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  • 1.
    Adineh, Morteza
    et al.
    Shahid Bahonar Univ Kerman, Coll Engn, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shahid Bahonar Univ Kerman, Coll Engn, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Microstructure, mechanical properties and machinability of Cu-Zn-Mg and Cu-Zn-Sb brass alloys2019Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 35, nr 12, s. 1504-1514Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Lead-free alloys have attracted great attentions recently due to the toxic nature of lead for the human body. In this study, low amounts of Mg and Sb were added to the Cu65-Zn35 brass and microstructure, mechanical properties and machinability of samples were compared to Cu65-Zn35 brass. Both Mg and Sb led to the promotion of beta ' phase as well as the formation of new ternary copper rich intermetallic particles. It was found that these particles had a significant role in the reduction of the ultimate tensile strength, toughness, work hardening and elongation while increasing the hardness of samples. Results of machinability evaluation of samples showed that the cutting forces were decreased significantly and morphology of chips were improved compared to Cu65-Zn35 brass sample.

  • 2. Alirezaei, Mohammadamin
    et al.
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Microstructure evolution in cast and equilibrium heat-treated CuZn30-(Si) alloys2016Ingår i: International Journal of Cast Metals Research, ISSN 1364-0461, E-ISSN 1743-1336, Vol. 29, nr 4, s. 222-227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The main object of this work was to investigate the effect of Si addition and heat treatment on the microstructure of CuZn30 alloy. The alloys were prepared by casting and then the chemical composition, microstructure and phases were determined by optical and scanning electron microscope and XRD analysis. The resulting microstructures contained two phases, alpha and beta', with volume fraction depending on silicon content. Increments of Si content led to the formation of a Widmanstatten structure. It was also found that the silicon dissolved completely in alpha + beta phases and the lattice parameters of both alpha- and beta'-phases increased as the Si content increased. Hardness tests showed that hardness of both the as-cast and heat-treated samples increased as the Si content increased, and a significant increment of hardness in heat-treated alloy was due to the formation of a martensite phase.

  • 3.
    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.

  • 4.
    Bagherpour-Torghabeh, Hamed
    et al.
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Raiszadeh, Ramin
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Sch Engn, Dept Met & Mat Sci, JomhooriEslami Blvd, Kerman, Iran..
    Removal of Bifilms from Al Melts by Stirring in Unbaffled and Baffled Crucibles2018Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 49, nr 6, s. 3456-3469Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The free surface of aluminum melt, during stirring under different rotation speeds in unbaffled and baffled crucibles, was simulated numerically using a RANS turbulence model coupled with a particle-tracking method. The effect of mechanical stirring of Al melts containing 0.3, 0.7, and 4.5 wt pct Mg in unbaffled and baffled crucibles on the rate of elimination of bifilms from the melt was also investigated using a reduced pressure test. The results showed that the stirring increased the rate of removal of bifilms from the melt due to an increase in the rate of formation of cracks on the bifilms. Using baffles in the crucible accelerated the rate of removal of bifilms by changing the pattern of movement of bifilms in the melt. The critical stirring speeds, above which the oxide layer on the Al melt could submerge into the bulk liquid, were determined by the simulation. It was confirmed by the experimental results to be about 158 and 420 RPM for the unbaffled and baffled crucibles, respectively.

  • 5.
    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.

  • 6.
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    A Study of Slag/Metal Equilibrium and Inclusion Characteristics during Ladle Treatment and after Ingot Casting2009Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Today, there is a high demand on clean steel for high performance materialproperties. Thus, steel producers try to deliver a steel product with the highestquality and cleanliness to the market. The number of parameters that affect thesteel cleanliness may vary depending on the required material properties of thefinal product. However, the non-metallic inclusion characteristics represent one ofthe most important parameters. More specifically, the composition, size, numberand morphology affect steel cleanliness. In this work, selected parameters affectingthe inclusion characteristics were studied using the following methods: i)thermodynamic calculations (including computational thermodynamiccalculations), ii) inclusion determinations using a cross sectional (CS) method (2Dinvestigations) and iii) inclusion determinations using an electrolytic extraction(EE) method (3D investigations).

    The computational thermodynamic calculations of the slag-steel and inclusion-steelequilibriums were carried out using the Thermo-Calc software. With the help ofthese calculations, the influence of the slag carryover on the top slag, aluminumcontent in steel and sulfur distribution ratio as well as predictions of stable phasesof inclusions were studied. In addition, inclusion determinations of tool steel gradesamples collected during various stages of the ladle treatment in a scrap-based steelplant were carried out using both 2D and 3D methods. Furthermore, inclusiondeterminations of bearing steel grade samples from a runner system after ingotcasting were performed using a 2D metallographic method (CS-method). Also, theINCAFeature software was used, when using cross sectional method, in order tocollect more statistics of the inclusion characteristics.

