Bioinspired interpenetrating-phase metal composites

The ingeniously complex architectures of biological materials evolved in Nature are a source of inspiration for the design of man-made materials. This has led to a major research field over the past two decades to characterize and model the properties and mechanisms induced by such hierarchical biological structures. However, the inability to manufacture synthetic structural materials incorporating these natural designs in the form of bioinspired materials has been a major "road block". Here we examine recent processes that can serve to overcome this issue, specifically by infiltrating a metal melt into porous scaffolds of reinforcement. Indeed, the melt infiltration technique offers an effective means for constructing bioinspired architectures in metallic materials, thereby affording the creation of high-performance bioinspired metal composites. The bioinspired architectures, wherein the constituents are mutually interpenetrated in 3D space often in line with specific configurations, have been proven to be effective for combining the property advantages of constituents, retarding the evolution of damage, and playing a toughening role by resisting crack propagation; as such, these effects confer a great potential towards achieving outstanding properties. This review elucidates the prerequisite conditions for melt infiltration processing, and introduces the technical routes for fabricating bioinspired metal composites via melt infiltration by highlighting the different approaches for constructing porous scaffolds of reinforcement. The formation, structure, and mechanical and functional properties of these composites are elaborated in conjunction with the state-of-the-art progress to provide a special focus on the effects of bioinspired architectures. On this basis, the existing challenges and future prospects for bioinspired metal composites are discussed and outlooked. The implementation of bioinspired designs in metallic materials by melt infiltration may afford breakthroughs in material performance with a promising potential towards engineering applications.