Lamellar Pearlite as an Initial Microstructure for Austenite Reversion Treatment

Through carbon and manganese partitioning to austenite from polygonal ferrite, bainite and martensite, retained austenite (RA) could be stabilized at room temperature in advanced high-strength steels. Alternatively, the present study utilized lamellar pearlite as an initial microstructure for austenite reversion treatment at 750 °C and successfully produced the microstructure consisting of film RA and lath martensite. This heat treatment is named as pearlitic reversed austenitization. The austenite formed from cementite was enriched in manganese and, in turn, was retained at room temperature; whereas, the austenite formed from ferrite was depleted in manganese and, in turn, transformed to martensite during cooling to room temperature. Different holding times at 750 °C led to different microstructures and RA fractions. After tempering 1 min at 300 °C, a high ultimate tensile strength of 1791 MPa and a decent total elongation of 8.1% were achieved due to tempered martensite matrix and transformation-induced plasticity effect. These tensile properties are comparable to C250 maraging steel. This investigation opens a new avenue to produce high-strength and good ductility steels based on pearlite.