Mechanical properties of NiAl-AlN-Al2O3 composites

The mechanical properties of NiAl-based composites containing a dispersion of AIN particles and Al2O3 fibers were studied. NiAl matrix powder containing a dispersion of about 5 vol.% AlN was synthesized by mechanical alloying (MA) of elemental nickel and aluminum under a nitrogen gas atmosphere. Nextel 610 short fibers were used as the second reinforcement in the composite. Composites containing 5, 15 and 30 vol.% of the Al2O3 fibers in addition to the AIN dispersion particles were fabricated by hot pressing a dry blend of the MA NiAl powder and the fibers. The as-fabricated microstructures revealed that the matrix is fully dense and bonded well with the randomly distributed Al2O3, fibers. Neither chemical reaction nor cracks were observed at the fiber/matrix interface. Compressive behavior of the composites and a monolithic counterpart was studied at 1300 K and strain rates between 8.5 x 10(-4) and 2.8 x 10(-6) s(-1). The 0.2% yield stress of the composites increases with fiber volume fraction at all strain rates. The strain rate-flow stress behavior at 1300 K indicates that the strength of NiAl-5%AIN-30%Al2O3 approaches that of NASAIR 100, a first generation Ni-base single crystal superalloy. (C) 1997 Elsevier Science S.A.