University of Oulu

Saeed Sadeghpour, Mahesh C. Somani, Jukka Kömi, L. Pentti Karjalainen, A new combinatorial processing route to achieve an ultrafine-grained, multiphase microstructure in a medium Mn steel, Journal of Materials Research and Technology, Volume 15, 2021, Pages 3426-3446, ISSN 2238-7854,

A new combinatorial processing route to achieve an ultrafine-grained, multiphase microstructure in a medium Mn steel

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Author: Sadeghpour, Saeed1; Somani, Mahesh C.1; Kömi, Jukka1;
Organizations: 1Centre for Advanced Steels Research, University of Oulu, 90014 Oulu, Finland
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 9.6 MB)
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Language: English
Published: Elsevier, 2021
Publish Date: 2021-11-16


A new combination of factors enhancing the stabilization of austenite, including pre-existed austenite among quenched martensite, prior deformation, and partitioning at high temperatures is employed to create a multi-component refined microstructure in a medium Mn steel (Fe–4Mn–0.31C–2Ni–0.5Al–0.2Mo, wt.%). The microstructure evolution and phase fraction during the processing are systematically investigated using various characterization methods. The microstructure of the specimen after 0.4 strain deformation of 73% martensite–27% austenite at 250 °C and subsequent partition-annealing at 600 °C for 20 min was composed of several phases including tempered martensite, fresh martensite, pearlite, 10% of retained austenite (RA) and undissolved cementite. By increasing the annealing temperature, the pearlitic transformation was suppressed, whereas recrystallization of the deformed martensite and carbide dissolution occurred following annealing at 650 °C for 20 min resulting in an ultrafine-grained microstructure composed of equiaxed ferrite, 32% RA along with some fresh martensite during final cooling and few carbide precipitates. The results demonstrate that the combinatorial approach accelerated partitioning of alloying elements from martensite and carbides to largely pre-existing austenite is responsible for the improved austenite stabilization during intercritical annealing of the deformed dual-phase specimens. However, competitive processes are also enhanced so that the RA content is not increased by deformation.

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Series: Journal of materials research and technology
ISSN: 2238-7854
ISSN-E: 2214-0697
ISSN-L: 2238-7854
Volume: 15
Pages: 3426 - 3446
DOI: 10.1016/j.jmrt.2021.09.152
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Funding: The authors would like to express their gratitude to the Academy of Finland for funding this research under the auspices of the Genome of Steel (Profi3) through project #311934.
Copyright information: © 2021 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (