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Ramos, A. K., Diószegi, A., Guesser, W. L. & Cabezas, C. S. (2020). Microstructure of compacted graphite iron near critical shrinkage areas in cylinder blocks. International Journal of metalcasting
Open this publication in new window or tab >>Microstructure of compacted graphite iron near critical shrinkage areas in cylinder blocks
2020 (English)In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193Article in journal (Refereed) Epub ahead of print
Abstract [en]

To study the microstructure of CGI near areas prone to shrinkage, a special sample was developed that resembles critical areas in cylinder blocks. Foundry trials were conducted with different magnesium contents and inoculation amounts. Using color etching techniques to follow the solidification sequence, four areas were observed with different macrostructure: (i) direct chill and columnar region near the surface; (ii) small eutectic cells and small intercellular space; (iii) large eutectic cells and large intercellular space; and (iv) eutectic cells with carbides in the last to freeze area. By increasing the amount of inoculation, the size of the eutectic cells in the zone with large eutectic cells (iii) is reduced, and the eutectic cells are now smaller and more evenly distributed through the section. Increasing the magnesium content brings a similar effect. In zone (iv), the samples with less inverse chill formation show smaller shrinkage porosities, which are located in the same regions where the inverse chill are, between the eutectic cells, in the last to freeze areas; they also have higher amounts of spheroidal graphite in the last-to-freeze areas. The amount of inverse chill carbides observed in zone (iv) did not present any clear relation with inoculation levels or magnesium content variations used in the experiments. 

Place, publisher, year, edition, pages
Springer, 2020
Keywords
cast iron, compacted graphite iron, shrinkage porosity, solidification, Carbides, Cells, Cylinder blocks, Cylinders (shapes), Cytology, Etching, Eutectics, Graphite, Magnesium, Microstructure, Porosity, Shrinkage, Content variation, Eutectic cells, Intercellular spaces, Macrostructures, Solidification sequence, Spheroidal graphite
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-47702 (URN)10.1007/s40962-019-00403-3 (DOI)2-s2.0-85078178612 (Scopus ID);JTHMaterialIS (Local ID);JTHMaterialIS (Archive number);JTHMaterialIS (OAI)
Available from: 2020-02-03 Created: 2020-02-03 Last updated: 2020-02-03
Domeij, B. & Diószegi, A. (2020). The Distribution of Carbon in Austenite Studied on a Water-Quenched Compacted Graphite Iron Using Electron Probe Microanalysis. International Journal of metalcasting
Open this publication in new window or tab >>The Distribution of Carbon in Austenite Studied on a Water-Quenched Compacted Graphite Iron Using Electron Probe Microanalysis
2020 (English)In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193Article in journal (Refereed) Epub ahead of print
Abstract [en]

Spheroidal graphite is the defining microstructural feature of ductile iron and also plays an important role in compacted graphite iron. It is widely accepted that graphite spheroids are engulfed by austenite at an early stage of solidification after which their growth is impeded by the slow diffusion of carbon through a layer of austenite. In this work, a compacted graphite iron-containing spheroidal graphite was studied after interruption of its solidification by water quenching. Selected areas of a cross section of the castings were investigated using quantitative electron probe microanalysis, with emphasis on the distribution of carbon in austenite. The measured carbon concentration near graphite was generally below the theoretical carbon concentration in austenite at equilibrium with graphite at 1140 °C. Numerical simulations of diffusion of carbon in austenite around spheroidal graphite suggest that a zone of austenite around graphite was likely depleted of carbon during quenching, possibly explaining the low measured concentrations. The measured carbon concentration near graphite varied by as much as 0.3 wt%, with the lowest concentrations consistently found in the central region of compacted graphite–austenite eutectic cells. Regardless of whether these differences were present prior to quenching or are consequences thereof, they seem to reflect either departures from, or displacements of, the carbon concentration in austenite at equilibrium with graphite. This indicates that there is something about growth of graphite embedded in austenite which is not well understood. Concentrations of Si, Mn and Cu are near equal in the compared regions and do not explain the observed differences in carbon content near graphite.

