Sliding at twin boundaries during high-temperature creep

Offsets due to grain boundary sliding have been observed at previously coherent annealing twin boundaries after high-temperature power-law creep of an austenitic stainless steel (Alloy 800). On average the magnitude of these offsets was 0middot;2-0middot;3 of that measured at 'general' grain boundaries. Sliding at twin boundaries contributed approximately 1middot;6% of the total strain during steady-state creep, while sliding at 'general' grain boundaries contributed 12-22%. Observations of dislocation structures in twin boundaries after creep suggest that twin boundary sliding is a direct result of the mobility of extrinsic boundary dislocations collected at these interfaces through interactions with matrix dislocations.