FABRICATION OF AL2O3-REINFORCED NI3AL COMPOSITES BY A NOVEL IN-SITU ROUTE

A novel in situ technique has been used to fabricate an Al2O3-reinforc ed Ni3Al matrix composite. The composite was prepared by first incorpo rating a low volume fraction of continuous Al2O3 fibers in a Ni3Al all oy containing 0.34 at. pct Zr. Pressure casting was used to embed the fibers. Casting resulted in partial reduction of the Al2O3 fiber by th e Zr present in the matrix and the formation of a layer of ZrO2 on the surface of the frbers. The final composite was then prepared by air a nnealing the precursor composite at 1100 degrees C for 10 days. Air an nealing led to the formation of networks of Al2O3 around the fibers. T he matrix in the inunediate vicinity of the networks consisted of Ni3A l particles in a matrix of disordered alpha-Ni(Al). The Al2O3 networks raised the yield and tensile strength of the material by 35 and 18 pc t, respectively. The composite had a tensile ductility of 14 pct.