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Publications (10 of 107) Show all publications
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)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: 2018-08-28Bibliographically 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: 2018-09-06Bibliographically approved
Svidró, P., Diószegi, A. & Jönsson, P. G. (2018). Extended method of volume change measurements during solidification of lamellar graphite 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, 925, 163-170
Open this publication in new window or tab >>Extended method of volume change measurements during solidification of lamellar graphite iron
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, p. 163-170Article in journal (Refereed) Published
Abstract [en]

Lamellar graphite iron (LGI) is an important technical alloy used to produce cast components for the automotive and the marine industry. The performance of the component is defined by the solidification sequence. Therefore, a lot of research work has been done in the field of solidification. The present work introduces a new measurement approach that combines advanced dilatation measurements with thermal analysis to investigate the solidification of LGI. The method involves a thermally balanced spherical sample. The temperature values are measured in the geometrical center and on the surface of the sample. The released heat of solidification is calculated by using the Fourier Thermal Analysis (FTA) method. The displacement values are measured on the surface of the sample. The volume change is calculated from the displacement data. The dilatation results clearly shows the advantage of the multidirectional measurement. 

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Lamellar graphite iron, Thermal analysis, Volume change, Graphite, Marine industry, Solidification, Thermoanalysis, Cast components, Displacement value, Graphite iron, Solidification sequence, Technical alloys, Temperature values, Volume change measurement, Cast iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41283 (URN)10.4028/www.scientific.net/MSF.925.163 (DOI)2-s2.0-85050010354 (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
Funder
Knowledge Foundation
Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2018-08-28Bibliographically approved
Ghassemali, E., Jarfors, A. E. .. & Diószegi, A. (2018). On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components. Metals, 8(7), Article ID 551.
Open this publication in new window or tab >>On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components
2018 (English)In: Metals, E-ISSN 2075-4701, Vol. 8, no 7, article id 551Article in journal (Refereed) Published
Abstract [en]

A combination of direct austempering after solidification (DAAS) treatment and electron backscatter diffraction (EBSD) method was used to study the formation of micro-shrinkage porosities in ductile iron. Analyzing the aus-ferritic microstructure revealed that most of micro-shrinkage porosities are formed at the retained austenite grain boundaries. There was no obvious correlation between the ferrite grains or graphite nodules and micro-shrinkage porosities. Due to the absolute pressure change at the (purely) shrinkage porosities, the dendrite fragmentation rate during the DAAS process would be altered locally, which caused a relatively finer parent-austenite grain structure near such porosities.

Keywords
DAAS, EBSD, shrinkage porosity, austenite, graphite, nodule
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41066 (URN)10.3390/met8070551 (DOI)
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-07-26Bibliographically approved
Hernando, J. C. & Diószegi, A. (2018). On the primary solidification of compacted graphite iron: Microstructure evolution during isothermal coarsening. Materials Science Forum, 925, 90-97
Open this publication in new window or tab >>On the primary solidification of compacted graphite iron: Microstructure evolution during isothermal coarsening
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, p. 90-97Article in journal (Refereed) Published
Abstract [en]

It is widely accepted that in most commercial hypoeutectic alloys, both static mechanicalproperties and feeding characteristics during solidification, are extremely linked to the coarseness ofthe primary phase. It is therefore of critical importance to provide tools to control and predict thecoarsening process of the dendritic phase present in hypoeutectic melts. The characterization of theprimary phase, a product of the primary solidification, has traditionally been neglected whencompared to the eutectic solidification characterization in cast iron investigations. This workpresents the morphological evolution of the primary austenite present in a hypoeutectic compactedgraphite cast iron (CGI) under isothermal conditions. To that purpose, a base spheroidal graphitecast iron (SGI) material with high Mg content is re-melted in a controlled atmosphere and reversedinto a CGI melt by controlling the Mg fading. An experimental isothermal profile is applied to thesolidification process of the experimental alloy to promote an isothermal coarsening process of theprimary austenite dendrite network during solid and liquid coexistence. Through interruptedsolidification experiments, the primary austenite is preserved and observed at room temperature. Byapplication of stereological relations, the primary phase and its isothermal coarsening process arecharacterized as a function of the coarsening time applied. The microstructural evolution observedin the primary austenite in CGI and the measured morphological parameters show a similar trend tothat observed for lamellar graphite cast iron (LGI) in previous investigations. The modulus of theprimary austenite, Mγ, and the nearest distance between the centre of gravity of neighbouringaustenite particles, Dγ, followed a linear relation with the cube root of coarsening time.

