An alloy, its preparation method, and its uses

Abstract

This invention relates to the field of alloy materials and metallurgical processing technology, and discloses an alloy, its preparation method, and its uses. The alloy comprises the following components by mass percentage: Ni: 22.0–28.0%; Al: 3.0–5.0%; Mn: 1.0–3.5%; Fe: 0.2–1.5%; Cr: 0.1–0.8%; Si: 0.05–0.30%; Ti: 0.05–0.50%; Zr: 0.02–0.20%; the balance being Cu and unavoidable impurities, and the atomic ratio of Ni to Al in the alloy is 2.6–3.3. The tensile strength, yield strength, and elongation of the alloy at room temperature are significantly improved.

Description

Technical Field

[0001] This invention relates to the field of alloy materials and metallurgical processing, specifically to an alloy, its preparation method, and its uses. Background Technology

[0002] Cupronickel alloy with Cu Ni-based alloys possess excellent corrosion resistance, impact resistance, and low magnetic permeability, making them widely used in shipbuilding, marine engineering, precision instruments, and military applications. In traditional aluminum-copper alloy systems, through Cu... Adding a certain amount of Al to Ni alloys forms ordered Ni3Al precipitates, thereby improving the alloy's strength to some extent. These materials are typically produced through smelting. Casting The process route for forging (or extrusion / rolling).

[0003] However, casting The deformation process has the following common problems. First, casting defects such as component segregation, shrinkage cavities, and porosity are easily generated during the solidification process of the ingot, which are difficult to completely eliminate in subsequent plastic deformation. Second, the second phase in the as-cast structure is often coarse, discontinuous, and distributed in a network, especially the brittle phases formed by Si and Ti. This weakens the grain boundary toughness on the one hand, and forms obvious stress concentration sources under tensile or fatigue loads on the other hand, resulting in a significant decrease in plasticity. Third, in order to ensure plasticity and corrosion resistance, the Ni and Al content of traditional aluminum cupronickel is usually limited to a narrow range, resulting in limited room for strength improvement and difficulty in achieving high-temperature performance.

[0004] In recent years, powder metallurgy combined with hot extrusion technology has been introduced into the field of copper alloys. Through gas atomization powder preparation and cladding extrusion, macroscopic shrinkage cavities and segregation in large-size ingots can be avoided, and the microstructure can be significantly refined. However, existing powder metallurgy copper alloys are mostly concentrated on Cu... Cr Zr and other high strength and high conductivity systems (CN110872659A, a high-performance copper alloy) have few systematic designs for high Ni, high Al, multi-element microalloyed cupronickel powder alloys. In particular, there is a lack of alloy systems that can construct heterogeneous structures and achieve synergistic improvement in strength and plasticity by combining composition, powder particle size distribution and hot extrusion process.

[0005] For shaft parts, friction pairs, and structural components with low magnetic permeability that need to withstand high loads and cyclic impacts for extended periods at relatively high temperatures (e.g., 500–600 °C), existing cast or ordinary wrought aluminum cupronickel materials still struggle to achieve a good balance between strength, ductility, and high-temperature performance. Therefore, it is necessary to develop a novel multi-element cupronickel alloy system with alloy composition matched to powder metallurgy processes, which, while maintaining high strength and good ductility, also possesses excellent high-temperature mechanical properties and microstructural stability. Summary of the Invention

[0006] This invention provides an alloy, its preparation method, and its applications, to address the problems in existing aluminum cupronickel and related cupronickel materials, such as the difficulty in eliminating casting defects, coarse grain boundary precipitates that deteriorate plasticity and strength. The problems include difficulty in achieving synergistic plasticity and insufficient high-temperature performance.

[0007] In a first aspect, the present invention provides an alloy comprising, by mass percentage, the following components:

[0008] Ni: 22.0~28.0%;

[0009] Al: 3.0–5.0%;

[0010] Mn: 1.0~3.5%;

[0011] Fe: 0.2–1.5%;

[0012] Cr: 0.1–0.8%;

[0013] Si: 0.05~0.30%;

[0014] Ti: 0.05–0.50%;

[0015] Zr: 0.02~0.20%;

[0016] The balance is Cu and unavoidable impurities.

[0017] Furthermore, the atomic ratio of Ni to Al in the alloy is 2.6 to 3.3.

