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1.	Diószegi, Attila, 1962-, et al. (författare) Defect formation mechanisms in lamellar cast iron related to the casting geometry 2015 Ingår i: Advances in the science and engineering of casting solidification. - Hoboken, NJ : John Wiley & Sons. - 9781119082385 - 9781119093367 ; , s. 251-259 Konferensbidrag (refereegranskat)abstract Although lamellar cast iron has been used in advanced applications for about twenty years, our knowledge about the mechanisms affecting microstructure and defect formation is relatively limited. The present paper summarizes some solidification related phenomena from a series of recently published peer reviewed papers and scientific theses and suggests a mechanism of defect formation which is dependent on the shape of the solidifying casting geometry. When shrinkage porosity or metal expansion penetration occurs evidence of material transport in the intergranular zone of primary equiaxed austenite grains in the casting and in the intergranular regions between the sand grains in the mold material is seen. Material transport occurs across the casting-mold interface where the existence of or the permeability of the primary columnar zone determines if material transport can take place.
2.	Diószegi, Attila, 1962-, et al. (författare) Modelling and simulation of heat conduction in 1-D polar spherical coordinates using control volume-based finite difference method 2016 Ingår i: International journal of numerical methods for heat & fluid flow. - 0961-5539 .- 1758-6585. ; 26:1, s. 2-17 Tidskriftsartikel (refereegranskat)abstract Purpose - The purpose of this paper is to obtain a finite difference method (FDM) solution using control volume for heat transport by conduction and the heat absorption by the enthalpy model in the sand mixture used in casting manufacturing processes. A mixture of sand and different chemicals (binders) is used as moulding materials in the casting processes. The presence of various compounds in the system improve the complexity of the heat transport due to the heat absorption as the binders are decomposing and transformed into gaseous products due to significant heat shock. Design/methodology/approach - The geometrical domain were defined in a 1D polar coordinate system and adapted for numerical simulation according to the control volume-based FDM. The simulation results were validated by comparison to the temperature measurements under laboratory conditions as the sand mould mixture was heated by interacting with a liquid alloy. Findings - Results of validation and simulation methods were about high correspondence, the numerical method presented in this paper is accurate and has significant potential in the simulation of casting processes. Originality/value - Both numerical solution (definition of geometrical domain in 1D polar coordinate system) and verification method presented in this paper are state-of-the-art in their kinds and present high scientific value especially regarding to the topic of numerical modelling of heat flow and foundry technology.
3.	Diószegi, Attila, 1962-, et al. (författare) Shrinkage porosity formation in cast iron components 2018 Ingår i: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings. - : Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association. - 9788390430638 ; , s. 207-208 Konferensbidrag (refereegranskat)abstract Shrinkage porosity formation mechanisms at production of cast iron components is particularly complex and became more and more difficult to understand since the shape casting complexity have been increased more and more in advanced component applications. The present work intends to summarize the state of the art in understanding the shrinkage porosity formation mechanism of cast iron based on a series of key publications, MSc and PhD theses performed in collaboration between cast iron component users, producers and researchers.
4.	Advances in the science and engineering of casting solidification : An MPMD symposium honoring Doru Michael Stefanescu 2015 Proceedings (redaktörskap) (refereegranskat)
5.	Diószegi, Attila, 1962-, et al. (författare) Austenite dendrite morphology in lamellar graphite iron 2015 Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 28:5, s. 310-317 Tidskriftsartikel (refereegranskat)abstract Primary austenite has been underestimated in general when the theories of nucleation, solidification, microstructure formation and mechanical properties were established for cast iron and particularly for lamellar cast iron. The present work aims to investigate the primary austenite morphology of as cast samples of a hypoeutectic lamellar cast iron produced with different cooling rates. Morphological parameters as the area fraction primary austenite, the secondary dendrite arm spacing, the dendrite envelope surface, the coarseness of the primary dendrite expressed as the relation between the volume of the dendrite and its envelope surface and the coarseness of the interdendritic space also known as the hydraulic diameter are measured. Furthermore, the role of the size of the investigation area is revealed to be sequential investigation. A strong relation between all measured morphological parameters and the solidification time has been established, except the volume fraction of primary austenite, which is constant for all cooling conditions.
