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  • 1.
    Muhmond, Haji Muhammad
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Processing.
    On the Inoculation and Graphite Morphologies of Cast Iron2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Research was conducted to understand the nucleation mechanism of graphite flakes and nodules and the effect of various elements on the growth morphology of graphite. Investigations were started on flake graphite cast iron. The effect of S on the graphite morphology and MnS was experimentally analysed. The influence of various type of oxides on the growth morphology of MnS and their relation with the graphite growth morphology was studied carefully through series of experiments, and results were related to the thermodynamic calculations, performed to predict the nucleation of oxides and sulfides at any temperature. The calculations were supported by EDX analysis on particles in the samples, showing sequential nucleation of flake graphite. The austenite volume fraction and the dendrite growth orientations were affected by the addition of Al to the melt. The effect of aluminium oxide and sulfur was studied on the austenite growth morphology with the help of colour etching technique. Thermal analyses were performed to study the effect of sulfur content on austenite volume fraction and growth morphology using DSC. The latent heat of solidification and the rate of austenite formation was studied and related to the sulfur content in the alloy.

    To study the effect of O and S on the graphite morphology, pure Fe-C alloy was prepared and strong de-oxidizers and de-sulfurizer (Mg, Ca and Sr) were tested. With the help of ion etching and polishing, we were able to reveal the graphite growth morphology. The morphological changes in the graphite were explained by relating it to the composition of the melt in regard of dissolved S and O in the melt. The effect of other trace elements such as S, F, O, N, P, B and Se, was also investigated by testing them on an ultra-pure Fe-C alloy. The possibility of substituting a foreign atom in the basal plane of graphite was analysed based on the bonding energy between C and the foreign atoms. The resulting change in the structure of the basal plane was studied using Avogadro software and the resulting model were compared with the experimental results. The basal plane of nodular, flake and undercooled graphite was studied with the help of HRTEM, which showed differences in the lattice spacing between different graphite morphologies. The latent heat measurement showed that flake graphite have higher energy than the undercooled or vermicular graphite. This research made us enabled to tell about the growth along c-plane in graphite and the reason behind the transition of graphite morphology.

    The effect of inoculation temperature and inoculation sequence on the nodularity was studied. EDX analysis were performed and the results were compared to the thermodynamic calculations.  It was found that, the melt composition is controlling the graphite growth morphologies. Strong de-oxidizers and de-sulfurizer are necessary to reduce O and S to a level where it does not influence the graphite growth morphology. The effect of various elements on the activity of oxygen in the melt is calculated. High Al cast iron was also studied. The major problem associated with this type of alloy was that, the Mg was not effective in producing nodular graphite. Experiments showed that de-oxidizers stronger than Mg are required to increase the nodularity. Thermodynamic calculations showed that the activity of oxygen in the melt was changing strongly by increasing the Al content in the alloy. This was increasing the required oxygen level to nucleate MgO.

  • 2.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    An Investigation on the Effect of S and Al on the AusteniteGrowth Morphology in Gray Cast Iron, Using Thermal Analysisand Etching Technique2013In: Transactions of the Indian Institute of Metals, ISSN 0019-493X, Vol. 66, no 2, p. 185-192Article in journal (Refereed)
    Abstract [en]

    The austenite nucleation and growth morphology was investigated through experiments by inoculation with pure Al in a controlled environment using DTA furnace and H.F furnace. The austenite volume fraction and the dendrite growth orientations were affected by the addition of Al to the melt. Thermal analyses were performed to study the effect of sulfur content on austenite volume fraction and growth morphology using DSC. The possibility of austenite nucleation by MnS particles was analyzed. Different sulfur contents in the alloys were resulting in change in the latent heat of solidification and the rate of austenite formation. Austenite volume fraction was measured with four methods, colour etching, DSC thermal analysis, lever rule, and using LH calculated by Thermo-Calc data base, and a comparison was made among them.

  • 3.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Effect of the cooling rate on the graphite nodule count and size distribution in nodular cast iron2018In: 11th International Symposium on the Science and Processing of Cast Iron, SPCI-XI 2017, Trans Tech Publications, 2018, Vol. 925, p. 45-53Conference paper (Refereed)
    Abstract [en]

    The graphite nodule count, size distribution and homogenization of the nodules distribution are the factors which are of more significance for the properties of the material. By just increasing the inoculants or Mg will not help to get rid of problems like the un-even size distribution and or increasing the nodule count. The cooling conditions of the melt prior to solidification and during solidification can control these two parameters to a large extent. In this research, it is more emphasized on the nucleation sequence of MgO particles and on the cooling rates. The nucleation of MgO at different temperatures and at different cooling rates was found to have a great influence on the nodule size distribution and the homogenization of the microstructure. A mathematical model was derived to relate the Mg concentration in the liquid to the cooling rate, prior to solidification. The MgO particles count was calculated as a function of cooling rate. It was found that at higher cooling rates, MgO can be nucleated in multi steps during cooling process, which can increase the nodule count tremendously.