[0018] In one alternative implementation, at least one of the following is satisfied:

[0019] By mass percentage, it comprises the following components: Ni: 24.0–26.0%, Al: 3.5–4.3%, Mn: 1.5–2.5%, Fe: 0.3–0.8%, Cr: 0.2–0.5%, Si: 0.08–0.20%, Ti: 0.10–0.30%, Zr: 0.05–0.12%;

[0020] The total impurity content is no more than 0.3%;

[0021] The alloy has a tensile strength ≥1000 MPa, a yield strength ≥890 MPa, and / or an elongation ≥12% at room temperature;

[0022] The alloy microstructure includes: a heterogeneous bimodal grain structure consisting of 1–3 μm equiaxed recrystallized grains and 3–8 μm elongated grains; and / or, L12 structure Ni3Al precipitates with an average size of 20–40 nm dispersed within the grains and FeCrNi-rich internal separated phases; and / or, G phase particles with an average size of 0.1–0.5 μm distributed at the grain boundaries.

[0023] Secondly, the present invention also provides a method for preparing the above-mentioned alloy, which includes: atomizing a nickel source, an aluminum source, a manganese source, an iron source, a chromium source, a silicon source, a titanium source, a zirconium source, and a copper source to obtain an alloy powder, wherein the alloy powder contains the components as described above in the alloy by mass percentage.

[0024] In one alternative implementation, at least one of the following is satisfied:

[0025] Before gas atomization, the process also includes heating the nickel source, aluminum source, manganese source, iron source, chromium source, silicon source, titanium source, zirconium source, and copper source.

[0026] The pressure for gas atomization is 1.5–6.0 MPa;

[0027] Argon or an argon / nitrogen mixture is used for gas atomization;

[0028] The alloy powder was sieved to obtain four types of powder with a diameter of 150–75 μm, 75–45 μm, 45–20 μm and less than 20 μm. The four types of powder were mixed in a mass ratio of (10–16):(2–6):(0.5–2):(2–5) to obtain composite powder.

[0029] In one alternative implementation, at least one of the following is satisfied:

[0030] In the step of heating the nickel source, aluminum source, manganese source, iron source, chromium source, silicon source, titanium source, zirconium source and copper source, the heating temperature is 1500-1650 ℃ and / or the heating time is 10-40 min.

[0031] Under an inert atmosphere, nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium, and copper sources are heated.

[0032] The nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium and copper sources are heated by vacuum induction melting or water-cooled copper crucible melting.

[0033] The mixing speed is 20–60 rpm;

[0034] The mixing time is 1–4 hours;

[0035] The method further includes: pressing the composite powder to obtain a blank.

[0036] In one alternative implementation, at least one of the following is satisfied:

[0037] The pressure during the compression of the composite powder is 300–800 MPa;

[0038] The composite powder is compressed by cold isostatic pressing or unidirectional cold pressing.

[0039] The relative density of the obtained billet is not less than 85%;

[0040] In the process of compressing composite powder, the composite powder is filled into a round or square tube with an inner diameter of 20 to 120 mm.

[0041] In the process of pressing composite powder, the composite powder is filled into a round or square tube made of copper alloy or low carbon steel.

[0042] In one alternative implementation, the method further includes heating and pressing the billet.

[0043] In one alternative implementation, at least one of the following is satisfied:

[0044] The billet is heated in an inert atmosphere or vacuum environment;

[0045] Heat the billet to 900–1100 °C;

[0046] The heating time for the billet is 0.5 to 2 hours;

[0047] The extrusion cylinder temperature is 400–520 ℃;

[0048] The extrusion ratio is 9:1 to 20:1;

[0049] The extrusion speed is 2–6 mm / s;

[0050] To obtain extruded bars, tubes, or profiles;

[0051] The nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium, and copper sources are selected from electrolytic copper, nickel granules, aluminum granules, manganese sheets, ferroalloys, ferrochrome, ferrosilicon, sponge titanium, and Zr master alloys.

[0052] Thirdly, the present invention also provides the application of the above-mentioned alloy or the alloy prepared by the above-mentioned alloy preparation method in the fields of shipbuilding, marine engineering, precision instruments or military industry.

[0053] Fourthly, the present invention also provides the application of the above-mentioned alloy or the alloy prepared by the above-mentioned alloy preparation method in the manufacture of heavy-duty high-speed friction pairs, high-temperature shaft parts, marine service structural parts or low magnetic permeability structural parts.

[0054] The Zr master alloy is an Al-3%Zr master alloy (Zr content is 3% by mass). Ferrochrome and ferrosilicon are also master alloys, namely Fe-75%Si (Si content is 75% by mass) and Fe-60%Cr (Cr content is 60% by mass), respectively.

