Thermodynamic Assessment of the Al-Cr System by Combining the First-Principles and CALPHAD Methods

摘要

Thermodynamic assessment of the Al-Cr system has been carried out by incorporating first-principles calculations into the CALPHAD approach. A regular solution approximation was adopted to describe the Gibbs energy of the solution phases. The several phases appearing in the composition range between about 30 and 42 at.%Cr were treated as a single homogeneous y-phase, based on recent experimental results, and the Gibbs energy of the y-phase was represented using the four-sublattice model with the formula (Al,Cr)_8(Al,Cr)_8(Cr)_(12)(Al)_(24). The calculated results enable the reproduction of experimental results on both the phase equilibria and thermochemical properties. In addition, a B2 ordered bcc phase, which was suggested to form as an equilibrium phase in a previous X-ray diffraction study, is not likely to form in either the stable state or metastable state based on our first-principles calculations.