Vol. 27 No. 3 2025 3 EDITORIAL COUNCIL EDITORIAL BOARD EDITOR-IN-CHIEF: Anatoliy A. Bataev, D.Sc. (Engineering), Professor, Rector, Novosibirsk State Technical University, Novosibirsk, Russian Federation DEPUTIES EDITOR-IN-CHIEF: Vladimir V. Ivancivsky, D.Sc. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Vadim Y. Skeeba, Ph.D. (Engineering), Associate Professor, Department of Industrial Machinery Design, Novosibirsk State Technical University, Novosibirsk, Russian Federation Editor of the English translation: Elena A. Lozhkina, Ph.D. (Engineering), Department of Material Science in Mechanical Engineering, Novosibirsk State Technical University, Novosibirsk, Russian Federation The journal is issued since 1999 Publication frequency – 4 numbers a year Data on the journal are published in «Ulrich's Periodical Directory» Journal “Obrabotka Metallov” (“Metal Working and Material Science”) has been Indexed in Clarivate Analytics Services. Novosibirsk State Technical University, Prospekt K. Marksa, 20, Novosibirsk, 630073, Russia Tel.: +7 (383) 346-17-75 http://journals.nstu.ru/obrabotka_metallov E-mail: metal_working@mail.ru; metal_working@corp.nstu.ru Journal “Obrabotka Metallov – Metal Working and Material Science” is indexed in the world's largest abstracting bibliographic and scientometric databases Web of Science and Scopus. Journal “Obrabotka Metallov” (“Metal Working & Material Science”) has entered into an electronic licensing relationship with EBSCO Publishing, the world's leading aggregator of full text journals, magazines and eBooks. The full text of JOURNAL can be found in the EBSCOhost™ databases.
OBRABOTKAMETALLOV Vol. 27 No. 3 2025 4 EDITORIAL COUNCIL EDITORIAL COUNCIL CHAIRMAN: Nikolai V. Pustovoy, D.Sc. (Engineering), Professor, President, Novosibirsk State Technical University, Novosibirsk, Russian Federation MEMBERS: The Federative Republic of Brazil: Alberto Moreira Jorge Junior, Dr.-Ing., Full Professor; Federal University of São Carlos, São Carlos The Federal Republic of Germany: Moniko Greif, Dr.-Ing., Professor, Hochschule RheinMain University of Applied Sciences, Russelsheim Florian Nürnberger, Dr.-Ing., Chief Engineer and Head of the Department “Technology of Materials”, Leibniz Universität Hannover, Garbsen; Thomas Hassel, Dr.-Ing., Head of Underwater Technology Center Hanover, Leibniz Universität Hannover, Garbsen The Spain: Andrey L. Chuvilin, Ph.D. (Physics and Mathematics), Ikerbasque Research Professor, Head of Electron Microscopy Laboratory “CIC nanoGUNE”, San Sebastian The Republic of Belarus: Fyodor I. Panteleenko, D.Sc. (Engineering), Professor, First Vice-Rector, Corresponding Member of National Academy of Sciences of Belarus, Belarusian National Technical University, Minsk The Russian Federation: Vladimir G. Atapin, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Victor P. Balkov, Deputy general director, Research and Development Tooling Institute “VNIIINSTRUMENT”, Moscow; Vladimir A. Bataev, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Vladimir G. Burov, D.Sc. (Engineering), Professor, Novosibirsk State Technical University, Novosibirsk; Aleksandr N. Korotkov, D.Sc. (Engineering), Professor, Kuzbass State Technical University, Kemerovo; Dmitry V. Lobanov, D.Sc. (Engineering), Associate Professor, I.N. Ulianov Chuvash State University, Cheboksary; Aleksey V. Makarov, D.Sc. (Engineering), Corresponding Member of RAS, Head of division, Head of laboratory (Laboratory of Mechanical Properties) M.N. Miheev Institute of Metal Physics, Russian Academy of Sciences (Ural Branch), Yekaterinburg; Aleksandr G. Ovcharenko, D.Sc. (Engineering), Professor, Biysk Technological Institute, Biysk; Yuriy N. Saraev, D.Sc. (Engineering), Professor, V.P. Larionov Institute of the Physical-Technical Problems of the North of the Siberian Branch of the RAS, Yakutsk; Alexander S. Yanyushkin, D.Sc. (Engineering), Professor, I.N. Ulianov Chuvash State University, Cheboksary
Vol. 27 No. 3 2025 5 CONTENTS OBRABOTKAMETALLOV TECHNOLOGY Kondratiev V.V., Gozbenko V.E., Kononenko R.V., Konstantinova M.V., Guseva E.A. Determination of the main parameters of resistance spot welding of Al-5 Mg aluminum alloy..................................................................................... 6 Gvindjiliya V.E., Fominov E.V., Marchenko A.A., Lavrenova T.V., Debeeva S.A. Infl uence of cutting speed on pulse changes in the temperature of the front cutter surface during turning of heat-resistant steel 0.17 C-Cr-Ni-0.6 Mo-V................................................................................................................................................................ 23 Karelin R.D., Komarov V.S., Cherkasov V.V., OsokinA.A., Sergienko K.V., Yusupov V.S., Andreev V.A. Production of rods and sheets from TiNiHf alloy with high-temperature shape memory eff ect by longitudinal rolling and rotary forging methods.................................................................................................................................................................... 37 EQUIPMENT. INSTRUMENTS Zakovorotny V.L., Gvindjiliya V.E., Kislov K.V. Information properties of vibroacoustic emission in diagnostic systems for cutting tool wear................................................................................................................................................ 50 Zhukov A.S., Ardashev D.V., Batuev V.V., Kulygin V.L., Schuleshko E.I. Modal analysis of various grinding wheel types for the evaluation of their integral elastic parameters...................................................................................... 