6.	Diószegi, Attila, et al. (författare) Defect formation mechanisms in lamellar graphite iron related to the casting geometry 2016 Ingår i: International Journal of Cast Metals Research. - : Taylor & Francis. - 1364-0461 .- 1743-1336. ; 29:5, s. 279-285 Tidskriftsartikel (refereegranskat)abstract Although lamellar cast iron has been used in advanced applications for about 20 years, our knowledge about the mechanisms affecting microstructure and defect formation is relatively limited. The present paper summarises some solidification-related phenomena from a series of recently published peer-reviewed papers and scientific theses and suggests a mechanism of defect formation which is dependent on the shape of the solidifying casting geometry. When shrinkage porosity or metal expansion penetration occurs, evidence of material transport in the intergranular zone of primary equiaxed austenite grains in the casting and in the intergranular regions between the sand grains in the mould material is seen. Material transport occurs across the casting-mould interface, where the existence of or the permeability of the primary columnar zone determines if material transport can take place.
7.	Diószegi, Attila, 1962-, et al. (författare) Method of and device for analysing a phase transformation of a material 2018 Patent (populärvet., debatt m.m.)abstract 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.
8.	Diószegi, Attila, 1962-, et al. (författare) Microstructures and Characterization of Gray Irons 2017 Ingår i: ASM Handbook, Volume 1A. - Materials Park, Ohio : ASM International. - 9781627081337 - 162708133X - 9781627081344 ; , s. 583-589 Bokkapitel (refereegranskat)
9.	Diószegi, Attila, 1962-, et al. (författare) Prediction of volume fraction of primary austenite at solidification of lamellar graphite cast iron using thermal analyses 2016 Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Netherlands. - 1388-6150 .- 1588-2926. ; 124:1, s. 215-225 Tidskriftsartikel (refereegranskat)abstract Lamellar graphite cast iron was investigated with carbon equivalents varied between CE = 3.4 and 4.26, cast at various cooling rates between 0.195 and 3.5 °C s-1 covering the limits used for technical applications in the production of complex-shaped lamellar graphite cast iron. Registered cooling curves displaced in two positions in the casting were used to predict the solidification and microstructure formation mechanisms. The predicted volume fraction of primary austenite was compared with the fraction of primary austenite measured on colour micrographs with the help of image analyses. A good correlation has been obtained for medium and slow cooling conditions, while a less good correlation at fast cooling condition was attributed to the used protective environment to preserve thermocouples. The observed fraction and the predicted fraction of primary austenite were in good correlation and followed a consequent variation dependent on the carbon equivalent. Furthermore, the quality of the prediction was dependent on the used numerical algorithm involving cooling information from either one or two thermocouples.
10.	Diószegi, Attila, 1962-, et al. (författare) Volumetric changes during the Solidification of Cast Iron 2017 Ingår i: ASM Handbook, Volume 1A. - Materials Park, Ohio : ASM International. - 9781627081337 - 162708133X - 9781627081344 ; , s. 88-93 Bokkapitel (refereegranskat)
11.	Domeij, Björn, 1988- (författare) Compacted graphite iron : On solidification phenomena related to shrinkage defects 2019 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract An improved understanding of solidification of compacted graphite iron (CGI) is necessary to predict shrinkage related casting defects. Spheroidal graphite is not only found in ductile iron (SGI) but usually also in CGI, but its characteristics and role in this material is less understood. Uncertainties also remain regarding the segregation of alloying elements in cast irons. This is important because of its important role in the solidification process. The dendritic austenite structure has received little attention in cast iron research. A good understanding of the development of this structure is important to understand feeding of melt through the solidifying material.Nodularity is a measure of the amount of spheroidal versus compacted graphite in the microstructure. At a lower nodularity, the compacted graphite tips were found to grow in contact with the melt for a longer time before being encapsulated in the austenite. Moreover, as the nodularity was reduced, the subpopulation of larger spheroidal graphite gradually disappeared, reducing the bimodal size distribution to unimodal.Segregation of Si, Mn and Cu in SGI and CGI with a solidification time of near 10 min was found to be rather predictable under assumptions of no diffusion in austenite and complete mixing in the melt. Gradients of these elements contribute to a decrease in the driving force for diffusion of carbon into the austenite from the liquid, which is important for the growth of graphite which is separated from the liquid by austenite.During solidification of a near-eutectic CGI, the carbon concentration of austenite was found to deviate considerably from local equilibrium with graphite during solidification. This is important to consider in growth models for graphite by diffusion of carbon through a barrier of austenite.Micropores were shown to have displaced liquid from the solid structure at a late stage of solidification when solidification was slowing down and the temperature of the casting was falling at an increasing rate.The development of dendritic austenite in a near eutectic CGI was investigated. The contact area between liquid and the dendritic structure exceeded the contact area between liquid and eutectic cells through the dominant part of solidification. This highlights the importance of good understanding of the development of this structure in order to predict feeding of melt through the solidifying material. The coarsening of the structure was found to proceed at a higher rate compared to studies under isothermal condition. The dendritic structure continued to grow in parallel with the eutectic by a combination of thickening and dendritic growth.
