Grain Growth Stagnation Caused by the Grain Boundary Roughening Transition

2012 ◽  
Vol 715-716 ◽  
pp. 415-415
Author(s):  
Elizabeth A. Holm ◽  
Stephen M. Foiles
Keyword(s):  
Molecular Dynamics ◽  
Transition Temperature ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Growth ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Annealing Temperatures ◽  
Roughening Transition ◽  
Dynamics Simulations

Molecular dynamics simulations of bicrystals show that grain boundaries undergo a thermal roughening transition, and the grain boundary mobility increases abruptly when the boundary roughens. The roughening transition temperature varies widely from boundary to boundary, ranging from less than 0.4 to more than 0.9 of the melting temperature. Thus, at typical annealing temperatures we expect polycrystals to contain both smooth (slow) and rough (fast) boundaries, with the fraction of each type varying with temperature.

Multiscale Simulations of Anisotropic Grain Growth Using Wavelet Based Multiresolution Analysis

2016 ◽  
Vol 83 (10) ◽  
Author(s):  
J. B. Allen
Keyword(s):  
Molecular Dynamics ◽  
Monte Carlo ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Growth ◽  
Multiresolution Analysis ◽  
Wavelet Transforms ◽  
Multiscale Simulation ◽  
Inherent Anisotropy ◽  
Dynamics Simulations

The present work serves to document the development and findings associated with a wavelet-based multiscale simulation analysis for anisotropic grain growth of a two-dimensional polycrystalline material. In particular, lattice-based Monte Carlo and atomically-based Molecular Dynamics simulations are used to compute the grain boundary energies over their respective spatial domains. Serial coupling is performed utilizing an orthonormal set of Haar wavelet transforms embedded within a corresponding multiresolution analysis. For the Monte Carlo approach, anisotropies in grain boundary energies, caused by differences in grain orientation (texturing), are examined using two distinct methods, while the molecular dynamics simulations, offering inherent anisotropy, are conducted assuming the interatomic Lennard Jones potential. Among other findings, under the present context, the results confirm the viability of the wavelet-based multiresolution analysis (MRA) method for use as a potential coupling agent, and provide substantiation for its use with other applications. The results further offer quantitative comparisons between isotropic and anisotropic modeling results, and demonstrate their range of applicability.

Grain Boundary Roughening Transition

2004 ◽  
Vol 467-470 ◽  
pp. 825-834 ◽  
Author(s):  
Duk Yong Yoon ◽  
Young Kyu Cho ◽  
Hyun Min Jang
Keyword(s):  
Molecular Dynamics ◽  
Theoretical Analysis ◽  
Grain Boundary ◽  
Molecular Dynamics Simulations ◽  
Grain Boundaries ◽  
High Temperatures ◽  
Flat Surfaces ◽  
Roughening Transition ◽  
Entropy Effect ◽  
Dynamics Simulations

Flat surfaces and grain boundaries lying on low crystal planes are singular corresponding to the cusps in the polar (Wulff) plots of their energy against their orientation. The theoretical analysis of the entropy effect at high temperatures shows that these interfaces undergo roughening transitions. The molecular dynamics simulations also show disordering to liquid-like structures at high temperatures that can be interpreted as the roughening transition. Experimentally, singular flat surfaces and grain boundaries become curved at high temperatures or with additives, indicating their roughening transition. The grain boundaries in polycrystals are often faceted with hill-and-valley shapes and their defaceting at high temperatures also show their roughening transition.

Introducing Solute Drag in Irregular Cellular Automata Modeling of Grain Growth

2004 ◽  
Vol 467-470 ◽  
pp. 1045-1050 ◽  
Author(s):  
Koenraad G.F. Janssens ◽  
Elizabeth A. Holm ◽  
Stephen M. Foiles
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Growth ◽  
Boundary Energy ◽  
Solute Drag ◽  
Solute Concentration ◽  
Local Concentration ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Dynamics Simulations

In this paper we discuss the principles of a combined approach to solve the problem of solute drag as it occurs in microstructure evolution processes such as grain growth, recrystallization and phase transformation. A recently developed irregular grid cellular automaton is used to simulate normal grain growth, in which the energy of the grain boundaries is the driving force. A new, discrete diffusion model is used to simulate solute segregation to the grain boundaries. The local concentration of the solute is then taken into account in the calculation of the local grain boundary mobility and/or grain boundary energy, thereby constituting a drag force. The relation between solute concentration and grain boundary mobility/energy is derived from molecular dynamics simulations.

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