Process–structure–property relationships in lightweight alloys (Al & Ti) under L-PBF: from defect formation to intelligent design

Abstract Additive manufacturing of lightweight metallic alloys, particularly aluminum- and titanium-based systems, has emerged as a transformative approach for producing high-performance components with unprecedented design freedom. Among available technologies, laser powder bed fusion (L-PBF) offers superior geometrical resolution and microstructural control; however, the successful processing of lightweight alloys remains constrained by fundamental challenges related to printability, defect formation, and microstructural heterogeneity. This review critically examines the process–structure–property relationships governing L-PBF fabrication of aluminum and titanium alloys, with a specific focus on the mechanisms of defect generation and their implications for mechanical performance. First, the unique thermophysical characteristics of lightweight alloys—including high reflectivity, oxidation tendency, and rapid solidification kinetics—are analyzed in the context of melt pool dynamics and thermal gradients. Second, alloy-specific microstructural evolution is discussed, highlighting the formation of cellular structures in Al–Si systems and martensitic transformations in Ti–6Al–4 V, alongside their dependence on process parameters. Third, the dominant defect mechanisms, including lack-of-fusion porosity, keyhole-induced voids, hydrogen gas porosity, and hot cracking, are systematically compared between aluminum and titanium alloys, establishing clear cause–effect relationships between processing conditions and structural integrity. Building upon these insights, the review integrates recent advances in computational modeling approaches—such as CALPHAD, phase-field simulations, and machine learning—to demonstrate how predictive frameworks can guide alloy design and process optimization. A cross-material comparison is further developed to identify critical differences and shared limitations in printability and performance. Finally, a unified design strategy is proposed, linking process control, alloy chemistry, and defect mitigation to enable the development of next-generation lightweight materials tailored for additive manufacturing. This work provides a focused and analytical perspective that bridges fundamental mechanisms with practical design strategies, offering a roadmap for advancing lightweight alloy applications in aerospace, automotive, and energy sectors.