It was pointed out that, although grain boundary sliding contributed largely to superplastic deformation, few studies had been made of the grain boundary sliding behavior at individual boundaries in superplastic materials. An investigation was made here of the effect of grain boundary characteristics such as the angle between the tensile direction and the grain boundary at the specimen surface, the natures of the adjacent grains across a grain boundary, and the -value for the misorientation of adjacent grains across a grain boundary. It was noted that superplastic behavior occurred when grain boundary sliding took place at most of the grain boundaries. It was concluded that such sliding was easier at a grain boundary when there was a large angle between the grain boundary and the tensile direction. Also, sliding was expected to be more difficult at grain boundaries with rather low -values, than at random grain boundaries. Finally, in the case of random grain boundaries, grain boundary sliding was expected to be easier at a boundary with a higher angle.

N.Furushiro, T.Haruna, T.Shibayanagi, U.Umakoshi, S.Hori: Materials Science Forum, 1997, 243-245, 109-14