Method for sintering densification of aluminum alloy powder chlorinated by membrane rupture activation

Abstract

The application provides a method for aluminum alloy powder chlorination film breaking activation sintering densification, and relates to the technical field of aluminum alloy powder metallurgy.The method introduces trace stannous chloride into 7xxx series aluminum alloy powder, so that the stannous chloride is dispersed and attached to the surface of powder particles;in the subsequent sintering process, the stannous chloride reacts with the aluminum oxide film on the surface of the powder particles to generate volatile AlCl3, the oxidation film is changed from a continuous distribution state into several nanometer scale aluminum oxide particles, the atomic migration ability and sintering neck growth behavior between particles are enhanced, and pressureless efficient full densification sintering of the aluminum alloy powder is realized.The application solves the problem that the sintering densification of 7xxx series aluminum alloy powder is difficult due to the stability of the surface oxidation film, has simple process and simple operation, is low in cost and high in efficiency, can be used for preparing lightweight aluminum alloy structural materials with high density and high strength, and is beneficial to industrial large-scale production and application promotion.

Description

Technical Field

[0001] This invention relates to the technical field of aluminum alloy powder metallurgy, and in particular to a method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder. Background Technology

[0002] High-strength aluminum alloys, due to their low density, high specific strength, excellent fracture toughness, and resistance to stress corrosion, are widely used in high-end equipment manufacturing fields such as aerospace, defense, rail transportation, and new energy. Among them, 7xxx series aluminum alloys, as a typical high-strength wrought aluminum alloy system, have irreplaceable engineering application value in the main load-bearing structural components of aerospace.

[0003] Powder metallurgy technology boasts advantages such as short process flow, fine and uniform microstructure, consistent composition distribution, and flexible forming, showing promising application prospects in the preparation of high-strength aluminum alloys. Nevertheless, powder metallurgy aluminum alloys still face key technological bottlenecks in actual sintering processes. During the preparation, storage, and forming of aluminum alloy powders, a dense and stable alumina film easily forms on their surface. This oxide film significantly hinders atomic diffusion and mass migration during sintering, making it difficult for sintering necks to form and grow between particles. This makes achieving full densification sintering of aluminum alloy powders under pressureless conditions extremely challenging.

[0004] Chinese patent CN106623915B discloses an activated sintering method for aluminum or aluminum alloys. This technology employs a process route involving mixing a mixed salt solution with aluminum powder or aluminum alloy powder, pressing, and sintering. However, this liquid-phase mixing method requires a subsequent drying process before pressing and sintering, resulting in a long process cycle and high energy consumption in the drying process, making large-scale production difficult. Furthermore, if the water adhering to the surface of the mixed salt solution is not completely removed, it can cause hydrogen embrittlement in the sintered product. Additionally, the chlorides in the mixed salt are difficult to decompose and remove, leaving residual salt compounds that deteriorate the mechanical properties of the product, making it difficult to meet the requirements for long-term service life of components. Moreover, without external pressure, the mixed salt needs to be sintered at a high temperature (560-620℃) to function effectively, and its densification effect is highly dependent on the purity of the atmosphere and the process window, making it difficult to achieve stable and fully densified sintering of aluminum alloy powder. Chinese patent CN116851739A suffers from similar issues.

[0005] US Patent 7517492B2 discloses a pressureless sintering method for aluminum or aluminum alloy powders. This technology essentially belongs to the "atmosphere-induced interface activation sintering" approach. Its densification effect is highly dependent on the water vapor partial pressure window, atmosphere purity, and process stability, making it sensitive to fluctuations in process parameters. Atmosphere sintering densification technology relies on the diffusion efficiency and degree of the atmosphere from the outside to the inside of the sintered product. For large-sized parts, this can lead to a "dense outer layer and loose core" microstructure, resulting in uneven component performance and an inability to meet high load-bearing requirements. Therefore, in pressureless sintering applications for 7xxx series high-strength aluminum alloy powders, problems such as a narrow densification window, insufficient batch consistency, and difficulty in achieving stable full densification may still exist.

[0006] Chinese patent CN111906314A discloses a method for simultaneously improving the density and elongation of powder metallurgy materials. This method essentially still relies on external mechanical pressure and specialized hot-pressing equipment to achieve densification. Its densification mechanism mainly stems from plastic deformation and pressure-driven porosity elimination, without addressing the issue of stable oxide film formation on the surface of aluminum alloy powder at the chemical or interfacial level. Without external pressure or for complex-shaped components, this technology is difficult to directly promote, and its complex process, high equipment investment, and limitations on component size and shape are also significant.

[0007] In summary, existing powder metallurgy aluminum alloy densification sintering technologies generally suffer from the following shortcomings: it is difficult to effectively break the stable oxide film on the surface of aluminum alloy powder under pressureless conditions; mass transfer between particles is limited during sintering; densification is insufficient; and it is difficult to balance process complexity or performance stability.

[0008] Therefore, there is an urgent need to develop a new technical solution that can effectively remove the oxide film on the surface of aluminum alloy powder, promote particle diffusion and sintering neck growth, and thus achieve the preparation of highly dense powder metallurgy aluminum alloys under simplified process conditions. Summary of the Invention

[0009] The main objective of this invention is to address the technical problems in the pressureless sintering process of powder metallurgy aluminum alloys, such as insufficient sintering density due to the presence of a dense and stable oxide film on the surface of the aluminum alloy powder, which hinders the synergistic improvement of the material's strength and plasticity. Therefore, a method for chlorination-induced oxide film breaking and activation sintering densification of aluminum alloy powder is proposed, which can solve the aforementioned problems.

[0010] A method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0011] S1. Alloy powder pretreatment: The 7xxx aluminum alloy powder is further crushed and deformed to obtain fine-grained 7xxx aluminum alloy powder.

[0012] S2. Preparation of stannous chloride organic solution: Stannous chloride powder is dissolved in a non-polar, volatile organic solvent to obtain a stannous chloride organic solution;

[0013] S3. Composite powder preparation: The fine-grained 7xxx aluminum alloy powder of S1 and the stannous chloride organic solution of S2 are simultaneously introduced into a dry mechanical mixing process to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the aluminum alloy powder.

