Change search
Refine search result
1 - 31 of 31
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Forslund, A.
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Simulation of reaction-diffusion between substrate and coating during vapor deposition processes2019In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 64, p. 278-283Article in journal (Refereed)
    Abstract [en]

    This work presents simulations of the solid state diffusion and reactions during deposition processes. Two cases are studied where the diffusion in and between coating and substrate is simulated. The processes simulated are in one case directed vapor deposition of Al and Ni on a precoated nickel-base superalloy, and in the other case chemical vapor deposition aluminization of a nickel-base superalloy. The simulations result in composition and phase-fraction profiles, which are presented and compared with experimental composition profiles. The simulation results are generally in good agreement with the experimental profiles.

  • 2. Hatt, O.
    et al.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Giuliani, F.
    Crawforth, P.
    Wynne, B.
    Jackson, M.
    Predicting Chemical Wear in Machining Titanium Alloys Via a Novel Low Cost Diffusion Couple Method2016In: Procedia CIRP, Elsevier, 2016, p. 219-222Conference paper (Refereed)
    Abstract [en]

    Chemical wear during high speed machining of titanium alloys is a serious problem which affects the surface integrity of both the tool and workpiece. A low cost, novel diffusion couple method is presented which allows for thorough analysis of the tool-workpiece interface at the high temperatures reached during conventional machining operations. X-EDS analysis reveals that no less than seven distinct diffusion zones arise between Ti-6Al-4 V and a WC-Co tool which are home to different phases and reaction species. Loss of cobalt binder coupled with a deficit of carbon results in a brittle η-phase leading to catastrophic fracturing of the tool. DICTRA is employed to thermodynamically model the diffusion mechanisms and verify the X-EDS results.

  • 3.
    Holmström, Erik
    et al.
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Lizarraga, Raquel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Linder, David
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Salmasi, Armin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Wang, Wei
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Kaplan, Bartek
    Sandvik Coromant R&D, SE-12680 Stockholm, Sweden..
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermocalc Software AB, Rasundavagen 18, SE-16967 Solna, Sweden..
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. ppsala Univ, Div Mat Theory, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Wigner Res Ctr Phys, Inst Solid State Phys & Opt, POB 49, H-1525 Budapest, Hungary..
    High entropy alloys: Substituting for cobalt in cutting edge technology2018In: Applied Materials Today, ISSN 2352-9407, Vol. 12, p. 322-329Article in journal (Refereed)
    Abstract [en]

    Cemented carbide, also known as hard metal, is one of the most outstanding composite engineering materials since its commercial introduction in the 1920s. The unique combination of strength, hardness and toughness makes cemented carbides highly versatile materials for the most demanding engineering applications. In their simplest form, these materials are composites of tungsten carbide (WC) grains that are cemented with a ductile metallic binder phase, typically cobalt. However, despite the superiority of Co as binder material, there is a long-standing need to find alternative binders due to serious health concerns that have haunted the industry for nearly 80 years. In the present study, we develop a new cemented carbide with a high entropy alloy binder phase (CoCrFeNi) from raw materials to a fully functional, coated and gradient-sintered cutting tool insert. The new hard metal with reduced Co content is designed by using first principles theory and the CALPHAD method. The cutting tool was made by pressing the new hard metal in a standard geometry, sintered to have a thin binder phase enriched surface zone, free from cubic carbides and coated with protective layers of Ti(C,N) and Al2O3. The resulting cutting insert was tested in a real machining operation and compared to a state-of-the-art reference that had Co as binder phase. The cutting tool made of the newly developed cemented carbide has an exceptionally high resistance against plastic deformation at all tested cutting speeds in the machining test, outperforming the reference insert, which shows a linear increase in edge depression when the cutting speed is increased. This result opens up the possibility to utilize the unique properties of high entropy alloys for industrial applications, in particular, as binder phase in new cemented carbides.

