Solvus line of the metastable rhombohedral phase in the Al-Zn system for Al-rich alloys

Abstract

The X-ray diffraction on single crystals and on coarse-grained foils of Al-Zn alloys was used to determine the solvus temperatures of the metastable rhombohedral α′R-phase. The dissolution of α′R-phase was studied simultaneously by application of DTA technique. Results obtained from different heat-treatments of the investigated alloys were critically interpreted in terms of the nucleation theory. The dissolution of large α′R-particles was necessary to obtain the correct α′R-solvus line unaffected by the reversion of the solid solution below the solvus temperatures.