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Bahmani, Mahmoud; Elliott, R.; Varahram, N.

doi:10.1023/a:1018687115732

Cited by 30 publications

(22 citation statements)

References 8 publications

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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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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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“…[1][2][3][4] The ADI, which is a nodular cast iron that undergoes a specially designed heat treatment, offers a good alternative to steels and aluminum alloys when high strength, good ductility, and low wear are required.…”

Section: Introductionmentioning

confidence: 99%

“…The typical chemical composition of the ductile iron is Fe-3.5 pct C-2.5 pct Si-0.4 pct Mn-0.05 pct Mg, but Cu might also be used to control the pearlitic transformation during the heat treatment. The heat treatment consists of the following two stages: (1) austenization at high temperature ranging between 1123 K (850°C) to 1223 K (950°C) for the period required to ensure that the matrix is fully austenitic, followed by rapid cooling to the austempering temperature; and (2) austempering-holding at a temperature T A below the bainite start temperature, in the range of 523 ‚ 723 K (250 ‚ 450°C), for a long time until the required microstructure in achieved. Finally, the samples are cooled by water quenching.…”

Section: Introductionmentioning

confidence: 99%

“…At the austempering temperature, the following two reactions may take place in a sequential order [1] :…”

Section: Introductionmentioning

confidence: 99%

“…(b) After a long enough dwell time, the hc-c decomposes to ferrite and iron carbides, the microstructure known as bainite. The carbides reduce the mechanical properties [1][2][3] of ADI, and therefore, the second reaction should be eliminated.…”

Section: Introductionmentioning

confidence: 99%

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Influence of Copper Addition and Temperature on the Kinetics of Austempering in Ductile Iron

Amran

Katsman

Schaaf

et al. 2010

Metall Mater Trans B

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Austempered ductile iron (ADI) is a material that exhibits excellent mechanical properties because of its special microstructure, combining ferrite and austenite supersaturated with carbon. Two ADI alloys, Fe-3.5 pct C-2.5 pct Si and Fe-3.6 pct C-2.7 pct Si-0.7 pct Cu, austempered for various times at 623 K (350°C) and 673 K (400°C) followed by water quenching, were investigated. The first ferrite needles nucleate mainly at the graphite/austenite interface. The austenite and ferrite weight fractions increase with the austempering time until stabilization is reached. The increase in the lattice parameter of the austenite during austempering corresponds to an increase of carbon content in the austenite. The increase in the ferrite weight fraction is associated with a decrease in microhardness. As the austempering temperature increases, the ferrite weight fraction decreases, the high carbon austenite weight fraction increases, but the carbon content in the latter decreases. Copper addition increases the high carbon austenite weight fraction. The results are discussed based on the phases composing the Fe-2Si-C system.

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Transformation characteristics of ductile iron austempered from intercritical austenitizing temperature ranges

2009

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Untitled

Cited by 30 publications

References 8 publications

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

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

Influence of Copper Addition and Temperature on the Kinetics of Austempering in Ductile Iron

Transformation characteristics of ductile iron austempered from intercritical austenitizing temperature ranges

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