CORRELATIONS BETWEEN OXIDE STRUCTURE, IRON DISTRIBUTIONS, AND ZIRCONIUM OXIDE GROWTH by Yan Dong A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Materials Science and Engineering) in the University of Michigan 2017 Doctoral Committee: Associate Professor Emmanuelle Marquis, Chair Professor Michael Atzmon Professor Katsuyo Thornton Professor Lumin Wang Acknowledgement The work in this dissertation would not have been possible without the help, support, and dedication of a number of people. First and foremost, I would like to express my most sincere gratitude and appreciation to my advisor Professor Emmanuelle Marquis for her guidance, support and help in every aspect of my study including experimental design, academic paper writing, presentation skills and future career development. She keeps me inspired by her positive perspectives, great passion for academic researches and hard-working attitude. I am also grateful to my dissertation committee members, Professor Lumin Wang, Professor Michael Atzmon, and Professor Katsuyo Thornton for all of their help during my PhD. Whether it’s been through a class I’ve taken with them, a joint collaboration we’ve had, or questions they’ve thought important for me to address, they have shaped my dissertation immensely and I would like to thank them for it. I would also like to thank our collaborator, Professor Arthur Motta at Pennsylvania State University. I have learned a great deal from the collaboration and I would like to thank him for the opportunity and his help along the way. I would especially like to thank each and every one of my lab mates for their tremendous help, and more importantly their friendships, during these past few years. I would like to specially thank Dr. Yimeng Chen, for being my first lab mentor, for getting me familiarized with atom ii probe, FIB, TEM, etc., and for driving me to Toledo in the first two semesters when I did not have a car. Whenever I have questions, I have always been able to rely on our post-doctoral researchers Dr. Mukesh Bachhav, Dr. Allen Hunter, Dr. Lan Yao and Dr. Vicente Araullo- Peters for their generous help and mentorship. I would also like to thank Reshma Mathew, Ellen Solomon, Kevin Fisher, Peng-Wei Chu, Adam McFarland, Craig Shaner, Elaina Anderson, Talia Barth, Kathleen Chou, and Li-Jen Yu, for always being there to help when I’ve needed them. Many thanks to the EMAL staff members Kai Sun, Haiping Sun, Ying Qi, for the instruments training and invaluable help. On a more personal note, I would like to thank my parents for their unconditional love and support. I would also like to thank Kenneth Cheng for everything he has done for me. I would not have been able to succeed if it had not been for his encouragement and dedication. Additionally, I would like to thank all the friends who have stayed with me during this long journey. I cherish all the fun and friendship with you. iii Table of Contents Acknowledgement ..........................................................................................................................ii List of Acronyms ..........................................................................................................................vii List of Tables .............................................................................................................................. viii List of Figures ............................................................................................................................... ix CHAPTER 1 Introduction ............................................................................................................ 1 1.1 Background .................................................................................................................. 1 1.2 Current Work ............................................................................................................... 1 1.3 Thesis Structure ........................................................................................................... 2 CHAPTER 2 Uniform Corrosion of Zirconium-based Alloys: Literature Review ................. 3 2.1 Introduction .................................................................................................................. 3 2.2 Physical Metallurgy ..................................................................................................... 6 2.2.1 Pure Zirconium ..................................................................................................... 6 2.2.2 Alloying Additions and Common Zirconium Alloys ........................................... 7 2.2.3 Material Processing and Resultant Microstructure ............................................... 9 2.2.4 Intermetallic Precipitates .................................................................................... 11 2.3 Microstructural Characterization of Oxidized Zirconium Alloys .............................. 12 2.3.1 Zirconium-Oxygen Phase Diagram .................................................................... 12 2.3.2 ZrO2 Oxide ......................................................................................................... 14 2.3.3 Suboxide at Metal-Oxide Interface .................................................................... 17 2.3.4 Oxide-Metal Interface Morphologies ................................................................. 19 2.3.5 Second Phase Particles in the Oxide .................................................................. 20 2.4 Oxidation Mechanisms and Kinetics ......................................................................... 21 2.4.1 Uniform Corrosion and Nodular Corrosion ....................................................... 21 2.4.2 Uniform Corrosion Kinetics ............................................................................... 22 2.4.3 Breakaway Mechanisms ..................................................................................... 25 2.5 Microstructural Factors Affecting Alloy Corrosion Resistance ................................ 26 2.5.1 Structures of Oxide Scale ................................................................................... 26 2.5.2 Second Phase Particles (SPPs) ........................................................................... 28 2.5.3 Alloying Additions ............................................................................................. 29 2.6 Summary .................................................................................................................... 31 iv CHAPTER 3 Alloys and Experimental Techniques ................................................................. 34 3.1 Materials .................................................................................................................... 34 3.1.1 Model Alloys ...................................................................................................... 34 3.1.2 Autoclave Corrosion Test ................................................................................... 36 3.2 Sample Preparation .................................................................................................... 38 3.2.1 Metallography ..................................................................................................... 38 3.2.2 TEM and APT Sample Preparation .................................................................... 38 3.3 Characterization Techniques ...................................................................................... 42 3.3.1 SEM and TEM .................................................................................................... 42 3.3.2 Atom Probe Tomography (APT) ........................................................................ 43 CHAPTER 4 Alloy Microchemistry .......................................................................................... 54 4.1 Overview .................................................................................................................... 54 4.2 Pure Zr ....................................................................................................................... 54 4.3 Zircaloy-4 ................................................................................................................... 56 4.4 Zr-Fe-Cr ..................................................................................................................... 58 CHAPTER 5 Structure and Morphology of Growing Oxide .................................................. 60 5.1 Overview .................................................................................................................... 60 5.2 Oxide Phase Sequence ............................................................................................... 61 5.2.1 Pure Zr ................................................................................................................ 62 5.2.2 Zircaloy-4 ........................................................................................................... 64 5.2.3 Zr-Fe-Cr .............................................................................................................. 65 5.2.4 Field Evaporation Behavior of the ZrO Layer ................................................... 66 5.2.5 Crystal Structure of Subxides ............................................................................. 68 5.3 Evolution of Oxide Morphology ................................................................................ 70 5.3.1 Early Stage of