Intrinsic and extrinsic nodes in a gold-tin alloy

Abstract

Dislocation nodes in a gold-tin alloy (4·8 at. % Sn) have been examined by transmission electron microscopy. It has been found that the ratio of the radius, R, to width, W, of intrinsic nodes varies between the values R/W ≃ 5 and R/W ≃ 3 for screw and edge nodes respectively. These values are consistent with the theoretical values obtained by Brown (1964). In addition to this systematic variation, there is a large scatter in R and W due to factors unconnected with the character of the node. Thus R and W each vary by a factor of approximately two for screw nodes, although the ratio R/W remains approximately constant. Nodes with straight edges have been observed and identified as extrinsic nodes. A wide variation of size is found in these extrinsic nodes.