 The mold cooling effect creates an advancing solidification front, which has several associated zones, closer to the wall there is a solid zone which draws heat from the solidifying melt, for alloys there may exist a "mushy" zone, which is the result of solid-liquid equilibrium regions in the alloy's phase diagram, and a liquid region.The rate of front advancement controls the time that dendrites or nuclei have to form in the solidification region.The width of the mushy zone in an alloy may be controlled by tuning the heat transfer properties of the mold, or adjusting the liquid melt alloy compositions.