Shear-coupled grain-boundary migration dependence on normal strain/stress

Combe, Nicolas; Mompiou, Frédéric; Legros, Marc

doi:10.1103/physrevmaterials.1.033605

Cited by 15 publications

(9 citation statements)

References 34 publications

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“…In some materials, this deformation mode is more effective at enhancing plastic deformation than more common deformation mechanisms such as pure grain boundary sliding (Molodov and Molodov 2018). However, it is also becoming clear that the character of the particular grain boundary or interface plays a significant role in determining the efficiency of shear-coupled migration, with different grain boundaries having very different shear strengths (Combe et al 2017).…”

Section: Introductionmentioning

confidence: 99%

The discontinuous effect of pressure on twin boundary strength in MgO

et al. 2020

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MgO makes up about 20% of the Earth's lower mantle; hence, its rheological behaviour is important for the dynamics and evolution of the Earth. Here, we investigate the strength of twin boundaries from 0 to 120 GPa using DFT calculations together with structure prediction methods. As expected, we find that the energy barrier and critical stress for shear-coupled migration of the 310/[001] interface vary strongly with pressure. However, what is surprising is that the twin boundary also exhibits sudden strong discontinuities in strength which can both weaken and strengthen the boundary with increasing pressure. Since twin boundary migration is a proposed mechanism for both deformation and seismic attenuation in MgO, these results may suggest that MgO can undergo sudden changes in rheology due to transitions in grain boundary structure. The multiplicity of interfaces, however, necessitates the need for further studies to examine the role that phase changes in grain boundary structure play in mediating polycrystalline plasticity in the Earth.

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Section: Introductionmentioning

confidence: 99%

The discontinuous effect of pressure on twin boundary strength in MgO

et al. 2020

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“…In fact, atomistic simulations of real GBs are only beginning, addressing the possible influence of defects present prior to deformation such as vacancies [78] or immobile disconnections [79]. A second reason for the current mismatch between the observed and simulated coupling factors may be the complex stress tensor acting locally on real GBs in small-grained metals whereas atomistic simulations involve perfectly defined and often homogenous stress states [80]. These two factors may explain why many more disconnections could be activated in real metals at lower stresses and coupling factors while the nucleation step and strictly imposed strain directions favor a given disconnection that may have a large coupling factor in simulations.…”

Section: Discussionmentioning

confidence: 99%

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Gautier¹,

Rajabzadeh²,

Larranaga³

et al. 2021

Comptes Rendus. Physique

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“…A disconnection is a GB defect with both a step and a dislocation character. Both experiments and simulations have evidenced the role of these disconnections during the SCGBM [15,16,17,18,13,19,8,9,20,21,22]. The coupling factor of the SCGBM is directly related to the ratio of the (norm of the) Burgers vector to the step height of the mobile disconnection.…”

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confidence: 93%

“…Cahn et al [3] have predicted for instance, in FCC crystals, four coupling modes in symmetric [001]-tilt GBs. While three of them have been evidenced in Molecular dynamics simulations [3,6,7,8,9], only two modes have been experimentally observed in macroscopic sheared Al bicrystals [10,11,12].…”

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confidence: 99%

Multiple coupling modes to relax shear strain during grain boundary migration

Combe

Mompiou²,

Legros³

2021

Acta Materialia

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Shear-coupled grain boundary (GB) migration is an effective plastic mechanism in absence of dislocation activity, ie. more favorably in nanocrystalline metals. For a given GB, several stress induced migration mechanisms, referred as coupling modes participate to the decrease of the elastic energy produced by the shear. They operate through the nucleation and motion of interfacial defects known as disconnections, carrying elementary shear strain characterized by their Burgers vector. However, so far, the coupling modes have been studied only under a simple shear, a situation much less complex than expected in a strained polycrystal, where multiple components of the stress tensor are present. Here we propose a more systematic investigation of the coupling modes when a composite shear is applied. This promotes the activation of new coupling modes. Using Molecular Dynamics simulations, we evidence these multiple coupling modes and the operation of their associate disconnections. Moreover, we also show that, even at low temperature, GB migration may occur by the successive occurrence of two modes: the relaxed shear appears then as an effective parameter, resulting from the combination of two operating elementary mechanisms.

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Shear-coupled grain-boundary migration dependence on normal strain/stress

Cited by 15 publications

References 34 publications

The discontinuous effect of pressure on twin boundary strength in MgO

The discontinuous effect of pressure on twin boundary strength in MgO

Shear-coupled migration of grain boundaries: the key missing link in the mechanical behavior of small-grained metals?

Multiple coupling modes to relax shear strain during grain boundary migration

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