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  • 1.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, T.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    On Liquid Metal Wetting of Casting Rings for DC Casting2015In: Light Metals 2015 / [ed] Hyland, M., Wiley-Blackwell, 2015, p. 855-863Chapter in book (Refereed)
    Abstract [en]

    During air-slip direct chill casting of aluminum alloys, uneven or low air pressure areas at the surface of the porous graphite ring mold, can cause the metal to stick to the graphite ring and produce traces along the billets called vertical drags (VD). To prevent this type of defect, it would be an advantage to decrease the wettability of the graphite ring. It has been shown that nanostructured surfaces can have hydrophobic properties, and a question is whether the same effect can be achieved for molten metals. A Ti02 nanowire structure is proposed to cover the casting ring, and the wetting behavior of such a structure has been studied, and compared to the wetting at a regular graphite ring surface by the dispensed sessile drop method. The results showed that the nanostructured surface very strongly de-wets metal droplets.

  • 2.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Influence of Heat Treatment on the Surface Structure of 6082 Al Alloys2017In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 48A, no 10, p. 5085-5094Article in journal (Other academic)
    Abstract [en]

    The β-Al5FeSi intermetallic phase and coarse Mg2Si particles have negative effects on extrudability and workability of 6xxx Al alloys billets. To achieve extruded products with a high surface quality, the as-cast billets are heat-treated before extrusion. During heat treatment, the undesired intermetallic particles, i.e., β-AlFeSi platelets are transformed to rounded α-Al(FeMn)Si intermetallic phases. Although the heat treatment of the bulk areas of the 6xxx Al alloys has been the focus of many previous studies, the process of phase transformation at the very surface has not been paid the same attention. In this study, microstructures of a homogenized billet of a 6082 alloy at the area very close to the surface were investigated. By comparing the X-ray diffraction patterns (XRD) of heat-treated samples as a function of different holding times, the gradual phase transformations could be followed, and using GDOES and map analysis by EDX, the alloying elemental redistribution was analyzed. Partial remelting and porosity growth was detected, and transformation rates were faster than in bulk material and from what is known from industrial processes.

  • 3.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    On Liquid Metal Wetting of Casting Rings for DC Casting2015In: TMS Light Metals / [ed] Margaret Hyland, Warrendale: Minerals, Metals & Materials Society, 2015, Vol. 2015-January, p. 859-864Conference paper (Refereed)
    Abstract [en]

    During air–slip direct chill casting of aluminum alloys, uneven or low air pressure areas at the surface of the porous graphite ring mold, can cause the metal to stick to the graphite ring and produce traces along the billets called vertical drags (VD). To prevent this type of defect, it would be an advantage to decrease the wettability of the graphite ring.  It has been shown that nanostructured surfaces can have hydrophobic properties, and a question is weather the same effect can be achieved for molten metals. A TiO2 nanowire structure is proposed to cover the casting ring, and the wetting behavior of such a structure has been studied, and compared to the wetting at a regular graphite ring surface by the dispensed sessile drop method. The results showed that the nanostructured surface very strongly dewetting metal droplets.

  • 4.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Surface formation in direct chill (DC) casting of 6082 aluminium alloys2016In: IOP Conference Series: Materials Science and Engineering, Institute of Physics Publishing (IOPP), 2016, Vol. 117, no 1, article id 012038Conference paper (Refereed)
    Abstract [en]

    Surface defects in aluminium billet production are a real problem for the subsequent extrusion procedure. Extrusion productivity can be influenced by the surface properties, which is defined as surface appearance, surface segregation zone depth and large Mg2Si and β-particles (Al5FeSi). In this research the surface formation during DC casting of 6082 aluminium billets produced by the air slip technology is studied. The surface microstructures of 6082 aluminium alloys with smooth and wavy surface appearances were investigated, including segregation zone depths and phase formation. The results were discussed based on the exudation of liquid metal through the mushy zone. The specific appearance of the wavy surface of 6082 alloys was correlated to how the oxide skin adheres to the underlying mushy zone and coupled to the dendritic coherency and surface tension of the skin. The occurrence of different phases at the very surface and in the layer just below was explained by variations in solidification directions and subsequent segregation patterns.

  • 5.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Surface structure formation in direct chill (DC) casting of al alloys2014In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 66, no 5, p. 700-710Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to increase the understanding of the surface zone formation during direct chill (DC) casting of aluminum billets produced by the air slip technology. The depth of the shell zone, with compositions deviating from the bulk, is of large importance for the subsequent extrusion productivity and quality of final products. The surface microstructures of 6060 and 6005 aluminum alloys in three different surface appearances - defect free, wavy surface, and spot defects - were studied. The surface microstructures and outer appearance, segregation depth, and phase formation were investigated for the mentioned cases. The results were discussed and explained based on the exudation of liquid metal through the mushy zone and the fact that the exudated liquid is contained within a surface oxide skin. Outward solidification in the surface layer was quantitatively analyzed, and the oxide skin movements explained meniscus line formation. Phases forming at different positions in the segregation zone were analyzed and coupled to a cellular solidification in the exudated layer.

  • 6.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cieslar, M.
    Faculty of Mathematic and Physics, Charles University, Prague, Czech Republic.
    In-Situ Study of Phase Transformations during Homogenization of 6005 and 6082 Al Alloys2017In: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 725, p. 504-509Article in journal (Refereed)
    Abstract [en]

    Intermetallic β-Al5FeSi phase and coarse Mg2Si particles have negative effects on extrudability and workability of 6xxx Al alloy billets. To achieve extruded products with a high surface quality as-cast billets are therefore heat-treated before extrusion. During heat treatment the undesired intermetallic particles, i.e., β-AlFeSi platelets, are transformed to a rounded α-Al(FeMn)Si intermetallic phase. This transformation was studied in-situ by TEM for 6005 and 6082 Al alloys. It was observed that the Mg2Si particles precipitate in the Al matrix at about 250 °C; this precipitation also occurred at the edge and faces of beta intermetallic particles, and the Mg2Si particles were the preferred sites for α-Al(FeMn)Si particle nucleation. The transformation proceeded faster and at lower temperatures, 350–450 °C, than what has been reported earlier for homogenization studies of bulk samples and industrial billets. This could be associated with the thin characteristic of used samples in TEM giving contribution from fast surface diffusion, but it was also concluded that the phase boundary layer diffusion was important for the understanding of how the transformations proceed.

