## Materials and Methods  
Five different configurations of Al-alloys were considered, as summarized in Table 1, with the material, the processing, as well as post-processing conditions. Batches A-C were manufactured completely by the SLM process using Al4047 powder. Batch A represents the as-built condition, while stress-relief at 240 \({}^{\circ}\)C for 2 h was performed for batch B. Batch C was manufactured while the heating platform was heated continuously at 200 \({}^{\circ}\)C during the processing. These in-process and post-process heat treatments were performed to understand their influence on their part characteristics as a result of changing cooling conditions in the melt pool. For investigation of integrated manufacturing feasibility, batches D and E were manufactured while taking Al7020 wrought blocks as the base platform in the SLM processing, and Al4047 was generated over it. The influence of post-process stress-relief for hybrid specimens is investigated in batch E.  
Powder material for Al4047 feedstock that was produced by gas atomization was obtained from _SLM Solutions_ with a D10-D90 diameter range of 20-63 \(\upmu\)m. The morphology of this powder, as shown in Figure 1a, is dominated by spherical particles. The corresponding powder size distribution (PSD), as shown in Figure 1b, is relatively uniform around the mean equivalent diameter of 33 \(\upmu\)m with a \begin{table}
\begin{tabular}{c c c c} \hline
**Batch** & **Material** & **Base Plate Heating (BPH)** & **Stress-Relief (SR)** \\ \hline A & Al4047 & - & - \\ B & Al4047 & - & 240 \({}^{\circ}\)C \\ C & Al4047 & 200 \({}^{\circ}\)C & 240 \({}^{\circ}\)C \\ D & Hybrid & - & - \\ E & Hybrid & - & 240 \({}^{\circ}\)C \\ \hline \end{tabular}
\end{table} 
Table 1: Experimental plan for investigation of Al4047 and hybrid (Al7020+Al4047) specimens. standard deviation of 6 \(\upmu\)m. The non-existence of powder particles below 10 \(\upmu\)m makes this powder good in flowability. Another important aspect in powder-based AM process is the chemical composition of the used material. Table 2 shows this composition for the Al4047 alloy used in this study. The composition having a nominal value of 12 wt% Si makes the alloy eutectic, and the Si percentage together with the heating/cooling rates in the SLM process can make it a critical alloying element. SLM processing was carried out using the machine system _SLM 250 HL_ (SLM Solutions, Luebeck, Germany) applying chessboard scanning strategy shown in Figure 2a where each chess field consisted of an edge length of 7.47 mm. Within the individual chess fields, hatch direction was altered by 90\({}^{\circ}\). A rotation of 79\({}^{\circ}\) was employed for each layer, as shown in three layers in Figure 2b, to reduce anisotropy in the resulting material properties. The melting parameters used were: laser power of 350 W, scan speed of 930 mm/s, hatch distance of 0.19 mm, and a layer thickness of 50 \(\upmu\)m. The same scanning strategy was used for the core and contour of the specimens, as shown in Figure 2c, as they were machined and polished before testing was carried out. The test specimens to which these cylindrical rods were converted are shown in Figure 3d for tensile and high cycle fatigue testing, and in Figure 2e for very high cycle fatigue specimens. \begin{table}
\begin{tabular}{c c c c c c c c} \hline
**Element** & **Al** & **Si** & **Cu** & **Fe** & **Mn** & **Zn** & **Ti** & **Others** \\ \hline wt\% & Bal. & 12.00 & 0.05 & 0.55 & 0.35 & 0.10 & 0.15 & 0.05 \\ \hline \end{tabular}
\end{table} 
Table 2: The nominal chemical composition of Al4047 powder. Figure 1: Characteristics of Al4047 powder: (**a**) morphology of powder particles; and, (**b**) the corresponding powder size distribution (PSD). Cubical specimens were prepared for part surface and microstructural analysis, which were ground and subsequently polished using oxide suspension.