Place, publisher, year, edition, pages
Springer, 2020
Keywords
austenite, carbon, cast iron, electron probe microanalysis, solidification, wavelength-dispersive spectroscopy
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-47896 (URN)10.1007/s40962-020-00425-2 (DOI)000516295700002 ()2-s2.0-85079487643 (Scopus ID)
Note

Funding details: VINNOVA; Funding text 1: Open access funding provided by Jönköping University. We extend our sincere gratitude to Kaj Grönlund and Gunilla Runnsjö, the engineers and operators of the electron microprobe, for their important contribution. This research was financed by VINNOVA, the Swedish Agency for Innovation, through the research project SPOFIC II, Grant No. (2013-04720), and by the Swedish Knowledge Foundation through the research project LeanCast, Grant No. (2018-0033). The projects are collaborations between Scania CV AB, Volvo Group Trucks Operation, SKF Mekan, Sintercast, CorrControl and Jönköping University.

Available from: 2020-02-26 Created: 2020-02-26 Last updated: 2020-03-18
Hernando, J. C., Elfsberg, J., Ghassemali, E., Dahle, A. & Diószegi, A. (2020). The role of primary austenite morphology in hypoeutectic compacted graphite iron alloys. International Journal of metalcasting
Open this publication in new window or tab >>The role of primary austenite morphology in hypoeutectic compacted graphite iron alloys
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2020 (English)In: International Journal of metalcasting, ISSN 1939-5981, E-ISSN 2163-3193Article in journal (Refereed) Epub ahead of print
Abstract [en]

This work investigates the role of primary austenite morphology on the eutectic and eutectoid microstructures and the ultimate tensile strength (UTS) in a hypoeutectic compacted graphite iron (CGI) alloy. The morphology of primary austenite is modified by isothermal coarsening experiments in which holding times up to 60 min are applied to the solid–liquid region after coherency. The cooling conditions for the subsequent eutectic and eutectoid reactions are similar. Miniaturized tensile tests are performed to evaluate the UTS. The morphological characteristics related to the surface area of primary austenite, the modulus of primary austenite, Mγ, and the hydraulic diameter of the interdendritic region, DHydID, increase with the cube root of coarsening time. The eutectic and eutectoid microstructures are not significantly affected by the morphology of primary austenite, thus indicating that the morphology of the interdendritic regions does not control the nucleation frequency and growth of eutectic cells or graphite. UTS decreases linearly with the increasing coarseness of primary austenite for similar eutectic and eutectoid microstructures, demonstrating the strong influence of primary austenite morphology on the UTS in hypoeutectic CGI alloys.

Place, publisher, year, edition, pages
Springer, 2020
Keywords
cast iron, compacted graphite iron, CGI, solidification, dendrites, primary austenite, UTS
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-47569 (URN)10.1007/s40962-020-00410-9 (DOI)000515610600001 ()2-s2.0-85078435803 (Scopus ID)
Funder
Vinnova, 2013-03303Knowledge Foundation, 2018-0033
Note

This paper is an invited submission to IJMC selected from presentations at the 2nd Carl Loper 2019 Cast Iron Symposium held September 30 to October 1, 2019, in Bilbao, Spain.

Available from: 2020-01-28 Created: 2020-01-28 Last updated: 2020-03-18
Ghasemi, R., Hassan, I., Ghorbani, A. & Diószegi, A. (2019). Austempered compacted graphite iron — Influence of austempering temperature and time on microstructural and mechanical properties. Materials Science & Engineering: A, 767, Article ID 138434.
Open this publication in new window or tab >>Austempered compacted graphite iron — Influence of austempering temperature and time on microstructural and mechanical properties
2019 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 767, article id 138434Article in journal (Refereed) Published
Abstract [en]