  • 7.
    Bayat, Nazlin
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Cieslar, M.
    Charles University, Prague, Czech Republic.
    In-Situ Study of Phase Transformations during Homogenization of 6060 and 6063 Al Alloys2019In: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 130, p. 165-171Article in journal (Refereed)
  • 8.
    Carlberg, Torbjorn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Jarfors, Anders E. W.
    School of Engineering, Jönköping University, 55111 Jönköping, Sweden .
    On Vertical Drag Defects Formation During Direct Chill (DC) Casting of Aluminum Billets2014In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 45, no 1, p. 175-181Article in journal (Refereed)
    Abstract [en]

    During air-slip direct chill casting of aluminum billets, one of the major defects occurring includes traces along the billet called vertical drags (VDs). If the VDs are too deep or too many, then they cause scraping of the billets. As in the subsequent extrusion process, the surface quality is known to impair both the productivity and quality of the profiles. In cast-house practice, many theories circulate about the causes of VD defects and how to avoid them, but in the literature, no thorough treatments have been made to explain this phenomenon. In the current study, the outer appearance, structure around, and compositions at the defects are analyzed. A theory for the formation of the defects, their cause, and how their appearance is coupled to different alloy types is presented. The segregation in the vicinity of the defects is discussed based on deformation of semisolid materials and coupled to Reynolds dilatancy in granular materials. The theory can explain differences between 6063 and 6005 alloys.

  • 9.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    A Review of Radial Segregation in Crystal Growth during Microgravity2006In: Progress in crystal growth and characterization of materials, ISSN 0960-8974, E-ISSN 1878-4208, Vol. 52, no 3, p. 213-222Article, review/survey (Refereed)
    Abstract [en]

    This review describes radial segregation results from crystal growth experiments in microgravity, together with their corre-sponding theoretical treatments. The paper is structured in terms of the different factors influencing radial segregation during crystal growth, such as: curved growth interfaces, variations in boundary layer thicknesses, weak convection, facets and magnetic fields. In a number of experiments considerably stronger radial segregation occurs in space than is normally observed on earth. The theoretical treatments lead to a sound understanding of all of the results. Possible ways to avoid the problem, such as the application of magnetic fields, are outlined.

  • 10.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Experimental Study of Radial Segregation Caused by Weak Convection2005In: Microgravity, science and technology, ISSN 0938-0108, E-ISSN 1875-0494, Vol. 15, no 1, p. 35-39Article in journal (Refereed)
    Abstract [en]

    Under conditions of weak convection in the liquid during metal solidification and crystal growth, large chemical inhomogeneities can occur due to insufficient mixing of the melt. In this project a series of experiments with increasing melt flow, driven by thermo-capillary forces, have been performed in a Get Away Special flight. The level of convection was evaluated quantitatively from analysis of axial segregation profiles. As expected a significantly stronger radial segregation has occurred in the space grown material compared to ground based reference experiments. It was also found that there was a shift of the position of maximum concentration when the flow was increased. Unexpected axial solute maxima were also revealed in the space samples. A comparison was made to numerical simulations, and good correlations were found to first order effects.

  • 11.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Radial Segregation during Microgravity Experiments: Presented at The International Conference on Advances in Solidification Processing, Stockholm, Sweden, June 20052005Conference paper (Other scientific)
    Abstract [en]

    Under conditions of weak convection in the liquid during metal solidification and crystal growth, large chemical inhomogeneities can occur due to insuffi-cient mixing of the melt. In this project a series of experiments with increasing melt flow, driven by thermo-capillary forces, have been performed in a Get Away Special flight. The level of convection was evaluated quanti-tatively from analysis of axial segregation profiles. As expected a significantly stronger radial segre-gation has occurred in the space grown mate-rial compared to ground based reference experiments. It was also found that there was a shift of the position of max-imum concentration when the flow was in-creased. Unexpected axial solute maxima were also revealed in the space samples. A comparison was made to numerical simulations, and good correla-tions were found to first order effects.

  • 12.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Silicon crystal formation during DC casting of aluminium-silicon alloys2009In: TMS Light Metals 2009, Minerals, Metals & Materials Society, 2009, p. 837-841Conference paper (Refereed)
    Abstract [en]

    The formation of polyhedral silicon crystals in aluminium 7-8% silicon alloys has been studied in industrial ingots. It was found that the nucleation temperature and the cooling rate were important factors influencing the amount and size of the polyhedral crystals. To avoid large particles in the as cast material early nucleation have to be suppressed and the phosphorous content should be kept low. Modeling of diffusion-controlled growth of the silicon phase in this type of aluminium-silicon alloys shows how the nucleation temperature influences the morphology of the precipitated silicon.

  • 13.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Silicon Particle Precipitation during DC Casting of Al-Si Clad Alloys2010In: Materials Science Forum, Trans Tech Publications Inc., 2010, p. 307-313Conference paper (Refereed)
    Abstract [en]

    The formation of polyhedral silicon crystals in aluminium 7-9% silicon alloys has been studied both in industrial ingots and in simulation experiments in a Bridgman furnace. It was found that the nucleation temperature and the cooling rate were important factors influencing the amount and size of the polyhedral crystals. To avoid large particles in the as cast material early nucleation have to be suppressed and the phosphorous content should be kept low. Modelling of diffusion-controlled growth of the silicon phase in this type of aluminium-silicon alloys shows how the nucleation temperature influences the morphology of the precipitated sili¬con.

