Thesis (Ph. D.)--University of Canterbury, 2007. / Typescript (photocopy). Includes bibliographical references (p. 185-196). Also available via the World Wide Web.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 172-182). Available also in a digital version from Dissertation Abstracts.

A dissertation submitted to the faculty of Engineering, University of the Witwatersrand, Johanuesburg, in fulfilment of the requirements for the degree of Master of Science in Engineering. / Ferritic stainless steels possess a number of properties which render them superior to austenitic stainless steels in certain applications. The ferritic stainless steels are highly resistant to stress-corrosion cracking and are generally of lower cost. Previous work had shown that the corrosion properties of the ferritic steels were optimised at a chromium content of forty percent. Extensive research had already characterised the mechanical and corrosion behaviour of the Fe"40Cr alloy in the cast and wrought form. This investigation involves the development of the material by powder metallurgy processing. Particular emphasis is placed on a proprietary powder production technique as well as on powder consolidation by Hot Isostatic Pressing. The effect of Ni, Mo, Ru, Nb, Al and Fe additions and well as various techniques of introducing these additions are examined. The unique effect of powder metallurgy manufacture on microstructure and the kinetics of sigma phase formation is highlighted. Corrosion tests in various concentrations of sulphuric acid and an industrial field trial were performed. It was found that combined Ni and Mo contents exceeding four percent resulted in severe embrittlement due to widespread formation of sigma phase during the HIP process. The use of powder metallurgy techniques was also found to enhance the kinetics of sigma phase formation in a particular alley when compared to the as-cast state. Direct additions of Fe powder were successful in inhibiting embrittlement, possibly due to a mechanism of Fe diffusion into Cr-rich regions. This lowered of the Cr content in these regions, thereby reducing the tendency for sigma precipitation. Corrosion tests indicate satisfactory resistance for the Fc-40Cr-2Ni-2Mo alloys in 70 weight percent sulphuric acid at 50°C. Alloys with 0.2 percent Ru additions were found to be especially resistant, due to the role of Ru as a cathodic modifier. The method of mixing and diffusion bonding metallic powders of varying composition was found to be feasible and certain novel combinations of Ni and Fe-rich alloys exhibited satisfactory corrosion resistance. A mathematical diffusion model was found to provide an order of magnitude approximation of the time required for hornogentsation in a certain mixture of powders. / Andrew Chakane 2018

No description available.

Graduation date: 1999

No description available.

This work details an investigation into the production of porous shape memory alloys (SMAs) via hot isostatic press (HIP) from prealloyed powders. HIPing is one of three main methods for producing porous SMAs, the other two are conventional sintering and selfpropagating hightemperature synthesis (SHS). Conventional sintering is characterized by its long processing time at near atmospheric pressure and samples made this way are limited in porosity range. The SHS method consists of preloading a chamber with elemental powders and then initiating an explosion at one end, which then propagates through the material in a very short time. HIPing provides a compromise between the two methods, requiring approximately 5 hours per cycle while operating in a very controlled environment. The HIPing method gives fine control of both temperature and pressure during the run which allows for the production of samples with varying porosity as well as for finetuning of the process for other characteristics. By starting with prealloyed powder, this study seeks to avoid the drawbacks while retaining the benefits of HIPing with elemental powders. In an extension of previous work with elemental powders, this study will apply the HIP method to a compact of prealloyed powders. It is hoped that the use of these powders will limit the formation of alternate phases as well as reducing oxidation formed during preparation. In addition, the nearspherical shape of the powders will encourage an even pore distribution. Processing techniques will be presented as well as a detailed investigation of the thermal and mechanical properties of the resulting material.

Thesis (Ph. D.)--Ohio State University, 2006. / Title from first page of PDF file. Includes bibliographical references (p. 346-353).

Thesis (M.Sc.)--City University of Hong Kong, 2005. / At head of title: City University of Hong Kong, Department of Physics and Materials Science, Master of Science in materials engineering & nanotechnology dissertation. Title from title screen (viewed on Aug. 31, 2006) Includes bibliographical references.

Copper is a material of interest to Additive Manufacturing (AM) owing to its outstanding material properties, which finds use in enhanced heat transfer and electronics applications. Its high thermal conductivity and reflectivity cause challenges in the use of Powder Bed Fusion AM systems that involve supplying high-energy lasers or electron beams. This makes Binder Jetting a better alternative as it separates part creation (binding together of powders) from energy supply (post-process sintering). However, it is challenging to fabricate parts of high density using this method due to low packing density of powder while printing. This work aims to investigate the effects of Hot Isostatic Pressing (HIP) as a secondary post-processing step on the densification of Binder Jet copper parts. By understanding the effects of HIP, the author attempts to create parts of near-full density, and subsequently to quantify the effects of the developed process chain on the material properties of resultant copper parts. The goal is to be able to print parts of desired properties suited to particular applications through control of the processing conditions, and hence the porosity. First, 99.47% dense copper was fabricated using optimized powder configurations and process parameters. Further, the HIP of parts sintered to three densities using different powder configurations was shown to result in an improvement in strength and ductility with porosity in spite of grain coarsening. The strength, ductility, thermal and electrical conductivity were then compared to various physical and empirical models in the literature to develop an understanding of the process-property-performance relationship. / Master of Science