Stacking defects in the 9R phase at an incoherent twin boundary in copper

Abstract

In situ HRTEM observations of the growth of 9R stacked material at a Σ=3 incoherent twin boundary in copper are presented. Stacking defects, which break the normal ABC BCA CAB… sequence of the 9R stacking, are observed in the growing 9R layer. These faults are shown to arise from the presence of secondary grain boundary dislocations with Burgers vectors of type a/6〈 211〉 . It is shown that both the sense (positive or negative) and character (90° or 30°) of the grain boundary dislocation determine the characteristics of the 9R fault.