Vetterick Gregory A, Gruber Jacob, Suri Pranav K, Baldwin Jon K, Kirk Marquis A, Baldo Pete, Wang Yong Q, Misra Amit, Tucker Garritt J, Taheri Mitra L
Department of Materials Science and Engineering, Drexel University, Philadelphia, PA, 19104, USA.
TerraPower, LLC, Bellevue, WA, 98005, USA.
Sci Rep. 2017 Sep 25;7(1):12275. doi: 10.1038/s41598-017-12407-2.
Many methods used to produce nanocrystalline (NC) materials leave behind non-equilibrium grain boundaries (GBs) containing excess free volume and higher energy than their equilibrium counterparts with identical 5 degrees of freedom. Since non-equilibrium GBs have increased amounts of both strain and free volume, these boundaries may act as more efficient sinks for the excess interstitials and vacancies produced in a material under irradiation as compared to equilibrium GBs. The relative sink strengths of equilibrium and non-equilibrium GBs were explored by comparing the behavior of annealed (equilibrium) and as-deposited (non-equilibrium) NC iron films on irradiation. These results were coupled with atomistic simulations to better reveal the underlying processes occurring on timescales too short to capture using in situ TEM. After irradiation, NC iron with non-equilibrium GBs contains both a smaller number density of defect clusters and a smaller average defect cluster size. Simulations showed that excess free volume contribute to a decreased survival rate of point defects in cascades occurring adjacent to the GB and that these boundaries undergo less dramatic changes in structure upon irradiation. These results suggest that non-equilibrium GBs act as more efficient sinks for defects and could be utilized to create more radiation tolerant materials in future.
许多用于制备纳米晶（NC）材料的方法会留下非平衡晶界（GBs），这些晶界含有比具有相同5个自由度的平衡晶界更多的自由体积和更高的能量。由于非平衡晶界的应变和自由体积都增加了，与平衡晶界相比，这些晶界在材料受辐照时可能成为多余间隙原子和空位更有效的阱。通过比较退火（平衡）和沉积态（非平衡）的NC铁膜在辐照下的行为，研究了平衡晶界和非平衡晶界的相对阱强度。这些结果与原子模拟相结合，以更好地揭示在时间尺度太短而无法用原位透射电子显微镜捕捉的潜在过程。辐照后，具有非平衡晶界的NC铁中缺陷团簇的数密度和平均缺陷团簇尺寸都较小。模拟表明，过量的自由体积导致在晶界附近发生的级联中点缺陷的存活率降低，并且这些晶界在辐照时结构变化较小。这些结果表明，非平衡晶界是更有效的缺陷阱，未来可用于制造更耐辐射的材料。
