Distribution of alkali, alkali earth, and despheroidizing elements in cast irons

Conclusions

• 1. Ca, Sr, Na, and Rb are unevenly distributed in cast iron, with notable enrichment of the graphite phase in the spheroidizing element. This distribution of elements remains unchanged with different residual concentrations of these elements in the cast iron and does not induce the formation of spheroidal graphite, which is evidently due to the weak spheroidizing capacity and the relatively small residual concentrations of these elements in inoculated cast irons (in the graphite phase).

• 2. The character of the microdistribution of the despheroidizing elements differs and is due above all to their physical and chemical properties, which determine the direction, intensity, and completeness of diffusion flows of despheroidizing elements, and consequently their enrichment of one or another of the phase and structural components.

• 3. Despite the difference in the distribution of Bi, Cu, Sb, Te, Tl, Cd, In, and Ag in cast irons, the mechanism of their spheroidizing effect on graphite in high-strength magnesium cast iron is the same and is due to formation of fairly stable chemical compounds, coordination groups, etc. of the Mg-despheroidizing element system, which sharply reduces the concentration of free magnesium atoms below the minimal level required for spheroidization of graphite, and thus induces weakening of the alloy.