Loop patch orientations in the matrix structure of cyclically deformed copper

Abstract

A detailed analysis was performed of two regions of matrix or loop patch structure of cyclically deformed copper, each containing a single orientation of persistent slip bands (PSBs). Each loop patch orientation identified agreed with a wall geometrically predicted from a dipole-loop-stacking model for the occurrence of primary slip in combination with a slip system involving a secondary Burgers vector. The wall orientations identified were mechanistically favoured, based on dislocation-sweeping angle considerations, and also were those best able to accommodate excess primary slip dipole loops. The occurrence of {135} walls emphasized the importance of mechanistic considerations in determining wall orientations. The loop patch orientations identified generally contained 〈112〉 parallel to the primary edge dislocations, permitting a high percentage of walls and loop patches to coincide at PSB interfaces. The same geometrical condition enables us to understand wall rotations within PSBs. Additional evidence was obtained related to the influence of dislocation-sweeping angles on wall spacing and on dipolar structures in the immediate vicinity of twin boundaries.