RESISTANCE OF VANADIUM-BASED ALLOYS TO RADIATION-INDUCED SEGREGATION UNDER IRRADIATION WITH HEAVY KRYPTON IONS

This work investigated changes in the morphology and elemental composition of alloys based on the V-Nb-Ta-Ti system after irradiation with ⁸⁴Kr¹⁵⁺ ions with an energy of 147 MeV and an ion fluence of 1·10¹³–1·10¹⁵ cm⁻². It was found that irradiation with krypton ions did not lead to significant damage to the surface of V, VNb, VNbTa, VNbTaTi samples, except for the formation of dark spots and chips, the size and number of which decreased from V to VNbTaTi. Scanning electron microscopy energy dispersive spectroscopy (SEM-EDS) analysis showed that the composition of all the initial samples was close to equiatomic. With increasing composition complexity from VNb to the medium entropy alloy (MEA) VNbTa, the radiation-induced segregation of elements in the samples increased, but decreased in the high-entropy alloy (HEA) VNbTaTi. The largest change in concentrations was found in VNbTa, where the Ta concentration increased by 18.5% (4.4 at.% (atomic percents)) compared to the unirradiated sample. It was found that in VNbTa and VNbTaTi, the segregation increased with increasing fluence, and in VNb, the segregation peaked at 1·10¹⁴ cm⁻² and then decreased. Using the Rutherford backscattering (RBS) analysis, it was shown that in samples irradiated with krypton ions with a fluence of 1·10¹³ cm⁻², the concentration of Ta atoms increased with depth by 33–34% (8.6–12 at.%) relative to the initial concentration. The results of the EDS and RBS analysis showed similar trends. Changes in the concentrations of elements in the near-surface layer of VNb, VNbTa and VNbTaTi for heavy elements Nb, Ta exceeded those for the light ones. The difference in the segregation of elements is probably due to the difference in lattice distortion, local chemical composition, different dependence of the migration of V, Nb, Ta, Ti atoms on vacancies and interstitials. Irradiation with krypton ions resulted in segregation in VNbTa MEA and VNbTaTi HEA, but the distribution of elements over the surface of the samples did not form distinct segregation regions. VNbTaTi HEA showed greater resistance to radiation-induced segregation.

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