71 Nishandar S.V., Pise A.T., Bagade P.M. Numerical and experimental investigation of heat transfer augmentation in roughened pipes................................................................................................................................................................ 87 Nosenko V.A., Rivas Perez D.E., Alexandrov A.A., Sarazov A.V. The eff ect of the grinding method on the grain shape coeffi cient of black silicon carbide....................................................................................................................................... 108 MATERIAL SCIENCE Karlina Yu.I., Konyukhov V.Yu., Oparina T.A. Investigation of the process of surface decarburization of steel 20 after cementation and heat treatment.................................................................................................................................. 122 Kovalevskaya Z.G., Liu Y. Eff ect of heat treatment on the structure and properties of high-entropy alloy AlCoCrFeNiNb0.25............................................................................................................................................................. 137 Sirota V.V., Prokhorenkov D.S., Churikov A.S., Podgorny D.S., Alfi mova N.I., Konnov A.V. Corrosion properties of coatings produced from self-fl uxing powders by the detonation spraying method............................................................ 151 Filippov A.V., Shamarin N.N., Tarasov S.Yu., Semenchyuk N.A. The infl uence of structural state on the mechanical and tribological properties of Cu-Al-Si-Mn bronze............................................................................................................. 166 Waheed F., Qayoom A., Shirazi M.F. Fabrication, characterization and performance evaluation of zinc oxide doped nanographite material as a humidity sensor......................................................................................................................... 183 Dolgova S.V., Malikov A.G., Golyshev A.A., Nikulina A.A. Features of the structure of gradient layers «steel - Inconel - steel», obtained by laser direct metal deposition.................................................................................................. 205 Burkov A.A., Dvornik M.A., Kulik M.A., Bytsura A.Yu. The infl uence of tungsten carbide particle size on the characteristics of metalloceramic WC/Fe-Ni-Al coatings.................................................................................................... 221 Patil S., Chinchanikar S. Investigation on the mechanical properties of stir-cast Al7075-T6-based nanocomposites with microstructural and fractographic surface analysis...................................................................................................... 236 EDITORIALMATERIALS 252 FOUNDERS MATERIALS 263 CONTENTS
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 The influence of structural state on the mechanical and tribological properties of Cu-Al-Si-Mn bronze Andrey Filippov а, *, Nikolay Shamarin b, Sergei Tarasov c, Natalya Semenchyuk d Institute of Strenght Physics and Materials Sciences SB RAS, 2/4 per. Academicheskii, Tomsk, 634055, Russian Federation a https://orcid.org/0000-0003-0487-8382, avf@ispms.ru; b https://orcid.org/0000-0002-4649-6465, shnn@ispms.ru; c https://orcid.org/0000-0003-0702-7639, tsy@ispms.ru; d https://orcid.org/0000-0001-6547-7676, natali.t.v@ispms.ru Obrabotka metallov - Metal Working and Material Science Journal homepage: http://journals.nstu.ru/obrabotka_metallov Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science. 2025 vol. 27 no. 3 pp. 166–182 ISSN: 1994-6309 (print) / 2541-819X (online) DOI: 10.17212/1994-6309-2025-27.3-166-182 ART I CLE I NFO Article history: Received: 23 June 2025 Revised: 03 July 2025 Accepted: 10 July 2025 Available online: 15 September 2025 Keywords: Additive manufacturing Bronze Microstructure Phase composition Mechanical properties Severe plastic deformation (SPD) Sliding friction Funding This research was funded by Russian Science Foundation project № 24-2900259, https://rscf.ru/project/ 24-2900259/. ABSTRACT Introduction. Electron beam additive manufacturing (EBAM) is a promising method for producing new alloys with unique properties. At the same time, existing problems with obtaining a high-quality structure require a search for a technical solution that ensures grain refinement and the formation of a more homogeneous microstructure. For strain-hardened copper alloys, severe plastic deformation (SPD) methods are effective ways to control their structural state and mechanical properties. Currently, the effect of severe plastic deformation on the structure, mechanical, and tribological properties of Cu-Al-Si-Mn bronze, which is promising for industrial application, has not been studied. The aim of this work is to study the relationship between the structural state formed as a result of severe plastic deformation and the mechanical and tribological properties of Cu-Al-Si-Mn bronze samples. The paper studies samples of Cu-Al-Si-Mn bronze, made from bronze (3% Si-1% Mn) wires and commercially pure aluminum using multiwire electron beam additive manufacturing. For targeted changes in structure and properties, the resulting additively manufactured blanks were subjected to severe plastic deformation. Multi-axial forging and rolling were used as SPD methods, aimed at significant grain refinement and increased strength characteristics. The work uses such research