Fig. 3.

Deformation micro-mechanisms in the hierarchical DPHL HEA with the increasing tensile strain. a STEM images showing the dislocation-substructure evolution. The early stage of deformation (ɛ = 4%) leads to more obvious dislocations in soft FCC grains than hard P2 (the intergranular B2 grains) and B2 grains near phase interfaces. At medium strains (ɛ = 13%), there exhibit significantly-increased dislocations in FCC grains and P2. The piling-up of GNDs is marked by dashed red lines in FCC grains. b, c STEM images of the microstructure stretched to fracture (ɛ = 21%). The dual-phase lamellae and P2 (indicated by yellow dashed lines and red arrows, respectively) show apparent dislocations. b Microcrack propagation stays confined/blunted by neighboring lamellae. c The dashed blue arrows point out different deformation directions, and even some FCC grains deform along two directions. d Schematic illustration of the dislocation evolution during deformation. Stage I: elastic deformation; Stage II: elastic-plastic deformation; Stage III: plastic deformation. ⊥, dislocation. Note that stage I in d is not the schematic illustration of ɛ = 4% in a. Scale bars, 200 nm in a, b and 1 µm in c