Formation of AlSi and AlGe solid solutions and equation of state

Abstract

The pressure effect on the solid solubility of the AlSi and AlGe systems is studied using the electronic theory based on pseudo- potentials and the virtual crystal approximation for the disordered alloy. The atomic concentration x-dependence of the equilibrium volume satisfying energy-minimum condition for Al 1− x Si x and Al 1− x Ge x solid solutions with fcc lattice is in good agreement with an available experimental data. The equation of state of these alloy systems is presented quantitatively and the compression effect on the heat of solution is investigated. The heat of solution ΔE S ( x, P) for Al 1− x Si x and Al 1− x Ge x solid solutions under pressure P is small for the Al-rich region and decreases as the crystal is compressed. Consequently, using the Helmholtz free energy of formation under pressure F' s ( x, P, T), we predict the extended solid solutions under pressure in AlSi and AlGe alloy system is consistent with the experimental tendency.