  • 14.
    Carlberg, Torbjörn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Bayat, Nazlin
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Erdegren, Mikael
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Surface Segregation and Surface Defect Formation During Aluminum Billet Casting2015In: Transactions of the Indian Institute of Metals, ISSN 0972-2815, E-ISSN 0975-1645, Vol. 68, no 6, p. 1065-1069Article in journal (Refereed)
    Abstract [en]

    In this paper the surface zone formation during direct chill casting of aluminum billets, produced by the air slip technology, is discussed. The shell zone depth and compositions have been quantitatively studied, and the surface microstructures of 6060, 6005 and 6082 alloys are compared and coupled to surface appearances. The understanding of the results is based on the exudation of liquid metal through the mushy zone and the fact that the exudate liquid is contained within a surface oxide skin, and the oxide skin movements are coupled to various surface appearances. The major defects that occur during billet castings are different kinds of vertical drags or horizontal bandings, also called lapping. The structures coupled to these defects and theories for their formation are discussed.

  • 15.
    Carlberg, Torbjörn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Jaradeh, Majed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Kamgou Kamga, H.
    Solidification Studies of Automotive Heat Exchanger Materials2006In: JOM: The Member Journal of TMS, ISSN 1047-4838, E-ISSN 1543-1851, Vol. 58, no 11, p. 56-61Article in journal (Refereed)
    Abstract [en]

    Based on the aluminium alloy AA 3003 different modifications of that alloy family have been studied to improve and tailor the properties of the material for its applications in automotive heat exchangers. Laboratory techniques have been applied to simulate industrial DC-casting, together with some basic solidification studies. The results are coupled to structures observed in industrial size ingots and discussed in terms of structure property relations.

  • 16.
    Carlberg, Torbjörn
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Winkler, C.
    Amberg, G.
    Weak Convection Influencing Radial Segregation2000In: European Space Agency, (Special Publication) ESA SP, 2000, Vol. 454 I, p. 431-436Conference paper (Other academic)
    Abstract [en]

    The influence of weak convection, caused by surface tension forces, on radial segregation occuring in crystals grown under microgravity conditions is studied in a project involving both numerical simulations and space experiments. The geometry studied is a Bridgman configuration with a partially coated surface. Small slots in the coating give free surface in a controlled way, and the free surface area is the parameter in the investigation. The experiments will be performed in a GAS module, which will be flown in the beginning of year 2001. The paper presents the experimental technique in detail as well as some results obtained during the development phase. Numerical simulations have been performed and results of how the radial segregation varies with the convection level will be presented. The project is the first phase of a research program, which will continue with experiments in the ISS.

  • 17. Do-Quang, Minah
    et al.
    Amberg, G
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Three-dimensional Modeling of Radial Segregation due to Weak Convection2004In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 269, no 2-4, p. 454-463Article in journal (Refereed)
    Abstract [en]

    A comprehensive three-dimensional, time-dependent model of heat, momentum and solute transfer during solidification is carried out to illustrate the influence of weak convection, caused by surface tension forces, on radial dopant segregation occurring in crystal growth under micro-gravity conditions. 3D adaptive finite element method is used in order to simulate the motion and deformation of the solidification interface. The geometry studied is a Bridgman configuration with a partly coated surface. The small slots in the coating gives a free surface in a controlled way, and is varied in order to alter the Marangom flow. in this study, A comparison is made between the numerical results and the experimental results. A good agreement has been observed for the effective distribution coefficient k(eff) and for the radial segregation Deltac'. The radial dopant segregation is affected by weak convection.

     

  • 18.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Carlberg, T.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hellström, Lisbeth M.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Quality Technology and Management, Mechanical Engineering and Mathematics.
    Gregersen, Øyvind Weiby
    NTNU - Norges teknisk-naturvitenskapelige universitet.
    Method for producing and processing wood chips [Förfarande för framställning av flis]2011Patent (Other (popular science, discussion, etc.))
    Abstract [en]

    This patent application describes a method to produce wood chips with the intention of reducing the energy consumption in the subsequent process steps for pulp production. With the present method wood chipping is done in a wood chipper where the chipping tool (3) has an angle γ (4) within the interval of 75° to 105° between the fibre direction of the log and the side of the tool which faces the chip (2). Angles in this interval will cause an axially directed compression of the chip which will cause a cracking of the wood during chipping.

  • 19.
    Engstrand, Per
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Chemical Engineering.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hellström, Lisbeth
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Sandström, Peter
    SCA Reseach.
    Liden, Joar
    SCA Ortviken.
    Söderberg, Mats
    SCA Research.
    Mats, Egnell
    Andritz Iggesund Tools.
    Improved refining energy efficiency in thermo-mechanical pulping by means of collimated wood chipping – from solid mechanics to full scale evaluation2016In: PaperWeek Canada 2016 Conference February 1 to 5, 2016, Montreal: Technical Track Program / [ed] Greg Hay, 2016Conference paper (Refereed)
    Abstract [en]

    The wood chipping process was never optimized with regard to high yield pulping processes as thermomechanical pulping (TMP) and chemithermomechanical pulping (CTMP). It is generally believed that wood chips for pulping should be produced in such a way that the degree of damage is minimized and that the chip dimensional distribution should be as narrow as possible. Since the TMP and CTMP processes were developed in the 60-ies and 70-ies, compression screw as well as roll nip equipment have been developed to pretreat wood chips as a way to reduce refining energy consumption to given fiber and pulp properties and also in order to improve impregnation. The general conclusions are that a combination of shear and compression in the tangential or radial direction of the wood initiates cracks that later in the refiner will enhance and optimize fiber separation and also fiber property development. The idea with the collimated chipping technology is to utilize the wood chipper as a tool, combining cutting of wood logs to wood chips with a pretreatment of the chips by creating cracks that would enhance fiber separation, fiber surface development as well as chip-impregnation. In this case the compression is performed in the wood fiber direction, in which direction wood actually is weakest when it comes to compression induced cracking. The maximization of the amount of cracks in wood-chips is performed by optimizing the knife angle (or spout angle) in the chipper, to what we call collimated chipping (according to a patent owned by CCT AB). This presentation describes a theoretical background and two demonstration scale studies performed by SCA Forest Products at their Ortviken mill. One conclusion drawn, based on two-month test period with three weeks of collimated chipping, was that specific refining energy reduction was around 100 kWh/adt of the 1400 kWh/adt used in primary stage double disc refining. Most probably the potential is higher if the whole system is optimized. Tests were performed at constant production rate and energy was reduced by reducing power to constant freeness, leading to similar tensile and light scattering levels. The deliberately increased forces created in the wood chipper by means of an optimized (increased) edge angle caused more problems with knife holder equipment than normally, as well as increased vibrations. These problems will have to be solved for future long-term implementation of the technique.

