High-entropy alloys (HEAs) have prospects for use as nuclear structural materials. Helium irradiation can form bubbles deteriorating the structure of structural materials. The structure and composition of NiCoFeCr and NiCoFeCrMn HEAs formed by arc melting and irradiated with low-energy 40 keV He²⁺ ions and a fluence of 2 × 10¹⁷ cm⁻² have been studied. Helium irradiation of two HEAs does not change the elemental and phase composition, and does not erode the surface. Irradiation of NiCoFeCr and NiCoFeCrMn with a fluence of 5 × 10¹⁶ cm⁻² forms compressive stresses (−90 … −160 MPa) and the stresses grow over −650 MPa as fluence increases to 2 × 10¹⁷ cm⁻². Compressive microstresses grow up to 2.7 GPa at a fluence of 5 × 10¹⁶ cm⁻², and up to 6.8 GPa at 2 × 10¹⁷ cm⁻². The dislocation density rises by a factor of 5–12 for a fluence of 5 × 10¹⁶ cm⁻², and by 30–60 for a fluence of 2 × 10¹⁷ cm⁻². Stresses and dislocation density in the HEAs change the most in the region of the maximal damage dose. NiCoFeCrMn has higher macro- and microstresses, dislocation density, and a larger increase in their values, with an increasing helium ion fluence compared to NiCoFeCr. NiCoFeCrMn a showed higher radiation resistance compared to NiCoFeCr.

This work studied the effect of sequential irradiation by krypton and helium ions at room temperature on the composition and structure of CoCrFeNi and CoCrFeMnNi high-entropy alloys (HEAs). Irradiation of the HEAs by 280 keV Kr¹⁴⁺ ions up to a fluence of 5 × 10¹⁵ cm^–2 and 40 keV He²⁺ ions up to a fluence of 2 × 10¹⁷ cm^–2 did not alter their elemental distribution and constituent phases. Blisters formed on the nickel surface after sequential irradiation, where large blisters had an average diameter of 3.8 μm. The lattice parameter of the (Co, Cr, Fe and Ni) and (Co, Cr, Fe, Mn and Ni) solid solutions increased by 0.17% and 0.37% after sequential irradiation, respectively. Irradiation by Kr ions led to a decrease in tensile macrostresses in the HEAs in the region of krypton ion implantation (Region I) and the formation of compressive macrostresses in the region behind the peak of implanted krypton (Region II). Sequential irradiation formed large compressive stresses in Ni and HEAs equal to −131.5 MPa, −300 MPa and −613.5 MPa in Ni, CoCrFeNi and CoCrFeMnNi, respectively, in the Region II. Irradiation by krypton ions decreased the dislocation density by 1.6–2.3 times, and irradiation with helium ions increased it by 11–15 times relative to unirradiated samples for CoCrFeNi and CoCrFeMnNi, respectively. Sequentially irradiated CoCrFeMnNi HEA had higher macrostresses and dislocation density than CoCrFeNi.

The paper presents the results of studying the structure and phase state of tungsten and tungsten-copper alloy after pulsed action of compression plasma flows and irradiation with helium ions. The compression plasma flows were used to modify the surface layer of tungsten, as well as to create an alloy based on tungsten and copper. Using scanning electron microscopy and X-ray structural analysis, the formation of radiation defects on the tungsten surface was detected in the form of local areas of exfoliation and destruction, which begin to form at helium ion irradiation doses of 2 × 10¹⁷ cm⁻². It is shown that preliminary plasma treatment of the surface in the melting mode leads to the complete disappearance of surface radiation defects up to a dose of 2 × 10¹⁷ cm⁻², which may be associated with the formation of a fine-crystalline grain structure, the intergranular boundaries of which serve as effective sinks for primary radiation defects.

The results of a tungsten–niobium alloy synthesis by the impact of pulsed compression plasma flows are presented. Tungsten plates with a 2 μm thin niobium coating were treated with dense compression plasma flows generated by a quasi-stationary plasma accelerator. The plasma flow with an absorbed energy density of 35–70 J/cm² and pulse duration of 100 μs melted the niobium coating and a part of the tungsten substrate, which caused liquid-phase mixing and WNb alloy synthesis. Simulation of the temperature distribution in the top layer of the tungsten after the plasma treatment proved the formation of the melted state. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to determine the structure and phase composition. The thickness of the WNb alloy was 10–20 μm and a W(Nb) bcc solid solution was found.

Bulk samples of CoCrFeNi and CoCrFeMnNi high-entropy alloys, prepared by arc melting from a powder of a purity up to 99.97% under an argon atmosphere followed by annealing (1150°С, 24 and 72 h) and cold rolling (85% reduction in thickness), are irradiated with He²⁺ ions (energy of 40 keV, fluence of 2 × 10¹⁷ cm^–2). CoCrFeNi and CoCrFeMnNi samples are substitutional solid solutions with a composition close to equiatomic and a uniform distribution of elements over the depth of the alloys. They have a coarse grain structure with a grain size of about 80 µm for CoCrFeNi and 100 µm for CoCrFeMnNi. The surface microstructure and the phase and elemental compositions of high-entropy alloys are resistant to irradiation. No traces of radiation erosion or changes in the elemental and phase compositions of the alloys are found. In alloys, the dislocation density increases, which leads to a decrease in the size of the coherent-scattering regions, and helium bubbles are also formed, leading to an increase in compressive macrostress. Tensile microstress prevails in irradiated CoCrFeNi alloys, while compressive stress prevails in CoCrFeMnNi alloys. High-entropy CoCrFeMnNi alloys with a more complex composition are more resistant to radiation damage.