Improvement of Mechanical Properties and Work-Hardening Behavior of Intercritically Annealed Dual Phase Steel

The effect of the initial microstructure and intercritical annealing on mechanical properties and work-hardening response of a high-formability low carbon steel were studied. The work-hardening analysis was based on the modified Crussard–Jaoul method. The ferritic-pearlitic sheets showed low strength and high total elongation with the appearance of the yield point phenomenon. The occurrence of yield-point phenomenon resulted in the very low work-hardening rates at the initial stages of deformation. However, after intercritical annealing, a good combination of tensile strength and ductility along with much better work hardening response was observed. Intercritical annealing of martensite initial microstructure was found to be a viable technique for graining refinement of DP steels with much better tensile strength compared with that obtained by intercritical annealing of the normalized microstructure. These observations were related to the much finer microstructure and enhancement of work-hardening behavior in the former, where its work-hardening rate at each given true stress was considerably higher.