A transmission electron microscope study of 1 Pct Mn ductile iron with different austempering treatments

Nili‐Ahmadabadi, Mahmoud

doi:10.1007/s11661-998-0107-0

Cited by 14 publications

(6 citation statements)

References 10 publications

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“…Also, although some carbons remain supersaturated in the BF, a part of carbons in the BF can precipitate as carbides. This fact is in good agreement with the results shown in Refs [13,38,39].…”

Section: Resultssupporting

confidence: 93%

Role of pre-formed martensite on transformation of austempered ductile iron

Liu

Yang

Yuan

et al. 2017

Materials Science and Technology

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A commercial ductile iron is treated by a novel austempering process to obtain a good combination of strength and ductility. The samples are austenitised at 890°C for 10 min, then quenched into patented quenching liquid, and austempered in an electric furnace at 220°C for 5, 10, 30, 60, 240 and 600 min, respectively, finally air cooled. The bending test and the tensile test are conducted and microstructural features are analysed on the austempered ductile iron. The optimum mechanical property is achieved at 220°C for 240 min. Main reason for high strength and ductility is the formation of a fine structure consisting of multiple phases of pre-formed martensite and lath bainitic ferrite with film retained austenite.

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Section: Resultssupporting

confidence: 93%

Role of pre-formed martensite on transformation of austempered ductile iron

Liu

Yang

Yuan

et al. 2017

Materials Science and Technology

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“…After reaching 1178 K (905°C), the samples were austenitized for another 30 minutes. Other studies [22][23][24] used longer austenitizing times of 60 to 120 minutes which might be appropriate for higher alloyed grades. Our previous results showed that 30 minutes is sufficient time for carbon saturation of the austenite in unalloyed and low-alloyed ductile iron.…”

Section: Heat Treatmentmentioning

confidence: 99%

In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

Saal

Meier

et al. 2015

Metall Mater Trans A

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Phase fractions and austenite carbon contents in austempered ductile iron samples with three different nickel contents were determined by in situ neutron diffraction. The samples were austenitized at 1178 K (905°C) for 30 minutes and austempered for 3.5 hours at temperatures between 523 K and 723 K (250°C and 450°C) using a mirror furnace. Based on the in situ neutron diffraction studies, plateau times were derived, which determine the end of stage I reaction. The austenite contents increase for higher austempering temperatures when the austempering times are selected properly, considering the accelerated phase transformation at higher temperature. Appropriate austempering times were derived for austempering temperatures between 523 K and 723 K (250°C and 450°C). Increased nickel contents lead to higher austenite phase fractions. Moreover the retarding effect of nickel on the phase transformation was quantified. The plateau values of phase fraction and the according austempering times were converted to TTT diagrams. The evolution of the austenite carbon content shows a maximum at 623 K (350°C) austempering temperature. This can be explained by temperature-dependent carbide precipitation and carbon diffusion into lattice defects. Fine carbides within the ferrite could be found by preliminary APT analysis.

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“…According to Rouns and Rundman [12] and Ahmadabadi, [13] the austenite lattice parameter (a ) in angstroms (Å ) is related to the carbon content (C ) in wt% by the equation a (Å ) ¼ 3.548 þ 0.044C . A credible explanation for this expansion is that during soaking, carbon diffuses from the graphite nodules to the austenite matrix, resulting in an increase in the lattice parameter a of austenite.…”

Section: Austenitization Behaviormentioning

confidence: 99%

A Dilatometry Study of the Austenitization and Cooling Behavior of Ductile Iron Meant for the Production of Austempered Ductile Iron (ADI)

Zimba

Simbi

Chandra

et al. 2004

Materials and Manufacturing Processes

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An understanding of the kinetics of transformation during austenitization, cooling, and austempering of ductile iron is critical to achieving the desired microstructures and ultimately mechanical properties in austempered ductile iron (ADI). To this end, dilatometry experiments have been carried out to study the austenitization and cooling behavior of an unalloyed ductile iron. When a typical austenitization temperature of 900 C is used, unlike in steels, there is an initial expansion of the specimen, which levels off as the soaking time is increased. This occurs despite the fact that the temperature remains constant. This phenomenon, hitherto unreported, highlights the subtle differences between the austenitization of ductile irons and steels. The initial expansion is attributed to the increase in austenite lattice parameter, arising from the diffusion of carbon from the graphite nodules. The levelling off signals the saturation of austenite with carbon and can ORDER REPRINTS therefore be used as an indicator of the appropriate austenitization time. Studies of the cooling behavior of unalloyed ductile iron have also shown that the dilatometer can be used as a tool for determining the minimum cooling rates, which guarantee the formation of ausferrite during austempering. When ductile iron is appropriately heat-treated based on results from dilatometry studies, the mechanical properties obtained are typically superior and consistent.

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A transmission electron microscope study of 1 Pct Mn ductile iron with different austempering treatments

Cited by 14 publications

References 10 publications

Role of pre-formed martensite on transformation of austempered ductile iron

Role of pre-formed martensite on transformation of austempered ductile iron

In Situ Study of the Influence of Nickel on the Phase Transformation Kinetics in Austempered Ductile Iron

A Dilatometry Study of the Austenitization and Cooling Behavior of Ductile Iron Meant for the Production of Austempered Ductile Iron (ADI)

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