[0055] The technical solution of this invention has the following advantages:

[0056] 1. The alloy provided by this invention, by increasing the Ni content to 22.0-28.0%, the Al content to 3.0-5.0%, and precisely defining the Ni / Al atomic ratio to 2.6-3.3, in Cu... Ni A novel high-Ni, high-Al multi-element cupronickel composition window was constructed on an Al matrix, significantly different from the limited Ni / Al range of traditional aluminum cupronickel. Combined with the synergistic effects of multiple elements such as Mn, Fe, Cr, Si, Ti, and Zr, a multi-scale strengthening combination from solid solution strengthening, precipitation strengthening to grain boundary strengthening was achieved. At room temperature, it exhibits strong and ductile properties with tensile strength ≥1100 MPa, yield strength ≥900 MPa, and elongation ≥15%, while maintaining a tensile strength of approximately 500 MPa and good ductility at 600 °C. Mn provides solid solution strengthening and inhibits excessive high-temperature recrystallization; Fe and Cr enter the L12 precipitate to form a FeCrNi-rich separated phase, enhancing the thermal stability and shear resistance of the precipitate; Zr, through solid solution strengthening and significant inhibition of grain growth, ensures that the alloy maintains fine grains and dispersed precipitates even at 600 °C. The coupling effect of the above elements gives the material excellent strength and resistance to softening at medium and high temperatures.

[0057] 2. The alloy preparation method provided by this invention, through gas atomization powder preparation process, avoids casting defects such as shrinkage cavities, porosity, and macroscopic segregation in large-sized ingots from the source. Rapid solidification and compositional homogenization are achieved at the powder scale, making the G phase formed by Si, Ti, etc., easily broken up and redistributed into fine particles or short strips during subsequent extrusion, forming a dispersed grain boundary G phase band. This effectively reduces stress concentration and brittle fracture tendency, significantly improving plasticity and fracture toughness.

[0058] 3. The alloy preparation method provided by this invention improves powder packing density and reduces pressing defects through carefully designed four-stage particle size composite powder mixing; hot extrusion at 900–1100 °C and an extrusion ratio of 9:1–20:1 yields a heterogeneous bimodal grain structure composed of fine equiaxed grains and elongated deformed grains. Under external load, the soft phase region is prone to plastic deformation, while the strong phase region constrains it, forming a significant back stress field between the two, thus reducing macroscopic stress. The strain curve shows a continuous work hardening capability, achieving a synergistic improvement in high strength and high uniform plasticity.

[0059] 4. The alloy preparation method provided by the present invention utilizes powder metallurgy. Hot extrusion technology can achieve excellent comprehensive mechanical properties in the extruded state without the need for complex multi-step aging treatment. The process is short, repeatable, and easy to scale up and stabilize for industrial production. Attached Figure Description

[0060] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0061] Figure 1 This is a scanning microstructure diagram of the alloy in the extruded state in Example 1 of the present invention;

[0062] Figure 2 This is a transmission electron microscope (TEM) schematic diagram of the L12 precipitate and the separated phase inside the FeCrNi-rich alloy in the extruded state of Example 1 of the present invention. Detailed Implementation

[0063] The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0064] Unless otherwise specified, the experimental steps or conditions in the examples were performed in accordance with conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0065] Example 1

[0066] 1. Alloy composition

[0067] The chemical composition (mass percentage) of the alloy in this embodiment is: Ni 25.0%, Al 3.8%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, with the balance being Cu and unavoidable impurities, the total impurity content not exceeding 0.2%. The atomic ratio of Ni to Al in this composition is approximately 2.9.

[0068] 2. Smelting and gas atomization powder production

[0069] A vacuum induction furnace was used for melting under a high-purity Ar protective atmosphere. First, electrolytic copper and nickel granules were added to the furnace and melted. Then, aluminum granules, manganese flakes, ferroalloys, ferrochrome, ferrosilicon, sponge titanium, and Zr master alloy were added sequentially. The temperature was gradually increased to 1580 °C and held for 20 min to ensure complete melting and homogenization of the alloy components. Subsequently, the atomization system was activated, using 3.0 MPa high-pressure argon gas to atomize the alloy melt flowing from the nozzle, obtaining near-spherical alloy powder. The oxygen content of the powder was tested, and the oxygen content was controlled below 150 ppm.

[0070] 3. Particle size classification and compound powder mixing

[0071] The obtained powder was sieved to obtain four groups of powders: 150–75 μm, 75–45 μm, 45–20 μm, and less than 20 μm. These powders were then compounded at a mass ratio of 13:3:1:3. The mixture was then stirred in a V-type mixer at 30 rpm for 2 hours to ensure thorough and uniform dispersion of the powders of different particle sizes, forming a composite powder with high bulk density.

[0072] 4. Encasing and cold pressing

[0073] A circular tube with an inner diameter of 30 mm is made of copper alloy or low-carbon steel. The composite powder is loaded into the circular tube and pressed into shape under a pressure of 500 MPa to obtain a cladding powder blank with a relative density of approximately 90%.

