Analysis of size effects associated to the transformation strain in TRIP steels with strain gradient plasticity

Mazzoni-Leduc, L.; Pardoen, Thomas; Massart, Thierry

doi:10.1016/j.euromechsol.2009.08.001

Cited by 12 publications

(6 citation statements)

References 44 publications

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“…If this was the case, one should expect that this effect and its consequences like the TRIP effect should be amplified when the test temperature is decreased. The nature of work-hardening in multi-phased materials due to a TRIP effect is very much dictated by SGP effects connected to the submicron size of the transforming domains [125,126].…”

Section: Deformation Mechanisms In Nc and Ufg Multiphased Metalsmentioning

confidence: 99%

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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a b s t r a c tPushing the internal or external dimensions of metallic alloys down to the nanometer scale gives rise to strong materials, though most often at the expense of a low ductility and a low resistance to cracking, with negative impact on the transfer to engineering applications. These characteristics are observed, with some exceptions, in bulk ultra-fine grained and nanocrystalline metals, nano-twinned metals, thin metallic coatings on substrates and freestanding thin metallic films and nanowires. This overview encompasses all these systems to reveal commonalities in the origins of the lack of ductility and fracture resistance, in factors governing fatigue resistance, and in ways to improve properties. After surveying the various processing methods and key deformation mechanisms, we systematically address the current state of the art in terms of plastic localization, damage, static and fatigue cracking, for three classes of systems: (1) bulk ultra-fine grained and nanocrystalline metals, (2) thin metallic films on substrates, and (3) 1D and 2D freestanding micro and nanoscale systems. In doing so, we aim to favour cross-fertilization between progress made in the fields of mechanics of thin films, nanomechanics, fundamental researches in bulk nanocrystalline metals and metallurgy to impart enhanced resistance to fracture and fatigue in high-strength nanostructured systems. This involves exploiting intrinsic mechanisms, e.g. to enhance hardening and rate-sensitivity so as to delay necking, or improve grain-boundary cohesion to resist intergranular cracks or voids. Extrinsic methods can also be utilized such as by hybridizing the metal with another material to delocalize the deformation -as practiced in stretchable electronics. Fatigue crack initiation is in principle improved by a fine structure, but at the expense of larger fatigue crack growth rates. Extrinsic toughening through hybridization allows arresting or bridging cracks. The content and discussions are based on experimental, theoretical and simulation results from the recent literature, and focus is laid on linking microstructure and physical mechanisms to the overall mechanical behavior.

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Section: Deformation Mechanisms In Nc and Ufg Multiphased Metalsmentioning

confidence: 99%

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

2016

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“…The plastic flow is initially constrained by using the cohesive zone to impose the condition εp = 0 through a penalty term at the boundary of the grain interior. Upon further straining, the confinement condition can be modified [44][45][46][47] based on a condition on the local (conventional) stress carried by the CZ. The condition for relaxing the higher order confining effect is formulated in terms of the CZ von Mises stress as…”

Section: Model For the Interface Layermentioning

confidence: 99%

“…More advanced models rely on crystal plasticity descriptions [42,43]. In the spirit of these studies, we have developed a generic approach of interfaces [36,[44][45][46][47] in the context of a finite element model relying on a finite strain implementation of the strain gradient plasticity theory of Fleck and Hutchinson [48]. Cohesive zones are used to represent the interface layers, together with higher order boundary conditions.…”

Section: Introductionmentioning

confidence: 99%

Interface controlled plastic flow modelled by strain gradient plasticity theory

Pardoen

Massart

2012

Comptes Rendus. Mécanique

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The resistance to plastic flow in metals is often dominated by the presence of interfaces which interfere with dislocation nucleation and motion. Interfaces can be static such as grain and phase boundaries or dynamic such as new boundaries resulting from a phase transformation. The interface can be hard and fully impenetrable to dislocations, or soft and partly or fully transparent. The interactions between dislocations and interfaces constitute the main mechanism controlling the strength and strain hardening capacity of many metallic systems especially in very fine microstructures with a high density of interfaces. A phenomenological strain gradient plasticity theory is used to introduce, within a continuum framework, higher order boundary conditions which empirically represent the effect of interfaces on plastic flow. The strength of the interfaces can evolve during the loading in order to enrich the description of their response. The behaviour of single and dual phase steels, with possible TRIP effect, accounting for the interactions with static and dynamic boundaries, is addressed, with a specific focus on the size dependent strength and ductility balance. The size dependent response of weak precipitate free zones surrounding grain boundaries is treated as an example involving more than one microstructural length scale.

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“…Upon further straining, the confinement condition can be modified [19,33] based on a condition on the local (conventional) stress carried by the CZ. The condition for relaxing the higher-order confining effect is formulated in terms of the CZ von Mises stress as:…”

Section: Modelmentioning

confidence: 99%

Strain gradient plasticity analysis of the strength and ductility of thin metallic films using an enriched interface model

Brugger¹,

Coulombier²,

Massart³

et al. 2010

Acta Materialia

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The mechanical response of thin metallic films is simulated using a two-dimensional strain gradient plasticity finite-element model involving grain boundaries in order to investigate the effect of the thickness, grain shape and surface constraint on the strength, ductility and back-stress. The grain boundaries and surface layers are modeled as initially impenetrable to dislocations while allowing for relaxation at a critical stress level. The model captures the variation of the strength with grain size, film thickness, and with the presence or not of constraining surface layers, in agreement with experimental results on Al and Cu films. A decrease in the uniform elongation is predicted with decreasing film thickness due to a loss of strain-hardening capacity and the possible presence of imperfections. These two effects dominate over the stabilizing contribution of the plastic strain gradients. Accounting for the relaxation of the interface constraint affects the magnitude of the back-stress as well as the drop in ductility.

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Analysis of size effects associated to the transformation strain in TRIP steels with strain gradient plasticity

Cited by 12 publications

References 44 publications

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

Failure of metals III: Fracture and fatigue of nanostructured metallic materials

Interface controlled plastic flow modelled by strain gradient plasticity theory

Strain gradient plasticity analysis of the strength and ductility of thin metallic films using an enriched interface model

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