Grain refinement of nickel-free high nitrogen austenitic stainless steel by reversion of eutectoid structure

For the purpose of austenite grain refinement, a two-step phase transformation was applied to nickel-free austenitic stainless steel (Fe–25Cr–1 N mass% alloy): first, the austenitic steel was subjected to isothermal heat treatment at around 1200 K to make the austenite decompose, which results in the formation of (ferrite + Cr2N) lamellar structure. The specimen with eutectoid structure was then reversed to austenite by heating. In addition, the grain refinement mechanism was discussed in terms of the nucleation of the reversed austenite.