    It was found that slag carryover has a large influence on the composition of theactual top slag as well as the aluminum content in the steel as well as the sulfurdistribution ratio. In addition, steel and slag were found to be in “near”-equilibriumconditions, after the completion of the vacuum degassing operation. Furthermore,the composition of small-size inclusions in samples taken from tool steel was foundto be very scattered. Moreover, the composition of the large-size inclusions wasfound to be less scattered. Furthermore, closer to the top slag composition insamples collected after vacuum degassing. Finally, the accuracy of the inclusioncomposition determinations of tool steel samples using the electrolytic extractionmethod was found to be better than for the cross sectional method. The worseaccuracy of the CS-method is due to a considerable effect of matrix elements oninclusion composition.

  • 7.
    Doostmohammadi, Hamid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Andersson, Margareta A. T.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Steneholm, Karin
    Uddeholm Tooling AB.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Effect of EAF Slag Carryover on Slag-metal Equilibrium Calculations for Ladle Degassing Process2009Ingår i: EPD CONGRESS 2009, PROCEEDINGS    / [ed] Howard SM, 2009, s. 695-702Konferensbidrag (Refereegranskat)
    Abstract [en]

    During the tapping of liquid steel from Electric Arc Furnace (EAF), some slag is carried over into the ladle. High levels of FeO and MnO in slag carryover increase the oxygen activity in steel melt leading to oxide inclusion formation during the ladle treatment. The demand on cleaner steels requires minimization of carryover slag. In this work, the effect of EAF slag carryover on ladle slag-steel equilibrium calculations for a hot working tool steel was studied. Steel and slag sampling were done in Uddeholm Tooling AB in Sweden. XRF and OES techniques were used to determine chemical composition of samples. The quantity of slag carryover was calculated based on a mass balance followed by thermodynamic calculations on metal-slag equilibrium using Thermo-Calc software. The agreement between predictions and experimentally determined compositions was good. This leads to the development of a prediction method for optimizing the production of other tool steel grades.

  • 8.
    Doostmohammadi, Hamid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Andersson, Margareta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Use of Computational Thermodynamic Calculations in Studying the Slag/Steel Equilibrium during Vacuum Degassing2010Ingår i: STEEL RES INT, ISSN 1611-3683, Vol. 81, nr 1, s. 31-39Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The effectiveness of a ladle refining process for production of tool steel with focus on the top slag is studied using computational thermodynamic calculations. The theoretical assessment was based on compositional data of steel and slag samples collected during trials in a plant equipped with a 65-t EAF, a ladle furnace and a vacuum degasser The calculation of slag-metal equilibrium during ladle treatment was performed for top slag excluding (Case A) and including (Case B) slag carryover and deoxidation products. The predictions showed that slag carryover and deoxidation products in the ladle significantly affect the composition of the top slag. Thus, these conditions must be taken into consideration when predicting the actual top slag composition. It was also found that it is possible to predict the final aluminium and sulphur content in steel based on the same calculation approach.

  • 9.
    Doostmohammadi, Hamid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Andersson, Margareta
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär G.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Thermodynamic and Experimental Considerations of the Inclusion Characteristics during Vacuum Degassing of Tool SteelManuskript (preprint) (Övrig (populärvetenskap, debatt, mm))
  • 10.
    Doostmohammadi, Hamid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Jönsson, Pär
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    Komenda, J
    Hagman, S
    Inclusion Characteristics of Bearing Steel in a Runner after Ingot Casting2010Ingår i: STEEL RES INT, ISSN 1611-3683, Vol. 81, nr 2, s. 142-149Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the uphill teaming method of ingot casting molten metal from the ladle goes into the runner system, which feeds one or several ingot moulds. This method is still important for production of bearing steel. In order to make clean steel, which has a controlled amount of inclusions, good understanding of inclusions characteristics is necessary In this work non-metallic inclusions of steel left in the runner part of an ingot casting system were studied. Inclusion type, size, and morphology were the main focus of this study A scanning electron microscope (SEM) was used to assess inclusion size and morphology The chemical composition of inclusions was determined by SEM equipped with EDS. An automated program called 'INCAFeature' was used to collect statistics of inclusion characteristics. Based on the statistical analysis of inclusion composition, four types of inclusions including oxides, sulfides, carbonitrides and complex inclusions were defined. The inclusion characteristics in the runner were also compared to literature data of inclusions found in ladle and mould samples.

