Microstructure evolution and strengthening mechanisms of Fe-₂₃Mn-₀.₃.C-₁,₅Al TWIP steel during cold rolling

The effect of cold rolling on the microstructure evolution and mechanical properties of Fe-₂₃Mn-₀.₃.C-₁,₅Al twinning-induced plasticity (TWIP) steel was studied. The extensive mechanical twinning subdivides the initial grains into nanoscale twin lamellas. In addition, the formation of deformation micro bands at ε>40% induces the formation of nanostructured bands of localized shear. It is demonstrated that the mechanical twinning is notably important for dislocation storage within the matrix, as the twin boundaries act as equally effective obstacles to dislocation glide as conventional high-angle grain boundaries. However, the contribution of the grain size strengthening to the overall yield stress (YS) is much smaller than that of the deformation strengthening, which plays a major role in the superior work-hardening behavior of TWIP steel