[0014] S4. Pressing: The composite powder of S3 is formed by molding or cold isostatic pressing to obtain a pressed green body.

[0015] S5. Activated pressureless sintering: The pressed green billet of S4 is activated pressureless sintering to obtain a fully dense aluminum alloy sintered billet.

[0016] S6, Solution Treatment + Aging Treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment, followed by low-temperature aging treatment, to finally obtain high-performance powder metallurgy aluminum alloy products.

[0017] Optionally, the 7xxx aluminum alloy powder of S1 is one or more of the following: gas atomized powder, air atomized powder, water atomized powder, water-air combined atomized powder, and mechanical alloying powder, with an average particle size of 2-50μm and an oxide film thickness of 3-20nm on the powder surface.

[0018] Optionally, further crushing and deformation refinement of S1 is achieved through high-energy ball milling, with a ball milling speed of 120 r / min and a ball milling time of 6-12 h; the average particle size of the fine 7xxx aluminum alloy powder is 1-30 μm, and the thickness of the oxide film on the powder surface is 2-15 nm.

[0019] Optionally, the average size of the stannous chloride powder in S2 is 30-80 μm, and the non-polar volatile organic solvent includes at least one of acetone, anhydrous isopropanol, and cyclohexane, with a mass ratio of stannous chloride powder to organic solvent of 1:10-1:20.

[0020] Optionally, the dry mechanical mixing of S3 is one or more of the following: rolling ball mill, planetary ball mill, stirring ball mill, vibrating ball mill, V-type mixing, and three-dimensional mixing. The mixing time is 2-48 hours, the ball-to-material ratio is 1:1-20:1, and the mixing atmosphere is one or two of the following: high-purity nitrogen and argon.

[0021] Optionally, the S3 mixture also needs to undergo ultrasonic stirring, centrifugation, and drying; the mass percentage of stannous chloride in the composite powder is 0.05-0.3%, and the thickness of stannous chloride uniformly coated on the surface of the aluminum alloy powder is 10-100 nm.

[0022] Optionally, the molding or cold isostatic pressing pressure of S4 is 150-350MPa, the holding time is 10-180s, and the size of the pressed green body is determined according to the specific size of the mold cavity, with an outer contour diameter of 10-1000mm and a height of 10-2000mm, forming a columnar or block-shaped body.

[0023] Optionally, the activated pressureless sintering of S5 is at least one of vacuum sintering and atmosphere-protected sintering, with a sintering temperature of 550-620℃, a holding time of 0.5-5h, and a vacuum degree of 10. -3 -10 -1 Pa, the atmosphere includes vacuum, high-purity argon or high-purity nitrogen.

[0024] Optionally, during the activated pressureless sintering process of S5, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion to the powder particles. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c The interface activation products reduce the interparticle interface energy barrier, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0025] Optionally, in the solution quenching treatment of S6, the heating rate is 5-20℃ / min, the solution temperature is 450-480℃, and the holding time is 0.5-2h; the water temperature for quenching is 20-60℃; in the aging treatment, the heating rate is 2-10℃ / min, the aging temperature is 120-150℃, and the holding time is 6-24h.

[0026] Optionally, the density of S6's high-performance powder metallurgy aluminum alloy products is 2.80-2.86 g / cm³. 3 It has a density greater than 98%, tensile strength greater than 600 MPa, yield strength greater than 550 MPa, yield strength ratio of 0.85-0.95, elongation of 5.0-15.0%, strength-ductility product of 4.0-10.0 GPa%, and fracture toughness of 15-25 MPa·m. 1 / 2 The impact energy is 2-8J.

[0027] Optionally, S6 is subjected to hot extrusion before solution treatment and aging treatment. The heating rate of hot extrusion is 5-20℃ / min, the temperature of hot extrusion is 350-450℃, and the extrusion ratio is 10:1-200:1.

[0028] Optionally, the high-performance powder metallurgy aluminum alloy product prepared by hot extrusion followed by solution treatment and aging has a density of 2.81-2.88 g / cm³. 3 It has a density greater than 99.5%, tensile strength greater than 650 MPa, yield strength greater than 600 MPa, yield-to-tensile ratio of 0.85-0.95, elongation of 8.0-15.0%, strength-ductility product of 5.0-10.0 GPa%, and fracture toughness of 20-35 MPa·m. 1 / 2 The impact energy is 5-15J.

[0029] Technical principle of the invention:

[0030] This invention introduces trace amounts of stannous chloride onto the surface of aluminum alloy powder, utilizing its low melting point (247°C) to sequentially perform liquid-phase wetting and interfacial activation during sintering heating. When the temperature rises to the melting range of stannous chloride, it transforms into a liquid state and spreads and redistributes along the powder particle surface and interparticle spaces, thereby improving the wetting state between particles and promoting the initial mass transfer process. As the temperature further increases, the chlorine element in the liquid stannous chloride participates in the interfacial activation reaction on the powder particle surface, causing the alumina film to undergo a chlorination reaction and generate easily sublimable and removable AlCl3. Simultaneously, Sn containing Sn, Cl, and O is formed on the particle surface. a Cl b O c The interface activation products are easily decomposed and removed, weakening or destroying the continuous and dense structure of the oxide film, building stable mass transfer channels between particles, thereby promoting atomic diffusion and continuous growth of the sintering neck, and realizing the full densification sintering of aluminum alloy powder under no external pressure conditions.

[0031] The above technical solution has at least the following advantages compared with the existing technology:

[0032] The above-mentioned solution proposes a method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder, which can solve the technical problems in the prior art of insufficient sintering density and difficulty in synergistically improving the strength and plasticity of the material due to the presence of a dense and stable oxide film on the surface of the aluminum alloy powder during the pressureless sintering process.

