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  • 1.
    Adolfi, Sofia
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Lagerstedt, Anders
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Sarnet, Jan
    Scana Steel Björneborg AB.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Macrosegregation In Ingot Cast Tool Steel2004Rapport (Övrigt vetenskapligt)
  • 2.
    Adolfi, Sofia
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Mori, Kenji
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    MnS precipitation during solidification in presence of oxide nuclei2007Konferensbidrag (Övrigt vetenskapligt)
  • 3.
    Aghasibeig, Maniya
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Laser cladding of a featureless iron-based alloy2012Ingår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 209, s. 32-37Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Laser cladding experiments with powder injection technique were carried out to create coatings of Fe-8.1Cr6.4Mn-5.3Si-6.9Mo-3.6C alloy on AISI 1018 steel substrates using a diode laser. Analysis of the clad layers showed that an almost featureless structure was formed at different dilutions between 1% and 4%. The featureless phase with a high hardness of 1155 HV was characterized as a metastable solid solution of e phase. However, the featureless structure appeared to be very brittle with numerous cracks. After heat-treatment, it decomposed into a bainitic structure with a high hardness of 884 HV.

  • 4. Antonsson, T.
    et al.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    The effect of cooling rate on the solidification of INCONEL 7182005Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 36, nr 1, s. 85-96Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The superalloy INCONEL 718 (IN718) is a commonly used material in aerospace and turbine components. The advantage of this type of material with sluggish precipitation-hardening kinetics is that IN718 is readily weldable. Both wrought and cast parts are used and welded together. While the alloy has been studied previously, new production processes such as laser treatment demand better knowledge of the solidification process in IN718. especially at high cooling rates. In this investigation. the solidification process was studied over a wide range of cooling rated by three different experimental techniques: differential thermal analysis (DTA), mirror furnace (MF), and levitation casting. The solidification sequence and the reaction temperatures were identified. The microstructure and the change in growth morphology were also studied. Segregation measurements were performed, and the distribution of Nb was analyzed in detail for the different types of samples. because of its strong impact on the solidification sequence and microstructure. New observations are that the latent heat decreases and the effective partition coefficient increases with increasing cooling rate. The diffusion rate also seems to be enhanced in the first part of primary solidified dendrites. It is suggested that the new observations can be explained by an increased number of lattice defects formed in the solid as the cooling rate increases.

  • 5.
    Antonsson, Tomas
    et al.
    KTH, Tidigare Institutioner, Metallernas gjutning.
    Ekbom, Lars B.
    KTH, Tidigare Institutioner, Metallernas gjutning.
    Eliasson, Anders
    KTH, Tidigare Institutioner, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner, Metallernas gjutning.
    Liquid Ni-Fe penetration and recrystallisation in tungsten2003Ingår i: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 21, nr 3-4, s. 159-170Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Melt penetration in grain boundaries of solid tungsten has been investigated. Solid tungsten rods have been exposed to a nickel-iron melt saturated with tungsten and the penetration depth and the shape of the liquid channels have been examined. The solid tungsten samples have been treated in different ways like cold working, annealing and recrystallisation, before melt exposure. Important parameters for the penetration process are stresses, surface tensions, solution and kinetic effects. A new theoretical model for the penetration mechanism in cold worked samples is proposed. Rapid recovery of the grains in the penetrated areas of the cold worked samples was observed. This is discussed, as well.

  • 6. Arai, Y.
    et al.
    Emi, Toshihiko
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Shibata, H.
    In-situ observed dynamics of peritectic solidification and delta/gamma transformation of Fe-3 to 5 At. Pct Ni alloys2005Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 36A, nr 11, s. 3065-3074Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The characteristics of liquid -> delta ferrite and delta ferrite -> gamma austenite transformation in Fe-3.50 at. pct Ni alloy, and of the peritectic solidification of Fe-4.83 and 5.01 at. pct Ni alloys, have been dynamically observed in situ with a confocal scanning laser microscope (CSLM) combined with an infrared image furnace (IIF). The unique sequence, morphologies, and rates of these transformations have been determined at a temperature gradient of 4 K/mm and growth rates of 2 to 3 mu m/s, in unidirectional solidification experiments. These observations have been discussed in terms of the constitutional undercooling description of solidification theory.

