Strength and Toughness of Ceramic-metal Prepared by Reactive Hot Pressing Composites

William G. Fahrenholtz o 9m Ceramic Engineering Department ‘so University of Missouri-Rolls w~!!l Rolls, MO 65409 + <. +# Metal-reinforced Alz03-matrix composites were prepared using reactive hot pressing. The volume fraction of the reinforcing phase was controlled by the stoichiometry of the particular displacement reaction used. Dense Alz03-Ni and Al@3-N’b composites were fabricated using this technique. ‘i’hebest combination of strength, 610 MPa, and toughness, 12 Mp~ln, Wm fo~d for the Al@3-Ni . composites. Indentation cracks and fracture surilaces showed evidence of ductile deformation of the Ni phase. The &03-Nb composites had high strength, but the toughness was lower than expected due to the poor bonding between the Nb and A1203phases. INTRODUCTION Metal-reinforced ceramics offer the potential for improved strength and toughness compared to monolithic ceramics. These composites combine the high elastic modulus, hardness and low density of the ceramic phase with the high ductility of the metallic phase to produce composites with properties unattainable from either pure ceramics or pure metals. Of the ceramic-metal systems studied, A1203-Al composites have probably received the most attention. A number of processing techniques have been developed to fabricate A1203-Al composites, including directed metal oxidation [1], reactive metal penetration [2], displacement reactions between Al and SiOz [3], and the pressure infiltration of Al into porous Alz03 preformso[4] The most significant factor limiting the use of Alz03-Al composites is its low use temperature due to the relatively low melting temperature of aluminum. Many of the potential applications for ceramic-metal composites require higher use temperatures than are attainable in the A1203-Al