DETERMINING DIRECTLY FROM EXPERIMENT THE MAGNITUDE OF THE BURGERS VECTOR OF GLISSILE [C]-COMPONENT DISLOCATIONS IN TI3AL

The magnitude of the Burgers vector of glissile [c]-component dislocat ions observed in polycrystalline alpha(2)-Ti3Al after room-temperature compression has been determined directly and unambiguously using tran smission electron microscopy. Previously only the direction of the Bur gers vector of these types of defects has been determined unequivocall y from experiment alone. The direct experimental determination of the Burgers vector has been achieved by combining conventional diffraction contrast experiments with a detailed analysis of the effects of these [c]-component dislocations on thickness contours. Thus the defects re sponsible for the limited accommodation of strains with components out of the basal plane, c-component strains, during room-temperature defo rmation have been identified to be pairs of [c+a/2] superpartial dislo cations with Burgers vectors b = 1/6[(2) over bar 116] delineating a r ibbon of antiphase boundary on second-order pyramidal planes, {(2) ove r bar 11 (1) over bar}.