This study investigates the effect of austempering temperature and time on the microstructural and mechanical properties of unalloyed Compacted Graphite Iron (CGI) with an initially ferritic matrix structure. The as-cast CGI samples were first austenitised at 900 °C for 60 min in a furnace, then austempered in a closed salt bath at three austempering temperatures – 275, 325, and 375 °C – for different times; 30, 60, 90, and 120 min. Tensile properties, Brinell, Vickers and Rockwell C hardness values were evaluated for the as-cast and austempered CGI ones. LOM and SEM, EBSD analysis techniques were used for microstructure and phase analysis. A mixture of acicular ferrite and retained austenite was achieved in the austempered CGI samples. In general, a decrease in austempering temperature resulted in a decrease in retained austenite content, corresponding improvements in hardness and tensile strength, and a decrease in elongation values.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Austenitising, Austempered CGI, Ausferrite matrix, Retained austenite, Mechanical properties, EBSD
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-46357 (URN)10.1016/j.msea.2019.138434 (DOI)000494052200036 ()2-s2.0-85072385523 (Scopus ID)PP JTH 2019 embargo 24 (Local ID)PP JTH 2019 embargo 24 (Archive number)PP JTH 2019 embargo 24 (OAI)
Available from: 2019-09-25 Created: 2019-09-25 Last updated: 2019-11-20Bibliographically approved
Hernando, J. C., Elfsberg, J., Dahle, A. & Diószegi, A. (2019). Evolution of primary austenite and its influence on eutectic microstructures during coarsening of Fe-C-Si alloys. Materialia, 7, Article ID 100391.
Open this publication in new window or tab >>Evolution of primary austenite and its influence on eutectic microstructures during coarsening of Fe-C-Si alloys
2019 (English)In: Materialia, ISSN 2589-1529, Vol. 7, article id 100391Article in journal (Refereed) Published
Abstract [en]

The evolution of primary austenite morphology during isothermal coarsening has been studied in the three main Fe–C–Si alloys used in industry, LGI, CGI, and SGI. The dendritic microstructure increases length scale during coarsening accompanied by fragmentation and coalescence of austenite crystals. The morphological parameters, SDAS, Mγ, DhydID, and Dγ show a linear relation with the cube root of coarsening time, t1/3, with similar rates for the three different Fe–C–Si alloys. The eutectic microstructures after coarsening of primary austenite in CGI and SGI alloys are not significantly affected by the surface area of primary austenite and the size of the interdendritic regions. Fraction, nodularity, shape distribution of graphite particles and the number of nodules and eutectic cells are similar when studied as a function of coarsening time. These results suggest that the nucleation frequency in CGI and SGI, and the growth of eutectic microstructures in CGI, are not significantly influenced by the morphology of primary austenite.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Solidification; Coarsening; Dendrites; Austenite; Eutectic; EBSD; CGI; SGI
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-43552 (URN)10.1016/j.mtla.2019.100391 (DOI)2-s2.0-85068795536 (Scopus ID)PP JTH 2019 embargo 24 (Local ID)PP JTH 2019 embargo 24 (Archive number)PP JTH 2019 embargo 24 (OAI)
Funder
VinnovaKnowledge Foundation
Note

Included in thesis in manuscript form with the title "Evolution of primary austenite and its influence on eutectic microstructures during coarsening of Fe-C-Si alloys".

Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-09-02Bibliographically approved
Ghassemali, E., Hernando, J. C., Stefanescu, D. M., Diószegi, A., Jarfors, A. E. .., Dluhoš, J. & Petrenec, M. (2019). Revisiting the graphite nodule in ductile iron. Scripta Materialia, 161, 66-69
Open this publication in new window or tab >>Revisiting the graphite nodule in ductile iron
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 161, p. 66-69Article in journal (Refereed) Published
Abstract [en]

The growth mechanism of graphite nodules in ductile iron was experimentally investigated using high-resolution 3D tomography of an individual graphite nodule in a near-eutectic ductile iron. The dual beam scanning electron microscopy (FIB-SEM) technique was used for this purpose. Iron particles elongated in the radial direction were observed inside a graphite nodule. Some micro-voids were detected inside the nodule, mostly located at the end of the iron particles. These observations were compared with established theories about the growth of graphite nodules and iron entrapment/engulfment in between the graphite sectors during solidification of ductile iron. 

