Austempering and austempered ductile iron microstructure in copper alloyed ductile iron

The variation in the austempered microstructure, the volume fraction of retained austenite, X(gamma), the average carbon content of retained austenite, C(gamma), their product X(gamma)C(gamma) and the size of bainitic ferrite needles with austempering temperature for 0.6% Cu alloyed ductile iron have been investigated for three austempering temperatures of 270, 330, and 380 degreesC for 60 min at each temperature after austenitization at 850 degreesC for 120 min. The austempering temperature not only affects the morphology of bainitic ferrite but also that of retained austenite. There is an increase in the amount of retained austenite, its carbon content, and size of bainitic ferrite needles with the rise in austempering temperature. The influence of austempering time on the structure has been studied on the samples austempered at 330 degreesC. The increase in the austempering time increases the amount of retained austenite and its carbon content, which ultimately reaches a plateau.