Effect of antimony on the nucleation process of spheroidal graphite iron

To further understand the influence of subversive elements on the nucleation process of spheroidal graphite, melts with antimony contents ranging from 0% to 0.0036% Sb were produced and poured into standard thermal analysis cups, which were quenched at increasing time intervals. Two different inoculants rich in Ce and Al were used. Nucleation sites were characterized through spectrums, mapping and line scans of a FEG-SEM equipment.

In most cases, Mg-Si-Al nitrides and Mg-Ca sulfides appeared to be the main nuclei, regardless of inoculation. The influence of these complex nitrides on the growth of graphite was determined. The presence of RE-inclusions in the nucleus of the graphite was very limited because of the lack of La and Ce in the Mg-treatment alloy. Sb can appear as inclusions in the matrix, in spiky graphite or as nucleation sites for ill-formed spheroidal graphite, depending on its content. Some dendritic graphite nucleating on Ca-inclusions was detected.