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  • 1. Andersson, J.
    et al.
    Raza, S.
    KTH.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Surreddi, K. B.
    Solidification of alloy 718, ati 718Plus® and waspaloy2014In: 8th International Symposium on Superalloy 718 and Derivatives 2014, 2014, p. 181-192Conference paper (Refereed)
    Abstract [en]

    Alloy 718, ATI 718Plus® and Waspaloy have been investigated in terms of what their respective solidification process reveals. Differential thermal analysis was used to approach the task together with secondary electron and back scattered electron detectors equipped with an energy dispersive X-ray spectroscopy detector. These experimental methods were used to construct pseudo binary phase diagrams that could aid in explaining solidification as well as liquation mechanisms in processes such as welding and casting. Furthermore, it was seen that Waspaloy has the smallest solidification range, followed by Alloy 718, and finally ATI 718Plus® possessing the largest solidification interval in comparison.

  • 2.
    Antonsson, Tomas
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Ekbom, Lars B.
    KTH, Superseded Departments, Casting of Metals.
    Eliasson, Anders
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Liquid Ni-Fe penetration and recrystallisation in tungsten2003In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 21, no 3-4, p. 159-170Article in journal (Refereed)
    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.

  • 3.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid Phase Sintering of Tungsten Composites1994In: Conference proceedings of the Sefström Symposium, Stockholm: KTH , 1994, p. 293-304Conference paper (Other academic)
  • 4.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid Phase Sintering of Tungsten Composites in Space: Results of Tests Performed in Texus1988In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 8, no 12, p. 315-319Article in journal (Refereed)
  • 5.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition1992In: Microgravity Q., Vol. 2, no 4, p. 227-232Article in journal (Refereed)
  • 6.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid Phase Sintering of Tungsten Composites under Microgravity: Effect of Matrix Composition. Particle Growth1992In: Proc. Tungsten & Tungsten Alloys, p. 97-110Article in journal (Refereed)
  • 7.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid Phase Sintering under Microgravity in Space1988In: Modern developments in powder metallurgy, ISSN 0074-7513, Vol. 18-21, p. 63-Article in journal (Refereed)
  • 8.
    Ekbom, Lars B
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Fredriksson, Hasse
    KTH, Superseded Departments, Materials Science and Engineering.
    Liquid-phase Sintering of Tungsten Composites in Space. Agglomerate Separation and Particle Growth1989In: High Temperatures-High Pressures, ISSN 0018-1544, E-ISSN 1472-3441, Vol. 21, p. 507-514Article in journal (Refereed)
  • 9.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Interaction behaviour between solid inclusions and solidification front and inclusion behaviour in iron base alloys during teeming and at deoxidation by the Kirkendall Effect2006Report (Other academic)
  • 10.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Liquid phase sintering of W-Ni-Fe composites: liquid penetration, agglomerate separation and tungsten particle growth2006Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    The initial stage of liquid phase sintering, involving liquid penetration, agglomerate separation, particle spreading and growth has been investigated in experiments using tungsten heavy alloys. The particle composites used were produced by hot isostatic pressing (HIP) of pure powder mixtures of W-Ni-Fe-(Co). By using different HIP temperatures, volume fractions of tungsten, alloying elements like Cobalt and Sulphur or excluding Iron from the matrix, liquid penetration, agglomerate separation and particle growth conditions were affected. The investigations were performed mainly under microgravity (sounding rockets or parabolic trajectories by airplanes) but at high tungsten particle fractions, short sintering times or at infiltration of solid pure tungsten, they were performed at normal gravity. The liquid penetration of the tungsten agglomerates is explained by initial wetting under non-equilibrium conditions, due to the reaction between the liquid matrix and the particles, and a decrease of interfacial energy. The dissolving of tungsten gives a pressure drop in the penetrating liquid and a driving force for the liquid movement by a suggested parabolic penetration model. For cold worked tungsten, a penetration theory was proposed, where an internal stress release in the penetrated tungsten grains creates space for the advancing liquid.

    The spreading of the tungsten agglomerates is explained by an interagglomerate melt swelling due to a Kirkendall effect. The liquid matrix undergoes a volume increase since the diffusion rates of Ni-Fe are higher than for W and initial concentration gradients of W and Ni, Fe exists. The suggested model by Kirkendall are also used for an analysis of the interaction behaviour between solid particles and a solidification front and inclusion behaviour in iron base alloys during teeming and deoxidation.