[0033] The alloy powder pretreatment in this invention involves further crushing and refining the 7xxx aluminum alloy powder, which significantly increases the specific surface area of ​​the powder, thereby improving its surface energy and sintering driving force. Simultaneously, the drastic deformation introduces high-density dislocations and lattice distortion energy into the powder, making the powder in a high-energy state more conducive to atomic diffusion and sintering neck formation during the sintering process. Furthermore, the mechanical crushing action initially disrupts the continuous and dense original oxide film on the powder surface, exposing a fresh metal matrix. This provides more active sites for the subsequent uniform adhesion of stannous chloride and chemical film-breaking reaction, ultimately helping to refine the grains and further enhance the material's strength and toughness through a grain refinement strengthening mechanism.

[0034] This invention overcomes the problem of traditional methods that rely on simple mechanical grinding to destroy the oxide film on the surface of aluminum powder or aluminum alloy powder, which easily leads to the regeneration of a new oxide film and hinders sintering densification. It also breaks through the limitations of mixed salt systems that rely on high-temperature melting to destroy the oxide film. By introducing trace amounts of stannous chloride onto the surface of the aluminum alloy powder, and utilizing its low melting point (247°C), it sequentially exerts liquid-phase wetting and interfacial activation effects during the sintering heating process. This causes the alumina film to undergo a chlorination reaction, generating easily sublimable and removable AlCl3. Simultaneously, Sn containing Sn, Cl, and O is formed on the particle surface. a Cl b O c The interface activation products make it easy to achieve pressureless full densification sintering of particles, simplifying the composition system and process flow, and significantly reducing energy consumption.

[0035] This invention breaks away from the traditional densification technology that relies on pressure-activated sintering. Instead, it employs an activated pressureless sintering process. Through the liquid-phase action of stannous chloride and the activation by chloride ions during sintering, the oxide film is effectively broken down, achieving efficient densification. Simultaneously, the oxide film is transformed from a continuous distribution state into several nanoscale alumina particles, which play a role in dispersion strengthening, further improving the mechanical properties and high-temperature stability of the product, and broadening the application range of aluminum alloy sintered parts.

[0036] The process of this invention is simple and low-cost, making it suitable for industrial application. The 7xxx series powder metallurgy aluminum alloys prepared have higher density and better mechanical properties, meeting the urgent needs of aerospace, artificial intelligence (robotics), low-altitude economy (drones) and other fields for high-strength, high-toughness aluminum alloy materials and lightweight complex parts.

[0037] In summary, compared with existing aluminum alloy powder metallurgy preparation methods, the method of the present invention obtains high-performance powder metallurgy aluminum alloy products through alloy powder pretreatment, preparation of stannous chloride organic solution, preparation of composite powder, pressing and forming, activation pressureless sintering, and solution + aging treatment. Therefore, the method is simple in process, easy to operate, low in cost, and high in efficiency, which is conducive to large-scale industrial production and application. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 Figure 1 shows the SEM microstructure of a 7055 sintered product (with added stannous chloride) prepared by compression molding in a method for chlorination-activated sintering and densification of aluminum alloy powder according to Embodiment 1 of the present invention. Figure 1(a) shows the SEM microstructure of the 7055 sintered product without added stannous chloride, and Figure 2(b) shows the SEM microstructure of the 7055 sintered product with added 0.1% stannous chloride.

[0040] Figure 2 Figure 1 shows the SEM microstructure of a 7055 sintered product (with added stannous chloride) prepared by cold isostatic pressing in a method for chlorination-activated sintering and densification of aluminum alloy powder according to Embodiment 1 of the present invention. Figure (a) is the SEM microstructure of the 7055 sintered product without added stannous chloride, and Figure (b) is the SEM microstructure of the 7055 sintered product with added 0.1% stannous chloride. Detailed Implementation

[0041] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0042] In embodiments of the present invention, words such as "exemplarily," "for example," etc., are used to indicate that something is an example, illustration, or description. Any embodiment or design described as "exemplary" in the present invention should not be construed as being more preferred or advantageous than other embodiments or designs. Specifically, the use of the word "exemplary" is intended to present the concept in a concrete manner. Furthermore, in embodiments of the present invention, the meaning expressed by "and / or" can be both, or either one.

[0043] In the embodiments of the present invention, the terms "image" and "picture" may sometimes be used interchangeably. It should be noted that when the distinction is not emphasized, their intended meanings are consistent.

[0044] In this embodiment of the invention, sometimes a subscript such as W1 may be written in a non-subscript form such as W1. When the difference is not emphasized, the meaning they express is the same.

[0045] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0046] A method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0047] S1. Alloy powder pretreatment: The 7xxx aluminum alloy powder is further crushed and deformed to obtain fine-grained 7xxx aluminum alloy powder.

[0048] S2. Preparation of stannous chloride organic solution: Stannous chloride powder is dissolved in a non-polar, volatile organic solvent to obtain a stannous chloride organic solution;

[0049] S3. Composite powder preparation: The fine-grained 7xxx aluminum alloy powder of S1 and the stannous chloride organic solution of S2 are simultaneously introduced into a dry mechanical mixing process to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the aluminum alloy powder.

[0050] S4. Pressing: The composite powder of S3 is formed by molding or cold isostatic pressing to obtain a pressed green body.

[0051] S5. Activated pressureless sintering: The pressed green billet of S4 is activated pressureless sintering to obtain a fully dense aluminum alloy sintered billet.

[0052] S6, Solution Treatment + Aging Treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment, followed by low-temperature aging treatment, to finally obtain high-performance powder metallurgy aluminum alloy products.

[0053] Specifically, the 7xxx aluminum alloy powder of S1 is one or more of the following: gas atomized powder, air atomized powder, water atomized powder, water-air combined atomized powder, and mechanical alloying powder, with an average particle size of 2-50μm and an oxide film thickness of 3-20nm on the powder surface.

[0054] Specifically, S1 is further crushed and refined by high-energy ball milling at a speed of 120 r / min for 6-12 h; the average particle size of the fine 7xxx aluminum alloy powder is 1-30 μm and the oxide film thickness on the powder surface is 2-15 nm.

[0055] Specifically, the average size of the stannous chloride powder of S2 is 30-80 μm, and the non-polar volatile organic solvent includes at least one of acetone, anhydrous isopropanol, and cyclohexane. The mass ratio of stannous chloride powder to organic solvent is 1:10-1:20.

