Flow stress anisotropy caused by geometrically necessary boundaries

The microstructural anisotropy of deformed metal is related to the formation of geometrically necessary boundaries such as dense dislocation walls and microbands. These boundaries have a macroscopic orientation with respect to the sample axes and they can resist slip due to a high concentration of dislocations. A model has been proposed for this microstructural anisotropy based on the assumptions that (i) the average slip plane is at an angle of 45-degrees to the direction of the applied stress and that (ii) a strengthening parameter is the mean distance in the slip plane between the geometrically necessary boundaries. For different macroscopic arrangements of such boundaries, the model predictions are in good qualitative and quantitative agreement with experiments.