On key factors influencing ductile fractures of dual phase (DP) steels

X, Sun; Choi, Kyoo Sil; Soulami, Ayoub; Liu, Wenning N.; Khaleel, Mohammad A.

doi:10.1016/j.msea.2009.08.010

Cited by 160 publications

(76 citation statements)

References 25 publications

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“…Even when presence of other phases such as retained austenite or bainite are not taken into account, the micromechanical behavior of the composite-like dual phase microstructure of DP http://dx.doi.org/10.1016/j.ijplas.2014.06.004 0749-6419/Ó 2014 Elsevier Ltd. All rights reserved. steels is rather complex (Tekoglu and Pardoen, 2010, Tekoglu et al, 2012, Kadkhodapour et al, 2011b,2011a, Sun et al, 2009a,2009b. Thus, following numerous reports on the mechanical performance of DP steel (which are typically based on conventional post-mortem microstructure characterization techniques), the microstructural strain and stress partitioning that governs the overall behavior of DP microstructures is still not fully understood.…”

Section: Introductionmentioning

confidence: 99%

Strain localization and damage in dual phase steels investigated by coupled in-situ deformation experiments and crystal plasticity simulations

Taşan

Hoefnagels

Diehl

et al. 2014

International Journal of Plasticity

444

176

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a b s t r a c tFerritic-martensitic dual phase (DP) steels deform spatially in a highly heterogeneous manner, i.e. with strong strain and stress partitioning at the micro-scale. Such heterogeneity in local strain evolution leads in turn to a spatially heterogeneous damage distribution, and thus, plays an important role in the process of damage inheritance and fracture. To understand and improve DP steels, it is important to identify connections between the observed strain and damage heterogeneity and the underlying microstructural parameters, e.g. ferrite grain size, martensite distribution, martensite fraction, etc. In this work we pursue this aim by conducting in-situ deformation experiments on two different DP steel grades, employing two different microscopic-digital image correlation (lDIC) techniques to achieve microstructural strain maps of representative statistics and high-resolution. The resulting local strain maps are analyzed in connection to the observed damage incidents (identified by image post-processing) and to local stress maps (obtained from crystal plasticity (CP) simulations of the same microstructural area). The results reveal that plasticity is typically initiated within ''hot zones'' with larger ferritic grains and lower local martensite fraction. With increasing global deformation, damage incidents are most often observed in the boundary of such highly plastified zones. High-resolution lDIC and the corresponding CP simulations reveal the importance of martensite dispersion: zones with bulky martensite are more susceptible to macroscopic localization before the full strain hardening capacity of the material is consumed. Overall, the presented joint analysis establishes an integrated computational materials engineering (ICME) approach for designing advanced DP steels.

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Section: Introductionmentioning

confidence: 99%

Strain localization and damage in dual phase steels investigated by coupled in-situ deformation experiments and crystal plasticity simulations

Taşan

Hoefnagels

Diehl

et al. 2014

International Journal of Plasticity

444

176

View full text Add to dashboard Cite

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“…However, in such higher strength grades (with higher martensite content), activity of microstructural damage mechanisms may often lead to unpredicted failures during forming operations or upon crash [21,22]. The limited understanding of the macroscopic fracture processes in DP steel arises from the presence of multiple microstructural damage mechanisms that exhibit complex interactions [23][24][25][26][27][28][29][30][31][32]. As a consequence, the applicability of state-of-the-art damage models that aim at modeling multiple, interacting, damage nucleation mechanisms, e.g., [33,34], is limited by the possibilities for experimental characterization, see e.g., [29,31].…”

Section: Introductionmentioning

confidence: 99%

Retardation of plastic instability via damage-enabled microstrain delocalization

et al. 2015

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Multi-phase microstructures with high mechanical contrast phases are prone to microscopic damage mechanisms. For ferrite-martensite dual-phase steel, for example, damage mechanisms such as martensite cracking or martensite-ferrite decohesion are activated with deformation, and discussed often in literature in relation to their detrimental role in triggering early failure in specific dualphase steel grades. However, both the micromechanical processes involved and their direct influence on the macroscopic behavior are quite complex, and a deeper understanding thereof requires systematic analyses. To this end, an experimental-theoretical approach is employed here, focusing on three model dual-phase steel microstructures each deformed in three different strain paths. The micromechanical role of the observed damage mechanisms is investigated in detail by in-situ scanning electron microscopy tests, quantitative damage analyses, and finite element simulations. The comparative analysis reveals the unforeseen conclusion that damage nucleation may have a beneficial mechanical effect in ideally designed dual-phase steel microstructures (with effective crack-arrest mechanisms) through microscopic strain delocalization.

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“…It has been repeatedly stressed in the literature [25][26][27] that the microstructural stress and strain heterogeneity that are due to martensite volume fraction and hardness, as well as the strength difference between the two phases, are the main sources of void formation and development in DP steels. In this study, we tried to simplify this complex problem by choosing three materials that have almost identical compositions for the two phases and were subjected to very similar heat-treatment patterns.…”

Section: Discussionmentioning

confidence: 99%

Effect of Martensite Volume Fraction on Void Formation Leading to Ductile Fracture in Dual Phase Steels

et al. 2014

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This study examines the ductile fracture of three dual-phase steels that contain low volume fractions of martensite (3.2%, 6.2% and 10%) and are composed of nearly the same quality of ferrite and martensite. The strains to rupture of the DP steel with 3.2% martensite are considerably higher than those of the DP steels with 6.2% and 10% martensite. The evolution of voids with respect to equivalent plastic strain, which is transformed from the thickness reduction of the specimen, was analyzed by SEM observation in fractured tensile specimens. The observation clarified the fact that the evolution of void size saturates at the specific strain in the DP steel with 3.2% martensite, whereas the void size in the DP steels with 6.2% and 10% martensite grows exponentially with strain. This significant favorable behavior of the DP steel with 3.2% martensite is probably caused by the relatively low heterogeneity of the stress and strain partitioning between the two phases, which allows attaining a significant higher ductility of this steel.

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On key factors influencing ductile fractures of dual phase (DP) steels

Cited by 160 publications

References 25 publications

Strain localization and damage in dual phase steels investigated by coupled in-situ deformation experiments and crystal plasticity simulations

Strain localization and damage in dual phase steels investigated by coupled in-situ deformation experiments and crystal plasticity simulations

Retardation of plastic instability via damage-enabled microstrain delocalization

Effect of Martensite Volume Fraction on Void Formation Leading to Ductile Fracture in Dual Phase Steels

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