Felisters Zvavamwe, Jubert Pasco, Min‐Kyu Paek, Clodualdo Aranas
In this work, the impact of microalloying with molybdenum, ranging from 0.05 to 0.25 wt%, on the microstructural properties of as-cast medium manganese steel was explored. Four medium manganese steels with different molybdenum contents were designed using a CALPHAD approach. A duplex phase microstructure consisting of martensite and retained austenite was observed in all the steels investigated. Increasing Mo content delays the martensitic transformation and promotes the formation of equiaxed prior austenite grains, effectively suppressing γ-lean band formation observed in low-Mo alloys. The prior austenite grain refinement also offers additional nucleation pathways for solid-state martensitic transformation and reduces the preferential <100> casting texture. Mo addition therefore mitigates the effects of directional solidification and leads to a more uniform distribution of retained austenite throughout the microstructure. The element distribution in the constituent phases was investigated in detail. Mn, Mo and Si segregation to austenite was observed. The origins of elemental banding in medium manganese steels were also analyzed. The findings also revealed that increasing the molybdenum content led to an increase in the hardness of the steel.