  • 7. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Analysis of phase diagram and diffusion coefficient for modeling of microsegregation2017Ingår i: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 52, nr 3, s. 1446-1460Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Thermodynamic description of phase diagram and diffusion data are required to model microsegregation during solidification of metallic alloys. Knowledge about non-equilibrium phase diagrams is essential for modeling of microsegregation in practical situations. Therefore, the aim of this study is to theoretically analyze phase diagram and diffusion data for calculation of microsegregation. For this purpose, aluminum-rich part of the Al-Cu phase diagram was recalculated under non-equilibrium conditions. Effect of excess vacancies formed during solidification was considered on both the phase diagram and diffusion coefficient. The results show that by modifying the phase diagram, the calculated results have better consistency with the experimental results, but there is still room for improvement. When the effect of excess vacancies on diffusion coefficient is considered, the modeling results show a much better correlation with the experimental results. The origin of discrepancies between the calculations and experiments are deeply discussed using current theories in solidification.

  • 8. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Effect of partition coefficient on microsegregation during solidification of aluminium alloys2014Ingår i: International Journal of Minerals, Metallurgy and Materials, ISSN 1674-4799, E-ISSN 1869-103X, Vol. 21, nr 10, s. 980-989Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the modeling of microsegregation, the partition coefficient is usually calculated using data from the equilibrium phase diagrams. The aim of this study was to experimentally and theoretically analyze the partition coefficient in binary aluminum-copper alloys. The samples were analyzed by differential thermal analysis (DTA), which were melted and quenched from different temperatures during solidification. The mass fraction and composition of phases were measured by image processing and scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectroscopy (EDS) unit. These data were used to calculate as the experimental partition coefficients with four different methods. The experimental and equilibrium partition coefficients were used to model the concentration profile in the primary phase. The modeling results show that the profiles calculated by the experimental partition coefficients are more consistent with the experimental profiles, compared to those calculated using the equilibrium partition coefficients.

  • 9. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Experimental analysis of partition coefficient in Al-Mg alloys2016Ingår i: Iranian Journal of Materials Science and Engineering, ISSN 1735-0808, Vol. 13, nr 2, s. 62-72Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Because the partition coefficient is one of the most important parameters affecting microsegregation, the aim of this research is to experimentally analyse the partition coefficient in Al-Mg alloys. In order to experimentally measure the partition coefficient, a series of quenching experiments during solidification were carried out. For this purpose binary Al-Mg alloys containing 6.7 and 10.2 wt-% Mg were melted and solidified in a DTA furnace capable of quenching samples during solidification. Cooling rates of 0.5 and 5 KJmin were used and samples were quenched from predetermined temperatures during solidification. The fractions and compositions of the phases were measured by quantitative metallography and SEM/EDX analyses, respectively. These results were used to measure the experimental partition coefficients. The resultant partition coefficients were used to model the concentration profile in the primary phase and the results were compared with equilibrium calculations and experimental profiles. The results of calculations based on the experimental partition coefficients show better consistency with experimental concentration profiles than the equilibrium calculations.

  • 10. Avazkonandeh-Gharavol, M. H.
    et al.
    Haddad-Sabzevar, M.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    On the microsegregation of Al-Mg alloys by thermal analysis and numerical modeling2014Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 610, s. 462-471Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Knowledge about solid fraction versus temperature during solidification is crucial for the control of solidification processes. In the present paper solidification sequence and path of Al-Mg binary alloys containing 6.7 and 10.2 wt.% Mg was investigated by a series of DTA and quenching experiments and numerical modeling in 0.5 and 5 K min(-1) cooling rates. Experimental results show that at both cooling rates, Al-6.7 wt.% Mg solidifies with a single phase structure, but Al-10.2 wt.% Mg solidifies with a two phase structure. According to the results of numerical modeling, good agreement between calculated solidification curves and experimental solid fractions, but poor correlation with concentration profiles. The source of discrepancies is discussed according to different theories of microsegregation.

  • 11.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    An Insight into the Effect of Deformation on Carbide Dissolution in the Band Structure of Bearing Steel2013Ingår i: Diffusion In Solids And Liquids VIII, Trans Tech Publications Inc., 2013, s. 171-176Konferensbidrag (Refereegranskat)
    Abstract [en]

    Dendritic segregation in deformed samples remains in the form of band structure, which is a high-strained region. The present work investigates the effect of the uphill diffusion process, occurring during deformation, on the dissolution of carbide particles in the band structure. A series of hot compression tests are performed on the cast structure of bearing steel by using a hydraulic testing machine, MTS 810. Cylindrical specimens are deformed in a temperature range of 800 degrees C to 900 degrees C and at strain rates of 5s(-1) and 0.5s(-1). In order to eliminate the recovery process, samples are immediately quenched after the compression. The microsegregation of Cr, Mo, Mn and Si are investigated in the band structure, which shows a tendency of uphill diffusion during deformation process. The results show that the volume fraction of carbides varies with the increased straining. The results also show that deformation causes the fragmentation, dispersion of pearlite in the dendrites and the dissolution of spheroidized carbides in the band structure.

