PSI - Issue 65

A.V. Sulitsin et al. / Procedia Structural Integrity 65 (2024) 282–289 A.V. Sulitsin, , S.V. Brusnitsyn, D.O. Levin, D.A. Usov, V.K. Dubrovin / Structural Integrity Procedia 00 (2024) 000–000 A.V. Sulitsin, , S.V. Brusnitsyn, D.O. Levin, D.A. Usov, V.K. Dubrovin / Structural Integrity Procedia 00 (2024) 000–000 and (α+β')-phase, and iron, silicon and manganese are present in the intermetallic compound. Industrial experiments were carried out using a modifier in an amount of 0.06 wt. %. The microstructure of the ingots has been studied. It has been established that when a modifier is added into the melt, the average area of intermetallic compounds in the alloy structure is 361 μm 2 . This is almost two times less than the average area of intermetallic compounds in the structure of the alloy without a modifier introducing into the melt, which is 676 μm 2 . The addition of a nickel-magnesium-cerium ligature in an amount of 0.06 wt. % to a complex alloyed brass with a composition 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb provides effective grinding of intermetallic compounds and excludes the formation of their conglomerates. © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers Keywords: modification; complex alloyed brass; structure; mechanical properties; intermetallic compound; ligature; grain; semi-continuous casting Complex-alloyed brasses have high mechanical properties and are superior to tin bronzes in terms of wear resistance. The main consumers of these alloys are automobile and instrument-making plants. They are used to manufacture parts for axial piston machines, pressure gauge tubes, gearbox synchronizer rings, etc. The required combination of properties in these alloys is provided by the alloyed matrix, which can consist of one, two or more phases, the presence of intermetallics (silicides of transition metals of the 4th period) and lead deposits. It should be noted that a minor change in the chemical composition (content of the main alloying components) can cause a change in the phase composition and, consequently, the properties of the alloy. In the cast state brasses have a structure consisting of α- and β-solid solutions of alloying elements in copper and intermetallics the composition of which depends on the presence of alloying elements. For example, silicon and manganese form the compound Mn 5 Si 3 , additional alloying with iron leads to the formation of a new phase – the intermetallic compound Fe 3 Si. In brass containing nickel, silicon and manganese, dispersion strengthening occurs as a result of the precipitation of intermetallic phases such as Ni 3 (Si, Mn) (γ-phase), NiAl (β'-phase) and Mn 6 Ni 16 Si 7 (θ-phase). The mechanical and operational properties of brass depend to a large extent on the volume fraction of α- and β-phases, the size and morphology of intermetallic compounds, as well as the uniformity of their distribution. When studying the complex-alloyed brass 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb it was established that the particles of intermetallic compounds differ in chemical composition, size and morphology, see, e.g., Li et al. (2017), Li et al. (2016). All large excess phase precipitates, reaching a size of 500 µm or more, in addition to manganese and silicon, are enriched with iron, and therefore their composition can be described by the formula (Mn, Fe) 5 Si 3 . These intermetallics begin to form in the liquid metal and, during crystallization, can come to the surface of the product (for example, when making a synchronizer ring) and crumble, forming micropores, thereby reducing the wear resistance of the material. Small intermetallics of several microns in size contain virtually no iron in their composition, have a stoichiometric composition of Mn 5 Si 3 and are released in the structure after crystallization with a decrease in the solubility of alloying elements in the solid solution with a decrease in temperature. In paper of Kurbatkin et al. (1994) it is shown that the greatest influence on strength characteristics is exerted by the ratio of the volume fraction of α and β-phases in the alloy, as well as the degree of their alloying. Thus, the tensile strength with an increase in the content of the β-phase by 30% increases by 200...300 MPa, and the Brinell hardness increases by 34...54 units. X-ray spectral analysis has established that the alloy with the minimum content of alloying elements has the maximum values of the crystal lattice parameters of the α and β-phases (0.3698 and 0.2949 nm, respectively), and the alloy with the maximum degree of alloying has the minimum crystal lattice parameters of the α and β-phases (0.3688 and 0.2941 nm, respectively). This change in the parameters of the crystal lattices allows us to consider that the solution strengthening of the two-phase matrix is different. It is minimal in less alloyed alloys and increases with the increase in the degree of their alloying. The wear resistance of complex-alloy brasses depends to a large extent on the volume fraction, morphology and size of intermetallics. Research and experience with these alloys have made it possible to formulate the basic requirements for the structure of alloys in terms of mechanical and tribological properties, see, e.g., Hofmann and Skrabal (2017), Hutchinson