  • 11.
    Doostmohammadi, Hamid
    et al.
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Karasev, Andrey
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap.
    Jönsson, Pär G
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap, Tillämpad processmetallurgi.
    A Comparison of a Two-Dimensional and a Three-Dimensional Method for Inclusion Determinations in Tool Steel2010Ingår i: STEEL RES INT, ISSN 1611-3683, Vol. 81, nr 5, s. 398-406Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To produce clean commercial tool steel the non-metallic inclusions characteristics have to be known, since they influence the mechanical properties of steel. In this work, inclusion characteristics in steel samples from plant trials were studied. The samples were collected in the steel plant according the two following methods: (a) 2D investigations of inclusions by a cross sectional method and (b) 3D investigations of inclusions collected on a film filter after electrolytic extraction. More specifically, the chemical composition, morphology, number and size distribution of inclusions in tool steel samples taken from ladle during melt treatment were determined by both methods. In both methods SEM equipped with EDS was used for compositional analysis of inclusions. In addition, in the cross sectional method an automated detection program called 'INCAFeature' was used to collect more statistics of non-metallic inclusions. The composition of inclusions larger than 5 mu m was found to contain 49% CaO based on the results from both methods. However, for smaller inclusions it was found that the accuracy of the 2D method was less than that of the 3D method due to the influence of the metal matrix on the results. In addition, it was found that a critical inclusion size of 4 mu m could be defined for the 3D method, above which the standard deviation in composition determination was very low.

  • 12.
    Doostmohammadi, Hamid
    et al.
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Moridshahi, Hamid
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Effects of Si on the microstructure, ordering transformation and properties of the Cu60Zn40 alloy2015Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 640, s. 401-407Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effects of small additions of Si to Cu60Zn40 on the properties, microstructure and phase transformation were investigated. It was found that Si promotes the formation of beta' phase and the microstructure of the alloys was changed from duplex alpha + beta' to single phase beta' brass. Electron to atom ratio was calculated and it was concluded that increment in this ratio led to a decrease in stacking fault energy which had an important role in reduction of the grain size as well microstructural variations in this study. The dilatomeric analysis showed that Si increased the ordering temperature of Cu60Zn40 alloy. Finally, based on the properties, the Cu-Zn-40-Si alloys are predicted to have the potential of being an alternative for free cutting leaded brass.

  • 13.
    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.

  • 14.
    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.

  • 15.
    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.

  • 16.
    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.

  • 17.
    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.

  • 18.
    Rajabi, Zahra
    et al.
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Met & Mat Sci, Jomhoori Eslami Blvd, Kerman, Iran..
    Effect of addition of tin on the microstructure and machinability of alpha-brass2018Ingår i: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 34, nr 10, s. 1218-1227Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study was aimed at developing lead-free brass alloys with the goal of substituting lead element with tin. For this purpose, lead-free alloys with tin were developed and the microstructure, hardness and machining behaviour of the Cu-30%Zn alloy was compared with Cu-30%Zn-x%Sn (x = 1.2, 3.2, 5.4, 8,11.4,13.9,17.4). The results showed that the addition of Sn to single-alpha phase brass led to the formation of duplex (alpha + beta') brass and then the formation of (beta' + gamma) brass both with increased hardness. In addition, the addition of Sn to Cu-30%Zn alloy led to the decrement of equivalent machining forces (F-m), surface roughness and also the promotion of chip fragmentation due to the formation of the beta' phase, which is an improvement in machinability.

  • 19. Sistaninia, M.
    et al.
    Doostmohammadi, Hamid
    Shahid Bahonar University of Kerman, Iran.
    Raiszadeh, R.
    Formation Mechanisms and Microstructure Characterization of Al/Al3Ni In-situ Composite by Compound Casting2019Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science, ISSN 1073-5615, E-ISSN 1543-1916, Vol. 50, nr 6, s. 3020-3026Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The Compound casting method was used to produce an Al/Ni bimetal composite. The mechanisms of formation of the reinforcing intermetallic phases were studied and the produced bimetal composite’s microstructure was then characterized. The results showed that the Al/Ni interface consisted of two intermetallic layers including Al3Ni2 and Al3Ni. It is suggested that the Al3Ni reinforcing particles of the composite originated from two sources. (1) Some Al3Ni particles detached from the Al3Ni layer formed at the interface between the Ni core and the Al melt and dispersed in the liquid Al and (2) Al-Al3Ni eutectic phase, which formed during the solidification process. The increase in the temperature led to the formation of more reinforcing particles and extended the depth of dispersion of the particles in the Al matrix.

