Effect of hot rolling process on the microstructure and mechanical properties of a high-strength strip casting microalloyed steel

A novel Nb-V-Mo microalloyed steel with 1 GPa yield strength and high ductility was developed by strip casting. The effects of hot rolling on the microstructure and mechanical properties of the Nb-V-Mo microalloyed steel were investigated using scanning electron microscopy, electron backscatter diffraction, transmission electron microscopy, atom probe tomography and tensile tests. Both the as-cast and hot-rolled specimens exhibit a microstructure characterized by lath-like bainite and (Nb, V, Mo)C clusters, while the bainite lath was refined after hot rolling. Tensile test results show obvious improvements in the yield strength, tensile strength, and elongation of the hot-rolled specimen (1008 MPa, 1075 MPa, 20.1 %, respectively), compared to that of the as- cast ones (879 MPa, 978 MPa, 19.0 %, respectively). Additionally, the hot-rolled specimen displays a similar dislocation multiplication and storage capacity to the as-cast specimen, resulting in a comparable work- hardening capability during plastic deformation.