Fig. 1. SEM-BSE images of the C-doped iHEA. (a) Annealed at 650 °C for 1 h; (b) Annealed at 800 °C for 1 h; (c) Annealed at 900 °C for 1 h.

Fig. 2. Microstructures and phase analysis of the C-doped iHEA. (a-c) EBSD phase map for and (d) XRD patterns of the specimens annealed at 650, 800 and 900 °C for 1 h.

Fig. 3. Step-diagram of the C-doped iHEA calculated by Thermo-Calc software.

Fig. 4. HAADF-STEM images of the C-doped iHEA annealed at 800 °C (a, b) and 900 °C (c, d) for 1 h. Inset of (c) is the SAED pattern of precipitates.

Fig. 5. Mechanical behavior of the C-doped iHEA at room temperature. (a) Engineering strain-stress curves; (b) Strain hardening rate curves.

Fig. 6. XRD patterns of the specimens interrupted at different strain levels in the C-doped iHEA.

Fig. 7. EBSD maps showing the microstructure evolution of the C-coped iHEA annealed at 800 °C at different strain levels (0, 2%, 20%, 35%) during tensile deformation. (a1-d1) Phase figures; (a2-d2) The kernel average misorientation (KAM) diagram; (a3-d3) The inverse pole figure (IPF); (d4, d5) The inverse pole figure and pole figure showing the orientation relationship between HCP and FCC phase. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

Fig. 8. Evolution of (a) phase fraction and (b) boundary fractions of the C-coped iHEA obtained by EBSD analysis at different strain levels; EBSD image quality maps with grain boundary misorientation distribution of FCC (c) and HCP (d) phase formed in the specimen with 35% tensile strain. (For interpretation of the references to color in this figure, the reader is referred to the web version of this article.)

Fig. 9. ECC images showing microstructural evolution of the C-doped iHEA with increasing strain levels: (a) 2%; (b) 20%; (c) 35%.

Fig. 10. TEM images of the C-doped iHEA annealed at 800 °C interrupted at 2% strain during the tensile deformation. (a, b) BF images of the precipitates, dislocations and SFs; (c) dislocation cells in grains with zone axis of [0.11¯] (d, e) DF images by the two beam diffraction in different g vectors; (f, g) BF and DF images showing the dislocations and stacking faults. (DS: dislocation; SF: stacking fault).

Fig. 11. Typical TEM images of the C-coped iHEA annealed at 800 °C interrupted at 20% strain during the tensile deformation. (a) BF images of thin plates; (b) SAED patterns of the region in yellow boxes in Fig.(a); (c) DF image of HCP phase using [$11\bar{2}0$]HCPreflection. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Fig. 12. Typical TEM images of the C-coped iHEA annealed at 800 °C interrupted at 35% strain during the tensile deformation. (a) BF images; (b) SAED pattern; (c, d) DF images showing the nano-twin and HCP phase; (e) HRTEM image showing the FCC and HCP phases; (f) HETEM image of deformation twins.