Alloyed ductile Cast iron samples were produced using induction coreless furnace. The designed alloys have the following composition (3.4-3.8 % C , 2.3-2.7 % Si , 0.15-0.54 % Mn , 0.02 % S , 0.02 % p , 0.4-0.5 % Mo and variable Ni content from 0.5-4 % ) The austempering heat treatment was performed using Salt bath furnaces, at a temperature of 900° c for 30 min. and the isothermal transformation was carried out at temp. of 220° C and 400° C . Austempering transformation time was varied from 10 min. to 24 hrs. to investigate its effect on the final structure and mechanical properties .
The results showed that, the best ductility and impact toughness for Austempered alloyed ductile Cast iron at 400° C was obtained by holding time equal to 60 min., while the optimum holding time at 220° C was 2 hrs. More over the alloy containing 0.5 % Mo & 2-4 % Ni provokes increase in hardenability and mechanical properties .