    The average tungsten particles size decrease initially since part of the tungsten particles is dissolved when the non-equilibrium matrix phase is melting. When equilibrium is reached, the tungsten particles grow in accordance with the Ostwald ripening process by an approximately 1/3 power law. Larger particle fraction of particles showed a higher growth rate, due to shorter diffusion distances between the particles. Cobalt, Sulphur and absence of iron in the matrix were found to increase the growth rate of the tungsten particles due to a higher surface tension between the solid tungsten particles and the matrix melt.

  • 11.
    Eliasson, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Ekbom, L.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Tungsten grain separation during initial stage of liquid phase sintering2008In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 51, no 4, p. 343-349Article in journal (Refereed)
    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.

  • 12.
    Eliasson, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Ekbom, Lars B
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fredriksson, Hasse
    Liquid Penetration and Particle Separation during the Initial Stage of Liquid Phase Sintering2006In: Metallurgical transactions. A, ISSN 0360-2133Article in journal (Refereed)
  • 13.
    Eliasson, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Interaction behaviour between alumina particles and solidification front and particle behaviour in iron based alloys at deoxidation by Kirkendall effect2007In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 20, no 3, p. 127-130Article in journal (Refereed)
    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.

  • 14.
    Eliasson, Anders
    et al.
    KTH, Superseded Departments, Casting of Metals.
    Hailom Yosef, Futsum
    KTH, Superseded Departments, Casting of Metals.
    Fredriksson, Hasse
    KTH, Superseded Departments, Casting of Metals.
    Dynamic temperature measurements and solidification structures in centrfugally casted IN718.2003Conference paper (Other academic)
  • 15. Formenti, A.
    et al.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Mitchell, A.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    Solidification sequence and carbide precipitation in Ni-base superalloys IN718, IN625 AND IN9392005In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, no 4, p. 239-258Article in journal (Refereed)
    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.

  • 16.
    Formenti, Angelo
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    On the dendritic growth and microsegregation in Ni-base superalloys IN718, IN625 and IN9392005In: High Temperature Materials and Processes, ISSN 0334-6455, E-ISSN 2191-0324, Vol. 24, no 4, p. 221-238Article in journal (Refereed)
    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.

  • 17.
    Fredriksson, Hasse
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Ekbom, Lars B
    KTH, Superseded Departments, Materials Science and Engineering.
    Penetration of Tungsten Grain Boundaries by a Liquid Fe-Ni Matrix1995In: International Journal of Refractory Metals and Hard Materials, ISSN 0958-0611, Vol. 13, p. 173-179Article in journal (Refereed)
  • 18. Lockowandt, C
    et al.
    Löth, K
    Ekbom, Lars B
    KTH, Superseded Departments, Materials Science and Engineering.
    Eliasson, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Wollmar Jarfors, Anders
    KTH, Superseded Departments, Materials Science and Engineering.
    Microgravity Applications Furnace Facility, MAFF, for Parabolic Flights.1992In: Proc. VIIIth Europ. Symp. Mat. and Fluid Sci. in Microg, 1992, Vol. 1, p. 383-386Conference paper (Refereed)
  • 19.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Prediction of particle size for water atomised metal powders: parameter study2012In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 55, no 1, p. 45-53Article in journal (Refereed)
    Abstract [en]

    This work aims to investigate how some significant atomising parameters influence the mass median particle size d50 of water atomised metal powders. More specifically, these were water pressure, melt flowrate, water jet angle, liquid metal viscosity and surface tension. Existing models for the prediction of d50 during water atomisation were reviewed. The selected models were fitted and compared with atomising experiments of liquid iron containing 0.5–4.4%C. Experimental results and model calculations were used in a parameter study to investigate how the different parameters influenced d50. The effect on d50 was large for the water pressure, medium for the viscosity and low for the melt flowrate and surface tension. Model calculations indicate that the jet angle has a large effect on d50, which should be verified by additional studies. The model proposed by Bergquist (B. Bergquist: Powder Metall., 1999, 42, 331–343) showed the best agreement with the current experimental data.

