New insights to understand the strain-state-dependent austenite stability in a medium Mn steel: An experimental and theoretical investigation

摘要

Changes in the mechanical stability of austenite with strain state is a significant aspect that needs to be addressed in the use of medium Mn steel in automobile body construction. New insights are provided in this paper to understand strain-state-dependent austenite stability in a 5 wt% Mn-containing steel based on the analysis of the Schmid factor by electron backscatter diffraction and the calculation of the work done by the applied stress. Four strain states, namely uniaxial tension, simple shear, plane strain, and equibiaxial stretch, were considered and digital image correlation was used to capture the strain field during the entire deformation process. Results show that the mechanical stability of austenite decreases when strain state changes from uniaxial tension to plane strain, and further decreases in the case of equibiaxial stretch due to the increasing work done by the applied stress and the increasing Schmid factor. The austenite acquires the highest mechanical stability when it is deformed at the simple shear state, which corresponds to the lowest work done by the applied stress. The obtained knowledge promotes the basic understanding for the comprehensive application of medium Mn steels in the automobile industry.