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

Abstract

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.