Microstructure and Mechanical Properties of 18%Mn TWIP/TRIP Steels Processed by Warm or Hot Rolling

Abstract

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.