CALPHAD based software and databases allow a high fidelity calculation of phase equilibria in multicomponent Ti- and γ-TiAl-based alloy systems.

Comparing with empirical regression analysis and artificial neural networks, the CALPHAD approach offers a unique and remarkable advantage in accurately obtaining all critical features at the same time for a wide spectrum of conventional Ti-alloys.

Examples of calculation results for conventional Ti-alloys:

  • β transus temperature Tβ
  • Sensitivity of Tβ to impurity content of O, C and N
  • Volume fraction of α and β
  • Partitioning of alloying elements between α and β phases
  • Formation of minor phases such as carbides, Laves phase and α2-Ti3Al
  • α/β To line

Knowledge of the above information through computational thermodynamics provides us a better, cheaper and faster way to tailor materials chemistry, optimise heat treatment schedules and enable quality assurance.

For γ-TiAl-based alloys, users frequently calculate:

  • α transus temperature
  • α2+γ eutectoid temperature
  • Formation of the B2 phase
  • Formation of minor phases such Ti5Si3 etc.

Due to the fact that the approach is based on thermodynamics, various important thermodynamic properties can also be readily calculated and utilised in kinetic simulations of phase transformation and microstructural evolution, such as:

  • Activity or chemical potential of all elements
  • Driving force for nucleation and growth
  • Specific heat

By using the Diffusion module (DICTRA) and combining both thermodynamic and kinetic databases, typical diffusion-controlled phase transformations in Ti-alloys can be simulated under arbitrary heat treatment conditions. Some examples of applications are:

  • Growth or dissolution of globular or plate alpha phase
  • Dissolution of minor phases, such as carbides, Laves phase, etc.
  • Nitriding
  • Solidification
MOBTI1 is the specialised Titanium-based database and is intended for use with the TTTI3 database.