  • 20. Erdegren, M.
    et al.
    Carlberg, T.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Surface Defects Structures on Direct Chill Cast 6xxx Aluminium Billets2011In: Light Metals 2011, John Wiley & Sons, 2011, p. 675-680Chapter in book (Other academic)
    Abstract [en]

    Surface defects found during air-slip direct chill casting are today a major quality factor for extruded aluminum, as they can cause increased segregation, pores and unwanted precipitations. The surface zone in billets of the aluminium alloys 6063, 6005 and 6082 have been analysed by metallographic methods and by chemical analysis. Surface defects, of the type vertical drags, were investigated and compared to defect free surfaces. Inverse segregation to the surface was quantitatively analysed. The concentration profiles were coupled to the appearance of the defects and to microstructures from corresponding areas. It was shown, for vertical drags on 6005 billet surfaces, that either the segregation depth or the precipitated particles were different from surface areas without defects. For the 6063 alloys on the other hand the vertical drag zones contained different particles than surfaces without defects and the segregation had noticeably increased. © 2011 The Minerals, Metals & Materials Society. All rights reserved.

  • 21.
    Erdegren, Mikael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Modification of mould surfaces for direct chill casting by application of nanostructuresManuscript (preprint) (Other academic)
  • 22.
    Erdegren, Mikael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Surface defects on direct chill as-cast 6XXX aluminum billets2011In: TMS Light Metals, San Diego, CA: The Minerals, Metals, and Materials Society, 2011, p. 675-680Conference paper (Refereed)
    Abstract [en]

    Surface defects found during air-slip direct chill casting are today a major quality factor for extruded aluminum, as they can cause increased segregation, pores and unwanted precipitations. The surface zone in billets of the aluminium alloys 6063, 6005 and 6082 have been analysed by metallographic methods and by chemical analysis. Surface defects, of the type vertical drags, were investigated and compared to defect free surfaces. Inverse segregation to the surface was quantitatively analysed. The concentration profiles were coupled to the appearance of the defects and to microstructures from corresponding areas. It was shown, for vertical drags on 6005 billet surfaces, that either the segregation depth or the precipitated particles were different from surface areas without defects. For the 6063 alloys on the other hand the vertical drag zones contained different particles than surfaces without defects and the segregation had noticeably increased.

  • 23.
    Erdegren, Mikael
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Ullah, Mohammad Wali
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Simulation of surface solidification in direct-chill 6xxx aluminum billets2012In: IOP Conference Series: Materials Science and Engineering, Institute of Physics (IOP), 2012, p. Art. no. 012013-Conference paper (Refereed)
    Abstract [en]

    Using the Bridgman technique, the solidification of aluminum alloys of types 6005, 6063, and 6082, was studied. The solidification process differs both between the alloys and between billet surface and bulk, due to higher concentrations of Fe, Si, Mn and Mg near the surface. Previously determined surface concentrations were used to calculate the Fe, Si, Mn and Mg additions needed for Bridgman experiments that simulate surface region solidification. Microstructures were studied and grain size, secondary dendrite arm spacing, intermetallic particles, segregation, and coarsening were evaluated. The increased alloy element concentrations at the surface were found to influence both the structure coarseness and the kind of intermetallic precipitation. In addition, clear differences could be determined between the alloy types, depending on their pull rate in the furnace.

  • 24.
    Hellström, Lisbeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gregersen, Øyvind
    Department of chemical engineering, NTNU, Norway.
    Collimated chipping technology in order to reduce the energy consumption in mechanical pulping2011In: Proceeding for International Mechanical Pulping Conference, Xi'an, P.R. of China, 2011, p. 457-460Conference paper (Other academic)
    Abstract [en]

    It has recently been shown that it is possible to improve the energy efficiency during first stage TMP (thermomechanical pulp) refining by utilizing a modified chipping method (collimated chipping). A patent application regarding this method has been filed and is pending. The modification consists in that the spout angle i.e. the angle between the fibre direction of the wood specimen and the cutting plane, is increased. This paper reports the differences in properties of IMP refined from chips produced at two different spout angles i.e. 30 and 50 with and without the addition of sodium bisulphite (NaHSO3) to the dilution water. It was found that the specific energy input for a certain CSF (Canadian Standard Freeness) value was lower for chips produced at spout 50 but that the addition of chemicals to the dilution water had no influence on the specific energy value for a given CSF value. However, the tensile index and specific light scattering coefficient was substantially higher for handsheets made of the pulp refined from chips produced at spout angle 50 and with NaHSO3 added compared to handsheets from pulp made from 30 and 50 chips without chemicals added.

  • 25.
    Hellström, Lisbeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Engstrand, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Gregersen, Øyvind
    Department for Chemical Engineering, NTNU, Norway.
    Evaluation Of Collimated Chipping Technology For Reducing Energy Consumption In Mechanical Pulping2012In: Journal of Science & Technology for Forest Products and Processes, ISSN 1927-6311, E-ISSN 1927-632X, Vol. 2, no 3, p. 6-9Article in journal (Refereed)
    Abstract [en]

    It has recently been shown that the energy efficiency during first-stage TMP (thermo-mechanical pulp) refining can be improved using amodified chipping method (collimated chipping), where the angle between the fibre direction of the wood specimen and the cutting plane is increased. This paper reports the differences in properties of TMP refined from wood chips produced at two different spout angles, 30° and 50°, with and without the addition of sodium bisulphite (NaHSO3) to the dilution water. It was found that the specific energy input for a certain CSF (Canadian Standard Freeness) value was lower for chips produced at spout 50°, but that the addition of chemicals to the dilution water had no influence on the specific energy value for a given CSF value. However, the tensile index and specific light-scattering coefficient were substantially higher for handsheets made from the pulp refined from chips produced at spout angle 50° and with NaHSO3 added compared to handsheets from pulp made from 30° and 50° chips without chemicals added.

