Multi-material additive manufacturing of a bio-inspired layered ceramic/metal structure: Formation mechanisms and mechanical properties

The performance enhancement of laser additive manufactured components depends on structural innovation and tailored printing, and the naturally optimized structures can provide inspiration for design and manufacturing. In this work, a layered TiB2/Ti6Al4V structure inspired by the biological structure of the Crysomallon squamiferum shell was designed and built by multi-material laser powder bed fusion (LPBF). The mechanisms for material densification, element diffusion, interfacial reaction, crystal growth and performance enhancement of multi-material LPBF-processed layered TiB2/Ti6Al4V parts were revealed by experiments and simulations. A strategy of process optimization by alternating appropriate printing parameters for metallic and ceramic materials yielded fully dense multi-material parts without discernible interfacial defects. The microstructure control showed that TiB whiskers were generated by the in-situ reaction between TiB2 and Ti matrix, yielding a sound metallurgical bonding between dissimilar materials. The gradient elements and microstructures induced the gradually changed microhardness at the interface, thereby reducing the abrupt change and incoordination of microstructure and properties at the interface. The excellent flexural performance with a strength of 2033.2 MPa and a strain of 7.8% was obtained for the laser printed of TiB2/Ti6Al4V multi-material parts, revealing the contribution of the high interfacial bonding between layers to the performance enhancement. The internal crack propagation in laser-fabricated parts was fulfilled by crack deflection and multistage cracking, which extended the propagation path and increased the crack propagation energy. The flexural strength and ductility of LPBF-fabricated TiB2/Ti6Al4V multi-material parts were enhanced by the combined effects of the bio-inspired layered composite structure and the interior whiskers-structured reinforcement. This study sheds light on the manufacturing and strengthening of ceramic/metal multi-material using laser additive manufacturing technology.