Defect Mechanisms and Microstructural Regulation in Be–Al Alloys Across Multiple Fabrication Routes

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.