Formation of bainite in ductile iron

Kutsov, A. Yu.; Taran, Yu. N.; Uzlov, К. І.; Krimmel, A.; Evsyukov, M. F.

doi:10.1016/s0921-5093(99)00332-9

Cited by 33 publications

(23 citation statements)

References 5 publications

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“…It has often been observed that films of carbon-enriched austenite become trapped between bainite sub-units. 6,9,10) The composition of these austenite films is close to the value given by the AeЈ 3 curve 6) (i.e. the composition of the (aϩg)/g phase boundary in paraequilibrium conditions).…”

Section: Carbon Redistributionsupporting

confidence: 66%

“…the locus where austenite and ferrite of the same composition have the same Gibbs free energy. 9) The effect of the austenite composition and grain size, the carbon redistribution, the entrapment of carbon-enriched austenite films between bainite sub-units [10][11][12] and the role of newly formed bainite sub-units as potential nucleation sites (autocatalysis or sympathetic nucleation) 5,[13][14][15] are all issues that need to be considered in a model describing this reaction. Furthermore, the extreme case of very small austenite grains that constrain the growth of the bainite sub-units is particularly interesting, since it may involve the interaction of the strains generated during the transformation with the transformation kinetics, and an early soft impingement.…”

Section: Introductionmentioning

confidence: 99%

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A New Physical Model for the Kinetics of the Bainite Transformation

Gaude-Fugarolas

Jacques

2006

ISIJ Int.

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A model describing the bainite reaction is presented that takes into account the effect of very small austenite grain size. This model considers the displacive approach and uses thermodynamic criteria for the description of the nucleation and growth of bainite sub-units forming either at grain boundaries or autocatalytically on previous sub-units. The evolution of the austenite composition with the partitioning and redistribution of carbon is estimated as the transformation proceeds. The size of the sub-units is calculated for each composition and temperature.The transformation kinetics, as well as the incomplete reaction phenomenon, are correctly predicted. Furthermore, the influence of the austenite grain size on the bainite transformation rate is addressed in the case of austenite grains smaller than the length of an unconstrained bainite sub-unit. In this case, the observed enhanced nucleation rate is semi-empirically related to the austenite yield strength. This semi-empirical relationship is corroborated with kinetics data from different alloys.

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Section: Carbon Redistributionsupporting

confidence: 66%

Section: Introductionmentioning

confidence: 99%

A New Physical Model for the Kinetics of the Bainite Transformation

Gaude-Fugarolas

Jacques

2006

ISIJ Int.

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“…The chemical composition of the first material (to be termed ductile iron 1): 3.2% C, 2.4% Si, 0.21% Mn, 0.59% Ni, 0.62% Cu i 0.13% Mo [10]. Second austempered ductile iron (to be termed ductile iron 2) contains: 3,6%C, …”

Section: Ttt Diagrams For Selected Ductile Ironsmentioning

confidence: 99%

“…[10] The relationships between parameters k, n and isothermal soaking temperature for both ductile irons are presented in Fig. 6.…”

Section: Mathematical Description Of Ttt Diagramsmentioning

confidence: 99%

Parametric Representation of TTT Diagrams of ADI Cast Iron

Olejarczyk-Wożeńska¹,

Adrian²,

Adrian³

et al. 2012

Archives of Metallurgy and Materials

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The method of parametric representation of TTT diagrams on example of selected austempered ductile cast irons is presented. TTT diagrams were digitalised and n, k parameters of Johnson Mehl equation were calculated. The relationships between n, k parameters and transformation temperature were analysed for two ADI irons. Knowledge of these parameters enables to calculate the progress of austenite to bainite transformation.Keywords: TTT diagrams, austempered ductile iron, bainitie transformation W pracy zaprezentowano metodykę parametrycznej reprezentacji wykresów CTP i na przykładzie wybranych wykresów dla żeliw sferoidalnych. Wykresy CTP i digitalizowano, a następnie obliczano parametry n i k równania Johnsona-Mehla opisującego postęp przemiany przechłodzonego austenitu w bainit. Analizowano wpływ temperatury przemiany na wartość parametrów n, k. Znajomość tych parametrów pozwala obliczać postęp przemiany austenitu w bainit przy danej temperaturze.

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“…Retained austenite present in ADI in the reacted stable and unreacted metastable forms may be subjected to martensitic transformation proceeding at different stages of austempering, especially while final cooling to the room temperature. A description of problems related to these harmful phenomena decreasing mechanical properties, mainly ductility, can be found, for example, in the publications [1,12,[15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Optimization of mechanical properties of complex, two-stage heat treatment of Cu–Ni (Mn, Mo) austempered ductile iron

Gazda

Warmuzek

Bitka

2018

J Therm Anal Calorim

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The aim of the study was to design and optimize the complex, two-step heat treatment of Cu-Ni (Mn, Mo) ductile iron. A method for the formation and investigation of austempered ductile iron (ADI) by means of complex two-step and as comparative, standard one-step heat treatments has been developed, using quenching dilatometer. Investigations of proceeding phase transformations using differential dilatometric and DSC analysis supported by microstructural observations, hardness and austenite volume measurements have been carried out. An analysis of the temperature sequence of the ausferrite decomposition in the one-step and two-step ADI was performed, which allowed for the separation and identification of the effects responsible for the carbon-enriched austenite decomposition. A quantitative relationship was established between basic dimensional effects revealed on the differential dilatometric curve of ausferrite decomposition, which enables prognosis and optimization of the parameters of complex ADI heat treatment variants. Verification tests were performed on a stand equipped with salt furnaces enabling a quick transfer of samples from one bath to another without changing their initial temperature. Optimization of the two-step ADI heat treatment with the use of quantitative dilatometric analysis of the ausferrite decomposition, allowed to obtain for the temperature step-down heat treatment 390°C/15, 20 min ) 270°C/130 min the excellent mechanical properties, unattainable by means of standard 1-step ADI heat treatment.

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Formation of bainite in ductile iron

Cited by 33 publications

References 5 publications

A New Physical Model for the Kinetics of the Bainite Transformation

A New Physical Model for the Kinetics of the Bainite Transformation

Parametric Representation of TTT Diagrams of ADI Cast Iron

Optimization of mechanical properties of complex, two-stage heat treatment of Cu–Ni (Mn, Mo) austempered ductile iron

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