  • 12.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Disorder Structure formation during plastic defroamtion of pure copper2012Ingår i: International journal of material science, ISSN 0973-4589, Vol. 7, nr 3, s. 169-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of the deformation process at 300˚C on the cast structure of pure copper is investigated. The temperature measurements during compression test are performed by a new experimental method developed earlier [1]. The deformed structure is studied with the aid of optical and transmission electron microscopy. Micrographs show the formation of deformed bands with high internal energy, due to many lattice defects. The strain energy calculations are based on an energy balance and the data obtain from micrograph studies performed by optical and transmission electron microscopy. It is found that there is a significant difference in the strain energy values obtained in the present work compared to the values available in the literature.  The strain energy values obtained in the band structure of the present work are 17.4% to 24% of the heat of fusion of Cu. Such high energy is sufficient to change the normal FCC structure to a disordered atomic structure in the highly deformed regions, during plastic deformation.

  • 13.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Effect of deformation on microsegregation in cast structure of bearing steel2012Ingår i: TMS 2012 141st Annual Meeting & Exhibition - Supplemental Proceedings, Vol 2: Materials Properties, Characterization, And Modeling, 2012, Vol. 2, s. 309-316Konferensbidrag (Refereegranskat)
    Abstract [en]

    Microsegregation changes in the cast structure of a five-ton ingot of ball bearing steel are investigated by a series of hot compression tests. Cylindrical specimens are deformed at a temperature range of 800 degrees C to 900 degrees C and strain rates of 0.5 s(-1). Samples are quenched after the compression in order to eliminate the homogenization time. Subsequently they are analysed with the aid of Electron Microprobe Analysis (EMPA) in order to investigate the effect of hot compression on microsegregation of Mo, Cr, Mn and Si. It is found that highly segregated regions are regions for formation of deformation bands. It seems that the degree of microsegregation increases by increasing the deformation. An attempt is made to estimate the diffusion coefficients of alloying elements during the deformation process. The increase of microsegregation during deformation is explained by tendency for uphill diffusion.

  • 14.
    Basirat, Mitra
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Plastic Deformation and Recrystallization in Incoloy 825Manuskript (preprint) (Övrigt vetenskapligt)
  • 15. Dhindaw, B. K.
    et al.
    Antonsson, Tomas
    KTH, Tidigare Institutioner, Materialvetenskap.
    Tinoco, J.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner, Materialvetenskap.
    Characterization of the peritectic reaction in medium-alloy steel through microsegregation and heat-of-transformation studies2004Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 35A, nr 9, s. 2869-2879Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the present work, the phenomenon of the peritectic reaction was characterized in a medium-ailoy steel. Several directional solidification and thermal-analysis experiments were done to investigate the reaction process. Directional solidification experiments carried out did not tend to show any direct evidence of a peritectic reaction. Microsegregation studies on the directionally solidified samples and those solidified under isothermal conditions bring out some interesting features. It has been documented that if the segregation ratio for Ni is higher than that for Cr, there is a correlation that the peritectic reaction had occurred in that region. On the other hand, a higher Cr segregation ratio as compared to Ni showed the possibility that the liquid had directly transformed to gamma-austenite without undergoing a peritectic reaction. Measurement of energies of transformations and the analysis of their values in different segments of the cooling-curve differential thermal analysis (DTA) experiments have helped in understanding the peritectic reaction. It is revealed that the transformation is more like diffusionless transformation, where gamma-austenite directly precipitates from delta-ferrite. Indeed, this proposition is also supported by the segregation patterns for Cr and Ni obtained in the solidified samples of this steel during directional solidification and DTA experiments and also by calculations to show the presence of enough lattice defects or vacancies to aid the aforementioned transformation.

  • 16. Dhindaw, B. K.
    et al.
    Kumar, L.
    Alkarkhi, N. C. Amer
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Microstructure development and solute redistribution in aluminium alloys under low and moderate shear rates during rheo processing2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 156-164Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microstructural features and microsegregational behaviour of solute are studied in shear or stir-cast aluminium alloys under low and moderate shear rates. Alloys studied are Al-6.2% Cu, Al-7.3% Si and Al-13.2% Mg. In all the cases, microstructures of the primary pre-quench solid for stir-cast samples show rosette or ellipsoidal morphologies. Volume fractions of pre-quenched solid phase show significantly higher values for stir-cast alloys as compared to calculated. Microsegregation studies by microprobe analysis along the grains of the samples solidified under different treatment conditions show that stir casting changes the segregation pattern significantly. Except for Al-13.2% Mg alloys lower values than those calculated by Scheil's microsegregation equation are observed for other systems. A model for microstructure evolution during stir casting is presented. The microsegregation patterns have been discussed in terms of interaction between the diffusing solute and the vacancies migrating from solid into liquid.

