Effect of thermomechanical treatment on the microstructures and mechanical properties of an ultrafine grained steel using bainite starting microstructure

Abstract

AbstractThe cold rolling and subsequent annealing of microstructures with a high percentage of bainite is one of the promising thermomechanical treatments for grain refinement in low-alloy steels. In this research, the bainite microstructure was formed in the steel DIN 1.5715 by austenitizing at 1143 K followed by quenching in a salt-bath at 688 K. The specimens were then cold rolled to 90 % reduction in thickness followed by annealing at 773–923 K for different times. An ultrafine grained ferrite microstructure was developed possessing the best strength–ductility balance after 90 % cold rolling followed by annealing at 923 K for 2 400 s.