  • 20. Persson, Fredrik
    et al.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jönsson, Pär G.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Oxidation of Water Atomized Metal Powders2014In: Steel Research International, ISSN 1611-3683, E-ISSN 1869-344X, Vol. 85, no 12, p. 1629-1638Article in journal (Refereed)
    Abstract [en]

    This study focuses on the oxidation of water atomized metal powders. Pilot plant experiments were performed using liquid iron alloyed with manganese and carbon. The powder particle shape and the oxides were determined using optical and scanning electron microscopy with energy dispersive X-ray microanalysis. The oxygen in the atomized powders was mainly present as thin surface oxide layers, which were determined to increase from 10 to 40-60 nm, at increased particle sizes from 10 to 750 mu m. In addition, manganese oxides were observed to be unevenly distributed at the surface of several particles for iron powders alloyed with 0.3mass% Mn. Experimental data indicated that between 10 and 20% of the manganese was present as oxides in the powders. However, equilibrium calculations predicted a strong driving force for oxidation of manganese. More specifically, it was estimated that only 4% of the initial manganese content remained in the final atomized powders.

  • 21. Persson, Fredrik
    et al.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär Göran
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Influence of liquid metal properties on water atomised iron powders2012In: ISIJ International, ISSN 0915-1559, E-ISSN 1347-5460, Vol. 52, no 12, p. 2130-2138Article in journal (Refereed)
    Abstract [en]

    The main focus of the present study was the influence of liquid metal properties on the particle size during water atomisation. Experiments for liquid iron showed that alloy additions of carbon and sulphur decreased the particle size. Moreover, it was indicated that the reduced d50 value at increased %C and %S contents may be related to a decreased viscosity and surface tension respectively. An alternative mechanism could be that raised superheats at increased carbon contents increased the total available time for atomisation. This may also have decreased the particle size. The influence of surface tension and viscosity on the d50 value was further analysed with a theoretical d50 model proposed in a previous work. A reduced viscosity from 6.8 to 4.3 mPa s decreased the d50 value with 33%. In addition, the particle size was estimated to decrease with 27% by decreasing the surface tension from 1 850 to 900 mN m-1.

  • 22.
    Persson, Fredrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Jönsson, Pär G
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Process Metallurgy.
    Influence of liquid metal properties for water atomised metal powders2012Manuscript (preprint) (Other academic)
    Abstract [en]

    The main focus of the present study was the influence of liquid metal properties on the particle size during water atomisation. Experiments for liquid iron showed that alloy additions of carbon and sulphur decreased the particle size. Moreover, it was indicated that the reduced d50 value at increased %C and %S may be related to a decreased viscosity and surface tension respectively. An alternative mechanism could be that raised superheats at increased carbon contents increased the total available time for atomisation. This may also have decreased the particle size. The influence of surface tension and viscosity on the d50 value was further analysed with a theoretical d50 model proposed in a previous work. A reduced viscosity from 4∙9 to 2∙1 mPa s decreased the d50 value with 33%. In addition, the particle size was estimated to decrease with 21% by decreasing the surface tension from 1840 to 900 mN m-1.

  • 23.
    Ragnarsson, Lars
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Ek, Mattias
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Eliasson, Anders
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Ceramics.
    Du, Sichen
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Micro-Modelling.
    Flow pattern in ingot during mould filling and its impact on inclusion removal2010In: Ironmaking & steelmaking, ISSN 0301-9233, E-ISSN 1743-2812, Vol. 37, no 5, p. 347-352Article in journal (Refereed)
    Abstract [en]

    A two-dimensional non-steady state computational fluid dynamic model was employed to gain a basic understanding of the flow in the ingot during casting. The surface velocity was found to be affected by the inlet angle and was found to vary with the casting level. The information of surface velocity was related to the probability of the inclusion removal. Water model experiments were also conducted to help the understanding. The model calculation revealed the same trends as the results of water model experiments. Both computational fluid dynamic data and the physical modelling showed that the inlet angle of 5 degrees currently used in the industry was a good alternative regarding inclusion removal. The present work suggests strongly that the melting shop should try to obtain a liquid or semiliquid film at as early stage as possible in ingot casting.

1 - 23 of 23
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