High-strength corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing and preparation method thereof

Abstract

The application discloses a high-strength corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing and a preparation method thereof, and belongs to the technical field of metal additive manufacturing and marine engineering materials. The high-strength corrosion-resistant nickel-aluminum bronze alloy disclosed by the application comprises, in percentage by weight, Al: 7.7-8.3%, Fe: 3.0-3.5%, Ni: 3.5-4.5%, Mn: 1.0-1.5%, impurity elements: ≤0.5%, and Cu: the balance. In the microstructure of the high-strength corrosion-resistant nickel-aluminum bronze alloy in a cooling deposition state, the matrix is an alpha-Cu (FCC) solid solution phase, the volume fraction of a beta' martensite phase is less than 2%, and there are kappa Ⅱ phases and kappa Ⅲ phases dispersedly distributed in the matrix; the kappa Ⅱ phases and kappa Ⅲ phases are spatially separated and decoupled in the matrix and are respectively nucleated and grown in the matrix. As can be seen, the application can obtain a microstructure with almost no martensite and unique decoupled phase characteristics in the deposition state without subsequent heat treatment, thereby realizing the synergy of high-strength plastic product and excellent seawater corrosion resistance.

Description

Technical Field

[0001] This invention relates to a high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing and its preparation method, belonging to the technical field of metal additive manufacturing and marine engineering materials. Background Technology

[0002] Nickel-aluminum bronze alloys are widely used in the manufacture of key components such as ship propulsion systems, pump and valve systems, marine engineering platforms, and seawater pipeline systems due to their excellent physical and mechanical properties, outstanding resistance to seawater corrosion, and good resistance to biofouling. However, as marine engineering equipment develops towards larger, more complex, and lighter designs, traditional casting processes face limitations such as high mold costs and long production cycles when manufacturing complex thin-walled structures or performing rapid on-site repairs.

[0003] In recent years, metal additive manufacturing technologies, represented by arc additive manufacturing and laser additive manufacturing, have been gradually introduced into the manufacturing and repair of nickel-aluminum bronze components due to their advantages such as high forming efficiency, high material utilization, and great design freedom. However, unlike the slow cooling rate of traditional casting processes, additive manufacturing, especially in underwater environments, has extremely high heating and cooling rates (typically reaching 10²~10³ K / s). These non-equilibrium solidification conditions bring significant microstructural defects and performance bottlenecks to NAB alloys with traditional composition systems.

[0004] Existing commercially available NAB alloys (such as CuAl10Ni5Fe4) are primarily designed for casting or forging processes, and their aluminum (Al) equivalent is typically high. Under the rapid cooling conditions of additive manufacturing, the high-temperature β phase of these high-alkaline-equivalent alloys cannot diffuse to transform into the equilibrium α and κ phases; instead, a shear-type phase transformation occurs, forming a large number of metastable states. Martensitic phase. The presence of this residual martensitic phase leads to the following main technical problems: severe mismatch between strength and plasticity and a significant decrease in corrosion resistance in seawater.

[0005] To address these issues, existing technologies typically employ subsequent high-temperature solution treatment or aging heat treatment processes to eliminate martensite and regulate precipitates. However, heat treatment processes have significant limitations: on the one hand, they increase production costs and manufacturing cycles, and for large, complex, thin-walled components, high-temperature heat treatment can easily cause thermal deformation or cracking; on the other hand, prolonged heat treatment can lead to coarsening of precipitates (such as coarse κⅠ phases in the as-cast structure), which in turn can damage the compactness of the oxide film, resulting in a further reduction in corrosion resistance.

[0006] Therefore, there is an urgent need to develop a nickel-aluminum bronze alloy material specifically for additive manufacturing. Through composition optimization design, it can avoid the formation of martensite in the deposition state and obtain a microstructure with specific decoupled precipitated phase characteristics, thereby achieving a synergy of high strength, high plasticity and excellent corrosion resistance, and eliminating the need for post-heat treatment. Summary of the Invention

[0007] The purpose of this invention is to provide a high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing and its preparation method, overcoming the defects of existing nickel-aluminum bronze alloys in underwater additive manufacturing processes, such as martensite residue, inversion of strength and plasticity, and decreased corrosion resistance caused by rapid cooling. This alloy, through precise composition control and specific process parameters, can achieve a microstructure with almost no martensite and unique decoupled precipitated phase characteristics in a deposited state without subsequent heat treatment, thus achieving a synergistic effect of high strength-plasticity product and excellent seawater corrosion resistance.

