Effect of Intercritical Deformation on Microstructure and Mechanical Properties of Quenching and Partitioning Low Carbon Multiphase High-Strength Steel

Abstract

Low carbon multiphase high strength steel is widely used in the automobile industry. In this work, the effect of intercritical deformation on the partitioning of alloying elements and the evolution of microstructure, as well as the effect of retained austenite stability on mechanical properties, were studied in a low carbon steel. The results demonstrate that the intercritical deformation enhances the C, Mn partition from ferrite to austenite during annealing at 770 ℃, and the volume fraction of the retained austenite increased from 8.8% to 12.3%. The DIQ&PB sample shows good balance between strength (1226.5 MPa) and ductility (24.4%), whose product of strength and elongation reached a larger value of 29926.6 MPa·% due to the intercritical deformation. This research provides theoretical guidance for the process design of automobile high-strength steels, considering the integration between rolling and heat cycles.

Keywords

• multiphase steel
• intercritical deformation
• quenching and partitioning
• retained austenite
• TRIP effect