Printed by Media-Tryck, Lund University 2015 MAIMAITIYILITUERDI Phase transformation and stability studies system the 2015 of Zr-H Phase transformation and stability studies of the Zr-H system TUERDI MAIMAITIYILI FACULTY OF ENGINEERING | LUND UNIVERSITY Phase transformation and stability studies of the Zr-H system Various hydride phases in the zirconium-hydrogen system have been prepared and studied both in situ and ex situ using high-energy synchrotron X-ray, neu- tron and conventional X-ray diffraction techniques. The crystal structure and stability of the present phases in the material as well as the phase transforma- tion order between phases were recorded, analyzed and presented. Lund University Division of Materials Engineering 235522 Department of Mechanical Engineering ISBN 978-91-7623-552-2 ISRN LUTFD2/TFMT--15/1015--SE(1-65) 789176 9 Phase transformation and stability studies of the Zr-H system Tuerdi Maimaitiyili DOCTORAL DISSERTATION by due permission of the Faculty of Engineering, Lund University, Sweden. To be defended at lecture hall M:E (M-Building, LTH), on 2015-12-03 at 10:15 AM Faculty opponent Lars Hallstadius Organization: Document name: Division of Materials Engineering DOCTORIAL DISSERTATION Department of Mechanical Engineering LUND UNIVERSITY P.O. Box 118 SE-221 00 Lund, Sweden Date of disputation: 2015-12-03 Author(s): Tuerdi Maimaitiyili Sponsoring organization: Swedish Research Council Title and subtitle: Phase transformation and stability studies of the Zr-H system Abstract: Zirconium alloys are widely used in the nuclear industry because of their high strength, good corrosion resistance and low neutron absorption cross-section. Zirconium has a strong affinity for hydrogen, however, and if hydrogen concentration builds up, the material will gradually degrade. In one class of such hydrogen caused degradation, called hydride induced embrittlement, hydrogen chemically reacts with zirconium forming one, or several, crystal phases of zirconium hydride. These hydrides play a primary, but sometime not fully understood, role in crack initiation and propagation within these materials. Despite the fact that hydride induced embrittlement in zirconium have been studied for several decades, there are still some unresolved issues. It has been the aim of the research presented in this thesis to provide the research community with new and updated data of the hydrides themselves in order to aid further studies within the field of hydride induced embrittlement in general, and the mechanism of delayed hydride cracking in particular. To that end, the research presented here proceeded, in short, as follows: First, zirconium hydride powder, of well defined hydrogen concentration, was produced from commercial grade zirconium. This powder was subjected to heat treatment and the hydride phases were characterized both in situ and ex situ using neutron, synchrotron X-ray, and conventional laboratory X-ray based diffraction techniques. Next, most of the low-pressure zirconium hydride phases were produced under hydrogen/argon atmosphere from commercial grade zirconium powder. This process was simultaneously monitored and recorded in real time using synchrotron X-ray diffraction. These experiments have produced new data of the behavior of different hydride phases during thermal treatment and in situ hydrogenation. For the first time all commonly reported zirconium hydride phases and the complete transformation between two different hydride phases were recorded with a single experimental arrangement. The phase transformation between δ and ε zirconium hydride was recorded in detail and presented. Finally, the controversial γ zirconium hydride was observed both in situ and ex situ and the preparation route, its crystal structure, and formation mechanisms were analyzed and presented. Key words: Zirconium hydride, phase transformation, synchrotron X-ray diffraction, neutron diffraction, hydrogen induced degradation, in situ hydrogen charging, hydrogenation Classification system and/or index terms (if any) Supplementary bibliographical information Language: English ISSN and key title ISBN: 978-91-7623-552-2 (print) 978-91-7623-553-9 (pdf) Recipient’s notes Number of Price pages: 161 Security classification I, the undersigned, being the copyright owner of the abstract of the above-mentioned dissertation, hereby grant to all reference sourcespermission to publish and disseminate the abstract of the above-mentioned dissertation. Signature Date 2015-10-28 Phase transformation and stability studies of the Zr-H system Tuerdi Maimaitiyili Cover: Complete phase transformation in zirconium during hydrogenation and dehydrogenation with different heating cycles (for details see Paper I). Copyright Tuerdi Maimaitiyili Division of Materials