Metal-matrix composites are currently of interest for application in high-temperature, elevated-stress environments. Of a number of such materials currently being investigated in our laboratory, nickel aluminides reinforced with ceramic whiskers or fibers have shown promise in that the maximum operating temperature of the alloy has been extended from 800°C to 1100°C. The microstructure of the fiber/matrix interface in a nickel aluminide strengthened with ceramic fibers is detailed in this paper.
The composite material was fabricated by mixing gas-atomized −100 mesh IC-50 powder (11.7 Al, 1.76 Hf, 0.025 B wt %, bal. Ni) with Nextel 440 fiber (3M Co., nominally 70 A12O3, 28 SiO2 and 2 B2O3 wt %) to give a composite with about 20 vol % fiber. The material was placed in a heavy-walled stainless-steel can which was evacuated while being heated to 600°C to remove fiber sizing. The can was subsequently sealed and preheated at 1100° C for 2 h, then hot consolidated at high pressure for 30 s to produce a fully dense material.