An analysis of the amount of retained austenite in manganese alloyed austempered ductile iron

Austempered ductile iron (ADI) is a revolutionary material which has excellent mechanical properties with ease of manufacturing. Manganese addition to the ductile iron is a complex job as it may segregate at the grain boundary causing brittleness to the material. Hence, it is important to select the optimum level of manganese which may be added to the ADI without causing any adverse effect on the mechanical properties. In this study, the effect of manganese addition and heat treatment parameters on the amount of retained austenite is studied. Manganese is added in three different proportion. Microstructure and XRD analysis have shown that increasing the austempeirng temperature has resulted in the increase in volume fraction of retained austenite. Manganese addition up to 1 wt% did not cause any adverse effect on the amount of retained austenite. Higher volume fraction of retained austenite obtained at 420°C is found be 36%.