Fig. 1 a-c SEM images and d XRD patterns of the samples sintered at different temperatures

Fig. 2 a1-a3 IPF maps of the samples sintered at 590, 620, and 640 °C, respectively; b1-b3 grain size distribution corresponding to a1, a2, and a3, respectively; b4 the average grain size as a function of sintering temperature

Fig. 3 Grain boundaries character distribution of the samples sintered at a 590, b 620, and c 640 °C, LAGB, HAGB, and TB are represented by lime green line, black line, and pink line, respectively; d the comparison of the fraction of LAGB, HAGB, and TB in the samples

Fig. 4 TEM images of the sample sintered at 590 °C: a a typical bright-field TEM image; b a higher magnification bright-field TEM image showing the nanoparticles and dislocations marked with white arrows and blue arrows, respectively

Fig. 5 TEM images of the sample sintered at 640 °C: a a typical bright-field TEM image; b the electron diffraction pattern corresponding to the area in a marked by white circle; c a typical Al2O3 particle distributed in Al matrix; d the interface between Al2O3 particle and Al matrix, the inset is FFT for the area marked with white square

Fig. 6 TEM images of the sample sintered at 640 °C: a TEM image of a typical twin at grain corner, the TBs are indicated by green arrows, the inset shows the entire grain containing numerous dislocations; b an enlarged view of the twin in a, the SFs are marked with ellipses; c the electron diffraction pattern corresponding to the region marked with black square in b; d the high resolution TEM images of TB and SFs on different {111} planes in b; e IFFT image of the region marked with white square in b, the dislocations are indicated by ⊥; f TEM image of another typical twin crossing the entire grain, the TB and dislocations are marked with green arrow and blue arrows, respectively; g the electron diffraction pattern corresponding to the twinned grain in f

Fig. 7 Distributions of recrystallized, substructured and deformed grains in the samples sintered at a 590, b 620, and c 640 °C. The LAGBs, HAGBs, and TBs are represented by lime green line, black line, and pink line, respectively; d comparison of the fraction of the recrystallized, substructured and deformed grains in samples; e1-e3 an enlarged view of the sample sintered at 640 °C, the twins formed in substructured regions are indicated by black arrows, and the twins formed in recrystallized regions are indicated by white arrows

Fig. 8 a Engineering and b true stress-strain curves of the samples sintered at different temperatures

Fig. 9 Contribution of strengthening mechanisms to the yield strength increment of the samples sintered at different temperatures