Effect of vanadium on the microstructure, mechanical properties and deformation mechanisms of strip casting high-strength steels

A novel 890 MPa-grade strip casting high-strength low-alloy steel with high ductility was developed in this work. The effects of V content on the microstructure, mechanical properties, and deformation mechanisms of the steels were investigated and discussed in detail. Microstructural characterization revealed that increasing V content refines bainitic microstructure and enhances dislocation density. Our results suggest that V can effectively reduce the activation energy, causing a higher nucleation rate of bainite, and thus finer microstructure. Mechanical tests indicate that increasing the V content from 0.05 wt.% to 0.2 wt.% significantly improves yield strength and tensile strength from 666 MPa and 728 MPa to 801 MPa and 889 MPa without a remarkable decrease in ductility. This is because, despite the significant increase in strength, the dislocation storage and multiplication capacities of the steel with 0.20 wt.% V are comparable to those of the steel with 0.05 wt.% V, resulting in comparable work-hardening capability for the two steels. These findings provide valuable insights into the design of high-performance strip casting steels. • Systematic investigation reveals that the steel with 0.2 wt.% V shows a superior combination of strength and ductility. • Our study suggests that V not only contributes to precipitation strengthening but also promotes bainite nucleation by reducing the activation energy, thereby resulting in a refinement of microstructure. • The substantial strength enhancement of the 0.2 wt.% V steel without a marked loss of ductility can be attributed to its comparable dislocation multiplication and storage capacities with that of the 0.05 wt.% V steel.