austempered ductile iron is the most recent addition of the ductile iron family. It is produced by giving conventional ductile iron to austempering heat treatment. Unlike conventional as-cast irons, its property are achieved by heat treatment, not by specific addition. Therefore the only prerequisite for a good ADI is a quality ductile iron.
Austempered Ductile Iron (ADI) offers the best combination of low cost, design flexibility, good machinability, high strength-to-weight ratio and good toughness, wear resistance and fatigue strength properties. Because it can be cast like any other member of the Ductile Iron family it offers all the production advantages of a conventional Ductile Iron casting. Subsequently it is subjected to the austempering process to produce mechanical properties that are superior to conventional ductile iron, cast and forged aluminum and many cast and forged steels.
The mechanical properties of properties of the ductile iron and austempered ductile iron are primarily determined by the metal matrix. The matrix in conventional ductile iron is controlled by mixture of pearlite and ferrite. The properties of austempered ductile iron is due to its unique matrix of acicular ferrite and carbon stabilized austenite, is called ausferrite. The austempering process has been utilized since the 1930 on cast and wrought steels but this process first commercially applied to ductile iron in 1972.
Austempered Ductile Iron (ADI) Casting Research Development