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arXiv 1702.03019cond-mat.mtrl-sci
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辐照W-Re合金中Re析出机制的动力学蒙特卡罗模拟

Mechanism of Re precipitation in irradiated W-Re alloys from kinetic Monte Carlo simulations

Chen-Hsi Huang, Leili Gharaee, Yue Zhao, Paul Erhart, Jaime Marian

摘要:

高温,高剂量,中子照射W的结果在形成的稀土丰富的集群在浓度低于一个数量级的热力学溶解度极限。这些团簇可能最终转化为脆性的W-Re金属间相,这可能导致高水平的硬化和热导率损失。辐射增强扩散和沉淀的标准理论不能解释这些沉淀物的形成,因此了解非平衡簇在辐射下形成的机制对于预测材料降解和制定缓解策略至关重要。在这里,我们进行了W-Re合金的热力学研究和进行动力学蒙特卡罗模拟的Re团簇形成在辐照的W-2 Re合金使用的晶体中含有点缺陷的广义哈密顿参数完全与电子结构计算。我们的模型结合了最近获得的混合间隙溶质输运的机制信息,这被认为是控制形成准球形核后,在1800 K的平均孵育时间为20 s的簇成核和生长。这些核被认为是通过吸引更多的混合溶质原子,这反过来又吸引空位,导致重组和溶质团聚增长。团簇生长到大约4纳米半径的最大尺寸,并且不完全致密的Re,在中心附近含有50%或更少。我们的模拟与最近的原子探针检查离子辐照的W-2 Re系统在773 K的合理协议。

英文摘要:

High-temperature, high-dose, neutron irradiation of W results in the formation of Re-rich clusters at concentrations one order of magnitude lower than the thermodynamic solubility limit. These clusters may eventually transform into brittle W-Re intermetallic phases, which can lead to high levels of hardening and thermal conductivity losses. Standard theories of radiation enhanced diffusion and precipitation cannot explain the formation of these precipitates and so understanding the mechanism by which nonequilibrium clusters form under irradiation is crucial to predict materials degradation and devise mitigation strategies. Here we carry out a thermodynamic study of W-Re alloys and conduct kinetic Monte Carlo simulations of Re cluster formation in irradiated W-2Re alloys using a generalized Hamiltonian for crystals containing point defects parameterized entirely with electronic structure calculations. Our model incorporates recently-gained mechanistic information of mixed-interstitial solute transport, which is seen to control cluster nucleation and growth by forming quasi-spherical nuclei after an average incubation time of 20 s at 1800 K. These nuclei are seen to grow by attracting more mixed interstitials bringing solute atoms, which in turns attracts vacancies leading to recombination and solute agglomeration. The clusters grow to a maximum size of approximately 4-nm radius, and are not fully dense with Re, containing 50% or less near the center. Our simulations are in reasonable agreement with recent atom probe examinations of ion irradiated W-2Re systems at 773 K.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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