Cyclic deformation behavior and dislocation structures of [001] copper single crystals--II. Characteristics of dislocation structures
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文摘
The dislocation structure of [001] Cu single crystals developed in cyclic deformation has been systematically studied with transmission electron microscopy and related to the mechanical behavior presented previously. The dislocation configuration for this orientation is characterized by labyrinth structures over all the strain amplitudes investigated. At high strain amplitudes (γpl = 1.8 × 10−3-3.0 × 10−3), additional structures such as exclusive walls and strips were observed. The strips are parallel to {111} slip planes and are associated with macro-deformation bands reported previously. At low strain amplitudes (γpl ≤ 2.4 × 10−4), however, labyrinth becomes irregular in geometrical shape. Labyrinth structures consist of two types of perpendicular walls: one is always parallel to (001) plane and the other may be (100), (210) or (120). The characteristic dimension of labyrinths, such as channel width, increases with decreasing applied strain amplitude. The nature of dislocations in labyrinth structures was identified to be mainly primary and critical dislocations. The role of labyrinth structures in cyclic deformation was discussed in terms of geometrical considerations. It has been shown that labyrinth structures are more favorable to cyclic deformation by promoting multiple slip and cross slip. Finally, the cyclic saturation stress was quantitatively correlated with the microparameter of labyrinth structures.