Editing Metal casting (section)

===Macrostructure===
The grain macrostructure in ingots and most castings have three distinct regions or zones: the chill zone, columnar zone, and equiaxed zone. The image below depicts these zones.

[[File:Cast ingot macrostructure.svg|class=skin-invert-image|500px]]

The chill zone is named so because it occurs at the walls of the mold where the wall ''chills'' the material. Here is where the nucleation phase of the solidification process takes place. As more heat is removed the grains grow towards the center of the casting. These are thin, long ''columns'' that are perpendicular to the casting surface, which are undesirable because they have [[anisotropic]] properties. Finally, in the center the equiaxed zone contains spherical, randomly oriented crystals. These are desirable because they have [[isotropic]] properties. The creation of this zone can be promoted by using a low pouring temperature, alloy inclusions, or [[wikt:inoculant|inoculants]].<ref name="degarmo282"/>