[0074] 5. Heating and hot extrusion

[0075] The coated powder blank was heated to 1000 °C in a protective atmosphere furnace and held for 1 h to achieve metallurgical bonding between the powders. It was then transferred to an extrusion cylinder preheated to 450 °C and hot-extruded at an extrusion ratio of 12:1 and an extrusion speed of 6 mm / s to obtain round bars with a diameter of approximately 8 mm. The extruded round bars were allowed to cool naturally to room temperature in air without aging treatment.

[0076] 6. Microstructure and Mechanical Properties

[0077] Metallographic observation of the extruded round bar in this embodiment revealed the coexistence of equiaxed fine recrystallized grains (1–3 μm) and elongated grains (3–6 μm) in the matrix, forming a typical heterogeneous bimodal grain structure. Transmission electron microscopy (TEM) showed dispersed L12-structured Ni3Al precipitates (approximately 20–35 nm in size) and separated FeCrNi-rich internal phases within the grains, while fine discontinuous G-phase particles (0.1–0.5 μm) were distributed at the grain boundaries.

[0078] Using a universal testing machine, the tensile specimens were subjected to uniaxial tension at room temperature, and the strain was accurately measured using an extensometer. The results showed that the tensile strength was approximately 1100 MPa, the yield strength was approximately 950 MPa, and the elongation was approximately 21%. When the tensile test was conducted at 600 °C, the tensile strength could still reach approximately 500 MPa, and the material maintained good plasticity, indicating that the alloy of the present invention has excellent strength and structural stability at medium and high temperatures.

[0079] Table 1 Tensile properties of the alloy in Example 1 of the present invention at different temperatures

[0080]

[0081] Example 2

[0082] 1. Alloy composition

[0083] This embodiment adjusts the alloy composition (mass percentage) based on Example 1 to: Ni 23.0%, Al 4.2%, Mn 1.8%, Fe 0.4%, Cr 0.25%, Si 0.10%, Ti 0.15%, Zr 0.06%, with the balance being Cu and unavoidable impurities.

[0084] 2. Smelting and grinding

[0085] The same vacuum induction melting process as in Example 1 was used, with a melting temperature of 1550 °C and a holding time of 15 min. Then, argon gas at 2.5 MPa was used for gas atomization to obtain alloy powder with an average particle size of about 55 μm.

[0086] 3. Compound powder mixing and encapsulation pressing

[0087] After sieving, four groups of powders were obtained: 150–75 μm, 75–45 μm, 45–20 μm, and less than 20 μm. These powders were then compounded and mixed in a mass ratio of 12:4:1:3 in a drum mixer at 25 rpm for 3 hours. Subsequently, the mixture was placed into a copper alloy or low-carbon steel sheath and pressed into shape using a unidirectional cold pressing method at a pressure of 450 MPa, resulting in a sheath blank with a relative density of approximately 86%.

[0088] 4. Heating and hot extrusion

[0089] The cladding billet was heated to 950℃ under a protective atmosphere and held for 1 hour. Then, it was hot extruded at an extrusion ratio of 9:1 and an extrusion speed of 3 mm / s under an extrusion cylinder temperature of 440℃ to obtain round bars with a diameter of 10 mm. After extrusion, the bars were air-cooled to room temperature.

[0090] 5. Mechanical properties

[0091] The room temperature tensile test results (example) are as follows: tensile strength of approximately 1050 MPa, yield strength of approximately 920 MPa, and elongation of approximately 16%; at 600 ℃, the tensile strength is approximately 480 MPa, indicating that the alloy in this embodiment also maintains high strength and good plasticity at high temperatures.

[0092] 6. Microstructure and Mechanical Properties

[0093] Metallographic observation of the extruded round bar in this embodiment revealed the coexistence of equiaxed fine recrystallized grains (2–4.5 μm) and elongated grains (4–10 μm) in the matrix, forming a typical heterogeneous bimodal grain structure. Transmission electron microscopy (TEM) showed dispersed L12-structured Ni3Al precipitates (approximately 25–50 nm in size) and separated FeCrNi-rich internal phases within the grains, while fine discontinuous G-phase particles (0.2–0.8 μm) were distributed at the grain boundaries.

[0094] Example 3

[0095] This embodiment adjusts the alloy composition (mass percentage) based on Example 1 to: Ni 26.0, Al 3.5, Mn 2.0, Fe 0.6, Cr 0.35, Si 0.15, Ti 0.20, Zr 0.10, with the balance being Cu. The Ni / Al atomic ratio is approximately 2.98, close to the upper limit for Ni. The process is the same as in Example 1. The resulting properties are a room temperature tensile strength of approximately 1120 MPa, a yield strength of approximately 958 MPa, and an elongation of approximately 12%; and a tensile strength of approximately 500 MPa at 600 °C.

