Abstract:
Aluminum alloys, owing to their exceptional combination of properties including low density, intrinsic lightweight nature, high specific strength and hardness, and outstanding corrosion resistance, have become core structural materials in critical sectors such as aerospace, automotive manufacturing, electronics, and telecommunications. The emergence of additive manufacturing (AM), particularly laser powder bed fusion (LPBF) technology, has brought about a revolutionary transformation in the design and manufacturing of geometrically complex aluminum alloy components. Such components are often difficult or impossible to produce using conventional manufacturing methods. As one of the core laser-based additive manufacturing technologies, LPBF utilizes a high-energy laser beam to selectively melt and fuse fine metallic powder layers within a precisely controlled atmosphere, enabling the layer-by-layer fabrication of intricate near-net-shape parts. This capability places LPBF at the forefront of cutting-edge additive manufacturing research and industrial applications for high-value aluminum alloy parts. This review systematically synthesizes and analyzes the significant research progress achieved in the LPBF processing of aluminum alloys. It begins by outlining the fundamental physical principles of the LPBF process and elucidates its unique advantages compared to traditional subtractive or formative manufacturing techniques (such as casting and forging), including unparalleled design freedom, minimal material waste, and the potential for rapid prototyping and customized production. Concurrently, the review candidly identifies the major challenges currently hindering the broader adoption of LPBF for aluminum alloys. These challenges include the persistent narrowness of the LPBF processing window, difficulties in controlling metallurgical defects, the challenge of simultaneously enhancing strength and ductility (strength-ductility trade-off), pronounced sensitivity associated with columnar grain-dominated solidification microstructures, significant hurdles in engineering application scale-up, and limitations in existing alloy systems specifically optimized for the rapid solidification characteristics inherent to LPBF. Furthermore, the review provides a comprehensive overview of the current research status concerning several industrially crucial wrought aluminum alloy systems processed via LPBF. These primarily include Al-Cu (2xxx series), Al-Mg (5xxx series), Al-Mg-Si (6xxx series), and ultra-high-strength Al-Zn-Mg-Cu (7xxx series) alloys. The review encompasses major advancements and ongoing developments across multiple interconnected domains: (1) Fundamental theoretical research: Focusing on understanding complex melt pool dynamics, rapid solidification mechanisms, unique microstructure evolution pathways, and defect formation kinetics specific to the LPBF thermal cycle; (2) Process development and optimization: Involving extensive studies on process parameters (laser power, scan speed, hatch spacing, layer thickness, scan strategy); (3) Material innovation: Including the development of novel aluminum alloy compositions and the modification of existing alloys through strategies such as grain refiners and nanoparticle additions to enhance their LPBF processability and final properties; and (4) Performance characterization: Detailing methodologies and research findings for evaluating the microstructure and mechanical properties of LPBF-fabricated aluminum alloy components. A comprehensive discussion delves into the critical factors governing the final microstructure and properties of LPBF-formed aluminum alloys, encompassing the influence of powder characteristics on powder spreading quality and melting behavior; the role of alloy composition in dictating solidification characteristics, phase transformation behavior, and defect suppression; the decisive control exerted by process parameters over melt pool morphology, densification, residual stress, and microstructural development; along with the essential function of post-heat treatments in eliminating residual stresses, regulating precipitate distribution and morphology, and ultimately optimizing comprehensive mechanical properties. Finally, the review rigorously examines the core scientific and technological problems persisting within current LPBF aluminum alloy technology. Building upon this critical analysis, it proposes forward-looking perspectives on future research directions. The ultimate objective is to provide robust scientific insights and theoretical underpinning to guide the development of next-generation, LPBF-dedicated aluminum alloys. These future alloys aim to significantly reduce hot cracking susceptibility while simultaneously achieving an optimized combination of high strength, high toughness, superior fatigue performance, and excellent corrosion resistance, thereby fully unlocking the potential of LPBF technology for demanding structural applications.