Interface properties and nucleation thermodynamics of Al₂Cu precipitated phase by first-principles calculations

The Al₂Cu precipitated phase plays a critical role in governing the stability and mechanical properties of age-hardened Al-Cu alloys, which are widely used in the aerospace and automotive industries due to their high strength-to-weight ratio. However, the influence of alloying elements (e.g., Fe, Mn, Mg, Sc, and Zr) on the interfacial stability and nucleation behavior of Al₂Cu remains insufficiently understood, limiting the rational design of advanced Al-Cu alloys with optimized performance. This study addresses this gap by investigating how elemental segregation affects the structural stability and nucleation thermodynamics of Al₂Cu interfaces, offering insights into strategies for enhancing the mechanical properties and thermal stability of these alloys.

First-principles calculations based on density functional theory (DFT) were employed to evaluate the effects of segregated elements (Fe, Mn, Mg, Sc, and Zr) on the coherent strain energy and interface energy of Al/Al₂Cu interfaces. Electronic structure calculations were performed using the Vienna ab-initio simulation package (VASP), employing the Perdew-Burke-Ernzerhof (PBE) functional within the generalized gradient approximation (GGA) to account for exchange-correlation effects. To further elucidate the bonding mechanisms, interface stability was analyzed through detailed electronic structure investigations. Classical nucleation theory was applied to predict phase nucleation thermodynamics at aging temperatures, examining the formation of core-shell precipitates (Al₂Cu cores with solute-rich shells) as a function of precipitate size.