  • 17.
    Ekbom, Lars B
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Eliasson, Anders
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Liquid-phase Sintering of Tungsten Composites in Space. Agglomerate Separation and Particle Growth1989Ingår i: High Temperatures-High Pressures, ISSN 0018-1544, E-ISSN 1472-3441, Vol. 21, s. 507-514Artikel i tidskrift (Refereegranskat)
  • 18.
    Elfsberg, Jessica
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Oscillation Mark Formation on Continuously Cast Copper2003Rapport (Övrigt vetenskapligt)
  • 19.
    Elfsberg, Jessica
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialens processteknologi.
    Oscillation Mark Formation on Continuously Cast Stainless Steel and Carbon Steel Slabs2003Rapport (Övrigt vetenskapligt)
  • 20.
    Elfsberg, Jessica
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Theoretical Study of Oscillation Mark Formation in Continuous Casting Processes2003Rapport (Övrigt vetenskapligt)
  • 21.
    Elfsberg, Jessica
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Widell, Björn
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Experimental Study of the Formation of Oscillation Marks in Continuous Casting of Steel Billets2002Ingår i: 4th European Continuous Casting Conference, Oct 14-15 2002, Birmingham,England, 2002Konferensbidrag (Övrigt vetenskapligt)
  • 22.
    Eliasson, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Ekbom, L.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Tungsten grain separation during initial stage of liquid phase sintering2008Ingår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 51, nr 4, s. 343-349Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The initial stage, the first few seconds of liquid phase sintering has been investigated in experiments using a tungsten heavy alloy with low tungsten content. The heavy alloy has been melted in a temperature gradient for short periods, similar to 9 s in an ellipsoid mirror furnace. During the liquid phase sintering at about 1470 degrees C, a penetration followed by a remarkably rapid separation and dispersion of the tungsten grains by the molten matrix occur. The suggested explanation for this grain separation and dispersion is based on the effect of composition gradients in the liquid matrix and a theory based on interagglomerate melt swelling due to a Kirkendall effect.

  • 23.
    Eliasson, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Ekbom, Lars B
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Fredriksson, Hasse
    Liquid Penetration and Particle Separation during the Initial Stage of Liquid Phase Sintering2006Ingår i: Metallurgical transactions. A, ISSN 0360-2133Artikel i tidskrift (Refereegranskat)
  • 24.
    Eliasson, Anders
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Interaction behaviour between alumina particles and solidification front and particle behaviour in iron based alloys at deoxidation by Kirkendall effect2007Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 20, nr 3, s. 127-130Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The present paper deals with interaction phenomena by particles in liquid metals. The interpretation is to make an initial analysis how the model by Kirkendall, for diffusion phenomena in solids, can be used for the analysis of particle behaviour in liquids. Whenever there is an unequal solutal field, insoluble particles may 'move' due to concentration gradients in the liquid and a difference of diffusion rates of the solute atoms. The analysis deals with the following melt/particles interactions: one is the interaction behaviour between the solidification front and the formed slag oxide particles of Al2O3 and the critical velocity for pushing/engulfment at the interface and the other is the movement and clustering of precipitated alumina inclusions around SiO2 or FeO inclusions formed in a steel melt before deoxidation. Despite the uncertainty of the used material constants and the assumed concentration profiles, the results of the present study are in accordance with some shown experimental particle movements.

  • 25.
    Eliasson, Anders
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Hailom Yosef, Futsum
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Dynamic temperature measurements and solidification structures in centrfugally casted IN718.2003Konferensbidrag (Övrigt vetenskapligt)
  • 26.
    Emi, Toshihiko
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    High-speed continuous casting of peritectic carbon steels2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 2-9Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Productivity of an integrated steel plant is improved by high-speed casting of hypo-peritectic steels that makes the productivity of caster meet basic oxygen furnace. In high-speed casting, however, strands of the steels tending to form cracks on the shell in the mold, require off-line conditioning that limits the plant productivity and premium yield. Hypo-peritectic transformation occurring on solidification in mold results in irregular shell-surface roughness that causes non-uniform heat transfer to the mold, causing local lifting of the shell from the mold, recalescence, and surface cracks. Influential factors are summarized on the development of the surface roughness, the non-uniform heat transfer and the decline of mechanical properties of the shell upon recalesce. Effective means are presented to reduce the non-uniformity and the cracks at high casting speeds by controlling the properties of mold flux film infiltrating into the solidifying shell/mold boundary.

