Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nano-cracks or precipitates

Luque, A.; Aldazábal, J.; Martı́nez-Esnaola, J.M.; Sevillano, J. Gil

doi:10.1080/14786430903097715

Cited by 5 publications

(2 citation statements)

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“…These include homogeneous nucleation from a free surface [17], dislocation-twin interactions [18][19][20][21], twin-twin interactions [22], and precipitation/void-induced nucleation [23,24]. The shear-coupled migration (SCM) phenomenon for grain boundary motion [25][26][27][28] has been extensively studied in terms of interfacial structure (coherency and grain-boundary dislocations or disconnections). New work has studied the solute-strengthening of a pre-existing twin dislocation moving along a pre-existing twin boundary in a material with a random solid solution [29].…”

Section: Introductionmentioning

confidence: 99%

A new mechanism for twin growth in Mg alloys

2014

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Twinning is an important deformation mode in lightweight Mg alloys, but the mechanisms of nucleation and growth of twins and their interactions with solutes remain largely unresolved. Here, a new model for thermally-activated, stress-driven growth of twin boundaries is presented and the role of random and segregated solutes in controlling this growth is studied analytically and using direct molecular dynamics simulations. Twin growth occurs by the thermallyactivated nucleation and expansion of twin dislocation loops on a pre-existing twin boundary. Fluctuations in the local concentration of random solutes lowers the energy barrier for this process and thus facilitates twin growth. Segregation of solutes to the twin boundary strongly increases the energy barrier and suppresses twin growth. In random solid solutions at experimental strain rates, the thermally-activated nucleation process is sufficiently fast at low applied stresses so that growth of the twin is controlled by solute strengthening of the nucleated twin loop as it expands across the twin boundary. Annealing of a deformed sample leads to solute segregation and very strong pinning so that further twinning can only be accomplished by nucleation of new twins, consistent with experimental observations. The new mechanism also (i) operates for detwinning and rationalizes complex twin shapes observed in experiments and (ii) suggests a process for dynamic strain aging commonly observed in Mg alloys at elevated temperatures.

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Section: Introductionmentioning

confidence: 99%

A new mechanism for twin growth in Mg alloys

2014

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“…In the recent contribution of Luque et al (2010), these authors did not consider the effective elastic properties of the bicrystal in the computation of the macroscopic plastic strain induced by shear-coupling GB migration (see their Eq. (2)).…”

Section: Model Results and Comparisons With Atomistic Simulationsmentioning

confidence: 99%

A micromechanics-based model for shear-coupled grain boundary migration in bicrystals

Berbenni

Paliwal

Cherkaoui

2013

International Journal of Plasticity

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International audienceA complete micromechanics-based model is here proposed using the concepts of continuum kinematics and thermodynamics. A new constitutive framework is proposed to describe stress-induced ``shear-coupled'' grain boundary (GB) migration. Like non diffusive phase-transformations, shear-coupled GB migration can be considered on the thermodynamics point of view of conservative nature until high temperature with respect to melting point (i.e., diffusionless but thermally activated). The micromechanics-based continuum model can include intra-crystalline slip, GB sliding and shear-coupled GB migration as additive dissipative mechanisms. To illustrate the present theory, the model is applied to shear-coupled GB migration in the case of three ``flat'' Cu bi-crystals [001] with symmetric tilt GB (STGB): Sigma 17(410) (theta = 28.07 degrees), Sigma 5(210) (theta = 53.13 degrees), Sigma 41(540) (theta = 77.32 degrees). Molecular dynamics (MD) simulations under simple shear loading are first performed to identify the active shear coupling modes, the stick-slip behavior at 0 K and 500 K and the bicrystal finite size dependence on the shear stress responses. The results of the micromechanical model are discussed in comparison with MD simulations. The effects of anisotropic vs. isotropic elastic properties on effective elastic shear Moduli, overall shear stress drop magnitudes and dissipated energy during GB migration are analyzed for these STGB

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An improved atomistic simulation based mixed-mode cohesive zone law considering non-planar crack growth

Paliwal

Cherkaoui

2013

International Journal of Solids and Structures

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Plastic deformation by conservative shear-coupled migration of tilt boundaries with intergranular nano-cracks or precipitates

Cited by 5 publications

References 56 publications

A new mechanism for twin growth in Mg alloys

A new mechanism for twin growth in Mg alloys

A micromechanics-based model for shear-coupled grain boundary migration in bicrystals

An improved atomistic simulation based mixed-mode cohesive zone law considering non-planar crack growth

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