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The results of previous works by the
primary author showed that the
mechanical properties of high Mn ductile iron can be increased by using successive austempering process. To study the effect of this process on the other alloyed ductile iron, a Ni-Cu-Mo ductile iron was selected. Impact and tensile test specimens were prepared form the alloy and austenitized at 900°C for 90 min. austempered at 375°C and subsequently austempered at 315°C for different periods. Optical and scanning electron microscopy were used to study the microstructures. The results of impact tests showed that impact energy is a function of austempering period of high and low astempering temperature. In addition, the results show that the successive austempering substantially improves mechanical properties of Ni-Cu-Mo iron which confirms beneficial effect
of this process on the different alloys of
ductile cast iron. The comparison between application of successive austempering on a 0.75 wt% Mn ductile iron and alloy used in this study, shows that the optimum
tensile strength of Ni-Cu-Mo iron is higher than high Mn iron, while their optimum elongation are almost identical; this is likely due to higher retained austenite in the high Mn iron.