The typical cellular microstructures developed in powder-based additively manufactured metallic materials: formation mechanisms, properties, outlooks and challenges

Cellular microstructures are intrinsically associated with the printability and mechanical-functional performance of laser-additively manufactured metallic materials. An in-depth understanding of formation mechanisms under extreme processing conditions and impacts on mechanical-functional performance remains critical to improving the application prospects of laser additive manufacturing. In this paper, vital insights into the characteristics, formation mechanisms, mechanical-functional performance, and prospects of cellular microstructures are orchestrated and articulated. First, the differences between dislocation cellular microstructures obtained from conventional methods and those induced by additive manufacturing are summarised through a comparative analysis. Based on the diverse environments of sub-boundaries, almost all cellular microstructures in metallic materials are then exemplified and classified into three categories: dislocation-formed cellular microstructures, both with and without elemental segregation, and eutectic-formed cellular microstructures. For each category, its formation mechanisms related to analysis approaches and evaluation of mechanical-functional performance are delineated and discussed in detail. Finally, insights into the formation mechanisms, model development, thermal stability of cellular microstructures, and countermeasures for aspects of their negative influence on printability and performance are presented. Collectively, this systematic review of cellular microstructures provides a foundational framework to guide the design, manufacture, and industrial-scale implementation of high-performance metallic components.