Chemical patterning enhanced by increasing quenching temperature in a medium-Mn steel

Chemical heterogeneity in high-temperature austenite is an effective way to tune the austenite-to-martensite transformation during cooling. The effect of quenching temperature on microstructure evolution is investigated when the high-temperature austenite is heterogeneous. After fast austenitization from partitioned pearlite consisting of Mn-enriched cementite and Mn-depleted ferrite in Fe–0.29C–3.76Mn–1.50Si (wt.%) steel, quenching to room temperature and quenching to 130 °C followed by 400 °C partitioning are both applied. With increasing quenching temperature from 25 to 130 °C, the amount of heterogeneous microstructure (lamellar ghost pearlite) increases from 10.6% to 33.6% and the thickness of Mn-enriched retained austenite film is increased from 31.9 ± 5.9 to 51.5 ± 4.4 nm, indicating an enhancement of chemical patterning. It is probably ascribed to the reduction in driving force for austenite-to-martensite transformation, which requires a lower Mn content for austenite retention.