SUPERPLASTIC BEHAVIOR OF FINE-GRAINED WHITE CAST IRONS

Superplastic behaviour of three hypo-eutectic while cast irons with different carbon contents was investigated at elevated temperatures. Hot and warm working, and rapid solidification technology (RST) were used to refine the coarse cementite structure. The resulting microstructure consisted of a mixture of small carbides and fine ferrite grains. Hot and warm working was found to be a successful method to refine the structure of white cast irons having a carbon content of less than 2.6%. Rapid solidification technology was the most promising process to refine high carbon (> 3.0%) cast irons. The refined white cast irons exhibited low flow stress and high strain-rate sensitivity in both tensile and compression in the temperature range 650-770-degrees-C. Tensile elongation to failure of 300% was found for 3.0% C RST iron, 220%, 150% and 80% for 2.2%, 2.6% and 3.0% C hot and warm rolled cast irons, respectively.