Ductile cast iron samples were austenitized at 927 °C and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 °C, 288 °C, 316 °C, 343 °C, 371 °C, and 399 °C. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pet retained austenite containing more than 1.8 wt pet carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of K<inf>IC</inf>2 against ?<inf>?</inf> (X<inf>?</inf>C<inf>?</inf>)1/2 resulted in a straight line, as predicted by the model.

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dc.contributor.authorPrasad Rao, P.
dc.contributor.authorPutatunda, S.K.
dc.date.accessioned2026-02-05T11:00:33Z
dc.date.issuedDependence of Fracture Toughness of Austempered Ductile Iron on Austempering Temperature
dc.description.abstract1998
dc.identifier.citationMetallurgical and Materials Transactions A: Physical Metallurgy and Materials Science, 1998, 29, 12, pp. 3005-3016
dc.identifier.issn10735623
dc.identifier.urihttps://doi.org/10.1007/s11661-998-0208-9
dc.identifier.urihttps://idr.nitk.ac.in/handle/123456789/28044
dc.publisherMinerals, Metals and Materials Society
dc.subjectAustenite
dc.subjectFractography
dc.subjectFracture toughness
dc.subjectMathematical models
dc.subjectMetallographic microstructure
dc.subjectMorphology
dc.subjectThermal effects
dc.subjectVolume fraction
dc.subjectAustempering temperature
dc.subjectNodular iron
dc.titleDuctile cast iron samples were austenitized at 927 °C and subsequently austempered for 30 minutes, 1 hour, and 2 hours at 260 °C, 288 °C, 316 °C, 343 °C, 371 °C, and 399 °C. These were subjected to a plane strain fracture toughness test. Fracture toughness was found to initially increase with austempering temperature, reach a maximum, and then decrease with further rise in temperature. The results of the fracture toughness study and fractographic examination were correlated with microstructural features such as bainite morphology, the volume fraction of retained austenite, and its carbon content. It was found that fracture toughness was maximized when the microstructure consisted of lower bainite with about 30 vol pet retained austenite containing more than 1.8 wt pet carbon. A theoretical model was developed, which could explain the observed variation in fracture toughness with austempering temperature in terms of microstructural features such as the width of the ferrite blades and retained austenite content. A plot of K<inf>IC</inf>2 against ?<inf>?</inf> (X<inf>?</inf>C<inf>?</inf>)1/2 resulted in a straight line, as predicted by the model.

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