Fig. 1 a-h SEM images illustrating the morphology evolution of precipitate for the Ni44Co22Cr22Al6Nb6 MPEA after different aging time from 0 to 200 h at 800 °C

Fig. 2 a Selected area electron diffraction pattern (SADP) and corresponding representative DF-TEM image of the Ni44Co22Cr22Al6Nb6 MPEA aged at 800 °C for 10 h. b Schematic diagram of the nanoparticles growth-split behavior evolution process

Fig. 3 a Tensile engineering stress-strain curve of Ni44Co22Cr22Al6Nb6 MPEA after isothermal aging treatment at 800 °C for different time at room temperature. b Vickers hardness and volume percentage of L12 particles after isothermal aging at 800 °C for different time

Fig. 4 High-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and corresponding elemental maps of L12 nanoparticles in the Ni44Co22Cr22Al6Nb6 MPEA aged at 800 °C for 10 h a, 48 h b

Fig. 5 Changing trend of chemical composition (at%) of FCC-matrix a, nanoparticles b during 800 °C isothermal aging. Composition distribution of L12 nanoparticles from 700 to 1050 °C c

Fig. 6 Plot of average particles size (a for r2 and b for r3) versus aging time for the Ni44Co22Cr22Al6Nb6 MPEA aged at 800 °C, the red line corresponds to the result of linear fitting

Fig. 7 a Plot of average precipitate size (r3(t)) versus aging time (t) for the Ni44Co22Cr22Al6Nb6 MPEA aged at temperatures between 750 and 850 °C. Solid lines are linear fits of the experimental data (green line: 750 °C, blue line: 800 °C, red line: 850 °C). b Arrhenius plot of the coarsening rate constant (ln (KT)) as a function of the reciprocal aging temperature (1/T)

Fig. 8 Coarsening rates for the Ni44Co22Cr22Al6Nb6 MPEA and a number of Ni-based alloys as a function of aging temperature [18,31,34,35,42,43]