12.	Domeij, Björn, 1988- (författare) On the solidification of compacted and spheroidal graphite irons 2017 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract A good understanding of the solidification process of a cast material is essential to understand how the combination of alloy composition and the casting process variables combines into the solid cast component and its performance. The wrong combination may result in poor performance or casting defects. Spheroidal graphite has been well researched in ductile irons (SGI) where it is predominant. Spheroidal graphite is also present in smaller amounts in compacted graphite irons (CGI), but its nature and role in this material is less understood. Recent associations of spheroidal graphite in CGI with shrinkage porosity problems highlights the need for better understanding in this area. The importance of the dendritic austenite structure to the properties and solidification behaviour of cast irons has been highlighted in recent research. However, progress is to a degree limited by lack of practical means to characterize the structure.In the present work, the transition of a cast iron from SGI to CGI though remelting was studied. As the fraction of SG dropped, the tips of the compacted graphite tended to lose contact with the melt at a later stage. After this occurred, solidification appeared to be dominated by spheroidal graphite. Compacted and spheroidal graphite was found to solidify mostly segregated, and the increased recallescence induced by a higher fraction of compacted graphite displayed small influence on the size distribution of spheroidal graphite apart from the total number and fraction. The partitioning of Si, Mn and Cu in SGI and CGI was found to agree well with each other, as well as with theoretical predictions under the assumptions of zero diffusion of the elements in the solid. This shows that the proportions of spheroidal and compacted graphite has small or no influence on the evolution of these elements in the melt during solidification. A method for characterization of the dendritic austenite in quenched cast irons was introduced and evaluated. The method includes a technique for producing a visual contrast between the ledeburite matrix and the dendritic austenite, and a scheme for producing binary images from the resulting micrographs which are suitable for automatic image analysis. Measurements of the volume fraction and surface area per unit volume of the dendritic austenite structure using the introduced method was found to agree reasonably with traditional point counting and line intercept techniques. The difficulty in finding the exact boundary was proposed to be the major source of systematic disagreement.
13.	Domeij, Björn, 1988-, et al. (författare) Solidification Chronology of the Metal Matrix and a Study of Conditions for Micropore Formation in Cast Irons Using EPMA and FTA 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 436-443 Tidskriftsartikel (refereegranskat)abstract 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.
14.	Ekengård, Johan, 1976-, et al. (författare) A STUDY OF OXYGEN ACTIVITIES BEFORE THE START OF SOLIDIFICATION OF CAST IRONS 2016 Ingår i: International Journal of metalcasting. - : Springer Science and Business Media LLC. - 1939-5981 .- 2163-3193. ; 10:4 Tidskriftsartikel (refereegranskat)abstract Focus in this work was to study dissolved oxygen content and oxygen activities in different cast irons. Plant trials were performed at three occasions for lamellar, compacted and nodular iron melts. The results show that at temperatures close to the liquidus temperature the oxygen activities ranged from 0.03-0.1 ppm for LGI, around 0.02 ppm for CGI and 0.001ppm for SGI. In addition, it was found that as oxygen activities increase with time after an Mg treatment, the ability to form compacted graphite or nodular graphite in Mg-treated iron melts was lowered. Also, oxygen activity differences up to 0.07 ppm were found for different hypoeutectic iron compositions for lamellar graphite iron at the liquidus temperature. Overall, the observed differences in the dissolved oxygen levels are believed to influence how graphite particles are incorporated into the austenite matrix and how the graphite morphology will be in the cast product.
