W. Wang et al., SI PHASE NUCLEATION ON SIC PARTICULATE REINFORCEMENT IN HYPEREUTECTICAL-SI ALLOY MATRIX, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 187(1), 1994, pp. 65-75
The solidification process of a hypereutectic Al-17wt.%Si-0.31wt.%Mg a
lloy with 15 wt.%SiC particles was investigated by quenching samples t
hrough the solidification region and by conventional casting of sample
s from the mechanically stirred composite melts. The nucleation and gr
owth processes of the primary Si phase under both stirred and unstirre
d conditions were examined, and the Si/SiC(p) interface was analysed b
y SEM and EDX with X-ray image analysis. The Si phase of Al-Si alloys
has a more important role than the alpha phase in the bonding of the S
iC reinforcement with the matrix, because the Si phase nucleates prefe
rentially on the SiC particles even when the spinel interfacial layer
exists. The crystal structures of the phases in the composites were id
entified by X-ray diffraction, and the factors which influence the het
erogeneous nucleation of Si crystal on the substrates are discussed.