Atomic-level heterogeneity and defect dynamics in concentrated solid-solution alloys

Performance enhancement of structural materials in extreme radiation environments has been actively investigated for many decades. Traditional alloys, such as steel, brass and aluminum alloys, normally contain one or two principal element(s) with a low concentration of other elements. While these exist in either a mixture of metallic phases (multiple phases) or in a solid solution (single phase), limited or localized chemical disorder is a common characteristic of the main matrix. Fundamentally different from traditional alloys, recently developed single-phase concentrated solid-solution alloys (CSAs) contain multiple elemental species in equiatomic or high concentrations with different elements randomly arranged on a crystalline lattice. Due to the lack of ordered elemental arrangement in these CSAs, they exhibit significant chemical disorder and unique site-to-site lattice distortion. While it is well recognized in traditional alloys that minor additions lead to enhanced radiation resistance, it remains unclear in CSAs how atomic-level heterogeneity affects defect formation, damage accumulation, and microstructural evolution. These knowledge gaps have acted as roadblocks to the development of future-generation energy technology. CSAs with a simple crystal structure, but complex chemical disorder, are unique systems that allow us, through replacing principal alloying elements and modifying concentrations, to study how compositional complexity influences defect dynamics, and to bridge the knowledge gaps through understanding intricate electronic- and atomic-level interactions, mass and energy transfer processes, and radiation resistance performance. Recent advances in defect dynamics and irradiation performance of CSAs are reviewed, intrinsic chemical effects on radiation performance are discussed, and direction for future studies is suggested.