Formation mechanism of precipitate T1 in AlCuLi alloys

The formation mechanism of the plate-like strengthening T-1-phase in an Al-4.15Cu-1.15Li (wt.%) alloy has been revealed by means of advanced imaging techniques and the first-principle calculations. It is shown that T-1-precipitates nucleate directly from their own GP(T1) zones and grow thicker in two possible paths. One is regular by repeating T-1-cells, and the other is abnormal via T-1-variants. Structural model of GP(T1) zones has been suggested, and refined by image simulation. A possible structural evolution from GP(T1) zones to precipitate T-1 at atomic level is suggested and proved to be energetically reasonable. (C) 2014 Elsevier B.V. All rights reserved.