15.	Fourlakidis, Vasilios (författare) Dendritic morphology and ultimate tensile strength of pearlitic lamellar graphite iron 2019 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract The continued development, of cylinder blocks and cylinder heads for heavy truck engines that are made of lamellar graphite iron (LGI) is focused on achieving high ultimate tensile strength (UTS) whilst conforming to environmental regulations. The purpose of this work is to further improve the tensile strength as well as the predictive engineering tools for optimization of LGI aimed to enhance the efforts for producing lighter and sustainable components without sacrificing performance.Varying the carbon content and solidification rate greatly influences the amount and the coarseness of the microstructure phases resulting in large variations of material properties. The experimental data set provided in this work covers a comprehensive range of microstructure and the UTS values aimed to be used in a holistic model for UTS prediction.In pearlitic LGI the primary austenite dendritic network reinforces the material while the distance between the pearlite grains defines the maximum continuous defect size. The novel parameter of Hydraulic Diameter of the Inter-dendritic Phase (DIPHyd) has been introduced in this work to express the amount and the coarseness of the space between the pearlite grains that have been solidified as primary austenite dendrites. The DIPHyd has proven to be the generic parameter that defines the maximum continuous defect size in the material, and hence it has been applied in modified Griffith and Hall-Petch models for prediction of UTS.Microstructure models have been developed for prediction of the key microstructure parameters that define the strength of LGI. These models have been combined with the modified Griffith and Hall-Petch equations and incorporated into casting simulation software to enable the strength prediction for pearlitic LGI alloys with various carbon contents. The results show that the developed models can be successfully applied, along with the simulation tools across a wide range of carbon content from eutectic to hypoeutectic composition, for the alloys solidified at various cooling rates typical for both thin and thick walled complex shaped iron castings.
16.	Fourlakidis, Vasilios, et al. (författare) Strength prediction for pearlitic lamellar graphite iron : Model validation 2018 Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 8:9 Tidskriftsartikel (refereegranskat)abstract The present work provides validation of the ultimate tensile strength computational models, based on full-scale lamellar graphite iron casting process simulation, against previously obtained experimental data. Microstructure models have been combined with modified Griffith and Hall–Petch equations, and incorporated into casting simulation software, to enable the strength prediction for four pearlitic lamellar cast iron alloys with various carbon contents. The results show that the developed models can be successfully applied within the strength prediction methodology along with the simulation tools, for a wide range of carbon contents and for different solidification rates typical for both thin-and thick-walled complex-shaped iron castings.
17.	Fourlakidis, Vasilios, et al. (författare) Strength prediction of lamellar graphite iron : From Griffith’s to hall-petch modified equation 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; , s. 272-279 Konferensbidrag (refereegranskat)abstract 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.
18.	Ghasemi, Rohollah, 1983-, et al. (författare) Austempered compacted graphite iron — Influence of austempering temperature and time on microstructural and mechanical properties 2019 Ingår i: Materials Science & Engineering. - : Elsevier. - 0921-5093 .- 1873-4936. ; 767 Tidskriftsartikel (refereegranskat)abstract 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.
19.	Ghassemali, Ehsan, 1983-, et al. (författare) On the Formation of Micro-Shrinkage Porosities in Ductile Iron Cast Components 2018 Ingår i: Metals. - : MDPI. - 2075-4701. ; 8:7 Tidskriftsartikel (refereegranskat)abstract 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.
20.	Ghassemali, Ehsan, 1983-, et al. (författare) Revisiting the graphite nodule in ductile iron 2019 Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 161, s. 66-69 Tidskriftsartikel (refereegranskat)abstract 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.
21.	Hellström, Kristina, et al. (författare) A broad literature review of density measurements of liquid cast iron 2017 Ingår i: Metals. - : MDPI. - 2075-4701. ; 7:5 Forskningsöversikt (refereegranskat)abstract The literature on density measurements, with a particular interest in methods suitable for liquid cast iron, is reviewed. Different measurement methods based on a number of physical properties are highlighted and compared. Methods for the calculation of density are also reviewed, and the influence of alloying elements on density is, to some extent, discussed. The topic is of essence for the understanding of the material behaviour at solidification, which is pivotal in software applications for casting simulation. Since a deeper understanding of the relationship between the density of liquid cast iron and volume expansion is necessary, the conclusion that further research within the field is needed lies close at hand.
22.	Hellström, Kristina, et al. (författare) Density variations during solidification of grey cast Iron 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; , s. 155-162 Tidskriftsartikel (refereegranskat)abstract 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.
