Small Stacking Fault Tetrahedra Observed in High Purity Gold Shortly after Quenching

Abstract

Small stacking fault tetrahedra (SFT) which just nucleated by clustering of vacancies inquenched high purity gold were observed at -160°C after specimen thinning by electron microscopy. It was found that even in a thin foil SFT grew appreciably and new SFT nucleated duringa room temperature annealing, while only SFT which were observed on the first cooling stage observation could grow during the subsequent 200°C thin foil annealing. The minimum edge size of tetrahedron image observed shortly after quenching was about 20 Å. For the nucleus of SFT which is the smallest vacancy cluster stable below 400°C as previously found expermentally, the present results suggest that they are the smallest SFT whose size is less than 20 Å. Growth of SFT in thin foil was explained with an almost perfect sink efficiency of SFT for the vacancy absorption below room temperature.