## 5 Conclusions  
The present paper aimed to evaluate the effects induced by different heat treatments (704 \({}^{\circ}\)C/120\({}^{\prime}\), 740 \({}^{\circ}\)C/130\({}^{\prime}\) and 1050 \({}^{\circ}\)C/60\({}^{\prime}\)), performed using an industrial furnace, on Ti6 Al4V-ELI samples manufactured via Laser Powder-Bed Fusion in different build orientations. In addition, the effects of the sandblasting process were also analyzed. The main conclusions can be summarized as follows:  
1. The microstructure of samples heat-treated at 704 and 740 \({}^{\circ}\)C is formed by columnar \(\beta\)-grains containing \(\alpha^{\prime}\)-martensite and \(\alpha\) (primary, secondary and tertiary) + \(\beta\) phases. Some samples also showed \(\alpha_{2}\)-Ti\({}_{3}\)Al and TiAl\({}_{3}\) precipitates that are probably formed during the L-PBF process. These can cause the anisotropic behavior of the mechanical performance related to samples grown along the same direction.
2. The samples heat-treated at 704 \({}^{\circ}\)C show more anisotropic mechanical properties than the same tensile samples heat-treated at 740 \({}^{\circ}\)C. On the other hand, both satisfy ASTM F2924 and ASTM F3001 standard specifications. The increase in \(\alpha\)-alth's thickness from 538 \(\pm\) 66 to 704 \(\pm\) 11 \(\upmu\)m only influences the HV\({}_{0.1}\) microhardness measurements, but apparently has no effect on yield, ultimate tensile strength or elongation.
3. The microstructure of samples heat-treated at 1050 \({}^{\circ}\)C varies in relation to the sample's thickness. As a matter of fact, the tensile samples (6 mm) are formed by \(\alpha\)-laths in a basketweave or Widmanstatten structure and small \(\alpha\)-colonies within recrystallized equiaxed \(\beta\)-grains. Instead, bars (10 mm) are formed by wider \(\alpha\)-colonies in a basketweave or Widmanstatten structure and globular \(\alpha\)-phase within the same equiaxed \(\beta\)-grains. Moreover, in both cases, an \(\alpha\)-case layer of about 100 \(\div\) 150 \(\upmu\)m is formed on the surface.  
Figure 16: XRD patterns of two 90\({}^{\circ}\)z-samples manufactured in the same batch and heat-treated at 740 \({}^{\circ}\)C/130\({}^{\prime}\). The black XRD pattern (1) is correlated to the red pattern (2) that is the same shown in Figure 8a.  
The samples heat-treated at 1050 \({}^{\circ}\)C show mechanical properties that satisfy only the ASTM F3001 standard specification. Despite the decrease in UTS and YS by about 10% and 14%, respectively, the elongation values do not show a significant increase with respect to the samples heat-treated at 704 and 740 \({}^{\circ}\)C, probably due to the presence of the \(\alpha\)-case layer.  
The sandblasting process does not induce effects on the mechanical properties, but increases the plastic strain in the near-surface area. The obtained surface roughness of the sandblasted tensile sample (12 \(\div\) 16 \(\mu\)m) does not satisfy the requirements for aerospace applications.  
Conceptualization, E.C. and E.G.; methodology, E.C. and E.G.; software, E.G. and G.B.; validation, E.C.; formal analysis, E.G.; investigation, E.G. and G.B.; resources, E.C.; data curation, E.C. and E.G.; writing--original draft preparation, E.G.; writing--review and editing, E.C., E.G. and G.B.; supervision, E.C.; project administration, E.C. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
All data are available within the manuscript.  
The authors would like to thank BEAMIT ([[https://www.beam-it.eu/](https://www.beam-it.eu/)]([https://www.beam-it.eu/](https://www.beam-it.eu/)), accessed on 20 April 2022) for supplying the material.  
The authors declare no conflict of interest.