[0096] Example 4

[0097] This embodiment adjusts the alloy composition (mass percentage) based on Example 1 to: Ni 22.0, Al 3.0, Mn 2.2, Fe 0.4, Cr 0.25, Si 0.10, Ti 0.12, Zr 0.05, with the balance being Cu. The Ni / Al atomic ratio is approximately 2.60, close to the lower limit of the Ni / Al ratio. The process is the same as in Example 1. The resulting properties are a room temperature tensile strength of approximately 1020 MPa, a yield strength of approximately 894 MPa, and an elongation of approximately 17%; and a tensile strength of approximately 460 MPa at 600 °C.

[0098] Comparative Example 1

[0099] To verify the powder metallurgy of this invention The advantages of hot extrusion process and multi-component design are highlighted in this embodiment, which uses the same alloy composition as in Example 1, but employs traditional smelting. Casting A comparison was made using hot extrusion processes. The specific steps are as follows:

[0100] 1. Smelting and casting

[0101] Vacuum induction melting was used to pour the melt into a metal mold to prepare an ingot with a diameter of 65 mm. The ingot was homogenized at 850℃ for 8 h and then air-cooled.

[0102] 2. Hot extrusion

[0103] After the ingot is machined to remove the skin, a billet with a diameter of 30 mm is selected and held at 1000 ℃ for 1 h. Then, it is hot extruded at an extrusion ratio of 12:1 under the condition of 440 ℃ in the extrusion cylinder to obtain a round bar with a diameter of about 8 mm.

[0104] Comparative Example 2

[0105] The only difference from Example 1 is:

[0106] Ni content below the lower limit: Ni 20.0%, Al 3.8%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, balance Cu. Room temperature tensile strength approximately 980 MPa, yield strength approximately 820 MPa, elongation approximately 13%; tensile strength at 600℃ approximately 380 MPa. Insufficient Ni content leads to a reduced L12 phase content, insufficient precipitation strengthening, and significant strength degradation at high temperatures.

[0107] Comparative Example 3

[0108] The only difference from Example 1 is:

[0109] Al content below the lower limit: Ni 25.0%, Al 2.0%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, balance Cu. Room temperature tensile strength is approximately 960 MPa, yield strength approximately 810 MPa, elongation approximately 15%; tensile strength at 600℃ is approximately 375 MPa. The excessively low Al content reduces the L12 phase content, resulting in insufficient precipitation strengthening and thus lower strength and high-temperature performance than those described in this invention.

[0110] Comparative Example 4

[0111] The only difference from Example 1 is:

[0112] Al content above the upper limit: Ni 25.0%, Al 5.5%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, balance Cu. Room temperature tensile strength is approximately 1000 MPa, yield strength approximately 910 MPa, elongation approximately 5%; tensile strength at 600℃ is approximately 400 MPa. Excessive Al content leads to the formation of coarse, discontinuous grain boundary precipitates, severe grain boundary embrittlement, and a significant decrease in plasticity.

[0113] Comparative Example 5

[0114] The only difference from Example 1 is:

[0115] Ni / Al ratio < 2.6: Ni 22.0%, Al 5.2 (≈2.2), Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, balance Cu. Room temperature tensile strength is approximately 1000 MPa, yield strength is approximately 880 MPa, and elongation is approximately 12%; tensile strength at 600℃ is approximately 405 MPa. A low Ni / Al ratio reduces the overall L12 phase integral, decreases high-temperature stability, and significantly lowers the overall performance compared to the window embodiment of this invention.

[0116] Comparative Example 6

[0117] The only difference from Example 1 is:

[0118] Ni / Al ratio > 3.3: Ni 28.0, Al 2.8 (≈3.5), Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.08%, balance Cu. Room temperature tensile strength approximately 1030 MPa, yield strength approximately 920 MPa, elongation approximately 6%; tensile strength at 600℃ approximately 410 MPa. An excessively high Ni / Al ratio leads to the coarse, blocky precipitation of the L12 phase and the growth of the brittle G phase at grain boundaries, resulting in a simultaneous deterioration of both strong ductility and high-temperature strength.

[0119] Comparative Example 7

[0120] The only difference from Example 1 is:

[0121] Both Mn and Zr are below the lower limit: Ni 25.0%, Al 3.8%, Mn 0.3%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.01%, with the balance being Cu. The room temperature tensile strength is approximately 1030 MPa, the yield strength is approximately 870 MPa, and the elongation is approximately 15%; the tensile strength at 600 °C is approximately 350 MPa. When the Mn and Zr contents are low, solid solution strengthening and grain boundary pinning are insufficient, resulting in poor high-temperature microstructure stability; the strength at 600 °C is significantly lower than the range of this invention.

