Mechanical twinning and texture evolution during asymmetric warm rolling of a high manganese steel

Asymmetric rolling is known to strongly refine the microstructure of metallic alloys due to an additional shear strain component introduced to the material, as compared to symmetric rolling. Additionally, the rolling temperature significantly influences the stacking fault energy (SFE) and thus, may be used to control the activation/suppression of the deformation mechanisms, such as deformation twinning. In the present study, asymmetric rolling at temperatures ranging from room temperature to 400 degrees C was applied to a high-manganese Twinning-Induced Plasticity (TWIP) steel in order to tailor the yield strength- ductility combination. Microstructure and texture evolution were investigated by transmission electron microscopy (TEM), electron backscatter diffraction (EBSD) and x-ray diffraction (XRD) in order to gain a detailed insight into the active deformation mechanisms and their effect on the mechanical properties. The combination of applied asymmetry and rolling at elevated temperatures resulted in a high yield strength (1047 MPa) due to a high density of dislocations and stacking faults on the one hand and a reasonably high ductility (30%) on the other hand. The latter was achieved by partial suppression of deformation twinning during warm rolling and subsequent activation of twinning during room temperature tensile testing. The suppression of twinning at elevated temperatures was most effective at low rolling degrees and resulted in a weak transition texture with characteristics of both Cu-type and Brass-type texture. In turn, at higher rolling degrees, where twinning was only partially suppressed, a weak Brass-type texture was developed.