methods as transmission electron microscopy (TEM) for a detailed analysis of the submicron structure after SPD, X-ray diffraction (XRD) to identify the phase composition of the alloy, tensile tests to determine key mechanical properties such as tensile strength, yield strength, and percentage of elongation, microhardness measurements to assess the hardening of samples using Vickers loads, confocal laser scanning microscopy (CLSM) for three-dimensional analysis of the surface topography and studying the morphology of worn surfaces, and dry sliding friction tests to assess the wear resistance of the material and the friction coefficient in the absence of lubrication under specified loads and sliding speeds. Results and discussion. Based on the data of transmission electron microscopy, it was found that the use of multiaxial forging and rolling led to significant changes in the structure of the material, as well as its phase composition. Based on the X-ray diffraction analysis, it was revealed that severe plastic deformation contributed to the deformation-induced dissolution of the γ- and β-phases. The results of tensile tests showed that the highest strength is achieved after intense plastic deformation by rolling, after multi-axial forging. SPD by multi-axial forging and subsequent rolling led to an increase in the microhardness of bronze. The results of tribological tests showed that SPD contributes to a decrease in the friction coefficient (FC) compared to the material in the printed state. Heat treatment of samples after SPD led to an increase in FC and an increase in fluctuations in its value. SPD by multiaxial forging and subsequent rolling contributes to a significant increase in the wear resistance of samples under dry sliding friction conditions. Low-temperature annealing after SPD leads to a decrease in the wear resistance of deformed samples. Thus, the use of SPD makes it possible to increase the strength and wear resistance of bronze samples of the Cu-Al-Si-Mn system. For citation: Filippov A.V., Shamarin N.N., Tarasov S.Yu., Semenchyuk N.A. The influence of structural state on the mechanical and tribological properties of Cu-Al-Si-Mn bronze. Obrabotka metallov (tekhnologiya, oborudovanie, instrumenty) = Metal Working and Material Science, 2025, vol. 27, no. 3, pp. 166–182. DOI: 10.17212/1994-6309-2025-27.3-166-182. (In Russian). ______ * Corresponding author Filippov Andrey V., Ph.D. (Engineering), Head of Laboratory Institute of Strenght Physics and Materials Sciences SB RAS, 2/4 per. Academicheskii, 634055, Tomsk, Russian Federation Tel.: +7 999 178-13-40, e-mail: avf@ispms.ru Introduction Bronzes are metal alloys that have a range of qualities making them essential for numerous uses, especially in corrosive environments and under sliding friction. The structural and phase states of bronzes dictate their mechanical, tribological, and corrosion properties, which are chosen based on the alloy’s intended use and can be modified through suitable alloying. The key alloying elements for bronzes are aluminum, iron, nickel, tin, zinc, lead, manganese, and silicon, which are part of the composition of wellknown bronze grades from the Cu-Al, Cu-Mn, Cu-Zn, Cu-Pb, Cu-Si, Cu-Al-Fe, Cu-Ni-Al, and Cu-Al-Fe-Ni
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 systems. The desired level of properties is attained not just by adjusting the alloying components but also through further thermal treatment and mechanical processing, which influences the material’s physical and mechanical properties [1]. Even though a significant amount of work has already been accomplished in this field, ongoing exploratory research continues to be directed toward the creation of innovative structural and functional materials to meet contemporary industrial demands [1]. Although significant progress has been made in this field, ongoing exploratory research continues to focus on creating new structural and functional materials for contemporary industrial requirements. The present phase of progress in material technologies is linked to the enhancement of additive techniques for creating items from robust materials that have excellent processability, adequate corrosion resistance, and wear resistance. To achieve an additive material with an adequate level of strength and functional characteristics, it is essential to identify a logical combination of printing parameters and filament formulation. The most crucial factor is the selection of the alloying element composition that will yield the required structure and phase constitution. Following this, the thermal treatment and mechanical processing modes for the printed material are established to achieve the intended functional characteristics. Aluminum bronzes are noted for their excellent strength and formability under pressure. Incorporating silicon enhances ductility and improves resistance to corrosion and cyclic impact loads, all while preserving high strength. These properties can be further enhanced by adding manganese to the Cu-Al-Si system, which promotes increased strength, hardness, and corrosion resistance. Silicon and manganese enhance the stability of the ductile FCC α-phase formed from alloying elements in copper and inhibit the development of the brittle β-Cu3Al phase. Nonetheless, high concentrations of these elements can also result in the formation of silicide particles and other reinforcement phases within the Mn-Al system. This is crucial for enhancing the mechanical characteristics of bronze through mechanical processes (forging, rolling, etc.). In