Negative to positive transition of strain rate sensitivity in Fe-22Mn-0.6C-x(Al) twinning-induced plasticity steels

In this study, it is found that the high-manganese austenitic FeMnC twinning-induced plasticity (TWIP) steel exhibits negative strain rate sensitivity (SRS), which is contrary to other face-centered cubic (fcc) metals or alloys. The negative SRS phenomenon of Fe-22Mn-0.6C (wt%) TWIP steel is considered to be suppressed or even convert to be positive through adding Al element. Meanwhile, the relation between tensile strength and uniform elongation of the FeMnC(Al) TWIP steels displays a transition from trade-off to synchronously improvement with decreasing the strain rate and Al content. It is suggested that the negative SRS phenomenon of FeMnC TWIP steel can be mainly attributed to the twinning mechanism assisted by dynamic strain aging (DSA). This mechanism can also explain well the negative to positive transition of SRS in FeMnC(Al) TWIP steel with the addition of Al element.