  • 4.
    Larsson, Henrik
    KTH, Superseded Departments, Materials Science and Engineering.
    A Random Walk Approach Towards 3D-Modelling of Nucleation, Growth and Coarsening of Precipitates in Steel2003In: IF Steels 2003: international forum for the properties and application of IF steels / [ed] Takechi, H, Iron and Steel Institute of Japan , 2003, p. 268-Conference paper (Other academic)
  • 5.
    Larsson, Henrik
    KTH, Superseded Departments, Materials Science and Engineering.
    Internal oxidation processing: New alloys and new simulation techniques2004Doctoral thesis, comprehensive summary (Other scientific)
    Abstract [en]

    Nitriding and oxidising treatments of alloys for toolingpurposes have been investigated both experimentally andtheoretically. Specimens prepared by a combination of differentprocessing steps are investigated by light-optical, scanningand transmission electron microscopy and hardness measurments.The bounds of carbon and nitrogen concentration profiles duringnitriding are obtained from simulations using the DICTRA code.As a result, a new processing route to produce oxide-dispersediron-base alloys with large volume fraction of carbides issuggested.

    On the theoretical side the methods based on the random walktechnique have been investigated and developed further. The newmethods have been applied to study a vide range of phenomenae.g. internal oxidation, diffusion in inhomogeneous media,phase transformations and formation of porosity due to theKirkendall effect in welded joints. Probability distributionsare introduced to replace random number generators in order toincrease computational efficiency. A general method to simulatediffusional phase transformations in multicomponent systems isdeveloped and applied to ternary alloys.

     

  • 6.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Simulation of phase transformations using the lattice-fixed frame of reference2005In: Solid-Solid Phase Transformations in Inorganic Material 2005, Vol 2 / [ed] Howe, JM; Laughlin, DE; Lee, JK; Dahmen, U; Soffa, WA, 2005, p. 789-793Conference paper (Refereed)
    Abstract [en]

    A method for simulating diffusion processes directly in the lattice-fixed frame of reference is described. The method does not require any assumptions regarding the conditions at phase interfaces. An example simulation in the Au-Pt system is presented. A fair agreement with experimental data is obtained.

  • 7.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Agren, J.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Simulation of Coupled Carbonitriding and Internal Oxidation of Steel2017In: HTM-JOURNAL OF HEAT TREATMENT AND MATERIALS, ISSN 1867-2493, Vol. 72, no 1, p. 19-24Article in journal (Refereed)
    Abstract [en]

    Carbonitriding and internal oxidation have been simulated simultaneously using the DICTRA homogenization model. The predicted carbon and nitrogen profiles as well as the oxide and nitride phase fraction profiles agree favourably with experimental data obtained from the literature, though some discrepancies exist. The present approach should be a very useful tool in process control and optimization.

  • 8.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Borgenstam, Annika
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Trans-interface diffusivity in the Fe-Ni system2007In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 56, no 1, p. 61-64Article in journal (Refereed)
    Abstract [en]

    The trans-interface diffusivity in the Fe-Ni system has been estimated by fitting simulations to experimental data. For diffusion across the alpha/gamma phase boundary, the mobility of species divided by an interfacial thickness of 1 nm, M-k/delta, is approximately 5% of the phase interface mobility M-int at 873 K and 15% at 973 K.

  • 9.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Engstrom, A.
    A homogenization approach to diffusion simulations applied to alpha+gamma Fe-Cr-Ni diffusion couples2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 9, p. 2431-2439Article in journal (Refereed)
    Abstract [en]

    The diffusion of Fe, Cr and Ni in one dimension in and between one- and two-phase alpha/gamma regions was simulated using independently assessed thermodynamic and kinetic data. Simulation results compare favourably with experimental Tesults obtained previously by one of the present authors (A. Engstrom). For example, the formation of a gamma layer between an alpha and a gamma + alpha region is correctly predicted. Neither phase interfaces nor individual phases are explicitly considered; instead, locally averaged kinetic properties are used and locally minimized Gibbs energy is assumed.

  • 10.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Erni, R
    Nordberg, L-O
    Ågren, John
    KTH, Superseded Departments, Materials Science and Engineering.
    Processing route to an oxide dispersed iron/carbide composite2004In: International journal of refractory metals & hard materials, ISSN 0958-0611, E-ISSN 2213-3917, Vol. 22, no 4-5, p. 159-167Article in journal (Refereed)
    Abstract [en]

    A new combination of techniques which should make it possible to produce oxide dispersed alloys by internal oxidation is suggested. The new technique has been used to produce a prototype alloy with a ferritic matrix containing fine (10-20 nm) oxides as well as a large volume fraction of carbides (about 40%). The microstructure indicates that it would be possible to produce an iron-base hard material with improved hot hardness. The technique is based upon an intermetallic starting material and utilises powder metallurgy and attrition ball milling.

