## 3 Results  
The results of the experimental campaign are reported in Figures 6-13. Figure 6 shows the surface macrographies of specimens before and after BF. The untreated surfaces are characterized by several defects, as expected. The horizontal one (\(0^{\circ}\) orientation) shows the effect of laser processing, and the tracks are visible. The \(45^{\circ}\) specimen is affected by the so-called balling phenomenon, which is more evident in \(90^{\circ}\) one. As the BF is performed at 30 rpm, these defects are deeply reduced: The laser tracks disappeared, and only some local asperities are present. At 42 rpm, the BF action is more effective, and almost all the defects are removed. Figure 5: Example of cross-section measurement, using the 3D structured light scanner: (a) acquired and reconstructed 3D shape; (b) cross-sections evaluated through a MATLAB routine. Figure 6: Macrographies before and after barrel finishing (BF). This morphological investigation can be quantitatively analyzed by roughness measurements. Before the conditioning, the expected profiles are observed. An almost periodical behavior is present for 0\({}^{\circ}\) orientation: Since the laser is orthogonally consolidating the area, no staircase effect and reduced balling phenomenon occur; as a consequence, the hatching laser tracks are prominent (Figure 7a). In this case, the average roughness Ra is low and equal to 8.557 \(\upmu\)m, and the total roughness, namely the distance between the maximum peak and the deepest valley, is 40 \(\upmu\)m. At 45\({}^{\circ}\) orientation (Figure 7b), the staircase and balling phenomenon affect the surface, which shows a greater Ra and Rt. For 90\({}^{\circ}\) orientation, the defects are pronounced with a Rt about twice the 0\({}^{\circ}\) case and an Ra equal to 12.903 \(\upmu\)m (Figure 7c). The conditioning via BF at 30 rpm markedly reduces the previous defects, providing surfaces with less than 1 \(\upmu\)m Ra: Only some scratches of 5 \(\upmu\)m maximum height are present in 0\({}^{\circ}\) orientation, as shown in Figure 7d; deeper valleys, 10 \(\upmu\)m height, are present in 45\({}^{\circ}\) and 90\({}^{\circ}\) surfaces (Figure 7e and f). When BF at 42 rpm is adopted, the previous scratches are almost removed and a Ra of about 0.5 \(\upmu\)m is reached (Figure 7g-i). It is well evident that BF is able to delete the micro-geometrical feature SLM technique applied to the fabricated surfaces. Figure 7: Roughness profiles for investigated specimen orientations before BF conditioning (**a,b,c**) after BF at 30 rpm (**d,e,f**) and after 42 rpm (**g,h,i**). Figure 8: Three-dimensional maps of untreated \(0^{\circ}\) (**a**) and \(90^{\circ}\) (**b**) specimen surfaces, 30 rpm (**c**) and 42 rpm (**d**) BF-conditioned surfaces. Figure 9: Force–displacement curves for (**a**) the barrel-finished samples and (**b**) the heat-treated samples. Figure 11: (**a**) Yield stress, ultimate tensile strength and elongation at break of the barrel-finished samples; (**b**) same quantities averaged over the BF speeds. Figure 12: (**a**) Yield stress, ultimate tensile strength and elongation at break for the heat-treated samples; (**b**) same quantities averaged over the postprocessing temperature. Figure 10: Stress–strain curves for (**a**) the barrel-finished samples and (**b**) the heat-treated samples. An overall analysis of surface was carried out by 3D maps. The unconditioned 0\({}^{\circ}\) surface is almost periodical but some subsidence zones present (in dark green in Figure 8a). A BF treatment at 30 rpm is a delicate operation which is able to delete the previous behavior but some little zones are characterized by local valleys, probably reminiscence of initial deepest subsidence (Figure 8c). Conversely the chaotic and rough surface related to 90\({}^{\circ}\) orientation shown in Figure 8b is completely flattened by a 42 rpm BF action which removed any defects present at the beginning (Figure 8d).