| 1. |
- Brennhaugen, David D. E., et al.
(författare)
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Predictive modeling of glass forming ability in the Fe-Nb-B system using the CALPHAD approach
- 2017
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Ingår i: Journal of Alloys and Compounds. - : Elsevier. - 0925-8388 .- 1873-4669. ; 707, s. 120-125
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Tidskriftsartikel (refereegranskat)abstract
- Accurate values needed for the most commonly used indicators of good Glass Forming Ability (GFA) in alloys, i.e. the liquidus (T-l), crystallization (T-x) and glass transition (T-g) temperatures, are only available after successful production of the metallic glass of interest. This has traditionally made discovery of new metallic glasses an expensive and tedious procedure, based on trial-and-error methodology. The present study aims at testing the CALPHAD (Computer Coupling of Phase Diagrams and Thermochemistry) approach for predicting GFA in the Fe-Nb-B system by the use of the Thermo-Calc software and the thermodynamic database TCFE7. The melting temperatures and phase stabilities were calculated and combined with data for an atomic size mismatch factor, lambda, in order to identify and map potential high-GFA regions. Selected compositions in the identified regions were later produced by suction casting and melt spinning, and the potential success verified using X-Ray Diffraction (XRD). Differential Scanning Calorimetry (DSC) was also used to compare thermodynamic calculations for the model predictions, and evaluate standard GFA indicators. The model is found to fit well with literature data, as well as predict new bulk glassy compositions at and around Fe70.5Nb7B22.5. These results show promise in further predictive use of the model.
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| 2. |
- Beheshti, Reza, et al.
(författare)
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Black Dross Processing : Utilization of Black Dross in the Production of a Ladle Fluxing Agent
- 2017
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Ingår i: Journal of Sustainable Metallurgy. - : Springer. - 2199-3831 .- 2199-3823. ; 3:2, s. 265-273
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Tidskriftsartikel (refereegranskat)abstract
- In the present study, black dross (BD) residue, a hazardous by-product generated during secondary aluminum production, has been evaluated as a possible raw material for the production of a calcium aluminate-based ladle fluxing agent to be used in the steel industry. The thermally treated BD [pretreated black dross (PBD)] used as a starting material, consisted of approximately 49.5 ± 3.5 wt% alumina and 0.3 wt% chloride. The effects of different process parameters on the properties of the produced flux were experimentally investigated, i.e., the CaO/Al2O3 ratio, the sintering temperature and time, and the cooling medium. The prepared samples were all sintered in a rapid high-temperature inductive furnace, and later characterized by SEM–EDS, XRD, XRF, and DTA/TG analyses. Dissolution tests were also performed using a synthetic slag simulating the carryover. Based on the presently obtained results, it can be concluded that the utilization of PBD as the alumina source during the production of a calcium aluminate fluxing agent shows promising results, and the optimum process conditions were established to be 1523 K for 15 min as the sintering temperature and time, water as the cooling medium, and a CaO/Al2O3 ratio of 0.94. Utilizing PBD as a raw material in the production of a value-added product would significantly reduce the need for the disposal of BD as a waste, and thereby help to decrease the overall environmental impact. It would also provide economic benefit to both the steel and aluminum industry.
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| 3. |
- Beheshti, Reza, et al.
(författare)
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Reduction kinetics of commercial haematite pellet in a fixed bed at 1123-1273 K
- 2016
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Ingår i: Ironmaking & steelmaking. - : Taylor & Francis. - 0301-9233 .- 1743-2812. ; 43:5, s. 394-402
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Tidskriftsartikel (refereegranskat)abstract
- In the present study a model for future use in the modelling of moving bed direct reduction reactors has been developed. The model of a fixed bed reactor for the production of sponge iron from haematite incorporates both heat-and mass-transfer, as well as the chemical reduction rate. The model results were compared to the experimental data obtained from a lab scale reactor in the temperature range 1123-1273 K, as well as to the output from a simple model assuming isothermal conditions. The H-2/CO ratio (beta) of the reducing gas was in all cases varied from 0.8 to 2.0. Overall the non-isothermal model developed permits a more accurate representation of the experimental data than the isothermal estimates, with a typical discrepancy of only 1.3%.
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| 4. |
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| 5. |
- Fritzsch, R., et al.
