Quantitative contribution of T 1 phase to the strength of Al-Cu-Li alloys

Aluminum–lithium alloys are widely used in aerospace due to their excellent comprehensive mechanical properties. The key to accelerate the composition design of aluminum–lithium alloys is to generate accurate precipitate structure models at the atomistic scale and quantify the effects of the secondary phase on the properties of the alloy. In this article, the development process of high-strength composition design of aluminum–lithium alloys is reviewed. The T 1 phase is considered to provide the highest strength in Al-Cu-Li alloys, and we further discuss the characteristics of the crystal structure, orientation relationship and morphology of the main strengthening phase. Additionally, this paper highlights the atomic structure model, microstructure parameters of T 1 phase and the precipitate–dislocation interaction relationships. Practically, the widely accepted atomic model of T 1 phase characterized with a corrugated Al-Li layer at the interface remains controversial. Moreover, the strengthening mechanism of Al-Li alloy is discussed. Based on the shearing and bypassing interaction mechanism between the T 1 precipitates and the matrix dislocations, some quantitative contribution models to the strength of Al-Cu-Li alloys are concluded. These models can effectively predict the variation of yield strength of Al-Cu-Li alloy, but the transition of T 1 phase from shearing mechanism to bypassing mechanism is not considered. However, the T 1 diameter threshold that activated this transition has not been completely determined, which need to be further studied by obtaining a wider range of T 1 microstructures. Graphical abstract