[0056] Specifically, the dry mechanical mixing of S3 is one or more of the following: rolling ball mill, planetary ball mill, stirring ball mill, vibrating ball mill, V-type mixing, and three-dimensional mixing. The mixing time is 2-48 hours, the ball-to-material ratio is 1:1-20:1, and the mixing atmosphere is one or two of the following: high-purity nitrogen and argon.

[0057] Specifically, the S3 mixture also requires ultrasonic stirring, centrifugation, and drying; the mass percentage of stannous chloride in the composite powder is 0.05-0.3%, and the thickness of stannous chloride uniformly coated on the surface of the aluminum alloy powder is 10-100 nm.

[0058] Specifically, the molding or cold isostatic pressing pressure of S4 is 150-350MPa, the holding time is 10-180s, and the size of the pressed green blank is determined according to the specific size of the mold cavity, which is a columnar or blocky body with an outer contour diameter of 10-1000mm and a height of 10-2000mm.

[0059] Specifically, the activated pressureless sintering of S5 is at least one of vacuum sintering and atmosphere-protected sintering, with a sintering temperature of 550-620℃, a holding time of 0.5-5h, and a vacuum degree of 10. -3 -10 -1 Pa, the atmosphere includes vacuum, high-purity argon or high-purity nitrogen.

[0060] Specifically, during the activated pressureless sintering process of S5, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion to the powder particles. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c The interface activation products reduce the interparticle interface energy barrier, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0061] Specifically, in the solution quenching treatment of S6, the heating rate is 5-20℃ / min, the solution temperature is 450-480℃, and the holding time is 0.5-2h; the water temperature for quenching is 20-60℃; in the aging treatment, the heating rate is 2-10℃ / min, the aging temperature is 120-150℃, and the holding time is 6-24h.

[0062] Specifically, the density of S6's high-performance powder metallurgy aluminum alloy products is 2.80-2.86 g / cm³. 3 It has a density greater than 98%, tensile strength greater than 600 MPa, yield strength greater than 550 MPa, yield strength ratio of 0.85-0.95, elongation of 5.0-15.0%, strength-ductility product of 4.0-10.0 GPa%, and fracture toughness of 15-25 MPa·m. 1 / 2 The impact energy is 2-8J.

[0063] Specifically, S6 undergoes hot extrusion before solution treatment and aging. The heating rate of hot extrusion is 5-20℃ / min, the temperature of hot extrusion is 350-450℃, and the extrusion ratio is 10:1-200:1.

[0064] Specifically, the high-performance powder metallurgy aluminum alloy product prepared by hot extrusion followed by solution treatment and aging has a density of 2.81-2.88 g / cm³. 3 It has a density greater than 99.5%, tensile strength greater than 650 MPa, yield strength greater than 600 MPa, yield-to-tensile ratio of 0.85-0.95, elongation of 8.0-15.0%, strength-ductility product of 5.0-10.0 GPa%, and fracture toughness of 20-35 MPa·m. 1 / 2 The impact energy is 5-15J.

[0065] Example 1

[0066] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0067] S1. Alloy Powder Pretreatment: The 7055 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 8.3 wt.% Zn, 2.5 wt.% Cu, 2.3 wt.% Mg, and the balance being Al. Its average particle size is 10 μm, and the oxide film thickness on the powder surface is 3 nm. The 7055 aluminum alloy powder is further crushed and refined by planetary ball milling at a ball-to-powder ratio of 5:1 for 12 hours, resulting in fine-grained 7055 aluminum alloy powder with an average particle size of 8 μm and an oxide film thickness of 3 nm.

[0068] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 45 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:19. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0069] S3. Preparation of composite powder: The fine-grained 7055 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing under high-purity nitrogen atmosphere, with a ball-to-powder ratio of 2:1 and a mixing time of 12 hours to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the 7055 aluminum alloy powder; the mass percentage of stannous chloride in the composite powder is 0.1%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 15 nm;

[0070] S4. Compression forming: The composite powder of S3 is formed by bidirectional compression molding at a pressure of 300MPa and a holding time of 180s to obtain a cylindrical compressed green body with a diameter of 20mm and a height of 10mm.

[0071] SEM microstructure of the 7055 sintered product (with added stannous chloride) prepared by compression molding in Example 1 is as follows: Figure 1 (a) Figure 1 As shown in (b), the SEM microstructure of the 7055 sintered product (with added stannous chloride) prepared by cold isostatic pressing in Example 1 is as follows: Figure 2 (a) Figure 2 As shown in (b), Figure 2 The density of the microstructure sintered sample formed by cold isostatic pressing is relatively... Figure 1 The molding performance was high, with no obvious pores between particles and no continuous oxide film residue, indicating that chlorination activation effectively promoted metallurgical bonding.

[0072] S5. Activated Pressureless Sintering: The pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature of 590℃, holding time of 4h, to obtain fully dense aluminum alloy sintered billet;

[0073] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0074] S6. Solution treatment + aging treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h; the water quenching temperature is 40℃; then it is subjected to low-temperature aging treatment with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0075] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.84 g / cm³. 3The density is 99%, the tensile strength is 615 MPa, the yield strength is 560 MPa, the yield-to-tensile ratio is 0.911, the elongation is 7.6%, the strength-ductility product is 4.674 GPa%, and the fracture toughness is 18 MPa·m. 1 / 2 The impact energy is 4J.

[0076] Comparative Example 1

[0077] For Example 1, the amount of stannous chloride added in S2 was changed to 0 wt.%, and the other steps were the same as in Example 1.

[0078] Performance testing revealed that the sintered body had a low density of only 2.63 g / cm³ due to the lack of an activating film-breaking agent. 3 The density is 92% (theoretical density is 2.86 g / cm³). 3 The tensile strength is 420 MPa, the yield strength is 265 MPa, the yield ratio is 0.631, the elongation is 2.5%, the strength-ductility product is 1.050 GPa%, and the fracture toughness is 8 MPa·m. 1 / 2 The impact energy is 1.5 J. Compared with Example 1, it is shown that the low-density sintered blank without the addition of stannous chloride is difficult to achieve sintering densification, which in turn leads to a significant reduction in mechanical properties.

