## 3 Results and Discussion  
The optical micrographs of the materials shown in Figure 3a,b indicate that the alloy consisted of \(\alpha\)-phase and \(\beta\)- phase and that the \(\alpha\)-phase had a long island shape that is typical for manganese bronze [1]. In the microstructure, the light areas correspond to the \(\alpha\)-phase, which possesses a face-centered cubic (fcc) lattice, while the dark areas correspond to the b-phase possessing a body-centered cubic (bcc) lattice. Figure 3c,d show the SEM micrograph of the structure. Figure 3d shows several types of non-dissolved small intermetallic precipitation that contain darker particles in the \(\alpha\)-phase and lighter particles in the \(\beta\)-phase. Therefore, technical scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS) mapping was used to investigate the qualitative distribution of the elements in the sample. It is important to highlight that the different magnifications used in tests (optical and SEM micrographs) and the crystallographic orientation of the grains produce variations in the microstructure analysis. Each micrograph in Figure 3 was described in terms of these conditions. Figure 4 shows the results obtained using energy dispersive spectroscopy (EDS). The copper and zinc showed a partially uniform distribution with small variations in the \(\alpha\)- and \(\beta\)-phase. In addition, the regions corresponding to the particles showed a significant decrease in the concentration of these elements. The manganese was uniformly distributed throughout the matrix, and the tin showed variations according to the region analyzed, which will be discussed in more detail later. The iron had a significant accumulation in determinate areas, indicating that specific particles of this element exist in the matrix. Lastly,  
Figure 2: Specim for the measurement of the mechanical property tests with the values in millimeters. the lead was homogeneously distributed; however, there were some areas that were less intense for this element. The SEM-EDS maps identified several types of non-dissolved particles: Fe spherical shapes with a dark color and Pb agglomerates with a light color. In Figure 5a, iron is predominantly concentrated at the \(\alpha\)-phase, and this occurs because it has a low solubility in the molten copper alloys. According to [PERSON] et al., these particles have a bcc structure and, based on their crystal structure and chemistry, can be identified as \(\alpha\)-Fe [22]. In 60/40 brass, the solubility of iron reduces from about 1.5 wt.% at 1020 \({}^{\circ}\)C to 0.04 wt.% at 950 \({}^{\circ}\)C [23]. This promotes the fine precipitation of iron particles that act as nuclei for new \(\alpha\)-phase grains [24]. Figure 4: Qualitative scanning of the energy dispersive X-ray spectroscopy (EDS) map, with distributions of the elements Sn, Pb, Cu, Mn, Zn, and Fe in the alloy. Figure 3: Optical micrograph showing the microstructure of the UNS C67600 alloy after cold worked and heat treatment at 650 \({}^{\circ}\)C (**a**) \(\alpha\)-phase needles (light areas) are present in the dark \(\beta\)-phase. (**b**) Detail of (**a**), dark particles of Pb and lighter particles of Fe are present. (**c**) SEM micrograph showing the \(\alpha\)-phase in the dark \(\beta\)-phase. (**d**) Detail of (**c**). Lead has low solubility in solid copper, and so the lead particles appear as light and discrete globules at the \(\alpha/\beta\) grain boundaries as high surface energy sites [25]. To prove this, the samples were inspected with elemental microanalysis using energy dispersive spectroscopy (EDS), and Figure 5b shows the results. Figure 5a shows the microstructure observed in SEM micrograph indicating the phases and particles. The EDX point chemical analysis of the \(\alpha\)- and \(\beta\)-phase are shown in Figure 6b,c, respectively. The results are similar to those noted in the literature, in which the \(\beta\)-phase has approximately \(55\%\) copper, and the \(\alpha\)-phase has \(64\%\)[25].