On the interaction between Ag-depleted zones surrounding γ plates and spinodal decomposition in an Al-22 at.% Ag alloy

Abstract

Decomposition of a supersaturated Al-22 at.% Ag alloy isothermally reacted at 350 °C in the α+γ two-phase field was investigated using various transmission electron microscopy techniques. The alloy was found to undergo both nucleation and growth of γ plates and spinodal decomposition. The interaction between the two mechanisms of phase decomposition caused an accumulation of Ag to develop in the matrix adjacent to the Ag-depleted zone surrounding the plates, which amplified with aging time. The matrix removed from the γ plates underwent three-dimensional, isotropic spinodal decomposition. A two-dimensional Cahn–Hilliard equation was used to model spinodal decomposition in the presence of the Ag-depleted zone adjacent to the γ plate faces. Agreement between the calculated and experimental composition profiles supports the view that the Ag-depleted zone adjacent to the plate faces catalyzes the development of a two-dimensional form of spinodal decomposition.