Grain boundary dislocations and the mechanism of sliding in symmetrical [011] tilt Al bicrystals

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Abstract
SUMMARY: Observations of grain boundary dislocations in [011] tilt bicrystals of aluminium after high temperature shear tests have led to a concept for grain boundary sliding that involves extrinsic dislocations moving through an array of structural dislocations. Each extrinsic dislocation consists of a group of structural dislocations with closer than normal network spacing caused by the presence of an extra dislocation with the same Burgers vector. The extrinsic dislocation exhibits a long range strain field and can move individually through the array of structural dislocations. The movement involves displacements in the structural network analogous to atom displacements during crystal slip. The width of the extrinsic dislocation on the grain boundary plane is dependent on the degree of accommodation of the extra dislocation by the structural array and this appears to increase with increasing density of structural dislocations.