[0008] To achieve the above-mentioned technical objectives, the present invention will adopt the following technical solution:

[0009] 1. A high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing, characterized in that the chemical composition of the high-strength, corrosion-resistant nickel-aluminum bronze alloy comprises the following components by weight percentage:

[0010] Al: 7.7–8.3%,

[0011] Fe: 3.0–3.5%,

[0012] Ni: 3.5%–4.5%

[0013] Mn: 1.0~1.5%,

[0014] Impurity elements: ≤0.5%,

[0015] The balance is Cu;

[0016] In the microstructure of the high-strength and corrosion-resistant nickel-aluminum bronze alloy in the cooled deposited state, the matrix is ​​an α-Cu (FCC) solid solution phase. The volume fraction of the martensite phase is less than 2%, and nanoscale κ phase is dispersed in the matrix;

[0017] The nanoscale κ phase includes κII and κIII phases; the κII and κIII phases exhibit a spatially separated and decoupled distribution in the matrix, and each nucleates and grows independently in the matrix;

[0018] The κⅡ phase has a Fe-rich DO3 crystal structure, and the κⅢ phase has a Ni-rich B2 crystal structure.

[0019] 2. The high-strength corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing according to claim 1, characterized in that the chemical composition of the high-strength corrosion-resistant nickel-aluminum bronze alloy is composed of the following components by weight percentage: Al: 8.0%, Fe: 3.2%, Ni: 4.1%, Mn: 1.2%, Cu: balance.

[0020] 3. A method for preparing a high-strength, corrosion-resistant nickel-aluminum bronze alloy as described in claim 1 or 2, characterized in that a laser additive manufacturing process is used to molten nickel-aluminum bronze alloy powder for molding, wherein:

[0021] The chemical composition of nickel-aluminum bronze alloy powder, by weight percentage, consists of the following components:

[0022] Al: 7.7–8.3%,

[0023] Fe: 3.0–3.5%,

[0024] Ni: 3.5%–4.5%

[0025] Mn: 1.0~1.5%,

[0026] Impurity elements: ≤0.5%,

[0027] The balance is Cu;

[0028] The process parameters for laser additive manufacturing are as follows:

[0029] Laser line energy density: 75-225 J / mm;

[0030] Laser power: 1000-3000W;

[0031] Laser spot diameter: 2mm;

[0032] Scanning line speed: 800-1200 mm / min;

[0033] Inter-track overlap rate: 50%.

[0034] 4. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 3, wherein the particle size range of the nickel-aluminum bronze alloy powder is 20-150 μm.

[0035] 5. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 4, characterized in that the laser additive manufacturing process adopts a synchronous powder feeding method, the powder feeding flow rate is 10-30 g / min, the protective gas flow rate is 1.5-2.0 m³ / h, the powder feeding gas flow rate is 0.7-1.5 m³ / h, and the protective gas is argon or a mixed gas with argon as the main component.

[0036] 6. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 5, characterized in that the chemical composition of the nickel-aluminum bronze alloy powder is composed of the following components by weight percentage: Al: 8.0%, Fe: 3.2%, Ni: 4.1%, Mn: 1.2%, Cu: balance.

[0037] 7. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 6, characterized in that the process parameters of the laser additive manufacturing process are: laser power 2000 W; laser spot diameter 2 mm; scanning linear speed 1000 mm / min; inter-channel overlap rate 50%; powder flow rate 20 g / min; protective gas flow rate 1.8 m³ / h; powder feeding gas flow rate 1.0 m³ / h.

[0038] 8. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 7, characterized in that the laser additive manufacturing process adopts a reciprocating scanning method with interlayer rotation of 90°.

[0039] 9. The method for preparing high-strength corrosion-resistant nickel-aluminum bronze alloy according to claim 7, characterized in that both the protective gas and the powder feeding gas are Ar gas.

[0040] 10. An application of the high-strength, corrosion-resistant nickel-aluminum bronze alloy as described in claim 1 or 2, characterized in that the high-strength, corrosion-resistant nickel-aluminum bronze alloy is used in the manufacture and / or repair of large propellers, pumps, valves, heat exchangers, or seawater pipelines in marine engineering equipment. Based on the above-mentioned technical objectives, compared with the prior art, the present invention has the following advantages:

[0041] 1. Excellent synergy of strong plasticity and structural stability: Through precise composition design, this invention completely eliminates the hard and brittle β' martensite phase (volume fraction controlled below 2%) in the deposition state under extremely high cooling rates in additive manufacturing, combined with "decoupled distribution" of nanoscale κ Ⅱ With κ Ⅲ The precipitated phase effectively solves the bottleneck of inverted strength and plasticity in traditional additive manufacturing of NAB alloys. High yield strength and high elongation can be achieved without subsequent heat treatment, and its mechanical properties are significantly superior to those of traditional cast samples.