23.	Hellström, Kristina (författare) Density variations during solidification of lamellar graphite iron 2017 Licentiatavhandling (övrigt vetenskapligt/konstnärligt)
24.	Hernando, Juan Carlos, et al. (författare) An overview of isothermal coarsening in hypoeutectic lamellar cast iron 2016 Ingår i: Advances in the science and engineering of casting solidification. - Cham : Springer. - 9783319486055 - 9783319481173 ; , s. 295-302 Konferensbidrag (refereegranskat)abstract A complete qualitative characterization of the isothermal coarsening process in hypoeutectic lamellar cast iron is presented for the first time in this work. Interrupted solidification experiments were used to study the evolution of the dendritic austenite network under long term isothermal conditions. Cylindrical samples were re-melted and isothermally coarsened for times from 2 minutes to 6 days at 1175°C after dendritic coherence was reached. Micrographs from horizontal and vertical sections of the coarsened samples are presented. Complete fragmentation of the dendrite network and further rearrangement of the solid phase are reported as new behaviors in the coarsening process in lamellar cast iron. A linear increase in secondary dendrite arm spacing in agreement with the literature is observed in the first several samples confirming qualitative observations. A new model is proposed which describes the entire coarsening process observed in this investigation.
25.	Hernando, Juan Carlos, et al. (författare) An overview of isothermal coarsening in hypoeutectic lamellar cast iron 2015 Ingår i: Advances in the science and engineering of casting solidification. - Hoboken, New Jersey : John Wiley & Sons. - 9781119082385 - 9781119093367 ; , s. 295-302 Konferensbidrag (refereegranskat)abstract A complete qualitative characterization of the isothermal coarsening process in hypoeutectic lamellar cast iron is presented for the first time in this work. Interrupted solidification experiments were used to study the evolution of the dendritic austenite network under long term isothermal conditions. Cylindrical samples were re-melted and isothermally coarsened for times from 2 minutes to 6 days at 1175°C after dendritic coherence was reached. Micrographs from horizontal and vertical sections of the coarsened samples are presented. Complete fragmentation of the dendrite network and further rearrangement of the solid phase are reported as new behaviors in the coarsening process in lamellar cast iron. A linear increase in secondary dendrite arm spacing in agreement with the literature is observed in the first several samples confirming qualitative observations. A new model is proposed which describes the entire coarsening process observed in this investigation.
26.	Hernando, Juan Carlos, et al. (författare) Evolution of primary austenite during coarsening and impact on eutectic microstructure in Fe–C–Si alloys 2019 Ingår i: Materialia. - : Elsevier. - 2589-1529. ; 7 Tidskriftsartikel (refereegranskat)abstract 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.
27.	Hernando, Juan Carlos, et al. (författare) On the primary solidification of compacted graphite iron : Microstructure evolution during isothermal coarsening 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. ; 925, s. 90-97 Tidskriftsartikel (refereegranskat)abstract 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.
28.	Hernando, Juan Carlos, et al. (författare) The effect of coarsening of primary austenite on the ultimate tensile strength of hypoeutectic compacted graphite Fe-C-Si alloys 2019 Ingår i: Scripta Materialia. - : Elsevier. - 1359-6462 .- 1872-8456. ; 168, s. 33-37 Tidskriftsartikel (refereegranskat)abstract 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.
29.	Hernando, Juan Carlos, et al. (författare) The morphological evolution of primary austenite during isothermal coarsening 2017 Ingår i: Materials Characterization. - : Elsevier. - 1044-5803 .- 1873-4189. ; 131, s. 492-499 Tidskriftsartikel (refereegranskat)abstract The morphological evolution of primary austenite in an industrial hypoeutectic lamellar cast iron was studied under isothermal conditions for coarsening times varying from 0 min to 96 h. The dendritic austenite structure formed during the primary solidification suffered major morphological changes during the isothermal coarsening process. After a sufficient coarsening time, dendrite fragmentation, globularization, and coalescence of austenite were studied using electron backscatter diffraction (EBSD) technique. This study confirmed that the secondary dendrite arm spacing (SDAS) is an inappropriate length scale to describe the primary austenite coarsening process for longer times. The application of shape independent quantitative parameters confirmed the reduction of the total interfacial area during microstructural coarsening. The modulus of the primary austenite, Mγ, which represents the volume-surface ratio for the austenite phase, and the spatial distribution of the austenite particles, measured as the nearest distance between the center of gravity of neighboring particles, Dγ, followed a linear relation with the cube root of coarsening time during the whole coarsening process. The mean curvature of the austenite interface, characterized through stereological relations, showed a linear relation to Mγ and Dγ, allowing the quantitative characterization and modeling of the complete coarsening process of primary austenite.
