THERMAL-STABILITY OF INTERFACES IN TI-6AL-4V REINFORCED BY SIC SIGMA-FIBERS

Interfacial reactions in Ti-6Al-4V/SiC Sigma fibres (coated with carbo n and TiB2) were studied at different temperatures (600, 700 and 1000 degrees C). Interface microstructure was investigated by scanning elec tron microscopy and Auger electron spectroscopy. A simulation of the c hemical phenomena occurring at the interfaces was carried out using po wders of pure titanium, carbon and TiB2; the reaction products were id entified by X-ray diffraction. The double coating of Sigma fibres is e ffective in delaying detrimental reactions with the matrix. At the int erfaces matrix/TiB2 and TIB2/C, the TiB and TiCx, phases form, respect ively. The protective coating of fibres shows a lifetime greater than 1000 and 750 h at 600 and 700 degrees C, respectively.