Helium implantation damage resistance in nanocrystalline W-Ta-V-Cr high entropy alloys. (March 2021)

• Record Type: Journal Article
• Authors: El-Atwani, O.; Alvarado, A.; Unal, K.; Fensin, S.; Hinks, J.A.; Greaves, G.; Baldwin, J.K.S.; Maloy, S.A.; Martinez, E.
• Is Part Of: Materials today energy. Volume 19(2021)
• Publication Date: 2021-03
• Subjects: HEA -- In-situ TEM -- He bubbles -- Electron microscopy -- Migration energy; Energy development -- Periodicals; Energy industries -- Periodicals; Power resources -- Periodicals; Energy policy -- Periodicals; Energy development; Energy industries; Energy policy; Power resources; Electronic journals; Periodicals; 621.042
• DOI: 10.1016/j.mtener.2020.100599
• Languages: English
• ISSNs: 2468-6069

Abstract

Abstract: Nanocrystalline W-Ta-Cr-V high entropy alloys have shown promising properties as nuclear fusion materials with enhanced radiation resistance to heavy ion irradiation and negligible radiation hardening. In this work, we investigate the performance of the alloy under low energy helium (He) implantation up to a fluence of 1.25 × 10 17 cm −2 at 1223 K. We observe a uniform high density of very small (~2–3 nm) bubbles grown at a slow rate along with enhanced He bubble damage resistance, further marked by no preferential bubble formation on the grain boundaries, even at much higher fluences compared to previously implanted tungsten grades. First principle calculations of He formation and migration energies in this alloy indicate deep energetic wells on the potential landscape and low diffusivity of He compared to pure W. The results imply higher overall (considering both grain matrices and grain boundaries) implantation resistance due to slow He diffusion and accumulation, and confirm the enhanced vacancy-self interstitial recombination argument in these alloys. Graphical abstract: Interstitial helium properties in W-Ta-Cr-V HEA elucidate their high implantation damage resistance. (a) Formation, (b) solution and (c) migration energies of helium in the HEA. (d) An example of minimum energy path of one hop of an interstitial helium between two stable sites. Image 1 Highlights: In-situ TEM/low energy He implantation experiment is performed on nanocrystalline W-Ta-Cr-V high entropy alloy. High density of very small bubbles are observed with no large bubble formation on grain boundaries. The overall implantation resistance is higher than nanocrystalline W and ultrafine W-TiC alloys. The implantation resistance in the HEA stems from favorable defect properties and matrix chemistry.