Austenite Grain Growth in High Manganese Steels

Grain growth in high-manganese steel (HMS) was studied at high temperatures (1273 K to 1473 K). Grain growth was found to be two orders of magnitude slower than that in a commercial low-Mn steel, as indexed by average experimentally determined mobilities. Electron backscatter diffraction maps of grain boundaries revealed the presence of numerous special boundaries in the global boundary network. Most of the special boundaries appeared in the form of Σ3-type coincident site lattice boundaries (annealing twins). Interaction of high-angle grain boundaries with annealing twins results in the formation of low-energy–low-mobility boundary segments, which were considered to be the reason for slow grain growth in HMS. A first-order model of grain growth kinetics in the presence of annealing twins was shown to be in reasonable accord with the experimental data.