Stress-driven migration of symmetrical 〈1 0 0〉 tilt grain boundaries in Al bicrystals

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

doi:10.1016/j.actamat.2009.07.036

Cited by 195 publications

(171 citation statements)

References 39 publications

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“…A nonzero σ 32 destroys the identity of the grains and induces coupled motion of this boundary. 4,20 It should be noted that this boundary remains coupled even at σ 32 = 0. Its spontaneous displacements up and down are accompanied by concurrent grain translations by geometrically prescribed amounts.…”

Section: Methodology Of Atomistic Simulations a Simulated Systemsmentioning

confidence: 99%

Thermodynamics of coherent interfaces under mechanical stresses. II. Application to atomistic simulation of grain boundaries

Frolov

Mishin

2012

Phys. Rev. B

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The thermodynamic theory of coherent interfaces developed in Part I of this work is applied to grain boundaries (GBs) subject to non-hydrostatic elastic deformations. We derive expressions for the GB free energy as the reversible work of GB formation under stress. We also present a generalized adsorption equation whose differential coefficients define the GB segregation, GB stress tensor, GB excess volume, and GB excess shear. The generalized adsorption equation generates a set of Maxwell relations describing cross-effects between different GB properties. The theory is applied to atomistic simulations of a symmetrical tilt GB in Cu and Cu-Ag alloys.Using a combination of molecular dynamics and Monte Carlo methods, we compute a number of GB excess quantities and their dependencies on the applied stresses, temperature and chemical composition in the grains.We also test several Maxwell relations and obtain excellent agreement between the theory and simulations.

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Section: Methodology Of Atomistic Simulations a Simulated Systemsmentioning

confidence: 99%

Thermodynamics of coherent interfaces under mechanical stresses. II. Application to atomistic simulation of grain boundaries

Frolov

Mishin

2012

Phys. Rev. B

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“…This motion coupled to shear, commonly referred to as "coupled motion", is characterized by a relationship v = βv n between the translation velocity of the two grains parallel to the GB plane, v , and the GB velocity normal to this plane, v n . For symmetric tilt GBs, analytical predictions for the coupling factor β(θ) (where θ is the misorientation) based on geometrical arguments have been validated by both MD simulations 33 and experiments 37,38 .…”

Section: Introductionmentioning

confidence: 99%

“…In contrast, a low angle dry GB with intact solid bridges in between isolated dislocations with premelted cores would be expected to support shear more like a static solid. However, both theoretical [32][33][34][35][36] and experimental [37][38][39] studies over the last decade have shown that a dry GB generically moves normal to itself under an applied shear stress. This motion coupled to shear, commonly referred to as "coupled motion", is characterized by a relationship v = βv n between the translation velocity of the two grains parallel to the GB plane, v , and the GB velocity normal to this plane, v n .…”

Section: Introductionmentioning

confidence: 99%

Phase-field-crystal study of grain boundary premelting and shearing in bcc iron

et al. 2013

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We use the phase-field-crystal (PFC) method to investigate the equilibrium premelting and nonequilibrium shearing behaviors of [001] symmetric tilt grain boundaries (GBs) at high homologous temperature over the complete range of misorientation 0 < θ < 90 • in classical models of bcc Fe. We characterize the dependence of the premelted layer width W as a function of temperature and misorientation. In addition, we compute the thermodynamic disjoining potential whose derivative with respect to W represents the structural force between crystal-melt interfaces due to the spatial overlap of density waves. The disjoining potential is also computed by molecular dynamics (MD) simulations, for quantitative comparison with PFC simulations, and coarse-grained amplitude equations (AE) derived from PFC that provide additional analytical insights. We find that, for GBs over an intermediate range of misorientation (θmin < θ < θmax), W diverges as the melting temperature is approached from below, corresponding to a purely repulsive disjoining potential, while for GBs outside this range (θ < θmin or θmax < θ < 90 • ), W remains finite at the melting point. In the latter case, W corresponds to a shallow attractive minimum of the disjoining potential. The misorientation range where W diverges predicted by PFC simulations is much smaller than the range predicted by MD simulations when the small dimensionless parameter ǫ of the PFC model is matched to liquid structure factor properties. However it agrees well with MD simulations with a lower ǫ value chosen to match the ratio of bulk modulus and solid-liquid interfacial free-energy, consistent with the amplitude-equation prediction that θmin and 90 • − θmax scale as ∼ ǫ 1/2 . The incorporation of thermal fluctuations in PFC is found to have a negligible effect on this range. In response to a shear stress parallel to the GB plane, GBs in PFC simulations exhibit coupled motion normal to this plane or sliding. Furthermore, the coupling factor exhibits a discontinuous change as a function of θ that reflects a transition between two coupling modes. Sliding is only observed over a range of misorientation that is a strongly increasing function of temperature for T /TM ≥ 0.8 and matches roughly the range where W diverges at the melting point. The coupling factor for the two coupling modes is in excellent quantitative agreement with previous theoretical predictions [J. W. Cahn, Y. Mishin, and A. Suzuki, Acta Mater. 54, 4953 (2006)].

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“…Moreover, the coupling shear is able to drastically decrease the minimum value of energy change. The critical shear stress τ c for initiating the dislocation emission process can be reduced significantly due to the existence of coupled shear during the migration process, especially in the case of high-angle boundary; and it is important to note that there is a critical coupling factor β c that corresponds to the minimum τ c , which indicates that the dislocations in NC materials can possibly be maximized by engineering the GB structure to obtain an appropriate value of β [31,33]. The predicted critical shear stress for initiating multiple dislocations that emit from disclinated GBs into grain interiors in multiple slip systems has also been validated by the existing MD simulations for a nanocrystalline Cu sample of 10 nm grain size.…”

Section: Discussionmentioning

confidence: 99%

“…The translation distance s is related to the normal migration distance m by a coupling factor β ¼ s=m [31]. The value of β is determined by the geometry of the GB concerned [31,32], and the maximum value of β can reach 1 based on experiments [27,33] and MD simulations [25,32] and reach 5 according to theoretical studies [34,35]. The coupled mode has been revealed as a very effective toughening mechanism in NC materials [36] and it can considerably enhance the intrinsic ductility of NC materials by incorporating with the conventional GB sliding process [37].…”

Section: Introductionmentioning

confidence: 99%

Enhancing dislocation emission in nanocrystalline materials through shear-coupled migration of grain boundaries

Soh

2014

Materials Science and Engineering: A

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a b s t r a c tA theoretical model has been developed to illustrate the effect of shear-coupled migration of grain boundaries on dislocation emission in nanocrystalline materials. The energy characteristics and critical shear stress τ c that is required to initiate the emission process were determined. The results obtained show that the dislocation emission can be considerably enhanced as shear-coupled migration was the dominating process; a critical coupling factor that corresponded to the minimum τ c , which led to an optimal dislocation emission, was also discovered. The proposed model has also been quantitatively validated by the existing molecular dynamics simulations.

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Stress-driven migration of symmetrical 〈1 0 0〉 tilt grain boundaries in Al bicrystals

Cited by 195 publications

References 39 publications

Thermodynamics of coherent interfaces under mechanical stresses. II. Application to atomistic simulation of grain boundaries

Thermodynamics of coherent interfaces under mechanical stresses. II. Application to atomistic simulation of grain boundaries

Phase-field-crystal study of grain boundary premelting and shearing in bcc iron

Enhancing dislocation emission in nanocrystalline materials through shear-coupled migration of grain boundaries

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