Absorption bias: A descriptor for radiation tolerance of polycrystalline BCC metals

To evaluate the radiation tolerance of polycrystalline materials, the damage effects of Fe and W as typical body-centered cubic metals under uniform irradiation are studied by multi-scale models. A guiding descriptor, the absorption bias (the ratio of the absorption abilities of grain boundaries (GBs) to interstitials (I) and vacancies (V)), is proposed to reflect the radiation tolerance of metals with different grain sizes. Low absorption bias promotes defects annihilation through enhancing I-V recombination and optimally tuning its competition with GB absorption. Polycrystalline metals possess high radiation resistant performance with low absorption bias regulated by grain size and temperature. Furthermore, by comprehensively considering the mechanical property, thermal stability, and radiation tolerance described by absorption bias, nano-crystals are recommended for Fe-based structural materials but coarse-grained crystals for W-based plasma-facing materials. This work reevaluates the radiation tolerance of polycrystalline metals, resulting in new strategies for designing structural materials in nuclear devices through manipulating grain sizes.