Nanoscale structural evolution accompanying mechanical degradation in an annealed AlFeNiCoCrCu complex-concentrated alloy

Prolonged annealing of an AlFeNiCoCrCu complex-concentrated alloy produces pronounced mechanical degradation and nanoscale structural evolution despite limited changes in its bulk phase constitution and dendritic/lamellar morphology. This work combines multiscale characterization with comparative atomistic modeling to identify the nanoscale structural variables associated with this annealing response. During prolonged annealing, the tensile strength and ductility decrease markedly, whereas the overall dendritic/interdendritic and lamellar structure is retained without systematic lamellar coarsening. The structural evolution is characterized by enhanced B2-type ordering within the FeCr-rich BCC-type regions, a marked reduction in the detectable population of Cu-rich nanoscale precipitates, and redistribution of local lattice strain. Correspondingly, the deformation substructure evolves from broadly distributed dislocation networks in the as-cast state to fewer and more spatially confined dislocations after prolonged annealing. Comparative atomistic models show that enhanced B2-type ordering within the FeCr-rich BCC-type regions is associated with lower generated dislocation densities, while the four idealized configurations exhibit distinct atomic-strain and dislocation-distribution patterns. These results highlight the need to consider nanoscale structural evolution and deformation behavior alongside bulk phase constitution and morphology when evaluating long-term mechanical reliability. Prolonged annealing of the AlFeNiCoCrCu complex-concentrated alloy causes mechanical degradation and nanoscale structural evolution. This work combines multiscale characterization with atomistic modeling to identify the nanoscale structural variables associated with this