Effect of Grain Boundary Characters on Grain Boundary Sliding during Superplastic Deformation

Abstract

It is well known that grain boundary sliding (GBS) mainly contributes to superplastic deformation. However, since there are few studies on GBS behavior at each grain boundary during superplastic deformation by using polycrystal material, the contribution of three grain boundary characters to GBS at each grain boundary during superplastic deformation has been investigated. Three characters were adopted as the following; the angle between grain boundary at the specimen surface and tensile direction, the kind of adjacent grains across a grain boundary, and Σ value which was calculated from orientations of adjacent grains across a grain boundary. The examination was carried out by tensile test in SEM with Pb–Sn eutectic alloy at room temperature. The results obtained are summarized as follows:(1) The superplastic behavior was confirmed to occur when GBS was observed at most of grain boundaries.(2) It is considered that GBS is easier at a grain boundary both with the higher angle between grain boundary and tensile direction, and with the same kind of adjacent grains across a grain boundary.(3) So far as Pb–Pb boundary is concerned, GBS was more difficult to occur at grain boundary with rather low Σ value than at random grain boundary. Moreover, for random grain boundary, GBS was easier to occur at a grain boundary with higher angle of grain boundary.