[0042] 2. Superior Seawater Corrosion Resistance and Heat-Free Advantage: By eliminating martensite as a microscopic galvanic corrosion source and strictly limiting the Fe and Ni contents to ensure the chemical activity of Al in the matrix, a dense, continuous, and stress-crack-free Al2O3 passivation protective film can spontaneously form on the alloy surface. Experimental results show that the self-corrosion current density of the alloy in the deposited state is reduced by about two orders of magnitude compared to the as-cast state, achieving a significant improvement in corrosion resistance, and avoiding the corrosion resistance degradation caused by coarsening of precipitates due to heat treatment in traditional processes.

[0043] 3. Applicability to Large-Size Components and Underwater In-Situ Repair: This invention employs high-power lasers (1000-3000W) and large-spot technology, resulting in high forming efficiency. Its core advantage lies in "possessing final performance in the deposited state." Firstly, for large components: It solves the technological challenge of performing overall high-temperature heat treatment on large, complex, thin-walled marine engineering components due to their enormous size and complex structure. Secondly, for underwater in-situ repair: It fills the technological gap where subsequent heat treatment cannot be implemented after in-situ repair in underwater environments, enabling damaged seawater pumps, valves, propellers, and other components to be repaired on-site and directly put into use, significantly reducing maintenance costs, manufacturing cycles, and downtime losses for marine engineering equipment. Attached Figure Description

[0044] Figure 1 shows scanning electron microscope images of Example 3 of the present invention and Comparative Examples 1, 2 and 3.

[0045] Figure 2 shows the transmission electron microscope (TEM) bright-field image and elemental surface scan of the sample in Example 3 of the present invention.

[0046] Figure 3 shows the tensile fracture surface and tensile properties of Example 3 of the present invention and Comparative Examples 1, 2 and 3.

[0047] Figure 4 shows the electrochemical corrosion performance test results of Example 3 of the present invention and Comparative Examples 1, 2 and 3. Detailed Implementation

[0048] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specifically stated, the relative arrangement, expressions, and values ​​of components and steps set forth in these embodiments do not limit the scope of the present invention. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values.

[0049] The high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing described in this invention is composed of the following components by weight percentage (wt.%): Al: 7.7–8.3%, Fe: 3.0–3.5%, Ni: 3.5–4.5%, Mn: 1.0–1.5%, impurity elements: ≤0.5%, Cu: balance; the microstructure of the high-strength, corrosion-resistant nickel-aluminum bronze alloy in the cooled deposition state is an α-Cu(FCC) solid solution phase. The volume fraction of martensite phase is less than 2%, and nanoscale κ phase is dispersed in the matrix; this invention will cool the deposited state The volume fraction of martensite is strictly limited to below 2% because, based on extensive experimental research, 2% is the critical threshold for maintaining high strength-ductility product and excellent corrosion resistance in the nickel-aluminum bronze composition system of this invention. When the volume fraction of martensite is <2%, the hard and brittle martensite is distributed in isolation in the α matrix at extremely small sizes, without disrupting the continuity of the passivation film. Once the volume fraction exceeds 2%, the martensite phase is highly prone to interconnection, forming galvanic corrosion channels, leading to a sharp increase in self-corrosion current density and a significant reduction in the elongation after fracture of the alloy. This volume fraction can be obtained by observing the sample cross-section using scanning electron microscopy in backscatter mode and statistically averaging the phase area percentages from at least 10 random fields of view using image analysis software. The nanoscale κ phase includes κ Ⅱ Phase and κ Ⅲ Phase; κ Ⅱ Phase and κ Ⅲ The phases exhibit a spatially separated, decoupled distribution within the matrix, each independently nucleating and growing within the matrix; κ Ⅱ The phase has a Fe-rich DO3 crystal structure, κ Ⅲ The phase is a Ni-rich B2 crystal structure.

[0050] To obtain the aforementioned high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing, this invention employs laser additive manufacturing to form nickel-aluminum bronze alloy powder with a particle size range of 20–150 μm. The chemical composition of the nickel-aluminum bronze alloy powder, by weight percentage, consists of the following components: Al: 7.7–8.3%, Fe: 3.0–3.5%, Ni: 3.5–4.5%, Mn: 1.0–1.5%, impurity elements: ≤0.5%, Cu: balance. The process parameters for laser additive manufacturing are: laser line energy density: 75–225 J / mm; laser power: 1000–3000 W; laser spot diameter: 2–4 mm; scanning line speed: 800–1200 mm / min; inter-pass overlap rate: 30%–60%. Furthermore, the laser additive manufacturing process employs a synchronous powder feeding method with a powder flow rate of 10–30 g / min, a protective gas flow rate of 1.5–2.0 m³ / h, and a powder feeding gas flow rate of 0.7–1.5 m³ / h. The protective gas is argon or a mixture primarily composed of argon. Simultaneously, the laser additive manufacturing process uses a reciprocating scanning method with 90° rotation between layers.

