Carbide Morphology Observations in Rare-Earth-Treated Fe-Al-Si-C Alloys

Aluminum-alloyed grey cast irons have been tried in industrial applications demanding moderate heat resistance. However, they tend to suffer from oxidation, dross entrapment during melting, and a loss of ductility at ambient temperatures. In addition, aluminum-alloyed grey iron containing approximately 2.4 wt.% carbon and 0.5–2.0 wt.% silicon can exhibit three different microstructures, depending on the aluminum content [1]. With a low aluminum content, as much as about 6%, the microstructure is one of flake graphite in a pearlitic matrix. With the aluminum content between 6 and 20%, a complex iron-aluminum carbide (k-phase) is formed. Aluminum contents in the 20–30% range produce a ferrite matrix.