Morphology and Phase Transformation in Rapidly Cooled Hypoeutectic Commercial Grey Iron

The role of cast iron in metallurgical industry worldwide is highly significant and despite decades of intensive research, the evolving solidification microstructure of this very important engineering material is ever revealing. Hence, this study shows how rapidly solidified Fe–C hypoeutectic commercial alloy can produce different morphologies and even phases at constant elemental composition. The research showcases powder droplets of different sizes ranging between 53 µm to 850 µm corresponding to cooling rate of 500 Ks-1 to 75,000 Ks-1 produced using state-of-the-art drop-tube technique. The microstructural analysis of the as-cast and the various rapidly cooled droplets was carried out using optical metallography, x-ray diffraction analysis and scanning electron microscopy; which reveals how cooling rate eventually influences the phase formation and emerging microstructures of the alloy from initial Graphite–Ferrite to Cementite–Martensitic phases in the as-cast and droplets respectively. Hence, the summary of the result shows that at constant elemental composition, cooling rate has significant effect on the structure and the eventual mechanical property (microhardness) of these versatile engineering materials as hardness increase with cooling due to increasing martensitic formation.