*3.3. Microstructure at the Edge of the Sample*

Structure at the sample´s edge consisted of ultrafine equiaxed grains (Figure 3c). The average grain size (D15) in this location was still higher than D3 and it became a bit smaller than that in the mid-radius area (Table 1).

Grain size distribution histograms for the transverse and longitudinal sections looked similar to those of the mid-radius area. The distributions were of log-normal type, with a maximum at 0.7 μm in both sections (Figure 4a,b). GB misorientation distributions show that the fractions of HABs in transverse and longitude sections were 61 and 79%, respectively. These values were much higher than the fractions of HABs in both the central and mid-radius areas (Table 1).