industrial alloys of the Cu-Al system, with approximately 8–12 wt. % Al, the phases that exist in equilibrium at room temperature include the solid solution phase α-Cu(Al) and the intermetallic compounds β-Cu3Al and γ2-Cu9Al4. The latter is the product of the decomposition of high-temperature β-Cu3Al into γ2-Cu9Al4 and α-Cu. The development of γ2-Cu9Al4 causes a reduction in the plasticity and corrosion resistance of bronze; thus, attempts are being made to remove it. One method to accomplish this could involve encouraging the diffusionless change from β to βʹ. The presence of βʹ-Cu3Al greatly influences the mechanical characteristics by enhancing microhardness and strength [5, 6, 7]. In the Cu-Si system, the predominant phase is the solid solution α-Cu(Si). A multiphase composition, comprising copper silicides, develops when the silicon content exceeds 5 wt.% [8]. The creation of copper silicides with higher silicon levels leads to enhanced strength and hardness in copper alloys [9]. The scenario is more intricate with the Cu-Al-Si system. The majority of the research on this system centers on analyzing the phase composition in areas with ele-vated aluminum levels [10–12], along with high silicon concentrations [13]. It has been previously noted that in such bronze, structures with FCC, BCC, and HCP crystal lattices, along with silicide particles, may develop [14]. The composition of phases is directly influenced by the amounts of aluminum and silicon, along with the temperature and the rate of solidification. This study suggests that a rise in aluminum content aids in creating a more multiphase structure. According to the modeling results [15], at temperatures of 500 °C and 700 °C in the Cu-Al-Si ternary system with approximately 10 at.% Al and about 3 at.% Si, the alloy appears to be multiphase. Nonetheless, this paper does not provide findings from structural studies that validate this information. Aluminum bronzes typically exhibit a structure with large columnar grains or dendrites after casting. Similarly, in the three-dimensional printing process using electron beam additive manufacturing, bronzes based on copper-aluminum (Cu-Al), copper-silicon-manganese (Cu-Si-Mn), and copper-aluminummanganese (Cu-Al-Mn) systems also develop a columnar grain structure in the samples [16–18]. These grains are undesirable, hindering the material’s strength and ductility. Therefore, a critical challenge for current researchers is to devise methods for controlling the microstructure of bronze alloys – through techniques like thermomechanical processing or alloying — to ensure improvements in their strength, wear resistance, and fatigue life.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Bronzes containing aluminum, silicon, and manganese are considered strain-hardening alloys. Applying severe plastic deformation (SPD) methods is a practical approach to intentionally modify their structuralphase state and, thereby, their mechanical properties. These methods encompass: forging, rolling, equalchannel angular pressing, high-pressure torsion, and surface plastic deformation [19, 20]. Currently, the impact of SPD on the structural, mechanical, and tribological characteristics of the Cu-AlSi-Mn bronze system, a material with considerable potential for industrial use, remains unexplored. This is particularly the case for materials fabricated via additive manufacturing techniques. In light of the foregoing review, the inherent promise of the material, and the identified deficiencies in existing studies, the objective of this research was established: to explore the correlations between the diverse structural states and the properties of the Cu-Al-Si-Mn copper alloy. To realize this objective, the following experimental tasks were undertaken: – to characterize the structure and phase composition of samples in the as-printed condition and following the application of intense plastic deformation techniques; – to evaluate mechanical properties, specifically tensile strength and microhardness, for samples exhibiting various structural states; – to analyze the tribological behavior of the samples; – to examine the morphology of the wear track surfaces. Methods To investigate the influence of structural states on the properties of Cu-Al-Si-Mn bronze, samples in the form of prismatic blocks (20×20×40 mm³) were fabricated using electron beam additive manufacturing. Printing was performed by simultaneously feeding two wires: Cu-3 Si-1 Mn (BrKMts 3-1) and commercially pure aluminum, in a ratio of 90 % bronze to 10 % aluminum [21]. The chemical composition of the samples was 93.8 wt.% Cu, 2.5 wt.% Al, 2.8 wt.% Si, 0.9 wt.% Mn. The printed blocks were subjected to severe plastic deformation (SPD) by means of multi-directional forging and rolling. In addition, the samples were also subjected to low-temperature heat treatment after SPD. The designations of the investigated samples and the processing parameters are listed in Table. Designation of samples and methods for forming their structure Sample designation Method of forming a structural state 1 Electron beam additive manufacturing 2 Multi-axial forging along three geometric axes until 40% plastic deformation is achieved in each direction 3 Rolling after multi-axial forging until 50% plastic deformation is achieved 4 Low-temperature annealing (30 min. at 400°C) after multi-axial forging with rapid cooling in water 5 Low-temperature annealing (30 min. at 400°C) after rolling with rapid cooling in water Flat tension test specimens were cut from the obtained