## 2 Materials and Methods  
In the CCDR process, a single machine directly produces Al alloy wire coils (Figure 1a,b), Tainan, Taiwan, Ting Sin Co., Ltd.. In this study, CCDR Al-Si alloy bars with diameters \(\phi\)10 mm serve as the research materials applied in the tensile and erosion wear tests, shown in Figure 1e-i (as-manufactured and under processing). The chemical compositions of the research materials named \"F\" are as shown in Table 1. In the pre-experiment, CCDR Al-Si alloy bars were rolled into strips of different thicknesses through different reduction rates, then used to confirm the maximum cold working limit of cold rolling by the observation of crack formations on the edges of specimens. As the results exhibited, the reduction ratio was set at 60%, which was named \"FR\" (diameter of the specimen: 10 mm\(\rightarrow\)4 mm), as shown in Figure 1c. Moreover, FR were subjected to solid solution treatment at 540 \({}^{\circ}\)C for 4 h (water quench) and aging at 170 \({}^{\circ}\)C for 12 h (air cooling). Those were named \"FRH\". The parameters and motivations are summarized in Table 2.  
Figure 1: (**a**) Al-Si alloy CCDR equipment, (**b**) bar coil of the CCDR Al-Si alloy, (**c**) schematic diagram of the bar being cold rolled into strip, (**d**) the definition of the axial and transverse sections, (**e**) as-manufactured and (**f**) as-manufactured after rolling, (**g**) dumbbell-shaped tensile specimens, (**h**) dog-bone-shaped tensile specimens, and (**i**) specimens for erosion wear. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Elements** & Al & Si & Fe & Cu & Mn & Mg & Zn & Ti \\ \hline
**Composition** & Bal. & 4.86 & 0.23 & 0.079 & 0.003 & 0.002 & 0.017 & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chemical composition analysis of the Al-Si alloy (wt.%). The microstructure was observed in the parallel (axial section) and vertical (transverse section) directions to the rolling direction from the CCDR process, as shown in Figure 1d with an optical microscope (Olympus BX41M-LED, Tokyo, Japan) and scanning electron microscopy (SEM) (Hitachi SU-5000, Hitachi, Tokyo, Japan). The specimens were grounded with #80-#4000 SiC sandpaper and polished with 1 and 0.3-\(\mu\)m Al\({}_{2}\)O\({}_{3}\) and 0.05-\(\mu\)m SiO\({}_{2}\) powder. Afterwards, [PERSON]'s reagent (19-mL HNO\({}_{3}\) + 9-mL HCl + 6-mL HF + 19-mL H\({}_{2}\)O) was used to etch the surface. For the tensile test, the F was processed into dumbbell-shaped tensile specimens (Figure 2a). After the rolling process, the bars were transformed into sheets, the FR and FRH were processed into dog-bone-shaped tensile specimens (Figure 2b) at a fixed tensile rate of 1 mm/ min. Each parameter was subjected to ten times tensile tests for averaging the strength and elongation. The hardness was detected in units of HRF (Mitutoyo AR-10, Kawasaki, Japan). The erosion specimens and experimental equipment to investigate the wear resistance are shown in Figure 3a-c. The eroded particles (Figure 3d) are irregular Al\({}_{2}\)O\({}_{3}\) particles (range from 125 to 150 \(\mu\)m). The erosion test was conducted with 200-g Al\({}_{2}\)O\({}_{3}\) ceramic \begin{table}
\begin{tabular}{c c c} \hline
**Group** & **Treatment Conditions** & **Motivations** \\ \hline F & As-manufactured & fundamental material \\  & & properties evaluation \\ \hline FR & as-manufactured + rolling & strain hardening \\ \hline FRH & As-manufactured + rolling + heat treatment & secondary cold working \\ \hline \end{tabular}
\end{table} 
Table 2: Treatment conditions and motivations for each group. Figure 2: Specifications of the tensile specimens: (**a**) group F, (**b**) groups FR and FRH, and (**c**) specimens for erosion wear (a flow chart of three pieces combined into one piece). particles, the inlet pressure was fixed at 3 \(\frac{\text{k}\text{g}\text{f}}{\text{cm}^{2}}\), and the working distance was 20 cm. The impact angle ranged from 15\({}^{\circ}\) to 90\({}^{\circ}\), and the interval increment was 15\({}^{\circ}\).