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Publications (10 of 114) Show all publications
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: 2018-12-10Bibliographically 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)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
Diószegi, A. & Svidró, P. (2018). Method of and device for analysing a phase transformation of a material. us US2018284043.
Open this publication in new window or tab >>Method of and device for analysing a phase transformation of a material
2018 (English)Patent (Other (popular science, discussion, etc.))
Abstract [en]

A method of analyzing a phase transformation process of a material comprises providing a spherical sample of the material, measuring and recording a first data series of core temperature at the sample's center of gravity, measuring and recording a respective second data series of temperature at the sample's periphery, measuring and recording a respective third data series of radial displacements at the sample's periphery, and calculating a change in pressure in the sample at a plurality of points in time based on first, second and third said data series.

National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41982 (URN)
Patent
US US2018284043 (2018-10-04)
Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06
Svidró, J. T. & Diószegi, A. (2018). Novel Measurement Method to Study Thermal Aspects of Molding Mixture Decomposition. Journal of Casting & Materials Engineering, 2(3), 63-66
Open this publication in new window or tab >>Novel Measurement Method to Study Thermal Aspects of Molding Mixture Decomposition
2018 (English)In: Journal of Casting & Materials Engineering, E-ISSN 2543-9901, Vol. 2, no 3, p. 63-66Article in journal (Refereed) Published
Abstract [en]

A wide variety of molding mixtures are extensively used in the process of the sand casting of metal components today. The sector is continuously developing in production volume; moreover, the expectations of customers are increasing on a monthly basis (also from a quality point of view). Even though mold and core manufacturing are well-organized routines in most foundries, technological problems still appear that can lead to technological problems and 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 as well as new material combinations. Research on molding materials and their properties must, therefore, take a step forward accordingly to generate the necessary new knowledge to understand the behavior of mold and core mixtures during casting.

This paper summarizes the latest results of a novel measurement method suitable for studying the degradation characteristics of different molding materials from a new perspective. The fundamentals of the method are based on a thermal analysis, focusing on the heat-absorption behavior of greensand and two types of chemically bonded sands regardless of the binder type and amount or the manufacturing process.

Place, publisher, year, edition, pages
AGH University of Science and Technology Pres, 2018
National Category
Metallurgy and Metallic Materials
Identifiers
urn:nbn:se:hj:diva-42097 (URN)10.7494/jcme.2018.2.3.63 (DOI)
Available from: 2018-11-20 Created: 2018-11-20 Last updated: 2018-11-20
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.

Place, publisher, year, edition, pages
MDPI, 2018
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)000445096800081 ()2-s2.0-85050550978 (Scopus ID)
Available from: 2018-07-25 Created: 2018-07-25 Last updated: 2018-10-26Bibliographically 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
Svidró, P. & Diószegi, A. (2018). Sampling device and method for sampling a liquid or viscous material. EPO (European Patent Office) EP3356782.
Open this publication in new window or tab >>Sampling device and method for sampling a liquid or viscous material
2018 (English)Patent (Other (popular science, discussion, etc.))
Abstract [en]

A sampling device for sampling a liquid or viscous comprises a receptacle, having a wall which is formed of a material having a higher melting point than that of the material, and a probe channel extending from outside the receptacle and to the receptacle's center of gravity. The receptacle is substantially spherical.

National Category
Materials Engineering
Identifiers
urn:nbn:se:hj:diva-41983 (URN)
Patent
EPO (European Patent Office) EP3356782 (2018-08-08)
Available from: 2018-11-06 Created: 2018-11-06 Last updated: 2018-11-06
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
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3024-9005

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