Interfacial porosity modulates fracture of brick-and-mortar multi-metal composites in additive manufacturing

Multi-material structures have shown great versatility in wide applications. However, additive manufacturing of multi-metal mechanical composite structures is challenging. Beyond this, a comprehensive and multi-scale understanding of the fracture mechanisms in such structures has not been sufficiently elucidated. In this study, we exploited synchrotron phase contrast X-ray computed tomography and synchrotron X-ray ptychographic tomography to achieve in situ , continuous observation of the fracturing process in large-scale brick-and-mortar multi-metal composite structures, resolving phenomena spanning from the micro- to nano- scale. Findings suggest that nano-pores prevailingly exist in additively manufactured metals, and interfacial porosity as a transitional geometry between different materials can retard the crack growth and improve fracture toughness. This multi-scale study directly informs the designing, manufacturing, and testing of multi-metal composite structures.