Identification of β Phase Particles in an Isothermally Aged Al–10 mass%Mg–0.5 mass%Ag Alloy

Abstract

The structure and morphology of coarse-scale globular and smaller spheroidal particles in an isothermally aged Al–10Mg–0.5Ag (mass%) alloy have been charcterised by means of transmission electron microscopy. Coarse-scale globular and smaller spheroidal particles were commonly observed in an over-aged sample aged for 72 h at 240°C. The coarse-scale globular and smaller spheroidal particles were identified by electron microdiffraction to have the face-centered cubic structure of equilibrium β phase (Al₃Mg₂) (lattice parameter a=2.824 nm). The orientation relationship between the β phase and α-Al matrix was such that: (100)_β||(100)_α and [001]_β||[001]_α. This orientation relationship differs from those reported previously for the β phase formed in binary Al–Mg alloys. The coarse-scale globular β particles had invariably internal faulted structures.