Effect of Bainite to Ferrite Yield Strength Ratio on the Deformability of Mesostructures for Ferrite/Bainite Dual-Phase Steels

The strength and plasticity balance of F/B dual-phase X80 pipeline steels strongly depends on deformation compatibility between the soft phase of ferrite and the hard phase of bainite; thus, the tensile strength of ferrite and bainite, as non-negligible factors affecting the deformation compatibilit...

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Bibliographic Details
Published in:Materials 2021-09, Vol.14 (18), p.5352
Main Authors: Qiao, Gui-Ying, Zhao, Zhong-Tao, Shi, Xian-Bo, Shan, Yi-Yin, Gu, Yu, Xiao, Fu-Ren
Format: Article
Language:English
Subjects:
Bainite
Compatibility
Cooling
Deformation
Deformation effects
Dual phase steels
Elongation
Formability
High strength low alloy steels
Mechanical properties
Morphology
Steel
Strain concentration
Strain hardening
Strain localization
Stress concentration
Structural steels
Tensile properties
Tensile strength
Yield strength
Yield stress
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Summary:The strength and plasticity balance of F/B dual-phase X80 pipeline steels strongly depends on deformation compatibility between the soft phase of ferrite and the hard phase of bainite; thus, the tensile strength of ferrite and bainite, as non-negligible factors affecting the deformation compatibility, should be considered first. In this purely theoretical paper, an abstract representative volume elements (RVE) model was developed, based on the mesostructure of an F/B dual-phase X80 pipeline steel. The effect of the yield strength difference between bainite and ferrite on tensile properties and the strain hardening behaviors of the mesostructure was studied. The results show that deformation first occurs in ferrite, and strain and stress localize in ferrite prior to bainite. In the modified Crussard-Jaoul (C-J) analysis, as the yield strength ratio of bainite to ferrite (σy,B/σy,F) increases, the transition strain associated with the deformation transformation from ferrite soft phase deformation to uniform deformation of ferrite and bainite increases. Meanwhile, as the uncoordinated deformation of ferrite and bainite is enhanced, the strain localization factor (SLF) increases, especially the local strain concentration. Consequently, the yield, tensile strength, and yield ratio (yield strength/tensile strength) increase with the increase in σy,B/σy,F. Inversely, the strain hardening exponent and uniform elongation decrease.
ISSN:1996-1944
1996-1944
DOI:10.3390/ma14185352