A (10•2) twin boundary in deformed -phase material was studied by means of high-resolution electron microscopy. Various twin dislocations were characterized, and it was revealed that the decomposition of matrix dislocations took place. It was found that the observations were in agreement with predictions which had been made by using a many-body potential. The existence of a twinning dislocation was predicted by topological theory, and was identified directly in experimental images by using the circuit-mapping method. It was shown that the core defect was spread along the twin plane, as predicted by an atomistic model. A large step was observed which was associated with a dislocation with a Burgers vector of b10/9. It exhibited a compact core with a step riser that was close to (10•0) and (00•1). This indicated the occurrence of matrix dislocation decomposition in the twin boundary. The present results differed from those which had been obtained for Zn; in which the twinning dislocation had a localized core.

T.Braisaz, P.Ruterana, G.Nouet, A.Serra, P.Komninou, T.Kehagias, T.Karakostas: Philosophical Magazine Letters, 1996, 74[5], 331-8