Dynamic Strain Aging and Serration Behavior of Three High-Manganese Austenitic Steels

The strain-rate dependence of the flow stress of three high-manganese austenitic steels with different compositions was studied in terms of dynamic strain aging and serration behavior at room temperature under quasi-static strain-rate ranges from 10−4 to 10−1 s−1. Tensile stress–strain curves showed that serrated flow occasionally appeared and the strain-rate dependence of flow stress was measured to be negative at all strains for Fe-22Mn-0.3C and Fe-30Mn-0.2C steels and at higher strain for Fe-30Mn-0.2C-1.5Al steel. Based on the tendency for a critical strain corresponding to the onset strain of serrated flow and electron back-scattered diffraction analysis, it was found that serrated flow was not induced by deformation twinning and γ→ε\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \gamma \to \varepsilon $$\end{document} martensitic transformation, but by dynamic strain aging associated with the interaction between partial dislocation and solute carbon. Also, the addition of Al content increased the critical strain, meaning that it effectively prohibits dynamic strain aging. In addition, dynamic strain aging promoted deformation twinning and/or γ→ε\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$ \gamma \to \varepsilon $$\end{document} martensitic transformation and resulted in negative strain-rate dependence of flow stress in the high-manganese austenitic steels.