On the nature and distribution of defects in tungsten lamp wire

A combined electron microscope-field ion microscope study of the early stages of bubble development in the as drawn material is reported. Some atom probe analyses of these defect regions, and of grain boundaries, are also being carried out, and are reported in more detail in a subsequent publication. A previous exploratory field-ion microscope investigation of this material by Meyrick shows strings of defects which were thought to be particles. The image contrast observed from the defects was quite different from that given by second-phase particles in other systems, however, and was not interpreted in detail. It is demonstrated that these complex image features are consistent with voids or bubbles intersecting the specimen surface, and that they are associated with severe ion optical distortions of the field ion image, caused by the local surface irregularity. (Auth.)