Formation mechanism of precipitate T1 in AlCuLi alloys

Abstract 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.