REACTIVE HOT COMPACTION OF NIAL WITH IN-SITU ALUMINA REINFORCEMENT

A reactive hot compaction process has been usd to produce interconnected Al2O3 reinforcements in situ in an NiA1 matrix. The process involved blending of Ni and Al powders in which one of the constituents was pre-oxidized, followed by reactive hot pressing. The fracture toughness of the materials was found to depend on the volume fraction and the morphology of the alumina reinforcement phase, which is determined by the type of oxidation treatment employed. Oxidation of the Al powders resulted in the formtion of a dispersed or rod-like network while oxidizing the Ni powders produced a tubular network. The oxidation treatment was found to be the critical step for the development of the proper alumina morphology to maximize fracture toughness. The highest room temperature fracture toughness obtained in these experiments was 14 MPa m(1/2) at differential thermal analysis 18 vol.%. The processing sequence and its effect on the alumina morphology are presented based on and interrupted quenching experiments.