Aging process of TiC particle dispersed Al-Cu and Al-Cu-Mg composite materials

Aging processes of TiC particle dispersed Al-4.0 mass%Cu, Al-4.3 mass%Cu-1.1 mass%Mg and Al-4.3 mass%Cu-1.8 mass%Mg alloys were investigated by micro-Vickers hardness, electric resistivity measurement and transmission electron microscope observation. When TiC particles are dispersed into an Al-4.0 mass%Cu alloy at a constant volume fraction of 4 vol%, aging time to reach a maximum hardness is shortened at 423 K aging. On the contrary, at 473 K aging, the time is more prolonged than that in the mother alloy. Coarsened θ′ phase precipitates on the dislocations are observed at the early stage of aging in the composite materials. At a peak aging condition, GP zones and almost identical size and density of the ff precipitates are distributed in the both mother alloy and composite materials. Aging curves of the small amount Ti added alloy show almost a similar tendency as those of the composite materials. When Al-Cu-Mg alloys having compositions in which GPB zones and the S′ intermediate phase are formed during aging are used as the mother alloy, the composite materials produce the same types as the mother alloy. In this case, both the Ti added alloy and composite materials also give the almost equal time to reach a maximum hardness at 473 K aging.