Fig. 1 Typical microstructures of the studied alloy: a OM image and c SEM backscattered electron micrograph of the as-cast alloy; b OM image and d SEM backscattered electron micrograph of the as-quenched alloy; e partial enlarged SEM image; f the corresponding Al, Cu linear scan analysis of the as-cast alloy

Fig. 2 TEM micrographs of the sample subjected to NA treatment: a BF image showing the β′-Al3Zr phases with Ashby-Brown contrast feature; b DF image showing the β′/δ′ composite particles and ultra-fine δ′ phases

Fig. 3 TEM micrographs of the sample aged at 150 °C for 24 h: a BF image and the SAD pattern (inset) showing the T1 precipitates; b DF image showing the β′/δ′ composite particles and a large number of δ′ phases

Fig. 4 TEM micrographs of the sample aged at 160 °C for 24 h: a BF image and the SAD pattern (inset) showing the non-uniform precipitation of T1 and θ′ phases; b DF image showing the evenly distributed δ′ phases

Fig. 5 TEM a BF, b DF images of the sample aged at 170 °C for 24 h

Fig. 6 TEM micrographs of the sample aged at 180 °C for 24 h: a BF image and the SAD pattern (inset) showing the two kinds of T1 variants; b DF image

Fig. 7 TEM a BF, b DF images of the sample aged at 190 °C for 24 h showing the coarsened T1 and δ′ phases

Fig. 8 TEM micrographs of the sample subjected to TS treatment: a BF image and the SAD pattern (inset) showing the needle-like θ′ particles perpendicular to each other; b DF image and the partial enlarged drawing showing the none-spherical δ′ (marked with “B”) and the interaction between θ′ and δ′ precipitates (marked with “C”)

Fig. 9 Mechanical properties a and representative engineering stress-strain curves b of cast Al-3Li-2Cu-0.2Zr alloy after different ageing treatments

Fig. 10 Typical fracture morphologies of the samples subjected to a NA; b 160 °C × 24 h; c TS; d 190 °C × 24 h ageing treatments