C, Si and Ni as alloying elements to vary carbon equivalent of austenitic ductile cast iron: Microstructure and mechanical properties

Successful casting of three groups of austenitic ductile irons was achieved covering a carbon equivalent (CE) range from 3.51% to 5.04%. The three groups implied the change of C, Si or Ni contents to control the CE%. In case of using Ni element to vary CE%, austenitic ductile iron could be obtained starting from 13.5% up to 34.7% Ni. Generally, the microstructure consisted of graphite nodules embedded in austenitic matrix. Nodule characteristics were affected by the variation of CE%. Nodularity was almost 100% for all tested specimens. Slight decrease in hardness and tensile strength (σu) was observed with increasing the CE%. 0.2% proof stress (σ0.2) showed almost a constant value with increasing CE%. Tensile elongation was mainly increased with increasing CE% with different degrees owing to the alloying element (C, Si or Ni).