A type of iron in which the graphite content takes spherical rather than flake form. Ductile iron is produced by adding magnesium. The spherical form of the graphite provides greater tensile strengths and flexibility than other types of iron. An iron/graphite composite in which the graphite exists in spheres or nodules, allowing the material to deform rather than fracture when placed under mechanical stress. Also called Nodular Iron. Iron in which carbon is in the form of spherical nodules. See Nodular Iron.
Ductile iron, also called ductile cast iron or nodular cast iron, is a type of cast iron invented in 1942 by Keith Millishttp://www.moderncasting.com/archive/feature_023_01.html. While most varieties of cast iron are brittle, ductile iron is much more ductile, as the name implies.