Formation of quasicrystalline particles in an isothermally aged Al-10 Mg-0.5 Ag (mass%) alloy

Abstract

The trace additions of Ag to binary Al-Mg alloys promote precipitation of a phase in the under-aged condition. The structures of the phase in an Al-10 Mg-0.5 Ag (mass%) alloy have been characterised using transmission electron microscopy and electron microdiffraction. An icosahedral quasicrystalline phase, which is identified by the electron microdiffraction patterns, has been found in the Al-10 Mg-0.5 Ag (mass%) alloy after solution treatment, water quenched and then aged during the time between 20 and 40 min. at 240°C. The orientation relationship between the quasicrystalline phase and the α-Al matrix is as follows; 15 // 〈011〉α and 13 // 〈111〉α. A uniform distribution of finer-scale (typically 20 nm), faceted precipitate particles was observed within the core of the grains, but the precipitates became coarser (60-80 nm) approaching the grain boundary precipitate-free zone. © 2005 The Japan Institute of Metals.