EVIDENCE OF COOPERATIVE GRAIN-BOUNDARY SLIDING IN SUPERPLASTICALLY DEFORMED GAMMA-TIAL

A study of the prepolished surface of gamma-TiAl specimens superplasti cally deformed in tension showed evidence of macroscopic surfaces at w hich grain boundary sliding occurs. In a scanning electron microscope these surfaces are observed as black bands on the deformed surface bec ause of the difference in the appearance of these bands and grain regi ons situated in between these bands. It has been suggested that cooper ative grain boundary sliding, i.e., sliding of grain groups, occurs du ring superplastic deformation, giving rise to these bands.