In this thesis, the results of oxidation and decarburization experiments with pure iron-carbon alloys over the temperature range 800 - 950ºc, and in atmospheres of varying carbon monoxide - carbon dioxide ratio are reported. Most of the experimental work is concerned with a 1.065 weight percent carbon alloy at temperatures where austenite is the stable phase. Complex kinetic behaviour was observed for this alloy in the range 10 - 100 volume percent carbon dioxide. An analysis is given which in turn associates the kinetics with a pure diffusion controlled decarburization model and a pure surface controlled decarburization model. The latter best represents the interaction of the decarburization mechanism with the scaling process on Y - iron. Metallographic evidence is provided where possible in support of the results of the afore-mentioned analysis. Mathematical relations are introduced which attempt to describe qualitatively the kinetics of the carbon alloys in all the atmospheres employed. A statement is made as to the applicability of the model to carbon steels in general at temperatures where austenite is the stable phase and where the atmospheres employed are of various carbon monoxide - carbon dioxide ratio. / Thesis / Master of Science (MS)

<P> A study has been made of the transformation of deoxidation products in the Fe-V-0 system in the temperature range 1545 -1640°C, using galvanic cells with solid electrolytes. The cells used were in the form of Zr02 (caO) immersion probes and Th02(Y2o2) crucible assemblies. The fields of study of Fev2o4(spinel) and v2o3 were established with respect to oxygen activity and temperature. </p> / Thesis / Master of Engineering (MEngr)

Fatigue and dispersion strengthening are reviewed generally. Experiments are described in which thin film transmission electron microscopy, as well as optical and electron fractography were employed to elucidate the mechanism of fatigue failure in dispersion strengthened nickel. It was found that whereas fatigue crack initiation occurs as in conventional materials, the propagation of both fatigue and tensile cracks is abnormal. The material fails in shear wherever possible although this is prevented where triaxial tensile stresses exist. Particle-matrix detachment does not occur during either tensile or fatigue stressing. / Thesis / Master of Science (MS)

Current theories to explain the st!'engthening caused by ordering a.re reviewed. Localization of slip was observed to occur during high strain reverse bending, and was associated with crack initiation. A mechanism for the breakdown of order strengthening mechanisms is suggested as an explanation for this localization. / Thesis / Master of Science (MS)

The relative merits of methods of determining the density of dislocations are reviewed. In particular, consideration has been given to the evidence available tending to indicate a loss of dislocations from foils of deformed metal during thinning processes preparatory to viewing in the electron microscope. By measurement of the electrical resistivity ratio, 293˚K./77˚K., during thinning, annealed specimens of super-purity aluminum foil were shown to obey Fuch’s theory for thin films, but cold-rolled specimens could not be fitted to the theory. This discrepancy has been attributed to the loss of dislocations from the cold-rolled material, and the results are shown to be consistent with a “loss-fringe” model of dislocation loss from the surface. / Thesis / Master of Science (MSc)

In this thesis the nature and strengthening effect of the various precipitates in Al-4% Cu are reviewed, followed by a literature survey on the response of this alloy to fatigue. The first experiments described were carried out to measure the Bauschinger effect and the results of these are presented. The experimental study was further extended by cyclic straining corresponding to fatigue conditions and the results obtained are presented graphically and through electron micrographs. The fatigue behaviour was further investigated at liquid air temperature. Also, the effect of heat treatments carried out during the interruption of fatigue on a specimen containing metastable θ" precipitates is reported. All the experiments were carried out on single crystals and most of them with 112 orientation as indicated later. / Thesis / Master of Science (MS)

This dissertation describes the determination of the equilibrium constant for the reduction of ferrous oxide by manganese to yield manganese oxide and iron. The experimental work was carried out over the temperature range of 1650°C to 1870°C. The results from the present work were combined with reliable published data to give what is considered to be the best relationship between the equilibrium constant and the temperature. The difference between this study and previous work on this topic is the radically new experimental approach. While previous workers used crucible techniques to achieve equilibrium for their system and standard wet chemical analysis, the method used here involved levitation melting and analysis by the electron probe micro-analyser. / Thesis / Master of Engineering (ME)

The Digitization Centre has determined that page 49 was not published with the original copies of this thesis. / The validity of current theories of precipitate morphology is dependent on the microscopic nature of the precipitate-matrix interface. It is the purpose of this thesis to investigate, by electron microscopy interfacial structure and mobility in precipitation reactions pertaining to these theories. In particular the B->a Widmanstatten reaction in 60:40 brass is investigated and compared with the B->y reaction in a Cu-Zn-Sn alloy. / Thesis / Master of Science (MS)

The Portevin-le Chatelier effect in a copper-3.2 at.% tin alloy has been used to investigate the rate of vacancy production during reversed plastic flow. The production rate per unit strain has been shown to be approximately half the value found for straight tensile deformation. It was inferred from this that fatigue is not a highly efficient method for producing vacancies. The relationship between the dislocation density and the tensile plastic strain for this alloy has been determined by transmission electron microscopy. It was found to obey the law, p = const. E^1.17±0.13. It was also found that during reversed plastic flow this law was no longer valid. / Thesis / Master of Science (MSc)

In this thesis, the theory of metal crystal evaporation and of vapour pressure determinations are presented, followed by a literature survey on the evaporation characteristics of iron, chromium and alloys of iron - chromium. Results are presented for an investigation carried out on the free evaporation kinetics of iron base alloys containing 5 percent and 25 percent chromium for the temperature range 900°C to 1080°C. Also, a complete description of the surface topographies of evaporated specimens is presented using normal, hot stage and interferometric microscopic techniques. These results are correlated in terms of the evaporation theory and pertinent experimental data reported for other metallic systems. / Thesis / Master of Science (MSc)