THE STRUCTURE OF ALUMINUM-SILICON ALLOYS
NAVAL RESEARCH LAB WASHINGTON DC
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The microstructures and the morphologies of the phases of unmodified Al-Si alloys have been examined through the use of special etchants and a chemical extraction technique. X-ray diffraction studies have been used to confirm the metallographic observations. Although the dendritic form of the primary a phase was found to be unaltered by changes in the growth conditions, the form of the primary Si phase was not unaffected by these changes. The usual complex idiomorphic form of the Si phase was transformed to the dendritic form when growth occurred in a super-saturated liquid. Eutectic Si plates, which have been observed to grow from primary Si particles, dominate the eutectic transformation and, by branching, restrict the growth of the eutectic a phase. this mode of solidification produces fine eutectic colonies in this abnormal eutectic structure.
- Metallurgy and Metallography