###### Abstract  
T6 Al4V-ELI is the most-used lightweight alloy in the aerospace industrial sector thanks to its high mechanical strength and corrosion resistance. The present paper aims, firstly, to evaluate the effects induced by different heat treatments, which were performed above and below the \(\beta\)-transus temperature on T6 Al4V-ELI samples manufactured via Laser Powder-Bed Fusion in different orientations (XZ, XY, Z and 45\({}^{\circ}\)). The first set of tensile samples and bars were heat-treated at 1050 \({}^{\circ}\)C \(\times\) 1 h, while the second and third set were heat-treated at 704 \({}^{\circ}\)C \(\times\) 120\({}^{\prime}\) following the AMS2801 standard specification, and at 740 \({}^{\circ}\)C \(\times\) 130\({}^{\prime}\). These heat treatments were chosen to improve the as-built mechanical properties according to the ASTM F3001 and also ASTM F2924-14 standard specifications. Optical and SEM measurements reveal primary, secondary and tertiary \(\alpha\)-laths below the \(\beta\)-transus, while above this temperature, the microstructure varies in relation to the sample's thickness. Secondly, this work analyzed the results obtained after a sandblasting process, which was performed on half of all the available heat-treated tensile samples, through XRD and Vickers microhardness measurements. XRD analysis also highlighted the presence of \(\alpha_{2}\)-T\({}_{3}\)Al and TiAl\({}_{3}\) precipitates and the microstructural change in terms of the \(\alpha\)-phase. T6 Al4V-ELI; \(\alpha\)-colon  
researchers to obtain a 3D physical object through the successive addition of material (layer-by-layer) following a CAD (Computer-Aided Design) project, which is converted into an.stl file before the manufacturing process [12; 13]. Despite these advantages, [PERSON] et al. [1] affirmed that only 8.2% of the aerospace industry has adopted rapid-prototyping technology, while [PERSON] et al. [14] underlined that the certification and qualification of the Laser Powder-Bed Fusion (L-PBF) process, which is an AM technology, do not differ from the conventional manufacturing process in the aerospace field. L-PBF is a technology wherein a laser source scans and melts a powder bed that is deposited by a roller or recoater on the build platform [12]. To obtain a fully dense and high-quality sample, the following full melting criterion proposed by [PERSON] et al. [15] must be satisfied:  
\[\left(\frac{h}{W}\right)^{2}+\left(\frac{t}{D}\right)^{2}<1, \tag{1}\]  
where \(h\) (\(\upmu\)m) and \(t\) (\(\upmu\)m) are the hatch spacing and the layer thickness, respectively, while \(W\) (\(\upmu\)m) and \(D\) (\(\upmu\)m) are the width and the depth of the molten pool, respectively. In other words, the main process parameters that characterize the L-PBF process (laser power \(P\) (W), scanning speed \(v\) (mm/s), hatch spacing \(h\) (mm) and the layer thickness \(t\) (mm)), and influence the molten pool dimensions, need to be optimized [16; 17; 18]. Tie6 Al4V-ELI (Extra-Low Interstitial) is an \(\alpha+\beta\) alloy at room temperature that contains Al and V elements as \(\alpha\)- and \(\beta\)-stabilizers, respectively. In addition, the O, N and C atoms (in a small amount) stabilize the hcp (hexagonal closed packed) \(\alpha\)-phase, while Fe stabilizes the bcc (body-centered cubic) \(\beta\)-phase [12; 19; 20]. Due to the high cooling rate (up to \(10^{8}\) K/s, [12]) that characterizes the L-PBF technology, the as-built microstructure of the Ti6 Al4V-ELI sample is totally or partially formed by \(\alpha^{\prime}\)-martensite contained within columnar \(\beta\)-grains arranged parallel to the build direction [21; 22]. Generally, the UTS (Ultimate Tensile Strength) and YS (Yield Strength) values of as-built Ti6 Al4V-ELI samples reach values higher 1.1 and 1.0 GPa, respectively, which decrease when the temperature of the pre-heated build platform or the percentage of decomposed \(\alpha^{\prime}\)-martensite are increased [12; 23; 24; 25].