Nanocrystalline tungsten at high radiation exposure

PW Ma and DR Mason and S Van Boxel and SL Dudarev, PHYSICAL REVIEW MATERIALS, 8, 083601 (2024).

DOI: 10.1103/PhysRevMaterials.8.083601

Evolution of nanocrystalline (NC) tungsten under radiation exposure is investigated by atomic scale simulations in the low temperature high dose limit. Statistical analysis of samples containing at least a million atoms, with grain size varying from 5 nm to 20 nm, shows that the pattern of microstructural evolution of a NC material differs significantly from that of a single crystal. The high resistance to swelling in the low grain size limit stems from a combined effect of the initial excess volume of atomic configurations at grain boundaries and high integral volume of grain boundary defect-denuded zones. Grain boundaries annihilate defects through the rearrangement of their local atomic configurations acting as fluctuating dynamic sinks for defects. Grain size distribution slowly broadens as a function of dose, delaying the onset of an asymptotic radiation-driven steady state in comparison with a single crystalline material. Spatial limitations imposed by the size and topology of grains prevent the formation of a percolating dislocation network, resulting in only isolated dislocation loops being retained in the microstructure even at high radiation exposure.

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