Microstructural Evaluation and Thermal Creep Behavior of Zr-Excel
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Authors
Ahmmed, Kazi Foyez
Date
2015-12-01
Type
thesis
Language
eng
Keyword
Zr-Excel pressure tube , heat-treatment , texture , anisotropy , line-broadening , dislocations , thermal creep , creep anisotropy
Alternative Title
Abstract
Dual phase (α-β) Zr-Excel Pressure Tube (PT) material has been heat treated in the (α+β) or β-phase regime to generate variable microstructures. These heat-treated microstructures revealed significant modification in the inital microstructure. The microstructural changes by heat-treatment will have a profound influence on their deformation behavior; characterizing those properties is the main goal of this study. In this dissertation, the experimental results are presented in a manuscript format, which is divided in three technical chapters. Chapter 3 discusses the effect of heat treatment on texture modification; where, as received (ASR) PT materials were heated to a range of temperatures and cooled either in water or in air. It has been observed that due to the orientation relationship between α and β-phase, the ASR microstructure has been significantly altered during heating and cooling. The extent of this alteration strongly depends on the solution temperature and cooling rate. Although, variant selection is observed during texture modification, significant randomization is noticed in the room temperature texture. In Chapter 4, line profile analysis technique has been used to quantitatively analyze the microstructural details of the heat-treated materials. Diffraction pattern analyses demonstrated significant peak broadening in the heat-treated material; which is attributed due to the increase of volume fraction of martensitic α and alteration in the dislocation structures. Line profile analyses also revealed that primary α consists with large sub-grains and correlated dislocations but the martensitic α are highly dislocated. Finally in Chapter 5, thermal creep behavior of the heat treated materials has been studied. Microstructural analyses were also conducted in the pre- and post-creep materials to understand the creep mechanism. Creep anisotropy of the heat treated materials has been investigated by correlating the experimental creep data with their associated texture. The ASR PT material shows very anisotropic creep behavior due to the strong texture. However, the water-quenched-895 treatment substantially decreased the anisotropy by creating a balance between the texture and microstructure. Nevertheless, texture randomization at higher solution temperatures might have changed this balance and made the material being anisotropic again.
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Thesis (Ph.D, Mechanical and Materials Engineering) -- Queen's University, 2015-11-26 16:15:21.68
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ProQuest PhD and Master's Theses International Dissemination Agreement
Intellectual Property Guidelines at Queen's University
Copying and Preserving Your Thesis
Creative Commons - Attribution - CC BY
This publication is made available by the authority of the copyright owner solely for the purpose of private study and research and may not be copied or reproduced except as permitted by the copyright laws without written authority from the copyright owner.