University of Oulu

Ali, M., Porter, D., Kömi, J., Eissa, M., El Faramawy, H. and Mattar, T. (2020), Characterization of the Microstructure and Precipitates Formed During the Thermomechanical Processing of a CrNiMoWMnV Ultrahigh‐Strength Steel. steel research int., 91: 1900580. doi:10.1002/srin.201900580

Characterization of the microstructure and precipitates formed during the thermomechanical processing of a CrNiMoWMnV ultrahigh‐strength steel

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Author: Ali, Mohammed1,2; Porter, David1; Kömi, Jukka1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, P.O. Box 4200, 90014 Oulu, Finland
2Steel Technology Department, Central Metallurgical Research and Development Institute (CMRDI), Helwan, 11421 Cairo, Egypt
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2020041416457
Language: English
Published: John Wiley & Sons, 2020
Publish Date: 2021-01-11
Description:

Abstract

The effect of total applied strain (TAS), finish forging temperature (FFT) on the microstructure, and precipitation kinetics of a newly developed low‐cost, low‐alloy CrNiMoWMnV ultrahigh‐strength steel has been investigated. A Gleeble 3800 thermomechanical simulator is used to simulate the hot forging process and its influence on the precipitation kinetics. Field‐emission scanning electron microscopy combined with electron‐backscattered diffraction is used to characterize the final overall microstructures, whereas transmission electron microscopy on carbon extraction replicas is used to characterize the precipitates in terms of morphology, size distribution, mean equivalent circle diameter, the 90th percentile in the cumulative diameter distribution (D90%ppt), chemical composition, and crystallography. Thermo‐Calc software is used to predict the precipitates expected in austenite at equilibrium. The final microstructure consists of lath martensite and a small fraction of the precipitates AlN, TiN, and composite TiN–AlN. Differences in the degree of strain‐induced precipitation caused by variations in TAS and FFT have been shown to greatly influence precipitate size distributions. Variations in the degree of precipitate dissolution and coarsening cause variations in the prior austenite grain size, which subsequently cause variations in the effective grain size of the final microstructure, i.e., that are defined by high‐angle grain boundaries.

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Series: Steel research international
ISSN: 1611-3683
ISSN-E: 1869-344X
ISSN-L: 1611-3683
Volume: 91
Issue: 6
Article number: 1900580
DOI: 10.1002/srin.201900580
OADOI: https://oadoi.org/10.1002/srin.201900580
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Funding: The authors acknowledge the Egyptian Ministry of Higher Education (Cultural Affairs and Missions Sector) for financial support during this work.
Copyright information: © 2020 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim. This is the peer reviewed version of the following article: Ali, M., Porter, D., Kömi, J., Eissa, M., El Faramawy, H. and Mattar, T. (2020), Characterization of the Microstructure and Precipitates Formed During the Thermomechanical Processing of a CrNiMoWMnV Ultrahigh‐Strength Steel. steel research int.. doi:10.1002/srin.201900580, which has been published in final form at https://doi.org/10.1002/srin.201900580. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving."