HREM study and structure modeling of the η′ phase, the hardening precipitates in commercial Al-Zn-Mg alloys

The structure of the eta' phase, one of the most important age-hardening precipitates in commercial Al-Zn-Mg alloys, has been studied at the atomic level by means of high-resolution electron microscopy (HREM). A structural model of the eta' phase has been constructed on the basis of the structural characteristics in the observed images and the structure of the eta-MgZn2 phase. Image simulation of this model shows a good agreement between calculated and experimental images. Comparison of this model with the early existing model on the basis of the X-ray diffraction is also given. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.