3D printing of Al2O3/Cu–O interpenetrating phase composite

Porous alumina preforms were fabricated by indirect 3D printing using a blend of alumina and dextrin as a precursor material. The bimodal granulate powder distribution with a bed density of 0.8 g/cm3 was increased to 1.4 g/cm3 by overprinting. The porosity of the sintered bodies was controlled by adjusting the printing liquid to precursor powder ratio in the range of 33–44 vol%. The green bodies exhibited bending strengths between 4 and 55 MPa. An isotropic linear shrinkage of ~17% was obtained due to dextrin decomposition and Al2O3 sintering at 1600 °C. Post-pressureless infiltration of the sintered preforms with a Cu–O alloy at 1300 °C for 1.5 h led to the formation of a dense Al2O3/Cu–O interpenetrating phase composite (IPC). X-ray analysis of the fabricated composites showed the presence of α-Al2O3, Cu and Cu2O. CuAl2O4 spinel was not observed at the grain boundaries during HRTEM examination. The Al2O3/Cu–O interpenetrating phase composite revealed a fracture toughness of 5.5 ± 0.3 MPam1/2 and a bending strength of 236 ± 32 MPa. In order to demonstrate technological capability of this approach, complex-shaped bodies were fabricated.