## 3 Results and Discussion
According to the literature, first, the liquid metal transforms into an \(\alpha\)-phase solid, and then the \(\beta\)-phase precipitates at the \(\alpha\) grain boundaries. With continuous cooling, the disorder \(\beta\)-phase is transformed to the ordered \(\beta^{\prime}\). In addition, the tin content of the alloy was more stable in the \(\beta^{\prime}\)-phase, and this information can be proven with the results  
Figure 5: Qualitative scanning of the energy dispersive x-ray spectroscopy (EDS) map in particles emphasizing high concentrations of (a) iron and (b) lead. Figure 6: (**a**) SEM micrograph showing the phase structure at higher magnification, EDS spectrum of the (**b**) \(\alpha\)-phase area and (**c**) \(\beta\)-phase area. presented in Figure 5, which shows that, in the EDS spectrum, Sn was contained only in the \(\beta^{\prime}\)-phase [26]. The stress-strain results of 13 samples, including the reference sample with 34% cold work, are shown in Figure 7. All specimens fractured in the center of the gauge length. We observed, in Figure 7, the effect of temperature on the shape of the stress-strain curves of manganese bronze. Technologically, the stress-strain curves from 200 to 350 \({}^{\circ}\)C, shown in Figure 7, represent the temperature range of warm working, where the recovery process takes place; therefore, the degree of hardening by deformation is considerably less than in cold working. Probably, the stress-strain curves from 350 to 750 \({}^{\circ}\)C represent the hot working, also called hot forming, that involves deformation at temperatures above the recrystallization temperature. The microstructure changes and variation of the yield strength, tensile strength, and ductility with the temperature during the heat treatment are shown in Figure 8a,b, respectively. Figure 8 presents the increasing annealing temperature with the subsequent increased ductility and decrease in the ultimate tensile strength and yield strength. Studies found the annealing of metallic material with addition of plasticity [27]. This effect occurred because, during the annealing, there was a decrease of the stored energy during plastic deformation due to the mechanisms of rearrangement and the annihilation of crystal defects. This process can be divided in three states: recovery, recrystallization, and grain growth. The first mechanism is characterized by the annihilation and rearrangement of dislocations occurring normally in low temperatures and involves thermal activation, with the formation of subgrains with low-angles within the as-deformed grains, and thus high-angle grain boundaries are usually unaffected. The second stage occurs with the nucleation and formation of strain-free new grains, where the driving force is the stored energy in the form of crystalline defects. In this step, the material restores the ductility, hardness, and strength that it had prior to cold deformation. The lowest temperature that forms new grains in a plastically deformed metal is known as the recrystallization temperature and normally corresponds to \(1/3\) to \(1/2\) of the melting point on the Kelvin scale. The last stage is characterized by the migration of boundaries; however, in this case, the driving force is the energy of the high angle boundaries [28; 29]. Figure 7: Evaluation of the strength and ductility parameters of samples that were heat-treated for 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, and 750 \({}^{\circ}\)C.  
The heat treatment of the samples showed that the recovery may have occurred between 200 and 350 \({}^{\circ}\)C, with the gradual reduction of engineering stress when compared with the reference sample. The reference sample presented a solid \(\beta\) solution matrix structure with the presence of a tensioned circular \(\alpha\)-phase and intermetallic constituents dispersed in the material structure.