No description available.

No description available.

Thesis (Ph. D.)--University of Florida, 1970. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--University of Florida, 1970. / Includes bibliographical references.

No description available.

No description available.

A thesis submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy in Engineering (Metallurgy and Materials Engineering). Johannesburg, March 2014 / This study investigated the C-Ni-V ternary phase diagram and identification of possible abrasive-resistance alloys. Twenty-four alloys were made from the elemental components and were arc-melted under an argon atmosphere, using Ti as an oxygen-getter. These alloys were analysed in both the as-cast condition, and after annealing for 1000oC and water quenching. Microstructural characterization was carried out in a SEM with EDX, and was done to confirm the phases. The results were used to plot a solidification projection and all binary phases extended into ternary, except for ~Ni8V, ~NiV3 and ~V2C which were not found, due to the sample compositions chosen. The extensions of the binary phases were: ~Ni3V: ~15 at.% C; ~Ni2V: ~20 at.% C; σ′: ~18 at.% C; (Ni): ~27 at.% C; ~V8C7: ~2 at.% Ni; ~V6C5: ~2 at.% Ni and ~VC: ~2 at.% Ni. The liquidus surface was derived, and three ternary invariant reactions were identified. The isothermal section at 1000oC was also constructed. Hardness of the alloys was studied in both conditions. Alloys with (Ni) (188-402HV5) were found to be ductile with low hardness. Alloys containing (V), ~Ni3V and ~Ni2V were identified as hard phases (533-1052 HV5). Alloys with σ′ phase were very hard (1065-1266 HV5) extremely brittle with cracks. Fracture toughness of the C-Ni-V alloys 0.9-5.2 (MPa.m-1/2) were comparable with ceramics 0.5-5.3(MPa.m-1/2). The wear behaviour of the alloys was characterized by sliding the carbide alloys against a Cr-steel ball in a pin-on-disc configuration. There were several co-existing wear mechanisms: abrasion, adhesion and the formation of a thin tribolayers. The wear coefficients for a 10N contact load after a sliding wear path of 300m varied between 0.1 x 10-6and 7.6 x 10-6(mm3/Nm), which was not as good as WC-Co hard metals, but close. / MT2017

Improving the performance of structural materials definitely leads to their better use for several applications, and consequently to a decrease in the use of natural resources or in the harmful environmental consequences. For example, reducing the weight of cars or planes while improving their structural performances will also bring about a decrease of their fuel consumption and of their level of emitted CO2. The key issue is thus to find and to fabricate better materials for these applications. Our research project deals with the influence of thermal, mechanical and thermomechanical parameters on the thermodynamics, kinetics, crystallography and mechanics of phase transformations occurring in different metallic alloys presenting finely grained multiphase microstructures in order to design new alloys or microstructures exhibiting mechanical properties never reached before. It encompasses the characterisation and the understanding of the relationships between the mechanisms dictating the elastic-plastic properties and the phase transformations and recrystallisation of different engineering metallic materials including steels, iron alloys and titanium alloys in order to improve their structural performances. We focus, on the one hand, on how the microstructure of engineering alloys can be designed and controlled through the combined actions of heat and deformation, and on the other hand, on the discovery and the understanding of how phenomena operating at different scales dictate the macroscopic mechanical behaviour. By controlling the defects structures generated at several levels ranging from 1nm to 100µm in the engineered microstructures, it is possible to attain large improvements of the mechanical properties instead of premature embrittlement.

No description available.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1970. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliography.