First-principles investigation of Al1-Li solid solutions: Elastic properties, electronic structures and thermodynamic properties

Al-Li alloys are widely used in automotive, aviation and aerospace industries because of their beneficial properties, such as high modulus, low density and high specific stiffness. However, their application is limited by their relatively low stiffness. Therefore, it is important to improve the elastic properties of Al-based alloys to increase their competitiveness. The inclusion of Li in these alloys significantly enhances their modulus. The modulus of Al-Li alloys typically consists of two parts: the Al-Li solid solutions and intermetallic compounds. Compared to the extensive research conducted on intermetallic compounds with fixed composition, there has been relatively less investigation into the elastic properties of the Al-Li solid solutions, especially with the composition and temperature variation. In this work, reliable crystal structure of Al1-xLix (x = 0, 0.03125, 0.0625, 0.09375, 0.125) solid solutions are generated by special quasi-random structure (SQS) and their elastic modulus with the composition range of 0–12.5 at% Li at 0–900 K are investigated by first-principles calculations. The calculated elastic modulus by VASP-SQS method agree relatively well with the available data in literature. The variation both in Li content and temperature have significant effects on the elastic properties of Al1-xLix solid solutions. While differences in atomic size and conventional cell volume contribute to this phenomenon, they are not the primary influencing factors. The local charge density increases the interatomic interaction force of Al1-xLix solid solutions, and ultimately result in an increase in elastic modulus. It is verified by VASP-SQS method that the Young's modulus of Al1-xLix solid solutions is mainly influenced by their electronic structures.