[0122] Comparative Example 8

[0123] The only difference from Example 1 is:

[0124] Both Mn and Zr exceed their upper limits: Ni 25.0%, Al 3.8%, Mn 4.0%, Fe 0.5%, Cr 0.3%, Si 0.12%, Ti 0.18%, Zr 0.25%, with the balance being Cu. The room temperature tensile strength is approximately 1060 MPa, the yield strength is approximately 950 MPa, and the elongation is approximately 6%; the tensile strength at 600℃ is approximately 430 MPa. When Mn and Zr are in excess, the intragranular second phase and enriched particles increase significantly, leading to stress concentration and early damage. Although the strength is high, the plasticity is severely reduced.

[0125] Comparative Example 9

[0126] The only difference from Example 1 is:

[0127] Both Fe and Cr are below the lower limit: Ni 25.0%, Al 3.8%, Mn 2.0%, Fe 0%, Cr 0%, Si 0.12%, Ti 0.18%, Zr 0.08%, with the balance being Cu. The room temperature tensile strength is approximately 1000 MPa, the yield strength is approximately 850 MPa, and the elongation is approximately 18%; the tensile strength at 600 °C is approximately 380 MPa. The significantly low Fe and Cr content indicates a lack of fine, separated phase reinforcement within the L12 phase, resulting in significant softening at high temperatures, and the 600 °C strength is significantly lower than the range specified in this invention.

[0128] Comparative Example 10

[0129] The only difference from Example 1 is:

[0130] Both Fe and Cr are above the upper limit: Ni 25.0%, Al 3.8%, Mn 2.0%, Fe 2.0%, Cr 1.0%, Si 0.12%, Ti 0.18%, Zr 0.08%, with the balance being Cu. The room temperature tensile strength is approximately 1080 MPa, the yield strength is approximately 980 MPa, and the elongation is approximately 8%; the tensile strength at 600℃ is approximately 430 MPa. When the Fe and Cr content is too high, the amount of coarse phase increases within the L12 phase and near the grain boundaries, leading to localized embrittlement and a significant decrease in elongation.

[0131] Comparative Example 11

[0132] The only difference from Example 1 is:

[0133] Both Si and Ti are below the lower limit: Ni 25.0%, Al 3.8%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0%, Ti 0%, Zr 0.08%, with the balance being Cu. The room temperature tensile strength is approximately 900 MPa, the yield strength is approximately 720 MPa, and the elongation is approximately 14%; the tensile strength at 600℃ is approximately 350 MPa. When Si and Ti are low, no G phase is formed, therefore the regulating effect of the L12 phase is insufficient, the precipitated phase size is slightly coarser, resulting in strength and high-temperature performance slightly lower than the range of this invention.

[0134] Comparative Example 12

[0135] The only difference from Example 1 is:

[0136] Both Si and Ti exceed their upper limits: Ni 25.0%, Al 3.8%, Mn 2.0%, Fe 0.5%, Cr 0.3%, Si 0.5%, Ti 0.7%, Zr 0.08%, with the balance being Cu. The room temperature tensile strength is approximately 1060 MPa, the yield strength is approximately 900 MPa, and the elongation is approximately 4%; the tensile strength at 600 °C is approximately 440 MPa. When Si and Ti are in excess, the G phase at the grain boundaries forms a continuous network, leading to a significant decrease in plasticity, and no significant advantage in high-temperature strength.

[0137] Comparative Example 13

[0138] The only difference from Example 1 is:

[0139] Instead of gas atomization, mechanical atomization / debris powder was used, resulting in powder particles with irregular morphology and higher oxygen content. The room temperature tensile strength was approximately 950 MPa, the yield strength approximately 760 MPa, and the elongation approximately 12%; the tensile strength at 600 °C was approximately 330 MPa. Compared to Example 1, both strength and plasticity decreased significantly, with a particularly noticeable reduction in high-temperature strength. Microstructural observation revealed increased porosity and oxide inclusions, and poor interfacial bonding, indicating that the near-spherical, low-oxygen powder obtained by gas atomization is necessary to improve densification, reduce defects, and achieve the high strength, high plasticity, and high-temperature strength required by this invention.

[0140] Comparative Example 14

[0141] The only difference from Example 1 is:

[0142] Without employing a four-stage particle size composite: only a single stage of 45–75 μm, the room temperature tensile strength is approximately 1050 MPa, the yield strength is approximately 900 MPa, and the elongation is approximately 13%; the tensile strength at 600 °C is approximately 430 MPa. The room temperature yield strength is basically close to the level of this invention, but the tensile strength and elongation are both lower than those specified in this invention. Microstructural observation revealed residual porosity and insufficient particle necking, indicating that a reasonable multi-stage particle size composite is beneficial to improving the packing density and sintering densification degree, which is one of the key conditions for achieving the comprehensive performance of this invention.

