new Mg–Sm–Ce–Mn-based alloying system with a large miscibility gap was uncovered

and multi-solute co-segregations at high-angular grain boundaries (HAGBs)

dislocations and low-angular grain boundaries (LAGBs) are obtained after the proper extrusion process. During following long-term thermal exposure

the solute along HAGBs gradually evolves into nano-precipitates

while the precipitation process along LAGBs is obviously suppressed due to the intrinsically low-energy character

and numerous G. P. zones and γ” phases are formed in deformed regions

which always keep the limited size and reticular distribution. Consequently

the bimodal-grain structure is thermally stable

and the excellent high-temperature strength can be well maintained.