Shinji Ando, Takushi Goto, Kazuki Takashima and Hideki Tonda
* Department of Mechanical Engineering and Materials Science, Faculty of Engineering, Kumamoto University, Kumamoto 860-8555 ** Graduate School of Science and Technology, Kumamoto University, Kumamoto 860-8555 *** Precision and Intelligence Laboratory, Tokyo Institute of Technology, Yokohama 226-8503The core structures of (c+a) dislocations in HCP metals have been investigated by molecular dynamics simulation using a Lennard-Jones type pair potential. The edge dislocation has two types of stable core structures at 0 K; one is a perfect dislocation (Type-A) and the other is two 1/2(c+a) partial dislocations (Type-B). While the Type-B core is stable at 30 K and 293 K, the Type-A core extends parallel to the basal plane at 30 K. The Type-A core at 0 K transforms to the Type-B core by increasing temperature from 0 K to 293 K. In contrast, the extended Type-A core at 30 K is still stable at 293 K. These results suggest that the (c+a) edge dislocation glides on the {1122} plane as two 1/2(c+a) partial dislocations and becomes sessile due to changes of the core structure. The screw dislocation exhibits a stable core spread over two {1011} type planes at 0 K. The core transforms to unsymmetrical structure at 293 K, which is spread over {1122} and {1011}, and to a core spread parallel to {1122} at 1000 K. The dependence of the yield stress on the shear direction can be explained from these core structures of screw dislocation.
hcp metal, non-basal slip, edge dislocation, screw dislocation, core structure, molecular dynamics, computer simulation