  • 27. Fjellstedt, J.
    et al.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    On the crystallization process of hypoeutectic Al-6 % Cu, unmodified and Sr-modified Al-2 % Si solidified alloys2003Ingår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 5, nr 02-jan, s. 24-32Artikel i tidskrift (Refereegranskat)
  • 28. Formenti, A.
    et al.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Mitchell, A.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Solidification sequence and carbide precipitation in Ni-base superalloys IN718, IN625 AND IN9392005Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, nr 4, s. 239-258Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Differential Thermal Analysis (DTA) and Directional Solidification and Quenching (DSQ) were used to evaluate the solidification and precipitation sequence for the Ni-base superalloys IN718, IN625 and IN939. They all showed a similar precipitation sequence, with an initial precipitation of gamma dendrites, followed by an intermediate non-invariant divorced eutectic reaction of type L -> gamma + MC, and a final eutectic precipitation of Laves phase for alloy IN718 and IN625 and of eta-phase for alloy IN939. The reaction temperatures and the amounts of carbides and of final precipitates were evaluated. Precipitated nitrides were found to act as nucleation sites for the precipitation of blocky carbides/carbonitrides, at low interdendritic supersaturation, while in interdendritic regions with high supersaturation, a 'script-like' carbide formation was found instead.

  • 29.
    Formenti, Angelo
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Eliasson, Anders
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Keramteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the dendritic growth and microsegregation in Ni-base superalloys IN718, IN625 and IN9392005Ingår i: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, nr 4, s. 221-238Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Directional Solidification and Quenching (DSQ) has been used to analyse the solidification, segregation and precipitation behaviour of the Ni-base alloys IN718, IN625 and IN939. The microsegregation in the primary solidified gamma-phase was analysed by Energy Dispersive Spectroscopy (EDS) and were mainly found to be Nb for alloy IN718 and Ti for alloy IN939. The microsegregation behaviour were analysed by numerical back diffusion models and it was found that the diffusion rate in the samples was higher than expected from the theory. A suggested explanation was that this was an effect of the formation of lattice defects during the solidification process. The coarsening process that occurs during the further cooling of the samples is proved to be by the mechanism of back diffusion i.e. the smaller secondary dendrite arms grow together with the thicker ones into a plate.

  • 30.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    On the solidification of metal alloys during microgravity conditions2015Ingår i: Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu, The Minerals, Metals, and Materials Society, 2015, s. 9-13Konferensbidrag (Refereegranskat)
    Abstract [en]

    Thermal analysis and unidirectional solidification experiments of mainly Al-, Sn- and Pb-base alloys has been performed during Rocket Flights, Parabolic aircraft flights, Space Lab, and GAS-Shuttle flights over three decades. In this presentation the special equipments developed and the experimental results from the different flight opportunities are to be presented. The cooling rates in the theraml analysis experiments have varied from around 0.01 to 10 C/Sec. The coarsnes fo the structure has been evaluated and the main effect is an increase in coarsness with decreasing gravity. The solidification undercooling was measured and it was mainly lower during microgravity conditions. The microgravity conditions gave mostly a larger effective partition coeffecient. The result will be presented and shortly discussed from existing theoretical standpoints and the difference will be analysed.

  • 31.
    Fredriksson, Hasse
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Elfsberg, Jessica
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Thoughts about the Initial Solidification Process during Continuous Casting of Steel2002Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, s. 292-297Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    The initial solidification during continuous casting is very important for the surface quality of the strand. Oscillation marks are formed by the movement of the mould. One mainly distinguishes between two different types of marks, namely folding marks and overflow marks. The formation of these can be described by the heat flow and the surface tension balance. A theoretical analysis outlining the most important parameters controlling the formation of these marks is presented. A metallographic analysis of the formation was also performed. The theory and observations have been used to analyse the effect of casting speed and oscillation frequency on the formation of different types of marks. It is shown that a meniscus is formed at the top of the growing shell. The maximum height of the meniscus determines the ideal distance between the marks. The mould frequency is related to this height. A frequency that is far from ideal causes overflow marks and folding marks with macrosegregation and cracks. The distance between the marks is, in such cases, not constant. The depth of the marks is calculated from the heat flow and the surface tension balance.

