First-principles theory of coherent precipitation in size-mismatched alloys

A first-principles thermodynamic approach for studying coherent precipitation in size-mismatched alloys is presented. The approach takes into account both strain and interfacial energies, incorporates the effects of finite temperature, and can treat systems with length scales of ∼200Å, all with first-principles accuracy. The method is applied to coherent precipitation in Al-Cu and Al-Mg alloys, where the coherent precipitation sequence is experimentally well-studied, but still controversial. This theoretical approach should aid in understanding the strengthening mechanism underlying precipitation hardening in these materials.