Thesis (Ph. D.)--Princeton University, 1919. / Cover title. Bibliography: p. 24.

Thesis (Ph. D.)--Princeton University, 1919. / Cover title. Bibliography: p. 24.

Thesis (Ph. D.)--University of Wisconsin--Madison. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 167-175).

Thesis (PhD)-Open University. BLDSC no.DX181454.

Thesis (Ph. D.)--Pennsylvania State College, 1936. / "By D. McLachlan, Jr., and Wheeler P. Davey." "Reprinted from the Transactions of the American society for metals."

Made available in DSpace on 2014-10-09T12:23:59Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:07:58Z (GMT). No. of bitstreams: 1 01070.pdf: 2677585 bytes, checksum: 886f210d3f6431136fa09330d68b8fa2 (MD5) / Dissertacao (Mestrado) / IEA/D / Faculdade de Filosofia Letras e Ciencias Humanas, Universidade de Sao Paulo - FFLCH/USP

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An investigation was conducted on the mechanisms of bond formation between alloys of nickel and single crystals of alumina. Nickel-titanium, nickel-chromium, and nickel-zirconium powder mixtures were cleaned with purified hydrogen gas at 800°C and were individually melted under vacuum (10⁻⁵ m.m. of Hg) in contact with alumina. Interfacial energy measurements at 1500°C were made by the sessile-drop method. The bond surfaces were examined by X-ray fluorescence and X-ray diffraction techniques. The bond formation in all cases appeared to involve two basic mechanisms - metal solute segregation and interfacial reaction. By interfacial measurements and X-ray fluorescence analyses, the solute atoms, titanium and chromium, were shown to be selectively adsorbed at the metal-ceramic interface. Interfacial reaction products were detected by X-ray diffraction methods. The adsorbed titanium reacted with the alumina to produce an interfacial layer of alpha titanium sesqui oxide (⍺-Ti₂0₃). Adsorbed chromium similarly reacted with the alumina to form an interfacial compound. However, this compound could not be identified. With nickel-zirconium alloys, the violence of the reaction between zirconium and alumina made experimental measurements impossible. / Applied Science, Faculty of / Mining Engineering, Keevil Institute of / Graduate

Studies have been made of both the solid state and supersolidus sintering characteristics of spherical cupronickel powders. Observations were made of the structural changes and shrinkage rates in specimens sintered in vacuum and in hydrogen. It was concluded that the early stage of solid state sintering (up to one hour at 1200°C) was dominated by Nabarro-Herring creep. Calculations of the stresses at necks during sintering were consistent with the proposed mechanism. No solute segregation to necks occurred during sintering, contrary to earlier observations by Kuczynski with other copper alloys. When pre-sintered cupronickel powder ( 68 μm) aggregates were heated to a temperature above the equilibrium solidus, melting was nucleated first at high angle grain boundaries (necks) and particle surfaces (voids). Most melting was intragranular, nucleated at interdendritic sites of above-average copper content. Solid-liquid equilibrium was established in less than one minute at the supersolidus temperature. The dihedral angle in the system was less than or equal to zero. Growth of solid grains during supersolidus sintering obeyed a parabolic rate law consistent with a model of growth due to phase boundary reaction-controlled solution and precipitation. Shrinkage during supersolidus sintering proceeded in several distinct stages. Prior to attainment of equilibrium; i.e. within the first minute above the solidus (Stage 1), contraction could be attributed to a melting and melt accommodation sequence, plus flattening by the the local operation of solution and precipitation. Beyond this (Stages 2 and 3) all densification was attributed to solution-precipitation, including grain growth. In the final stage of shrinkage (Stage 3) the rate of contraction was controlled by the rate of escape of gas from closed pores. Comparisons have been made between the supersolidus sintering of cupronickel and the liquid-phase sintering of iron-copper. The processes are seen to have little in common. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

A Dissertation submitted to the Faculty of Science, University of the Witwatersrand, Johannesburg, for the Degree of Master of Science / A simple three-dimensional model of a high y' volume fraction Ni-based alloy is developed. The model is based on the idea that a unit volume in the superalloy can be represented by a cuboidal precipitate with thin 'slabs' of matrix material 'stuck' onto its faces in such a way that coherency is maintained. Rafting is investigated by considering the changes in total energy whon the cuboidal precipitates start to flatten into plate shapes or lengthen into rod shapes. It is assumed that inelastic effects are negligible. Internal and external stresses and strains are determined. Expressions for the derivative of the total energy with respect to a shape parameter are then calculated in the absence of applied stress and in the presence of applied stress. Predictions of rafting behaviour are made for six alloys. Excellent agreement is found with experimental evidence but it is suggested that the agreement is fortuitous. / AC 2018