  • 32.
    Fredriksson, Hasse
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Eliasson, Anders
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Ekbom, Lars B
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Penetration of Tungsten Grain Boundaries by a Liquid Fe-Ni Matrix1995Ingår i: International Journal of Refractory Metals and Hard Materials, ISSN 0958-0611, Vol. 13, s. 173-179Artikel i tidskrift (Refereegranskat)
  • 33.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, E.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    A model of liquid metals and its relation to the solidification process2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 455-459Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    X-ray analysis shows that a liquid is build up of clusters of atoms with a certain number of nearest neighbours. The X-ray analysis shows that 8-11 nearest neighbours surround each atom. Each cluster has a crystal-like structure. Between the clusters there are some free atoms and free electrons. The enthalpy of fusion is according to Richard's rule around the gas constant times the temperature of melting and the heat capacity in the liquid state is normally constant and for some metals lower than that in the solid state. For metals with low melting points it will decrease further with increasing temperature. This behaviour of the metals can be explained by the use of statistical mechanics and by assuming that the clusters, observed by X-ray analysis are rotating around a centre of its mass. The cluster model is applied to explain the diffusion rate in liquid metals. The effect of the experimental set upon measurements of diffusion constants is discussed as well as its effect on crystal growth.

  • 34.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Haddad-Sabzevar, M.
    Hansson, K.
    Kron, J.
    Theory of hot crack formation2005Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 21, nr 5, s. 521-529Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The hot crack sensitivity in metals is suggested to be caused by the supersaturation of vacancies created during the solidification process. Equations have been derived to predict the nucleation and growth of cracks by the condensation of vacancies. The transition temperature from brittle to ductile fracture was found to be related to the decrease in the supersaturation of vacancies due to an annealing process. The hot crack sensitivity was observed to be related to the supersaturation of vacancies, the diffusion rate, and the structure coarseness. The effect of surface active elements such as phosphorous and sulphur in steel alloys is discussed.

  • 35.
    Fredriksson, Hasse
    et al.
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Hansson, K.
    Olsson, A.
    On the mechanism of liquid copper penetration into iron grain boundaries2001Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 30, nr 1, s. 41-50Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The penetration of liquid copper into iron grain boundaries has been experimentally analysed. During the penetration, Cu diffuses into the iron grains. In this case, a Kirkendall effect is created, leading to vacancies which diffuse to the grain boundaries where they condense. A grain boundary crack is formed, which will be filled with liquid Cu. The driving force for penetration of the Cu-liquid into the grain boundary is the condensation of vacancies and the surface/interface free energy change. A theoretical model describing the penetration rate is derived and a good agreement between theory and experiments was achieved. The model is general and can be used to explain liquid metal embrittlement.

  • 36.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Stjerndahl, J.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Tinoco, J.
    On the solidification of nodular cast iron and its relation to the expansion and contraction2005Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, s. 363-372Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Directional solidification and quench-out thermal analysis experiments have been performed in Mg-treated cast iron alloys. The volume fraction of liquid, allstenite and graphite was evaluated. It was observed that the volume fraction of austenite is much larger than expected from the equilibrium phase diagram at the beginning of the solidification process. It was also been observed that the last melt solidifies far below the equilibrium eutectic temperature. The solidification process was analyzed by non-equilibrium thermodynamic models. The theoretical treatment was supported by the observation that the latent heat decreases during the solidification process. The formation of small pores was observed at the very end of the solidification. An explanation for the formation of the small pores is given in terms of a vacancies creep model. The formation of macropores was related to the large fraction of austenite formed during the first part of the solidification process.

  • 37.
    Fredriksson, Hasse
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Metallernas gjutning.
    Åkerlind, Ulla
    University of Stockholm, Sweden.
    Solidification and Crystallization Processing in Metals and Alloys2012Bok (Refereegranskat)
    Abstract [en]

    Solidification and Crystallization Processing in Metals and Alloys. Hasse Fredriksson KTH, Royal Institute of Technology, Stockholm, Sweden. Ulla Åkerlind University of Stockholm, Sweden. Solidification or crystallization occurs when atoms are transformed from the disordered liquid state to the more ordered solid state, and is fundamental to metals processing. Conceived as a companion volume to the earlier works, Materials Processing during Casting (2006) and Physics of Functional Materials (2008), this book analyzes solidification and crystallization processes in depth. Starting from the thermodynamic point of view, it gives a complete description, taking into account kinetics and mass transfer, down to the final structure. Importantly, the book shows the relationship between the theory and the experimental results. Topics covered include: Fundamentals of thermodynamics. Properties of interfaces. Nucleation. Crystal growth - in vapours, liquids and melts. Heat transport during solidification. processes. Solidification structures - faceted, dendritic, eutectic and peritectic. Metallic glasses and amorphous alloy melts. Solidification and Crystallization Processing in Metals and Alloys features many solved examples in the text, and exercises (with answers) for students. Intended for Masters and PhD students as well as researchers in Materials Science, Engineering, Chemistry and Metallurgy, it is also a valuable resource for engineers in industry.

