Ductile iron is part of a group of materials that can have a wide range of properties through control of micro-structure. The common defining characteristic is graphite.
Ductile iron received its name due to the creation process. The graphite is nodule form rather than flake, like in grey iron. The sharp shape of the graphite flakes inhibit cracks and provide enhanced ductility, hence ductile iron.
While most varieties of cast iron are brittle, ductile iron has much more impact and fatigue resistance due to its nodular graphite inclusions.
Tiny amounts of magnesium added to cast iron slows down the growth of graphite precipitates by bonding to the edges of the graphite planes. It is strong and fracture resistant as well as being resistant to corrosion. Ductile iron is used to handle concentrated sulfuric acid as well as a variety of other, organic liquids.
High tensile strength, yield strength, and elongation are combined to give Ductile Iron a superior strength to weight ratio that adds up to more strength at less expense.
Ductile iron offers versatility and high performance and is used in many automotive components, where strength needs to surpass aluminum but does not require steel.