samples using an electrical discharge machine for mechanical testing on a Testsystem UTS-110M testing machine. The tensile speed was 1 mm/min. Samples in the form of plates were additionally cut for conducting X-ray diffraction analysis on a Shimadzu XRD-7000 diffractometer. Microhardness measurements were performed using a Tochline-TBM microhardness tester with a load of 100 N. The fine structure of the samples was investigated by transmission electron microscopy on a JEOL JEM-2100 microscope. Tribological tests were conducted at a fixed sliding speed of 0.1 m/s and a normal load of 20 N under dry sliding friction conditions using a pin-on-disk scheme. Disks were cut from bronzes with different structural states. Counterbodies were made of ball-bearing steel (1 C-1.5 Cr). Tescan MIRA 3 LMU and Olympus OLS-4100 microscopes were used to investigate the surface condition of the samples after friction
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 using scanning electron microscopy and laser scanning microscopy, respectively. Energy-dispersive X-ray spectroscopy (EDS) was performed to identify the features of the sample condition after friction. Results and Discussion Based on previously obtained results [21] from metallographic studies, it was established that the structure of the printed bronze consists of α-Cu(Al) solid solution grains with a size of approximately 75 μm, interspersed with layers of a secondary phase. Upon examination of the fine structure using transmission electron microscopy, it was revealed that the printed bronze (Sample 1) exhibits laths representing α/β eutectoid lamellae, in which the decomposition β→γ2+ α has occurred (Fig. 1, a). The high dislocation density and two overlapping systems of deformation twins (Fig. 1, b) are a result of multi-directional forging (Sample 2). Rolling (Sample 3) creates a high dislocation density and deformation twins within the material (Fig. 1, c). Primary systems of deformation twins can be disrupted due to the high degree of deformation and replaced by secondary ones, which are significantly smaller than those formed during the multi-directional forging stage. In Sample 4 (Fig. 1, d), one system of deformation twins predominates, remaining intact even after annealing, indicating their sufficiently high stability with respect to heating. In Sample 5 (Fig. 1, e), stacking faults, recrystallized submicron grains, and annealing microtwins were formed in the material. These structural changes indicate that the high degree of deformation promoted recrystallization of grains even during annealing below the recrystallization temperature. X-ray diffraction analysis revealed the influence of the SPD method and subsequent heat treatment on the phase composition of the printed bronze. The X-ray diffraction patterns clearly show intense reflections of the α-Cu(Al) phase, with the (111) peak being the highest, indirectly indicating the absence of a growth texture (Fig. 2, a). Upon detailed examination, reflections of γ2-Cu9Al4 were also identified, which are only found in samples of the as-printed bronze (Sample 1, Figs. 2, c, d) and samples after multi-directional а b c d e Fig. 1. TEM images of the typical microstructure of Cu-Al-Si-Mn bronze samples. Sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d) and sample 5 (e)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Fig. 2. X-ray diffraction (XRD) patterns of Cu-Al-Si-Mn bronze samples a b c d forging (Sample 2, Figs. 2, c, d). The intensity of the reflections from this phase increased after multidirectional forging, presumably due to the formation of γ2-Cu9Al4 during plastic deformation within the CuAl system. It is known that γ2-Cu9Al4 is formed during mechanical alloying and friction stir processing and decomposes into its components when heated above 180 °C [22]. Therefore, either intermediate annealing before rolling or complete annealing at 400 °C can completely eliminate this phase. In addition, reflections of the β-Cu3Al phase are observed, which are found in samples of the as-printed bronze (Sample 1, Figs. 2, c, d), samples after multi-directional forging (Sample 2, Figs. 2, c, d), and heattreated samples after multi-directional forging (Sample 4, Figs. 2, c, d). One of the key factors affecting the phase composition of samples after SPD is the mechanism of deformation-induced dissolution of intermetallic phases [23]. As a result of SPD, particles of secondary phases dissolve, are fragmented, and refined under the influence of high stresses and a dislocation density close to the theoretical limit [24]. The possibility of precipitation of finely dispersed intermetallic particles is also not excluded, which is also a consequence of SPD and leads to additional strengthening of the alloy. The modification of the material’s structure through severe plastic deformation (SPD), followed by subsequent heat treatment, resulted in changes to the mechanical properties of the bronze, in comparison to the as-printed condition. The conducted investigations clearly demonstrate that the sequential application of SPD methods — namely, multi-directional forging and rolling — causes a substantial increase in the tensile strength of the bronze compared to the initial state obtained by the electron beam additive manufacturing method (Fig. 3, a). In particular, the use of multi-directional forging provided a significant strength increase of 179 MPa, while the rolling process led to an even more pronounced enhancement of mechanical properties, increasing the tensile strength by 515 MPa.
