晶粒尺寸对材料辐照损伤影响的团簇动力学模拟

发布时间：2018-01-05 17:35

本文关键词：晶粒尺寸对材料辐照损伤影响的团簇动力学模拟　出处：《安徽大学》2017年硕士论文　论文类型：学位论文

【摘要】：寻找设计出长时间服役的面向等离子体材料是保证热核聚变安全运行的关键,而研究材料在辐照场下的损伤行为和抗辐照机制可为实验的开展提供理论支持。目前人们主要关注H/He粒子和中子辐照下材料损伤的行为。纳米晶材料由于具有较高的晶界密度,材料纳米化被认为是提高材料抗辐照能力的一种手段。本文基于多尺度框架的团簇动力学方法,并尝试考虑晶界和位错俘获效应,系统地研究了钨中晶粒尺寸与H/He粒子滞留之间的关系,以及扩散偏压对材料铁和钨辐照容忍度的影响。主要内容如下:(1)氚(T)在等离子体材料钨中的滞留行为的研究非常重要。目前关于晶粒尺寸对H/He粒子滞留行为的研究还不够系统而且还存在争议。针对此现象,通过在团簇动力学模型中引入晶界的效应,本文系统地研究了钨中H/He粒子滞留行为随晶粒尺寸变化的关系,发现H/He滞留量随晶粒尺寸的减小而显著增加,主要由于晶界俘获量增加导致。我们的研究进一步发现,在低能低剂量辐照条件下,He的滞留量主要是由晶界和位错俘获的贡献,随着晶粒尺寸的增加,由晶界主导的粒子滞留向位错发生转变。我们的结果指出使用多晶钨作为等离子体材料更为合适。此研究有助于定量理解等离子体钨材料不同晶粒尺寸下体内粒子滞留的机制。(2)我们结合多种方法研究影响材料抗辐照能力的因素,包括稳态下的化学速率理论状态方程,非平衡态下的团簇动力学和分子动力学方法,系统地模拟了不同晶粒尺寸下铁和钨的抗辐照能力。我们发现,在稳态下,材料的抗辐照能力只与自身空位的扩散速率有关而与扩散偏压无关。在非平衡态下,基于团簇动力学结合晶界效应的长时间演化的动力学模型,我们系统地研究了在中子辐照下不同晶粒尺寸的铁和钨体内总空位的滞留行为。结果证实了我们的预期:对于纳米晶铁,在温度为500 K时,纳米晶的抗辐照能力就体现出来了。然而对于纳米晶钨,当温度升高到900 K,纳米晶的抗辐照能力尤其对体内空位的湮灭没有体现出来。因此在稳态达到之前,研究以扩散偏压为主要因素影响纳米晶材料的抗辐照能力至关重要。分子动力学的模拟结果也证实了上述研究。我们建议选择多晶钨作为等离子体材料更为合适。而对于结构材料铁,由于具有较好的抗中子辐照能力,则选择纳米晶材料更为合适。研究结果为理解纳米晶材料在辐照下的行为提供了帮助。
[Abstract]:For a long time the design of plasma facing material service is the key to ensure the safe operation of thermonuclear fusion, which can provide theoretical support for the experiment and Research on material damage behavior of the radiation field and anti radiation mechanism. The damage of materials people mainly focus on H/He particle and neutron irradiation behavior of nanocrystalline materials. Due to the grain boundary density is the nanometer material is considered as a means to improve the ability of anti radiation materials. The cluster dynamics method based on multiscale framework, and try to consider boundaries and dislocation trapping, systematically studies the relationship between tungsten grain size and H/He particle retention, and the effect of diffusion bias on iron and tungsten materials radiation tolerance. The main contents are as follows: (1) tritium (T) is very important for the study on plasma materials in tungsten retention behavior. The grain size of H /He particles Study on the retention behavior of sub system is not enough but also controversial. In view of this phenomenon, the effects of introducing grain boundaries in cluster dynamics model, this paper systematically studies the relationship between H/He particles in tungsten retention behavior with the change of grain size, found that the decrease of H/He retention with the grain size increased, mainly due to the grain boundary trapping increase the amount of lead. Our study further found that in the low energy low doses of radiation, the retention of He is mainly composed of grain boundaries and dislocation trapping contribution, with the increase of the grain size, the grain boundary dominated particle retention transition to dislocation. Our results indicate that the use of polycrystalline tungsten as plasma material is more appropriate. This study contributes to the quantitative understanding of mechanism of plasma tungsten materials with different grain sizes in the body of the particle residence. (2) the ability of anti radiation materials we combine methods to study the influence of The factors, including the chemical rate theory equation of state under steady-state conditions, kinetics and molecular cluster dynamics method of non equilibrium system, simulation of the different grain sizes of iron and tungsten radiation resistance. We found that in the steady state, the anti radiation ability of materials and self diffusion rate of vacancies on has nothing to do with the diffusion bias. Under non-equilibrium state, long time evolution dynamics model of grain boundary effect based on the combination of cluster dynamics, we systematically studied under neutron irradiation with different grain sizes of iron and tungsten in total vacancy retention behavior. The results confirm our expectations for nanocrystalline iron in temperature 500 K, nanocrystalline radiation resistance is manifested. However for Nanocrystalline Tungsten, when the temperature rises to 900 K, nanocrystalline anti irradiation ability especially in the annihilation of vacancies is not reflected in. In order to reach steady state before the study of diffusion bias are main factors affecting the anti radiation ability of nanocrystalline materials is essential. Molecular dynamics simulations also confirm the above research. We suggest that the selection of polycrystalline tungsten as plasma material is more suitable for structural materials. Iron, due to neutron irradiation resistance the ability to select nanocrystals the material is more suitable. The research results provide help for understanding the behavior of nanocrystalline materials under irradiation.

【学位授予单位】：安徽大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O469

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