30.	Hernando, Juan Carlos (författare) The role of primary austenite morphology in cast iron 2019 Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract Automotive industry products portfolio includes a wide variety of complex-shaped cast iron products, such as truck engine components. Urged by strict environmental regulations on emissions, these components constantly need to combine higher demands on performance with lighter designs. As a result, cast iron industry continuously faces new challenges related to solidification of new alloys, component designs and casting processes.Complex shapes, variations in the thickness of the casting and the molding material strongly influence the solidification time for a component, thus varying its microstructural coarseness and hence showing different properties depending on the local shape of the casting.This work increases our understanding of the morphological evolution of primary austenite occurring during isothermal coarsening at the semi-solid state. New experimental techniques have been developed to show that primary austenite coarsens according to the Ostwald ripening model in lamellar (LGI), compacted (CGI)and spheroidal (SGI) graphite iron. Significant morphological changes occur after long coarsening times, including dendrite fragmentation and coalescence. The quantitative characterization of the morphological changes during coarsening is accurately described by morphological parameters, i.e., Mγ, DIDHyd and DγNN.Subsequently, the impact of primary austenite morphology on the eutectic microstructures in CGI and SGI has been investigated. It was observed that the eutectic microstructures 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 as a function of coarsening time. These results suggest that the nucleation frequency and growth of eutectic microstructures are not significantly influenced by the morphology of primary austenite.Furthermore, miniaturized tensile tests demonstrated that the UTS in CGI is directly related to the primary austenite morphology. The UTS decreases with the increasing coarseness of primary austenite, showing an inverse linear relation to Mγ, DIDHyd and DγNN. These results demonstrate the strong impact of primary austenite morphology on UTS when the eutectic and eutectoid microstructures are similar, emphasizing the importance of incorporating the morphology of primary austenite in our models.
31.	Lidumnieks, Kriss, et al. (författare) The effect of various production parameters on the heat absorbing capacity of greensand 2018 Ingår i: International Journal of Cast Metals Research. - : Maney Publishing. - 1364-0461 .- 1743-1336. ; 31:1, s. 7-13 Tidskriftsartikel (refereegranskat)abstract 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.
32.	Orlenius, Jessica, et al. (författare) Mould and core gas evolution in grey iron castings 2015 Ingår i: International Foundry Research. - 0046-5933. ; 67:4, s. 10-20 Tidskriftsartikel (refereegranskat)abstract The volume and rate of gas evolution from cores prepared with various binders and sand has been determined with a new commercial technique. Spherical cores were mounted on a glass tube and immersed into molten grey iron. The gas generated by decomposition of the binder was determined by displacement of water in a measuring tube placed on a balance. The gas evolution from PUCB, epoxy and sodium silicate cores changes insignificantly during the first week after production. Neither influences iron temperature the amount of evolved gas to a large extent. Different binders evolve different amount of gas, but also the sand type affects the gas evolution. The impact of additives on the gas evolution is dependent on the amount of organic compounds in the additive. Coatings increase the total gas volume, while the maximal rate is not necessarily affected. Dried green sand evolves more gas than chemical bonded sand.
33.	Science and Processing of Cast Iron XI 2018 Proceedings (redaktörskap) (refereegranskat)abstract 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.
34.	Svidró, Judit, et al. (författare) New possibilities in the thermal analysis of moulding materials 2018 Ingår i: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings. - : Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association. - 9788390430638 ; , s. 25-26 Konferensbidrag (refereegranskat)abstract Moulding material related studies within research activities concerning foundry technology have always been limited, despite the significant effect of moulding mixtures on the quality of cast parts. One reason behind this trend is the difficulty in interpreting results of such complex systems like moulds and cores. This paper provides a new possibility to study the heat absorption performance of materials used as moulding media in metal casting processes. By further developing the Fourier thermal analysis method of cores and moulds introduced by earlier authors, the investigation of unbonded sand has become available. Heat absorption properties of the components can be hereby separated and studied respectively. Thermal analyses were performed on sphere shaped, resin bonded cores with various binder levels and on unbonded sand samples. The temperature data collected in two points of the samples were then used for the calculation of novel thermophysical properties. The results revealed not only quantitative but qualitative differences in the characteristics of binder decomposition processes, providing deeper understanding on the thermal behavior of moulding materials. The outcome of the research provides more accurate data, which is the key for improved simulation of casting processes.
