Effect of Mn content and strain rate on mechanical properties of high-C high-Mn austenitic steel

Abstract

This research deals with tensile properties and deformation behavior of Fe-xMn-1.2C (wt.%, x = 7, 11, 15 and 19) steels. The effect of Mn content and strain rate on mechanical properties is analyzed considering deformation microstructure observation. Results show that the strength and plasticity of the test steels increase either with the increase of Mn content or strain rate. The increased Mn content enhances the stacking fault energy (SFE) of the test steel, but also aggravates the dynamic strain aging (DSA) effect, which promotes the formation of deformation twins and work hardening characteristic instead. The increased strain rate is also noted conducive for the formation of deformation twins. Consequently, the deformation strain prolongs, and desired strength and plasticity are obtained. At high strain rate of 2 × 10−2 s−1, the strength and plasticity of the 120Mn15 and 120Mn19 steels are observed approximately the same, which can be explained by the combined influences of strain rate and Mn element on the deformation twins and the DSA effect. Moreover, a moderate but stable strain hardening rate during plastic deformation is proved to be a key parameter to achieve excellent strength and plasticity in high-C high-Mn steel. The presented research provides an economical method for the selection of high-C high-Mn steel, i.e., reducing the Mn content, under different service environments.