Properties of thermomechanically processed dual-phase steels containing fibrous martensite

Manganese partitioning and long fibrous martensite were obtained in several dual-phase steels by annealing, followed by hot rolling in their respective intercritical annealing temperature regions. The volume fraction of martensite was varied by changing the intercritical annealing temperature. Long annealing times were required to obtain complete manganese partitioning in order to increase the strength of the austenite phase and subsequently the martensite phase. Post-roll annealing improves the ductility through ferrite recrystallisation and also by changes to the martensite morphology, however, this results in a decrease in strength. The as-rolled steel shows two distinct work-hardening processes with different exponents and shows a laminated fracture appearance due to the ribbon-like morphology of the martensite.