     

  • 11.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermocalc Software, SE-11364 Stockholm, Sweden.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermocalc Software, SE-11364 Stockholm, Sweden.
    A scheme for more efficient usage of CALPHAD data in simulations2015In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 50, p. 1-5Article in journal (Refereed)
    Abstract [en]

    A method is suggested that allows thermodynamic data to be dynamically stored and retrieved. The purpose of the method is to reduce computer simulation time when Calphad type databases are being used. Some test simulations are presented and these indicate that simulations can be made to run 5-40 times faster without any significant loss of accuracy.

  • 12.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Höglund, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Multiphase diffusion simulations in 1D using the DICTRA homogenization model2009In: Calphad, ISSN 0364-5916, E-ISSN 1873-2984, Vol. 33, no 3, p. 495-501Article in journal (Refereed)
    Abstract [en]

    A model for multiphase simulations in 1D previously reported in [H. Larsson, A. Engstrom, Acta Mater. 54 (2006) 2431] has been further developed and incorporated in the DICTRA software. The model is based on the assumption of local equilibrium and locally averaged kinetic properties, which computationally transforms the problem into a single-phase diffusion process. The applicability of the model is discussed and example simulations are presented.

  • 13.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Jonsson, T.
    Naraghi, R.
    Gong, Y.
    Reed, R. C.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Oxidation of iron at 600 degrees C - experiments and simulations2016In: Materials and corrosion - Werkstoffe und Korrosion, ISSN 0947-5117, E-ISSN 1521-4176Article in journal (Refereed)
    Abstract [en]

    Pure iron has been oxidized at 600°C and 1bar in dry O2 (oxygen partial pressure 0.05, bal. N2) and the mass gain as well as the thicknesses of the individual oxide phases have been measured. The oxidation process has been simulated using a modified version of the homogenization model as implemented in Dictra; this has helped to rationalize the kinetics of oxide scale formation and in particular the evolution of the hematite (Fe2O3), magnetite (Fe3O4), and wustite (FeO) which form. Independently assessed thermodynamic and kinetic Calphad databases are needed for the calculations; details of these are given. Reasonable agreement between simulation results and experimental data is obtained, though it is concluded that the large influence of grain boundary diffusion on the oxidation rate needs further consideration.

  • 14.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Reed, R. C.
    On the numerical simulation of diffusion-controlled reactions under local equilibrium conditions2008In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 56, no 15, p. 3754-3760Article in journal (Refereed)
    Abstract [en]

    To estimate the interfacial velocity in a multicomponent moving boundary problem, existing procedures require an interative technique too be used if a sharp interface methods is employed. The need to use an interactive technique can cause convergence problems; these become more frequent as more components are added. In this paper, two new methods are suggested which allow the velocity of a phase interface to be evaluated directly from the fluxes of the components Wider the assumption of local equilibrium. The methods assume that the interface has a fixed width in which the incoming and outgoing components are distributed in a way that moves the interface while maintaining local equilibrium. Example simulations are presented and results are ill good agreement with established front-tracking simulation software (DICTRA) moreover. the superior convergence of the new methods is demonstrated .

  • 15.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Schwind, M
    Ågren, John
    KTH, Superseded Departments, Materials Science and Engineering.
    A cellular automata treatment of internal oxidation2000In: Proc. Int. Conf. Mass and Charge Transport in Inorganic Materials: Fundamentals to Devices, Lido di Jesolo, Italy, 2000 / [ed] P Vincenzini, V Buscaglia, Faenza (Ravenna): Techna , 2000, p. 647-652Conference paper (Other academic)
  • 16.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Strandlund, H.
    Hillert, Mats
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Unified treatment of Kirkendall shift and migration of phase interfaces2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 4, p. 945-951Article in journal (Refereed)
    Abstract [en]

