Charged particles: Unique tools to study irradiation resistance of concentrated solid solution alloys

Abstract

• Both energetic ions and high-energy primary recoils induce defect processes in complex alloys that are consequences of the spatial and temporal coupling of atomic displacement processes and energy dissipation from ionization. • Chemical disorder does not monotonically increase with more alloying elements but can be tuned by specific alloying elements and the corresponding concentrations. • Differences between ions and neutrons need to be taken when relying on ion beam testing for reactor applications. Many multicomponent concentrated solid solution alloys (CSAs), including high-entropy alloys (HEAs), exhibit improved radiation resistance and enhanced structural stability in harsh environments. To study and assess irradiation resistance of nuclear materials, energetic ion and electron beams are commonly used to create displacement damage. Moreover, charged particles of ions, electrons, and positrons are unique tools to create and characterize radiation effects. Ion beam analysis (e.g., Rutherford backscattering spectrometry, nuclear reaction analysis, and time-of-flight elastic recoil detection analysis), electron microscopy techniques (e.g., transmission or scanning electron microscopy, and electron diffraction), and positron annihilation spectroscopy have been applied to characterize irradiated CSAs or HEAs to understand defect formation and evolution together with chemical and microstructural information. Their distinctive analyzing power and some perspectives in these techniques are reviewed. In developing structural alloys desirable for applications in advanced reactors, neutron exposure is a critical test but the limitation in achievable high damage levels is, however, a bottleneck. Ion irradiation is often used as a surrogate for neutron irradiation, and the associated reduced transmutations and higher displacements per atom (dpa) rates are desirable for materials research. Nevertheless, cautions need to be taken when relying on ion irradiation results for reactor evaluations. Literature on differences between ions and neutrons is briefly reviewed. In addition, the links to bridge the current advances on fundamental understandings to reactor applications are discussed to lay the groundwork between neutrons and ions for radiation effects studies.