35.	Svidró, Judit, et al. (författare) New possibilities in thermal analysis of molding materials 2018 Ingår i: Journal of Casting & Materials Engineering. - Krakow : AGH University of Science and Technology. - 2543-9901. ; 2:4, s. 67-70 Tidskriftsartikel (refereegranskat)abstract Molding material-related studies within the research activities concerning foundry technology have always been limited despite the significant effect of molding mixtures on the quality of cast parts. One reason behind this trend is the difficulty in interpreting the results of such complex systems like molds and cores. This paper provides a new possibility for studying the heat-absorption performance of materials used as molding media in metal casting processes. By further developing the Fourier thermal analysis method of cores and molds introduced by earlier authors, the investigation of unbonded sand has become available. The heat-absorption properties of the components can be hereby separated and studied respectively. Thermal analyses were performed on sphere-shaped resin-bonded cores with various binder levels as well as on unbonded sand samples. The temperature data collected from two points of the samples were then used for the calculation of the novel thermophysical properties. The results revealed not only quantitative but qualitative differences in the characteristics of the binder decomposition processes, providing a deeper understanding on the thermal behavior of molding materials. The outcome of the research provides more-accurate data, which is the key for the improved simulation of casting processes.
36.	Svidró, József Tamás, 1984-, et al. (författare) A novel measurement method to study the thermal aspects of moulding mixture decomposition 2018 Ingår i: 73rd World Foundry Congress "Creative Foundry", WFC 2018 - Proceedings. - : Stowarzyszenie Techniczne Odlewnikow Polskich/Polish Foundrymen's Association. - 9788390430638 ; , s. 113-114 Konferensbidrag (refereegranskat)abstract 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.
37.	Svidró, József Tamás, 1984-, et al. (författare) Novel Measurement Method to Study Thermal Aspects of Molding Mixture Decomposition 2018 Ingår i: Journal of Casting & Materials Engineering. - : AGH University of Science and Technology Press. - 2543-9901. ; 2:3, s. 63-66 Tidskriftsartikel (refereegranskat)abstract 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.
38.	Svidró, József Tamás, 1984-, et al. (författare) The effect of different binder levels on the heat absorption capacity of moulding mixtures made by the phenolic urethane cold-box process 2017 Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 130:3, s. 1769-1777 Tidskriftsartikel (refereegranskat)abstract The phenolic urethane cold-box (PUCB) process was first introduced to the foundry industry in the late 1960s. Since then, it has become one of the most popular methods to make foundry purpose sand moulds and cores, utilized in the manufacturing of aluminium and cast iron cast components. The factors to be considered, affecting the general performance of a PUCB moulding mixture, are the temperature of sand, the moisture content, the mixing conditions, etc. Moreover, there are variable production parameters such as binder level, to improve certain properties of the mould and/or the core based on their specific area of application. These are mainly mechanical properties such as tensile or splitting strength. They have significant influences on the behaviour of the moulding material and are usually tested at room temperature. Although the production phases of the PUCB system are refined to a high extent today, the effect of binder content on the quality of the mould/core and the final casting should be supported by new approaches also in thermal sciences, interpreted in high-temperature environment. In this work, different PUCB mixtures were produced to evaluate the effect of various binder levels on the thermophysical properties of sand cores. Thermogravimetry, differential thermal analysis and a novel application of Fourier thermal analysis were used to study the decomposition processes of the PUCB mixture and to reveal the impact of binder level on the heat absorption (cooling) capacity of sand cores at temperatures relevant in the manufacturing of cast iron parts (1300 ± 10 °C).
