Extended Dislocation Nodes in a Silver-Tin Alloy

Publisher Website
Google Scholar
Abstract
A study of dislocation nodes formed in silver-tin solid solution alloys has been conducted using transmission electron microscopy. In alloys of 6 and 8 at.% Sn, both extrinsic and intrinsic stacking faults were observed at threefold dislocation nodes. Burgers' vector data obtained from diffraction contrast studies were in agreement with predictions based on geometric considerations. From a qualitative comparison of the node extensions, the extrinsic fault energy appears to be greater than the intrinsic fault energy. Both fault energies were observed to decrease with increasing solute concentration. At many of the nodes containing extrinsic faults, the partial dislocations were bowed outward; at the intrinsically faulted nodes, inward curvatures were always observed. It is believed that the dislocation constrictions or cross-linking dislocations required at the extrinsically faulted nodes were responsible for this difference. Motion under stress of the extrinsically faulted nodes was observed, consistent with the coplanar Burgers' vector geomtery. The observations lead us to suggest the general occurrence of both types of faults in low stacking-fault energy fcc materials.