Fig. 1. Schematic diagram showing the cyclic pre-deformation processing of the as-prepared equiatomic CrMnFeCoNi alloy.

Fig. 2. OM micrographs of (a) the as-annealed and (b) the cyclically pre-deformed CrMnFeCoNi alloy prior to room-temperature tensile testing. CD: cyclically deformed direction (CD), ND: normal direction (ND).

Fig. 3. TEM images showing the morphologies of the CrMnFeCoNi alloy at (a) the as-annealed and (b) the cyclically pre-deformed states.

Fig. 4. Chemical analysis by TEM-EDS. Low-magnification HAADF-TEM image and EDS elemental mapping of the as-annealed (a) and the cyclically pre-deformed specimens (b); (c) and (d) represent the line profiles of the atomic fraction of individual elements taken from the respective EDS maps in (a) and (b), respectively.

Fig. 5. TEM imaging and element distribution mapping in the as-annealed CrMnFeCoNi alloy. (a) HAADF image of atomic structure, taken with the [110] zone axis, and the corresponding EDS maps for individual elements of Cr, Mn, Fe, Co, and Ni. (b) Line profiles of the atomic fraction of individual elements taken from the respective EDS maps in (a). each line profile represents the distribution of an element in a (11-1) plane projected along the [110] beam direction. (c) Plots of pair correlation function S(r) of individual elements as a function of concentration wavelength r; S(r) is shifted by avg(C)2, where avg(C) is the average atomic fraction of the corresponding element. (d) Magnification of local regions in (a) (all with the same scale), showing small groups of neighboring atomic columns with similar brightness. (e) Comparison of the local concentration distribution of individual elements for the same region, indicating that the Cr-poor region is filled with a mixture of the other four elements.

Fig. 6. TEM imaging and element distribution mapping in the cyclically pre-deformed CrMnFeCoNi alloy. (a), HAADF image of atomic structure, taken with the [110] zone axis, and the corresponding EDS maps for individual elements. (b), Line profiles of the atomic fraction of individual elements taken from the respective EDS maps in (a). each line profile represents the distribution of an element in a (11-1) plane projected along the [110] beam direction. (c), Plots of pair correlation function S(r) of individual elements as a function of concentration wavelength r. S(r) is shifted by avg(C)2, where avg(C) denotes the average atomic fraction of the corresponding element. (d) Magnification of local regions in (a) (all to the same scale), indicating small groups of neighboring atomic columns with similar brightness. (e) Comparison of the local concentration distribution of individual elements for the same region, indicating that the Fe-poor region is more inclined to be filled by Co and Ni.

Fig. 7. (a) Engineering stress-strain curves of the CrMnFeCoNi alloy subjected to annealing and cyclic deformation, and the magnified section of the tensile curve for the cyclically pre-deformed specimen showing the yield plateau. (b) Summary of the failure elongation versus yield strength for the CrMnFeCoNi alloy undergone the current cyclic deformation and other processing methods [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44]. HR/CR+AN: Hot/cold deformation + annealing, AC: As-cast, SLM: Selective laser melting, HPT: High-pressure torsion, MA: Mechanical alloying, SPS: Spark plasma sintering, LENS™: The laser engineered net shaping. CG: coarse-grained, FC: fine-grained, UFG/NG: ultrafine-grained/nano-grained.

Fig. 8. TEM of the cyclically pre-deformed CrMnFeCoNi alloy. (a) The enhanced pinning effect on dislocations, (b) multiple dislocation configurations.