HIGH-RESOLUTION ELECTRON-MICROSCOPY STUDY OF THE (10(1)OVER-BAR-2) TWIN AND DEFECTS ANALYSIS IN DEFORMED POLYCRYSTALLINE ALPHA-TITANIUM

A (<10(1)over bar 2>) twin boundary in deformed alpha-Ti has been obse rved by high-resolution electron microscopy. The observations are in a greement with a model calculated using a many-body potential. A twinni ng dislocation is predicted by the topological theory and characterize d directly in the experimental image with the circuit mapping method. It is shown that the core defect is spread along the twin plane as pre dicted by the atomistic model. Finally, the observation of a large ste p associated with a dislocation with Burgers vector b(10/9) points to the mechanism of matrix dislocation decomposition in the twin boundary .