Effect of Sb addition and casting modulus on graphite morphology, microstructure and mechanical properties of ductile cast iron

In this study, the effects of Sb addition and casting modulus on the microstructure, morphology of graphite, and mechanical properties of ductile cast iron were investigated. For this purpose, a ductile cast iron with different casting modulus of 8, 15 and 30 mm were cast. Also, in order to examine the effect of Sb element in another mold with similar conditions, 0.01 wt% of Sb was added to the melt followed by the microstructure evaluation using an optical microscope. MIP4 image processing software was used to analyze the microstructure images. Brinell hardness and tensile tests were conducted to evaluate the mechanical properties. The results of this study showed that with increasing the casting modulus, nodule count decreased from 500 to 235 nodule per square mm, also nodularity decreased from 71 to 63%. In addition, the study of the results of hardness and the tensile test showed that with increasing the casting modulus, the hardness decreases from 289 to 212 HB and the yield strength from 430 to 350 MPa. Comparison of samples containing Sb and without Sb showed that Sb increased the nodularity, nodule count and volume fraction of perlite. For example, for the sample with 1 mm modulus, the presence of Sb increased the nodule count by 49%, improved the nodularity from 65% to 68.5%, and also increased the perlite volume fraction by almost 11%.