Study of microstructure and silicon segregation in cast iron using color etching and electron microprobe analysis

• Sensitivity of a color etchant to silicon segregation is quantitatively demonstrated.
• Si segregation measurement by EMPA approved the results achieved by color etching.
• Color etched micrographs provided data about solidification mechanism in cast irons.
• Austenite grain boundaries were identified by measuring the local Si concentration.

An investigation on silicon segregation of lamellar, compacted and nodular graphite iron was carried out by applying a selective, immersion color etching and a modified electron microprobe to study the microstructure. The color etched micrographs of the investigated cast irons by revealing the austenite phase have provided data about the chronology and mechanism of microstructure formation. Moreover, electron microprobe has provided two dimensional segregation maps of silicon. A good agreement was found between the segregation profile of silicon in the color etched microstructure and the silicon maps achieved by electron microprobe analysis. However, quantitative silicon investigation was found to be more accurate than color etching results to study the size of the eutectic colonies.