LOCKING OF 1 OVER-BAR(1)OVER-BAR26-GREATER-THAN(11(2)OVER-BAR1) SUPERPARTIALS IN TI3AL AT HIGH-TEMPERATURES/

The <(1) over bar (1) over bar 26>{11 (2) over bar 1} pyramidal slip i n Ti3Al shows the so-called yield stress anomaly. Near the peak-stress temperature, specimens collapse by shearing on {11 (2) over bar 1} sl ip plane almost immediately after yielding. Transmission electron micr oscope study revealed that pairs of unlike 1/6<(1) over bar (1) over b ar 26>{11 (2) over bar 1} superpartial dislocations coupled by antipha se boundaries were generated in the same temperature range. These supe rpartials are of edge in character and are shown further to climb-diss ociate on the basal plane into partials of smaller Burgers vector boun ding a complex stacking fault: the dissociation is described by an equ ation 1/6<(1) over bar (1) over bar 26> --> 1/6<(1) over bar 013> +1/6 <0 (1) over bar 13>. Fracture of single crystals at high temperatures is associated with locking of 1/6<(1) over bar (1) over bar 26> superp artials by climb dissociation.