Coarsening mechanism of T1 precipitation and calculation of T1/Al interface properties in 2198 Al-Cu-Li alloys: Experimental and DFT studies

This paper aims to reveal the thickening mechanism of multiple different types of T1 precipitation through experimental characterization by HAADF-STEM. Meanwhile, a detailed theoretical analysis of the properties of the T1(0001)/Al(111) interface has been carried out for the first time by applying the first-principles. The experimental results show that the crystal orientation relationships of the T1/Al interface are (0001)T1/{111}Al and [1010]T1/[110]Al. Firstly, two T1 phase thickening mechanisms are proposed. (i) The Cu-rich layer in the T1 phase is used as a substrate for the coarsening of the precipitation. (ii) The Al-Cu transition layer is used as a starting point for precipitation thickening. Secondly, the first-principles were applied to calculate the properties of the T1/Al interface in terms of adhesion work, interfacial energy and electronic structure. The results of the interfacial energy and adhesion work calculations demonstrate that the AlLi-terminated T1/Al interface is more stable. The analysis of the electronic characteristics of the interface shows that the AlLi-terminated interface is more stable and that strong Al-Al and weak Al-Li covalent bonds are formed at the T1/Al interface. Meantime, the electronic structure features are in complete agreement with the findings of the energy calculations.

Automated summary

This paper reveals the mechanisms of thickening for different types of T1 precipitation and the properties of the T1/Al interface through experimental and theoretical analysis. The experimental results show the crystal orientation relationships of the T1/Al interface. The first-principles calculations demonstrate that the AlLi-terminated T1/Al interface is more stable and exhibits unique chemical bonds.