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  • 1.
    Amirinejhad, Sajad
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Kerman, Iran.;Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Sch Engn, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Kerman, Iran..
    Calorimetric study of the oxidation of Al-Mg alloys for the prediction of healing of the double oxide film defect2013Ingår i: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 113, nr 2, s. 769-777Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The oxidation of Al alloys containing 0.3-4.5 wt% Mg in an atmosphere with a very low oxygen partial pressure (< 0.5 ppm, to depict the atmosphere within a double oxide film defect) was studied using differential scanning calorimetry and scanning electron microscopy. The results showed that a newly formed Al2O3 layer held in an Al-Mg melt first transformed to MgAl2O4 spinel and then to MgO. This mechanism was the same for all the Al alloys containing 0.3-4.5 wt% Mg, but the kinetics of the transformations were different and depended on the Mg content of the melt. The results also suggest that the two layers of a double oxide film defect that is held in an Al melt containing 0.3-4.5 wt% Mg can heal (i.e. bond to each other) if held in the liquid metal for a long enough period of time.

  • 2.
    Bagherpour-Torghabeh, Hamed
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman 7616914111, Iran.;Shahid Bahonar Univ Kerman, Mineral Ind Res Ctr, Jomhoori Eslami Blvd, Kerman 7616914111, Iran..
    Role of Mechanical Stirring of Al-Mg Melt in the Healing of Bifilm Defect2017Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 48, nr 6, s. 3174-3184Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effect of mechanical stirring of aluminum melts containing 0.3, 0.7, and 4.5 wt pct Mg with a graphite rotor with different rotation speeds of 85 and 220 RPM on the behavior of bifilms was investigated using a reduced pressure test. The results showed that the mechanical stirring at 85 RPM accelerated the healing of the bifilms by increasing the rate of formation of cracks on the bifilms and hence accelerated the consumption of their atmosphere and provided enough Mg for the transformation of the alumina layers of the bifilms to spinel. Mechanical stirring with a high speed of 220 RPM caused aspiration of the surface oxide into the melt to form new bifilms which counteracted the healing of the previously presented bifilms.

  • 3.
    Esfahani, Hosein Bartar
    et al.
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Decrease in the rate of diffusion of hydrogen through layers of bifilm defects in Al melt in the presence of Sr2016Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, nr 3, s. 179-185Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in the diffusion rate of H through layers of bifilm defects in Al-0.05 wt% Sr melt was investigated by studying the change in the porosity of samples that were held in furnace for different times, subjected to vibration and then solidified under reduced pressure. The results showed that the vibration accelerated the rate of formation of cracks on the layers of the defects, the rate of diffusion of H into their atmosphere and the rate of consumption of Sr in the melt. These rates decreased gradually as the melt was held in the furnace before applying the vibration. This decrease was attributed to the transformation of alumina to Sr-containing oxides, which caused the strength of the layers to increase and the rate of formation of cracks on them to decrease. This behaviour may have an impact on the increase in porosity of Al castings modified by Sr.

  • 4.
    Esfahani, Hosein Bartar
    et al.
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    The Effect of Strontium on the Strength of Layers of Double Oxide Film Defects2016Ingår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 47A, nr 3, s. 1331-1338Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in the strength of layers of oxide film (bifilm) defects when held in Al-0.05 and 0.1 wt pct melts was evaluated indirectly by comparing the porosity, average pore roundness, and pore number density results obtained from a reduced pressure test of the commercial purity and Sr-containing Al melts subjected to different holding and vibration regimes. Any changes in the composition of the pores were also studied using scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the Al2O3 layers of a newly formed oxide film defect, when held in Al-0.05 or 0.1 wt pct Sr melt, transformed gradually into an Sr-containing oxide. This transformation caused the strength of the oxide layers to increase and the rate of the expansion of its atmosphere and removal of the defect from the melt to decrease. This might influence the increase in the porosity of Sr-modified Al castings.

  • 5.
    Esfahani, Hosein Bartar
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Kerman, Iran..
    Weibull verification of reduced pressure test as a tool for assessing Al melt quality2017Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 30, nr 2, s. 87-95Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The credibility of reduced pressure test (RPT) as a substitute for Weibull analysis for benchmarking bifilm defects in Al alloys was confirmed by comparing the RPT parameters (2D and 3D porosity, and Bifilm Index) with the Weibull moduli for UTS values for pure Al and Al-0.05Sr alloys. The porosity of RPT samples was found to have an exponential decay relationship with Weibull modulus. A reasonable trend for Bifilm Index could not be found. 3D porosity of RPT samples was found to be more favourable than 2D porosity or Bifilm Index. Some evidence was also found of connections occurring between the sides of bifilm defects at the surfaces of the fractured tensile test bars of Al-0.05Sr alloy which had a relatively high UTS.

  • 6.
    Khaleghifar, Farzaneh
    et al.
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Sch Engn, Mineral Ind Res Ctr, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Sch Engn, Mineral Ind Res Ctr, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, Kerman, Iran.;Shahid Bahonar Univ Kerman, Sch Engn, Mineral Ind Res Ctr, Kerman, Iran..
    Effect of Ca on the Behavior of Double Oxide Film Defects in Commercially Pure Aluminum Melt2015Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 46, nr 2, s. 1044-1051Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in the composition of oxide layers and the possibility of the formation of bonding between the two layers of a double oxide film defect when held in Al-0.01 and 0.05 wt pct Ca melt was investigated, and the thermodynamics of the transformations occurring in the Al-Ca-Al2O3 system was studied. The defect was modeled experimentally by maintaining two aluminum oxide layers in contact with one another in the liquid metal at 1023 K (750 degrees C) for times ranging from 5 seconds to 50 hours. Any changes in the composition and morphology of these layers were studied by scanning electron microscopy and energy-dispersive X-ray spectroscopy. The results showed that the initial Al2O3 layer started to transform to a mixture of calcium aluminates in both alloys when the Al bars were still in the solid state. This transformation caused the two oxide layers to bond with each other gradually after the bars melted. The degree of bonding, however, was not consistent between the repetitions of the experiments, which was attributed to the difference between the initial H content of the melt on different experimental days.

  • 7.
    Nateghian, Morteza
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Mineral Ind Res Ctr, Kerman 7616914111, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Mineral Ind Res Ctr, Kerman 7616914111, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Mineral Ind Res Ctr, Kerman 7616914111, Iran..
    Behavior of Double-Oxide Film Defects in Al-0.05 wt pct Sr Alloy2012Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 43, nr 6, s. 1540-1549Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The change in the composition of oxide layers and the possibility of the formation of bonding between the two layers of a double-oxide film defect when held in an Al-0.05 wt pct Sr melt was investigated. The defect was modeled experimentally by maintaining two aluminum oxide layers in contact with one another in the liquid metal at 1023 K (750 A degrees C) for times ranging from 5 seconds to 50 hours. Any changes in the composition and morphology of these layers were studied by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results showed that the A1(2)O(3) layers started to transform to SrO gradually from the moment that they submerged into the melt. The transformation caused the two layers to bond with each other gradually. The results illustrated that the composition of the oxide layers of a double oxide film defect submerged in Sr-treated melt is different from that of pure Al, and this might affect the mechanical properties and the behavior of the defect in the melt significantly.

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