39.	Svidró, József Tamás, 1984-, et al. (författare) Thermophysical aspects of reclaimed moulding sand addition to the epoxy-SO2 coremaking system studied by Fourier thermal analysis 2017 Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer. - 1388-6150 .- 1588-2926. ; 130:3, s. 1779-1789 Tidskriftsartikel (refereegranskat)abstract The most important advantage of foundry purpose moulding sand is that it can be reclaimed and reused through the casting manufacturing process. Supplying the foundry with a new source of material, sand reclamation brings along both environmental and economic advantages. Utilization of used sand can be considered as a common technological routine in the production of most types of chemically bound moulding materials. The epoxy-SO2 process is prevalent in the processing of cast iron engine components worldwide. Based on its excellent properties, it is mainly suitable for producing internal sand cores with complex geometry. Even though reclaimed sand addition is an active and well-functioning feature in ferrous foundries, the scientific and thermophysical background of its effects on the casting process is yet to be explored. In this work, the thermal aspects of different reclaimed sand levels in the epoxy-SO2 moulding system were examined. Thermogravimetry and differential thermal analysis of the epoxy-SO2 and reclaimed sand in focus were carried out to obtain basic understandings about their high-temperature behaviour. A state-of-the-art Fourier thermal analysis method presented in a recent paper was used at temperatures corresponding to actual cast iron production (1300 ± 10 °C), contrary to the previous tests at the typical temperature range of aluminium melt processing (660 ± 10 °C). By the right of the method, the effects of reclaimed sand addition on the heat absorption (cooling) capacity of the epoxy-SO2 moulding mixtures were investigated.
40.	Svidró, Judit, et al. (författare) The influence of thermal expansion of unbonded foundry sands on the deformation of resin bonded cores 2017 Ingår i: Archives of Metallurgy and Materials. - : De Gruyter Open. - 1733-3490 .- 2300-1909. ; 62:2, s. 795-798 Tidskriftsartikel (refereegranskat)abstract Depending on the preparation and the applied materials, moulds and cores can be of high rigidity or can be flexible. Although, chemically bonded moulding materials have relatively good flexibility, their high temperature behaviour determines the dimensional accuracy, the stresses in the castings and can induce several casting defects, such as rattail, veining, etc. The phenomenon is based on two major effects: the thermal expansion of the unbonded foundry sands and the deformation of the sand mixtures. The main objective of the present work was to study the relationship between these two effects, and to improve the knowledge related to the thermo-mechanical interactions between the casting and the mould. Dilatometric analysis of unbonded sand samples were performed and compared to the results of hot distortion tests of moulding mixture specimens. The results showed, that the thermal expansion of foundry sand largely influences the hot distortion behaviour, but depending on the type of binder used.
41.	Svidró, Péter, 1980-, et al. (författare) Determination of pressure in the extradendritic liquid area during solidification 2018 Ingår i: Journal of thermal analysis and calorimetry (Print). - : Springer Netherlands. - 1388-6150 .- 1588-2926. ; 132:3, s. 1661-1667 Tidskriftsartikel (refereegranskat)abstract 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.
42.	Svidró, Péter, 1980-, et al. (författare) Extended method of volume change measurements during solidification of lamellar graphite iron 2018 Ingår i: Materials Science Forum. - : Trans Tech Publications. - 0255-5476 .- 1662-9752. - 9783035710557 ; 925, s. 163-170 Tidskriftsartikel (refereegranskat)abstract 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.
43.	Svidró, Péter, 1980-, et al. (författare) Investigation of dendrite coarsening in complex shaped lamellar graphite iron castings 2017 Ingår i: Metals. - : MDPI. - 2075-4701. ; 7:7 Tidskriftsartikel (refereegranskat)abstract Shrinkage porosity and metal expansion penetration are two casting defects that appear frequently during the production of complex-shaped lamellar graphite iron components. These casting defects are formed during the solidification and usually form in the part of the casting which solidifies last. The position of the area that solidifies last is dependent on the thermal conditions. Test castings with thermal conditions like those existing in a complex-shaped casting were successfully applied to provoke a shrinkage porosity defect and a metal expansion penetration defect. The investigation of the primary dendrite morphology in the defected positions indicates a maximum intradendritic space, where the shrinkage porosity and metal expansion penetration defects appear. Moving away from the defect formation area, the intradendritic space decreases. A comparison of the intradendritic space with the simulated local solidification times indicates a strong relationship, which can be explained by the dynamic coarsening process. More specifically, long local solidification times facilitates the formation of a locally coarsened austenite morphology. This, in turn, enables the formation of a shrinkage porosity or a metal expansion penetration.
44.	Svidró, Péter, 1980-, et al. (författare) Sampling device and method for sampling a liquid or viscous material 2018 Patent (populärvet., debatt m.m.)abstract 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.

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