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[en] This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo-based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data
[en] Gas phase permeation techniques have been used to determine the permeability and diffusivity of deuterium in a nominal Mo-47.5Re (wt.%) alloy. The deuterium solubility was deduced from the permeability and diffusivity. Refractory metal alloys of molybdenum and rhenium have good mechanical properties at elevated temperatures and appear to be mechanically stable in the presence of hot hydrogen. For such reasons, alloys such as Mo-47.5Re are being considered for use in advanced aerospace engines where they will be in contact with high temperature gaseous hydrogen. Knowledge of the bulk hydrogen transport parameters for these alloys is, however, very limited or non-existent. A measurement of the hydrogen permeability constant for Mo-50Re (wt.%) has been reported by Svedberg, but diffusivity and solubility values have not been reported. Since Mo-47.5Re is composed predominantly of Mo and has a similar BCC crystal structure, the results from the present study will be compared with corresponding results obtained for pure Mo. For experimental reasons to be discussed, deuterium has been substituted for hydrogen. This substitution should scale the relative magnitude of the determined parameters as compared with hydrogen values, but it is not expected to affect their overall temperature dependence. The present measurements were made over a temperature range from 340 C to 850 C and the pressure range from 1.3 x 103 N/m2 to 1.0 x 105 N/m2
[en] Using the methods of diffraction electron microscopy studied were the cellular dislocation structure, orientations and disorientations in the local areas of a deformed molybdenum foil. The detected electron microscopic orientations correspond to the strong component of the texture and clarify the less strong component. The dislocation structure of rolling is very heterogeneous and may be conventionally divided into three cellular structures. The differences in the substructure of the components of the texture of rolling in polycrystalline molybdenum have turned out to be less clear than in the event of the axial texture of hydroextrudates
[en] Highlights: • Polycrystalline elastic properties of γ-phase U – 8 wt% Mo are determined between 25 and 650 °C. • First measurement of temperature-dependent stiffness tensor components for a U-Mo alloy. • Literature review of U-Mo elastic properties as a function of temperature and composition. • Discussion of the unique auxetic single-crystalline elastic properties predicted for U-Mo. • Demonstration that microstructure has a negligible effect on U-Mo elastic properties. Abstract: Polycrystalline elastic moduli and stiffness tensor components of γ-phase U – 8 wt% Mo have been determined by resonant ultrasound spectroscopy in the temperature range of 25-650°C. The ambient temperature elastic properties are compared to results measured via other experimental methods and show reasonable agreement, though there is considerable variation of these properties within the literature at both the U – 8 wt% Mo composition and as a function of Mo concentration. The Young’s modulus of U – 8 wt% Mo measured in this study decreases steadily with temperature at a rate that is slower than trends previously observed at similar Mo concentrations, though the difference is not statistically significant. This first measurement of the temperature dependent elastic stiffness tensor of a polycrystalline U-Mo alloy clarifies that the behavior of the Young’s modulus is due to a strongly weakening C11 polycrystalline stiffness tensor component, along with milder decreases in C12 and C44. The unique partially auxetic properties recently predicted for singlecrystalline U-Mo are discussed in regard to their possible impact on the polycrystalline behavior of the alloy.
[en] Peculiarities of MeC crystals morphology in synthetic Fe-Mo-C alloys (35.0-52.5% Mo and 1.26-1.7% C) are investigated and correlation bound between morphology and internal structure of this carbide is revealed. It is shown that Me6C carbide crystals in Fe-Mo-C melts at 70-100 deg/min cooling rates grow in the form of octahedrons having most often skeleton structure and ''pseudodendrites''. Nature of location of layers and macrostages of growth on (111) faces permits to suppose that eta-crystals grow by combined normal-laminated mechanism. Octahedral form of Me6C carbide crystal growth is mainly caused by peculiarities of its internal structure-packing density of low-index faces which is predetermined by the nature of distribution of strong covalent Mo-C bounds in their elementary layers