[0051] The technical solution of the present invention will be described in detail with reference to the following embodiments and comparative examples.

[0052] Powder Raw Material: The raw material used in this embodiment and comparative example is preferably a pre-alloyed spherical powder prepared by gas atomization, with a particle size range of 20–150 μm. This powder has good sphericity, few satellite spheres, and its flowability meets the requirements of synchronous laser powder feeding. Molding Equipment: A laser melting deposition (LMD) additive manufacturing system equipped with a high-power fiber laser and a synchronous powder feeding system is used. Substrate: Pure copper or cast nickel-aluminum bronze plates with similar composition are used as substrates. The substrates are polished and cleaned to remove oil before printing. To simulate the extremely high cooling rate conditions of underwater additive manufacturing and in-situ surface repair, the printing process is carried out in conjunction with forced water cooling of the substrate or in a partially drained / fully underwater environment.

[0053] Example 1

[0054] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 7.7%, Fe: 3.4%, Ni: 4.3%, Mn: 1.1%, impurity elements: ≤0.5%, balance Cu.

[0055] 2. Fabrication Process. Laser additive manufacturing was employed with parameters set at a high heat input boundary: laser power 3000W, laser spot diameter 2 mm, scanning linear speed 800 mm / min, and inter-pass overlap 50%, resulting in a calculated linear energy density of 225 J / mm². Other parameters included a powder feed rate of 20 g / min, a protective gas (Ar) flow rate of 1.8 m³ / h, and a powder feed gas (Ar) flow rate of 1.0 m³ / h. A reciprocating scanning method was used, with interlayer rotation of 90°. After printing, the sample was rapidly cooled to room temperature, remaining in a cooled deposition state without any subsequent heat treatment.

[0056] 3. Microstructural Characteristics. Microstructural characterization revealed that, due to the Al content in this component being at the lower limit of the scope of protection of this invention, coupled with a high linear energy density, the matrix exhibited a fully grown Widmanstätten α-Cu (FCC) solid solution phase. The microstructure contained hard and brittle... The martensite phase was completely suppressed, with a volume fraction of less than 0.5%. Nanoscale κ phases were dispersed in the matrix. High-resolution transmission electron microscopy (TEM) confirmed that the Fe-rich κⅡ phase and the Ni-rich κⅢ phase exhibited a significant spatially separated and decoupled distribution in the matrix. The two phases nucleated and grew independently in the matrix, and no core-shell coating structure commonly found in traditional additive alloys was found.

[0057] 4. Performance Test Results. Tensile testing at room temperature showed that the sample had a tensile strength of 625 MPa and an elongation after fracture of up to 30%, demonstrating excellent plastic deformation capacity. Impedance spectroscopy results in a 3.5 wt.% NaCl solution showed that the total resistance of the sample was approximately... It has excellent resistance to seawater corrosion.

[0058] Example 2

[0059] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 7.9%, Fe: 3.5%, Ni: 3.6%, Mn: 1.0%, impurity elements: ≤0.5%, and the balance is Cu.

[0060] 2. Preparation process. Laser power: 2500 W; laser spot diameter: 2 mm; scanning linear speed: 1200 mm / min; inter-channel overlap rate: 50%; linear energy density: 125 J / mm. Other process parameters and sample conditions were the same as in Example 1.

[0061] 3. Microstructure characteristics. The microstructure exhibits a fine needle-like Widmanstätten α-Cu matrix. Due to the increased cooling rate caused by high-speed scanning, trace amounts of metastable phases are present at the edges of the needle-like matrix. Statistical analysis using image analysis software shows that... The volume fraction of martensite phase is only about 1.1%, which is below the 2% performance degradation threshold. The nanoscale κII and κIII phases precipitate uniformly within the matrix and do not overlap in three-dimensional space, maintaining a typical spatially separated and decoupled distribution pattern and their own independent growth kinetics.

[0062] 4. Performance Test Results: Testing showed that the alloy, after forming, possesses excellent comprehensive properties, with a tensile strength of 658 MPa, an elongation after fracture of 26%, and a total electrochemical resistance reaching [value missing]. .

[0063] Example 3 (Core Optimal Example of the Invention)

[0064] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 8.0%, Fe: 3.2%, Ni: 4.1%, Mn: 1.2%, impurity elements: ≤0.5%, and the balance is Cu.

[0065] 2. Preparation process. The core process parameters of this invention are as follows: laser power 2000 W, laser spot diameter 2 mm, scanning linear speed 1000 mm / min, inter-channel overlap rate 50%, and linear energy density 120 J / mm. The remaining process parameters and sample conditions are the same as in Example 1.

