When calculating the Ti-Al phase diagram why do I see odd looking phase boundaries for the TiAl and Ti3Al phases?
TiAl and Ti3Al (as well as many other phases in the SGTE Solution database) have been treated with a two sublattice model that takes care of the atomic long range ordering of these phases. The phase constituents of TiAl for example are Ti1Al1, Ti1Ti1, Al1Ti1 and Al1Al1 or written in an overall formula (Ti,Al)1(Ti,Al)1. This means that both kinds of atoms can occupy both sites. However, there is actually a preference in site occupation such that one sublattice is mainly occupied by Ti and the other mainly by Al. Which element occupies which site is decided by the lowest Gibbs free energy of the phase. This lowest Gibbs free energy can only be found properly if TWO copies of the phase are used in the calculations, i.e. if the I-option (Immiscibility) is set for that phase. When two copies (i.e. I-Option) of TiAl and of Ti3Al are used in the phase diagram calculation the phase boundaries corresponding to the lowest Gibbs free energies of the respective phases are found and no odd looking
TiAl and Ti3Al (as well as many other phases in the SGTE Solution database) have been treated with a two sublattice model that takes care of the atomic long range ordering of these phases. The phase constituents of TiAl for example are Ti1Al1, Ti1Ti1, Al1Ti1 and Al1Al1 or written in an overall formula (Ti,Al)1(Ti,Al)1. This means that both kinds of atoms can occupy both sites. However, there is actually a preference in site occupation such that one sublattice is mainly occupied by Ti and the other mainly by Al. Which element occupies which site is decided by the lowest Gibbs free energy of the phase. This lowest Gibbs free energy can only be found properly if TWO copies of the phase are used in the calculations, i.e. if the I-option (Immiscibility) is set for that phase.
Related Questions
- Does each player complete all seven phases in the action sequence before the next player starts his or her turn or do all players complete phase one before going to phase two?
- When calculating the Ti-Al phase diagram why do I see odd looking phase boundaries for the TiAl and Ti3Al phases?
- When will the subsequent phases get underway to expand the terminal after Phase one is completed?