  • 4.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Graphite growth control analysis in high Al cast iron2016In: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, no 5, p. 272-278Article in journal (Refereed)
    Abstract [en]

    High Si and Al cast iron has been investigated experimentally and thermodynamically. Alloys were prepared in the laboratory with low to high Al and Si concentrations. Experiments were performed using Mg treatment of the melt. In another series of experiments, the effect of Ca and Ce in the absence of Mg was studied. The samples were analysed using scanning electron microscope and energy-dispersive X-ray spectroscopy. In alloys with high Al and Si content, the formation of chunky graphite is crucial for control. The effects of Al, Si and inoculants were analysed with the help of thermodynamics. It was found that the activity of oxygen changed due to the high concentrations of Al and Si, which influenced the nucleation of MgO and other oxides in the melt. The oxygen level in the melt determines the graphite morphology.

  • 5.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Graphite growth control in nodular cast iron2014Manuscript (preprint) (Other academic)
  • 6.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Graphite growth morphologies in cast iron2014In: Solidification and Gravity VI, Trans Tech Publications Inc., 2014, p. 458-463Conference paper (Refereed)
    Abstract [en]

    Graphite growth morphology was studied by using InLense detector on FEG-SEM after performing ion etching on the samples. Star like and circumferential growth mechanism of graphite was observed in the graphite nodules. Pure ternary alloy of hypo eutectic and hyper eutectic composition was treated with pure Mg, Ca and Sr, to study the effect of O and S concentration in the melt, on the transition of graphite morphology from nodular to vermicular/compacted and flake graphite. The change in the melt composition between the austenite dendrites due to microsegregation of S, O and inoculants and their possible effects on the transition of graphite morphologies as well as the nucleation of new oxides/sulfides particles is discussed with the help of thermodynamics.

  • 7.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Graphite Growth Morphologies in High Al Cast Iron2014Manuscript (preprint) (Other academic)
  • 8.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Graphite growth morphologies in high Al castiron2015In: Advances in the Science and Engineering of Casting Solidification: An MPMD Symposium Honoring Doru Michael Stefanescu, The Minerals, Metals, and Materials Society, 2015, p. 323-330Conference paper (Refereed)
    Abstract [en]

    High Si and Al cast iron has been investigated experimentally and thermodynamically. Alloys were prepared in the laboratory with low to high Al and Si concentrations. Experiments were performed using Mg treatment of the melt. In another series of experiments, the effect of Ca, Sr and Ce on graphite morphology was investigated. In the last experiments, the effect of Ca and Ce in the absence of Mg was studied. The samples were analyzed using field emission-scanning electron microscope (FE-SEM) and energy dispersive x-ray spectroscopy (EDX). In alloys with high Al and Si, the formation of chunky graphite is crucial for control. The effects of Al, Si and inoculants were analyzed with the help of thermodynamics. It was found that the activity of oxygen changed due to the high concentrations of Al and Si, which influenced the nucleation of MgO and other oxides in the melt. The oxygen level in the melt determines the graphite morphology.

  • 9.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Relationship Between Inoculants and the Morphologies of MnS and Graphite in Gray Cast Iron2013In: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 44, no 2, p. 283-298Article in journal (Refereed)
    Abstract [en]

    The influence of oxides and sulfides in gray cast iron on the growth morphologies of MnS and on the nucleation of graphite was experimentally investigated using scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) analysis with evidences that shows the possible nucleation sites for graphite nucleation. Thermodynamic studies have been done on the influence of varying sulfur concentrations on the nucleation of MnS in the melt and during solidification. The consumption of dissolved oxygen and sulfur in the melt during the cooling process was analyzed and we explored how this influenced the nucleation process of oxides and sulfides. A sequential nucleation concept of oxides and MnS is proposed in relation to the growth morphology of MnS and graphite with respect to the mechanical properties of cast iron. The nucleation of new oxides and sulfides was analyzed using thermodynamics and compared to our experimental results. Graphite nucleation on substrates other than MnS, such as MoS2 oxides and (Mo,Cr)S, was experimentally analyzed along with the influence of the substrates on graphite nucleation and growth morphology.

  • 10.
    Muhmond, Haji Muhammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Fredriksson, Hasse
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Casting of Metals.
    Relationship Between the Trace Elements and Graphite Growth Morphologies in Cast Iron2014In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 45, no 13, p. 6187-6199Article in journal (Refereed)
    Abstract [en]

    The graphite morphology transition was studied using various techniques and additives in ultra-pure binary and ternary alloys with hypo- and hypereutectic compositions. Some of the trace elements were observed to stabilize the flake growth morphology of graphite, while others did not. The distance between the graphite basal planes of spheroidal, flake, and undercooled fine graphite was measured and the lattice fringes were studied using high resolution transmission electron microscope, after preparing a thin lamella of graphite using focused ion beam. Latent heat measurement was performed using differential scanning calorimeter on the pure binary alloy with and without sulfur and oxygen additions. The substitution of various elements under study in a monolayer of graphene was analyzed by considering the binding energies of the elements with C and their bonding nature. Simulations were performed using a molecule editor program and visualizer (Avogadro software), which considers various types of interatomic forces to optimize a monolayer of graphene to a minimum energy. The effect of the type of cyclic C-ring structure and energy of the basal plane of graphite with a connection to the addition of trace elements individually in the monolayer of graphene was studied and simulated to understand the resulting bulk graphite growth morphology.

1 - 10 of 10
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  • ieee
  • modern-language-association-8th-edition
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