Fabrication of Al2O3-based composites by indirect 3D-printing

A powder mixture of alumina and dextrin was used as a precursor material for fabrication of porous alumina preforms by indirect three-dimensional printing. Post-pressureless infiltration of the fabricated preforms with copper alloys resulted in dense composites with interpenetrating microstructure. The fabrication procedure involves four steps: a) freeze-drying of Al2O3/dextrin blends, b) three-dimensional printing of the green bodies, c) drying, dextrin decomposition and sintering of the printed bodies and d) post-pressureless infiltration of Cu-alloy into as-fabricated Al2O3 porous preforms. As result of the dextrin decomposition and Al2O3 sintering an average linear shrinkage of 17.7% was measured. After sintering the Al2O3 preforms with similar to 36 vol.% porosity were obtained. A post-infiltration with copper alloy at 1300 degrees C for 1.5 h led to formation of dense Al2O3/CU parts. X-ray analysis showed the presence of alpha-Al2O3, Cu and Cu2O only. Al2O3/Cu composite exhibits a fracture toughness of similar to 5.5 MPa m(1/2) and bending strength of similar to 236 MPa. Fractographic analysis showed that crack bridging by plastically deformed metal phase may control the fracture toughness of this composite. (c) 2005 Elsevier B.V All rights reserved.