[0143] Comparative Example 15

[0144] The only difference from Example 1 is:

[0145] Heating below the lower limit (850℃ × 1 h) makes extrusion molding difficult. Under these conditions, powder binding and densification are significantly insufficient. During the experiment, the billet repeatedly cracked and delaminated during extrusion, making it difficult to obtain a complete and dense extruded product, and the mechanical properties could not be stably measured. These results indicate that when the heating temperature is below 900 °C, it is difficult to form a dense structure that meets the requirements for extrusion molding and subsequent service; the lower limit of the heating temperature has a significant process criticality.

[0146] Comparative Example 16

[0147] The only difference from Example 1 is:

[0148] Heating above the upper limit: 1150 ℃ × 1 h, the room temperature tensile strength is approximately 930 MPa, the yield strength is approximately 760 MPa, and the elongation is approximately 13%; the tensile strength at 600 ℃ is approximately 380 MPa. Compared with Example 1, both room temperature strength and high temperature strength are significantly reduced. Microstructural observation shows significant grain growth, coarsening and aggregation of G phase and some second phase particles, and even a tendency for overheating in some areas. This indicates that when the heating temperature exceeds 1100°C, it will cause abnormal coarsening of grains and strengthening phases, resulting in a significant deterioration of overall performance, and the upper limit of the heating temperature also has a clear criticality.

[0149] Comparative Example 17

[0150] The only difference from Example 1 is:

[0151] When the extrusion ratio is below the lower limit (6:1), the room temperature tensile strength is approximately 1000 MPa, the yield strength is approximately 860 MPa, and the elongation is approximately 14%; the tensile strength at 600 °C is approximately 410 MPa. Compared to Example 1, both room temperature and high temperature strengths are reduced, and the elongation still does not reach 15%. Microstructure analysis shows that when deformation accumulation is insufficient, the degree of grain refinement and second-phase dispersion is limited, and the heterogeneous structure and back stress strengthening effect are not obvious. This indicates that when the extrusion ratio is below 9:1, it is difficult to fully utilize the advantages of powder metallurgy + hot extrusion to construct a heterogeneous structure, and the required strength-plasticity synergy and high temperature strength level of this invention cannot be achieved.

[0152] Comparative Example 18

[0153] The only difference from Example 1 is:

[0154] When the extrusion ratio exceeds the upper limit of 25:1, excessive deformation makes forming difficult. Under this condition, the billet experiences excessive strain, easily leading to cracks and folding defects at the extrusion exit and deformation concentration areas during testing. The forming window is extremely narrow, making it difficult to consistently obtain defect-free products. Even when some samples are barely formed, elongated second phases and microcracks along the extrusion direction are visible in their microstructure, significantly reducing the material's reliability and safety in use. This result indicates that an excessively high extrusion ratio is also detrimental to the stable preparation of the alloy of this invention, and the upper limit of the extrusion ratio should be controlled within 20:1.

[0155] Comparative analysis

[0156] The results show that once the content combination of any key element or any process parameter exceeds the scope defined by the present invention, at least one key indicator (e.g., room temperature tensile strength ≥1000 MPa, yield strength ≥890 MPa, elongation ≥12%, or 600 °C tensile strength ≥450 MPa) fails to meet the performance requirements of the present invention, and the corresponding microstructure generally exhibits unfavorable characteristics such as L12 precipitate quantity density or size imbalance, grain boundary G phase coarsening, abnormal grain growth, or increased porosity. This proves that the composition and its scope defined by the present invention have synergistic necessity and unexpected comprehensive performance advantages.

[0157] Compared to Example 1, when changing only a single process parameter—such as replacing gas atomization with non-gas atomization, changing the four-stage composite particle size to a single-stage particle size, or lowering the heating temperature to below 900 °C or raising it to above 1100 °C, or lowering the extrusion ratio to below 9:1 or raising it to above 20:1—at least one key indicator failed to meet the requirements. These results confirm the criticality and non-arbitrary adjustability of the parameter range defined in this invention. Furthermore, these performance deteriorations are directly causally related to the deterioration of the alloy powder's oxygen content and particle morphology, insufficient powder necking and densification, significant coarsening of grains and the second phase, and damage and defect formation caused by insufficient or excessive deformation accumulation.

[0158] As can be seen from the above embodiments, the present invention utilizes a high-Ni, high-Al multi-component design and powder metallurgy. The synergistic effect of heating and hot extrusion processes avoids casting defects while constructing a multi-component cupronickel alloy with fine L12 precipitates, dispersed G phase, and heterogeneous bimodal grain structure, achieving a balance of high strength, high plasticity, and excellent high-temperature mechanical properties. For those skilled in the art, certain adjustments can be made to the specific composition range, powder particle size distribution, and extrusion parameters without departing from the spirit of this invention; all such adjustments should fall within the scope of protection described in this invention.