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Following heat treatment via annealing, conducted at a temperature of 400 °C, a further strengthening effect was demonstrated for both types of deformed samples. Notably, for samples that had undergone multidirectional forging, annealing contributed to a further increase in tensile strength by 30 MPa. Regarding the samples after rolling, annealing at the same temperature resulted in a more substantial additional increase in strength, amounting to 43 MPa. The performed analysis also revealed that SPD induces a significant increase in the yield strength of the bronze, relative to the characteristics of the samples formed after additive manufacturing. Multi-directional forging led to a substantial increase in yield strength (by 359 MPa), whereas the application of rolling produced an even more significant increase – 725 MPa Subsequent heat treatment via annealing, also demonstrated a positive influence on this parameter for all types of samples considered after SPD. In particular, for samples pre-processed by multi-directional forging, annealing contributed to a further increase in yield strength by 16 MPa. In the case of samples subjected to rolling, a similar annealing process resulted in a greater additional increase in yield strength, which amounted to 26 MPa. The application of multi-directional forging and rolling led to a reduction in the relative elongation of the bronze samples by 2.6 and 4.5 times, respectively, compared to the as-printed sample (Fig. 3, b). Annealing at 400 °C resulted in a minor increase in relative elongation of 1.1 % for the sample after multidirectional forging and 1.8 % for the sample after rolling. a b Fig. 3. Mechanical properties of Cu-Al-Si-Mn bronze samples Based on the experimental data, it was established that SPD significantly affects the strength and ductility of the printed Cu-Al-Si-Mn bronze samples. An increase in strength and a decrease in ductility are expected for an alloy with an FCC lattice, due to strain hardening mechanisms and structural refinement. Annealing has a minimal impact on the strength of the post-SPD samples, while their ductility improves by approximately 5–13.6 % compared to the deformed state. This is due to the influence on the structure and phase composition of the samples. On the one hand, annealing led to partial recrystallization of the structure and a reduction in the number of crystal lattice defects. On the other hand, the sizes of the structural elements remained at the submicron level. As a result, an increase in ductility and the retention of the material’s strength were achieved. The small increase in strength after annealing is associated with the cooperative contribution from grain boundary and dislocation strengthening mechanisms in the FCC alloy and has been previously noted for alloys with an ultrafine-grained structure [25–29]. In addition, the contribution to solid solution strengthening comes from the deformation-induced dissolution of secondary phase particles [30], as well as the possible precipitation of dispersed phases from the solution as a result of aging. Severe plastic deformation (SPD) through multi-directional forging followed by rolling increased the microhardness of the bronze by 46% and 80%, respectively, compared to the as-printed samples (Fig. 4). Annealing the multi-directionally forged sample at 400°C increased the microhardness from 2.05 GPa to
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 2.37 GPa. Based on the microstructural data and phase composition, the increased hardness is likely due to the dissolution of the primary β-phase and the precipitation of secondary coherent phases within the grain volume. Annealing the rolled sample at 400°C decreased the microhardness from 2.52 GPa to 2.25 GPa.As annealing did not alter the phase composition of the rolled sample, the change in microhardness is attributed solely to structural modifications within the material. During the tribological tests, the change in the coefficient of friction (CoF) over time was recorded (Fig. 5, a), from which the average value was calculated (Fig. 5, b). When the printed bronze sample (Sample 1) was subjected to friction, the CoF remained relatively constant throughout the test at 0.245, with the amplitude of fluctuations not exceeding 0.02. In addition to changing the mechanical properties, multi-directional forging also affected the tribological properties of the investigated bronze. At the start of the test, the CoF for Sample 2 was 0.2, but then decreased to 0.14 within the first 300 seconds. Then the CoF gradually increased to 