[0079] Example 2

[0080] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0081] S1. Alloy Powder Pretreatment: The 7055 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 8.3 wt.% Zn, 2.5 wt.% Cu, 2.3 wt.% Mg, and the balance being Al. Its average particle size is 25 μm, and the oxide film thickness on the powder surface is 5 nm. The 7055 aluminum alloy powder is further crushed and refined by planetary ball milling at a ball-to-powder ratio of 5:1 for 12 hours, resulting in fine-grained 7055 aluminum alloy powder with an average particle size of 20 μm and an oxide film thickness of 3 nm.

[0082] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 50 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:19. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0083] S3. Preparation of composite powder: The fine-grained 7055 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing under high-purity nitrogen atmosphere, with a ball-to-powder ratio of 2:1 and a mixing time of 12 hours to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the 7055 aluminum alloy powder; the mass percentage of stannous chloride in the composite powder is 0.1%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 35 nm.

[0084] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 150MPa and the holding time is 180s to obtain a cylindrical green body with a diameter of 60mm and a height of 100mm.

[0085] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature of 600℃, holding time of 2h, to obtain fully dense aluminum alloy sintered billet;

[0086] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0087] S6. Solution treatment + aging treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h; the water quenching temperature is 40℃; then it is subjected to low-temperature aging treatment with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0088] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.85 g / cm³. 3 The density is 99%, the tensile strength is 630 MPa, the yield strength is 585 MPa, the yield-to-tensile ratio is 0.929, the elongation is 6.3%, the strength-ductility product is 3.969 GPa%, and the fracture toughness is 16 MPa·m.1 / 2 The impact energy is 3.5J.

[0089] Example 3

[0090] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0091] S1. Alloy Powder Pretreatment: The 7055 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 8.3 wt.% Zn, 2.5 wt.% Cu, 2.3 wt.% Mg, and the balance being Al. Its average particle size is 45 μm, and the oxide film thickness on the powder surface is 5 nm. The 7055 aluminum alloy powder is further crushed and refined by planetary ball milling at a ball-to-powder ratio of 5:1 for 18 hours, resulting in fine-grained 7055 aluminum alloy powder with an average particle size of 35 μm and an oxide film thickness of 3 nm.

[0092] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 60 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:19. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0093] S3. Preparation of composite powder: The fine-grained 7055 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing under high-purity nitrogen atmosphere, with a ball-to-powder ratio of 2:1 and a mixing time of 12 hours to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the 7055 aluminum alloy powder; the mass percentage of stannous chloride in the composite powder is 0.1%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 60 nm.

[0094] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 180MPa and the holding time is 180s, resulting in a cylindrical green body with a diameter of 60mm and a height of 120mm.

[0095] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature is 615℃, holding time is 1h, and fully dense aluminum alloy sintered billet is obtained;

[0096] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0097] S6. Solution treatment + aging treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h; the water quenching temperature is 40℃; then it is subjected to low-temperature aging treatment with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0098] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.83 g / cm³. 3 The density is 99%, the tensile strength is 605 MPa, the yield strength is 550 MPa, the yield ratio is 0.909, the elongation is 7.3%, the strength-ductility product is 4.417 GPa%, and the fracture toughness is 17 MPa·m. 1 / 2 The impact energy is 3.8J.

[0099] Example 4

[0100] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0101] S1. Alloy Powder Pretreatment: The 7055 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 8.3 wt.% Zn, 2.5 wt.% Cu, 2.3 wt.% Mg, and the balance being Al. Its average particle size is 25 μm, and the oxide film thickness on the powder surface is 5 nm. The 7055 aluminum alloy powder is further crushed and refined by planetary ball milling at a ball-to-powder ratio of 5:1 for 12 hours, resulting in fine-grained 7055 aluminum alloy powder with an average particle size of 20 μm and an oxide film thickness of 3 nm.

[0102] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 50 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:20. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0103] S3. Preparation of composite powder: The fine-grained 7055 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing under high-purity nitrogen atmosphere, with a ball-to-powder ratio of 2:1 and a mixing time of 12 hours to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the 7055 aluminum alloy powder; the mass percentage of stannous chloride in the composite powder is 0.1%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 35 μm;

[0104] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 150MPa and the holding time is 180s to obtain a cylindrical compressed green body with a diameter of 60mm and a height of 100mm.

[0105] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature of 600℃, holding time of 2h, to obtain fully dense aluminum alloy sintered billet;

[0106] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0107] S6. Solution treatment + aging treatment: The fully dense aluminum alloy sintered billet of S5 is hot extruded at a temperature of 390℃ and an extrusion ratio of 16:1. Then, it is first subjected to solution water quenching treatment with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h. The water quenching temperature is 40℃. Then, it is subjected to low-temperature aging treatment with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0108] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.86 g / cm³. 3 The density is 99.8%, the tensile strength is 750 MPa, the yield strength is 696 MPa, the yield-to-tensile ratio is 0.928, the elongation is 11.9%, the strength-ductility product is 8.925 GPa%, and the fracture toughness is 30 MPa·m. 1 / 2 The impact energy is 11J.

[0109] Comparative Example 2

[0110] For Example 4, the amount of stannous chloride added in S2 was changed to 0 wt.%, and the other steps were the same as in Example 4.

[0111] Performance tests showed a tensile strength of 642 MPa, a yield strength of 554 MPa, a yield-to-tensile ratio of 0.863, an elongation of 9.6%, and a density of 2.78 g / cm³. 3 The density is 97.2%, the strength-ductility product is 6.163 GPa%, and the fracture toughness is 21 MPa·m. 1 / 2 The impact energy is 6J. Compared with Example 4, it is shown that the low-density sintered billet without stannous chloride needs to have its porosity eliminated during the subsequent hot extrusion process, resulting in mechanical properties that are inferior to the extrusion performance of the sintered billet with stannous chloride.

