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Tsuru, Tomohito; Shibutani, Yoji*; Hirouchi, Tomoyuki*
AIP Advances (Internet), 6(1), p.015004_1 - 015004_9, 2016/01
Times Cited Count：11 Percentile：44(Nanoscience & Nanotechnology)The material strengths of polycrystalline metals have been widely predicted according to the grain size, where yield stress is governed by slip transfer through the grain boundary (GB). The transferability of a dislocation across a GB is enormously important in the deformation process as well as the interaction between a dislocation and GB. This paper proposes a new criterion for the transferability of dislocations through a GB that considers both the intergranular crystallographic orientation of slip systems and the applied stress condition. Atomistic simulations were carried out to investigate the slip transfer event of simple bicrystals composed of 
GB than 
GBs under uniaxial deformation and to illustrate the availability of this criterion. As a result, in contrast to the predictions of conventional criteria such as the 
-value, dislocations propagated more easily across the and GB under given stress states, reflecting a larger 
-value of 
bicrystal associated with higher transferability.
3 tilt grain boundaries under uniaxial compressionShibutani, Yoji*; Hirouchi, Tomoyuki*; Tsuru, Tomohito
Journal of Solid Mechanics and Materials Engineering (Internet), 7(6), p.571 - 584, 2013/06
Microscopic yielding can be realized by the transfer of a dislocation across a grain boundary (GB), or by incorporation between the residual GB dislocation and the dislocations nucleated in the near-field of a GB due to the applied stress. In the present paper, a new boundary interaction criterion of 
- or '-value is proposed, which considers both the contributions of the geometric relationship between two grains and a GB, and the stress state applied to the near-field of a GB. This value and the others so far proposed were calculated for 
110
, 100, and 111 symmetric tilt grain boundaries under uniaxial compression normal to the GB. The dynamic transfer and incorporation of the dislocations nucleated under uniaxial compression normal to the GB plane were then examined using 3-dimensional molecular dynamics simulations.
tilt grain boundary using multi-phase-field model with penalty for multiple junctionsHirouchi, Tomoyuki*; Tsuru, Tomohito; Shibutani, Yoji*
Computational Materials Science, 53(1), p.474 - 482, 2012/02
Times Cited Count：23 Percentile：56.95(Materials Science, Multidisciplinary)Multi-phase-field (MPF) model with a higher-order term representing energetic penalty for multiple junctions was proposed to predict the grain growth accompanying the inclination dependence of grain boundary (GB) energy and mobility. The inclination effect was introduced on the basis of GB energy obtained from molecular dynamics simulations. The preliminary grain growth simulation of an isolated grain surrounded by GB certified that the analytical equilibrium shape was well reproduced. The augmented higher-order term added to conventional MPF model could improve convergence and stability of numerical calculations around triple junction (TJ) region even if there exists the large GB energy gap at the TJ. For the polycrystalline grain growth simulations with the GB energy distribution according to the misorientation angle of Al tilt GB, GB inclination lead the weak anisotropy characterized by 
twin boundary.
Hirouchi, Tomoyuki*; Tsuru, Tomohito; Shibutani, Yoji*
Nihon Kikai Gakkai Rombunshu, A, 77(782), p.1723 - 1734, 2011/10
Multi-phase-field (MPF) modeling with a higher-order term, which can stably analyze the triple junction (TJ) behaviors even with large difference between grain boundary (GB) energies, is proposed for the more realistic grain growth prediction. Grain growth simulations of systems including multiple junctions show that the proposed MPF model can represent the stable TJ behaviors with wider range of GB energies than the conventional model, and well perform the quadruple junction behaviors in agreement with the responding theory. Two kinds of GB energy distribution models are employed here, which are based on all of and only low cuspate energies of 1 1 0 symmetric tilt GB energy in pure Al by molecular dynamics simulations. Polycrystalline grain growth simulations combining with either GB energy distribution exhibited the large amount of nucleation of low-energy boundaries, which would be quantitatively compatible to the experiments.
