Ultra-high strength attributed to retardation of recrystallization during intercritical annealing in cold-rolled (V,Nb) microalloyed 5Mn steel

The effects of V and Nb addition on the microstructure and mechanical properties of a cold-rolled and inter-criticallly annealed 5Mn steel were investigated. Compared to a steel without V or Nb the recrystallization in microalloyed steel was retarded significantly from the beginning of annealing, which resulted in a 100-200 MPa increase in both yield and tensile strength while the degradation of ductility was not observed. Negligibly small change in elongation was attributed to a larger degree of carbon enrichment due to the smaller volume fraction of retained austenite and accelerated Mn transport through high density dislocations, which may well have operated to increase the austenite stability.