Atomistic simulation of grain boundary energetics – Effects of dopants

Millett, Paul C.; Selvam, R. Panneer; Bansal, Shubhra; Saxena, Ashok

doi:10.1016/j.actamat.2005.04.031

Cited by 91 publications

(43 citation statements)

References 21 publications

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“…These simulations show that solute atoms randomly positioned (or evolved through Monte Carlo techniques) at grain boundaries in nanocrystalline Cu can retard grain growth 29,82,86,87 and even reduce the grain boundary energy to zero in both general [86][87][88] and specific [89][90][91] Fig. 7 show that nanocrystalline Cu rapidly coarsens at 1200 K while the same structure with 5%Ta as Ta clusters (based on TEM images) acts to stabilize the nanocrystalline grain size.…”

Section: Modeling and Simulation Approachesmentioning

confidence: 99%

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Tschopp

Murdoch

Kecskes

et al. 2014

JOM

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It is a new beginning for innovative fundamental and applied science in nanocrystalline materials. Many of the processing and consolidation challenges that have haunted nanocrystalline materials are now more fully understood, opening the doors for bulk nanocrystalline materials and parts to be produced. While challenges remain, recent advances in experimental, computational, and theoretical capability have allowed for bulk specimens that have heretofore been pursued only on a limited basis. This article discusses the methodology for synthesis and consolidation of bulk nanocrystalline materials using mechanical alloying, the alloy development and synthesis process for stabilizing these materials at elevated temperatures, and the physical and mechanical properties of nanocrystalline materials with a focus throughout on nanocrystalline copper and a nanocrystalline Cu-Ta system, consolidated via equal channel angular extrusion, with properties rivaling that of nanocrystalline pure Ta. Moreover, modeling and simulation approaches as well as experimental results for grain growth, grain boundary processes, and deformation mechanisms in nanocrystalline copper are briefly reviewed and discussed. Integrating experiments and computational materials science for synthesizing bulk nanocrystalline materials can bring about the next generation of ultrahigh strength materials for defense and energy applications.

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Section: Modeling and Simulation Approachesmentioning

confidence: 99%

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Tschopp

Murdoch

Kecskes

et al. 2014

JOM

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“…37 For some of the binary alloy systems discussed above, solute enrichment at grain boundaries has been confirmed by atom probe tomography. [38][39][40][41] It has also been studied extensively by computer simulations both for individual grain boundaries 42 and, more recently, for simulated nanocrystalline structures. 36,43,44 A particularly clear illustration of the principle behind Eq.…”

Section: Introductionmentioning

confidence: 99%

Grain boundary segregation and thermodynamically stable binary nanocrystalline alloys

2009

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A free-energy function for binary polycrystalline solid solutions is developed based on pairwise nearestneighbor interactions. The model permits intergranular regions to exhibit unique energetics and compositions from grain interiors, under the assumption of random site occupation in each region. For a given composition, there is an equilibrium grain size, and the alloy configuration in equilibrium generally involves solute segregation. The present approach reduces to a standard model of grain boundary segregation in the limit of infinite grain size, but substantially generalizes prior thermodynamic models for nanoscale alloy systems. In particular, the present model allows consideration of weakly segregating systems, systems away from the dilute limit, and is derived for structures of arbitrary dimensionality. A series of solutions for the equilibrium alloy configuration and grain size are also presented as a function of simple input parameters, including temperature, alloy interaction energies, and component grain boundary energies.

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“…Atomistic simulations on nanocrystalline alloys show that structural stabilization is contingent upon the distribution and character of the solute atom. A certain minimum concentration of solute is often found to be necessary for grain size stabilization, as for various solute species in simulated copper [11][12][13][14][15][16][17]. The efficacy of different solute species is variable, and in some studies has been related to the size difference between solute and solvent atoms [11][12][13].…”

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Stability of binary nanocrystalline alloys against grain growth and phase separation

2013

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Grain boundary segregation has been established through both simulation and experiments as a successful approach to stabilize nanocrystalline materials against grain growth. However, relatively few alloy systems have been studied in this context; these vary in their efficacy, and in many cases the stabilization effect is compromised by second phase precipitation. Here we address the open-ended design problem of how to select alloy systems that may be stable in a nanocrystalline state. We continue the development of a general "regular nanocrystalline solution" model to identify the conditions under which binary nanocrystalline alloy systems with positive heats of mixing are stable with respect to both grain growth (segregation removes the grain boundary energy penalty) and phase separation (the free energy of the nanocrystalline system is lower than the common tangent defining the bulk miscibility gap). We calculate a "nanostructure stability map" in terms of alloy thermodynamic parameters. Three main regions are delineated in these maps: one where grain boundary segregation does not result in a stabilized nanocrystalline structure, one in which macroscopic phase separation would be preferential (despite the presence of a nanocrystalline state stable against grain growth), and one for which the nanocrystalline state is stable against both grain growth and phase separation. Additional details about the stabilized structures are also presented in the map, which can be regarded as a tool for the design of stable nanocrystalline alloys. Atomistic simulations on nanocrystalline alloys show that structural stabilization is contingent upon the distribution and character of the solute atom. A certain minimum concentration of solute is often found to be necessary for grain size stabilization, as for various solute species in simulated copper [11][12][13][14][15][16][17]. The efficacy of different solute species is variable, and in some studies has been related to the size difference between solute and solvent atoms [11][12][13]. However, in these studies, the grain boundaries are manually decorated with solute atoms, which may represent artificial segregation states. There have been fewer simulation works on systems where segregation is thermodynamic (by, e.g., Monte Carlo methods) [16][17][18][19][20]. These suggest that equilibrium solute segregation lowers the grain boundary energy to varying degrees. Experimentally, a reduction in the propensity for grain growth in nanocrystalline materials has been observed in a variety of binary alloys [21][22][23][24][25][26][27][28][29][30][31]. There are many indications in experimental systems that there is a "preferred" grain size which emerges during processing which is closely linked to the solute content [2,24,30,32,33]; this is considered significant evidence for a thermodynamic contribution to stabilization. The grain size that is stable against coarsening is correlated to the solute concentration in these systems, but the system also often exhibits instabilities w...

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Atomistic simulation of grain boundary energetics – Effects of dopants

Cited by 91 publications

References 21 publications

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

“Bulk” Nanocrystalline Metals: Review of the Current State of the Art and Future Opportunities for Copper and Copper Alloys

Grain boundary segregation and thermodynamically stable binary nanocrystalline alloys

Stability of binary nanocrystalline alloys against grain growth and phase separation

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