Structural/textural changes and strengthening of an advanced high-Mn steel subjected to cold rolling

The microstructure and texture evolution during cold rolling with total thickness reductions of 20-80% (nominal strains of 0.22-1.61) and their effect on the tensile behavior of an Fe-17Mn-1.5Al-0.3C steel were studied. The cold rolling to total strains of 0.5 was accompanied by multiple deformation twinning, resulting in the formation of twin/matrix lamellae with the boundary spacing of 35 nm. Correspondingly, the textural changes were characterized by the rapid evolution of rather strong Brass and S texture components. An increase in the rolling strain led to further reduction in the boundary spacing down to about 20 nm and the development of shear banding, which promoted the formation of γ-fiber (〈111〉||ND) at large strains. Before cold rolling, the investigated steel exhibited a large total elongation above 90% because of the TWIP (twinning-induced plasticity) effect and a relatively low yield strength of 245 MPa. The cold rolling resulted in significant increase in the yield strength up to 1440 MPa after rolling to a total strain of 1.61, whereas the total elongation decreased to 5%. The strengthening of the present steel during cold rolling was attributed to increased dislocation density and reduced twin/grain boundary spacing.