Partitioning temperature-dependent microstructures and mechanical properties of precipitation-hardened medium-Mn steel

This study reports the partitioning temperature-dependent microstructures and mechanical properties of precipitation-hardened medium Mn steel processed by roomtemperature quenching and partitioning. The hot-rolled Fe-7Mn-0.3C-3Ni-1.5Si-1Al -1Cu-0.3V (wt.%) steel was processed by austenitization, water quenching to roomtemperature, and partitioning treatment at 200, 300, 400, and 500 degrees C for 600 s. The samples before and after the partitioning process at temperatures below 400 degrees C show a microstructure consisting of lath martensite and retained austenite, whereas the sample partitioned at 500 degrees C shows a notably high fraction of retained austenite, owing to the formation of austenite grains during the partitioning process. The C partitioning during the partitioning process led to higher C contents in the samples processed by austenitization, quenching, and partitioning than in the sample processed by austenitization and quenching. The co-precipitation of VC precipitates and dispersed fine particles could exhibit a precipitation-strengthening effect. The sample partitioned at 200 degrees C shows an excellent strength-ductility combination, i.e., a yield strength of 740.9 MPa, an ultimate tensile strength of 1623.6 MPa, and a total elongation of 23.8%. Film-like retained austenite stabilized by carbon partitioning could exhibit high mechanical stability, leading to a gradual transformation induced plasticity (TRIP) effect and superior mechanical properties. In contrast, the samples partitioned at temperatures above 400 degrees C show poor ductility with brittle fracture, which could be related to the formation of martensite/retained austenite (M/A) constituents. (c) 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

This study investigates the microstructures and mechanical properties of precipitation-hardened medium Mn steel processed via room temperature quenching and partitioning. The results show that samples subjected to partitioning below 400 degrees C have a microstructure consisting of lath martensite and retained austenite, while the sample partitioned at 500 degrees C exhibits a high fraction of retained austenite. Carbon partitioning during the process leads to higher carbon contents. The sample partitioned at 200 degrees C demonstrates an excellent combination of strength and ductility, while samples partitioned above 400 degrees C show poor ductility with brittle fracture.