Print Email Facebook Twitter Improving the strength-ductility balance of medium-Mn Q&P steel by controlling cold-worked ferrite microstructure Title Improving the strength-ductility balance of medium-Mn Q&P steel by controlling cold-worked ferrite microstructure Author Li, Jiayu (Northeastern University China; Universiteit Gent) Xu, Yunbo (Northeastern University China) Jing, Yi (Northeastern University China) Gao, Yijing (Northeastern University China) Liu, Hongliang (Technology Research Institute of Bengang Steel Plates Co.) Yu, Yongmei (Shenyang University of Chemical Technology) Banis, Alexandros (Universiteit Gent) Kestens, L.A.I. (TU Delft Team Maria Santofimia Navarro; Universiteit Gent) Petrov, R.H. (TU Delft Team Maria Santofimia Navarro; Universiteit Gent) Date 2023 Abstract The phase transformations, microstructure and properties of two Medium-Mn processed via quenching and partitioning steels were compared in this contribution and a new strategy for controlling mechanical properties by introducing and controlling cold-worked ferrite prior to heat treatment is proposed. It was found that during heating, the recovery and recrystallization of cold-worked ferrite compete with austenitization, thereby inhibiting the coarsening of austenite. The cold-worked ferrite interface will significantly delay the austenitization kinetics during the partitioning local equilibrium stage compared to martensite. These results lead to a diverse parent austenite, as well as a refined martensite substructure. As a result, the randomly distributed variants increase the number of effective grain boundaries, thus enhancing yield strength. The intercritical annealing process at a temperature of 860 °C resulted in the formation of fresh martensite-retained austenite (M/RA) constituents exhibiting a remarkably fine (<2 μm) and uniform grain morphology. Such microstructure yielded substantial improvement in both the strength and ductility of the steel. The proposed treatment led to excellent elongation (24%) at fracture, combined with very high ultimate tensile strength and yield strength of 1345 MPa and 1163 MPa, respectively, of the steel, resulting in a product of strength and elongation that exceed 32 GPa%. Subject Austenitization kineticsCold-worked ferriteMedium‑manganese steelMicrostructure and mechanical propertiesQuenching and partitioning process To reference this document use: http://resolver.tudelft.nl/uuid:4e8310b5-bee3-46f0-b77d-b40a2adb93cb DOI https://doi.org/10.1016/j.matchar.2023.113377 Embargo date 2024-04-09 ISSN 1044-5803 Source Materials Characterization, 205 Bibliographical note Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public. Part of collection Institutional Repository Document type journal article Rights © 2023 Jiayu Li, Yunbo Xu, Yi Jing, Yijing Gao, Hongliang Liu, Yongmei Yu, Alexandros Banis, L.A.I. Kestens, R.H. Petrov Files PDF 1_s2.0_S1044580323007362_main.pdf 14.78 MB Close viewer /islandora/object/uuid:4e8310b5-bee3-46f0-b77d-b40a2adb93cb/datastream/OBJ/view