THE STRUCTURES OF FULLY EUTECTIC ALUMINUM SILICON ALLOY CASTINGS

Strontium-modified aluminium alloys containing 14 to 15 wt% silicon were cast with fully eutectic structures by using heated moulds and high-purity materials. In alloys containing the additional elements magnesium, copper or nickel, a distinct eutectic colony structure was evident outlined by intermetallic compounds. At the edges of the castings the eutectic colony structures and the aluminium grains (revealed by anodizing) were of a similar scale. Further from the mould walls the eutectic colonies contained several aluminium grains. This is believed to result from the blocking of growth of the aluminium phase by the silicon phase. © 1990 Chapman and Hall Ltd.