Crystallographic Texture and Creep Anisotropy in Cold Worked and Recrystallized Zirlo

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dc.contributor.advisor Ron O.Scattergood, Committee Member en_US
dc.contributor.advisor Mohamed A. Bourham, Committee Member en_US
dc.contributor.advisor Man-Sung Yim, Committee Member en_US
dc.contributor.advisor K. Linga Murty, Committee Chair en_US Yan, Jinyuan en_US 2010-04-02T19:11:05Z 2010-04-02T19:11:05Z 2005-08-09 en_US
dc.identifier.other etd-04132005-130645 en_US
dc.description.abstract Zirlo, a special zircaloy material alloyed with niobium, tin and iron is a successor of Zircaloy-4. Zirlo is materials used in fuel rod cladding, structural and flow mixing grids, instrumentation tubes, and guide thimbles. It increases margin to fuel rod corrosion limits and enhance fuel assembly structural stability in Pressurized Water Reactor. Zirconium and its alloys, being hexagonally close packed, have limited number of slip systems, and exhibit preferred orientations following thermo-mechanical treatments, which result in anisotropic mechanical properties. The objective of this project is to investigate the anisotropic mechanical properties, crystallographic texture, and microstructure of crept zirlo materials. The anisotropic mechanical properties were investigated using uniaxial and biaxial creep tests. The specimen was loaded axially by a dead weight pan, and the hoop stresses was achieved by internally pressurizing the specimen with inert argon. Different axial and hoop stress, which produced different stress ratios (0, 0.67,0.75, 1, and 2) are selected for creep tests at 450°C. The axial displacement was measured by a linear variable differential transducer and the diameter change by a laser extensometer. Creep data are used to determine strain rate ratios vs stress ratios, the anisotropic parameters ( R and P), and creep loci for cold-worked and recrystallized zirlo. The crystallographic textures were characterized in terms of inverse and direct pole figures using X-ray diffraction techniques. Inverse pole figures were constructed for specimens in the rolling direction, transverse direction, and normal direction for both cold worked and recrystallized tubes. Direct pole figures were constructed for specific reflection planes, such as basal (0002), prismatic (10 0) and pyramidal (10 2). Crystallite orientation distribution function (CODF) was derived from the pole figure data. Euler plots were obtained from crystallite orientation distribution coefficients (wlmn ) and subsequently therefore, ideal orientations were calculated. These CODFs were combined with the Lower-Bound model to predict creep anisotropy assuming the dominance of prismatic, basal and pyramidal slip systems. Creep strain rate ratios vs stress ratios, creep loci and anisotropy parameters (R and P) were predicted. The predictions based on the prismatic dominance matche with the experimental data very well. Microstructure of the crept specimens was characterized by Transmission Electron Microscopy for different stress ratios ( 0, 0.75 and 1). The results show mainly dislocations in the matrix with no subgrain formation. The samples tested under equibiaxial loading revealed deformation twins. More detailed work is called for in characterizing the influence of stress-states and stress levels as well as cold work on deformation microstructures. en_US
dc.rights I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to NC State University or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. en_US
dc.subject Texture en_US
dc.subject Anisotropy en_US
dc.subject Inverse pole figure en_US
dc.subject Direct pole figure en_US
dc.subject CODF en_US
dc.subject Low-bound en_US
dc.subject Zirlo en_US
dc.subject Creep en_US
dc.subject en_US
dc.title Crystallographic Texture and Creep Anisotropy in Cold Worked and Recrystallized Zirlo en_US PhD en_US dissertation en_US Nuclear Engineering en_US

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