## 2 Materials and Methods  
Ti6 Al4V-ELI powder (Tekna, Sherbrooke, QC, Canada) was used to manufacture tensile samples and bars via Laser Powder-Bed Fusion technology. The powder used was characterized by a granulometry between 20 and 60 \(\upmu\)m and by an apparent density higher than 2.2 g/cm\({}^{3}\). Its chemical composition is reported in Table 1.  
Figure 1a shows a representative batch formed by 24 tensile samples and four bars directed along different directions, i.e., 0\({}^{\circ}\)\({}_{XZ}\) (blue), 0\({}^{\circ}\)\({}_{XY}\) (red), 45\({}^{\circ}\) (green) and 90\({}^{\circ}\)z (yellow), considering their major axis of symmetry. For a better understanding of the results, the tensile samples and bars were designated as reported in Table 2, where their dimensions are also listed. Three batches (Figure 1a) were manufactured through the SLM\({}^{\circ}\)280 (SLM solutions, Lubeck, Germany) machine following the skin-core scan strategy reported in Figure 1b, wherein the red dotted arrows indicate the laser directions. The laser scan tracks were parallel to each other and inclined by 56.5\({}^{\circ}\) with respect to the base of the external frame. Each layer (n) was rotated by 67\({}^{\circ}\) with respect to the previously solidified layer (n \(-\) 1). To manufacture all tensile samples and bars, the following process parameters were used: scanning speed of 1250 mm/s, laser power of 340 W, hatch spacing of 120 \(\upmu\)m and layer thickness of 60 \(\upmu\)m. The build platform was heated at 80 \({}^{\circ}\)C.  
All batches were heat-treated at three different temperatures below (704 and 740 \({}^{\circ}\)C) and above (1050 \({}^{\circ}\)C) the \(\beta\)-transus following the time-temperature curves reported in Figure 2. All treatments were performed in a vacuum furnace where the samples were cooled in argon gas for 1 h. The first batch was heat-treated at 704 \({}^{\circ}\)C for 2 h (704 \({}^{\circ}\)C/120\({}^{\prime}\)) following the ASM2801 standard specification, the second at 740 \({}^{\circ}\)C for 130\({}^{\prime}\) (740 \({}^{\circ}\)C/130\({}^{\prime}\)) and the third at 1050 \({}^{\circ}\)C for 60\({}^{\prime}\) (1050 \({}^{\circ}\)C/60\({}^{\prime}\)). The latter two heat treatments were performed to obtain a possible balance between strength and ductility to satisfy the ASTM F3001 standard specification. Focusing on the 740 \({}^{\circ}\)C/130\({}^{\prime}\), the cooling pathway (red curve) was \begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Elements** & **Ti** & **Al** & **V** & **C** & **Fe** & **O** & **N** & **H** & **Y** \\ \hline wt\% & Bal. & 6.47 & 4.06 & 0.01 & 0.21 & 0.09 & 0.01 & 0.001 & \textless{}0.001 \\ \hline \end{tabular}
\end{table} 
Table 1: Nominal chemical composition of Ti6 Al4V-ELI in wt.%. formed by the first step down to 520 \({}^{\circ}\)C in 90\({}^{\prime}\) and the second down to room temperature in argon gas. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Samples** & **Nomenclature** & **Color** & **Length** & **Width** & **Thickness** & **Cross-Section** \\  & \(0^{\circ}\)XZ-sample & Blue & & & & \\ Tensile & \(0^{\circ}\)Xr-sample & Red & \(10.0\,^{1}\) & \(6.0\pm 0.1\,^{1}\) & \(6.0\,^{1}\) & \(36\) \\ sample & \(45^{\circ}\)-sample & Green & Yellow & & & \\ \hline  & \(0^{\circ}\)Xr-bar & & & & & \\ Bars & \(0^{\circ}\)Xr-bar & Grey & \(25\) & \(15\) & \(15\) & \(225\) \\  & \(45^{\circ}\)-bar & & \(10\) & & & \\  & \(90^{\circ}\)Zr-bar & & & & & \\ \hline \hline \end{tabular} \({}^{1}\) Dimensions in agreement with the ES/ESM-16a standard specification.  
\end{table} 
Table 2: Nomenclature used in the present paper for all tensile samples and bars and their dimensions.