Effect of pearlite on microstructures and tensile properties in Mn-heterogeneous steels

Abstract

Mn heterogeneity in high-temperature austenite is an effective way to tailor retained austenite and achieve a good balance of strength and ductility. Instead of conventional quenching and tempering, fast and short austenitization from Mn-partitioned pearlite followed by quenching and tempering is carried out, leading to the formation of ghost pearlite. Here, we have studied the role of the lamellar width of cementite on microstructures and tensile properties in Mn-heterogeneous steels. With increasing pearlite transformation temperature from 540 °C to 570 °C, the lamellar width of cementite increases from 11.4±2.1 nm to 18.3±2.8 nm, effectively enlarging the size of the Mn-enriched regions in high-temperature austenite, thereby facilitating the formation of ghost pearlite after quenching to room temperature. The high volume fraction of ghost pearlite can ensure a high strength due to refined width of martensitic lath, while high RA fraction can ensure a good ductility, leading to a simultaneous increase in yield strength and uniform elongation with increasing pearlite transformation temperature.