  • 26.
    Hellström, Lisbeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Strain Distribution in Wood During Chipping2007In: International Mechanical Pulping Conference 2007, TAPPI, 2007, Vol. 1, p. 251-255Conference paper (Refereed)
    Abstract [en]

    To be able to understand more in detail what actually happens during chipping, the strain field in a chip during chipping was studied by means of the Digital Speckle Photography (DSP) technique. In addition to recording the strain field, the load on and displacement of the chipping tool was also recorded. The equipment used in this study was a DSP system, an MTS servo hydraulic testing machine and a specially developed chipping device. Displacement controlled testing was performed with a crosshead speed of 1.0 mm/s. The results are promising but needs some improvement regarding resolution of the digital images in a vicinity of the knife-edge. The cutting speed in this investigation is low in comparison to normal industrial cutting speeds and since wood in general exhibits a viscoelastic material behaviour this might give a slightly different strain field as compared to an industrial chipping process. However, it is believed that using DSP as a tool for studying the deformations during chipping, even under quite restricted conditions, will increase the understanding of the chipping process. The present study is a part of a larger project aimed at a better understanding of the chip formation and wear mechanisms of wood chipping knifes.

  • 27.
    Hellström, Lisbeth
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gulliksson, Mårten
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A laboratory wood chipper for chipping under realistic conditions2011In: Experimental mechanics, ISSN 0014-4851, E-ISSN 1741-2765, Vol. 51, no 8, p. 1309-1316Article in journal (Refereed)
    Abstract [en]

    In order to be able to study the damage mechanisms and in general the mechanisms active when a wood chip is created during the wood chipping process, it is crucial to have access to an experimental equipment in which chips can be produced under realistic conditions. In this paper is presented a laboratory chipper, which has been developed to admit chipping at rates that can be varied in a large interval i.e. at rates ranging from zero to 50 m/s. The knife used to cut the chips is mounted in a knife holder, which is instrumented in such a way that forces in three orthogonal directions can be measured. Since the actual force and the measured force differs due to inertia effects, a simple mathematical model is developed and used to evaluate the force acting on the knife. Some results are shown from the force measurements and it is concluded that the laboratory chipper is a versatile tool in the process of increasing the understanding of the chipping process.

  • 28.
    Hellström, Lisbeth M
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A device for studying wood chipping under realistic conditions2009In: Proceedings - 2009 International Mechanical Pulping Conference, IMPC 2009, 2009, p. 252-254Conference paper (Refereed)
    Abstract [en]

    It seems to be a consensus in the papermaking society that chip quality is very much a matter of a narrow thickness distribution. Much effort has been spent on studying the influence of certain process parameters on the thickness distribution of chips. However, when these studies have been performed in a laboratory environment, the conditions have been far from realistic when it comes to for instance cutting rates. In this paper a laboratory chipper is presented, which has been developed to admit chipping at rates used in the industry. The knife holder is instrumented in such a way that moments and forces in three directions can be measured. Results from tests, where the cutting rate is varied, is presented and it is concluded that the laboratory chipper is a versatile tool in the process of increasing the understanding of the chipping process.

     

     

  • 29.
    Hellström, Lisbeth M
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A Method for Experimental Investigation of the Wood Chipping Process2008In: Nordic Pulp & Paper Research Journal, ISSN 0283-2631, E-ISSN 2000-0669, Vol. 23, no 3, p. 339-342Article in journal (Refereed)
    Abstract [en]

    SUMMARY: To be able to formulate criteria’s for determining the onset of the creation of a wood chip; it is desirable to be able to study the deformation fields in a vicinity of the edge of the chipping tool. To that end, an experimental setup has been developed in which the chipping can be performed under very well defined conditions. In this setup it is possible to control the rate of indentation of the chipping tool and also to measure the force on the tool. The setup admits also that the angle of the wood specimen with respect to the cutting plane can be varied in both a horizontal and a vertical plane. To determine the deformations, a Digital Speckle Photography (DSP) equipment is used, which together with image processing software makes it possible to determine the strain field on the surface of the wood specimen. One observation that can be made in these studies is that prior to the creation of a chip, there is a localization of strains in a thin region starting from the edge of the tool and directed parallel to the grain. Another observation made during the experimental work is that there exist different types of fracture processes, each giving different chip thicknesses.

  • 30.
    Hellström, Lisbeth Maria
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Gradin, Per A
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    A Study of Fracture processes in Wood Chipping2008In: 6th Fundamental Mechanical Pulp Research Seminar, Espoo: KCL Oy Keskuslaboratorio - Centrallaboratorium AB , 2008Conference paper (Refereed)
  • 31. Holm, P
    et al.
    Löth, K
    Larsson, B
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Solidification Experiments in Mirror Furnaces Flown in a GAS Payload on Space Shuttle STS-1082003In: Proceedings of the 16th ESA Symposium on European Rocket and Balloon Programmes and Related Research, 2003, p. 113-117Conference paper (Other academic)
    Abstract [en]

    Solidification Experiments in Mirror Furnaces Flown in a GAS Payload on Space Shuttle STS-108

  • 32.
    Hummelgård, Magnus
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Zhang, Renyun
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Vengust, D
    Dvorsek, D
    Mihailovic, D
    Olin, Håkan
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Nanowire Transformation and Annealing by Joule Heating2010In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 21, no 16, p. 165704-165704Article in journal (Refereed)
    Abstract [en]

    Joule heating of bundles of Mo6S3I6 nanowires, in real time, was studied using in situ TEM probing. TEM imaging, electron diffraction, and conductivity measurements showed a complete transformation of Mo6S3I6 into Mo via thermal decomposition. The resulting Mo nanowires had a conductivity that was 2-3 orders higher than the starting material. The conductivity increased even further, up to 1.8 x 10(6) S m(-1), when the Mo nanowires went through annealing phases. These results suggest that Joule heating might be a general way to transform or anneal nanowires, pointing to applications such as metal nanowire fabrication, novel memory elements based on material transformation, or in situ improvement of field emitters.

