Microstructural Processes in Irradiated Materials: Fusion Materials and High-Temperature Alloys
Sponsored by: TMS Structural Materials Division, TMS: Nuclear Materials Committee
Program Organizers: Thak Sang Byun, Pacific Northwest National Laboratory; Chu-Chun Fu, Commissariat Ó l'Únergie atomique et aux Únergies alternatives (CEA); Djamel Kaoumi, University of South Carolina; Dane Morgan, University of Wisconsin-Madison; Mahmood Mamivand, University of Wisconsin-Madison; Yasuyoshi Nagai, Tohoku University

Wednesday 2:00 PM
March 1, 2017
Room: Del Mar
Location: Marriott Marquis Hotel

Session Chair: Gary Was, University of Michigan; Chad Parish, Oak Ridge National Laboratory

2:00 PM  Invited
IOM/Mehl Award Lecture: Microstructure of Irradiated Materials: Steven Zinkle1; 1University of Tennessee; Oak Ridge National Laboratory
    Energetic particle irradiation can induce pronounced microstructural changes and corresponding dramatic property changes in materials. This presentation will provide an overview of radiation-induced microstructural changes, with particular emphasis on similarities and differences between metals and ceramics. There are several key temperature regimes for all irradiated materials (defined by the onset temperatures for migration of interstitials and vacancies, thermal dissolution of in-cascade produced vacancy clusters, and thermal evaporation of cavities). In general, radiation tolerance in one temperature regime does not universally translate to radiation tolerance in other temperature regimes due to different controlling physical parameters. The fluence dependence of defect accumulation also is generally significantly different in the various temperature regimes. The roles of primary knock on atom energy, damage rate, atomic mass, crystal structure, and other material parameters will be briefly discussed.

2:50 PM  
Microstructural Processes in Neutron-irradiated Tungsten: Chad Parish1; Xunxiang Hu1; Lauren Garrison1; Philip Edmondson1; Kun Wang1; Lance Snead2; Yutai Katoh1; 1Oak Ridge National Laboratory; 2Massachusetts Institute of Technology
    We performed mixed spectrum neutron irradiation of single and polycrystalline tungsten over a wide range of irradiation conditions, to determine the microstructural processes that might occur during service as a fusion plasma-facing materials. Irradiation temperatures ranged from ~80░C to ~1000░C. Neutron doses were from a fraction of a dpa to ~5 dpa. Hardness increased and toughness decreased markedly, and many of the high-dpa samples fractured in handling before tensile testing. Positron annihilation indicated significant vacancy populations; isochronal annealing helped determine the vacancy mobility. Microscopy and atom probe found significant levels of the transmutation products Re and Os, which formed complex precipitate microstructures. Grain boundaries and voids gettered Re but not Os. In addition to mapping the microstructure of tungsten as a function of irradiation temperature and dose, this talk will discuss the effect of the microstructural features on the key issue of irradiation embrittlement in tungsten.

3:10 PM  
Evolution of Microstructure of Tungsten under Irradiation with Tungsten Ions: Emmanuel Autissier1; Marie-France Barthe1; Pierre Desagrdin1; CÚcile Genevois1; Brigitte Decamps1; Robin SchaŘblin2; Yves Serruys3; 1CNRS; 2ETH Zurich; 3CEA
    To study and understand the evolution of the microstructure of tungsten under conditions similar to those expected in future fusion reactors such as ITER and DEMO, irradiations with W ions were performed, in well prepared tungsten samples, using various conditions (energy, temperature and damage). Positron annihilation spectroscopy (PAS) and Tranmission Electron Microscopy (TEM) were used to characterize defects induced by irradiation, from the small vacancy clusters to large cavities. The defects distribution changes with damage dose between 0.01 and 0.06 dpa and irradiation temperature between -182 and 700 ░C. The effect of ion energy (1.2  20 MeV) on this distribution will be discussed. Acknowledgements: These studies are supported by the European Commission in the framework of the EUROfusion Consortium. Irradiations were performed at JANNuS (Joint Accelerators for Nanoscience and Nuclear Simulation) Orsay at CSNSM (France) and Saclay at CEA (France) which are part of the EMIR French accelerators network.