Atomistically determined phase-field modeling of dislocation dissociation,stacking fault formation,dislocation slip,and reactions in fcc systems |
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| Institution: | 1. Material Mechanics, RWTH Aachen University, Schinkelstr. 2, 52062 Aachen, Germany;2. Microstructure Physics and Alloy Design, Max-Planck Institute for Iron Research, Max-Planck Str. 1, 40237 Düsseldorf, Germany;1. Unité Matériaux Et Transformations (UMET), UMR CNRS 8207, Université Lille 1, 59655 Villeneuve D’Ascq, France;2. EDF R&D MMC, Électricité de France, 77810 Moret-sur-Loing, France;1. Institute of Applied Mechanics, RWTH Aachen University, D-52074 Aachen, Germany;2. Material Mechanics, RWTH Aachen University, D-52062 Aachen, Germany;3. Microstructure Physics and Alloy Design, Max-Planck-Institut für Eisenforschung GmbH, D-40237 Düsseldorf, Germany;1. California NanoSystems Institute, University of California, Santa Barbara, Santa Barbara, CA 93106-6105, USA;2. GWW School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0405, USA;3. School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245, USA;4. Department of Mechanical Engineering, Materials Department, University of California, Santa Barbara, Santa Barbara, CA 93106, USA;1. Unité Matériaux Et Transformations, UMR CNRS 8207, Université Lille 1, F-59655 Villeneuve D''Ascq, France;2. Laboratoire commun EDF-CNRS Étude et Modélisation des Microstructures pour le Vieillissement des matériaux (EM2VM), France;1. State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha, Hunan Province, 410082, PR China;2. State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan Province, 410083, PR China;3. School of Engineering and Material Sciences, Queen Mary University of London, London, E1 4NS, UK;1. Purdue University, West Lafayette, IN 47907, USA;2. Los Alamos National Laboratory, Los Alamos, NM 87545, USA |
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| Abstract: | The purpose of the current work is the development of a phase field model for dislocation dissociation, slip and stacking fault formation in single crystals amenable to determination via atomistic or ab initio methods in the spirit of computational material design. The current approach is based in particular on periodic microelasticity (Wang and Jin, 2001, Bulatov and Cai, 2006, Wang and Li, 2010) to model the strongly non-local elastic interaction of dislocation lines via their (residual) strain fields. These strain fields depend in turn on phase fields which are used to parameterize the energy stored in dislocation lines and stacking faults. This energy storage is modeled here with the help of the ”interface” energy concept and model of Cahn and Hilliard (1958) (see also Allen and Cahn, 1979, Wang and Li, 2010). In particular, the “homogeneous” part of this energy is related to the “rigid” (i.e., purely translational) part of the displacement of atoms across the slip plane, while the “gradient” part accounts for energy storage in those regions near the slip plane where atomic displacements deviate from being rigid, e.g., in the dislocation core. Via the attendant global energy scaling, the interface energy model facilitates an atomistic determination of the entire phase field energy as an optimal approximation of the (exact) atomistic energy; no adjustable parameters remain. For simplicity, an interatomic potential and molecular statics are employed for this purpose here; alternatively, ab initio (i.e., DFT-based) methods can be used. To illustrate the current approach, it is applied to determine the phase field free energy for fcc aluminum and copper. The identified models are then applied to modeling of dislocation dissociation, stacking fault formation, glide and dislocation reactions in these materials. As well, the tensile loading of a dislocation loop is considered. In the process, the current thermodynamic picture is compared with the classical mechanical one as based on the Peach-Köhler force. |
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| Keywords: | Phase field Molecular statics Stacking fault Stacking fault energy Dislocation core Atomistically determined |
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