Effect of Ag Addition to Zn22 mass%Al–2 mass%Cu Alloy on the Four-Phase Reaction η + ε → α + τ′

Abstract

The effect of Ag additions to the four-phase, η + ε → α + τ′, was studied experimental and thermodynamically using Zn–22 mass%Al–2 mass%Cu base alloys with four Ag contents from 0 to about 4 mass% Ag. SEM and XRD results indicated the presence of the τ′ phase decreased as the Ag content increased for the aged alloys which can be attributed to the stabilization of the ε phase because of its increase in Ag content which is in agreement with Thermo-Calc results. The Ag addition also promoted a slowest decrease in hardness in the aging curves at 200°C which can be attributed to the slowest diffusion process for the quaternary alloy.