    A recent treatment of diffusion in a lattice-fixed frame of reference, which can predict the Kirkendall shift, is modified to be applicable also to the migration of phase interfaces. The net flux across a reference point in the lattice, yielding the Kirkendall shift, as well as the net flux across a phase interface, yielding its migration, are obtained from the same flux equation. Numerical calculations are presented and demonstrate that the method gives expected results. The strength of the method is that it is not based on the assumption of local equilibrium and it is capable of automatically yielding close to local equilibrium conditions except at high supersaturations. There it describes an increasing deviation from local equilibrium as the initial alloy composition is moved inside the one-phase field for the new phase. The interaction of a migrating phase interface and Kirkendall markers is also illustrated.

  • 17.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments, Materials Science and Engineering.
    A random-walk approach to diffusion controlled growth2003In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 49, no 6, p. 521-526Article in journal (Refereed)
    Abstract [en]

    The new method does not require formulation of any special conditions at the moving phase interface. Although only binary systems are treated at present an extension to any number of components seems straightforward. A good agreement with conventional front tracking techniques (DICTRA) is found.

  • 18.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments, Materials Science and Engineering.
    A random-walk approach to diffusion controlled growth II: A distribution function solution2004In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 51, no 2, p. 137-140Article in journal (Refereed)
    Abstract [en]

    Earlier work on simulations of diffusion controlled transformations based on a random-walk technique is extended; a random-walk simulation of a transformation in a ternary system and a new method based on distribution functions are presented. As before, no special assumption regarding the state of the phase interface is required.

  • 19.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Ågren, John
    KTH, Superseded Departments, Materials Science and Engineering.
    A random-walk investigation of the diffusive properties of inhomogenous mediaIn: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550Article in journal (Refereed)
  • 20.
    Larsson, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Combined probability distributions of random-walks: A new method to simulate diffusion processes2005In: Computational materials science, ISSN 0927-0256, E-ISSN 1879-0801, Vol. 34, no 3, p. 254-263Article in journal (Refereed)
    Abstract [en]

    Two related methods to simulate diffusion processes are presented. Both are based on conceiving diffusion as a random-walk process. Several example simulations are presented: single phase diffusion couples, diffusion controlled growth and prediction of Kirkendall porosity. Comparisons with experimental results and simulation software based on established technique (DICTRA) show good agreement with results obtained from the presented models.

  • 21.
    Larsson, Henrik
    et al.
    KTH, Superseded Departments, Metallurgy.
    Ågren, John
    KTH, Superseded Departments, Metallurgy.
    Gas nitriding of high vanadium steels: Experiments and simulations2004In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 35A, no 9, p. 2799-2802Article in journal (Refereed)
    Abstract [en]

    Four experimental high vanadium alloys were gas nitrided in an ammonia-nitrogen atmosphere. The microstructure and concentration gradients have been investigated by means of several techniques. The nitriding process has been tentatively simulated using the DICTRA software. A precise process simulation does not seem possible at present; the reason for this is discussed. Instead, bounds for the carbon and nitrogen concentration profiles were obtained by applying different simulation conditions.

  • 22. Morral, J. E.
    et al.
    Pan, X. M.
    Zhou, N.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Wang, Y. Z.
    Singularities in multiphase diffusion couples2008In: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 58, no 11, p. 970-972Article in journal (Refereed)
    Abstract [en]

    Singularities are not normally expected in diffusion couple data; however, they can occur in certain multiphase concentration profiles and diffusion paths. The following work reviews the theoretical reason why singularities form and gives two different computer simulations that support the theoretical predictions. In addition, a correction is given to a previous paper in which artifacts created by modeling software were inadvertently reported as diffusional singularities.

