Microstructure and irradiation hardening of V-4Cr-4Ti alloys with different yttrium (Y) contents were studied by self-ion irradiation at 550 °C via TEM and nano-indentation test technology. The peak damage of the V-4Cr-4Ti-xY alloy (x = 0, 0.1, 0.5, and 1, wt.%) irradiated by 2.5 MeV self-ion (V²⁺) is 8 dpa. Dense dislocation loops were observed in all vanadium alloy samples after irradiation. With the increase of Y content, both average size and number density of dislocation loops using g = near the pole [001] decreased, while the irradiation hardness increment first decreased and then increased. In order to better reduce the irradiation hardening, it is considered that the addition of 0.1 wt.% Y in V-4Cr-4Ti alloy is reasonable.

V-4Cr-4Ti alloy is one of the candidate structural materials for future fusion reactors due to its desirable characteristics. In our previous research, MAX-phase-dispersion-strengthened vanadium alloy (V-4Cr-4Ti-1.5Y-0.3Ti₃SiC₂), prepared through mechanical alloying, showed excellent thermal stability and creep resistance and was expected to have good radiation resistance. This study investigates the effects of 2.5 MeV V²⁺ ion irradiation on V-4Cr-4Ti-1.5Y-0.3Ti₃SiC₂ and V-4Cr-4Ti alloys at 500 °C, with peak damage of 0.8, 3.5, and 6.1 dpa. Transmission electron microscopy and nanoindentation were used to examine the changes in microstructure and hardness before and after irradiation. The microscopic analysis reveals that dispersed nanoparticles maintained good stability under irradiation. Defect clusters grow with increasing irradiation doses in both materials. The nanoindentation results show that V-4Cr-4Ti-1.5Y-0.3Ti₃SiC₂ has higher initial hardness and lower irradiation hardening, indicating better resistance to radiation hardening than V-4Cr-4Ti. This research serves as a valuable reference for the assessment of the irradiation resistance of Ti₃SiC₂-dispersion-strengthened V-4Cr-4Ti alloy.

After being self-ion implanted at 400 °C and 550 °C, the microstructure and irradiation hardness of kilogram-scale V-4Cr-4Ti alloys were studied using a transmission electron microscope (TEM) and nano-indentation test technology. Irradiation was performed using self-ions (V²⁺) at 2.5 MeV with design influences of 1.15 × 10¹⁵ ions cm⁻², 4.59 × 10¹⁵ ions cm⁻², and 9.17 × 10¹⁵ ions cm⁻², so that the peak damages of V-4Cr-4Ti alloys are 1, 4, and 8 dpa, respectively. Compared with the 400 °C samples, the 550 °C samples exhibited a higher-density number of dislocation loops and increased hardness and reached saturation at lower irradiation doses. The irradiation temperature was mainly responsible for these differences, and the potential mechanism for its effect on the irradiation behavior was discussed.