Age-precipitation in Al2O3 particle/Al-Cu alloy and SiC particle/Al-Cu-Mg alloy composite materials.

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Abstract
In order to compare with the aging processes of alumina particle dispersed Al–Cu–Mg alloy composites which was revealed previously, those of alumina particle dispersed Al–4.0 mass%Cu alloy composites and SiC particle dispersed Al–4.1 mass%Cu–1.6 mass%Mg alloy composites were investigated by micro-vickers hardness test, electrical resistivity measurement and transmission electron microscope observation. When alumina particle sizes were differed from 1 to 15 μm at constant volume fraction as 5 vol%, both the GP zone and θ′ intermediate precipitates were appeared during aging. And the time requrired to make a maximum by aging was not changed with alumina particle size. But when the volume fraction of alumina particles increased, the time to reach maximum hardness by aging obviously decreased. Then the effects of alumina particle addition to Al–Cu alloy were the acceleration of aging process. At SiC particle dispersed composite materials, S' intermediate precipitates, rod-like θ′ intermediate precipitates and rectangular shaped σ phases coexisted at relatively later stage of aging. The time to reach maximum hardness by aging of the composites was retarded as compared with that of mother alloy. Then the effects of SiC particle adittion to Al–Cu–Mg alloy were the retardation of aging process.