Most alloys behave in a consistent and predictable manner on cooling from pouring through to the solidus temperature. Two separate phases of shrinkage occur Firstly, as the alloy cools from the pouring temperature to the liquidus, this is commonly termed liquid or superheat shrinkage. Secondly, as the alloy cools from the liquidus to the solidus point, which is generally referred to as solidification shrinkage. On the other hand, the cooling and solidification of graphitic iron castings, which includes grey, ductile and malleable iron alloys, is accompanied by an unusual phenomenon, the metal starts to expand. This expansion is generally attributed to the precipitation of the less dense graphite phase overcoming and exceeding the contraction associated with cooling liquid and the solidification of austenite.
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