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
3D reconstruction, FIB, Growth mechanism, Solidification, Ductility, Graphite, Iron, Scanning electron microscopy, 3-d tomographies, Graphite nodules, Growth mechanisms, High resolution, Iron Particles, Micro voids, Radial direction, Cast iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41986 (URN)10.1016/j.scriptamat.2018.10.018 (DOI)000450375500015 ()2-s2.0-85055115924 (Scopus ID);JTHMaterialIS (Local ID);JTHMaterialIS (Archive number);JTHMaterialIS (OAI)
Available from: 2018-11-07 Created: 2018-11-07 Last updated: 2020-01-20Bibliographically approved
Hernando, J. C., Elfsberg, J., Ghassemali, E., Dahle, A. & Diószegi, A. (2019). The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys. Scripta Materialia, 168, 33-37
Open this publication in new window or tab >>The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys
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2019 (English)In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 168, p. 33-37Article in journal (Refereed) Published
Abstract [en]

The effect of primary austenite morphology on the ultimate tensile strength (UTS) of hypoeutectic compacted graphite Fe-C-Si alloys (CGI) is studied by isothermal coarsening experiments. Secondary dendrite arm spacing (SDAS) and the morphological characteristics related to the surface area of primary austenite, M γ and D ID Hyd , increase with the cube root of coarsening time. UTS decreases linearly with increasing coarseness of primary austenite. The eutectic and eutectoid microstructures are unaffected by the primary austenite morphology. These observations demonstrate the strong influence of primary austenite morphology on the mechanical properties of hypoeutectic CGI alloys.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Coarsening, Compacted graphite iron, Dendrites, Mechanical properties, UTS, Austenite, Dendrites (metallography), Graphite, Morphology, Ostwald ripening, Silicon alloys, Tensile strength, Morphological characteristic, Primary austenite, Secondary dendrite arm spacing, Si alloys, Surface area, Ultimate tensile strength, Iron alloys
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-43550 (URN)10.1016/j.scriptamat.2019.04.010 (DOI)000470798400008 ()2-s2.0-85064563538 (Scopus ID)PP JTH 2019 embargo 24 (Local ID)PP JTH 2019 embargo 24 (Archive number)PP JTH 2019 embargo 24 (OAI)
Funder
Vinnova, 2013-03303; 2013-04720Knowledge Foundation, 2018-0033
Available from: 2019-04-29 Created: 2019-04-29 Last updated: 2019-08-06Bibliographically approved
Svidró, J. T. & Diószegi, A. (2018). A novel measurement method to study the thermal aspects of moulding mixture decomposition. In: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings: . Paper presented at 73rd World Foundry Congress "Creative Foundry", 23-27 September 2018, Kraków, Poland (pp. 113-114). Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association
Open this publication in new window or tab >>A novel measurement method to study the thermal aspects of moulding mixture decomposition
2018 (English)In: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings, Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association , 2018, p. 113-114Conference paper, Oral presentation with published abstract (Refereed)
Abstract [en]

A wide variety of moulding mixtures are extensively used in the process of sand casting of metal components. The sector is continuously developing in production volume, moreover the expectations from the customers are increasing on monthly basis, also from the quality point of view. Even though mould and core manufacturing are well-organized processes in most foundries, technological problems still appear which may lead to casting defects. These trends are forcing metal casters to come up with fitting strategies to solve their daily production challenges, while their suppliers are expected to keep up the continuous development of their existing foundry products and to find innovative solutions. Research on moulding materials and their properties must also take the step forward accordingly to generate the necessary new knowledge. This paper summarizes the latest results of a novel measurement method suitable for studying the degradation characteristics of different moulding materials from a new perspective. The fundamentals of the method are based on thermal analysis, focusing on the heat absorption behaviour of sand mixtures regardless of binder type/amount or manufacturing process. 

