Transmission electron microscopy study of austempered nodular iron: Influence of silicon content, austenitizing time and austempering temperature

Franetovic, Vjekoslav; Shea, M. M.; Ryntz, Edward F.

doi:10.1016/0025-5416(87)90556-8

Cited by 34 publications

(14 citation statements)

References 14 publications

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“…For high silicon steels and cast iron it could be shown that at austempering temperatures below 623 K (350°C) fine carbides precipitate within the ferrite plates. [36,[42][43][44] With lower austempering temperatures, the possible carbon diffusion decreases, resulting in a higher local supersaturation. Therefore, the driving force for carbide precipitation increases.…”

Section: B Austenite Carbon Contentmentioning

confidence: 98%

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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: B Austenite Carbon Contentmentioning

confidence: 98%

“…The carbon's coefficient of expansion in austenite was derived from investigations of Ridley and Stuart [21] (k C c = 0.031 Å /pct).…”

Section: B Neutron Diffractionmentioning

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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“…During bainitic reactions, formation of carbides is minimized by the silicon content present in the ductile iron. Allowing carbon deposition into the austenitic matrix results in the formation of ferrite with low carbon solubility [4]. Carbon is deposited in austenite until this phase become stable at room temperature [5].…”

Section: Introductionmentioning

confidence: 99%

Austempered Ductile Iron (ADI): Influence of Austempering Temperature on Microstructure, Mechanical and Wear Properties and Energy Consumption

Sellamuthu

Samuel

Dinakaran

et al. 2018

Metals

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Alloyed Ductile iron, austenitized at 840 • C for 30 min in a special sealed austempering furnace, was austempered for 30 min in molten salt mixture at 4 trial temperatures of 300 • C, 320 • C, 340 • C and 360 • C. Tensile strength, yield strength, percentage elongation and impact energy were evaluated for the as-cast and austempered samples. Microstructures were investigated using microscopy, coupled with analyzing software and a scanning electron microscopy. The specific wear of samples was tested using pin-on-disc wear testing machine. X-ray diffraction was performed to calculate the amount of retained austenite present in the ausferrite matrix. As-cast microstructure consists of ferrite and pearlite, whereas austempered ductile iron (ADI) contains a mixture of acicular ferrite and carbon enriched austenite, called "ausferrite". Hardness and strength decreased, whereas ductility and impact strength improved with an increase in the austempering temperature. XRD analysis revealed that the increase in austempering temperature increased the retained austenite content. A decrease in wear resistance with austempering temperature was observed. Modified Quality Index (MQI) values were envisaged, incorporating tensile strength, elongation and wear resistance. MQI for samples austempered at 340 • C and 360 • C showed a better combination of properties. About an 8% reduction in energy consumption was gained when the heat treatment parameters were optimized.

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“…3(a) and 3(b), which are responsible for the higher hardness and strength values due to the high dislocation density in ferrite. 19) The ductility of such a microstructure is generally low because there is less RA (Fig. 7).…”

Section: Mechanical Propertiesmentioning

confidence: 99%

“…As shown in the present study, the volume fraction of ferrite is high at 270°C, whereas the volume fraction of RA is low. Because of the high dislocation density within the ferrite, 19) interactions between dislocations and carbon atoms are prevalent depending on the high volume fraction of ferrite at the low austempering temperature. Therefore, the strain-hardening exponent values obtained at the low austempering temperature would be high as a result of these interactions.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Effect of Microstructural Features on Mechanical and Magnetic Properties of Austempered High-silicon Ductile Irons

Yürektürk

Baydoğan

2017

ISIJ Int.

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Transmission electron microscopy study of austempered nodular iron: Influence of silicon content, austenitizing time and austempering temperature

Cited by 34 publications

References 14 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

Austempered Ductile Iron (ADI): Influence of Austempering Temperature on Microstructure, Mechanical and Wear Properties and Energy Consumption

Effect of Microstructural Features on Mechanical and Magnetic Properties of Austempered High-silicon Ductile Irons

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