The purpose of this diploma project has been to investigate the elastic properties of hexagonal close-packed Fe-Ni-Mg alloys at high pressure. Recent research has suggested that iron and magnesium can form an alloy under high pressure because of the great compressibility of the magnesium atoms. This also makes it possible for magnesium alloying with nickel atoms which are very similar to iron so that we get Fe-Ni-Mg alloys. Learning more about the elastic properties of iron alloys at high pressure will give us a better understanding of the inner core of our planet, which is believed to be composed primarily of iron. The calculations are based on a ab-inito method supported on the Density Functional Theory. The calculations were performed with a simulation package based on the Exact Muffin-Tin Orbitals theory, in conjuction with the Coherent Potential Approximation. The effects that small impurities can have on iron are remarkable.

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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.

Thesis (Ph.D.) -- McMaster University, 1998. / Includes bibliographical references (p. 295-305). Also available via World Wide Web.

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

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

Thesis (Ph. D.)--Lehigh University, 1998. / Includes vita. Includes bibliographical references (leaves 168-180).

Thesis (doctoral)--Helsinki University of Technology, 2002. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1967. / Typescript. Vita. Description based on print version record. Includes bibliographical references.