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Microyielding and flow in niobium alloy crystalsWilson, F. Graham January 1969 (has links)
Oriented single crystals of niobium and dilute alloys with molybdenum and tantalum were deformed in tension between 77°K and 500°K, and the macroflow and slip parameters established. At high temperatures the main effect of alloying was to increase the flow stress, considerably more with molybdenum than with tantalum. The observed yield drop and subsequent plastic flow were explained in terms of a stability theory relating changes in yield and work hardening parameters with temperature and addition of solute.
A technique was developed for measuring small plastic strains in the microflow region, and for recording the dynamic transition to macroflow. From studies on pure niobium between 77°K and 295°K, the nature of dislocation motion at small strains was established; microflow was explained in terms of a transition from edge dislocation motion to screw dislocation motion at the macroflow stress. Interstitial effects were found to be particularly significant during microflow, and are probably important in determining the low temperature flow stress in: even the highest purity bcc metals. A further low temperature contribution
comes from a directional component of the internal stress field which depends on the distribution of dislocations rather than on their density.
Microflow curves were obtained for niobium alloy crystals, land the interaction of dislocations with substitutional solute atoms established. In contradiction to previous suggestions, substitutional solute was found to restrict the mobility rather than the multiplication of dislocations. The elastic contribution of solute atoms to the internal stress field was confirmed, although a quantitative theory for bcc alloys does not yet exist.
Peierls stress considerations alone were found to be incapable of explaining either the temperature sensitivity of flow or the low temperature solution softening; the short range interaction of interstitials with the dislocation core was considered to be more significant. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate
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Effect of cool deformation on mechanical properties and microstructure of Nb microalloyed steelsFatehi, Arya. January 1900 (has links)
Thesis (M.Eng.). / Written for the Dept. of Mining and Materials Engineering. Title from title page of PDF (viewed 2009/06/17). Includes bibliographical references.
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Study of Nb/AlOx̲/Nb SIS tunnel junctions fabricated by electron beam evaporation at UHVAl-Ghamdi, F. M. January 1988 (has links)
No description available.
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Critical current distributions and the V(1) transition in Nb-Ti superconducting compositesNarang, Girish 16 January 1996 (has links)
It is well established that the extended range V(I) transition behavior in
filamentary superconducting composites depends strongly on the processing
conditions of the composite. Based on previous work, a model proposed by
Warnes et al predicts that the second derivative of the V(I) transition is related to
a more fundamental property the critical current distribution in the composite.
The present work consolidates the said model by showing that in spite of
the V(I) transition being dependent on the matrix resistance, the second
derivative is relatively independent. Also, the second derivative V(I) curve has
been correlated to the critical current distributions and area distributions in
monofilament and multifilamentary superconductors, using image analysis
techniques. The work provides a better understanding of the critical current
distributions in composite superconductors and can be an effective tool for
measuring conductor quality more precisely.
In addition to this, image analysis techniques have been used to study the
effect of processing on the structure of wires - and have been related to the
predictions of a model of inplane stresses in composites. / Graduation date: 1996
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Searching for new niobium oxide based superconductorsBacon, Paul Eric 21 August 1995 (has links)
Graduation date: 1996
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Nouveaux matériaux à base de Niobium et de Molybdène pour turbines aéronautiques relations de phases et oxydation ; élaboration de nouveaux revêtements /Zamoum, Ferhath Vilasi, Michel. January 2008 (has links) (PDF)
Thèse de doctorat : Physique et Chimie de la Matière et des Matériaux : Nancy 1 : 2008. / Titre provenant de l'écran-titre.
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POLAROGRAPHIC INVESTIGATION OF SOME NIOBIUM COMPLEXESKirby, Robert Emmet, 1921- January 1961 (has links)
No description available.
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A first-principles study of the niobium-hydrogen systemLi, Changlin 12 1900 (has links)
No description available.
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Organometallic thiolate complexes of the early transition metalsSpence, Malcolm Andrew January 1998 (has links)
No description available.
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Flow-injection solvent extraction of metal chelatesPornsinlapatip, Pornpun January 1998 (has links)
No description available.
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