Engineering Department of Mechanical Engineering Lund University, Box 118, SE-221 00 Lund, Sweden ISRN LUTFD2/TFMT--15/1015--SE(1-65) ISBN 978-91-7623-552-2 (print) ISBN 978-91-7623-553-9 (pdf) Printed in Sweden by Media-Tryck, Lund University Lund 2015 Materials Science and Applied Mathematics Dept. Media Technology and Product Development Faculty of Technology and Society, Malm¨oUniversity SE 20506 Malm¨o,Sweden Homepage: http://www.mah.se/ To my dearest parents, and Zhayida and Lale and Malik. ix Abstract Zirconium alloys are widely used in the nuclear industry because of their high strength, good corrosion resistance and low neutron absorption cross-section. Zirconium has a strong affinity for hydrogen, however, and if hydrogen con- centration builds up, the material will gradually degrade. In one class of such hydrogen caused degradation, called hydride induced embrittlement, hydro- gen chemically reacts with zirconium forming one, or several, crystal phases of zirconium hydride. These hydrides play a primary, but sometime not fully understood, role in crack initiation and propagation within these materials. Despite the fact that hydride induced embrittlement in zirconium have been studied for several decades, there are still some unresolved issues. It has been the aim of the research presented in this thesis to provide the research community with new and updated data of the hydrides themselves in order to aid further studies within the field of hydride induced embrittlement in general, and the mechanism of delayed hydride cracking in particular. To that end, the research presented here proceeded, in short, as follows: First, zir- conium hydride powder, of well defined hydrogen concentration, was produced from commercial grade zirconium. This powder was subjected to heat treat- ment and the hydride phases were characterized both in situ and ex situ using neutron, synchrotron X-ray, and conventional laboratory X-ray based diffrac- tion techniques. Next, most of the low-pressure zirconium hydride phases were produced under hydrogen/argon atmosphere from commercial grade zirconium powder. This process was simultaneously monitored and recorded in real time using synchrotron X-ray diffraction. These experiments have produced new data of the behavior of different hy- dride phases during thermal treatment and in situ hydrogenation. For the first time all commonly reported zirconium hydride phases and the complete trans- formation between two different hydride phases were recorded with a single experimental arrangement. The phase transformation between δ and " zirco- nium hydride was recorded in detail and presented. Finally, the controversial γ zirconium hydride was observed both in situ and ex situ, and the prepara- tion route, its crystal structure, and formation mechanisms were analyzed and presented. xi Acknowledgment The work presented in this dissertation has been conducted at the Materials Science and Applied Mathematics group at Malm¨oUniversity. This work would not have been possible without the support of many people around me. Here I would like to take this opportunity to acknowledge the support of many who helped me out along the past couple years. There have been far too many to name everyone individually so I will be brief: I would like to thank my supervisor Dr. Christina Bjerk´en,for her valuable suggestions, encouragement and constant support during this research. I am also thankful for my supervisor Dr. Jakob Blomqvist for his patience and guid- ance. I am deeply grateful to Dr. Axel Steuwer for introducing this scientific field to our group and his generous help throughout the process. Dr. Olivier Zanellato spent a significant amount of his valuable time to teach me how to use the Topas Academic software package, and to share his insight into crystal- lography as well as data analysis with me. I am truly thankful for all his help. Dr. P¨arOlsson, Dr. Matthew Blackmuir and Dr. Martin Fisk showed great interest in my work and we had many rewarding discussions which, provided me with a better perspective on my results. I would also like to acknowledge Dr. John Christopher Ion and Waleed Shoaib for proof reading my papers and thesis. Additionally, my special thanks go to all of the helpful and encouraging co-workers at the Faculty of Technology and Society at Malm¨oUniversity who have helped directly or indirectly when I was in need of advice or support. The Swedish Research Council (Grant no. VR 2008-3844) and Malm¨oUni- versity are gratefully acknowledged for providing financial support for this project. The European Synchrotron Radiation Facility (ESRF), Grenoble, France, the Forschungsneutronenquelle Heinz Maier-Leibnitz (FRM II), Garching, Ger- many, and the Australian Nuclear Science and Technology