CONCERNING THE DISSOCIATION OF GROWN-IN DISLOCATIONS IN MELT SPUN RIBBONS OF THE INTERMETALLIC COMPOUND NB3AL

The nature of 'grown-in' dislocations formed in melt spun ribbons of the compound Nb3Al have been studied using transmission electron microscopy. These dislocations have b = <100> and are predominantly screw in character. They are dissociated into two partial dislocations which bound a complex stacking fault according to the reaction <100> --> 1/2 <100> + CSF + 1/2 <100>. The habit plane of the fault is shown to be {012}. These observations are compared with previous studies performed on the isostructural compound V3Si and the consequences of the observed dissociation for the plastic deformation of A15 compounds are discussed.