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| 2. |
- Aune, Ragnhild E., et al.
(författare)
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Measurement of Thermophysical Properties of Liquid Metallic Alloys in a Ground- and Microgravity Based Research Programme - the ThermoLab Project
- 2005
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Ingår i: Microgravity, science and technology. - 0938-0108 .- 1875-0494. ; 16:1-4, s. 7-10
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Tidskriftsartikel (refereegranskat)abstract
- The ThermoLab project is concerned with the measurement of the thermophysical properties of industrial alloys in the liquid phase. The project combines long and short duration microgravity measurements based on containerless processing with an electromagnetic levitation device and a ground based experimental programme using conventional and containerless processing techniques. An overview of the project and representative results from the ground based experimental programme are given. Alloys investigated included Ni-based, Fe-based, a Cu-Sn-Mg alloy and a gamma-TiAl alloy.
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| 3. |
- Aune, Ragnhild E., et al.
(författare)
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Surface Tension and Viscosity of Industrial Alloys from Parabolic Flight Experiments : Results of the ThermoLab Project
- 2005
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Ingår i: Microgravity, science and technology. - 0938-0108 .- 1875-0494. ; 16:1-4, s. 11-14
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Tidskriftsartikel (refereegranskat)abstract
- The surface tension and the viscosity of a series of industrial alloys have been measured by the oscillating drop technique with an electromagnetic levitation device under reduced gravity conditions in several parabolic flights. It was demonstrated that the 20 seconds of reduced gravity available in a parabola were sufficient for melting, heating into the liquid phase, and cooling to solidification of typically 7 mm diameter metallic specimen. The surface tension and the viscosity were obtained from the frequency and the damping time constant of the oscillation which were evaluated from the temperature signal of a highresolution pyrometer. Alloys processed included steels, Ni-based superalloys, and Ti-alloys which were supplied by industrial partners to the project. Three to four parabolas were sufficient to obtain the surface tension and the viscosity over a large range in temperature.
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| 4. |
- Aune, Ragnhild E., et al.
(författare)
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Thermodynamic approach to physical properties of silicate melts
- 2005
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Ingår i: Ironmaking & steelmaking. - : Informa UK Limited. - 0301-9233 .- 1743-2812. ; 32:2, s. 141-150
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Tidskriftsartikel (refereegranskat)abstract
- The thermophysical properties of silicate melts are strongly structure dependent. It is well known that the viscosity of slags increases with increasing degree of polymerisation of the silicate anion. Even the thermodynamic properties of slags are dependent on the species type and population in the melt. Thus, a link between the thermophysical and thermochemical properties of silicate melts is logically expected. The present paper elucidates the salient features of Darken's excess stability approach to the Gibbs energy of solution as applied to the viscosities of silicate melts. It is demonstrated that the second derivatives of the viscosities of binary silicate melts with respect to composition indicate maxima corresponding to the existence of stable compounds in these systems. The concept has been successfully applied to the following systems: Al2O3-SiO2, CaO-SiO2, FeO-SiO2, MgO-SiO2 and MnO-SiO2. In all cases, the second derivative plots of viscosities with respect to composition show peaks corresponding to the metasilicates. The second derivatives of the activation energies of viscous flow with respect to temperature have earlier been shown to reflect the formation of associates/embryos in homogeneous silicate melts, indicating the readiness of the melt to separate a solid phase. Thermodynamic coupling of thermal diffusivities in the case of the CaO-Al2O3-SiO2 system from laser flash measurements of these slags, as a function of temperature, has been examined as part of the present study. Densities have been estimated from integral molar enthalpies in the case of silicate systems, and the results are presented.
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| 5. |
- Aune, Ragnhild E., et al.
(författare)
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Thermophysical properties of IN738lc, MM247lc and CMSX-4 in the liquid and high temperature solid phase
- 2005
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Ingår i: Superalloys 718, 625, 706 and Derivatives, Proceedings. - : TMS. ; , s. 467-476
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Konferensbidrag (refereegranskat)abstract
- Thermophysical properties of the Ni-based superalloys CMSX-4, IN738LC, and MM247LC have been measured in the liquid and high-temperature solid phase. Properties included calorimetric, thermal transport, the surface tension, and the viscosity. Experiments have been performed in ground-based laboratory using classical calorimetry and rheometry as well as under reduced gravity conditions in an electromagnetic levitation device on board parabolic flights. In this contribution, an overview of the various properties of three Ni-based superalloys is given with emphasis on the surface tension and viscosity as obtained from the parabolic flight experiments. The measurements were performed within a program called ThermoLab dedicated to the measurement of thermophysical properties of industrial alloys.
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| 6. |
- Morales, R., et al.
(författare)
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Hydrogen reduction of complex oxides - a novel route toward the production of nanograined alloys and intermetallics
- 2005
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Ingår i: Scandinavian journal of metallurgy. - : Wiley. - 0371-0459 .- 1600-0692. ; 34:2, s. 108-115
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Tidskriftsartikel (refereegranskat)abstract
- One of the major obstacles in the incorporation of nanomaterials in high technology is the lack of new processes for the bulk production of the materials with compositions tailored to suit the application. Oxides can potentially be reduced to metals, intermetallics or alloys by hydrogen or natural gas. The formation of homogeneous alloys and intermetallics by this method has been confirmed by a number of experimental studies. The kinetics of hydrogen reduction of pure oxides of transition metals as well as complex tungstates, molybdates, titanates, aluminates and chromate were investigated by thermogravimetry. The formation of homogeneous alloys and intermetallics was confirmed by these studies. Arrhenius activation energies of the reduction reactions could be linked to the stabilities of the complex oxides. The products were found to have nanograin structure. Bulk processing through hydrogen reduction route was examined in the case of iron molybdate using a fluidized bed reactor.
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| 10. |
- Teng, L. D., et al.
(författare)
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Thermodynamic investigations of the Mn-Ni-C-N quarternary alloys by solid-state galvanic cell technique
- 2005
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Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 388:2, s. 250-257
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Tidskriftsartikel (refereegranskat)abstract
- In view of the important applications of carbides and nitrides of transition metals in the hard materials industries, the thermodynamic activities of manganese in Mn-Ni-C-N alloys have been studied by solid-state galvanic cell technique with CaF2 as the solid electrolyte. The phase compositions and microstructure of various alloys have been analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Nitrogen was introduced into the alloy by equilibrating with N-2 gas. It was established during the experiments that the solubility of nitrogen in the alloys was affected by the carbon content. A (Mn,Ni)(4)(N,C) nitride was formed during the nitriding procedure in the alloys. The electromotive force (EMF) measurements were carried out in the temperature range 940-1127 K in order to determine the activities of Mn in the alloys. The activities of manganese were calculated and compared with those of the corresponding Mn-Ni-C ternary alloys.
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