[0159] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An alloy, characterized in that, It includes the following components by mass percentage: Ni: 22.0~28.0%; Al：3.0～5.0%； Mn: 1.0~3.5%; Fe: 0.2–1.5%; Cr：0.1～0.8%； Si: 0.05~0.30%; Ti: 0.05–0.50%; Zr：0.02～0.20%； The balance is Cu and unavoidable impurities. Furthermore, the atomic ratio of Ni to Al in the alloy is 2.6 to 3.

3. The alloy microstructure includes: a heterogeneous bimodal grain structure consisting of 1–3 μm equiaxed recrystallized grains and 3–8 μm elongated grains; L12 structure Ni3Al precipitates with an average size of 20–40 nm dispersed within the grains and FeCrNi-rich internal separated phases; and G phase particles with an average size of 0.1–0.5 μm distributed at the grain boundaries.

2. The alloy according to claim 1, characterized in that, Meet at least one of the following: By mass percentage, it comprises the following components: Ni: 24.0–26.0%, Al: 3.5–4.3%, Mn: 1.5–2.5%, Fe: 0.3–0.8%, Cr: 0.2–0.5%, Si: 0.08–0.20%, Ti: 0.10–0.30%, Zr: 0.05–0.12%; The total impurity content is no more than 0.3%; The alloy has a tensile strength ≥1000 MPa, a yield strength ≥890 MPa, and an elongation ≥12% at room temperature.

3. The method for preparing the alloy according to claim 1 or 2, characterized in that, include: An alloy powder is prepared by gas atomization of nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium, and copper sources. The alloy powder contains the components as described in claim 1 or 2 by mass percentage. The alloy powder was sieved to obtain four types of powder: 150–75 μm, 75–45 μm, 45–20 μm, and less than 20 μm. These four types of powder were then mixed in a mass ratio of (10–16):(2–6):(0.5–2):(2–5) to obtain a composite powder. The composite powder is pressed to obtain a blank. The billet is heated and extruded. To obtain extruded bars, tubes, or profiles; The specific process for heating the billet is as follows: The billet is heated to 900–1100 °C in an inert atmosphere or vacuum environment for 0.5–2 h. The specific extrusion process is as follows: The extrusion cylinder temperature is 400–520 ℃, the extrusion ratio is 9:1–20:1, and the extrusion speed is 2–6 mm / s.

4. The method for preparing the alloy according to claim 3, characterized in that, Meet at least one of the following: Before gas atomization, the process also includes heating the nickel source, aluminum source, manganese source, iron source, chromium source, silicon source, titanium source, zirconium source, and copper source. The pressure for gas atomization is 1.5–6.0 MPa; Argon or an argon / nitrogen mixture is used for gas atomization.

5. The method for preparing the alloy according to claim 4, characterized in that, Meet at least one of the following: In the step of heating the nickel source, aluminum source, manganese source, iron source, chromium source, silicon source, titanium source, zirconium source and copper source, the heating temperature is 1500~1650 ℃ and the heating time is 10~40 min; Under an inert atmosphere, nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium, and copper sources are heated. The nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium and copper sources are heated by vacuum induction melting or water-cooled copper crucible melting. The mixing speed is 20–60 rpm; The mixing time is 1 to 4 hours.

6. The method for preparing the alloy according to claim 5, characterized in that, Meet at least one of the following: The pressure during the compression of the composite powder is 300–800 MPa; The composite powder is compressed by cold isostatic pressing or unidirectional cold pressing. The relative density of the obtained billet is not less than 85%; In the process of compressing composite powder, the composite powder is filled into a round or square tube with an inner diameter of 20 to 120 mm. In the process of pressing composite powder, the composite powder is filled into a round or square tube made of copper alloy or low carbon steel.

7. The method for preparing the alloy according to claim 6, characterized in that, The nickel, aluminum, manganese, iron, chromium, silicon, titanium, zirconium, and copper sources are selected from electrolytic copper, nickel granules, aluminum granules, manganese sheets, ferroalloys, ferrochrome, ferrosilicon, sponge titanium, and Zr master alloys.

8. The application of the alloy according to claim 1 or 2 or the alloy prepared by the preparation method of any one of claims 3-7 in marine engineering, precision instruments or military fields.

9. The application of the alloy according to claim 1 or 2, or the alloy prepared by the preparation method according to any one of claims 3-7, in ships.

10. The application of the alloy according to claim 1 or 2 or the alloy prepared by the preparation method of any one of claims 3-7 in the manufacture of heavy-duty high-speed friction pairs, high-temperature shaft parts, marine service structural parts or low magnetic permeability structural parts.

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