Tension-tension cyclic deformation of a [¯123]-[¯455] bi-crystal, with the stress axis parallel to the grain boundary, was performed under load control at room temperature. At lower stress amplitudes, in the early stages of fatigue, the dislocation configuration in both of the component crystals was characterized by an irregular cell-like structure. After 2 x 106 cycles at the same lower stress amplitude, the dislocation density in the ceilings or floors of irregular cell-like structures increased. These dislocations lined up in straight lines that corresponded to persistent slip lines on the surfaces of the 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 remained in the double-slip component, [¯455]. At a higher stress amplitude, the regular cell-like structure turned into a ladder-like structure in the single-slip component. The micro-cracks were approximately parallel to the grain boundary, and were 3 to 5μ from the grain boundary. They emerged preferentially into the single-slip component.

Micro-Crack Initiation and Dislocation Structures in an Aluminium Bi-Crystal Under Cyclic Loading S.Li, R.Chu, J.Hou, Z.Wang: Philosophical Magazine A, 1998, 77[4], 1081-92