Concurrent grain boundary motion and grain rotation under an applied stress

Gorkaya, Tatiana; Molodov, Konstantin D.; Molodov, Dmitri A.; Gottstein, Günter

doi:10.1016/j.actamat.2011.05.042

Cited by 120 publications

(66 citation statements)

References 25 publications

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“…Also, it appears that direct experimental evidence for zero free grain boundary energies, i.e., the absence of grooving at grain boundaries intersecting a free surface, does not exist. An additional complication is found in the work of Gorkaya et al 11) who have shown that grain boundary migration may be driven not only by the grain boundary free energy, but also by an externally applied shear stress. Therefore, even when the grain boundary free energy is zero, grain coarsening may occur during mechanical testing.…”

Section: Introductionmentioning

confidence: 91%

Hall–Petch Breakdown at Elevated Temperatures

Schneibel¹,

Heilmaier

2014

Mater. Trans.

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The HallPetch effect responsible for the strength of fine-grained and ultrafine-grained (UFG) metals is almost exclusively measured at room temperature. One reason for this is that at elevated temperatures grains tend to coarsen, and this negates the strengthening. The grains may, however, be stabilized by small volume fractions of fine dispersoids. These dispersoids cause direct Orowan strengthening and, by stabilizing the so-called Zener grain size, indirect strengthening due to HallPetch. We show that for most metals the critical Zener grain size above which HallPetch strengthening is more important than Orowan strengthening is lower than, and sometimes even considerably lower than 1 µm, i.e., in the range of UFG metals. Breakdown of the HallPetch relationship, which occurs at elevated temperatures once mechanisms weaker than Hall Petch start to control the strength, is best studied for grain sizes well above this critical grain size. The HallPetch breakdown due to either Coble creep or grain size-dependent dislocation creep is modeled. We present model calculations for copper and verify our approach by comparing with experimental results for ferritic steels containing nanoscale dispersions.

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Section: Introductionmentioning

confidence: 91%

Hall–Petch Breakdown at Elevated Temperatures

Schneibel¹,

Heilmaier

2014

Mater. Trans.

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“…The GB S is considered to be of a mixed type, with both tilt and twist components, where the misorientation is given by Θ = I + θ 1 (e 1 ×) + θ 3 (e 3 ×) for small θ 1 and θ 3 , where (e×) represents a skew tensor with components given by (e×) jk = ε jlk e l (here ε jlk is the permutation symbol); as discussed in appendix A, θ 1 and θ 3 determine the twist and the tilt characteristic, respectively, of the GB. Whereas the deformation of grains in the wake of a moving GB, under the external loading considered here, is simple shear for a tilt GB, it is more complicated if the GB is of mixed type [7]. The array of edge dislocations is driven by the Peach-Koehler force to move the GB in normal direction while translating the grains parallel to the GB.…”

Section: (A) Bicrystal-imentioning

confidence: 99%

“…This is unlike coarse-grained materials where GB migration and dislocation dynamics dominate grain coarsening and plastic deformation, respectively. The coupled motion has recently been studied theoretically [1,2,5,6], experimentally [7] and with molecular simulations [8]. Although some of these studies have included the effect of junction dynamics [2,8], all of them are restricted to two-dimensional grains and hence applicable only to polycrystals where each grain is columnar and identical in cross section along the length direction; such a restriction requires the GB to have only tilt, and no twist, character.…”

Section: Introductionmentioning

confidence: 99%

A three-dimensional study of coupled grain boundary motion with junctions

Basak

Gupta

2015

Proc. R. Soc. A.

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A novel continuum theory of incoherent interfaces with triple junctions is applied to study coupled grain boundary (GB) motion in three-dimensional polycrystalline materials. The kinetic relations for grain dynamics, relative sliding and migration of the boundary and junction evolution are developed. In doing so, a vectorial form of the geometrical coupling factor, which relates the tangential motion at the GB to the migration, is also obtained. Diffusion along the GBs and the junctions is allowed so as to prevent nucleation of voids and overlapping of material near the GBs. The coupled dynamics has been studied in detail for two bicrystalline and one tricrystalline arrangements. The first bicrystal consists of two cubic grains separated by a planar GB, whereas the second is composed of a spherical grain embedded inside a larger grain. The tricrystal has an arbitrary-shaped grain embedded inside a much larger bicrystal made of two cubic grains. In all these cases, analytical solutions are obtained wherever possible while emphasizing the role of various kinetic coefficients during the coupled motion.

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“…Two general NGG modes have been identified by various researchers, i.e., nano-grain rotation (NGR) and shear-coupled migration (SCM) of grain boundaries [4][5][6][7][8][9][10][11]. Moreover, as demonstrated by many experiments and molecular dynamics as well as mesoscale simulations [4,12,13], NGG and SCM usually appear concomitantly. Most recently, Li et al [14] predicted a novel coupling behavior of NGR and SCM in their theoretical model, i.e., under an externally applied load, NGR occurred first, which led to a decrease of the initial misorientation parameter θ 0 of a given GB and subsequently SCM appeared, which was called a cooperative NGR-SCM process.…”

Section: Introductionmentioning

confidence: 99%