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

Monday 8:30 AM
February 27, 2017
Room: Del Mar
Location: Marriott Marquis Hotel

Session Chair: Philip Edmondson, Oak Ridge National Laboratory; Philippe Pareige, Rouen University

8:30 AM Introductory Comments

8:35 AM  Invited
Atom Probe Characterization of Microstructures in Irradiated Materials: Philippe Pareige1; Bertrand Radiguet1; Auriane Etienne1; Cristelle Pareige1; 1Rouen University
    Atom Probe Tomography (APT) allows to explore matter at the atomic scale to understand microstructural evolution of nuclear reactor pressure vessel steels or internals under neutrons (or other particles) irradiation. Specific sample preparations and correlative microscopies (APT and TEM)give new possibilities and bring additional informations to understand irradiation effects but also to support modeling. This state of art combination of techniques is available at the GPM laboratory in the GENESIS platform. However, APT data mining requires careful attention to give a correct description of the material at this ultimate atomic scale.In this presentation recent results and benchmarking on irradiated materials will be presented.

9:05 AM  
On the Influence of the Irradiation Depth on the Microstructural Evolution of FeCrX (X=Ni,Si,P) Alloys under Ion Irradiation: Begońa Gómez-Ferrer1; Cristelle Pareige1; Philippe Pareige1; 1University of Rouen
     The in-service behavior of high-Cr Ferritic-Martensitic steels –candidate structural alloys in future GEN IV and fusion reactors—is a key issue that requires a deep understanding of the microstructural changes operating under neutron-irradiation. Nevertheless, given the complexity of these processes and the restricted access to neutron-irradiations, the community focuses on model experiments performed on Fe-Cr alloys using ion-irradiations as alternative. However, transferability issues arise. In neutron irradiated Fe-Cr alloys (>9%) at 300°C α/α' decomposition was observed at low dose but not under ion-irradiation. Also, in low purity Fe-Cr model alloys, formation of NiSiPCr-enriched clusters formed under both ion and neutron irradiations was revealed with Atom Probe Tomography (APT). Within the framework of the European FP7/MatISSE project, FeCrX (X=Ni,Si,P) model alloys have been self-ion irradiated at 5 MeV and 300°C at two different fluences. APT characterization along the implantation profile provides insights on the origin of the differences and commonalities described.

9:25 AM  
Prismatic Dislocation Loop Interaction with Free Surface in BCC Metals: Jan Fikar1; Roman Gröger1; Robin Schäublin2; 1IPM; 2ETHZ
    The prismatic loops appear in metals as a result of high-energy irradiation. Understanding their formation and interaction is important for quantification of irradiation-induced deterioration of mechanical properties. Characterization of dislocation loops in thin foils is commonly done using transmission electron microscopy (TEM), but the results are inevitably influenced by the proximity of free surfaces. The prismatic loops are attracted to free surfaces by image forces. Depending on the type, size and depth of the loop in the foil, they can escape to the free surface, thus invalidating TEM observations and conclusions. We present an easy applicable and general method to estimate the critical depth for various dislocation loops in the thin foil and to correct the TEM measurements. The method is verified by atomistic simulations in BCC iron and tungsten on dislocation loops with Burgers vector 1/2<111> and <100> and with various shapes.