Interfacial microstructure and chemical stability during diffusion bonding of single crystal Al2O3-fibres with Ni25.8Al9.6Ta8.3Cr matrix

BN coated Al2O3 fibre-reinforced NiAl-alloy composites were fabricated by hot pressing at 1 200-1 400 (C, and the interfacial microstructure and chemical stability of BN coated Al2O3 fibre-reinforced NiAl-alloy composites were investigated by scanning electron microscopy (SEM) and analytical transmission electron microscopy (TEM). It was found that the complicated chemical reactions and diffusion processes happened in the interface area between BN-layer and Ni25.8Al9.6Ta8.3 during the hot pressing at 1 200-1 400 (C. A continuous AlN-layer was formed at the interface due to the reaction between NiAl and BN. At the same time, Cr diffused extensively into the BN-layer and reacted with boron to form Cr boride precipitates (Cr5B3). In addition, a few particles of Ta-rich phase were also precipitated in NiAl matrix near the interface.