  • 20.
    Yousefi, Maryam
    et al.
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran.;Shahid Bahonar Univ Kerman, Young Researchers Soc, Kerman, Iran..
    Doostmohammadi, Hamid
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Microstructure characterization and formation mechanism of functionally graded Al-TiAl3 insitu composite by liquid-solid interaction2018Ingår i: Journal of Alloys and Compounds, ISSN 0925-8388, E-ISSN 1873-4669, Vol. 766, s. 721-728Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, microstructure and formation mechanism of functionally graded Al-TiAl3 insitu composite fabricated by solid-liquid interaction was investigated. Mechanism of formation and distribution of the intermetallic particles was determined and it was in good agreement with computational thermodynamic calculations results. It was found that the gradient microstructure for Al-TiAl3 insitu composite was obtained at 1173 K (900 degrees C) holding for 180 min which included blocky and plate particles. The Al/Ti interface was changed from flat to irregular form at 1173 K (900 degrees C) due to diffusion of Al in solid Ti. The role of temperature and holding time was found to be important for formation and distribution of both blocky and plate TiAl3 particles. A critical solute value equal to 2.7 wt% was determined for dissolved Ti. Higher concentrations than the critical value led to the formation of blocky particles (mainly during heating) while lower concentrations led to the formation of plate particles (mainly during cooling). The gradient distribution of intermetallic particles in Al matrix led to a gradient hardness.

  • 21.
    Yousefi, Maryam
    et al.
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran.
    Spatial and microstructural dependence of mechanical properties and wear performance of functionally graded Al-TiAl3 in situ composite2019Ingår i: SN Applied Sciences, ISSN 2523-3963, Vol. 1, nr 10, artikel-id UNSP 1190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effect of morphology and spatial distribution ofTiAl(3) particles on the hardness, the tensile behavior and the wear performance of functionally graded Al-TiAl3 in situ composite (FGC) was investigated. Initially, FGC was produced by interaction between solid Ti and liquid Al. Based on the spatial distribution and morphology of TiAl3 particles in the microstructure of FGC, three distinctive regions including blocky-particle region, mixed-particle region (blocky and short plate particles) and lengthy plate-particle region were studied. Results of this study showed that the blocky-particle region had promoted tensile strength as well as highly improved wear resistance. In addition, this region with higher density of blocky particles and low interparticle spacing showed a brittle fracture. The mixed-particle region with a lower density of blocky particles had a ductile fracture mechanism while the plate-particle region showed cleavage fracture.The dominant wear mechanism for regions including blocky particles was determined to be mild oxidation while it was delamination wear for regions containing plate particles. Finally, correlation between mechanical properties, wear resistance and microstructure of FGC was discussed.

  • 22.
    Yousefi, Maryam
    et al.
    Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Doostmohammadi, Hamid
    KTH, Skolan för industriell teknik och management (ITM), Materialvetenskap. Shahid Bahonar Univ Kerman, Dept Mat Engn & Met, Kerman 7618868366, Iran..
    Spatial and microstructural dependence of mechanical properties and wear performance of functionally graded Al-TiAl3 in situ composite2019Ingår i: SN APPLIED SCIENCES, ISSN 2523-3963, Vol. 1, nr 10, artikel-id UNSP 1190Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Effect of morphology and spatial distribution ofTiAl(3) particles on the hardness, the tensile behavior and the wear performance of functionally graded Al-TiAl3 in situ composite (FGC) was investigated. Initially, FGC was produced by interaction between solid Ti and liquid Al. Based on the spatial distribution and morphology of TiAl3 particles in the microstructure of FGC, three distinctive regions including blocky-particle region, mixed-particle region (blocky and short plate particles) and lengthy plate-particle region were studied. Results of this study showed that the blocky-particle region had promoted tensile strength as well as highly improved wear resistance. In addition, this region with higher density of blocky particles and low interparticle spacing showed a brittle fracture. The mixed-particle region with a lower density of blocky particles had a ductile fracture mechanism while the plate-particle region showed cleavage fracture.The dominant wear mechanism for regions including blocky particles was determined to be mild oxidation while it was delamination wear for regions containing plate particles. Finally, correlation between mechanical properties, wear resistance and microstructure of FGC was discussed.

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