ASSESSMENT OF THERMODYNAMIC PROPERTIES OF ALLOYS BY COMBINING THE EMBEDDED-ATOM AND THE QUASI-HARMONIC METHODS

The Embedded Atom Method (EAM) was combined with the quasiharmonic app roximation to determine the enthalpies and the free energies of mixing for a number of binary f.c.c. and b.c.c. metallic solid solutions. In each case, the EAM potential functions were determined using only the data for the constituent elements. It was found that when two f.c.c. elements are mixed to form an f.c.c. solid solution, the combination o f the EAM and the quasiharmonic methods gives a fairly good assessment of the thermodynamic properties of the solid solution. On the other h and, when an f.c.c metal and an b.c.c. metal are combined to produce e ither an f.c.c. or an b.c.c solid solution, the same approach fails to predict correctly the enthalpies and the free energies of the mixing. However, at least over a composition range reasonably good prediction s can still be obtained for the relative thermodynamic stability of th e f.c.c, and the b.c.c, structures which is of interest in the analysi s of diffusionless phase transformations, such as the martensitic tran sformation.