Fig. 1. (a) Porosity of EHEA samples fabricated at different process parameters; (b, c, d) optical graphs of EHEA samples to show the defect distributions with VED of 42 J/mm3, 63 J/mm3, 156 J/mm3, respectively.

Fig. 2 SEM microstructures of as-built EHEA with VED of 83 J/mm3 (laser power of 200 W) from cross plane (a1, a2, a3), and longitudinal plane (b1, b2, b3). shows that the lamellar colony is also very small, even along the building direction. We further analyzed the colony distribution with EBSD along the building direction, as shown in Fig. 3. Fig. 3(a) presents the inverse pole figure (IPF) map of FCC phase of the as-built EHEA sample with a VED of 83 J/mm3 (laser power of 200 W). The colonies are composed of equiaxed grains and columnar grains. There are a large number of equiaxed grains at the bottom of the molten pool while a large number of columnar grains in the molten pool, growing along the normal direction of the molten pool boundary. The distribution of lamellar colony size is shown in Fig. 3(b), and most lamellar colonies are in the size range of 2-6 μm.

Fig. 3. (a) IPF map of FCC phase of as-built EHEA with VED of 83 J/mm3 (laser power of 200 W); (b) distribution of lamellar colony size.

Fig. 4. (a) Tensile stress-strain curve at room temperature of EHEA samples with different VED and their as-cast counterparts [27,28]; (b) comparison of yield strength with different additive manufacturing processes of HEAs [13⇓⇓⇓⇓-18,37]; (c) tensile stress-strain curve of EHEA samples at different temperatures; (d) the variation of yield strength with temperature.