Materials Transactions Online

Materials Transactions, Vol.50 No.01 (2009) pp.2-10
© 2009 The Japan Institute of Metals

Effect of Extrinsic Grain Boundary Dislocations on Mechanical Properties of Ultrafine-Grained Metals by Molecular Dynamics Simulations

Tomotsugu Shimokawa1, Tomoyuki Hiramoto2, Toshiyasu Kinari1 and Sukenori Shintaku1

1Division of Innovative Technology and Science, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan
2Division of Mechanical Science and Engineering, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan

The effect of extrinsic grain boundary dislocations (EGBDs) in nonequilibrium grain boundaries on the mechanical properties of ultrafine-grained metals is investigated by molecular dynamics simulations. Aluminum bicrystal models containing cracks and EGBDs impinged from the crack tips are prepared. First, the dependence of the local grain boundary structure on the accommodation mechanism of EGBDs, and on its stress field is studied. Then, the shielding effect of EGBDs on the emissions of dislocations from crack tips is investigated, and the effect of nonequilibrium grain boundaries on the intragranular deformation is discussed. Finally, to investigate the relationship between EGBDs and intergranular deformations, shear loading is applied to the bicrystal models. It is found that extrinsic grain boundaries function as the intergranular deformation source, and the Burgers vector components of the EGBDs lead to anisotropic grain boundary sliding.

(Received 2008/7/15; Accepted 2008/8/29; Published 2008/10/22)

Keywords: extrinsic grain boundary dislocation, grain boundary sliding, grain boundary migration, nonequilibrium grain boundary, shielding effect, grain boundary structure, molecular dynamics

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