Austempered Ductile Iron Castings Properties
ADI is a group of materials whose mechanical properties can be varied over a wide range by a suitable choice of heat treatment. A high austempering temperature, 750F (400°C), produces ADI with high ductility, a yield strength in the range of 500 MPa with good fatigue and impact strength. These grades of ADI also respond well to a surface strain transformation which greatly increases their bending fatigue strength. A lower transformation temperature, 500F (260°C), results in ADI with very high yield strength (1400 MPa (200 MPa)), high hardness, excellent wear resistance and contact fatigue strength. This high strength ADI has lower fatigue strength as-austempered but it can be greatly improved with the proper rolling or grinding process. Thus, through relatively simple control of the austempering conditions, ADI can be given a range of properties unequaled by any other material. Small amounts of alloying elements such as nickel, copper and molybdenum are used to produce the desired heat treated result.