OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 26 No. 3 2024 subject to continuous anodic oxidation accompanied by the formation of Cu+ and Cu2+ ions. Additionally, cathodic processes described by reactions (9), (10) are possible on the surface of copper phases, partially impeding its ionization. Thus, in the presence of strong oxidizing agents (Cl-) the formation of corrosion pits in the composites based on aluminum bronze and stainless steel will be accelerated if the formation of Fe/Cr microgalvanic couples is not prevented (Fig. 7, e). In order to increase the corrosion properties of these composites, it is necessary to carry out surface treatments leading to the formation of continuous and dielectric oxide films on the surface of α-Cu, α-(Fe,Cr) and γ-(Fe,Ni,Cr) phases, preventing a direct electrochemical contact of Fe/Cr at interphase boundaries. Conclusions The paper presents experimental results of the electrochemical behavior of the CuAl9Mn2/ER 321 composites obtained by the additive electron beam method. With an increase in the volume fraction of steel in aluminum bronze, the microhardness, yield strength and strength of the composites change in a nonmonotonic manner and reach the highest values in the specimen containing 50 vol. % of the steel. Corrosion resistance of the specimens in 3.5 wt. % NaCl solution was estimated using the Tafel extrapolation method. It has been found that the densities of corrosion currents monotonically decrease for the composites obtained at the ratios CuAl9Mn2 : ER 321 = 90 : 10, 75 : 25, 50 : 50 and 25 : 75, and the polarization resistance, that is inversely proportional to the corrosion rate, increases by an order of magnitude. A comprehensive assessment of the electrochemical properties of the specimens using impedance spectroscopy and cyclic voltammetry has shown that the most corrosion resistant is a composite with 75 vol. % of the ER 321 steel, and the lowest corrosion resistance is demonstrated by the CuAl9Mn2 alloy and a composite with 10 vol. % of the ER 321 steel. It has been observed that the main processes on the surface of composites are anodic oxidation of Cu and Fe, leading to the formation of corrosion products – Cu2O and FeCl2. It is assumed that the main mechanism of the corrosion damage in the CuAl9Mn2/ER 321 composites is a galvanic corrosion caused by the formation of galvanic Fe/Cr pairs at the interphase boundaries between ferrite particles α-(Fe,Cr) and the α-Cu matrix. References 1. Wang L., Tieu A.K., Lu S., Jamali S., Hai G., Zhu Q., Nguyen H.H., Cui S. Sliding wear behavior and electrochemical properties of binder jet additively manufactured 316SS /bronze composites in marine environment. Tribology International, 2021, vol. 156, p. 106810. DOI: 10.1016/j.triboint.2020.106810. 2. Ateya B.G., Ashour E.A., Sayed S.M. Corrosion of α-Al bronze in saline water. Journal of the Electrochemical Society, 1994, vol. 141 (1), p. 71. DOI: 10.1149/1.2054712. 3. Davis J.R., ed. Copper and copper alloys. Materials Park, OH, ASM International, 2001. 869 p. 4. Blau P.J. Investigation of the nature of micro-indentation hardness gradients below sliding contacts in five copper alloys worn against 52100 steel. Journal of Materials Science, 1984, vol. 19, pp. 1957–1968. DOI: 10.1007/ BF00550266. 5. Shi Z., Sun Y., Bloyce A., Bell T. Unlubricated rolling-sliding wear mechanisms of complex aluminium bronze against steel. Wear, 1996, vol. 193 (2), pp. 235–241. DOI: 10.1016/0043-1648(95)06773-6. 6. Kwarciak J., Bojarski Z., Morawiec H. Phase transformation in martensite of Cu-12.4% Al. Journal of Materials Science, 1986, vol. 21, pp. 788–792. DOI: 10.1007/BF01117355. 7. Adorno A.T., Guerreiro M.R., Benedetti A.V. Isothermal aging kinetics in the Cu–19 at.%Al alloy. Journal of Alloys and Compounds, 2001, vol. 315 (1–2), pp. 150–157. DOI: 10.1016/S0925-8388(00)01268-8. 8. Zykova A.P., Panfilov A.O., Chumaevskii A.V., Vorontsov A.V., Nikonov S.Yu., Moskvichev E.N., Gurianov D.A., Savchenko N.L., Tarasov S.Yu., Kolubaev E.A. Formation of microstructure and mechanical characteristics in electron beam additive manufacturing of aluminum bronze with an in-situ adjustment of the heat input. Russian Physics Journal, 2022, vol. 65, pp. 811–817. DOI: 10.1007/s11182-022-02701-6. 9. Li W.S., Wang Z.P., Lu Y., Gao Y., Xu J.L. Preparation, mechanical properties and wear behaviours of novel aluminum bronze for dies. Transactions of Nonferrous Metals Society of China, 2006, vol. 16 (3), pp. 607–612. DOI: 10.1016/S1003-6326(06)60107-6.
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