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Theses

Incorporation d'éléments réfractaires dans les alliages à base de niobium

Abstract : This thesis presents the thermodynamic, kinetics and physical aspects of the development of metallurgical alloys niobium based with high characteristics. The main event is the incorporation of molybdenum in a ternary alloy niobium-aluminum-titanium. To meet the requirements of purity and structural uniformity, alloying is the major step. The technique of inductive cold crucible is a method well suited to this development. Joined to the cold crucible, a method of measuring the temperature of the surface of the liquid bath is used, which eliminates any contamination problem. Measurements are performed by infrared-ultratviolet-coupled pyrometer allowing to separate the effects of temperature change and variations in emissivity. Data on the equilibrium phase at high temperature niobium-titanium-aluminum system and the system derivative by addition of molybdenum and zirconium are established. A modification of the projection of the liquidus niobium-titanium-aluminum system and an isothermal section at 1200 °C are available. The evolution of the phase boundaries for a zirconium content of 1% and the molybdenum content of 4% and 8% (atomic fraction) is specified. These results are observed for the raw sample and annealed at 1200 ° C. To better understand the phenomena that influence the dissolution of a refractory addition (niobium, molybdenum or nickel) in a aluminum metal bath, a physicochemical model is proposed. This numerical model, focused on phenomena at the interface, describes the mass and heat transfer phenomena. It takes into account the solid-liquid equilibria and the thermic effect of mixing. All the answers provided to the development of the problem of refractory alloys should allow a more rational conduct of the elaboration.
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Submitted on : Thursday, June 30, 2016 - 2:07:44 PM
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  • HAL Id : tel-01340114, version 1

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Annie Antoni-Zdziobek. Incorporation d'éléments réfractaires dans les alliages à base de niobium. Electromagnétisme. INSTITUT NATIONAL POLYTECHNIQUE DE GRENOBLE, 1995. Français. ⟨tel-01340114⟩

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