Reduced-activation complex concentrated alloys

In order to satisfy the stringent performance requirements for future advanced fission and fusion reactors, there is a need for the development of new high-performance, low-activation materials. Reduced-activation complex concentrated alloys (RACCAs) have been developed and investigated extensively very recently in response to this situation. RACCAs can provide excellent mechanical properties and radiation resistance at a wide temperature range. This article provides a thorough summary of the development of low-activation materials and the fundamental features of complex concentrated alloys (CCAs). We classify the RACCAs into four categories, based on their chemical composition: (1) reduced-activation complex concentrated titanium alloys (RACCTAs), (2) reduced-activation complex concentrated vanadium alloys (RACCVAs), (3) reduced-activation complex concentrated steels (RACCSs), and (4) reduced-activation complex concentrated tungsten alloys (RACCWAs). Most RACCAs possess a single-phase body-centered cubic (bcc) matrix, sometimes accompanied by the formation of precipitation phases such as Laves, B2, or σ phases. Due to its wide compositional space, RACCTAs cover a wide range of mechanical properties at room temperature, which can be compared with reduced-activation ferrite/martensite (RAFM) steels and ODS steels. The high strength can be derived from strong solid solution strengthening, short-range clustering strengthening, precipitation strengthening, etc. The deformation of RACCAs at room temperature is primarily governed by dislocation slip, but twinning and phase transformation may occur during the deformation of RACCAs with metastable bcc phases. Twining-induced plasticity and transformation-induced plasticity can be effectively applied in the RACCAs to enhance the work hardening and ductility. RACCWAs possess the highest compressive strength at room temperature and exhibit excellent mechanical properties at elevated temperatures. The excellent radiation resistance of RACCAs is believed to stem from a large overlap of point defect migration energies, severe lattice distortion, sluggish diffusion effects, and a self-healing effect. Additionally, the article places particular emphasis on highlighting novel and promising avenues for future research.