Effect of Heat Treatment Parameters and Alloying Elements on Microstructure of Austempered Ductile Iron – A Review | Original Article
The most rapidly growing area of cast technology is that of Austempered Ductile Iron (ADI). This paper reviews the effect of alloying elements and heat treatment parameters on microstructure of Austempered Ductile Iron. ADI is a heat treated Ductile Iron or S.G. iron with a unique micro-structure: Ausferrite which consists of high carbon Austenite and Bainitic ferrite with graphite nodules dispersed in it. This is one of the unique microstructures having excellent properties: high strength, toughness, good wear resistance, good machinability and all that at low cost. The use of this type of cast iron as an engineering material has been increasing day by day since its discovery. These properties can be achieved upon adequate heat treatment which yields optimum microstructure for a given chemical composition. But this type of treatment is bit tricky, since it requires controlled heating and isothermal holding of the material. In this work an investigation has been conducted on ductile iron with and without Copper additions and austempered in a range of time and temperature. The influence of conditions of isothermal heat treatment on microstructure and mechanical properties of austempered ductile iron, especially different temperature of isothermal transformationof austenite and different holding time at this temperature, is shown in the paper.