CHEMICAL-STABILITY OF TITANIUM DIBORIDE REINFORCEMENT IN NICKEL ALUMINIDE MATRICES

Chemical stability of titanium diboride (TiB2) reinforcement in NiAl ( 45 at% Al) and Ni3Al (24 at% Al) matrices has been theoretically and e xperimentally investigated. Calculations were made using thermodynamic properties of the systems to predict behaviour at temperatures betwee n 1173 and 1573 K. Experimental investigation of hot-press consolidate d TiB2 particulate/prealloyed matrix powder blends were conducted usin g energy dispersive X-ray analysis, X-ray diffraction analysis, Auger electron spectroscopy and transmission electron microscopy. The theore tical and experimental analyses suggest that TiB2 is chemically stable in both matrices up to 1573 K, however, TiB2 was found to be less act ive in NiAl than in Ni3Al due to lower nickel activity in NiAl.