*3.1. Grain Size and Grain Orientation*

The EBSD images of the SR-, ST-, and HIP-treated specimens are shown in Figure 3. In the vertical section, the SR specimen contained grains oriented parallel to the build direction (Figure 3a). A continuous grain growth (i.e., epitaxial growth across the melt pool boundaries) during the LPBF process affected the grain orientation and the length of growing grains. In fact, the grains had an average length greater than 120 μm (three layer thicknesses). Equiaxed grains with an average size of 20 μm were observed in the horizontal section. After the ST and HIP treatments, the columnar grain structure of the SR alloy morphed into equiaxed grain structures (Figure 3b,c). After the ST, the grain size varied from 1 to 80 μm in size, while after the HIP, it varied between 10 and 300 μm. Note that the average grain size (~45 μm) of the HIP alloy was twice as large as that of the ST alloy (~20 μm). The equiaxed grains with annealing twins corresponded to a low-stacking fault-free energy fcc matrix. For the SR specimens, the dominant grain texture in the build direction corresponded to the [001] direction (red area in Figure 3a), which transformed to a random texture after the ST and HIP treatments (Figure 3b,c).

**Figure 3.** Electron backscatter diffraction (EBSD) images of the (**a**) stress-relief annealing (SR)-, (**b**) solution-treated (ST)-, and (**c**) hot isostatic pressing (HIP)-treated alloys; white arrow shows the build direction. (Color crystal orientation code is inserted.)
