Sensitivity of Austempering Heat Treatment of Ductile Irons to Changes in Process Parameters

Boccardo, Adrián Dante; Dardati, Patricia Mónica; Godoy, Luis A.; Celentano, Diego J.

doi:10.1007/s11663-018-1222-y

Cited by 12 publications

(9 citation statements)

References 27 publications

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“…Heat treatment of iron materials has a long history but is still a matter of intensive research due to its complexity [ 1 , 2 , 3 , 4 ]. Phase transformation, diffusion and segregation at different temperatures in dependence of alloying elements, initial state and time allow in the case of austempered ductile iron (ADI) a wide field of properties.…”

Section: Introductionmentioning

confidence: 99%

Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content

et al. 2020

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The phase transformation to ausferrite during austempered ductile iron (ADI) heat treatment can be significantly influenced by the alloying element Mo. Utilizing neutron diffraction, the phase transformation from austenite to ausferrite was monitored in-situ during the heat treatment. In addition to the phase volume fractions, the carbon enrichment of retained austenite was investigated. The results from neutron diffraction were compared to the macroscopic length change from dilatometer measurements. They show that the dilatometer data are only of limited use for the investigation of ausferrite formation. However, they allow deriving the time of maximum carbon accumulation in the retained austenite. In addition, the transformation of austenite during ausferritization was investigated using metallographic methods. Finally, the distribution of the alloying elements in the vicinity of the austenite/ferrite interface zone was shown by atom probe tomography (APT) measurements. C and Mn were enriched within the interface, while Si concentration was reduced. The Mo concentration in ferrite, interface and austentite stayed at the same level. The delay of austenite decay during Stage II reaction caused by Mo was studied in detail at 400 °C for the initial material as well as for 0.25 mass % and 0.50 mass % Mo additions.

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Section: Introductionmentioning

confidence: 99%

Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content

et al. 2020

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“…The process of shaping the structure and properties of ADI cast iron has been known from the world literature for several decades. This applies to issues related to the numerical simulation, [8][9][10] kinetics of the austenitizing and austempering processes, [4][5][6][7][8]11,12] effect of alloying elements, [12][13][14][15] structure formation, [11,12,[16][17][18][19] mechanical and fatigue properties, [20][21][22][23] machinability, [24] and other applications. [25] The structural homogeneity and thermal stability affect the behavior of the material when subjected to static and dynamic loads within a wide temperature range (from extremely low to very high values).…”

Section: Introductionmentioning

confidence: 99%

Structure Homogeneity and Thermal Stability of Austempered Ductile Iron

Górny

Gondek

Tyrała

et al. 2021

Metall Mater Trans A

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Solid-state transformation during heat treatment is of great practical importance because it significantly affects the final structure, properties, and thermal stability of cast components. The present study highlights the issue of structure formation and its effect on the thermal stability of high-quality cast iron, namely, austempered ductile iron (ADI). In this study, experiments were carried out for castings with a 25-mm-walled thickness and under variable heat treatment conditions, i.e., austenitization and austempering within ranges of 850 °C to 925 °C and 250 °C to 380 °C, respectively. The X-ray diffraction (XRD) investigations were carried out within a range of − 260 °C to + 450 °C to study the structure parameters related to the XRD tests, which provided information related to the phase participation, lattice parameters, and stresses in the microstructure as well as with an expansion of the crystal lattice. The results also provide insight into the role of the structure and its homogeneity on the thermal stability of ADI cast iron. The present work also aims to develop strategies to suppress the formation of blocky-shaped austenite in the ADI structure to maintain a homogeneous microstructure and high thermal stability.

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“…From the viewpoint of material selection, ADI is therefore the most cost-effective solution in many applications, including automotive and light/heavy trucks, construction and mining equipment, railroad, agricultural, gears and crankshafts, and brackets, among others [5][6][7]. In the literature, numerous papers have been published on ADI: particularly, on the numerical simulation [8][9][10], kinetics of austenitizing and austempering processes [3][4][5][6][7][8], effect of alloying elements [11][12][13][14], structure formation [15][16][17], mechanical and fatigue properties [18][19][20][21][22], machinability [23], and other applications [24].…”

Section: Introductionmentioning

confidence: 99%

Role of Austenitization Temperature on Structure Homogeneity and Transformation Kinetics in Austempered Ductile Iron

et al. 2019

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This paper considers the important factors of the production of high-strength ADI (Austempered Ductile Iron); namely, the austenitization stage during heat treatment. The two series of ADI with different initial microstructures were taken into consideration in this work. Experiments were carried out for castings with a 25-mm-walled thickness. Variable techniques (OM, SEM, dilatometry, DSC, Variable Magnetic Field, hardness, and impact strength measurements) were used for investigations of the influence of austenitization time on austempering transformation kinetics and structure in austempered ductile iron. The outcome of this work indicates that the austenitizing temperature has a very significant impact on structure homogeneity and the resultant mechanical properties. It has been shown that the homogeneity of the metallic matrix of the ADI microstructure strongly depends on the austenitizing temperature and the initial microstructure of the spheroidal cast irons (mainly through the number of graphite nodules). In addition, this work shows the role of the austenitization temperature on the formation of Mg-Cu precipitations in ADI.

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Sensitivity of Austempering Heat Treatment of Ductile Irons to Changes in Process Parameters

Cited by 12 publications

References 27 publications

Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content

Phase Transition Kinetics in Austempered Ductile Iron (ADI) with Regard to Mo Content

Structure Homogeneity and Thermal Stability of Austempered Ductile Iron

Role of Austenitization Temperature on Structure Homogeneity and Transformation Kinetics in Austempered Ductile Iron

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