Summary
The approaches including an automated SEM/EDX analysis of graphite nodule nucleation sites, the special algorithms to convert two-dimensional to three-dimensional graphite nod- ule size distribution, and reconstructed heterogeneous nucle- ation kinetics were suggested and tested. Three-dimensional size distributions of graphite nodules in different industrial and laboratory produced ductile iron were investigated. It was shown that both the cooling rate and post-inoculation affected the volumetric size distribution mode. These modes could be near normal distribution or bi-modal and even more complicated in heavy sections. Volumetric nodule graphite size distribution modes were discussed taking into consid- eration efficiency of heterogeneous nucleation and recon- structed solidification kinetics.
For determination of the chemical nature of heterogeneous nuclei, the “soft” quenching technique was applied to de- velop small graphite nodules and increase the probability to reveal non-metallic heterogeneous nuclei using automated SEM/EDX analysis. It was shown that partitioning of non- metallic inclusions between metal matrix and inclusions enclosed into graphite nodules takes place. Thermodynamic analysis was used to predict non-metallic inclusion forma- tion sequences and correlate it with observed inclusion par- titioning.
Acknowledgments
Dr. V. Richards, Dr. K. Peaslee, and PhD student Jingjing Qing for help and support.
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International Journal of Metalcasting/Volume 8, Issue 2, 2014
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