Critical Assessment of Activities of Structural Units in Fe–Al Binary Melts Based on the Atom and Molecule Coexistence Theory

A thermodynamic model for calculating the mass action concentrations Ni{N_i} of structural units in Fe–Al binary melts based on the atom–molecule coexistence theory, i. e., AMCT–Ni{N_i} model, has been developed and verified to be valid by comparing with reported activities aR,i{a_{{\rm{R, }}i}} of both Al and Fe relative to pure liquid as standard state in Fe–Al binary melts over a temperature range from 1823 to 1973 K (1550 to 1700 °C). Furthermore, Raoultian activity coefficients γi0\gamma _i^0 of both Al and Fe in the Fe-rich corner or Al-rich corner of Fe–Al binary melts as well as the standard molar Gibbs-free energy changes ΔsolGm,i(l)→[i][%i]=1.0Θ,%{\Delta _{{\rm{sol}}}}G_{{\rm{m, }}i{\rm{(l)}} \to {{{\rm{[}}i{\rm{]}}}_{{\rm{ [ \% }}i]{\rm{ = 1}}{\rm{. 0}}}}}^{\Theta {\rm{, \% }}} of dissolved Al or Fe for forming [% Al] or [% Fe] as 1.0 in Fe–Al binary melts have also been determined by the developed AMCT–Ni{N_i} model and verified to be accurate