Theoretical Assessment of Thermodynamic Stability in Nanocrystalline Metallic Alloys

Thermal stability in nanocrystalline alloys has been extensively explored while using both experimental and theoretical approaches. From the theoretical point of view, the vast majority of the models proposed in the literature have been implicitly limited to immiscible or dilute systems and thus lack the necessary generality to make predictions for different alloying interactions and in the case of intermetallic compounds formation. In this work, a general theoretical description for the case of binary W-based alloys is presented. It is shown that a critical value Ω ∗ of the interaction energy in the grain boundary Ω ( g b ) exists, such that the condition Ω ( g b ) < Ω ∗ can be regarded as a criterion for thermodynamic stability assessment. A procedure for calculating the value of Ω ∗ for each specific alloy is illustrated. A preliminary qualitative comparison between the model predictions and properly selected experimental findings taken from the literature and related to the W-Cr system is also provided.