ADI have been used for a wide variety of application in automotive ,rail,and heavy engineering industry because of its excellent mechanical properties such as high strength with good ductility ,good wear resistance ,and good fatigue properties. The properties of austempered ductile iron are dependent on both chemistry and heat treatment, which has lead to invention of MADI (machinable austempered ductile iron). MADI is a new class of ductile iron with superior mechanical property than regular ductile iron with the same machinability characteristic. In this study Different cycle of austempering process ( austenitization and austempering cycle ) applied Due to the effect of heat treatment cycle on the metal matrix structure and mechanical properties of ductile iron and effect of heat treatment cycle on the mechanical properties of MADI was investigated.