The role of grain boundaries on fatigue crack initiation – An energy approach

Sangid, Michael D.; Maier, Hans Jürgen; Şehitoğlu, Hüseyin

doi:10.1016/j.ijplas.2010.09.009

Cited by 223 publications

(98 citation statements)

References 73 publications

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“…An analogy ARTICLE may be made to fatigue in FCC-base alloys, where S3 CTBs are also found to initiate cracks 19,20 . Under cyclic loading, crack initiation at CTBs has been tied to localization of dislocation activity along persistent slip bands that intersect CTBs and within the boundaries themselves [21][22][23] .…”

Section: Discussionmentioning

confidence: 99%

The dual role of coherent twin boundaries in hydrogen embrittlement

et al. 2015

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Hydrogen embrittlement (HE) causes engineering alloys to fracture unexpectedly, often at considerable economic or environmental cost. Inaccurate predictions of component lifetimes arise from inadequate understanding of how alloy microstructure affects HE. Here we investigate hydrogen-assisted fracture of a Ni-base superalloy and identify coherent twin boundaries (CTBs) as the microstructural features most susceptible to crack initiation. This is a surprising result considering the renowned beneficial effect of CTBs on mechanical strength and corrosion resistance of many engineering alloys. Remarkably, we also find that CTBs are resistant to crack propagation, implying that hydrogen-assisted crack initiation and propagation are governed by distinct physical mechanisms in Ni-base alloys. This finding motivates a re-evaluation of current lifetime models in light of the dual role of CTBs. It also indicates new paths to designing materials with HE-resistant microstructures.

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Section: Discussionmentioning

confidence: 99%

The dual role of coherent twin boundaries in hydrogen embrittlement

et al. 2015

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“…When applied to Ni-based superalloys, grain boundary engineering has been shown to increase resistance to fatigue crack growth and extend the high cycle fatigue life [19,20]. When either a large grain or a cluster of grains within a polycrystalline microstructure are favorably oriented for planar slip, cyclic deformation conditions may lead to the formation of persistent slip bands that effectively serve as precursors for nucleation of fatigue cracks [21]. Since the length of the persistent slip bands determine the likelihood of crack nucleation, populating the microstructure with a high density of Σ3 twin or high-CSL boundaries will serve to inhibit slip transmission across these boundaries and effectively limit their overall length [21].…”

Section: Introductionmentioning

confidence: 99%

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Detrois

Rotella

Hardy

et al. 2017

Integr Mater Manuf Innov

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Traditionally, material design and property modifications are usually associated with compositional changes. Yet, subtle changes in the manufacturing process parameters can also have a dramatic effect on the resulting material properties. In this work, an integrated computational materials engineering (ICME) framework is adopted to tailor the fatigue performance of a Ni-based superalloy, RR1000. An existing fatigue model is used to identify microstructural features that promote enhanced fatigue life, namely a uniform, fine grain size distribution, random orientation, a distinct grain boundary distribution (specifically high twin boundary density and limited low-angle grain boundaries). A deformation mechanism map and process models for grain boundary engineering of RR1000 are used to identify the optimal thermo-mechanical processing parameters to realize these desirable microstructural features. For validation, small-scale forgings of RR1000 were produced and heat-treated to attain fine grain and coarse grain microstructures that represent the conventionally processed and grain boundary engineered (GBE) conditions, respectively. For each of the four microstructural variants of RR1000, the twin density and grain size were characterized and were in agreement with the desired microstructural attributes. In order to validate the deformation mechanisms and fatigue behavior of the material, high-resolution digital image correlation was performed to generate strain maps relative to the microstructural features. The high density of twin boundaries was confirmed to inhibit the length of slip bands, which is directly attributed to extended fatigue life. Thus, this study demonstrated the successful role of models, both process and performance, in the design and manufacture of Ni-based superalloy disk forgings.

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“…It is clear that microstructuresensitive modelling methodologies are needed for the capture of the phenomena leading to FCI and, thus, HCF failure. Sangid et al [19][20][21] have developed a dislocation-driven criterion for the prediction of FCI based on the stability of an energy balance for PSB formation, including terms for dislocation-grain boundary interaction determined via atomistic simulations. Microstructure-sensitive fatigue indicator parameters (FIPs) coupled with CP modelling represents another approach.…”

Section: Introductionmentioning

confidence: 99%

Micro-scale testing and micromechanical modelling for high cycle fatigue of CoCr stent material

Sweeney

O’Brien

Dunne

et al. 2015

Journal of the Mechanical Behavior of Biomedical Materials

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This paper presents a framework of experimental testing and crystal plasticity micromechanics for high cycle fatigue (HCF) of micro-scale L605 CoCr stent material.Micro-scale specimens, representative of stent struts, are manufactured via laser micromachining and electro-polishing from biomedical grade CoCr alloy foil. Crystal plasticity models of the micro-specimens are developed using a length scale-dependent, strain-gradient constitutive model and a phenomenological (power-law) constitutive model, calibrated from monotonic and cyclic plasticity test data. Experimental microstructural characterization of the grain morphology and precipitate distributions is used as input for the polycrystalline finite element (FE) morphologies. Two microstructure-sensitive fatigue indicator parameters are applied, using local and non-local (grain-averaged) implementations, for the phenomenological and length scale-dependent models, respectively, to predict fatigue crack initiation (FCI) in the HCF experiments.

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The role of grain boundaries on fatigue crack initiation – An energy approach

Cited by 223 publications

References 73 publications

The dual role of coherent twin boundaries in hydrogen embrittlement

The dual role of coherent twin boundaries in hydrogen embrittlement

Tailoring the Properties of a Ni-Based Superalloy via Modification of the Forging Process: an ICME Approach to Fatigue Performance

Micro-scale testing and micromechanical modelling for high cycle fatigue of CoCr stent material

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