[0066] 3. Microstructure characteristics. This sample represents the ideal microstructure state of this invention. The matrix is ​​a pure and homogeneous α-Cu (FCC) solid solution phase. Under extensive microscopic field-view statistics, the hard and brittle... With a martensite volume fraction below 1.0%, the martensite transformation range under rapid solidification was successfully avoided. Transmission electron microscopy revealed a large number of extremely fine nanoscale κ phases dispersed within the matrix. Among these, the κⅡ phase (Fe-rich DO3 crystal structure) and the κⅢ phase (Ni-rich B2 crystal structure) exhibited perfect spatial separation and decoupling, with each phase nucleating and growing independently. This unique microstructure maximized the preservation of the chemical reactivity of Al in the matrix, preventing the formation of microscopic anodic galvanic corrosion sources.

[0067] 4. Performance Test Results. Tensile testing at room temperature showed that the sample had a tensile strength of 654 MPa and an elongation after fracture of 27%, achieving an exceptionally good balance of strength and ductility. Impedance spectroscopy in a 3.5 wt.% NaCl solution showed a total resistance of [value missing]. It exhibits excellent resistance to seawater corrosion and passivation.

[0068] Example 4

[0069] 1. Chemical composition. The composition adopts the core ratio of this invention, the same as in Example 3.

[0070] 2. Fabrication process. The forming state under extremely low line energy density was tested: laser power 800 W, laser spot diameter 2 mm, scanning line speed 1500 mm / min, inter-track overlap rate 50%, and the calculated line energy density was only 32 J / mm.

[0071] 3. Microstructural Characteristics. Microstructural characterization revealed that due to the extremely low linear energy density and severely insufficient heat input, obvious unfused voids and cold shut defects appeared inside the molded sample. The extreme cold conditions resulted in an extremely short phase transformation time, leading to a severe shear-type phase transformation within the matrix, resulting in a hard and brittle structure. The martensite volume fraction rises sharply to about 8.5%, far exceeding the 2% performance critical value. At the same time, due to the rapid cooling and numerous matrix defects, the κⅡ and κⅢ phases do not have enough time to fully nucleate and grow, failing to form a typical spatially separated and decoupled distribution, and some regions exhibit a lack of nano-precipitated phases.

[0072] 4. Performance Test Results. The macroscopic mechanical properties are extremely poor, with tensile strength dropping sharply to 450 MPa and elongation after fracture at only 8.5%, exhibiting brittle fracture even under low tensile force. The total electrochemical impedance spectroscopy decreased to... Numerous pore defects and excessive martensitic microanodes together trigger severe pitting and galvanic corrosion, causing the seawater corrosion resistance to fail. This embodiment demonstrates that when the process parameters are below the lower limit defined in this invention, excellent overall performance cannot be obtained.

[0073] Example 5

[0074] 1. Chemical composition. The composition adopts the core formula of this invention, the same as in Example 3.

[0075] 2. Fabrication process. The forming state under extremely high line energy density was tested: laser power 4000 W, laser spot diameter 2 mm, scanning line speed 400 mm / min, inter-track overlap rate 50%, and line energy density up to 600 J / mm.

[0076] 3. Microstructure characteristics. High linear energy density leads to a significantly prolonged molten pool residence time and a huge heat input. Although under these slow cooling conditions... The martensite volume fraction was extremely low (below 0.5%), but the grains were severely coarsened. More critically, the nanoprecipitates, which should have been in a decoupled state, underwent severe ripening and aggregation under prolonged high temperatures. The κⅡ and κⅢ phases adsorbed and encapsulated each other, forming a coarse core-shell structure, completely losing the spatially separated and decoupled distribution characteristics.

[0077] 4. Performance Test Results. The coarse core-shell structure significantly weakens the precipitation strengthening effect and introduces extremely high internal stress at the phase interface. Its tensile strength drops to 580 MPa, and the elongation after fracture is 18%. In corrosive environments, the protective film at the core-shell interface is easily ruptured under stress concentration, resulting in a significant decrease in total resistivity. This embodiment demonstrates that excessive heat input can disrupt the unique decoupled precipitate structure, leading to a sharp drop in corrosion resistance.

[0078] Example 6

[0079] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 8.1%, Fe: 3.3%, Ni: 4.0%, Mn: 1.4%, impurity elements: ≤0.5%, and the balance is Cu.

[0080] 2. Preparation process. Laser power 1000 W, laser spot diameter 2 mm, scanning linear speed 800 mm / min, inter-channel overlap rate 50%, and linear energy density 75 J / mm. Other process parameters and sample conditions are the same as in Example 1.

[0081] 3. Microstructure characteristics and performance test results. The microstructure shows that the matrix consists of α-Cu solid solution. The volume fraction of martensite phase is approximately 1.2%. The nanoscale κII and κIII phases dispersed in the matrix exhibit a spatially separated, decoupled distribution, with each showing distinct independent growth characteristics. Testing revealed a tensile strength of 645 MPa, an elongation after fracture of 26.5%, and a total electrochemical resistance of [value missing]. All indicators performed excellently.

