Design of bimetallic interpenetrating biomimetic structures and additive-casting synergetic manufacturing

Inspired by biological materials like shell nacre , biphase interpenetrating materials with alternating soft and hard phases significantly enhance mechanical properties. However, their application in metallic materials is still unexplored. This study investigates the microstructure and fracture patterns of steel/aluminum interpenetrating composites with a Diamond TPMS structure, fabricated via vacuum infiltration casting. We found that steel and aluminum form a biomimetic "brick-and-mortar" structure under the Diamond framework, significantly enhancing the composites' ductility and strength . The interfacial bonding layer, composed of Fe 2 Al 5 , Al 8 Fe 2 Si, and Al 4.5 FeSi, shows a hardness far exceeding the adjacent base materials. This hardness increases unevenly with distance from the interface. Tensile tests reveal that structurally periodic interpenetrating materials outperform both trapezoidal interpenetrating and planar materials. Upon fracturing, cracks initially form at the interfacial bonding layer and gradually spread into the interpenetrating region. Subsequently, under tensile and shear stress from mechanical interlocking, brittle fractures develop between aluminum components. The crack then extends into the steel framework, causing ductile fractures and complete failure of the composite. • In vacuum infiltration casting, the interface and density of steel/aluminum composite materials are well maintained. • The strength of the steel/aluminum interface is enhanced through metallurgical bonding and mechanical interlocking. • The strength and toughness of biomimetic structured composite materials are synergistically improved. • The fracture process and damage mechanisms of interpenetrating materials have been characterized.