SOLIDIFICATION OF THE ALUMINUM-SILICON EUTECTIC
NAVAL RESEARCH LAB WASHINGTON DC
Pagination or Media Count:
The eutectic solidification process in aluminum-silicon alloys has been examined through a metallographic study of slowly cooled and quenched specimens. The use of suitable etchants to delineate the structures of the Si and a phases and the examination of extracted particles of Si have shown that the abnormal Al-Si eutectic structure is the result of the great disparity in the nucleation and growth characteristics of the two phases. the eutectic Si not only nucleates readily, but it grows rapidly into a branched-plate structure. The nucleation of the a phase, requiring a high supersaturation, is retarded and, as a consequence, this phase exerts very little control in the solidification process. Thermal data, showing the relative effectiveness of the two primary phases in limiting the undercooling preceding the eutectic, support these observations.
- Metallurgy and Metallography