[0112] Example 5

[0113] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0114] S1. Alloy Powder Pretreatment: The 7055 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 6.0 wt.% Zn, 2.0 wt.% Cu, 2.8 wt.% Mg, and the balance being Al; its average particle size is 25 μm, and the oxide film thickness on the powder surface is 5 nm; the 7055 aluminum alloy powder is further crushed and refined by planetary ball milling with a ball-to-powder ratio of 5:1 and a milling time of 12 h to obtain fine-grained 7055 aluminum alloy powder with an average particle size of 20 μm; the oxide film thickness on the surface of the fine-grained 7055 aluminum alloy powder is 3 nm;

[0115] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 50 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:20. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0116] S3. Preparation of composite powder: The fine-grained 7055 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing under high-purity nitrogen atmosphere, with a ball-to-powder ratio of 1:1 and a mixing time of 24 hours to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the 7055 aluminum alloy powder; the mass percentage of stannous chloride in the composite powder is 0.15%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 50 nm.

[0117] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 150MPa and the holding time is 180s to obtain a cylindrical compressed green body with a diameter of 60mm and a height of 100mm.

[0118] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature of 600℃, holding time of 2h, to obtain fully dense aluminum alloy sintered billet;

[0119] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0120] S6. Solution treatment + aging treatment: The fully dense aluminum alloy sintered billet of S5 is hot extruded at a temperature of 390℃ and an extrusion ratio of 16:1. Then, it is first subjected to solution water quenching treatment with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h. The water quenching temperature is 40℃. Then, it is subjected to low-temperature aging treatment with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0121] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.81 g / cm³. 3The density is 99%, the tensile strength is 658 MPa, the yield strength is 613 MPa, the yield ratio is 0.932, the elongation is 10.2%, the strength-ductility product is 6.712 GPa%, and the fracture toughness is 26 MPa·m. 1 / 2 The impact energy is 8.5J.

[0122] Example 6

[0123] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0124] S1. Alloy Powder Pretreatment: The 7075 aluminum alloy powder is a water-air co-atomized powder, with the following elemental mass percentages: 6.0 wt.% Zn, 2.0 wt.% Cu, 2.8 wt.% Mg, and the balance being Al; its average particle size is 13 μm, and the oxide film thickness on the powder surface is 5 nm; the 7075 aluminum alloy powder is further crushed and refined by planetary ball milling, with a ball-to-powder ratio of 5:1 and a milling time of 10 h, to obtain fine-grained 7075 aluminum alloy powder with an average particle size of 10 μm; the surface oxide film thickness of the fine-grained 7075 aluminum alloy powder is 3 nm;

[0125] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 40 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:20. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0126] S3. Preparation of composite powder: The fine-grained 7075 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing. The mixing atmosphere is high-purity nitrogen, the ball-to-powder ratio is 1:1, and the mixing time is 24h. The aluminum alloy powder is coated to obtain a composite powder in which stannous chloride is uniformly coated on the surface of 7075 aluminum alloy powder. The mass percentage of stannous chloride in the composite powder is 0.15%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 30nm.

[0127] S4. Compression molding: The composite powder of S3 is formed by bidirectional compression molding at a pressure of 300MPa and a holding time of 60s to obtain a cylindrical green body with a diameter of 20mm and a height of 15mm.

[0128] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature of 590℃, holding time of 3h, to obtain fully dense aluminum alloy sintered billet;

[0129] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0130] S6. Solution treatment + aging treatment: The fully dense aluminum alloy sintered billet of S5 is directly heat treated; firstly, solution water quenching is performed, with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h; the water quenching temperature is 40℃; then, low-temperature aging treatment is performed, with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0131] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.79 g / cm³. 3 The density is 98.2%, the tensile strength is 585 MPa, the yield strength is 530 MPa, the yield-to-tensile ratio is 0.906, the elongation is 6.5%, the strength-ductility product is 3.80 GPa%, and the fracture toughness is 16 MPa·m. 1 / 2 The impact energy is 3.6J.

[0132] Example 7

[0133] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0134] S1. Alloy Powder Pretreatment: The 7075 aluminum alloy powder is a water-atomized powder, with the following elemental mass percentages: 6.0 wt.% Zn, 2.0 wt.% Cu, 2.8 wt.% Mg, and the balance being Al; its average particle size is 45 μm, and the oxide film thickness on the powder surface is 15 nm; the 7075 aluminum alloy powder is further crushed and refined by planetary ball milling, with a ball-to-powder ratio of 5:1 and a milling time of 15 h, to obtain fine-grained 7075 aluminum alloy powder with an average particle size of 40 μm; the surface oxide film thickness of the fine-grained 7075 aluminum alloy powder is 8 nm;

[0135] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 60 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:20. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0136] S3. Preparation of composite powder: The fine-grained 7075 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing. The mixing atmosphere is high-purity nitrogen, the ball-to-powder ratio is 1:1, and the mixing time is 24 hours. The aluminum alloy powder is coated to obtain a composite powder in which stannous chloride is uniformly coated on the surface of the 7075 aluminum alloy powder. The mass percentage of stannous chloride in the composite powder is 0.2%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 80 nm.

[0137] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 180MPa and the holding time is 180s to obtain a cylindrical green body with a diameter of 60mm and a height of 100mm.

[0138] S5. Activated Pressureless Sintering: The cylindrical pressed green body from S4 is subjected to activated pressureless sintering, specifically vacuum sintering. The vacuum degree during the vacuum sintering process is 10. -3 Pa, sintering temperature is 610℃, holding time is 3h, and fully dense aluminum alloy sintered billet is obtained;

[0139] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0140] S6. Solution treatment + aging treatment: The fully dense aluminum alloy sintered billet of S5 is hot extruded at a temperature of 400℃ and an extrusion ratio of 20:1. Then, it is first subjected to solution water quenching treatment at a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h. The water quenching temperature is 40℃. Then, it is subjected to low-temperature aging treatment at a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0141] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.82 g / cm³. 3 The density is 99.5%, the tensile strength is 645 MPa, the yield strength is 590 MPa, the yield-to-tensile ratio is 0.915, the elongation is 9.5%, the strength-ductility product is 6.128 GPa%, and the fracture toughness is 24 MPa·m. 1 / 2 The impact energy is 7.5J.

