Phase relationships involving TiC and Ti3AlC (P phase) in Ti-Al-C system

Titanium rich alloys of the TI-AI-C system have been investigated to determine the constitution in the range 1250 - 750 degrees C with particular reference to phase equilibria and transformations involving TIC and Ti3AlC (P phase). Alloys with varying aluminium and carbon concentrations up to 15 at.-%Al and 15 at.-%C have been studied using scanning and transmission electron microscopy and X-ray diffraction, The isothermal sections at 1250, 1050, 1000, and 750 degrees C reported by previous workers are reviewed. Equilibria involving the phases beta-Ti, alpha-Ti, Ti3Al (alpha(2)), TiC, and Ti3AlC (P phase) have been investigated and partial isothermal sections at 1050 and 750 degrees C are presented. A revision of the previously established TI-AI-C isothermal section at 750 degrees C is shown involving equilibria of alpha + alpha(2) + P and alpha + P + TiC. The orientation relationship between the P phase and Ti-Al (alpha/alpha(2)) matrix has been found to be (0001)(alpha/alpha 2)//{111}(P) and [1 (2) over bar 10](alpha/alpha 2)//[110](P). MST/4603.