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Primary austenite, Microstructure evolution, Dendritic coarsening, Compacted Graphite Iron, CGI
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-40548 (URN)10.4028/www.scientific.net/MSF.925.90 (DOI)XYZ ()2-s2.0-85050029582 (Scopus ID)
Available from: 2018-06-19 Created: 2018-06-19 Last updated: 2018-08-28Bibliographically approved
Diószegi, A., Diaconu, L. V. & Jarfors, A. E. .. (Eds.). (2018). Science and Processing of Cast Iron XI. Paper presented at 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017. Trans Tech Publications
Open this publication in new window or tab >>Science and Processing of Cast Iron XI
2018 (English)Conference proceedings (editor) (Refereed)
Abstract [en]

The goal of this book is to present for readers the articles from the 11th International Symposium on the Science and Processing of Cast Iron that was held in September 2017 in Jönköping, Sweden. The content of the book reflects the state of the art, research and development tendencies of cast iron as the main engineering cast material also in the 21st century.

Place, publisher, year, edition, pages
Trans Tech Publications, 2018. p. 546
Series
Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752 ; 925
Keywords
Cast Iron, Characterization, Defect Formation, Modelling, Properties, Simulation, Solidification, Structure Formation
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41397 (URN)10.4028/www.scientific.net/MSF.925 (DOI)978-3-0357-1055-7 (ISBN)978-3-0357-2055-6 (ISBN)978-3-0357-3055-5 (ISBN)
Conference
11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017
Available from: 2018-09-10 Created: 2018-09-10 Last updated: 2018-09-10Bibliographically approved
Domeij, B., Hernando, J. C. & Diószegi, A. (2018). Size distribution of graphite nodules in hypereutectic cast irons of varying nodularity. Metallurgical and materials transactions. B, process metallurgy and materials processing science
Open this publication in new window or tab >>Size distribution of graphite nodules in hypereutectic cast irons of varying nodularity
2018 (English)In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916Article in journal (Refereed) Epub ahead of print
Abstract [en]

An SGI was machined into 400 g cylindrical pieces and remelted in an electrical resistance furnace protected by Ar gas to produce materials ranging from SGI to CGI. The graphite morphology was controlled by varying the holding time at 1723 K (1450 °C) between 10 and 60 minutes. The discrete sectional size distribution of nodules by number density was measured on cross sections of the specimens and translated to volumetric distribution by volume fraction. Subpopulations of nodules were distinguished by fitting Gaussian distribution functions to the measured distribution. Primary and eutectic graphite, were found to account for most of the volume of nodular graphite in all cases. For holding times of 40 minutes and greater, corresponding to nodularity roughly below 40 pct, the primary subpopulation was very small and difficult to distinguish, leaving eutectic nodules as the dominant subpopulation. The mode and standard deviation of the two subpopulations were roughly independent of nodularity. Moreover, the nodular and vermicular graphite were segregated in the microstructure. In conclusion, the results suggest that the parallel development of the vermicular eutectic had small influence on the size distribution of eutectic graphite nodules.

Place, publisher, year, edition, pages
Springer, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-35530 (URN)10.1007/s11663-018-1274-z (DOI)XYZ ()2-s2.0-85048767236 (Scopus ID)
Note

Included in licentiate thesis by Björn Domeij (2017), On the solidification of compacted and spheroidal graphite irons, as manuscript.

Available from: 2017-05-16 Created: 2017-05-16 Last updated: 2018-07-03
Domeij, B. & Diószegi, A. (2018). Solidification Chronology of the Metal Matrix and a Study of Conditions for Micropore Formation in Cast Irons Using EPMA and FTA. 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, 925, 436-443
Open this publication in new window or tab >>Solidification Chronology of the Metal Matrix and a Study of Conditions for Micropore Formation in Cast Irons Using EPMA and FTA
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, p. 436-443Article in journal (Refereed) Published
Abstract [en]

Microsegregation is intimately coupled with solidification, the development of microstructure, and involved in the formation of various casting defects. This paper demonstrates how the local composition of the metal matrix of graphitic cast irons, measured using quantitative electron microprobe analysis, can be used to determine its solidification chronology. The method is applied in combination with Fourier thermal analysis to investigate the formation of micropores in cast irons with varying proportions of compacted and spheroidal graphite produced by remelting. The results indicate that micropores formed at mass fractions of solid between 0.77 and 0.91, which corresponded to a stage of solidification when the temperature decline of the castings was large and increasing. In 4 out of the 5 castings, pores appear to have formed soon after the rate of solidification and heat dissipation had reached their maximum and were decreasing. While the freezing point depression due to build-up of microsegregation and the transition from compacted to spheroidal type growth of the eutectic both influencing solidification kinetics and the temperature evolution of the casting, the results did not indicate a clear relation to the observed late deceleration of solidification.

