THE STRUCTURE OF ASYMMETRICAL TILT BOUNDARIES FORMED DURING CREEP OF [112] ORIENTED ALUMINUM SINGLE CRYSTALS

Abstract

The structure of {110} tilt boundaries formed during creep at 400° C of [112] oriented aluminum single crystals has been studied using high resolution and weak beam electron microscopy. The dislocation content is described as a function of the plane of the boundaries and the tilt misorientation. The arrangement of the atomic columns indicates that higher angle boundaries are composed predominantly of Lomer dislocations aligned in orderly, low energy tilt configurations. The boundary plane is faceted by the presence of 60° dislocations. In contrast, lower angle boundaries tend to be less periodic and have a higher density of 60° than Lomer dislocations. The Burgers vectors of the 60° dislocations have been determined using weak beam observations and the magnitude of the twist misorientation of the boundaries agrees well with the dislocations present. The relevance of these observations with respect to glide on non-compact planes, subgrain boundary formation during creep and dislocation core observations in aluminum is also discussed