University of Oulu

Ghosh, S., Mula, S., Malakar, A., Somani, M., & Kömi, J. (2021). High cycle fatigue performance, crack growth and failure mechanisms of an ultrafine-grained Nb+Ti stabilized, low-C microalloyed steel processed by multiphase controlled rolling and forging. Materials Science and Engineering: A, 825, 141883. https://doi.org/10.1016/j.msea.2021.141883

High cycle fatigue performance, crack growth and failure mechanisms of an ultrafine-grained Nb+Ti stabilized, low-C microalloyed steel processed by multiphase controlled rolling and forging

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Author: Ghosh, Sumit1,2; Mula, Suhrit1; Malakar, Aniruddha1;
Organizations: 1Department of Metallurgical and Materials Engineering, Indian Institute of Technology Roorkee, Roorkee, 247667, Uttarakhand, India
2Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, 90014, Oulun yliopisto, Finland
Format: article
Version: accepted version
Access: embargoed
Persistent link: http://urn.fi/urn:nbn:fi-fe2022021719703
Language: English
Published: Elsevier, 2021
Publish Date: 2023-08-08
Description:

Abstract

An effort has been made to examine the high cycle fatigue (HCF) properties including crack propagation characteristics and related fracture mechanisms of submicron-grained (SG) Nb + Ti stabilized low C steel processed through advanced multiphase-controlled rolling (MCR) and multiaxial forging (MAF). The HCF and other mechanical properties have been correlated with microstructural features characterized by light optical (LOM), transmission electron (TEM) and scanning electron microscopy (SEM), aided with electron backscatter diffraction (EBSD). TEM analysis near the fracture zones of the fatigue tested samples and corresponding fractographic analysis corroborated well in explaining the improved fatigue life of the SG steel. The fatigue strength was found to have a linear relationship with the tensile strength in both types of processed samples. The fatigue strength of the forged specimens was estimated to be nearly twice than that of the untreated annealed steel, demonstrating significantly different fracture characteristics. Intergranular fracture is found to be dominant in the rolled/forged specimens, in comparison to the transgranular fracture observed in the as-received steel. Such variances in fatigue strength and fracture characteristics have been endorsed to their microstructural constituents. Superior combinations of yield strength (YS), tensile strength (UTS), elongation (% El.) and high cycle fatigue strength (σf) (YS = 1027 MPa, %El. = 8.3%, σf = 355 MPa) were obtained in multiphase-controlled 15-cycle multiaxially forged (MAFed) specimens (processed in intercritical α+γ phase regime). An enhancement of the fatigue strength can be ascribed to the formation of evenly dispersed nano-sized fragmented cementite (Fe₃C) particles (~35 nm size) present in the SG ferritic matrix (average ~280 nm size). The fine dislocation substructures/cells together with the nano-sized Fe₃C particles could efficiently block the initiation and propagation of cracks thereby enhancing the fatigue endurance limit of the steel. Superior mechanical properties together with high fatigue resistance in the SG material render the present steels highly beneficial for high-strength structural applications.

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Series: Materials science & engineering. A, Structural materials: properties, microstructure and processing
ISSN: 0921-5093
ISSN-E: 1873-4936
ISSN-L: 0921-5093
Volume: 825
Article number: 141883
DOI: 10.1016/j.msea.2021.141883
OADOI: https://oadoi.org/10.1016/j.msea.2021.141883
Type of Publication: A1 Journal article – refereed
Field of Science: 216 Materials engineering
Subjects:
Copyright information: © 2021 Elsevier B.V. This manuscript version is made available under the CC-BY-NC-ND 4.0 license http://creativecommons.org/licenses/by-nc-nd/4.0/.
  https://creativecommons.org/licenses/by-nc-nd/4.0/