An explanation of labyrinth walls in fatigued f.c.c. metals

Abstract

The occurrence of labyrinth dipolar walls in fatigued f.c.c. metals is explained as resulting from double pseudo-polygonization (DPP) arrangements of dipole loops essentially edge in character. From the orientations of the edge dislocations of two Burgers vectors on any two slip systems, a three-dimensional regular stacking network of dipole loops can be constructed from which a dipolar wall is obtained by restricting stacking in one of two directions, since the third possible stacking direction appears to be mechanistically favoured. The experimentally demonstrated {100} and {210} walls are shown to be obtained from the same dipole networks. Some experimental evidence also exists suggesting the presence of geometrically predicted {110}, {111} and {211} and/or {311} DPP walls. The present model for f.c.c. metals explains the main aspects of the existing experimental evidence on the orientations of labyrinth walls and also appears to explain that on walls produced at intersections of persistent slip bands. Apparent rotations of simple polygonization {100} walls and the occasional presence of dipolar walls along persistent slip band interfaces can also be rationalized by this model.