No description available.

Thesis (Ph. D.)--Lehigh University, 2003. / Includes vita. Includes bibliographical references (leaves 198-205).

No description available.

The damage clusters produced by low dose, 80 keV Ni⁺ and W⁺ heavy-ion bombardment of pure nickel; of two nichrome alloys (with 8% and 17%Cr); and of a ternary alloy and 321 stainless steel which have the same base composition (Fe/Ni10%/Cr17%) have been studied by means of transmission electron microscopy. In all cases where the defects could be identified with confidence they were found to be vacancy in nature. Most of the defects were identified as Frank loops, some of which had partially dissociated. The number of loops that were identified as dissociated and the average degree of dissociation were dependent on the stacking fault energy γ, being greater in the low-γ ternary alloy and the stainless steel than in the high-γ nickel and nichrome alloys. In the high-y materials a small proportion (< 5%) of perfect loops was also observed. Defect yield values were between a factor of 2 and 5 higher for W⁺ ion bombardment than for the corresponding Ni⁺ ion irradiations, but the effect on the mean defect size and cascade efficiency was much less pronounced. In the case of the Ni⁺ ion bombardment, the defect yields in the two nichrome alloys were lower than in pure Ni. No such effect was observed for the W⁺ ion irradiations, when defect yield and cascade efficiency values very similar to those of pure nickel were obtained. The defect yield in the W⁺ ion irradiated ternary alloy was considerbly smaller than in the nichrome alloys and there was a further major decrease in the stainless steel. These reductions in defect yields were not accompanied by a change in the mean defect size nor in the distribution of the defect sizes which were very similar in all the materials for irradiation by a given ion species. The defect yield in W⁺ ion irradiated Ni remained constant with increasing irradiation temperature up to ~450°C and then decreased sharply at higher irradiation temperatures. The defect yield in W⁺ ion irradiated Ni/Cr17% remained constant up to at least 500°C. Possible physical explanations for these results are discussed.

This research is concerned with identifying and characterizing four solid-state precipitation reactions in the W-Ni-Fe system that can be induced by appropriate heat treatments. Previous work in this area is reviewed, and a general overview of the research on this system that may, directly or indirectly, further the understanding of microstructure/mechanical property relationships in the W-Ni-Fe heavy alloy is presented. The many metallographic and analytical techniques that have been employed in the course of this investigation are also briefly reviewed. The specific precipitation reactions studied in the 90W-5Ni-5Fe heavy alloy are listed and briefly described. Interfacial precipitation - interfacial precipitates at the W-andgamma; and andgamma;-andgamma; boundaries were found to be andeta;-carbides. This morphology is expected to severely embrittle the alloy. Matrix-phase precipitation - discontinuous precipitation of W was observed in the matrix region. W-W grain boundary precipitation - W-W grain boundary allotriomorphs (andgamma;-phase) were identified and characterized. W-phase precipitation hardening - fine scale precipitation in the W-phase was found to strengthen the alloy. Deformation prior to aging significantly increased the rate of precipitate nucleation. TEM contrast analysis showed the precipitates to be plate-like with a {100} habit plane, and the strain in the W lattice normal to the precipitates was found to be tensile in nature. Matrix-composition alloys were manufactured to simulate the andgamma;-phase in the 90W-5Ni-5Fe alloy. Metallographic observations of these alloys furthered the understanding of reactions 1) and 2) above. These results are discussed in terms of (a) current theories of solid-state precipitation and (b) the influence of the various morphologies on mechanical properties.

No description available.

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

Thesis (M. App. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 90-94). Also available in electronic format on the Internet.

Thesis (M.App.Sc.) - Carleton University, 2005. / Includes bibliographical references (p. 109-120). Also available in electronic format on the Internet.

Dissertation (Ph.D.)--Auburn University, 2006. / Abstract. Vita. Includes bibliographic references.