[0142] Example 8

[0143] This embodiment provides a method for chlorination-activated sintering and densification of aluminum alloy powder, comprising the following steps:

[0144] S1. Alloy Powder Pretreatment: The 7075 aluminum alloy powder is an atomized powder with the following elemental mass percentages: 6.0 wt.% Zn, 2.0 wt.% Cu, 2.8 wt.% Mg, and the balance being Al; its average particle size is 30 μm, and the oxide film thickness on the powder surface is 5 nm; the 7075 aluminum alloy powder is further crushed and refined by planetary ball milling with a ball-to-powder ratio of 5:1 and a milling time of 12 h to obtain fine-grained 7075 aluminum alloy powder with an average particle size of 25 μm; the oxide film thickness on the surface of the fine-grained 7075 aluminum alloy powder is 3 nm;

[0145] S2. Preparation of stannous chloride organic solution: Stannous chloride powder with an average size of 50 μm was dissolved in anhydrous acetone solution. The mass ratio of stannous chloride powder to organic solvent was 1:20. The solution was magnetically stirred at 20°C for 1 h to obtain a uniformly mixed acetone suspension containing stannous chloride.

[0146] S3. Preparation of composite powder: The fine-grained 7075 aluminum alloy powder of S1 and the acetone suspension containing stannous chloride of S2 are simultaneously introduced into a V-type mixer for mixing. The mixing atmosphere is high-purity nitrogen, the ball-to-powder ratio is 1:1, and the mixing time is 24 hours. The aluminum alloy powder is coated to obtain a composite powder in which stannous chloride is uniformly coated on the surface of the 7075 aluminum alloy powder. The mass percentage of stannous chloride in the composite powder is 0.1%, and the thickness of the stannous chloride uniformly coated on the surface of the aluminum alloy powder is 40 nm.

[0147] S4. Compression forming: The composite powder of S3 is loaded into a rubber sleeve and formed by cold isostatic pressing (CIP). The cold isostatic pressing pressure is 180MPa and the holding time is 180s to obtain a cylindrical green body with a diameter of 60mm and a height of 100mm.

[0148] S5. Activated pressureless sintering: The cylindrical pressed green billet of S4 is activated pressureless sintering, specifically high-purity nitrogen protection sintering, sintering temperature is 590℃, holding time is 3h, to obtain fully dense aluminum alloy sintered billet.

[0149] During the activated pressureless sintering process, when the temperature rises to 230-250℃, the stannous chloride melts and transforms into a liquid state. The corresponding liquid stannous chloride spreads and redistributes along the surface and interparticle spaces of the powder particles, providing liquid-phase wetting and mass transfer promotion. As the temperature further increases to the sintering temperature range, in the presence of liquid stannous chloride, chlorine participates in the interfacial activation reaction on the powder particle surface, weakening or destroying the oxide film structure on the aluminum alloy powder surface and generating easily decomposed and removable Sn. a Cl b O c Interface activation products reduce interparticle interface energy barriers, promote atomic diffusion and sintering neck growth, and achieve sintering densification.

[0150] S6. Solution treatment + aging treatment: The fully dense aluminum alloy sintered billet of S5 is directly heat treated; firstly, solution water quenching is performed, with a heating rate of 10℃ / min, a solution temperature of 475℃, and a holding time of 2h; the water quenching temperature is 40℃; then, low-temperature aging treatment is performed, with a heating rate of 5℃ / min, an aging temperature of 120℃, and a holding time of 24h, finally obtaining a high-performance powder metallurgy aluminum alloy product.

[0151] The density of the high-performance powder metallurgy aluminum alloy product prepared in this embodiment is 2.79 g / cm³. 3 The density is 98.2%, the tensile strength is 585 MPa, the yield strength is 530 MPa, the yield-to-tensile ratio is 0.906, the elongation is 6.3%, the strength-ductility product is 3.786 GPa%, and the fracture toughness is 15 MPa·m. 1 / 2 The impact energy is 3.2J.

[0152] The above-mentioned solution proposes a method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder, which can solve the technical problems in the prior art of insufficient sintering density and difficulty in synergistically improving the strength and plasticity of the material due to the presence of a dense and stable oxide film on the surface of the aluminum alloy powder during the pressureless sintering process.

[0153] The alloy powder pretreatment in this invention involves further crushing and refining the 7xxx aluminum alloy powder, which significantly increases the specific surface area of ​​the powder, thereby improving its surface energy and sintering driving force. Simultaneously, the drastic deformation introduces high-density dislocations and lattice distortion energy into the powder, making the powder in a high-energy state more conducive to atomic diffusion and sintering neck formation during the sintering process. Furthermore, the mechanical crushing action initially disrupts the continuous and dense original oxide film on the powder surface, exposing a fresh metal matrix. This provides more active sites for the subsequent uniform adhesion of stannous chloride and chemical film-breaking reaction, ultimately helping to refine the grains and further enhance the material's strength and toughness through a grain refinement strengthening mechanism.

[0154] This invention overcomes the problem of traditional methods that rely on simple mechanical grinding to destroy the oxide film on the surface of aluminum powder or aluminum alloy powder, which easily leads to the regeneration of a new oxide film and hinders sintering densification. It also breaks through the limitations of mixed salt systems that rely on high-temperature melting to destroy the oxide film. By introducing trace amounts of stannous chloride onto the surface of the aluminum alloy powder, and utilizing its low melting point (247°C), it sequentially exerts liquid-phase wetting and interfacial activation effects during the sintering heating process. This causes the alumina film to undergo a chlorination reaction, generating easily sublimable and removable AlCl3. Simultaneously, Sn containing Sn, Cl, and O is formed on the particle surface. a Cl b O c The interface activation products make it easy to achieve pressureless full densification sintering of particles, simplifying the composition system and process flow, and significantly reducing energy consumption.

