Mechanism of subsurface microstructural fatigue crack initiation during high and very-high cycle fatigue of advanced bainitic steels

Guhui Gao ¹Rong Liu ¹Yusong Fan ¹Guian Qian ²Xiaolu Gui ¹R.D.K.Misrac ³Bingzhe Bai⁴

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作者信息

1. Material Science&Engineering Research Center,School of Mechanical,Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China
2. State Key Laboratory of Nonlinear Mechanics(LNM),Institute of Mechanics,Chinese Academy of Sciences,Beijing 100190,China
3. Laboratory for Excellence in Advanced Steel Research,Department of Metallurgical,Materials and Biomedical Engineering,University of Texas at El Paso,500W University Avenue,El Paso,TX 79968,USA
4. Material Science&Engineering Research Center,School of Mechanical,Electronic and Control Engineering,Beijing Jiaotong University,Beijing 100044,China;Key Laboratory of Advanced Material,School of Material Science and Engineering,Tsinghua University,Beijing 100084,China
折叠

Abstract

Advanced bainitic steels with the multiphase structure of bainitic ferrite,retained austenite and marten-site exhibit distinctive fatigue crack initiation behavior during high cycle fatigue/very high cycle fatigue(HCF/VHCF)regimes.The subsurface microstructural fatigue crack initiation,referred to as"non-inclusion induced crack initiation,NIICI",is a leading mode of failure of bainitic steels within the HCF/VHCF regimes.In this regard,there is currently a missing gap in the knowledge with respect to the cyclic response of multiphase structure during VHCF failure and the underlying mechanisms of fatigue crack initiation during VHCF.To address this aspect,we have developed a novel approach that explicitly identi-fies the knowledge gap through an examination of subsurface crack initiation and interaction with the lo-cal microstructure.This was accomplished by uniquely combining electron microscopy,three-dimensional confocal microscopy,focused ion beam,and transmission Kikuchi diffraction.Interestingly,the study indi-cated that there are multiple micro-mechanisms responsible for the NIICI failure of bainitic steels,includ-ing two scenarios of transgranular-crack-assisted NIICI and two scenarios of intergranular-crack-assisted NIICI,which resulted in the different distribution of fine grains in the crack initiation area.The fine grains were formed through fragmentation of bainitic ferrite lath caused by localized plastic deformation or via local continuous dynamic recrystallization because of repeated interaction between slip bands and prior austenite grain boundaries.The formation of fine grains assisted the advancement of small cracks.An-other important aspect discussed is the role of retained austenite(RA)during cyclic loading,on crack ini-tiation and propagation in terms of the morphology,distribution and stability of RA,which determined the development of localized cyclic plastic deformation in multiphase structure.

Key words

Microstructure/Advanced bainitic steels/Very high cycle fatigue/Mechanism/Retained austenite

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基金项目

authors(at BJT and TU)gratefully acknowledge the fund-ing by National Key Technologies Research and Development Pro-gram of (2017YFB0304500)

G.Gao and B.Bai acknowl-edge the support from National Natural Science Foundation of China(51771014)

and Joint Funds of National Natural Sci-ence Foundation of China(U1834202)

出版年

2022

材料科学技术(英文版)

中国金属学会中国材料研究学会中国科学院金属研究所

材料科学技术(英文版)

CSTPCDCSCDSCI

影响因子：0.657

ISSN：1005-0302

参考文献量70

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