(författare)
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Electromagnetic priming of ceramic foam filters (CFF) for liquid aluminum filtration
- 2016
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Ingår i: 142nd Annual Meeting and Exhibition, TMS 2013. - Cham : Springer International Publishing. ; , s. 973-979
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Konferensbidrag (refereegranskat)abstract
- Commercial Ceramic Foam Filters (CFF) of 30, 50 and 80 Pores Per Inch (PPI) have been primed, using magnetic field strengths of 0.06–0.2T, for periods of 1–10 minutes. The influence of time and field strength on the gas removal from the CFF structure, and the resulting improvements in filter productivity, are discussed. The obtained results are related to Finite Element Modeling (FEM) of the metal flow fields induced by the electromagnetic Lorentz forces. Higher filtration rates were obtained for 50 PPI magnetically primed, than for 30 PPI gravity primed filters. This suggests that electromagnetic priming offers an opportunity to use 50 PPI filters, with a higher overall filtration efficiency than 30 PPI filters, in existing cast house applications where the low productivity/high priming head of these filters would otherwise rule them out. Estimated filtration efficiency of different filter types are presented as functions of velocity and thickness.
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| 6. |
- Frostell, Claes, et al.
(författare)
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Tracheal implants revisited
- 2017
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Ingår i: The Lancet. - : ELSEVIER SCIENCE INC. - 0140-6736 .- 1474-547X. ; 389:10075, s. 1191-1191
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Tidskriftsartikel (refereegranskat)
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| 7. |
- Kennedy, M. W., et al.
(författare)
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Analytical and fem modeling of aluminum billet induction heating with experimental verification
- 2016
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Ingår i: Light Metals 2012. - Cham : Springer International Publishing. ; , s. 269-275
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Bokkapitel (övrigt vetenskapligt/konstnärligt)abstract
- Induction heating is commonly used in the re-heating of aluminum billets before forging or extrusion. Powerful finite element modeling (FEM) tools are available to assist in the design of such processes; however, such models should be validated by comparison with analytical solutions or experimental results to ensure accuracy. Induction heating experiments have been performed using a number of different coil designs and work piece dimensions at 50 Hz. Aluminum alloys with different electrical conductivities have been used, i.e. 6060 and A356. Process parameters such as: current, power, magnetic field, electrical conductivity, etc. have been measured with high precision instrumentation. Experimental data are presented and compared with equivalent 1D analytical and 2D axial symmetric FEM modeling results. The effect of frequency on the induction heating process is reviewed using the validated analytical and FEM models. Some recommendations are given with respect to appropriate modeling techniques, boundary conditions and numerical mesh sizes.
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| 8. |
- Zhao, Guo-Hua, et al.
(författare)
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Tribocorrosion studies of metallic biomaterials : The effect of plasma nitriding and DLC surface modifications
- 2016
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Ingår i: Journal of The Mechanical Behavior of Biomedical Materials. - : Elsevier. - 1751-6161 .- 1878-0180. ; 63, s. 100-114
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Tidskriftsartikel (refereegranskat)abstract
- The medical grade pure titanium, stainless steel and CoCrMo alloy have been utilized as biomaterials for load-bearing orthopedic prosthesis. The conventional surgery metals suffer from a combined effect of wear and corrosion once they are implanted, which may significantly accelerate the material degradation process. In this work, the tribocorrosion performance of the metallic biomaterials with different surface modifications was studied in the simulated body fluid for the purpose of investigating the effect of the surface treatments on the tribocorrosion performance and eventually finding the most suitable implantation materials. The metals were subjected to surface modifications by plasma nitriding in different treatment temperatures or physical vapor deposition (PVD) to produce diamond-like carbon (DLC) coating, respectively. The dry wear and tribocorrosion properties of the samples were evaluated by using a reciprocating ball-on-disc tribometer equipped with an electrochemical cell. Prior to the tribocorrosion tests, their electrochemical behavior was measured by the potentiodynamic polarization in phosphate buffer saline (PBS) solution at room temperature. Both stainless steel and CoCrMo after low temperature nitriding kept their passive nature by forming an expanded austenite phase. The DLC coated samples presented the low anodic corrosion current due to the chemical inertness of the carbon layer. During the tribocorrosion tests at open circuit potential, the untreated and low temperature nitrided samples exhibited significant potential drop towards the cathodic direction, which was a result of the worn out of the passive film. Galvanic coupling was established between the depassivated (worn) area and the still passive (unworn) area, making the materials suffered from wear-accelerated corrosion. The DLC coating performed as a solid lubricant in both dry wear and tribocorrosion tests, and the resulting wear after the tests was almost negligible.
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