铁和钨中晶界对材料辐照损伤影响的理论模拟

Theoretical study of effects of grain boundaries on the radiation damage in iron and tungsten

利用稳态下的化学速率理论并结合晶界效应,对纳米晶材料的抗辐照能力进行研究,发现纳米晶材料的抗辐照能力只与体内空位自身的扩散速率有关,而与吸收偏压(指空位扩散速率与间隙原子扩散速率之比)无关.纳米晶铁和钨都表现出相比多晶优良的性能.采用分子动力学模拟晶界对铁和钨体内间隙原子和空位的吸收能力,研究纳米晶材料在非平衡态下的辐照损伤行为.结果表明,铁中晶界对空位具有很好的俘获能力.对于面向等离子体材料钨,体内中的空位滞留较大,主要是受到了吸收偏压的影响.在未来聚变装置中典型的服役环境下,到达稳态之前,吸收偏压的大小对纳米晶材料的抗辐照能力起决定作用.

This study is based on the chemical rate theory at steady state and the grain boundary sink effect. We find that the anti-irradiation ability of nano-crystalline materials is mainly determined by the vacancy diffusivity but barely by the absorption bias（ the ratio of vacancy diffusivity to interstitial diffusivity）. The anti-irradiation abilities of nano-crystalline iron and nano-crystalline tungsten are better than those of poly-crystalline. The behavior of radiation damage in nano-crystalline materials under non-equilibrium state is investigated by simulating the absorption capacity of grain boundaries on interstitials and vacancies by the molecular dynamics method. It is shown that the grain boundary has a good trapping ability for vacancies in iron. While for tungsten as a plasma facing material,more vacancies are retained in the bulk,mainly due to the effect of absorption bias. Under the typical service environment of fusion devices in the future,the level of absorption bias dominates the anti-irradiation ability of nano-crystalline materials before the steady state is reached.