Fig. 1 Hardness-time curve of samples aged at 120 °C

Fig. 2 Schematic of GPII zones in Al matrix: a 3D view of GPII zones lying on four equivalent {111} planes of Al matrix; b projection of GPII zones along [\bar{1}\bar{1}0]Al; c projection of GPII zones along [1\bar{1}\bar{2}]Al; d projection of GPII zones along [1\bar{1}1]Al

Fig. 3 HRTEM image a, corresponding FFT pattern b taking along [001]Al zone axis from sample aged at 120 °C for 1 h

Fig. 4 Typical HRTEM images of precipitates viewed along <110>Al zone axis in samples aged at 120 °C for 1 h a, 20 h b, 36 h c, 98 h d, 138 h e, 202 h f

Fig. 5 Typical HRTEM images of precipitates viewed along <112>Al zone axis in samples aged at 120 °C for 1 h a, 20 h b, 36 h c, 98 h d, 138 h e, 202 h f

Fig. 6 Typical HRTEM images of precipitates viewed along <111>Al zone axis in samples aged at 120 °C for 1 h a, 20 h b, 36 h c, 98 h d, 138 h e, 202 h f

Fig. 7 Distribution of the thickness versus diameter of precipitates in samples with different aging times, the red points correspond to the average thickness and diameter of precipitates

Fig. 8 Schematic of precipitate morphology changing along with aging time

Fig. 9 Comparison of the average aspect ratio-time curve with microhardness-time curve