Place, publisher, year, edition, pages
Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association, 2018
Keywords
Cold-box, Greensand, Moulding mixture, Thermal analysis, Cold boxes, Continuous development, Degradation characteristics, Innovative solutions, Manufacturing process, Measurement methods, Mixture decomposition, Foundries, Mixtures, Thermoanalysis, Molding
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-43375 (URN)2-s2.0-85062275328 (Scopus ID)9788390430638 (ISBN)
Conference
73rd World Foundry Congress "Creative Foundry", 23-27 September 2018, Kraków, Poland
Available from: 2019-03-22 Created: 2019-03-22 Last updated: 2019-03-22Bibliographically approved
Hellström, K., Svidró, P., Diaconu, L. V. & Diószegi, A. (2018). Density variations during solidification of grey cast Iron. Paper presented at 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017. Materials Science Forum, 155-162
Open this publication in new window or tab >>Density variations during solidification of grey cast Iron
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, p. 155-162Article in journal (Refereed) Published
Abstract [en]

As part of moving towards a sustainable production of diesel engines for heavy vehicle applications, the ability to predict casting defects has become ever so important. In order to model the solidification process for cast components correctly, it is of essence to know how the material will actually behave. To produce sound castings, often of complex geometry, the industry relies on various simulation software for the prediction and avoidance of defects. Thermophysical properties, such as density, play an important part in these simulations. Previous measurements of how the volume of liquid grey iron changes with temperature has been made with a conventional dilatometer. Measurements have also been made in the austenitic range, then on iron-carbon-silicon alloys with a carbon content lower than 1.5 wt%. Based on these measurements the density variations during solidification were calculated. The scope for this paper is to model the volume changes during solidification with the control volume finite difference method, using data from the density measurements. 

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Density, Grey cast iron, Measurement, Modelling, Simulation, Casting, Computer software, Defects, Density (specific gravity), Diesel engines, Finite difference method, Models, Silicon alloys, Solidification, Technology transfer, Thermodynamic properties, Complex geometries, Control volume finite difference methods, Density variations, Simulation software, Solidification process, Sustainable production, Cast iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41280 (URN)10.4028/www.scientific.net/MSF.925.155 (DOI)XYZ ()2-s2.0-85050011430 (Scopus ID)9783035710557 (ISBN)
Conference
11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017
Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2019-01-25Bibliographically approved
Svidró, P., Diószegi, A., Jönsson, P. G. & Stefanescu, D. M. (2018). Determination of pressure in the extradendritic liquid area during solidification. Journal of thermal analysis and calorimetry (Print), 132(3), 1661-1667
Open this publication in new window or tab >>Determination of pressure in the extradendritic liquid area during solidification
2018 (English)In: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 132, no 3, p. 1661-1667Article in journal (Refereed) Published
Abstract [en]

Complex-shaped lamellar graphite iron castings are susceptible to casting defects related to the volume change during solidification. The formations of these recurring defects are caused by the flow of the liquid in the intradendritic area, between the austenite dendrite arms, and in the extradendritic area between the austenite grains. The conditions for the liquid flow, in turn, are determined by the solidification behavior. The present study suggests a new measurement method and a novel calculation algorithm to determine the pressure of the extradendritic liquid during solidification. The method involves a spherical sample suspended in a measurement device, where the temperature and the volume changes are measured during solidification. The calculation algorithm is based on the numerical interpretation of the Clausius-Clapeyron equation where the temperature variation, the volume change and the released latent heat are processed to determine the local pressure of the extradendritic liquid area during solidification.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Volume change measurement; Fourier thermal analysis; Clausius-Clapeyron equation; Extradendritic liquid pressure; Lamellar graphite iron
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41094 (URN)10.1007/s10973-018-7088-z (DOI)000432215600022 ()2-s2.0-85042940249 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2018-08-03 Created: 2018-08-03 Last updated: 2019-03-05Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3024-9005

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