The aging characteristics of an Al–Ag alloy processed by equal-channel angular pressing

An Al–10.8 wt.% Ag alloy was processed by equal-channel angular pressing (ECAP) and aged at temperatures of 373 or 473 K. Hardness measurements were taken after different aging times and the results show the hardness continuously decreases when aging at 473 K but increases to a peak hardness when aging at 373 K. For aging at 473 K, it is shown that metastable γ′-phase particles form within the grains and stable γ-phase particles form throughout the sample but these particles make no contribution to the hardness. By contrast, aging at 373 K leads to the formation of stable γ-phase particles on the grain boundaries and a fine dispersion of η-zones and plate-like γ′-phase particles within the grains: the increase in hardness is attributed to these finely-dispersed particles. Aging at 373 K for 100 h, corresponding to peak aging, gives an increase in the uniform elongation in tensile testing and the same high level of stress as in samples after ECAP processing.