OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 25 No. 1 2023 Ta b l e 1 Mechanical properties of specimens printed from C65500 and with the addition of aluminum filament Specimen designation Offset yield strength, MPa Ultimate strength, MPa Strain-to-fracture, % C65500 (mode 1) 89 242 83 C65500 (mode 2) 93 294 75 C65500 (mode 3) 82 253 114 C65500 (annealing) 92 301 76 C65500 (deformation + annealing) 75 318 91 C65500 (10 wt.% Al) 203 434 21 C65500 (10 wt.% Al–5Si) 150 394 67 C65500 (10 wt.% Al–12Si) 186 448 57 Mechanical properties of specimens Changing the heat input, the use of thermal and mechanical treatments, as well as alloying with aluminum through the use of multiwire technology, made it possible to obtain bronze specimens not only with different structures, but also with modified mechanical properties. It can be seen that the specimens printed using the multiwire technique have the highest strength (Table 1). In addition, these specimens (with the exception of the C65500 alloy with the addition of 10 wt.% Al) are characterized by sufficiently high ductility. Consequently, the two-phase structure of the specimens printed with the addition of Al-5Si and Al-12Si alloys is characterized by high strength and simultaneously high ductility. More detailed study of the strength of the specimens under consideration is presented [22, 23]. Structural modifications have also affected the microhardness of the specimens (Fig. 5). Heat treatment expectedly reduced the microhardness due to the removal of residual stresses. As in the case of strength, specimens with a two-phase structure have a higher hardness compared to that of the single-phase ones. The increase in microhardness was 140–215 %. Corrosion The above-described differences in the structural and phase states of the studied specimens affected not only its mechanical properties, but also its corrosion resistance. Figure 6 shows the potentiodynamic polarization curves that were recorded during the study of the electrochemical corrosion. In all the cases under consideration, the potential changes in the cathode part of the curves are without any significant fluctuations. In the anodic part of the curves, the potential changes similarly to that of the cathodic one, but there is a small region with a slowing growth in the potential, which may indicate passivation of the specimen’s surface. For a specimen, subjected to pre-deformation and annealing, this section is the longest (Fig. 6a). Therefore, this specimen is the most resistant to the action of the corrosive media, which can be caused by more active formation of aluminum and copper oxides, which hinder the anodic dissolution of the specimen. Such an increase in chemical activity may be the result of a refinement of the material structure, accompanied by an increase in the length of grain boundaries. The boundaries serve as a source of active ions that react with the solution in the electrochemical cell and form passive oxide films. In addition, the results obtained indicate the absence of pitting on the surface of all specimens. The parameters of the electrochemical potential of the specimens were established. The corrosion potential (Table 2) for specimens printed with low (mode 1), medium (mode 2) and high (mode 3) heat input are as follows: -178 mV, -210 mV and -202 mV, respectively. The post-manufacture annealing of both as-
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