Abstract:
The movement of a dislocation in interaction with an interface, in the absence of external
stresses, is controlled by the balance of internal stresses. This assessment includes the friction force in the Peierls-Nabarro network stress and a force due to the anisotropy of the material called image force. We study the mobility of the perfect dislocation 1/3 <11-20> in the (0001) basal and prismatic (10-10) slip planes of the hexagonal structure. The dislocations are located in crystal (1) of a bicrystal among Zn, Be, Co, Hf, Ti, Zr, Cd, Y, Mg and Tl which are elastically anisotrope metals. They are parallel to the interface plane and are in elastic interaction with this interface and situated at a distance d therefrom. Each dislocation is characterized by its line direction and Burgers vector b. The interface is defined by its plane which is basal one for the two crystals and a null disorientation. The setting of the dislocation movement under the effect of the image force depends on the intensity of the elastic energy interaction of dislocation with interphase boundary and of the distance d where the dislocation is located.
The setting in motion is effective if the intensity of the image force (Fi = - E / d, E is the elastic interaction energy) is greater than the Peierls constraint. The dislocation is attracted or repelled upon the direction of image force. A critical distance, dc, is defined when image force is equal to the Peierls force. The dislocation is attracted to the interface when the crystal (2) is softer than the crystal (1), it is repelled when the crystal (2) is the hardest. The efficiency distance of image force increases with the absolute value of the difference in shear modulus of the materials constituting the bicrystal.
The favored slip plane is selected by the c/a ratio of the crystal which is located dislocation.
The result is in accordance with those of the behavior of dislocations in single crystals except for the cases crystals of the c/a ratio close to (8/3) (Mg and Co).
