Influence of martensite morphology on the work-hardening behavior of high strength ferrite-martensite dual-phase steel

This study concerns influence of martensite morphology on the work-hardening behavior of high-strength ferrite-martensite dual-phase (DP) steel. A low-carbon microalloyed steel was subjected to intermediate quenching (IQ), step quenching (SQ), and intercritical annealing (IA) to develop different martensite morphologies, i.e., fine and fibrous, blocky and banded, and island types, respectively. Analyses of work-hardening behavior of the DP microstructures by differential Crussard-Jaoul technique have demonstrated three stages of work-hardening for IQ and IA samples, whereas the SQ sample revealed only two stages. Similar analyses by modified Crussard-Jaoul technique showed only two stages of work-hardening for all the samples. Among different treatments, IQ route has yielded the best combination of strength and ductility due to its superior work-hardening behavior. The influence of martensite morphology on nucleation and growth of microvoids/microcracks has been correlated with the observed tensile ductility.