## 2 Materials and Methods
### Methodology
#### 2.2.2 Fabrication  
Aluminum is a highly reflective and thermally conductive material for any laser-enabled AM process. Therefore, a high-power TeraBlade-2000 direct-diode 949-1001 nm wavelength CW laser (TeraDiode, a Panasonic company, Wilmington, MA, USA) was used in this study to fabricate Scalmalloy. Laser-enabled AM processes can be classified into three categories such as powder-bed SLM, powder-fed DED, and wire-fed DED. In all these processes, the surface exhibits a waviness profile and roughness. The surface roughness and waviness are defined by ASME B46.1 [31; 63] as low-frequency and high-frequency components, respectively. The surface roughness depends on the input energy density applied to fabricate the material. Poor energy density choices during deposition yield material defects that mimic bulge-like structures on the surface and increase the surface roughness [53] while high-wavelength surface features (waviness) exist on the surface of AM parts because of the layer width and thickness. These features are especially high  
Figure 1: Experimental setup used in this study for direct energy deposition (DED) and laser-aided machining and polishing (LAMP) processes.  
in the DED process, where the beam size is larger compared to the SLM process beam size, and the track overlap leads to a wavy surface pattern. Therefore, in this study, the powder-fed DED process was employed with no raster rotation to obtain an initially high surface roughness after deposition. Figure 2a exhibits the schematic representation of the raster pattern used for material deposition. The fabrication process parameters used to deposit Scalmalloy are listed in Table 2. Based on the design of experiments, a total of 44 rectangular patches with dimensions of 27 mm \(\times\) 27 mm \(\times\) 1 mm were deposited to obtain optimized LAMP process parameters for good surface quality. All the samples were deposited on 5000 series aluminum alloy substrate (152.4 mm \(\times\) 152.4 mm \(\times\) 12.7 mm). Among 44 rectangular deposits, 12 samples were used for the machining process while half of the remaining samples were used for macro-polishing and the rest for the micro-polishing process. Figure 3a shows the first 12 samples deposited and used for optimizing the machining process.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameters**} & **Laser** & **Travel** & **Layer** & **Layer** & **Overlap** & **Raster Rotation** & **Powder** & **Shield Gas** \\  & **Power** & **Speed** & **Width** & **Thickness** & **Between Tracks** & **Rotation** & **Flow Rate** & **Flow Rate** \\  & **(W)** & **(mm/min)** & **(mm)** & **(mm)** & **(\%)** & **(degree)** & **(g/min)** & **(L/min)** \\ \hline Value & 1600 & 500 & 2.5 & 0.300 & 30 & 0 & 6 & 4 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Fabrication process parameters used to deposit Scalmalloy.  
Figure 3: Top view of Scalmalloy samples from #1 to #12 (**a**) deposited with process parameters mentioned in Table 2 and (**b**) machined with different process parameters presented in Table 3.  
Figure 2: Schematic representation (not to scale) of (**a**) the CW laser scan pattern for material deposition and macro-polishing and (**b**) pulsed laser scan pattern for machining and micro-polishing. The PL scan pattern rotates radially inward in an anti-clockwise direction.