High-entropy alloys (HEAs) present a vast compositional design space, characterized by four core effects—high configurational entropy, sluggish diffusion, severe lattice distortion, and the cocktail effect—which collectively underpin their exceptional potential for both structural and hydrogen storage applications. This mini-review synthesizes recent advances in the compositional design of HEAs with emphasis on structural materials and hydrogen storage. Firstly, it provides an overview of the definition of HEAs and the roles of principal alloying elements, then synthesizes solid solution formation rules based on representative descriptors—atomic size mismatch, electronegativity difference, valence electron concentration, mixing enthalpy, and mixing entropy—together with their applicability limits and common failure scenarios. A brief introduction is provided to the preparation methods of arc melting and powder metallurgy, which have a strong interaction with the composition. The design–structure–property links are then consolidated for structural materials (mechanical properties) and for hydrogen storage materials (hydrogen storage performance). Furthermore, the rules for the combined design of control systems for HEAs and the associated challenges were further discussed, and the future development prospects of HEAs in structural materials and hydrogen storage were also envisioned.

This study examines the microstructural evolution and tensile response of a cold-rolled C17200 Cu–Be–Co alloy strip after short-time annealing at 550 and 610 °C. X-ray diffraction (XRD), electron backscatter diffraction (EBSD), kernel average misorientation (KAM) analysis, transmission electron microscopy (TEM), and room-temperature tensile testing were used to compare phase constitution, grain-boundary character, recrystallization behavior, texture evolution, dislocation substructure, and tensile properties. The results show that both annealed samples mainly consisted of an α-Cu matrix and a small amount of BeCu-related precipitates. After annealing at 550 °C, the alloy retained a recovery-dominated partially recrystallized microstructure, with an average grain size of 1.47 μm, a low-angle grain boundary fraction of 8.4%, a recrystallized fraction of 18.06%, and evident residual dislocation substructures. This condition exhibited a yield strength of 365.5 MPa. After annealing at 610 °C, recrystallization was substantially promoted, the average grain size increased to 1.92 μm, the high-angle grain boundary fraction increased to 97.5%, and the recrystallized fraction reached 82.76%. Meanwhile, the yield strength decreased to 276.6 MPa because of the reduced contribution from dislocation strengthening. These results indicate that, under the two investigated short-time annealing conditions, the strength difference in the alloy is mainly associated with the transition of microstructural evolution from recovery-dominated partial recrystallization to a recrystallization-dominated microstructure.

Be–Al alloys are attractive for aerospace and precision-engineering applications because of their low density, high specific stiffness, and excellent dimensional stability. However, their broader application is constrained by multiscale defects arising from the low mutual solubility of Be and Al, their large melting-point difference, and the high reactivity of the Be/Al interface. This review critically examines defect formation and microstructural evolution in Be–Al alloys produced by casting, powder metallurgy, pressure infiltration, thermomechanical processing, and additive manufacturing, with particular emphasis on additive manufacturing. Rapid solidification can refine the Be-rich phase and suppress coarse segregation, but unstable melt-pool behavior, restricted gas escape, cyclic thermal loading, and insufficient interfacial diffusion may also promote porosity, compositional heterogeneity, residual stress, and interfacial degradation. The mechanical properties of Be–Al alloys depend strongly on Be-phase morphology, continuity of the Al matrix, interfacial integrity, and the spatial distribution of processing-induced defects. Recent progress in alloy design, process optimization, interfacial engineering, and post-processing is evaluated, together with the limitations of the available evidence. Future research should establish quantitative processing–defect–microstructure–property relationships through in situ monitoring, multiscale characterization, predictive modeling, and standardized mechanical validation. These advances are essential for the reliable manufacture of complex, high-performance Be–Al components.