Combustion synthesis of Al2O3(-Cr2O3)-Cr cermets

Al2O3(-Cr2O3)-Cr cermets are synthesized from the 2Al+Cr2O3 yields 2Cr+Cr2O3+Al2O3 reaction, and the influence of the reactant compact composition on product microstructures is investigated. With the addition of Al2O3 in reaction compacts, Al2O3-Cr cermets consisted of chromium particles and Al2O3 matrix, and no eutectic microstucture was found. While excess Cr2O3 was introduced into reaction compacts, a eutectic microstructure containing rocklike chromium was observed. The cermets consisted of chromium particles, Al2O3-Cr2O3 solid solution matrix, and (Al,Cr)2O3-Cr eutectic regions. The chromium content in the matrix of eutectic regions is higher than that in the matrix of noneutectic regions, while the aluminum content is the opposite. The toughening effect of Cr in Al2O3(-Cr2O3)-Cr cermets produced by combustion synthesis is better than that by conventional powder metallurgy due to the eutectic formation in the former. (AIAA)