[0082] Example 7

[0083] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 8.2%, Fe: 3.0%, Ni: 4.5%, Mn: 1.5%, impurity elements: ≤0.5%, and the balance is Cu.

[0084] 2. Preparation process. Laser power: 1800 W; laser spot diameter: 2 mm; scanning linear speed: 900 mm / min; inter-channel overlap rate: 50%; linear energy density: 120 J / mm. Other process parameters and sample conditions were the same as in Example 1.

[0085] 3. Microstructural characteristics and performance test results. Within the tissue... The volume fraction of martensite phase was controlled at an extremely low level of 0.8%. The nano-κ precipitates within the matrix exhibited a clear spatially separated and decoupled distribution, with independent nucleation of the two phases, effectively strengthening the α matrix without causing localized stress concentration. Tensile testing showed a tensile strength of 662 MPa, an elongation after fracture of 25%, and a total impedance of [missing value]. .

[0086] Example 8

[0087] 1. Chemical composition. The specific proportions by weight percentage (wt.%) are: Al: 8.3%, Fe: 3.1%, Ni: 3.8%, Mn: 1.3%, impurity elements: ≤0.5%, and the balance is Cu.

[0088] 2. Preparation process. Parameters were set to the upper limit of composition combined with a high scanning speed: laser power 1500 W, laser spot diameter 2 mm, scanning linear speed 1200 mm / min, inter-channel overlap rate 50%, and linear energy density 75 J / mm. Other process parameters and sample conditions were the same as in Example 1.

[0089] 3. Microstructure characteristics and performance test results. This example tested the extreme case of high aluminum content combined with high forming speed. Because the Al content was at the upper limit of the invention and the cooling rate was fast, the grains in the microstructure were significantly refined. The volume fraction of martensite increased to 1.8%, but was still successfully suppressed below the safety threshold of 2%. The nanoscale κⅡ and κⅢ phases in the matrix maintained their spatially separated, decoupled distribution pattern. Performance tests showed that its tensile strength reached 680 MPa, elongation after fracture was 23%, and total resistivity was [missing value]. It achieves a balance between extremely high strength and excellent corrosion resistance.

[0090] Comparative Example 1

[0091] 1. Chemical Composition. The standard commercial grade composition (high aluminum equivalent system) designed for traditional casting processes is adopted, with the following specific ratio: Al: 9.5%, Fe: 4.8%, Ni: 5.0%, Mn: 1.0%, impurity elements: ≤0.5%, balance Cu.

[0092] 2. Fabrication Process. The same core laser additive manufacturing process parameters as in Example 3 were used (laser power 2000 W, scanning linear speed 1000 mm / min, linear energy density 120 J / mm). The sample was allowed to cool naturally after forming and remained in a cooled deposition state.

[0093] 3. Microstructure characteristics and performance test results. Due to the significantly higher aluminum equivalent in this traditional composition system, it is difficult to achieve the extremely high cooling rates in laser additive manufacturing (…). Under non-equilibrium solidification conditions, the high-temperature β phase cannot undergo a diffusion-type transformation, but is instead forced to undergo a shear-type phase transformation, resulting in the retention of metastable states with a volume fraction exceeding 90% in the microstructure. Martensitic phase. Simultaneously, the microstructure failed to form a spatially separated and decoupled distribution of the nanoscale κ phase. Tensile testing showed that although its tensile strength reached 749 MPa, its elongation after fracture dropped to 3.2%, exhibiting extremely high hardness and brittleness with cleavage fracture characteristics. In corrosive environments, the large amount of residual martensitic phase acted as a micro-anode, initiating severe micro-galvanic corrosion between it and the matrix, leading to easy peeling of the oxide film and a significant decrease in the total electrochemical resistance. .

[0094] Comparative Example 2

[0095] 1. Chemical composition and preparation process. The chemical composition is the same as Comparative Example 1 (Al: 9.5% of conventional commercial grade composition), and the forming process parameters are the same as Comparative Example 1 (linear energy density 120 J / mm). Unlike the "deposited state without heat treatment" design of this invention, this sample underwent the post-forming stress relief and aging heat treatment commonly used for NAB alloys (held at 700 ℃ for 2 hours and then air-cooled).

