Abstract
Tension—tension cyclic deformation of a [123]—[455] aluminium bicrystal with the stress axis parallel to the grain boundary (GB) was performed under load control at room temperature. At a lower stress amplitude, in the early stage of fatigue the dislocation configuration in both component crystals was characterized by an irregular cell-like structure. After 2 × 106 cycles, at the same lower stress amplitude, the dislocation density in some ceilings or floors of irregular cell-like structure increased, and these dislocations lined up in straight lines that corresponded to the persistent slip lines on the surfaces of the two component crystals. At an intermediate stress amplitude the irregular cell-like structure changed to a regular cell-like structure in the single-slip component [123], while the irregular cell-like structure still remained in the double-slip component [455]. At a higher stress amplitude the regular cell-like structure turned to a ladder-like structure in the single slip component. The microcracks were approximately parallel to the GB, and they were 3–5 μ apart from the GB and emerged preferentially in the single slip component. A possible mechanism of microcrack initiation by voiding was suggested.