High entropy alloys (HEAs) have been considered as one of the potential structural material candidates for fourth-generation nuclear reactors and fusion reactors due to their excellent irradiation resistance. Current studies have shown that the chemical short-range order (CSRO) usually exists in HEAs, which has a significant effect on the mechanical properties and irradiation resistance of HEAs. Refractory high entropy alloys (RHEAs), as a new class of HEAs have better mechanical properties at high temperatures than face-centered cubic (FCC) HEAs, and therefore have better prospects of application in the nuclear field. In this study, CSRO and its effect on the irradiation resistance of HfNbTaTiZr are analyzed via molecular dynamics (MD) and Monte Carlo (MC). The primary cascade simulations, multi-cascade simulations and surface bombardment simulations are carried out to simulate the generation and accumulation of irradiation damage. The results of the primary cascade simulations and surface bombardment simulations of CSRO models show that the presence of CSRO induces cascade splitting into subcascades. The presence of subcascades reduces the thermal peak enhancement effect and thus lowers the recombination rate of Frenkel pairs (FPs) in the damage zone when FPs concentrations are low. However, the creation of subcascades increases the size of the damage zone caused by the cascade. Thus, when the concentrations of FPs are high, the larger area of damage zone allows more of the already existing FPs to be included, thus promoting their recombination, i.e., impedes their accumulation when concentrations are high. These subcascades lower the recombination of FPs at low FPs concentrations but inhibit their accumulation at high FPs concentrations. The presence of CSRO is also beneficial in inhibiting the growth of point defect clusters, which further improves the resistance of HfNbTaTiZr to dislocation generation. Furthermore, the presence of CSRO facilitates the irradiation-induced phase transition. But it is found that HfNbTaTiZr shows suppression of hexagonal close-packed (HCP) cluster growth. And the tendency to break down large HCP clusters into smaller ones is demonstrated in the CSRO model. From our calculations we also find that the irradiation-induced HCP atoms have a higher potential energy relative to the matrix. The potential energy difference between those energetic HCP atoms and the matrix can lead to generating a great number of insurmountable barriers pervading the matrix and largely suppressing the long-term mobility of FPs, thus limiting their aggregation and growth into clusters.

中文翻译：

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HfNbTaTiZr 高熵合金抗辐照性能的化学短程有序原子模拟


高熵合金 （HEAs） 因其优异的抗辐照性而被认为是第四代核反应堆和聚变反应堆的潜在结构材料候选者之一。目前的研究表明，化学短程序 （CSRO） 通常存在于高熵合金中，这对高熵合金的力学性能和抗辐照性有显著影响。难熔高熵合金 （RHEAs） 作为一类新型高熵合金，在高温下比面心立方 （FCC） 高熵合金具有更好的力学性能，因此在核领域具有更好的应用前景。在本研究中，通过分子动力学 （MD） 和蒙特卡洛 （MC） 分析了 CSRO 及其对 HfNbTaTiZr 抗辐照性的影响。进行了初级级联模拟、多级联模拟和表面轰击模拟，以模拟辐照损伤的产生和积累。CSRO 模型的初级级联模拟和表面轰击模拟结果表明，CSRO 的存在会诱导级联分裂为子级联。当 FPs 浓度较低时，子级联的存在降低了热峰增强效应，从而降低了损伤区 Frenkel 对 （FPs） 的复合速率。但是，子级联的创建会增加级联引起的损害区域的大小。因此，当 FPs 浓度较高时，较大的损伤区面积允许包含更多已经存在的 FPs，从而促进它们的重组，即在浓度高时阻碍它们的积累。这些子级联反应在低 FPs 浓度下降低了 FPs 的重组，但在高 FPs 浓度下抑制了它们的积累。 CSRO 的存在也有利于抑制点缺陷簇的生长，从而进一步提高 HfNbTaTiZr 对位错产生的抵抗力。此外，CSRO 的存在促进了辐照诱导的相变。但发现 HfNbTaTiZr 显示出对六边形紧密堆积 （HCP） 簇生长的抑制。CSRO 模型展示了将大型 HCP 集群分解为较小集群的趋势。从我们的计算中，我们还发现辐照诱导的 HCP 原子相对于基体具有更高的势能。这些高能 HCP 原子与基质之间的势能差会导致在基质中产生大量不可逾越的障碍，并在很大程度上抑制 FP 的长期迁移率，从而限制它们聚集和生长成簇。