[0096] 2. Microstructure characteristics and performance test results. Microstructure characterization showed that although high-temperature heat treatment released some residual forming stress and promoted the evolution of the microstructure towards an equilibrium state, The volume fraction of the martensitic phase decreased to below 0.1%; however, due to the high Fe and Ni content of the traditional composition and the lack of optimized proportions, the κ precipitate underwent severe growth and polymerization under prolonged high-temperature heat treatment. The κII and κIII phases polymerized and adsorbed each other, evolving into coarse, elongated strips or "core-shell structures" with micrometer-sized particles. This coarse, undecoupled structure not only weakened the nanoprecipitate strengthening effect (tensile strength decreased to 610 MPa, elongation after fracture was 21%), but also introduced extremely high phase transformation and growth stress concentration at the phase interface. In seawater corrosion resistance tests, the coarse phase interface showed… The passivation film is highly susceptible to cracking and peeling under stress, causing its total resistance to drop to a certain level. Corrosion resistance deteriorates exponentially.

[0097] Comparative Example 3

[0098] Traditional commercial casting alloy. Standard grade commercial nickel-aluminum bronze alloys are selected and traditional sand casting process is used (extremely slow cooling rate, <1 K / s).

[0099] Microstructural characteristics and performance test results: Microstructural observation shows that due to the extremely slow cooling of traditional casting, the grains are extremely coarse (reaching the millimeter level), and large rose-shaped κⅠ phases with sizes up to tens of micrometers are prevalent at grain boundaries and within grains, completely lacking the spatially separated and decoupled distribution characteristics of the nanoscale κⅡ and κⅢ phases unique to this invention. Tests show that its tensile strength is only 565 MPa, and its elongation after fracture is 14.5%, with a strength-ductility product significantly lower than that of the embodiments of this invention; at the same time, due to the giant κⅠ phase causing severe discontinuity in the growth of the passivation film, its total electrochemical resistance is only... It is nearly two orders of magnitude lower than the deposited alloy of this invention.

[0100] Comprehensive performance comparison analysis

[0101] To visually demonstrate the rationality of the composition and process window of the present invention and its excellent technical effects, Table 1 summarizes the composition and process parameters of all embodiments and comparative examples, and Table 2 summarizes the key performance comparison data.

[0102] Table 1: Summary of Chemical Composition and Process Parameters of Each Example and Comparative Example

[0103]

[0104] (Note: The balance of each component in the table is Cu, and the impurity elements are ≤0.5%; the laser process uses Ar protective gas and synchronous powder feeding.)

[0105] Table 2: Comparison of microstructure and properties of different NAB alloy samples

[0106]

[0107] Results analysis:

[0108] Summarize:

[0109] (1) Innovative design of composition system Traditional commercial NAB alloys (such as Comparative Example 1) are designed with high aluminum equivalent composition specifically for slow cooling casting. Once exposed to the extremely high heating and cooling rates of additive manufacturing, the high-temperature β phase will inevitably undergo a shear-type phase transformation under rapid non-equilibrium solidification because it does not have time to diffuse. This results in an extremely hard and brittle phase with a volume fraction of over 90% in the deposited state. The martensitic phase induces a severe inversion of strong plasticity (elongation of only 3.2%). This invention breaks with convention by precisely limiting the Al content to a narrow range of 7.7%–8.3%, and by adjusting the ratio of Fe and Ni, fundamentally alters the driving force of the phase transition at the material genome level. Experiments show that when strictly controlled within the composition and process window defined by this invention (Examples 1-3 and 6-8), the cooled deposited state… The volume fraction of martensite was steadily suppressed to below 2%, eliminating the source of hard and brittle phase aggregation and micro-galvanic corrosion.

[0110] (2) Nano-decoupled construction of precipitated phases to synergistically achieve high strength and high corrosion resistance. Even if martensite is eliminated in the traditional process through subsequent heat treatment (Comparative Example 2) or avoided in slow cooling casting (Comparative Example 3), the composition will still precipitate coarse rose-shaped κⅠ phases or undergo coherent destruction during temperature change. Under long-term high-temperature driving, these phases are prone to mutual adsorption and polymerization, evolving into coarse "core-shell coated structures" or micron-sized blocks. These coarse phases will cause severe stress concentration in seawater to passivate film growth, leading to continuous The protective film is highly susceptible to localized cracking and peeling, causing its total impedance value to plummet. Order of magnitude. The key to this invention lies in the spatially separated "decoupled distribution" mechanism of the nanoscale κⅡ (Fe-rich) and κⅢ (Ni-rich) phases. Due to strict limitations on the total Al content and optimized Fe / Ni ratio, the κⅡ and κⅢ phases nucleate and grow independently within the matrix. This unique nanoscale, spatially separated, and non-overlapping morphology (Examples 1-3 and 6-8) significantly improves the matrix yield strength through dispersion precipitation without causing severe stress concentration, maintaining excellent ductility of >20%. Furthermore, the decoupled morphology avoids excessive consumption of Al in the matrix, ensuring the density and stress-free integrity of the passivation film on the alloy surface, thus dramatically enhancing seawater corrosion resistance. This represents a significant leap forward, achieving the goal of surpassing the overall performance of traditional cast samples.