  • 38.
    Hailom Yosef, Futsum
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On the peritectic reaction of iron based binary alloys2005Rapport (Övrigt vetenskapligt)
  • 39.
    Hailom Yosef, Futsum
    et al.
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Metallernas gjutning.
    On the solidification behaviour of ferritic stainless steels2003Rapport (Övrigt vetenskapligt)
  • 40. Hansson, K.
    et al.
    Droujevski, M.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Hot ductility of an Fe-10%Ni alloy during penetration of copper2002Ingår i: Scandinavian journal of metallurgy, ISSN 0371-0459, E-ISSN 1600-0692, Vol. 31, nr 4, s. 256-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Today's available theories for hot crack formation are based on the fact that hot cracks are formed in the presence of liquid films in the interdendritic areas or at the grain boundaries, which are exposed to tensile stress. Copper is well known to cause hot shortness in steels. In order to study how the liquid embrittles the material, high-temperature tensile tests were performed at two strain rates during the penetration of liquid copper into Fe-10%Ni. The penetration distance was measured in samples that were exposed to strain without fracturing. The ductility (area reduction), strain and ultimate tensile stress were determined. Microprobe analysis was performed on the fractured samples. The transition temperature of ductility was found at 1400-1450degreesC without copper penetration whereas it occurred at 1025-1078degreesC during the penetration of copper, i.e. copper starts to embrittle at a temperature below its melting point. The microprobe measurements showed that the diffusion rate of copper into Fe-10%Ni was enhanced when the lattice was strained. The results are discussed in terms of a new theory concerning vacancy formation and condensation as the dominating mechanism for hot crack formation during solidification.

  • 41. Hansson, K.
    et al.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    On the behavior of hot crack formation during solidification in Fe-Ni alloys2003Ingår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 5, nr 02-jan, s. 66-77Artikel i tidskrift (Refereegranskat)
  • 42. Kim, S. K.
    et al.
    Lee, Y. D.
    Hansson, K.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Influence of cooling rate on the hot cracking formation of nickel rich alloys2002Ingår i: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 42, nr 5, s. 512-519Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Hot cracking formation and its mechanism in invar alloys (Fe-36mass%Ni) during continuous casting was investigated. The invar alloy is very sensitive to hot cracking due to its low transition temperature of brittle to ductile fracture even though its solidification interval is narrow. At the cooling rate of 10degreesC/min the transition temperature of brittle to ductile fracture is about 113degreesC below the solidus temperature. An increased cooling rate in invar alloy increases transition temperature of brittle to ductile fracture. It is increased to about 43degreesC below the solidus temperature when the cooling rate is increased to 100degreesC/min. A mechanism of hot cracking formation in invar alloys has been proposed. Hot cracks in invar alloys with a fast cooling rate are formed between the primary dendrites due to the equiaxed solidification structure. However, at slow cooling rate, hot cracks are formed between the grain boundaries due to the columnar structure.

  • 43.
    Korojy, Bahman
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Ekbom, Lars
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On solidification shrinkage of copper-lead and copper-tin-lead alloys2009Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 22, nr 1-4, s. 179-182Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Solidification shrinkage is an important concept in achieving sound castings. In the present work solidification shrinkage was studied in copper-lead and copper-lead-tin alloys. A series of solidification experiments was performed under different cooling rates using a dilatometer which was developed for melting and solidification purposes. The volume change was measured during primary solidification and the monotectic reaction. In order to explain the volume-changing results, the sample macrostructures were studied to evaluate gas and shrinkage cavities which were formed during the solidification. Furthermore, the volume fraction of the primary phase during solidification was evaluated in the samples that were quenched from different temperatures below the liquidus temperature. A shrinkage model was used to explain the volume changes during solidification.

  • 44.
    Korojy, Bahman
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On solidification and shrinkage of brass alloys2009Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 22, nr 1-4, s. 183-186Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The solidification process was investigated in brass alloys containing a wide range of zinc, between 32.5 and 47.1 wt-%. A series of solidification experiments was performed under different cooling rates using differential thermal analysis (DTA) and a confocal mirror furnace. The cooling rate and the solidification under cooling temperature were evaluated from cooling curves. Furthermore, the peritectic reaction was studied in view of the starting and the ending temperatures and shrinkage behaviour. The volume change was measured in the peritectic alloys using a dilatometer which was developed to investigate the melting and solidification processes. A theoretical analysis was developed to evaluate the volume change effect on the peritectic reaction.

