## 3 Results
### Microstructure and Surface Roughness
Figure 6c,d highlight the \(\beta\)-grain boundary formed by the \(\alpha_{\rm GB}\) (Grain Boundary) phase  
Figure 5: SEM micrographs of the 0\({}^{\circ}\)XY-sample (**a,b**) after 704 \({}^{\circ}\)C/120\({}^{\prime}\) and 90\({}^{\circ}\)Z-sample (**c,d**) after 740 \({}^{\circ}\)C/130\({}^{\prime}\). All images were acquired on the plane perpendicular to the build platform. Panel (**b**) illustrates the magnification (40 k\(\times\)) of the red square area in panel (**a**) (2 k\(\times\)), while panel (**d**) shows the magnification (40 k\(\times\)) of the yellow square area in panel (**c**) (2 k\(\times\)). Orange, green and light-blue dotted lines indicate primary, secondary and tertiary \(\alpha\)-laths. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Spectrum** & **Ti** & **Al** & **V** & **Fe** & **Phase** \\ \hline A & 91.6 & 7.2 & 1.2 & - & \(\alpha\) \\ B & 89.9 & 2.0 & 7.9 & 0.2 & \(\beta\) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Chemical composition (EDS) of spectra A and B in wt.%. due to \(\beta\to\alpha_{\text{GB}}\) transformation during the cooling, and from which the \(\alpha\)-colonies and \(\alpha\)-laths nucleate and grow. Tensile samples are formed by \(\alpha\)-laths and small \(\alpha\)-colonies that form a typical basketweave structure within the equiaxed \(\beta\)-grains (Figure 6a,c). On the other hand, the bar is formed by the Widmanstatten microstructure (Figure 6b,d) where wider \(\alpha\)-colonies are arranged in a basketweave structure. In addition, Figure 6b shows a granular/globular \(\alpha\)-phase, as also shown in [50]. [PERSON] et al. [51] suggested that different cooling rates induce these microstructural differences between the basketweave of \(\alpha\)-laths (<15 \({}^{\circ}\)C s\({}^{-1}\)) and the classical \"basketweave\" Widmanstatten morphology (<1.5 \({}^{\circ}\)C s\({}^{-1}\)). In the present work, the different cooling rates can be correlated to the different sample thicknesses between the tensile sample (6 mm) and the bar (10 mm) because both are simultaneously cooled with Argon gas for 1 h.  
Heat treatment at 1050 \({}^{\circ}\)C/60\({}^{\prime}\) also induces the formation of an \(\alpha\)-case surface layer with a thickness of 100 \(\div\) 150 \(\upmu\)m and hardness of (400 \(\pm\) 10) HV\({}_{0.1}\) in both the tensile sample (Figure 7a) and bar (Figure 7b). Similar results are shown in [49,52] for the cross-sections of the 45\({}^{\circ}\)-sample and 45\({}^{\circ}\)-bar. Figure 6: SEM micrographs of the 90\({}^{\circ}\)Z-sample (**a,c**) and the 90\({}^{\circ}\)Z-bar (**b,d**) acquired on the perpendicular (**a,b**) and parallel (**b,c**) planes to the build platform after 1050 \({}^{\circ}\)C/60\({}^{\prime}\). Figure 7(a) shows the results of the XRD analysis performed on the cross-sections of the heat-treated 90\({}^{\circ}\)Z-samples after the 704 \({}^{\circ}\)C/120\({}^{\prime}\), 740 \({}^{\circ}\)C/130\({}^{\prime}\) and 1050 \({}^{\circ}\)C/60\({}^{\prime}\) heat treatments. The different patterns show a reorientation and a possible recrystallization of the \(\alpha\)-phase after the 1050 \({}^{\circ}\)C/60\({}^{\prime}\), as previously reported and illustrated in Figures 5 and 6. Due to the exact overlap between the peaks of the \(\alpha\) and \(\alpha^{\prime}\) phases (as widely discussed in [12]), it is not possible to discern which of the two phases exists in each sample through XRD patterns alone. In this case, it is the microstructural observation in Figure 6 which confirms that the diffraction peaks of the samples heat-treated at 1050 \({}^{\circ}\)C belong to the \(\alpha\)-phase rather than the \(\alpha^{\prime}\)-martensite. Instead, the peaks appearing in the patterns of the 704 \({}^{\circ}\)C/120\({}^{\prime}\) and 740 \({}^{\circ}\)C/130\({}^{\prime}\) samples can be ascribed to the \(\alpha^{\prime}\)/\(\alpha\)-phases. The spectra also reveal peaks related to both the \(\alpha_{2}\)-Ti\({}_{3}\)Al and the TiAl\({}_{3}\) precipitates, which can be nucleated during the L-PBF process [12,24].