0.172, and its short-term fluctuations did not exceed 0.05. After rolling (Sample 3), the CoF changed insignificantly; its average value was 0.189, and short-term fluctuations were 0.03. Heat treatment of the sample after multi-directional forging led to an increase in the average CoF to 0.18, and short-term fluctuations to 0.05 (Fig. 5, a, Sample 4). During friction, the CoF monotonically increased from the beginning to the end of the test. Heat treatment of the sample after rolling led to an increase in the average CoF to 0.226, and short-term fluctuations to 0.05 (Fig. 5, a, Sample 5). The change in CoF during friction was not monotonic. At the initial stage, the CoF increased, but then decreased approximately in the second half of the test. Fluctuations in the coefficient of friction reflect dynamic alterations during the sliding friction process. The greater their amplitude, the more unstable the friction process becomes, which may reflect a change in the conditions of contact interaction between the steel ball and the bronze. Based on the obtained results, it can be noted that SPD contributes to a reduction in the CoF compared to the as-printed material. Heat treatment of the samples after SPD led to an increase in the CoF and an increase in the amplitude of its fluctuations. Based on the analysis of optical image data, characteristic regions reflecting the condition of the wear track surface on the bronze samples were identified (Fig. 6). After friction of the as-printed bronze, fine microgrooves formed on the track, oriented along the direction of the friction force, along with dark areas Fig. 4. Microhardness of Cu-Al-Si-Mn bronze samples a b Fig. 5. Coefficients of friction as a function of time during sliding tests (a) and their average values (b)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 containing oxidized material (Fig. 6, a). Signs of plastically displaced material are visible at the edges of the track, indicating substantial plastic deformation of the material. Following friction of the bronze sample with the structure produced by multi-directional forging (Fig. 6, b), fragments of detached wear particles are observed on the surface, in addition to microgrooves and extended regions of oxidized material. Rolling significantly influenced the post-friction condition of the material (Fig. 6, c). The resulting image reveals that the wear track consists of microgrooves without noticeable oxidation or wear debris. After annealing the multi-directionally forged sample (Fig. 6, d), the microgrooves are preserved and become more pronounced; the traces of oxidation approximately coincide with those observed on the deformed Sample 2. Concurrently, individual wear particles are absent. Annealing the rolled sample (Fig. 6, e) had a minimal effect on the morphology of the wear track surface; only a slight increase in its width was observed, suggesting an increase in the wear volume. Fig. 6. Optical images of the wear track surfaces of Cu-Al-Si-Mn bronze samples. Sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d) and sample 5 (e) a b c d e Annealing promotes increased material plasticity; therefore, the amount of wear particles on the heattreated samples after SPD by multi-directional forging decreased. This is attributed to a reduced likelihood of fracture of the ductile bronze material due to deformation induced by the steel counterbody. Following the tribological tests, the surface condition of the steel balls was also investigated (Fig. 7). Signs of adhesive material transfer were observed on the surfaces of all the balls, a characteristic feature of bronze-steel friction pairs [31]. Bronze particles detaching during sliding friction adhered to the surface of the steel counterbody due to adhesive bonds. This process results in the formation of a protective layer, acting as a third body between the sample and the counterbody. The state of this layer is dependent on the wear characteristics of the softer material – the bronze. Previous results indicated that the wear of as-printed bronze results in the formation of microgrooves on its surface accompanied by minor oxidation. Correspondingly, grooves and minor areas with oxidized material are also observed on the surface of the ball (Fig. 7, a). Increased oxidation during friction of bronze Sample 2 and Sample 4 (following multi-directional forging and subsequent annealing) is reflected in the formation of an adherent layer on the counterbody’s surface. Instead of microgrooves, the formation of a mechanical mixture of non-uniform thickness, composed of bronze and oxidized material, is observed (Fig. 7, b, d).
