Vat photopolymerization 3D printing of Al₂O₃ ceramic cores with TPMS micro lattice structure

The complex ceramic core used for hollow turbine blades requires a high porosity and a high flexural strength. For a better balance between porosity and flexural strength, ceramic materials with porous structures are preferred. In order to achieve the transition from disordered pore formation to ordered pore formation, Al₂O₃ ceramic cores with triply periodic minimal surface (TPMS) micro lattice structures with different structural configurations (gyroid, diamond, and neovius) and different volume fractions of lattice structures (30, 40, and 50, vol.%) were designed and prepared by vat photopolymerization 3D printing. The effects of structural configuration and volume fraction of the lattice structure on the following structural shrinkage, microstructure, and flexural strength were investigated. The shrinkage relationship of the three lattice configurations is: neovius>diamond>gyroid. Besides, it is found that with an increase in the volume fraction of the 3D printed Al₂O₃ ceramic micro lattice structures, their flexural strength correspondingly increases ranging from 54.95 MPa to 139.1 MPa. The maximum average flexural strength of the 3D printed Al₂O₃ ceramic micro lattice structures is obtained when the structural configuration is diamond and with a volume fraction of 50vol.%, which is 139.1 MPa. Even when the volume fraction of the lattice structure is 30vol.%, that is to say the porosity is 70%, the flexural strength is as high as 50–70 MPa, which can still be maintained at a high level. In addition, when the volume fraction of the lattice structure is a certain value, the sample with diamond configuration has a higher strength. The internal pore morphology, pore size, and porosity of the cores are precisely controlled, achieving both a high porosity and a high strength. Therefore, this study maintains high porosity and high strength simultaneously, providing a new lattice structure design idea for 3D printed ceramic cores.