Role of electronic energy loss on defect production and interface stability: Comparison between ceramic materials and high-entropy alloys. Issue 4 (August 2022)

• Record Type: Journal Article
• Authors: Zhang, Yanwen; Silva, Chinthaka; Lach, Timothy G.; Tunes, Matheus A.; Zhou, Yufan; Nuckols, Lauren; Boldman, Walker L.; Rack, Philip D.; Donnelly, Stephen E.; Jiang, Li; Wang, Lumin; Weber, William J.
• Is Part Of: Current opinion in solid state & materials science. Volume 26:Issue 4(2022)
• Publication Date: 2022-08
• Subjects: Radiation damage -- High-entropy alloys -- Chemically complex alloys, nanocrystalline alloys -- Crystallites -- Electronic energy loss -- Displacement damage, grain growth; Materials science -- Periodicals; Solid state physics -- Periodicals; 620.11
• DOI: 10.1016/j.cossms.2022.101001
• Languages: English
• ISSNs: 1359-0286

Abstract

Graphical abstract: Highlights: Ionization effects and the associated chemical complexity should be considered to understand radiation effects in complex alloys. The coupled elastic and inelastic thermal spikes both contribute to the grain growth of nanocrystalline high-entropy alloys (HEAs). The much slower radiation-induced microstructural evolution in nanocrystalline HEAs is attributed to the sluggish diffusion and the resulting slower kinetics. Abstract: High-entropy alloys (HEAs) and some complex alloys exhibit desirable properties and significant structural stability in harsh environments, including possible applications in advanced reactors. Energetic ion irradiation is often used as a surrogate for neutron irradiation; however, the impact of ion electronic energy deposition and dissipation is often neglected. Moreover, differences in recoil energy spectrum and density of cascade events on damage evolution must also be considered. In many chemically complex alloys, the mean free path of electrons is reduced significantly, thus their decreased thermal conductivity and slow dissipation of localized radiation energy can have noticeable effects on displacement cascade evolution that is greatly different from metals with high thermal conductivity. In this work, nanocrystalline HEAs of Ni20 Fe20 Co20 Cr20 Cu20 and nonequiatomic (NiFeCoCr)97 Cu3, both having much lower room-temperature thermal conductivity than pure Ni or Fe, are chosen as model HEAs to reveal the role that electronic energy loss during ion irradiation has in complex alloys. The response of nanocrystalline HEAs is investigated under irradiation at room temperature using MeV Ni and Au ions that have different ratios of electronic energy to damage energy, which is the energy dissipated in displacing atoms. Different from previously reported amorphization of nanocrystalline SiC, experimental results on these HEAs show that, similar to the process in nanocrystalline oxide materials, both inelastic thermal spikes via electron–phonon coupling and elastic thermal spikes via collisions among atomic nuclei contribute to the overall grain growth. The growth follows a power law dependence with the total deposited ion energy, and the derived value of the power-exponent suggests that the irradiation-induced instability at and near grain boundaries leads to local rapid atomic rearrangements and consequently grain growth. The high power-exponent value can be attributed to the sluggish diffusion and delayed defect evolution arising from the chemical complexity intrinsic to HEAs. This work calls attention to quantified fundamental understanding of radiation damage processes beyond that of simplified displacement events, especially in simulating neutron environments.