  • 33.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Analysis of solidification in a Bridgman furnace as a simulation of DC casting of aluminium alloy slabs2007In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 23, no 4, p. 475-482Article in journal (Refereed)
    Abstract [en]

    A vertical Bridgman directional solidification equipment has been used in several investigations to simulate DC casting of wrought aluminium alloys. As a base for such investigations and alloy developments, it is important to have an understanding of the performance of the used furnace during simulation of casting conditions. In this investigation the thermal conditions in the furnace have been analysed in detail, both by measurements and by mathematical modelling. The thermal characteristics of the furnace, such as gradient, growth rates and cooling rates have been compared to conditions in large ingots. The DC casting conditions, which the simulations have been compared to, are casting of slabs of 330 and 600 mm width of an AA3003 type alloy. The results show that the experiments are able to simulate the cooling conditions in the ingots except from the surface zone. Comparisons of the microstructure have been made and a good agreement has been obtained for structure parameters such as grain size and DAS.

  • 34.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Differential thermal analysis and differential scanning calorimetry studies of aluminum 3003 alloys with Zn and Cu additions2007In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 38, no 9, p. 2138-2147Article in journal (Refereed)
    Abstract [en]

    The effect of Zn additions in the range of 0 to 5 wt pct and Cu contents of 0.15 to 1.0 wt pct on the solidification and precipitation behavior of aluminum alloys of AA 3003 type was investigated with differential thermal analysis (DTA), differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy/energy-dispersive X-ray (SEM/EDX). The results show that the additions of varying Zn and Cu have significant effects on the crystallization process, phase precipitation, and microstructure formation of the alloys. Phases formed have been identified and morphological differences have been discussed

  • 35.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Directional Solidification of Type AA3003 Alloys with Additions of Zn and Si2004In: SOLIDIFICATION OF ALUMINUM ALLOYS / [ed] Chu, MG; Granger, DA; Han, QY, MINERALS, METALS & MATERIALS SOC , 2004, p. 53-62Conference paper (Refereed)
    Abstract [en]

    Directional solidification has been used to study effects on the structure and on materials properties from variations in the alloy contents in type AA 3003 alloys, Structure parameters such as grain size, DAS and secondary phase precipitations have been evaluated, as well as micro segregation, micro hardness and coarsening after solidification.Here the first part of the project is reported, and additions of Zn and Si have been studied. Zn additions improve the strength of the matrix of the material through solid solution hardening. At a level of 5% the hardness is improved by about 50%, but the solidification structure becomes less promising. The DAS and the secondary phases become coarse, and the solidification range increases significantly as the Zn content increases from 2.5 to 5%.Additions of Si, which have a significantly lower solubility than Zn, quickly gives larger amounts of secondary phase precipitations and a longer solidification interval.Directional Solidification of Type AA3003 Alloys with Additions of Zn and Si.

  • 36.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    DTA and DSC Studies of Aluminium 3003 Alloys with Zn and Cu Additions2007In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 38A, p. 2138-2147Article in journal (Refereed)
    Abstract [en]

    The effect of Zn additions in the range of 0-5wt.% and Cu contents of 0.15-1.0 wt.%, on the solidification and precipitation behaviour of aluminium alloys of AA 3003 type was investigated with differential thermal analysis (DTA), differential scanning calorimetry (DSC), optical microscopy (OM), and scanning electron microscopy (SEM/EDX). The results show that the additions of varying Zn and Cu have significant effects on the crystallization process, phase precipitation and microstructure formation of the alloys. Phases formed have been identified and morphological differences have been discussed.

  • 37.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Effect of refiner addition level on zirconium-containing aluminium alloys2012In: IOP Conference Series: Materials Science and Engineering, Institute of Physics (IOP), 2012, Vol. 27, p. Art. no. 012008-Conference paper (Refereed)
    Abstract [en]

    It is well known that in aluminium alloys containing Zr, grain refiner additions do not function as desired, producing an effect often referred to as nuclei poisoning. This paper investigates the structure of direct chill-cast ingots of commercial AA3003 aluminium alloys, with and without Zr, at various addition levels of Al5Ti1B master alloy. In Bridgman experiments simulating ingot solidification, Zr-containing alloys were studied after the addition of various amounts of Ti. It could be demonstrated, in both ingot casting and simulation experiments, that Zr poisoning can be compensated for by adding more Ti and/or Al5Ti1B. The results confirm better refinement behaviour with the addition of Ti + B than of only Ti. The various combinations of Zr and Ti also influenced the formation of AlFeMn phases, and the precipitation of large Al 6(Mn,Fe) particles was revealed. AlZrTiSi intermetallic compounds were also detected.

  • 38.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Effect of titanium on the microstructure of DC-cast aluminium alloys2005In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 413, p. 277-282Article in journal (Refereed)
    Abstract [en]

    The effect of the Ti content on the solidification structures of aluminum alloys of AA3003 type was investigated. Some improved corrosion properties can be obtained from increasing the Ti contents in aluminium alloys to a level above the normal practice for grain refinement. However, increasing the Ti content above the peritectic point, 0,15%, can influence the grain refinement and cause casting difficulties. The investigation was made by both characterizing the grain structure over the width of DC cast rolling ingots of different alloys, and by studying the solidification micro-structure of Bridgman directional solidified samples, grown to simulate ingot solidi-fication. Structure properties such as grain size, distances between secondary phases and microstructure coarsening were studied. The hardness of the alloys was also determined. It was found that with normal Ti contents in the range of 0,015% the grain refinement is effective. However, upon larger Ti additions to levels around 0,15% the grain structure becomes coarser.

