Direct observation of chemical short-range order in 25 wt% Mn steel via transmission electron microscopy

Abstract

In this study, we demonstrate the existence of chemical short-range order (CSRO) in high-Mn (25Mn-0.6C-Fe in wt%) austenitic steel. A definitive proof of CSRO was obtained by electron diffraction measurements and dark field imaging via transmission electron microscopy. CSRO in the steel sample generated additional diffuse scattering in selected area electron diffraction patterns along high-index zone axes, namely, [1 1 1](gamma), [1 1 2](gamma), and [1 3 0](gamma), which was absent along low-index zone axes, namely, [1 1 0](gamma) and [0 0 1](gamma). We found that CSRO induced lattice distortions, and the corresponding interplanar spacing was twice that in gamma-austenite. This study offers a useful approach to detect CSRO in other high-Mn steels.