Fig. 1 a Schematic diagrams of SLM process [55]. SEM images of the pre-alloyed HEA powders b and particle size distribution of the powders c [51]. d The small turbine blade of Al0.5CoCrFeNi HEA manufactured by SLM [53]. e The complex fan blade of AlCoCrFeNi2.1 EHEA produced via SLM [54]

Fig. 2 a Schematic diagram of SEBM process [56]. b SEM image of AlCoCuFeNi HEA powders [35]. Cylinder specimens c and bulk specimens d prepared by SEBM [58,59]

Fig. 3 a Schematic diagram of DED process [60]. b SEM image showing the AlCoCrFeNiTi0.5 powders and c powder size distribution map [66]. d The bulk HEA produced by DED [63]. e LENS-produced large-sized AlCoCrFeNi2.1 sample [64]. f A thin wall deposited by DED [65]

Fig. 4 a XRD profile of the LENS-ed AlxCuCrFeNi2 [62]. b XRD spectra of cast specimen and SEBM specimens. c Phase diagram of AlxCrCoFeNi calculated with Thermo-calc using TCFE6 database [58]

Fig. 5 Inverse pole figure (IPF) maps of the SEBM-ed AlCoCrFeNi specimens parallel to the building direction: a top section; b bottom section [59]. c IPF map of DED-ed AlCoCrFeNi along building direction [75]. Comparison of IPF maps for AlCoCrFeNi specimens: d SLM-ed and e metallic glass refined [76]. IPF maps of SLM-ed AlCoCrCuFeNi with different VEDs: f 52.08 J/mm3; g 69.40 J/mm3; h 78.10 J/mm3; i 83.3 J/mm3 [78]

Fig. 6 SEM-BSE images of the as-cast a and SEBM-ed AlCoCrFeNi b; the magnified images of a and b are shown in (a1) and (b1) [59]. Lamellar structure c and cellular structure d of SLM-ed AlCrCuFeNi3; (c1) and (d1) represent the corresponding phase maps [70]. e SEM image of the SLM-ed FeCoCrNi; f, g TEM images showing cellular substructure and columnar substructure [79]

Fig. 7 a Gas porosity defects in the gas-atomized powder observed by SEM and b magnification image of a; c density of SLM-ed AlCoCrCuFeNi HEA varies with VEDs and metallographs: d 52.08 J/mm3; e 69.4 J/mm3; f 78.1 J/mm3; g 83.3 J/mm3 [78]

Fig. 8 a Microcomputed tomography (µ-CT) images with corresponding cross-sectional OM image for SLM-ed sample. The chimney-like cracks appeared within the sample are circled in a red dashed line. b SEM image showing the atom probe tomography (APT) specimen was acquired on the periphery of a hot crack. c SEM image showing an APT specimen tip with a dimension of ~ 50 nm. d APT reconstruction volumes showing atom distribution of the 4 constituting elements (Co, Cr, Fe and Ni). e A generic schematic illustration of the hot cracking mechanism in AM process. f Hot tearing propensity with respect to their grain size and typical depression pressures for the chosen SLM-built alloys [90]

Fig. 9 a Initial orientation of as-deposited alloy using EBSD-IPF map with schematic representation of tensile and compressive specimens with respect to loading directions. b True stress-strain curve under tensile and compressive loading. TEM images showing c deformation twins in a sample compressed to a strain of 1.0 and d deformed structure testes in tension to true failure strain of 0.38 [92]

Fig. 10 Back-scattered images of AlCoCrFeNi specimens obtained at the cross section perpendicular to the build direction with various heat treatment conditions: a-c for as-deposited, aged at 800 ℃-168 h, 1000 ℃-168 h, respectively. (a1), (b1) and (c1) are higher magnification corresponding to a, b and c. d EDS map of AlCoCrFeNi aged at 1000 ℃ for 168 h [37]. Kernel average misorientation (KAM) maps of (e1) as-printed FeCoCrNi sample and samples after 2 h of annealing at (e2) 973 K, (e3) 1173 K, and (e4) 1573 K (insets: misorientation statistics). Twinning distribution of (f1) as-printed FeCoCrNi sample and samples after 2 h of annealing at (f2) 973 K, (f3) 1173 K, and (f4) 1573 K (insets: recrystallization distribution maps) [79]

Fig. 11 SEM micrographs of DLF-ed a Al0.3, b Al0.6 and c Al0.85 HEAs. The micrographs of the DLF/HIP HEAs at the same magnification were compared in d, e and f, respectively. The corresponding EBSD-IPF maps were shown in g, h and i [98]