  • 23.
    Salmasi, Armin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blomqvist, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Sandvik Coromant R&D.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Computational Thermodynamics. Thermo-Calc AB.
    Geometry effects during sintering of graded cemented carbides: Modelling of microstructural evolution and mechanical properties2019In: Results in Materials, ISSN 2590-048X, Vol. 1, article id 100008Article in journal (Refereed)
    Abstract [en]

    Cemented carbides with mesoscopically non-homogeneous properties by design represent a potential to enhanceperformance in metal cutting and rock drilling. Development of in-homogeneous structured hard materialsthrough an ICME approach requires a thorough understanding of diffusion kinetics during solid and liquid statesintering. In this work, we used thermodynamics and diffusion kinetics modelling tools to predict the micro-structure and resulting properties of cemented carbide composites. First, we designed and gradient sintered two(WC-TiCN-Co) cemented carbides with different nitrogen to titanium ratios. Second, we reproduced the experi-mental results in 2D by means of thermodynamic and kinetic simulations. In the last step we calculated fracturetoughness KIC, and Vickers hardness of cemented carbides. The agreement between simulations and experimentalresults is fair and acceptable

  • 24.
    Strandlund, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Larsson, Henrik
    KTH, Superseded Departments, Materials Science and Engineering.
    Diffusion process simulations - an overview of different approaches2004In: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Vol. 233, p. 97-113Article in journal (Refereed)
    Abstract [en]

    Some different approaches to diffusion process simulations are briefly presented. Their varying areas of applicability are discussed. Example simulations using the phase-field method, the DICTRA software, and random-walk based approaches are presented.

  • 25.
    Strandlund, Henrik
    et al.
    KTH, Superseded Departments, Materials Science and Engineering.
    Larsson, Henrik
    KTH, Superseded Departments, Materials Science and Engineering.
    Prediction of Kirkendall shift and porosity in binary and ternary diffusion couples2004In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 52, no 15, p. 4695-4703Article in journal (Refereed)
    Abstract [en]

    Computer simulations are applied to simulate the Kirkendall shift and porosity in binary and ternary alloys. Three different computational methods, based on different assumptions, are used together with assessed thermodynamic and kinetic data. The simulation results show good agreement compared with experimental data.

  • 26.
    Strandlund, Henrik
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Simulation of diffusion by direct solution in the lattice-fixed frame of reference2006In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 37A, no 6, p. 1785-1789Article in journal (Refereed)
    Abstract [en]

    A new simulation method for bulk diffusion that automatically takes the Kirkendall effect into account is presented. Example simulations are presented and compared with experimental data and DICTRA simulations.

  • 27.
    Tian, Liyun
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Lizárraga, Raquel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Holmström, E.
    Vitos, Levente
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Uppsala University, Sweden.
    A first principles study of the stacking fault energies for fcc Co-based binary alloys2017In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 136, p. 215-223Article in journal (Refereed)
    Abstract [en]

    The stacking fault energy is closely related to structural phase transformations and can help to understand plastic deformation mechanisms in materials. Here we perform first principles calculations of the stacking fault energy in the face centered cubic (fcc) Cobalt-based binary alloys Co1−x Mx, where M = Cr, Fe, Ni, Mo, Ru, Rh, Pd and W. We investigate the concentration range between 0 and 30 at.% of the alloying element. The results are discussed in connection to the phase transition between the low-temperature hexagonal close packed (hcp) and the fcc structures observed in Co and its alloys. By analyzing the stacking fault energies, we show that alloying Co with Cr, Ru, and Rh promotes the hcp phase formation while Fe, Ni and Pd favor the fcc phase instead. The effect of Mo and W on the phase transition differs from the other elements, that is, for concentrations below 10% the intrinsic stacking fault energy is lower than that for pure fcc Co and the energy barrier is higher, whereas above 10% the situation reverses. We carry out also thermodynamic calculations using the ThermoCalc software. The trends of the ab initio stacking fault energy are found to agree well with those of the molar Gibbs energy differences and the phase transition temperature in the binary phase diagrams and give a solid support for the phase stability of these alloys.