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 a b c d e Fig. 7. Optical images of the steel ball surfaces after sliding against Cu-Al-Si-Mn bronze samples. Sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d) and sample 5 (e) Following friction of Sample 3 and Sample 5 (Fig. 7 c, d), a noticeable layer of bronze, transferred from the wear track, forms on the surface of the balls. Its formation is attributed to a reduction in the oxidation of the copper alloy surface during sliding friction in the examined structural states, which also leads to less pronounced mechanical removal of material from the ball surfaces. To provide a more detailed assessment of the wear track surface condition, energy-dispersive X-ray spectroscopy (EDS) analysis was performed (Figs. 8, 9). As a result of friction, dark layers of material formed, unevenly covering the worn surface of the Cu-Al-Si-Mn alloy samples. EDS analysis revealed that these layers contained an increased concentration of oxygen (Fig. 9). Therefore, these layers consist of a mechanical mixture of bronze and wear particles, which underwent oxidation due to thermomechanical a b c d e Fig. 8. SEM images of the wear track surfaces of Cu-Al-Si-Mn bronze. Sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d) and sample 5 (e)
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 Fig. 9. Elemental mapping of oxygen on the wear track surfaces of Cu-Al-Si-Mn bronze. Sample 1 (a), sample 2 (b), sample 3 (c), sample 4 (d) and sample 5 (e) a b c d e action during sliding friction. During friction, these layers were disrupted by repeated mechanical action from the counterbody. Three-dimensional surface scanning provided detailed data on the morphology of the wear track crosssections, as shown in Fig. 10. The profile shape of each track closely mirrored the spherical configuration of the steel balls used, without any noticeable deviations. Furthermore, the track profiles clearly visualized characteristic surface microroughness formed during frictional interaction and subsequent wear of the material. Quantification of wear, achieved through accurate determination of the cross-sectional area of the obtained profiles, revealed a significant disparity in the wear resistance of the samples. Specifically, printed a b Fig. 10. Cross-sectional profiles (a) and areas (b) of the wear tracks of Cu-Al-Si-Mn bronze
OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 27 No. 3 2025 sample 1 (Fig. 10) exhibited the lowest wear resistance, supported by the highest wear area value of 87,084 μm², significantly exceeding the respective values of the other examined samples. The wear on the sample after multi-side forging (Fig. 10, sample 2) was notably lower, measuring 34,545 μm². The sample’s wear after rolling (Fig. 10, sample 3) was the lowest at 26,732 μm². Following heat treatment after multi-side forging, the wear of the specimen (Fig. 10, sample 4) increased to 40,869 μm². Following heat treatment after rolling, the wear of the sample (Fig. 10, sample 5) increased to 40,124 μm². These experimental data confirm that incremental plastic deformation (IPD) results in reduced bronze wear compared to the printed condition. Heat treatment, in turn, increased the wear of samples relative to their deformed state. Conclusion This study investigated the effect of severe plastic deformation (SPD) on the structural state, mechanical properties, and tribological performance of a Cu-Al-Si-Mn copper alloy fabricated by electron beam additive manufacturing. The experimental results established a correlation between the microstructure, tensile mechanical properties, and tribological behavior of the bronze alloy under unlubricated sliding friction. 1. SPD via multi-side forging and rolling resulted in a high density of dislocations and deformation twins within the material. 2. Annealing at 400 °C following multi-side forging led to partial recrystallization of the material; however, a system of deformation twins remained, demonstrating considerable structural stability. Lowtemperature annealing at 400 °C after rolling resulted in the development of stacking faults, recrystallized submicron grains, and annealing micro-twins within the material. 3. X-ray diffraction analysis indicated that rolling and annealing induced deformation dissolution of secondary phases (β- and γ-phases), resulting in the Cu-Al-Si-Mn alloy becoming a single-phase consisting of the α-phase of face-centered cubic (FCC) copper. 4. Multi-side forging and rolling enhanced the tensile strength of the bronze alloy by factors of 1.43 and 2.24, respectively, while reducing its relative elongation by factors of 2.6 and 4.5 compared to the as-printed condition. 5. Annealing had a minimal impact on the strength of the post-SPD samples, whereas their ductility increased by approximately 5–13.6% relative to the deformed condition. 6. SPD via multi-side forging followed by rolling increased the microhardness of the bronze by 46% and 80%, respectively, compared to the as-printed samples. Annealing the sample at 400 °C after multi-side forging led to a 15.6% increase in microhardness. Annealing the sample at 400 °C after rolling resulted in a 12% decrease in microhardness. 7. Multi-side forging and rolling reduced wear by factors of 2.5 and 3.3, respectively, compared to the alloy in its as-printed state. Annealing increased the wear of the alloy by a factor of 1.5. 8. Based on these findings, a processing route involving a combination of multi-side forging, followed by rolling and low-temperature annealing, is proposed to enhance the mechanical and tribological properties of the Cu-Al-Si-Mn copper alloy. These experimental results provide valuable insights for developing practical strategies aimed at significantly improving the strength properties and wear resistance of bronzes in the CuAl-Si-Mn system, fabricated using electron beam additive manufacturing. References 1. Osintsev O.E., Fedorov V.N. Med’ i mednye splavy: otechestvennye i zarubezhnye marki [Copper and copper alloys. domestic and foreign brands]. 2nd ed., rev. Moscow, Innovatsionnoe mashinostroenie Publ., 2016. 360 p. ISBN 978-5-9907638-3-8. 2. Kolubaev E.A., Rubtsov V.E., Chumaevsky A.V., Astafurova E.G. Micro-, Meso- and macrostructural design of bulk metallic and polymetallic mate-rials by wire-feed electron-beam additive manufacturing. Physical Mesomechanics, 2022, vol. 25 (6), pp. 479–491. DOI: 10.1134/S1029959922060017. 3. Qu S., An X.H., Yang H.J., Huang C.X., Yang G., Zang Q.S., Wang Z.G., Wu S.D., Zhang Z.F. Microstructural evolution and mechanical properties of Cu-Al alloys subjected to equal channel angular pressing. Acta Materialia, 2009, vol. 57 (5), pp. 1586–1601. DOI: 10.1016/j.actamat.2008.12.002.
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