IJMC/FEF Student Research Competition

Ductile iron is renowned for its superior mechanical properties, higher strength, and ductility, combined with excellent castability and the economy of using a scrap melting process. The matrix structure as well as morphology and distribution of graphite nodules significantly influences mechanical properties of as-cast ductile iron. Boron contamination of the scrap supply has presented some difficulties in controlling the microstructure and mechanical properties of certain gray and ductile iron grades. In the current study, the effect of boron levels up to 95 ppm was determined on graphite nodularity and distribution in as-cast ductile iron castings as a function of section size. This was accomplished using a combination of light optical microscopy and scanning electron microscopy with automated feature analysis. The mechanisms underlying the influence of boron on graphite nucleation, growth, and distribution are discussed. Preliminary data serve as a basis for which to evaluate acceptable concentrations of boron for desired mechanical properties.