A thermodynamic description of the Al-B-Er system

The Al-B-Er ternary system was optimized by means of the CALPHAD (CALculation of PHAse Diagram) technique. The solution phases, liquid and hcp, were described by the substitutional solution model. The compounds AlB12, AlB2, B2Er, B4Er, B12Er, B66Er, AlB4Er and AlB14Er were treated as stoichiometric compounds. In the present study, in order to describe the structural relationship between the solution phase fcc(A1) (disordered part) and the phase L12 (cP4-AuCu3-type, ordered part), the two phases were modeled as (Al,B,Er)1(Va)1 and (Al,B,Er)0.75(Al,B,Er)0.25(Va)1, respectively. A self-consistent thermodynamic description of the Al-B-Er system was obtained.