[0111] (3) High tolerance design of process window to support large components and underwater in-situ repair After establishing the optimal composition system and microstructure mechanism, this invention verified the boundary effect of process parameters by systematically adjusting the linear energy density (32~600 J / mm). Under the core process parameters (Example 3, 120 J / mm), the strength-ductility product and corrosion resistance reached the perfect optimal peak. However, when the linear energy density was extremely low (Example 4, 32 J / mm), the extremely low cooling rate induced more than 8% of hard and brittle martensite and hindered the formation of decoupled precipitates, resulting in extremely poor toughness of the molded parts; when the linear energy density was too high (Example 5, 600 J / mm), the high temperature caused the precipitates to be severely matured and evolved into a coarse core-shell coating structure, which completely destroyed the corrosion resistance.

[0112] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing, characterized in that, The chemical composition of the high-strength, corrosion-resistant nickel-aluminum bronze alloy consists of the following components by weight percentage: composition: Al：7.7～8.3%， Fe: 3.0–3.5%, Ni: 3.5%–4.5% Mn: 1.0~1.5%, Impurity elements: ≤0.5%, The balance is Cu; In the microstructure of high-strength, corrosion-resistant nickel-aluminum bronze alloy in the cooled deposited state, the matrix is ​​an α-Cu solid solution phase. The volume fraction of the martensite phase is less than 2%, and nanoscale κ phase is dispersed in the matrix; Nanoscale κ phase includes κ Ⅱ Phase and κ Ⅲ Phase; κ Ⅱ Phase and κ Ⅲ The phases exhibit a spatially separated and decoupled distribution in the matrix, and each nucleates and grows independently in the matrix; κ Ⅱ The phase has a Fe-rich DO3 crystal structure, κ Ⅲ The phase is a Ni-rich B2 crystal structure.

2. The high-strength, corrosion-resistant nickel-aluminum bronze alloy suitable for underwater additive manufacturing according to claim 1, characterized in that, The chemical composition of the high-strength corrosion-resistant nickel-aluminum bronze alloy consists of the following components by weight percentage: Al: 8.0%, Fe: 3.2%, Ni: 4.1%, Mn: 1.2%, Cu: balance.

3. A method for preparing a high-strength, corrosion-resistant nickel-aluminum bronze alloy as described in claim 1 or 2, characterized in that, The process employs laser additive manufacturing to form molten nickel-aluminum bronze alloy powder, wherein: The chemical composition of nickel-aluminum bronze alloy powder, by weight percentage, consists of the following components: Al：7.7～8.3%， Fe: 3.0–3.5%, Ni: 3.5%–4.5% Mn: 1.0~1.5%, Impurity elements: ≤0.5%, The balance is Cu; The process parameters for laser additive manufacturing are as follows: Laser line energy density: 75-225 J / mm; Laser power: 1000-3000W; Laser spot diameter: 2mm; Scanning line speed: 800-1200 mm / min; Inter-track overlap rate: 50%.

4. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 3, characterized in that, The particle size range of nickel-aluminum bronze alloy powder is 20–150 μm.

5. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 4, characterized in that, The laser additive manufacturing process adopts a synchronous powder feeding method with a powder feeding flow rate of 10-30 g / min, a protective gas flow rate of 1.5-2.0 m³ / h, and a powder feeding gas flow rate of 0.7-1.5 m³ / h. The protective gas is argon or a mixed gas with argon as the main component.

6. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 5, characterized in that, The chemical composition of the nickel-aluminum bronze alloy powder consists of the following components by weight percentage: Al: 8.0%, Fe: 3.2%, Ni: 4.1%, Mn: 1.2%, Cu: balance.

7. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 6, characterized in that, The process parameters for laser additive manufacturing are as follows: laser power 2000 W; laser spot diameter 2 mm; scanning line speed 1000 mm / min; inter-pass overlap rate 50%; powder feed rate 20 g / min; protective gas flow rate 1.8 m³ / h; powder feed gas flow rate 1.0 m³ / h.

8. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 7, characterized in that, The laser additive manufacturing process uses a reciprocating scanning method with 90° rotation between layers.

9. The method for preparing the high-strength, corrosion-resistant nickel-aluminum bronze alloy according to claim 7, characterized in that, Ar gas is used for both the protective gas and the powder conveying gas.

10. An application of the high-strength, corrosion-resistant nickel-aluminum bronze alloy as described in claim 1 or 2, characterized in that, High-strength, corrosion-resistant nickel-aluminum bronze alloys are used in the manufacture and / or repair of large propellers, pumps, valves, heat exchangers, or seawater pipelines in marine engineering equipment.

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