Synchrotron quantification of graphite nodule evolution during the solidification of cast iron

Azeem, Mohammed Abdul; Bjerre, Mathias Karsten; Atwood, Robert C.; Tiedje, Niels Skat; Lee, Peter

doi:10.1016/j.actamat.2018.06.007

Cited by 37 publications

(46 citation statements)

References 28 publications

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“…It has been discussed that such a change in growth behaviour occurs when a graphite sphere is in partial contact with the melt. [21][22][23] This can happen when graphite is trapped between branches of a dendrite or through liquidation cracking due to dynamic conditions during solidification [liquation cracking ref].…”

Section: Resultsmentioning

confidence: 99%

“…Using an environmental cell described in detail by Azeem et al [12], the sample was heated to above the melting point and then cooled at a rate of 0.03 °C/s while 3D X-ray tomograms were recorded. Details on imaging, construction of tomograms and filtering follow the methodology developed in [12,13] and are described in detail in [14,15]. Binary images for quantification of particle shape and volume were obtained by filtering and segmenting reconstructed 3D volumes based on grey level variations representing differences in attenuation.…”

Section: Methodsmentioning

confidence: 99%

“…As described by Azeem el al. [14] variation in carbon and silicon concentration between dendrites in combination with stresses due to contraction and shrinkage during cooling, can break the austenite shell around a nodule so that it has direct contact with the liquid that has a high carbon content. During solidification, carbon is rejected to the liquid between dendrite arms so that the austenite solidus temperature is lowered.…”

Section: Possible Transition From Encapsulated To Growth In Contact Wmentioning

confidence: 99%

“…If, at the same time, local stresses occur it may be the cause of liquidation cracking as described in. [14] It means that austenite around a nodule can fracture so that the nodule gains access to the carbon enriched liquid. In contact with the liquid, the graphite can grow under conditions similar to a regular eutectic and at a higher rate than in the encapsulated state.…”

Section: Possible Transition From Encapsulated To Growth In Contact Wmentioning

confidence: 99%

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Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

Tiedje

Bjerre

Azeem

et al. 2018

Trans Indian Inst Met

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Analysis of local conditions on graphite growth and shape during solidification of ductile cast iron.Abstract 3D X-Ray tomography recordings have been used to study graphite growth during solidification of ductile cast iron. Using data from such recordings, it is shown how local growth conditions influence growth rate and morphology of nodules during solidification. The experiments show that it is common for nodules to gradually change shape during solidification so that sphericity decreases. It is also shown that different shapes of nodules can evolve in direct contact with liquid iron and also after when they are encapsulated in austenite.It is observed that a significant proportion of originally complete spherical nodules become less spherical via formation of protrusions on the surface, these new surfaces are observed to grow relatively faster.It is shown that encapsulation of the graphite nodule by austenite may be incomplete, and that at the end of solidification, partial encapsulation and the effect of the number of nearest graphite nodules play a crucial role in determining the final graphite morphology.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Possible Transition From Encapsulated To Growth In Contact Wmentioning

confidence: 99%

Section: Possible Transition From Encapsulated To Growth In Contact Wmentioning

confidence: 99%

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Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

Tiedje

Bjerre

Azeem

et al. 2018

Trans Indian Inst Met

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“…which was calculated using the total graphite mass after solidification as measured from tomograms obtained after solidification was complete. A thorough description of the experiment and data post-processing has been given in reference [17].…”

Section: In Situ Observations Of DCI Solidificationmentioning

confidence: 99%

A graphite nodule growth model validated by in situ synchrotron x-ray tomography

Bjerre

Azeem

Tiedje

et al. 2018

Modelling Simul. Mater. Sci. Eng.

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An accurate prediction of ductile cast iron microstructures is crucial for a science-based optimisation of cast component design. The number density and distribution of graphite nodules critically influence the mechanical performance of a component in service. Although models predicting nodule growth have been researched for many years, recent improvements have been impeded by lack of detailed experimental data on nodule growth kinetics for validation. This data has now been made available through in situ observations of the solidification of ductile cast iron using synchrotron X-ray tomography in combination with a high temperature environmental cell. In the present investigation, a new sphere of influence model for spheroidal graphite growth is proposed. It inherently incorporates the competition for carbon between neighbouring nodules and the depletion of carbon in the matrix.Comparing simulation results to the in situ observations of graphite growth, the sphere of 2 influence model successfully predicts both growth of individual nodules as well as the size distribution of a large nodule population during solidification.

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Recent trends in X‐ray‐based characterization of nodular cast iron

Andriollo

Zhang

et al. 2020

Mat Design & Process Comms

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Through various examples, this short review presents the main X‐ray‐based techniques that are available to characterize nodular cast iron at the microstructural level. Emphasis is placed on the enormous potential offered by the recent developments in X‐ray tomography, X‐ray diffraction, and digital volume correlation, which allow collecting microstructural and micromechanical information in 4D (3D plus time) during both casting and subsequent mechanical loading. The goal is to demonstrate that for nodular cast iron, which has an inherently three‐dimensional, composite microstructure, X‐ray‐based techniques provide some significant advantages over conventional microscopy. For this reason, these techniques can be instrumental in unveiling the mechanisms controlling both the formation of the microstructure as well as its micromechanical behavior during in‐service loading, thus paving the way to the development of improved process–structure–property relations.

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Synchrotron quantification of graphite nodule evolution during the solidification of cast iron

Cited by 37 publications

References 28 publications

Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

Analysis of Local Conditions on Graphite Growth and Shape During Solidification of Ductile Cast Iron

A graphite nodule growth model validated by in situ synchrotron x-ray tomography

Recent trends in X‐ray‐based characterization of nodular cast iron

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