INVESTIGATION ON THE 1000, 1150 AND 1400-DEGREES-C ISOTHERMAL SECTIONOF THE TI-AL-NB SYSTEM

The 1000, 1150 and 1400 degrees C isothermal sections of the Ti-Al-Nb system have been determined using a diffusion couple technique. A seri es of ternary alloys in the single-phase or multi-phase regions has be en employed to identify the phase relations shown in these isothermal sections. A new ternary phase yl has been identified. Several of the b inary phases were found to have extensive solubilities, which increase d with increasing temperature. The binary compounds TiAl3 and NbAl3 fo rm a continuous solid solution in the ternary system. Determination of these phase relations was accomplished through the use of electron mi croprobe analysis (EPMA), X-ray diffraction (XRD) and microstructure o bservations.