Microstructure-controlled strengthening mechanisms and strategies in additively manufactured aluminum alloys: A review

Laser powder bed fusion (LPBF) has emerged as an important but challenging route for producing high-strength aluminum alloys. However, existing studies often treat individual alloy systems or specific defects in isolation, which obscures the overall links between microstructural evolution, strengthening mechanisms, and strengthening strategies. This review addresses that gap by establishing a comprehensive, mechanism-based framework for the rational design of LPBF processing and aluminum alloys. We organize the discussion around a systematic causal chain linking microstructure, strengthening mechanisms, and strengthening strategies. The strengthening contributions are classified into five categories: Grain-boundary, solid-solution, precipitation, dislocation, and load-bearing strengthening. On this basis, we distill three transferable classes of practical strategies—process optimization, alloy design, and post-heat treatment—and clarify how they tailor high strength across different alloy families. The resulting mechanism-based framework links LPBF processing conditions, microstructures, strengthening mechanisms, and strengthening strategies in a unified manner. It provides a common reference for researchers and practitioners designing high-strength LPBF-processed aluminum alloys and highlights key directions where further quantitative and mechanistic studies are needed.