Austempered spheroidal graphite iron (ADI)

Austempered ductile iron is obtained by subjecting castings of alloyed spheroidal graphite iron to an austempering cycle — austenitization followed by isothermal quenching in a salt bath — which produces an ausferritic matrix with mechanical properties comparable to quenched and tempered steels. ADI combines high static and fatigue strength, fracture toughness, wear resistance, and a density roughly 10% lower than steel, making it competitive in gearboxes, gears, automotive, rail, and earthmoving applications.