Atomic insights for elevated modulus in Al–Li alloys: synergies and design strategy.

Al–Li alloys, characterized by their lightweight and high strength, are essential structural materials in aerospace industry. Unraveling the atomic mechanisms that enhance the modulus of Al–Li alloys is key to developing the next-generation alloys. Utilizing first-principles methods, we systematically explored the influence of alloying elements on mechanical properties, ranging from binary solid solutions to Al3X precipitates and extending to ternary Al–Cu–Li alloys. Li significantly improves the modulus due to its size effects, low density, high solubility and easy precipitation. In binary A–Li solutions, the formation energy decreases (− 0.007 to 0.030 eV/atom) and the Young's modulus rises (80.2–88.4 GPa) as Li concentration increases (0–12.5 at.%). This increase in modulus is due to the compression of Al–Al bonds by Li atoms. The binary Al3Li phase, with reinforced bonds and lower density, exhibits a higher specific E modulus (49.2 GPa/g cm−3). In the ternary phase T1 (Al6Cu4Li3), the synergistic strengthening of both Al–Al and Cu-X (X = Al, Cu) bonds results in an elevated Young's modulus of 120.3 GPa, establishing it as a pivotal strengthening phase for the third-generation alloys. Subsequent theoretical calculations show superior elastic modulus in Al-X (X = Be, Si, Cr, Mn, Ni) solutions and Al3X (X = Sc, Ti, V, Zr) phases. Additionally, Zn can participate in the precipitation of the T1 phase, thereby enhancing the mechanical properties of the alloy. Gaining insights into atomic interactions and their influence on the modulus could inform the future design and optimization of multi-element Al–Li alloys. [ABSTRACT FROM AUTHOR]