含共格纳米析出相高熵合金的辐照缺陷演化及抗辐照机理研究

High entropy alloys are novel irradiation resistant structural materials, and have attracted significant attention. At present, the investigations of their irradiation behaviors have mainly focused on the single-phase solid solution alloys, however, these alloys experience severe void swelling under high fluence irradiation, and cannot meet the requirements by the Generation IV nuclear reactors. As an important type of defect trap with superior stability, coherent nanoprecipitates can absorb point defects produced by irradiation, which is key to further improving the irradiation resistance of high entropy alloys. However, the effects of coherent nanoprecipitates on the irradiation response of high entropy alloys remain unclear, and desire in-depth investigations. Therefore, this project will target on the high entropy alloys containing coherent nanoprecipitates, and characterize the irradiation-induced defect evolution under high temperature irradiation, in order to understand the impact of coherent nanointerface on the irradiation resistance of high entropy alloys. Moreover, this project will study the microstructure evolution of nanoprecipitates, in order to understand the effects of sluggish diffusion of high entropy alloys on the materials stability under high temperature irradiations. This project aims at unveiling the synergistic effects between defect trapping and transport property control, and eventually providing a new strategy of improving the irradiation resistance of high entropy alloys.

高熵合金作为新型抗辐照结构材料受到广泛关注。当前，高熵合金的辐照损伤研究主要集中在具有简单结构的单相固溶体高熵合金，但其在剂量超过100dpa的高温辐照下肿胀严重，仍不足以适应第四代反应堆的高温和高剂量辐照环境，而通过引入缺陷“陷阱”来降低辐照缺陷浓度是进一步提升其抗辐照性能的关键。共格纳米析出相是具有良好热稳定性的缺陷陷阱，但其对高熵合金抗辐照性能的影响尚不清楚，亟需深入研究。因此，本项目以含共格纳米析出相高熵合金为主要研究对象，通过观测其在高温离子辐照下的缺陷演化规律，探索纳米尺度共格界面对高熵合金抗辐照性能的影响机制。同时，通过研究共格纳米析出相在高温辐照下的长大及消解等演化过程，探索高熵合金的“迟滞扩散”这一输运性质特征对缺陷陷阱辐照稳定性的影响。项目成果将揭示陷阱吸收与输运性质调控这两种抗辐照机制间的协同作用，为进一步提升高熵合金抗辐照性能提供新的设计思路和参考依据。

先进反应堆研发对提升金属结构材料的抗辐照性能提出了强烈需求。高熵合金作为新型抗辐照材料受到广泛关注，但单相固溶体高熵合金的抗辐照性能仍需进一步提升。本项目提出在高熵合金中引入共格纳米析出相，利用其作为缺陷阱，进一步降低高熵合金的辐照损伤，同时依托高熵合金中的迟滞扩散效应，更好地发挥共格析出相的结构稳定性优势。. 本项目在典型的具有单相固溶体结构的模型高熵合金CoCrFeNi中，通过掺杂Ti、Al元素并调控热处理工艺，引入具有不同含量和尺寸的L12共格纳米析出相，并对其开展高温下的重离子(Fe)和He离子辐照实验，研究了共格纳米析出相对辐照后的缺陷演化和力学性能的影响规律，同时研究了高熵合金中共格纳米析出相在辐照下的稳定性。. 本项目通过对重离子辐照后的材料表征发现，引入共格纳米析出相后高熵合金中辐照位错环尺寸更小、退层错程度更低，体现出更慢的缺陷聚集和演化速率；同时，尽管引入析出相后的合金本身硬度更高，辐照后的硬化程度却比单相高熵合金更低，体现出更强的抗辐照硬化能力；除了抑制辐照损伤的能力外，高熵合金中的共格析出相在高温呢辐照下比在传统合金中具有更高的结构稳定性，体现出多主元效应与缺陷阱之间对抗辐照性能的协同作用。此外，通过对氦离子辐照后的微观结构进行表征，发现尽管辐照注入的氦并不在共格纳米析出相自身界面异质形核，但析出相可以通过改变辐照下基体中空位团簇浓度，调控不同缺陷阱间的竞争优势，使氦泡在层错环上异质形核，聚集长大，体现出一种 “旁观者”效应。. 本项目揭示了共格纳米析出相对高熵合金辐照损伤的影响，为进一步提升材料抗辐照性能提供了思路和实验依据。