Direct laser powder-bed fusion additive manufacturing of complex-shaped TiB2-B4C composite with ultra-fine eutectic microstructure and outstanding mechanical performances

TiB2-B4C composite has various outstanding properties and great potentials in versatile high-end application fields, and currently the preparation of its monolithic counterpart with arbitrarily-complex shape is eagerly demanded. However, due to the intrinsically strong covalent-bonding and poor laser absorption performances of its constituents, it is still highly-challenging to prepare TiB2-based composite by additive manufacturing method. Herein, by direct laser powder-bed fusion additive manufacturing (selective laser sintering) and the unique strategy of in-situ synthesizing/sintering, dense and complex-shaped TiB2-B4C composites were successfully additively manufactured for the first time. More importantly, benefiting from their ultrafine eutectic micro-structures and high relative densities, the resultant TiB2-B4C composites exhibited outstanding Vickers hardness and fracture toughness respectively up to 35.6 GPa and 8.6 MPa.m(1/2), which were remarkably higher even than those of the near-fully-dense counterparts prepared by various subtractive methodologies. This work offered a reliable approach to near-net-forming high-temperature ceramic-matrix composites with arbitrarily-complex shapes and superior mechanical performances.