MICROSTRUCTURAL ASPECTS OF NONHOMOGENEITY OF GRAIN-BOUNDARY SLIDING

Direct observation in the scanning electron microscope of grain-bounda ry sliding (GBS) in Pb-62%Sn eutectic alloy, superplastically deformed in shear, showed non-uniformity of GBS. Such non-homogeneity of GBS r eveals itself as sliding of large grain blocks with dimensions of tens of grain size and sliding of grain groups with dimensions of a few (f our to eight) grain size. Sliding of large blocks of grains is a resul t of the sliding of grains as an entity along grain boundaries of form er dendritic boundaries. The sliding of grain groups is due to the coo perative manner of GBS. Experimentally observed size of the grain grou ps can be explained from the view point of cooperative GBS, caused by glide of cellular dislocations.