Disconnections, dislocations and generalized disclinations in grain boundary ledges

Sun, Xiaoyu; Fressengeas, Claude; Taupin, Vincent; Cordier, Patrick; Combe, Nicolas

doi:10.1016/j.ijplas.2018.02.003

Cited by 23 publications

(17 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is definitely possible that other twin boundaries may have lower barriers to shear, thus enabling the activation of the shear-coupled migration at a wider range lower mantle conditions and grain sizes ( > 10 μm ) (Yamazaki et al 1996). Furthermore, at large grain sizes, shear-coupled migration may be facilitated by mechanisms such as disconnection nucleation (Han et al 2018;Rajabzadeh et al 2013;Sun et al 2018); however, the acute dependence of such mechanisms on the shear modulus of the material will likely be a limiting factor.…”

Section: Migration Energy Barrier and Critical Stressmentioning

confidence: 99%

The discontinuous effect of pressure on twin boundary strength in MgO

et al. 2020

View full text Add to dashboard Cite

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.

show abstract

Section: Migration Energy Barrier and Critical Stressmentioning

confidence: 99%

The discontinuous effect of pressure on twin boundary strength in MgO

et al. 2020

View full text Add to dashboard Cite

show abstract

“…Recent results indicate that the mechanism entails the glide of disconnections in the grain boundary. Unit disconnection motion is observed in several computer simulations and experiments (32,(55)(56)(57)(58), including the detailed formation and motion of disconnection by a kink pair mechanism (57). Cordier et al (6) suggested that disclination motion was a mechanism for GBS.…”

Section: Diffusional Creep With Grain Boundaries As Sources and Sinksmentioning

confidence: 99%

“…Furthermore, the wording in ref. 58 does not convey the nature of the elastic strain fields, specifically, that of a dislocation for unit defects and that of disclinations for defects with larger steps. Hence, we propose precept [9] in general.…”

Section: Diffusional Creep With Grain Boundaries As Sources and Sinksmentioning

confidence: 99%

Disclinations and disconnections in minerals and metals

Hirth

Wang

2019

Proc. Natl. Acad. Sci. U.S.A.

View full text Add to dashboard Cite

A different type of defect, the coherency disclination, is added to disclination types. Disconnections that include disclination content are considered. A criterion is suggested to distinguish disconnections with dislocation content from those with disclination content. Electron microscopy reveals unit disconnections in a low albite grain boundary, defects important in grain boundary sliding. Disconnections of varying step heights are displayed and shown to define both deformed and recovered structures.

show abstract

“…This was shown above from the examples of straight and stepped Σ5(310)[001] symmetrical tilt boundaries in Cu. The description of the grain boundaries used the distortion and second-order distortion fields, as obtained from atomic displacements by the discrete-to-continuum method of Sun et al [2016Sun et al [ , 2018. Discontinuities in the displacement, rotation and strain fields were found across the boundaries, pointing at the presence of dislocation and g-disclination fields in these areas.…”

Section: Resultsmentioning

confidence: 99%

“…Several trials were made from different initial configurations and the final configuration with the lowest energy was retained. Then, following the discrete-to-continuum method detailed in Sun et al [2016Sun et al [ , 2018, elastic displacement, distortion and second-order distortion fields were built, on the basis of the atomic displacements between the initial and final configurations, in a continuum superimposed to the atomic configuration at the same scale. The analysis reveals a plane state of distortion and second-order distortion along the (e 1 , e 2 ) symmetry plane of the boundary, and localized areas where the elastic displacement and distortion fields encounter sharp jumps interpreted as discontinuities across the boundary 1 .…”

Section: Symmetrical Tilt Boundariesmentioning

confidence: 99%

On the theory of dislocation and generalized disclination fields and its application to straight and stepped symmetrical tilt boundaries

Fressengeas

2020

Journal of the Mechanics and Physics of Solids

View full text Add to dashboard Cite

The theory of dislocation and generalized dislocation fields is developed within a second-order mechanical framework where the description of the internal state of the body and the balance equations involve the stress and hyper-stress tensors, work-conjugates to the strain and second-order distortion tensors. Consistently, the free energy density depends on the elastic strain and second-order distortion tensors. To obtain a continuous setting, the theory uses the duality between the discontinuity of the elastic displacement vector and distortion tensor fields and the incompatibility of the smooth second-order elastic distortion field. The conservation of these discontinuities across arbitrary patches provides transport relationships for the motion of dislocations and generalized disclinations serving as a kinematic basis for the description of plasticity and phase transformation. Closure of the theory derives from constitutive relationships for the mobility of dislocations and generalized disclinations compatible with the thermodynamic requirement of positive dissipation. In contrast with dislocations, the driving forces for generalized disclinations involve the hyper-stress tensor, not the stress tensor. The resulting theory is able to address boundary value problems for the elasto-plasticity of solids coupled with phase transformation along arbitrary loading paths. We provide examples showing generalized disclination distributions in plane state situations such as straight symmetrical tilt boundaries and symmetrical tilt boundaries involving steps and ledges.

show abstract

Disconnections, dislocations and generalized disclinations in grain boundary ledges

Cited by 23 publications

References 37 publications

The discontinuous effect of pressure on twin boundary strength in MgO

The discontinuous effect of pressure on twin boundary strength in MgO

Disclinations and disconnections in minerals and metals

On the theory of dislocation and generalized disclination fields and its application to straight and stepped symmetrical tilt boundaries

Contact Info

Product

Resources

About