Assessment of the microstructure evolution of an austempered ductile iron during austempering process through strain hardening analysis

Donnini, Riccardo; Fabrizi, Alberto; Bonollo, Franco; Zanardi, Franco; Angella, Giuliano

doi:10.1007/s12540-017-6704-y

Cited by 17 publications

(45 citation statements)

References 26 publications

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“…The ADI 1050 with chemical composition complying to ISO 17804:2005(E) [25] and nodular graphite fraction of 10 ± 1 % was first austenitized, then held in salt bath at the austempering temperature for fourteen different increasing times (t 1 , t 2 ,..., t 14 in arbitrary units) and then quenched. Detailed results on the tensile tests of the corresponding 14 samples are reported in [8,9].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…2, whilst excellent are the fits at high stresses where linear regions in the differential data dσ/dε p vs. σ are found in metallic materials, e.g. copper [3], stainless steel [28], cast irons [29] and DIs [7][8][9]. This discrepancy at low stresses in ductile materials like copper and stainless steels has been attributed to a transient of the dislocation structures evolution with straining [3,28].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…The parameter Θ o showed a wide low plateau between t 5 and t 13 . Based on microstructure findings and plastic behaviour analysis reported in [9] the process window was associated to the interval t 7 -t 11 . The minimum corresponding to the austempering time t 9 was found to be the time for the best ausferrite with the coarsest and highest volume fraction of γ HC without carbides ε' [9].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Based on microstructure findings and plastic behaviour analysis reported in [9] the process window was associated to the interval t 7 -t 11 . The minimum corresponding to the austempering time t 9 was found to be the time for the best ausferrite with the coarsest and highest volume fraction of γ HC without carbides ε' [9]. Before t 5 some martensite was found in the tensile tested samples, since the austempering reaction was not finished, whilst at t 14 transmission electron microscopy (TEM) observations found carbides ε' [9].…”

Section: Materials and Experimental Methodsmentioning

confidence: 99%

“…Recently it was reported that the dislocation-density-related Estrin equation could correlate the tensile plastic behaviour and the microstructure evolution of an ADI 1050 at different austempering times [8,9], and that the evolution of the Estrin equation parameters with austempering times could identify the process window to produce the best ausferrite [8,9]. Depending on the grade, ADIs are produced through austenitization in the range of temperatures 800-920°C, with subsequent holding in isothermal salt bath at temperatures typically between 250 and 400°C for the austempering transformation [10,15] γ → α + γ HC .…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Evaluation of Microstructure Quality in Ductile Irons Based on Tensile Behaviour Analysis

Donnini

Zanardi

Vettore

et al. 2018

MSF

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Abstract. Dislocation-density-related equations were proved to be promising tools to correlate tensile plastic behaviour and microstructure in ductile irons (DIs), revealing distinct relationships between equation parameters and microstructure features in austempered ductile irons (ADI) and isothermed ductile irons (IDI). These equations resulted to be successful also in the characterization of the austempering process through the plastic behaviour analysis of tensile tests of an ADI 1050 that was quenched at different times during austempering. The equation parameters could indeed be correlated to the time window for the best ausferrite, and could predict the precipitation of the deleterious ε' carbides for long austempering times. In the present work the results of the tensile plastic behaviour analysis of different DIs through dislocation-density-related equations are reported. The aim of the analysis was to test the capability of these equations to assess the microstructure quality of DIs and support their industrial production.

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Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Materials and Experimental Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Evaluation of Microstructure Quality in Ductile Irons Based on Tensile Behaviour Analysis

Donnini

Zanardi

Vettore

et al. 2018

MSF

Self Cite

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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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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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Assessment of the microstructure evolution of an austempered ductile iron during austempering process through strain hardening analysis

Cited by 17 publications

References 26 publications

Evaluation of Microstructure Quality in Ductile Irons Based on Tensile Behaviour Analysis

Evaluation of Microstructure Quality in Ductile Irons Based on Tensile Behaviour Analysis

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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