  • 39.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Method Developed for Quantitative Analysis of Inclusions in Solidified Aluminum Ingots2011In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 42, no 1, p. 121-132Article in journal (Refereed)
    Abstract [en]

    A deep-etching method was used to determine inclusions in solidified direct chill cast aluminum ingots. The technique was developed to allow easy quantification of the amount and size distribution of inclusions over billet lengths and cross sections. A pressure filtration (Prefil) test also was used to verify molten alloy cleanliness during casting, and the results of these measurements then were compared. The amount and distribution of nonmetallic inclusions were analyzed, as determined using a NaOH deep-etching method over billet lengths and cross sections. A higher inclusion count was observed at both billet ends, with more inclusions located nearer the billet section centerline. Furthermore, the inclusion density in the radial direction at every distance along the billet length was distributed inhomogeneously. Differences were observed between Prefil samples taken at different casting stages. The Prefil curves and metallographic analysis of Prefil residue obtained from melt samples, at an early casting stage or before degassing, indicate more oxides than in a melt sample taken under steady-state casting conditions. A reasonable correlation was established between the number of inclusions in the molten alloy (measured using Prefil and LiMCA) and the etch pits on deep-etched surfaces of billet cross sections. © 2010 THE MINERALS, METALS & MATERIALS SOCIETY and ASM INTERNATIONAL.

  • 40.
    Jaradeh, Majed
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Method Developed for Quantitative Assessment of Inclusions in aluminium Billets2007In: LIGHT METALS 2007, Minerals, Metals & Materials Society, 2007, p. 679-684Conference paper (Refereed)
    Abstract [en]

    A technique, based on sodium hydroxide hot macro etching, has been developed to deep etch non-metallic inclusions in a way that makes them visible on a macro scale. The distribution of inclusions in transverse sections along DC-cast aluminium billets could thus be studied. The technique has obvious advantages over other common analysis methods in giving a macroscopic spatial distribution of inclusions in a relatively simple way. The paper describes the development of the new technique and some applications. An analysis was made of how different inclusions behave during prolonged strong etching. Light optical microscopy, TEM and SEM/EDX have been used to identify specific inclusions.

  • 41.
    Jaradeh, Majed M.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of applied science and design.
    Analysis of Distribution of Nonmetallic Inclusions in Aluminum DC-Cast Billets and Slabs2012In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, no 1, p. 82-91Article, review/survey (Refereed)
    Abstract [en]

    Inclusion distribution was studied in commercial aluminum DC-cast billets and slabs using a newly developed deep-etching method. Analyses revealed a nonuniform distribution of nonmetallic inclusions across billet diameters and lengths, and also across slab thicknesses and widths. In as-cast billets, more inclusions were found at the beginning and end of the billet length; more were present near the cross-section center than near the surface. In slabs, inclusions were located mostly within 13 mm of the surface and in a band between the centerline and the surface. Few inclusions were found 60 to 100 mm from the slab surface or at the centerline. In addition, comparing slab quality after casting using three types of ceramic foam filters (CFFs; i.e., 30 ppi, 50 ppi, and 50 ppi + HF) revealed significant differences in inclusion size, number, and distribution. Casting slabs using a finer pore-size filter (50 ppi) reduced the number of non-metallic inclusions greatly. The inclusion distribution patterns observed in the solidified slabs are discussed in terms of melt flow during casting.

  • 42.
    Jaradeh, Majed M. R.
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Carlberg, Torbjorn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences, Engineering and Mathematics.
    Solidification Studies of 3003 Aluminium Alloys with Cu and Zr Additions2011In: Journal of Materials Science & Technology, ISSN 1005-0302, Vol. 27, no 7, p. 615-627Article in journal (Refereed)
    Abstract [en]

    The effects of Cu and Zr additions, on the microstructure formation, precipitation and ingot cracking, in commercial 3003 Al alloys have been studied. The investigation was carried out by characterizing the grain structure in DC-cast rolling ingots, and studying the solidification microstructure of Bridgman directionally solidified samples. To better understand the influence of the different Cu and Zr contents on the phase precipitations, differential thermal analysis (DTA) experiments were performed. Results from the ingot microstructure analysis show that in commercial alloys with relatively high contents of Cu and Zr, no significant differences in measured grain sizes compared to conventional 3003 Al alloys could be found. However, only Zr containing alloys exhibited significantly larger grain sizes. Increased grain refiner and/or titanium additions could compensate for the negative effects on nucleation normally following Zr alloying. Different types of precipitates were observed. Based on DTA experiments, increased Cu and Zr contents resulted in the formation of Al2Cu phase, and increased solidification range. It was also found that increased Mn content favors an early precipitation of Al(6)(Mn,Fe) giving relatively coarse precipitates. It was concluded that the Cu alloying has a detrimental effect on hot tearing.

  • 43. Jin, Hu
    et al.
    Jaradeh, Majed
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Solidification studies of 6xxx alloys with different Mg and Si contents2005In: Light Metals 2005, Minerals, Metals & Materials Society, 2005, p. 1039-1044Conference paper (Refereed)
    Abstract [en]

    Directional solidification studies, simulating billet casting, have been made off alloys with balanced and not balanced Mg and Si additions, and with different alloying levels ranging from 6063 to 6082. The effects of growth rate, grain refinement, tempera-ture gradient and composition on struc-ture formation have been investigated. Increased alloy content strongly influence the solidification structure, but during cooling the coarsening process decrease the differences, and relatively similar structures are obtained at room temperature. Segregation to the surface zone is proposed to have an effect on surface defect formation.

