Phase relationships involving TiC and Ti 3 AlC (P phase) in Ti–Al–C system

Abstract

Titanium rich alloys of the Ti–Al–C system have been investigated to determine the constitution in the range 1250–750°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°C reported by previous workers are reviewed. Equilibria involving the phases β-Ti, α-Ti, Ti₃Al (α ₂), TiC, and Ti₃AlC (P phase) have been investigated and partial isothermal sections at 1050 and 750°C are presented. A revision of the previously established Ti–Al–C isothermal section at 750°C is shown involving equilibria of α+α ₂+P and α+P+TiC. The orientation relationship between the P phase and Ti–Al (α/α ₂) matrix has been found to be (0001)_{α/α 2} ∥{111}_P and 〈12¯10〉_{α/α 2} ∥〈110〉_P.