[0155] This invention breaks away from the traditional densification technology that relies on pressure-activated sintering. Instead, it employs an activated pressureless sintering process. Through the liquid-phase action of stannous chloride and the activation by chloride ions during sintering, the oxide film is effectively broken down, achieving efficient densification. Simultaneously, the oxide film is transformed from a continuous distribution state into several nanoscale alumina particles, which play a role in dispersion strengthening, further improving the mechanical properties and high-temperature stability of the product, and broadening the application range of aluminum alloy sintered parts.

[0156] The process of this invention is simple and low-cost, making it suitable for industrial application. The 7xxx series powder metallurgy aluminum alloys prepared have higher density and better mechanical properties, meeting the urgent needs of aerospace, artificial intelligence (robotics), low-altitude economy (drones) and other fields for high-strength, high-toughness aluminum alloy materials and lightweight complex parts.

[0157] In summary, compared with existing aluminum alloy powder metallurgy preparation methods, the method of the present invention obtains high-performance powder metallurgy aluminum alloy products through alloy powder pretreatment, preparation of stannous chloride organic solution, preparation of composite powder, pressing and forming, activation pressureless sintering, and solution + aging treatment. Therefore, the method is simple in process, easy to operate, low in cost, and high in efficiency, which is conducive to large-scale industrial production and application.

[0158] It should be understood that the term "and / or" in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. Additionally, the character " / " in this article generally indicates an "or" relationship between the preceding and following related objects, but it can also represent an "and / or" relationship. Please refer to the context for a more accurate understanding.

[0159] In this invention, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of a single item or a plurality of items. For example, at least one of a, b, or c can represent: a, b, c, ab, ac, bc, or abc, where a, b, and c can be a single item or multiple items.

[0160] It should be understood that, in various embodiments of the present invention, the order of the above-mentioned process numbers does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present invention.

[0161] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for chlorination-induced film-breaking activation sintering densification of aluminum alloy powder, characterized in that, The method for chlorination-induced film-breaking activation sintering densification of aluminum alloy powder includes the following steps: S1. Alloy powder pretreatment: The 7xxx aluminum alloy powder is further crushed and deformed to obtain fine-grained 7xxx aluminum alloy powder. S2. Preparation of stannous chloride organic solution: Stannous chloride powder is dissolved in a non-polar, volatile organic solvent to obtain a stannous chloride organic solution; S3. Composite powder preparation: The fine-grained 7xxx aluminum alloy powder of S1 and the stannous chloride organic solution of S2 are simultaneously introduced into a dry mechanical mixing process to coat the aluminum alloy powder, resulting in a composite powder in which stannous chloride is uniformly coated on the surface of the aluminum alloy powder. S4. Pressing: The composite powder of S3 is formed by molding or cold isostatic pressing to obtain a pressed green body. S5. Activated pressureless sintering: The pressed green billet of S4 is activated pressureless sintering to obtain a fully dense aluminum alloy sintered billet. S6, Solution Treatment + Aging Treatment: The S5 fully dense aluminum alloy sintered billet is first subjected to solution water quenching treatment, followed by low-temperature aging treatment, to finally obtain high-performance powder metallurgy aluminum alloy products.

2. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The 7xxx aluminum alloy powder of S1 is one or more of the following: gas atomized powder, air atomized powder, water atomized powder, water-air combined atomized powder, and mechanical alloying powder, with an average particle size of 2-50μm and an oxide film thickness of 3-20nm on the powder surface.

3. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, Further crushing and deformation refinement of S1 involves high-energy ball milling at a speed of 120 r / min for 6-12 h. The average particle size of the fine 7xxx aluminum alloy powder is 1-30 μm, and the oxide film thickness on the powder surface is 2-15 nm.

4. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The average size of the stannous chloride powder in S2 is 30-80 μm. The non-polar volatile organic solvent includes at least one of acetone, anhydrous isopropanol, and cyclohexane. The mass ratio of stannous chloride powder to organic solvent is 1:10-1:

20.

5. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The dry mechanical mixing of S3 is one or more of the following: rolling ball mill, planetary ball mill, stirring ball mill, vibrating ball mill, V-type mixing, and three-dimensional mixing. The mixing time is 2-48 hours, the ball-to-material ratio is 1:1-20:1, and the mixing atmosphere is one or two of the following: high-purity nitrogen and argon.

6. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The S3 mixture also needs to undergo ultrasonic stirring, centrifugation, and drying; the mass percentage of stannous chloride in the composite powder is 0.05-0.3%, and the thickness of stannous chloride uniformly coated on the surface of the aluminum alloy powder is 10-100 nm.

7. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The molding or cold isostatic pressing pressure of S4 is 150-350MPa, the holding time is 10-180s, and the size of the pressed green blank is determined according to the specific size of the mold cavity, which is a columnar or block shape with an outer contour diameter of 10-1000mm and a height of 10-2000mm.

8. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The activated pressureless sintering of S5 is at least one of vacuum sintering and atmosphere-protected sintering, with a sintering temperature of 550-620℃, a holding time of 0.5-5h, and a vacuum degree of 10. -3 -10 -1 Pa, the atmosphere includes vacuum, high-purity argon or high-purity nitrogen.

9. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, In the solution quenching treatment of S6, the heating rate is 5-20℃ / min, the solution temperature is 450-480℃, and the holding time is 0.5-2h; the water temperature for quenching is 20-60℃; in the aging treatment, the heating rate is 2-10℃ / min, the aging temperature is 120-150℃, and the holding time is 6-24h.

10. The method for chlorination-induced film breaking activation sintering densification of aluminum alloy powder according to claim 1, characterized in that, The density of S6 high-performance powder metallurgy aluminum alloy products is 2.80-2.86 g / cm³. 3 It has a density greater than 98%, tensile strength greater than 600 MPa, yield strength greater than 550 MPa, yield strength ratio of 0.85-0.95, elongation of 5.0-15.0%, strength-ductility product of 4.0-10.0 GPa%, and fracture toughness of 15-25 MPa·m. 1 / 2 The impact energy is 2-8J.

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