change in the DRX kinetics results in the specific distributions of the grain orientation spread (GOS) among the DRX grains, depending on deformation conditions. The maximal fraction of grains with small GOS below 1° corresponding to rapid DRX development is observed at certain temperature/strain rate, although the DRX fraction increases with a decrease in temperature‐compensated strain rate and can be related to the fraction of grains with GOS below 4°. The texture of DRX grains is also determined by the orientations of grains with GOS below 4°. The grain boundary mobility for the DRX grain growth is characterized by an activation energy close to that for grain boundary diffusion.