Ni3Al intermetallic compound as second phase in Al2O3 ceramic composites

Several metals have been proposed as second phases in ceramic matrix composites in order to improve their fracture toughness. Unfortunately, the use of metals is limited by low melting temperature, as for Al and Ag, poor oxidation resistance, as for Ni, Mo and W, and decrease of mechanical strength as temperature increases. In these respects, high temperature structural intermetallics show better properties. This work presents the preparation and the characterization of a Ni3Al reinforced-alumina. A ceramic composite containing 10 vol% Ni3Al powder was prepared by hot-pressing at 1350°C for 1.5 h green compacts of the mixture of ceramic and intermetallic powder. Microstuctural features were investigated by scanning electron microscopy (SEM). Elastic modulus, flexural strength and fracture toughness were measured at room and high temperatures and correlated to the micro structural characteristics of the material. A toughening mechanism due to plastic deformation of the intermetallic particles during crack propagation was seen to operate both at room and at high temperature.