EBSD Analysis of the Primary Austenite Grains in Lamellar Graphite Cast Iron

Abstract

This work investigates the size and morphology of the primary austenite grains present in lamellar graphite cast iron. Samples of lamellar graphite iron were cast and austempered during the post-solidification cooling stage in order to preserve part of the original austenite at room temperature. Electron backscatter diffraction technique was applied to reveal the regions of different crystalline orientation of the austenite. The eutectic colonies and the last-to-freeze areas were also examined by color etching of the same regions previously analyzed by electron backscatter diffraction. The results reveal that the solidification units of lamellar graphite iron are formed by austenite grains that include several eutectic colonies inside, all of which have the same crystalline orientation as the primary austenite grain. For all the samples studied, it can be confirmed that there are no eutectic colonies with a different crystalline orientation than that of the primary austenite dendrites.