University of Oulu

Sumit Ghosh, Bernd M. Schönbauer, Sakari Pallaspuro, Mahesh Somani, Herwig Mayer, Jukka Kömi, Micro-mechanism associated with very high cycle fatigue crack initiation of advanced DQ&P processed steel, Procedia Structural Integrity, Volume 42, 2022, Pages 919-926, ISSN 2452-3216,

Micro-mechanism associated with very high cycle fatigue crack initiation of advanced DQ&P processed steel

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Author: Ghosh, Sumit1; Schönbauer, Bernd M.1,2; Pallaspuro, Sakari1;
Organizations: 1Materials and Mechanical Engineering, Centre for Advanced Steels Research, University of Oulu, Oulu 90014, Finland
2Department of Material Sciences and Process Engineering, Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Vienna (BOKU, Vienna 1190, Austria
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.9 MB)
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Language: English
Published: Elsevier, 2022
Publish Date: 2023-01-16


In the present study, very high cycle fatigue (VHCF) characteristics and properties of a direct quenched and partitioned (DQ&P) medium carbon (0.4 wt.% C) steel having ultrahigh-strength (UTS > 2 GPa) was investigated using an ultrasonic-fatigue testing technique (∼19 kHz frequency) up to ∼10¹⁰ cycles at the load ratio (R) of −1 (fully reversed tension-compression). The occurrence of crack initiation in the VHCF regime was observed at interior non-metallic inclusions. The microstructural changes following VHCF failure underneath the fracture surfaces near the crack initiation sites were further investigated through transmission electron microscopy. Formation of a clear nanograined subsurface layer adjacent to the crack initiating site at the interior inclusion was noticeably evident. The variation of average grain size (60 − 140 nm) and thickness (300 − 1200 nm) of nanograined layers at different number of cycles to failure were measured in detail. Apparently, localized plastic deformation caused the fragmentation of martensitic laths and hence, the formation of aforesaid ultrafine-grained layers in the microstructures.

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Series: Procedia structural integrity
ISSN: 2452-3216
ISSN-E: 2452-3216
ISSN-L: 2452-3216
Volume: 42
Pages: 919 - 926
DOI: 10.1016/j.prostr.2022.12.116
Host publication: 23 European Conference on Fracture - ECF23
Host publication editor: Moreira, Pedro
dos Reis, Luis Filipe Galrao
Conference: European Conference on Fracture
Type of Publication: A4 Article in conference proceedings
Field of Science: 212 Civil and construction engineering
214 Mechanical engineering
216 Materials engineering
Funding: The authors are grateful for the financial support provided by the Jane and Aatos Erkko Foundation of Finland and Academy of Finland (grant No. #311934).
Copyright information: © The Author(s) 2022. Published by Elsevier B.V. This is an open access article under the CC-BY-NC-ND 4.0 license (