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Solidification, Microsegregation, EPMA, Microporosity, Cast Iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-40787 (URN)10.4028/www.scientific.net/MSF.925.436 (DOI)2-s2.0-85050037946 (Scopus ID)
Conference
11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Jönköping, Sweden, 4-7 September 2017
Available from: 2018-06-25 Created: 2018-06-25 Last updated: 2018-08-28Bibliographically approved
Fourlakidis, V., Diaconu, L. V. & Diószegi, A. (2018). Strength prediction of lamellar graphite iron: From Griffith’s to hall-petch modified equation. 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, 925, 272-279
Open this publication in new window or tab >>Strength prediction of lamellar graphite iron: From Griffith’s to hall-petch modified equation
2018 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 925, p. 272-279Article in journal (Refereed) Published
Abstract [en]

Traditionally, ultimate tensile strength (UTS) is used as the main property for the characterization of lamellar graphite iron (LGI) alloys under static loads. The main models found in the literature for predicting UTS of pearlitic lamellar graphite iron are based on either regression analysis on experimental data or on modified Griffith or Hall-Petch equation. In pearlitic lamellar graphite iron the primary austenite dendritic network, transformed to pearlite, reinforces the bulk material while the distance between those pearlite grains, defines the maximum continuous defect size in the bulk material. Recently the novel parameter of the Diameter of Interdendritic Space has been used to express the flow length in a modified Griffith equation for the prediction of the UTS in LGI. Nevertheless this model neglects the strengthening effect of the pearlite lamellar spacing within the perlite grains. A model based on modified Hall-Petch equation was developed in this work. The model considers the effect of both microstructure parameters and covers a broad spectrum of microstructure sizes typical for complex shape castings with various wall thicknesses. 

Place, publisher, year, edition, pages
Trans Tech Publications, 2018
Keywords
Lamellar graphite iron, Pearlite spacing, Primary austenite, Tensile strength, Austenite, Forecasting, Graphite, Materials handling equipment, Microstructure, Pearlite, Regression analysis, Graphite iron, Interdendritic space, Micro-structure parameters, Strength prediction, Strengthening effect, Ultimate tensile strength, Cast iron
National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41295 (URN)10.4028/www.scientific.net/MSF.925.272 (DOI)2-s2.0-85050010996 (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: 2018-08-29 Created: 2018-08-29 Last updated: 2018-08-29Bibliographically approved
Lidumnieks, K., Svidró, J. T. & Diószegi, A. (2018). The effect of various production parameters on the heat absorbing capacity of greensand. International Journal of Cast Metals Research, 31(1), 7-13
Open this publication in new window or tab >>The effect of various production parameters on the heat absorbing capacity of greensand
2018 (English)In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 31, no 1, p. 7-13Article in journal (Refereed) Published
Abstract [en]

Greensand is a widely-used material to produce sand moulds in high production, mainly for iron casting applications. Several authors have studied the high temperature behavior of greensand regarding to the vapour condensation and transfer zones, and the effect of different production parameters on the thermal conductivity. This work focuses on the effect of the mixture composition on the heat absorption (cooling) capacity of the greensand. During the experimental work, various greensand mixtures with changing bentonite + water and coal dust contents were prepared and tested by a novel application of Fourier thermal analysis. The method provides new thermophysical knowledge about moulding sand, through applying real casting conditions by the immersion of spherical sand samples into liquid iron. The findings of the work direclty contribute to the area of thermal sciences and also brings novel understandings to foundry technology in general.

Place, publisher, year, edition, pages
Maney Publishing, 2018
Keywords
Bentonite, cast iron, casting, coal dust, Fourier thermal analysis, greensand, heat absorption, thermal properties, Absorption cooling, Coal water mixtures, Iron, Mixtures, Sandstone, Thermal conductivity, Thermoanalysis, Thermodynamic properties, Foundry technology, Fourier, High temperature behavior, Mixture compositions, Novel applications, Production parameters
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-41017 (URN)10.1080/13640461.2017.1348005 (DOI)000428582500002 ()2-s2.0-85023164116 (Scopus ID)JTHMaterialIS (Local ID)JTHMaterialIS (Archive number)JTHMaterialIS (OAI)
Available from: 2018-07-19 Created: 2018-07-19 Last updated: 2018-07-19Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-3024-9005

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