and Rod (2016), Laws et al. (2015). The structure of 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb and (α+β')-phase, and iron, silicon and manganese are present in the intermetallic compound. Industrial experiments were carried out using a modifier in an amount of 0.06 wt. %. The microstructure of the ingots has been studied. It has been established that when a modifier is added into the melt, the average area of intermetallic compounds in the alloy structure is 361 μm 2 . This is almost two times less than the average area of intermetallic compounds in the structure of the alloy without a modifier introducing into the melt, which is 676 μm 2 . The addition of a nickel-magnesium-cerium ligature in an amount of 0.06 wt. % to a complex alloyed brass with a composition 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb provides effective grinding of intermetallic compounds and excludes the formation of their conglomerates. © 2024 The Authors, Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers Keywords: modification; complex alloyed brass; structure; mechanical properties; intermetallic compound; ligature; grain; semi-continuous casting 1. Introduction Complex-alloyed brasses have high mechanical properties and are superior to tin bronzes in terms of wear resistance. The main consumers of these alloys are automobile and instrument-making plants. They are used to manufacture parts for axial piston machines, pressure gauge tubes, gearbox synchronizer rings, etc. The required combination of properties in these alloys is provided by the alloyed matrix, which can consist of one, two or more phases, the presence of intermetallics (silicides of transition metals of the 4th period) and lead deposits. It should be noted that a minor change in the chemical composition (content of the main alloying components) can cause a change in the phase composition and, consequently, the properties of the alloy. In the cast state brasses have a structure consisting of α- and β-solid solutions of alloying elements in copper and intermetallics the composition of which depends on the presence of alloying elements. For example, silicon and manganese form the compound Mn 5 Si 3 , additional alloying with iron leads to the formation of a new phase – the intermetallic compound Fe 3 Si. In brass containing nickel, silicon and manganese, dispersion strengthening occurs as a result of the precipitation of intermetallic phases such as Ni 3 (Si, Mn) (γ-phase), NiAl (β'-phase) and Mn 6 Ni 16 Si 7 (θ-phase). The mechanical and operational properties of brass depend to a large extent on the volume fraction of α- and β-phases, the size and morphology of intermetallic compounds, as well as the uniformity of their distribution. When studying the complex-alloyed brass 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb it was established that the particles of intermetallic compounds differ in chemical composition, size and morphology, see, e.g., Li et al. (2017), Li et al. (2016). All large excess phase precipitates, reaching a size of 500 µm or more, in addition to manganese and silicon, are enriched with iron, and therefore their composition can be described by the formula (Mn, Fe) 5 Si 3 . These intermetallics begin to form in the liquid metal and, during crystallization, can come to the surface of the product (for example, when making a synchronizer ring) and crumble, forming micropores, thereby reducing the wear resistance of the material. Small intermetallics of several microns in size contain virtually no iron in their composition, have a stoichiometric composition of Mn 5 Si 3 and are released in the structure after crystallization with a decrease in the solubility of alloying elements in the solid solution with a decrease in temperature. In paper of Kurbatkin et al. (1994) it is shown that the greatest influence on strength characteristics is exerted by the ratio of the volume fraction of α and β-phases in the alloy, as well as the degree of their alloying. Thus, the tensile strength with an increase in the content of the β-phase by 30% increases by 200...300 MPa, and the Brinell hardness increases by 34...54 units. X-ray spectral analysis has established that the alloy with the minimum content of alloying elements has the maximum values of the crystal lattice parameters of the α and β-phases (0.3698 and 0.2949 nm, respectively), and the alloy with the maximum degree of alloying has the minimum crystal lattice parameters of the α and β-phases (0.3688 and 0.2941 nm, respectively). This change in the parameters of the crystal lattices allows us to consider that the solution strengthening of the two-phase matrix is different. It is minimal in less alloyed alloys and increases with the increase in the degree of their alloying. The wear resistance of complex-alloy brasses depends to a large extent on the volume fraction, morphology and size of intermetallics. Research and experience with these alloys have made it possible to formulate the basic requirements for the structure of alloys in terms of mechanical and tribological properties, see, e.g., Hofmann and Skrabal (2017), Hutchinson and Rod (2016), Laws et al. (2015). The structure of 70Cu-13Zn-7Mn-5Al-2Fe-2Si-1Pb © 2024 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of MRDMS 2023 organizers 1. Introduction 283 2 2