中文摘要：

钒合金（V-Cr-Ti系列）是重要的聚变堆结构候选材料，但是相比于铁素体／马氏体钢等其他候选材料，有关钒合金（V-Cr-Ti）的辐照损伤研究较为缺乏。利用载能离子束模拟聚变堆中子辐照条件，对V-4Cr-4Ti和V-5Cr-5Ti两种样品进行了载能He离子和重离子辐照实验。实验采用离子束梯度减能方法在样品中产生辐照损伤的坪区，利用纳米压痕技术测试材料的辐照硬化效应。结果表明，样品纳米硬度的深度递减现象可以用Nix-Gao模型很好描述，高能重离子辐照的样品中软基体效应可以有效避免；在He离子辐照情形，He浓度（以原子百万分率计（Atomic parts per million，APPM））／位移损伤（以每原子平均离位数计（Displacement per atom，DPAl）大于4200／0．2时，两种钒合金样品出现硬化饱和现象；相近位移损伤水平下，He与空位的结合导致缺陷集团的加速长大，致使材料的辐照硬化远大于重离子辐照情形。

英文摘要：

Background： Vanadium alloy （V-Cr-Ti） is an important fusion reactor candidate material due to its low activation characteristics, desirable high-temperature strength and good resistance to radiation damage. However, studies at lower temperature have shown a substantially reduced radiation resistance, manifested in a loss of ductility and enhanced hardening. Purpose： This work aims to investigate the irradiation hardening behavior of vanadium alloys under He-ion implantation and displacement damage, and provide an experimental evidence for optimizing the radiation resistance of vanadium alloys. Methods： In this study, irradiation of V-4Cr-4Ti alloy and V-5Cr-5Ti alloy samples were carried out with He-ions and swift-heavy-ions. A thick layer with a uniform damage distribution in samples was produced by varying energy of He ions, or by using an energy degrade wheel for swift-heavy-ion irradiation. The nanoindentation technique was used to measure the irradiation hardening. Cross-sectional transmission electron microscopy （TEM） sample fabricated from the irradiated samples were investigated with TEM. Results： The results show that the hardening saturation occurs when the dose of He-ion implantation is more than 4 200 （Atomic parts per million, APPM）/0.2 （Displacement per atom, DPA）. The irradiation hardening by He-ions is far larger than that by the swift-heavy-ions at the same displacement damage level. Conclusion： The phenomenon of the enhanced hardening by He-ions can be attributed to the accelerated formation of defect clusters due to the combination of He-atoms and vacancies.