  • 45.
    Korojy, Bahman
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    On solidification of hypereutectic Al-Si alloys2009Ingår i: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 62, nr 4-5, s. 361-365Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Precipitation of primary silicon was studied in Al-Si hypereutectic alloys with 15, 18, and 25 wt. % silicon content. The alloys were solidified with different cooling rates from different super heat temperatures. The liquidus and eutectic temperature were evaluated from the cooling curves. The liquidus temperature was found to decrease with cooling rate. The evaluation of microstructure showed that the fraction of primary silicon decreased with increasing the cooling rate and super heat temperature. Furthermore, the morphology of the primary silicon changed as an effect of cooling rate and super heat temperature.

  • 46. Kron, J.
    et al.
    Antonsson, T.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Air gap formation during solidification in cylindrical castings of pure aluminium and eutectic Al-Si2002Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 14, nr 5, s. 275-285Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Casting of aluminium and eutectic Al-Si in a cylindrical mould has been performed. The air gap formed between the inner mould wall and the solidified shell was measured throughout the solidification process. Simultaneously the temperature distribution in the metal and the mould was measured. Calculations of the shrinkage of the metal were performed. The shrinkage due to thermal contraction was found to be too small to fit the measurements. A new model for the solidification process and the air gap formation was used, where the effect of the formation and condensation of lattice defects was considered. The condensation of lattice defects was used to explain the shrinkage and the air gap found experimentally.

  • 47. Kron, J.
    et al.
    Bellet, M.
    Ludwig, A.
    Pustal, B.
    Wendt, J.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Comparison of numerical simulation models for predicting temperature in solidification analysis with reference to air gap formation2004Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 17, nr 5, s. 295-310Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    As a result of its influence on heat transfer between cast part and mould, air gap formation is an important problem for many casting processes. The general explanation for gap formation is that, as a result of stresses and distortions that are created from inhomogeneous cooling, shrinkage of the casting and expansion of the mould occur. In this paper, different thermomechanical approaches are applied to a well defined casting process using three commercial and one in-house codes and their predictions are compared with experimental findings. The experimental data were obtained from the solidification and subsequent cooling of cylindrical castings of eutectic Al-13% Si and ternary Al-7% Si-0.3% Mg alloys. Based on these findings, the major differences between the predictions of the models and the actual formation of the air gap are discussed.

  • 48. Kron, J.
    et al.
    Bellet, M.
    Ludwig, A.
    Wendt, J.
    Pustal, B.
    Fredriksson, Hasse
    KTH, Tidigare Institutioner                               , Materialvetenskap.
    Cooperation within MEBSP on the subject of air gap formation during a casting process2003Ingår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 5, nr 02-jan, s. 78-79Artikel i tidskrift (Refereegranskat)
  • 49. Kron, J.
    et al.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Measurements and modelling of air gap formation in Cu-based alloys2005Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 18, nr 1, s. 21-28Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of an air gap has been experimentally studied during solidification of pure Cu, Cu-Te and Cu-6%Sn in a cylindrical mould. The displacements of the casting and the mould causing an air gap have been measured during solidification and cooling of the casting. The temperature distribution was measured simultaneously. Mathematical modelling has been performed to increase the understanding of the solidification process and the shrinkage of the casting leading to air gap formation. A model, which has been tested in earlier work showing good results for aluminium based alloys, has been applied here to describe air gap formation during solidification of copper based alloys. The model includes the effect of the formation and condensation of vacancies on the solidification process as well as on the material shrinkage resulting in air gap formation. The results from the modelling show a reasonable agreement with the experimental measurements.

  • 50. Kron, J.
    et al.
    Lagerstedt, A.
    Fredriksson, Hasse
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Materialens processteknologi.
    Measurements and modelling of air gap formation in aluminium based alloys2005Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 18, nr 1, s. 29-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The formation of an air gap has been experimentally studied during solidification of several aluminium based alloys. Air gap widths and temperature distribution have been measured during solidification in a cylindrical mould. The effect of grain refinement on heat transfer and air gap formation has been studied. Mathematical modelling has been performed to increase the understanding of the solidification process and air gap formation. A model was developed for description of air gap formation in alloys solidifying with varying solidification intervals. The model includes the effect of formation and condensation of lattice defects on the solidification process and air gap formation. The calculated shrinkage using this model shows good agreement with the experimental data.

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