Materials in Nuclear Energy Systems (MiNES) 2021: Fundamental Irradiation Damage- Session VI
Program Organizers: Todd Allen, University of Michigan; Clarissa Yablinsky, Los Alamos National Laboratory; Anne Campbell, Oak Ridge National Laboratory
Wednesday 1:30 PM
November 10, 2021
Room: Urban
Location: Omni William Penn Hotel
Session Chair: Zhijie Jiao, University of Michigan
1:30 PM Invited
Radiation Enhanced Diffusion (RED) and the Coupled Effects of Irradiation and Corrosion in Fe2O3: Kayla Yano1; Aaron Kohnert2; Amitava Banerjee2; Danny Edwards1; Edward Holby2; Tiffany Kaspar1; Hyosim Kim2; Sandra Taylor1; Yongqiang Wang2; Blas Uberuaga2; Daniel Schreiber1; 1Pacific Northwest National Laboratory; 2Los Alamos National Laboratory
The extreme environments present in a nuclear reactor do not occur in isolation – they are often coupled. In particular, the defects produced by irradiation have the potential of changing the rates and even mechanisms of corrosion. Here, we examine radiation-enhanced transport in a model oxide – Fe2O3 – and use that insight to develop a model of coupled irradiation and corrosion. Fe2O3 films with isotopic tracer layers are deposited, irradiated with ion beams, and characterized via atom probe tomography to determine the extent of RED. These results are compared to an atomistically-informed mesoscale model of transport to identify mechanisms responsible for RED. Once validated, the model is used to explore the potential impact of irradiation on the corrosive growth of Fe2O3 scales. We find that irradiation can increase growth rates by orders of magnitude and that the growth rate becomes non-monotonic with thickness, a consequence of different regimes of radiation damage evolution.
2:10 PM
Radiation-induced Segregation in Nanocrystalline FeCrNi under Concurrent Grain Boundary Movement: Aashique Rezwan1; Yongfeng Zhang1; 1University of Wisconsin Madison
Irradiation of crystalline materials modifies the microchemistry and microstructure, including solute segregation towards defect sinks such as grain boundaries (GBs), known as radiation-induced segregation (RIS). Unlike coarse-grained alloys, where GBs are nearly static, RIS in nanocrystalline is accompanied and affected by concurrent grain growth, either thermal or irradiation induced. This talk presents a phase-field study of concurrent RIS and grain growth in austenitic Fe-Cr-Ni. It is found that the overall RIS is grain size-dependent and increases with increasing grain size. The segregation profile is asymmetrical, with Cr depleted behind and enriched in front of a moving GB. This leads to a heterogenous Cr distribution, depleted in growing and enriched in shrinking grains. These findings highlight different effects of RIS in nanocrystalline alloys than those in their coarse-grained counterparts.
2:30 PM
Suppressing Irradiation Instabilities in Nanocrystalline Tungsten through Grain Boundary Doping: Jason Trelewicz1; W. Cunningham1; Khalid Hattar2; Yuanyuan Zhu3; Danny Edwards4; 1Stony Brook University; 2Sandia National Laboratories; 3University of Connecticut; 4Pacific Northwest National Laboratory
Targeted doping of grain boundaries stabilizes nanostructured materials against thermal coarsening, which provides a pathway to advanced alloys containing a high density of defect sinks. However, the impact of dopants on irradiation damage processes in interfaces represents a knowledge gap in radiation-resistant alloy design. In this study, we probe the coupling between microstructural evolution and irradiation damage in nanocrystalline W-20 at.% Ti using complementary in situ and ex situ ion irradiation experiments. Compared with a nanocrystalline W film, the W-Ti alloy is shown to exhibit smaller defect loops and a delayed saturation dose with a period of irradiation induced grain growth during the transient damage accumulation regime. Application of a thermal spike grain growth model reveals that the microstructure in the W-Ti alloy plateaus to a much finer grain size relative to predictions for pure W, indicating that doping for enhanced thermal stability also stabilizes the material against irradiation-induced instabilities.
2:50 PM
Correlating Properties of Irradiation Produced Nanoscale Superlattices with Irradiation Condition Parameters: Anton Schneider1; Yongfeng Zhang1; Jian Gan2; 1University of Wisconsin Madison; 2Idaho National Laboratory
Void superlattices have been known to form in materials under irradiation for decades. Although the exact mechanisms of such lattice ordering remain debated in the literature, recent theoretical and experimental studies have clarified the role of one-dimensional self-interstitial atoms diffusion in the superlattice formation process. Based on the framework developed in earlier modeling works, the present study aims at providing a deeper understanding of the dependance of several key superlattice properties on irradiation conditions, by combining theoretical analysis and Kinetic Monte-Carlo simulations. The results suggest that superlattice properties such as the lattice constant, ordering, and critical dose and temperature limit of formation are clearly correlated with irradiation condition parameters such as dose rate and temperature. The correlations elucidated by theory and simulations provide deeper insights regarding superlattice formation and constitute a valuable step towards the development of tailor-made meta-materials.
3:10 PM
Study on Role of Irradiation Induced Vacancies and Voids on Strain-induced Martensitic Transformations by Molecular Dynamics: Chao Yang1; Yash Pachaury1; Anter El-Azab1; Janelle Wharry1; 1Purdue University
Strain-induced martensitic transformations can improve the strength and ductility of face centered cubic metals and alloys. Defects such as vacancies, dislocation loops, and voids – often introduced by irradiation – activate martensitic transformations over a wider range of conditions than the pristine material. However, the mechanisms underlying irradiation-enabled martensite transformations remain unclear. In this work, molecular dynamics simulations study the effect of vacancies and voids on strain-induced transformations. Single vacancies have no resolvable effect on the transformation because they reduce the stacking fault energy by a relatively insignificant margin and do so only if the vacancy is located on the stacking fault plane. Voids, however, activate the martensite transformation through shear strain accumulation around the void due to dislocation pileup. The larger the void, the more pronounced this effect. Mechanisms identified here are consequential to the deformation behavior of porous, nanoporous, irradiated, and hydrogen- or helium-charged steels and FCC alloys.
3:30 PM Break