Secondary defects in quenched and aged platinum

Abstract

Some results of a study of secondary defects in quenched platinum are presented. Transmission electron microscopy (TEM), used with field-ion microscopy (FIM), yielded direct evidence for the existence of prismatic loops, Frank loops, and polyhedral voids. The Frank loops were observed as black spots in the electron microscope and were resolvable only via FIM. The loop density was estimated to be 1013 per cu cm from TEM with an average size of approximately 50A. Resolvable loops were found among networks of heavily jogged dislocations. The void concentration reached a maximum of 7 × 1014 per cu cm after annealing at 400°C for 24 hr and fell sharply on either side of this temperature. In general the voids could be described as regular octahedra, some truncated by {100} and occasionally by {111} planes. Small voids appear spherical due to strain contrast but careful tilting experiments reveal hexagonal cross sections implying {100} truncated octahedra. Small tetrahedral clusters have been observed via FIM and these may be the nuclei for both voids and dislocation loops. Larger voids are shown to be extremely stable almost to the melting point.