  • 28.
    Walbrühl, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blomqvist, Andreas
    Thomen, Aurélien
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effective diffusion in cemented carbide systems: Geometrical effect of the labyrinth factorManuscript (preprint) (Other academic)
    Abstract [en]

    In cemented carbides the effective diffusivities are associated with the carbides acting as obstacles that increase the diffusion distance, thus altering the overall diffusion in the composite. From an industrial point of view, the prediction of the surface gradient formation is important to develop state-of-the-art cemented carbide cutting tools and require an understanding of the liquid binder diffusivities and the effective diffusion reduction at typical sintering temperatures where the binder is molten. Recently, a full description of the diffusivities in the liquid binder has become available and the focus of the present work is thus the effective diffusion reduction. Isotope diffusion couple experiments have been successfully performed to investigate the effective diffusion in a WC-Ni liquid binder-carbide composite material, i.e. a cemented carbide. The 58Ni isotope diffusion profiles have been measured with Secondary Ion Mass Spectroscopy (SIMS) and the results have been compared to DICTRA simulations using an updated kinetic database. The agreement between the experimental and simulated diffusion profiles is excellent showing that the theoretical geometrical limit, simulated with the upper Hashin-Shtrikman bound, is obeyed in simple cemented carbide systems. For complex cemented carbide systems, where gradient sintering is relevant, the effective diffusion is insufficiently explained by the geometrical reduction.

  • 29.
    Walbrühl, Martin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Ågren, John
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Blomqvist, A.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    ICME guided modeling of surface gradient formation in cemented carbides2018In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 72, p. 33-38Article in journal (Refereed)
    Abstract [en]

    Structural gradients are of great interest for state-of-the-art cemented carbides used in metal cutting applications. The gradient growth during sintering is controlled by the fundamental aspects of diffusion, thermodynamics and phase equilibria in systems with multiple components and phases. With the demand for binder alternatives to Co, there is a need for understanding the diffusion and thermodynamics in new materials systems. Materials development guided by ICME (Integrated Computational Materials Engineering) is a new approach that accelerates the design of tailor-made materials, assisting us to find and optimize prospective binder candidates using computational tools. The role of the thermodynamic descriptions will be briefly discussed but this work focuses on a better kinetic description. Models based on cemented carbide microstructures and fundamental understanding of kinetics will allow for a more general use of simulations of gradient formation. The diffusion of elements during sintering mainly occurs in the liquid binder phase, with the solid WC and gamma phases acting as an effective labyrinth, hindering diffusion. In this work, the liquid mobilities and the effective labyrinth factor is studied for traditional and alternative binders by combing ab initio molecular dynamics and diffusion couple experiments with CALPHAD modeling. 

  • 30.
    Wang, Wei
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Dept Chemical Engineering, Northeast Electric Power University, Jilin, 132012, China.
    Hou, Ziyong
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Lizarrága, Raquel
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tian, Ye
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Babu, Prasath
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Holmström, Erik
    Coromant R & D, SE-12680, Stockholm, Sweden.
    Mao, Huahai
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. Thermo-Calc Software, Råsundav. 18, SE-16767, Solna, Sweden.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy. Thermo-Calc Software, Råsundav. 18, SE-16767, Solna, Sweden.
    An experimental and theoretical study of duplex fcc+hcp cobalt based entropic alloys2019In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 176, p. 11-18Article in journal (Refereed)
    Abstract [en]

    Martensitically formed duplex fcc + hcp Co-based entropic alloys have been investigated both experimentally and theoretically. Theoretical predictions are in good agreement with experimental observations. A fair correlation is found between calculated driving forces for a partitionless fcc→hcp transformation and experimentally obtained phase fractions.

  • 31. Warnken, N.
    et al.
    Larsson, Henrik
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Physical Metallurgy.
    Reed, R. C.
    Coupled modelling of solidification and solution heat treatment of advanced single crystal nickel base superalloy2009In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 25, no 2, p. 179-185Article in journal (Refereed)
    Abstract [en]

    Two numerical models to simulate microsegregation and phase formation during directional solidification and subsequent solution heat treatment of an advanced experimental ruthenium containing single crystal nickel base superalloy are tested and compared. The first method is based on a one-dimensional front tracking for the primary solidification and a homogenisation method for the final stages of solidification as well as for the solution heat treatment. Calculations for this model are carried out in one-dimension using cylindrical coordinates. The second is based upon the phase field method, applied to solidification and subsequent solution heat treatment, where calculations are carried out in two-dimension. Both models are coupled to thermodynamic and kinetics databases modelled according to the CALPHAD method. A concept of computer based optimisation of solution heat treatments is proposed. The results show that both methods are capable of handling the complexity of contemporary superalloys, and realistic results are obtained from both models.

1 - 31 of 31
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • harvard1
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf