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Abstract

Heat treatment is one of the preferred methods in altering material characteristic. In this present study, the effect of austenitizing temperature in double-quenching heat treatment process was studied on microstructure as well as exploring the phase constituents of ductile iron through x-ray diffraction (XRD)analysis.Ductile iron produced through conventional CO2 sand casting method. Ductile iron was heat treated by using the double-quenching method. The sample was annealed at 673K for 1.8 ks and subsequently oil quenched before austenitized at 3 different temperatures which those are 1123K, 1173K and 1223K for 3.6 ks respectively. Standard metallographic observation nodule and XRD analysis were done to characterize the microstructure and the constituents respectively. It is found that austenitizing process transforms the microstructure from pearlitic-ferritic matrix structure, which presented in annealing condition into martens tic. Marten site morphology becomes coarser and the nodularity of graphite nodule decreases as austenitizing temperature increases. But, austenitizing process seemingly gives no significant effect to the graphite nodule size. The presence of BCT marten site is validated by the presence of high-intensity (110) and (101) planes verified at 430 to 440 2? angles. Austenitizing sub-process of double-quenching heat treatment process does influence the marten site and graphite nodule morphologies. It transforms ferritic-pearlitic structure in as annealed ductile iron to martens tic matrix structure. The presence of Marten site and austenite can be validated by using XRD method with specific plane.