Precipitation sequence in a SiC/Al-Mg2Si alloy composite material

The precipitation sequence of an Al-1.0mass%Mg2Si composite material having 8 vol.% SiC particles was investigated by Vickers micro hardness and speci fic electrical resistivity measurements, and by TEM observation. The format ion of GP zones was suppressed in the composite material and its age-harden ability was reduced. Distribution of precipitates in the composite material was coarser and their size was larger than that in the Al-1.0mass%Mg2Si al loy (base alloy). Some types of precipitates in the composite material were not similar to those found in the base alloy but were similar to those in an Al-1.0mass%Mg2Si alloys with excess silicon (the excess Si alloy). Espec ially, the metastable phases in the composite material aged at 473 K belong ed to the type-A, type-B and type-C precipitates, which are typical metasta ble phases in the excess Si alloy, instead of the beta' phase that is a typ ical metastable phase in quasi-binary Al-Mg2Si alloys. The dislocations had little effect on the aging process of this composite material, because of the small number of dislocations introduced by the quenching after solution treatment. (C) 2001 Kluwer Academic Publishers.