## 3 Results and Discussions
\begin{tabular}{c} 2.57 \\ 1.97 \\ 2.22 \\ \end{tabular}  & 2.25 & \ \begin{tabular}{c} 186.28 \\ 185.38 \\ 185.32 \\ \end{tabular}  & 185.66 & \begin{tabular}{c} 7.95 \\ 7.58 \\ 8.80 \\ \end{tabular}  & 8.10 \\ \hline
18 & \(259\) &
\begin{tabular}{c} 0.00 \\ 0.  
which is shown by the \(\alpha 2\) and \(\alpha 1\) specimens, can be obtained by evaluating the fracture surface of the welding joint. The macrograph of the fracture surfaces of \(\alpha 0\), \(\alpha 1\), and \(\alpha 2\) is shown in Figure 4.  
From Figure 4 it can be seen that the \(\alpha 1\) specimens produce better coalescence, which is shown by the fracture on the steel and brass bars. By nature, the steel shows a black color in Figure 4 whilst the brass tends to be yellow. On the fracture surface of the \(\alpha 1\) specimen, quite a lot of yellow dimples can be observed on the steel bar (left side), which represent the brass. Conversely, black dimples can be found on the brass bar (right side) for the steel. This appearance proves that by sharpening the steel bar, better smelting was obtained, which in turn improves the performance of the joint under a SCC load. The same trend is also found in the \(\alpha 2\) specimen, but in a smaller number, while for the \(\alpha 0\) specimen, no such dimples were found on the fracture surface, which shows the bad coalescence of the interface. Another confirmation can also be taken from the flash which develops in the joint. In the \(\alpha 1\) specimen, a lot of flash is found in the fracture photo, especially in the steel bar. A small number of flashes can be found in the \(\alpha 2\) specimen, especially on the brass side. It should be noted that it seems the flash was built at the sharpening side. The last and the least number of flashes can be found at the flat interface of specimen \(\alpha 0\). The larger flash showed better melting. Evaluating the flashes confirms the obtained stress corrosion cracking threshold of Figure 3.  
Figure 4: The fracture surface of the CDW welding joints after being exposed to the SCC load. Figure 3: SCC threshold for varied surface preparation set up. Our recent study suggests that the welding joint is more susceptible to the SCC when the welded materials have more residual stresses and voids. The void acts as crack initiator and may grow and form cracks [6; 24]. Considering the embedded residual stresses and cracks, which easily occur in the welded joint: once it is exposed to the corrosive surroundings, all three ingredients of SCC are provided and the SCC failure exists in the welded joints. The SEM/EDS evaluation of the welded interface of the \(\alpha 0\) specimen is shown in Figure 5. Figure 5a shows the interface with a 50x magnification. Figure 5a also shows the position where the EDS was applied. The position where SEM/EDS was exhibited in the joint between mild steel and brass is shown in Figure 5b. It can be seen that there are porosity and fibrous networks, which initiate fracture at the welded joint. The fibrous network indicates the ductile fracture [25]. The local pit corrosion is spread over the interface. The existence of the O element indicates the oxidation of the welded joint when exposed to the HNO\({}_{3}\) solution. The increasing C is able to promote local pitting corrosion. Figure 5d-g shows a mapping of C, O, Fe, Cu, and Zn elements. It should be noted that Fe-C is the major element of mild steels whilst Cu and Zn are the dominant elements of brass. In the interface, the elements of Cu and Zn increase, which indicates that the brass deliquesce easier than steel. This is plausible since the melting point of brass is lower. Figure 6 shows the SEM/EDS photos of \(\alpha 1\) specimens. Compared to Figure 5, it can be seen that less void and corrosion products are found. As in Figure 5, Cu and Zn dominate more than Fe, although both elements are less compared to the \(\alpha 0\) specimen. The O element decreases, which indicates that less oxidation took place, which in turn increases the strength of \(\alpha 1\).