Effect of a new pretreatment-Q&P process on the microstructure and mechanical properties of light-weight Al-containing medium-Mn steels

Abstract

This study examines the impact of a new pretreatment-Q&P process on the mechanical properties and microstructure of lightweight Al-containing medium Mn steels. The tested steel is pre-strained (0%, 1%, 2%, and 3%) before going through the Q&P process. The tested steel's microstructure and mechanical properties were examined. And the results revealed that the tested steel was composed of martensite, α-ferrite, δ-ferrite, and retained austenite. After the heat treatment process, the retained austenite in the microstructure is distributed in a dispersed distribution. According to research, the amount of elemental Mn required to maintain a stable presence at room temperature varies depending on the retained austenite morphology. Simultaneously, it was revealed that the process significantly improved martensite/retained austenite/ferrite to accept dislocations. This is because the increase in dislocation channels allows C/Mn/Al/Si elements to diffuse more easily, allowing the block, granular retained austenite to remain moderately stable at room temperature. This facilitates the TRIP effect, which enhances the plasticity of the medium manganese steels. At the same time, when the external stress reaches a certain degree, the sudden opening of dislocations in the microstructure and their mutual cancellation causes stress relaxation and redistribution in the medium manganese steel microstructure. The plasticity of medium manganese steels is greatly enhanced by the combined effect of the TRIP effect and the redistribution of stress between the microstructures.