Phase stability by the artificial concentration wave method

Abstract

The effect of system fluctuations on the stability of alloy phases has been addressed by Khachaturyan.(1) A thermodynamic analysis of stability and transformations considers the dominance of either the thermal energy or interaction energy. At low temperatures, the interaction energy dominates. The phase state present may either be ordered, disordered, or some mixture of ordered and/or disordered. A redistribution of atoms over the crystal lattice sites accompanied by lattice rearrangements, further complicates the ordering or decomposition. The ordering and decomposition states may be interpreted by the loss of stability of a disordered solution with respect to static concentration waves (SCW). The loss of stability with respect to concentration waves characterized by asymptotically small wave vectors generates a, so called, spinodal miscibility. The loss of stability with respect to concentration waves characterized by finite wave vectors leads to the order-disorder transformation. The wave vector may be represented as 2π/λ, where λ represents the repeat period of the wave, i.e. the scale of heterogeneity.