Flash annealing of a chemically heterogeneous medium Mn steel

Medium Manganese Steels (MMS) are considered among the most promising 3rd generation advanced high strength steels. However, their practical production and application have been constrained by factors such as relatively high Mn content, low yield strength and the occurrence of Luders banding. In this contribution, flash heating and the concept of chemical heterogeneity were combined to engineer an MMS variant with a reduced Mn content (Fe-0.18C-4.95Mn-0.4Si (wt.%)), nearly doubling the material's yield strength and successfully mitigating the presence of Luders banding. It is interestingly found that Mn heterogeneity can not only directly stabilize austenite but also contributes to austenite stabilization via promoting carbon partitioning from the Mnpoor austenite into the Mn-enriched austenite. Heating rate is proven to be a key parameter to manipulate chemical heterogeneity, austenite stability and mechanical properties. The present strategy can be potentially applied to other advanced high strength steels.