  • 44. Kastebo, J
    et al.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Engineering, Physics and Mathematics.
    Temperature Measurements and Modeling of Heat Losses in Molten Metal Distribution Systems.2004In: LIGHT METALS 2004: Proceedings of the Technical Sessions, 133rd Technical TMS Annual Meeting, MINERALS, METALS & MATERIALS SOC , 2004, p. 649-654Conference paper (Refereed)
    Abstract [en]

    During casting of aluminum ingots the molten metal has to be transported from the furnace to the moulds. During the transport heat is lost both to the atmosphere and to the refractory launder system itself. As different dimensions of the cast ingots necessitate different design of the system the difference between the furnace temperature and the temperature in the metal, which enters the mould, can vary significantly. It is therefore of importance to have a good knowledge of the heat fluxes in the launder system and of how the temperature decreases during metal flow.In this work thorough measurements of the temperature have been made in casting tables of different design during casting of different ingot dimensions. Based on the experimental results an analytic model has been derived. Good correlation between calculated and measured temperature losses was obtained. It was also possible, from the results, to obtain an understanding of heat transport from a liquid metal flowing in an open channel, and the relative importance of radiation to the atmosphere and conduction to the refractory.Temperature measurements and modeling of heat losses in molten metal distribution systems

  • 45.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Casting practices influencing inclusion distributions in billets2013In: Light Metals, ISSN 0147-0809, p. 987-991Article in journal (Refereed)
    Abstract [en]

    A macro-etching method has been used to analyze the distribution and amount of inclusions along billets and on cross sections. Main parameters that have been varied are holding time before casting and amount of liquid remaining after casting. The result show that short holding times, in the order of 10 minutes, give increased amount of inclusions in the beginning of the billets, but holding times in the range from 30 to 60 minutes do not show any significant differences. If the melt remaining in the furnace after casting is less than about 3000 kg, the inclusion density increases towards the end of the ingots. The distribution of inclusions over the cross section of billets show that most inclusions are found in the centre of the billets, however, at increased total amount of inclusions, they tend to appear evenly over the whole cross sections. The results are discussed based on convection in furnace and settling rates and convection at solidification front.

  • 46.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Hot tearing susceptibility of AA3000 aluminum alloy containing Cu, Ti, and ZrIn: Article in journal (Refereed)
  • 47.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    On the dissolution Process of Manganese and Iron in Molten Aluminum2019In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 50, no 4, p. 1873-1887Article in journal (Refereed)
    Abstract [en]

    The dissolution of Mn and Fe in liquid Al presents a challenge due to their high melting points and low diffusivity. A literature review reveals that the existing knowledge of the processes involved in the dissolution of both Fe and Mn in liquid Al is rather ambiguous. Thus, this work aimed to obtain more detailed insights into the dissolution behavior of Mn and Fe in various Al melts. The results of the Mn dissolution tests showed that three intermediate phases were involved in the dissolution process, all of which exhibited a smooth interface between Mn and the liquid. These three phases were identified as the γ2, Al11Mn4, and µ phases which grow slowly, penetrating the Mn particles. The results of the Fe dissolution tests showed that in pure Al, the Al5Fe2 phase dominates the dissolution process and penetrates the Fe particles. The addition of Ti into the molten Al alters the intermetallic compound formation by replacing Al5Fe2 by Al2Fe. The addition of Si significantly inhibited the Fe dissolution kinetics. A theoretical approach based on Ficks’ law was used to explain the experimentally obtained Mn and Fe dissolution rates. It showed that the surface area and shape of the additives significantly affected the dissolution processes.

  • 48.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Segregation during metal sampling2014In: Materials science forum, Trans Tech Publications Inc., 2014, p. 83-88Conference paper (Refereed)
    Abstract [en]

    In order to obtain accurate chemical compositions in as-cast billets and ingots the sampling methods for the analysis have to give reproducible results with high precision. OES analysis made on samples at certain milling depths does not always show the desired nominal composition, and especially the macro segregation profiles within the samples can show significant variations. The present work examine the influence of main sampling parameters, such as the volume of the melt, the melt temperature, the mould design and the method of filling the mould, on the segregation. The results point out the importance of the convection in the mould during solidification, and thus the technique of pouring the melt into the sampling mould. © (2014) Trans Tech Publications, Switzerland.

  • 49.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Solidification studies of 3003 alloys with different Mn and Ti contents2017In: Solidification processing 2017: proceedings of the 6th Decennial International Conference on Solidification Processing : 25-28 July 2017, Beaumont Estate, Old Windsor, UK / [ed] Fan, Zhongyun, bcast , 2017Conference paper (Refereed)
    Abstract [en]

    Aluminum alloys of AA3003 are widely used in heat exchangers. This type of alloy mainly contains manganese as alloying element, but in recent developments there have been additions of both titanium and copper. The limits of Mn solubility in aluminum are influenced by these additions, which can cause the formation of large particles of an unwanted AlMnTi phase.

    This project was initiated to investigate the effects of Mn contents in combination with Ti additions on the solidification and precipitation behavior using both Bridgman directional solidification and DTA equipment. The results show that coarse AlMnTi particles start forming when Mn contents are over 1.5 wt% in alloys with 0.14 wt% Ti and that the amount significantly increases with increasing Mn content from this level. Large particles were also found for Mn contents slightly below 1.4 wt%. If the Ti additions were on the level of 0.25 wt%. The DTA experiments show that AlMnTi phases grow in a limited temperature interval, and can reach a size of 150 microns. Such large sized particles are detrimental for the material in the ensuing rolling operation and must be avoided, and it is, therefore, important to accurately control the combinations of Mn and Ti contents.

  • 50.
    Razaz, Ghadir
    et al.
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Carlberg, Torbjörn
    Mid Sweden University, Faculty of Science, Technology and Media, Department of Natural Sciences.
    Study of manganese dissolution in aluminum melts2016In: TMS Light Metals, Minerals, Metals & Materials Society, 2016, p. 731-736Conference paper (Refereed)
    Abstract [en]

    Problems with the yield during Mn alloy additions and the occurrence of undissolved Mn rich phases in as cast material containing Ti is the background to the present study of the dissolution of Mn compacts in aluminum melts. The dissolution rate of Mn in liquid aluminum, have been studied in pure Al and in Al-0.12%Ti melts. It was found that Ti additions to the melt decreased the dissolution rate of Mn compacts. It was also shown that the intermediate phases formed at the interface between Mn and liquid aluminum was different after small Ti additions. Moreover, an undissolved Mn briquette, found after casting in a furnace, was examined and the conditions for this to happen have been discussed. The discussion was based on calculations of heat balances during the initial dissolution steps and studies of the transformations occurring within the briquette.

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