Abstract
The occurrence of grain boundary precipitates was investigated with respect to the crystallographic orientation of the adjacent grains in extruded AA6110, AA6063 and AA6061 alloys brought to T6 temper. It was found that the requirement for grain boundary precipitate formation is for the adjacent grains to have <100>Al directions or {100}Al planes parallel to the grain boundary plane. The highest density of grain boundary precipitates was present when this requirement was fulfilled by both adjacent grains.