An aviation aluminum alloy material and a preparation process thereof

Abstract

The application provides an aviation aluminum alloy material, which comprises the following components in percentage by weight: Cu: 3.8-4.6 %, Zn: 6.3-7.2 %, Mg: 1.5-1.9 %, Zr: 0.15-0.22 %, Fe: less than or equal to 0.12 %, Si: less than or equal to 0.10 %, and the balance of Al and non-artificially added impurities. The preparation process comprises the following steps: raw material melting, step-by-step smelting, composite refining, rotary degassing, modification treatment and casting forming. Through the synergistically optimized rotary degassing process, composite refining system, nanoparticle modification treatment and differential pressure casting pressure gradient control, the high-strength and high-toughness aviation aluminum alloy material with small grain size and uniform ZrAl3 phase distribution is obtained while realizing low hydrogen content and low porosity defects, and the technical bottlenecks of low hydrogen removal efficiency, excessive slag and coexistence of micro shrinkage in the traditional process are systematically solved.

Description

Technical Field

[0001] This invention belongs to the field of metal material processing technology, specifically relating to an aerospace aluminum alloy material and its preparation process. Background Technology

[0002] Aerospace aluminum alloys are lightweight structural materials made with aluminum as the matrix and reinforced by the addition of elements such as copper, zinc, and magnesium. In both military and civilian aviation, these materials are primarily used to manufacture components that withstand complex alternating loads, such as wing spars, hydraulic valve bodies, and turbine casings. These components must simultaneously meet three core performance indicators: a tensile strength of not less than 450 MPa to withstand aerodynamic loads, a hydrogen content of less than 0.15 ml / 100 g Al to prevent hydrogen embrittlement during service, and an X-ray flaw detection porosity level not exceeding level 3 to ensure structural integrity.

[0003] However, current aerospace aluminum alloy castings face three major technical bottlenecks in practical applications: First, hydrogen contamination control during the smelting process fails. Liquid aluminum absorbs hydrogen atoms from water vapor decomposition at temperatures above 720°C. The traditional solution is to introduce argon gas into the bottom of the smelting furnace for bubbling. However, due to the increased viscosity of high-zinc content alloy melts, the bubble rising speed decreases by more than 40%, leading to a sharp drop in hydrogen removal efficiency. Some manufacturers have attempted vacuum smelting, but the equipment investment cost is more than five times that of conventional smelting lines.

[0004] Secondly, micro-shrinkage porosity is unavoidable. Taking Al-Zn-Mg-Cu alloys as an example, their solidification temperature range is 160-180℃, causing the feeding channels to close prematurely during gravity casting. Current solutions involve increasing the riser size to 30% of the casting volume, but this results in a metal utilization rate of less than 50%. Although differential pressure casting can increase the feeding pressure to 80 kPa, isolated shrinkage cavities with diameters of 50-200 μm will still appear in the center of thick sections.

[0005] Third, excessive oxide inclusions. Statistics show that 60% of fatigue cracks on the casting surface originate from Al2O3 inclusions introduced during smelting. Current mainstream technology uses ceramic foam filters, but when the melt flows through the filter, the newly formed oxide film ruptures, forming micron-sized debris. This resulted in a less than 70% installation pass rate for the transmission housing of a certain helicopter model.

[0006] To address the aforementioned issues, several improved technologies have emerged in recent years: some patents propose adding rare earth cerium to improve melt fluidity, but adding more than 0.3% can cause grain boundary embrittlement; another solution uses electromagnetic centrifugal slag removal, but it is only suitable for tubular castings and consumes as much as 120 kWh / ton. None of these technologies have been able to overcome the key bottleneck of synergistic optimization of hydrogen removal, feeding, and slag removal.

[0007] Therefore, it is necessary to design an aerospace aluminum alloy material and its preparation process. Summary of the Invention

[0008] To overcome the shortcomings of existing technologies, an aerospace aluminum alloy material and its preparation process are provided.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] An aerospace aluminum alloy material, the chemical composition of which, by weight percentage, comprises: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities.

[0011] The microstructure of this aerospace aluminum alloy material contains the ZrAl3 phase, which is distributed in a blocky manner with an average size of 0.8-1.2 μm; the average grain size is 60-70 μm, the tensile strength is greater than 495 MPa, and there are no continuous network compounds at the grain boundaries.

[0012] A process for preparing an aerospace aluminum alloy material, the process comprising the following steps:

[0013] Raw material melting and mixing: Electrolytic aluminum ingots, Al-50Cu master alloy blocks, Al-10Zr master alloy ingots, metallic magnesium ingots, and metallic zinc ingots are loaded into a graphite crucible, with the total loading amount controlled to be 75-85% of the crucible volume;

[0014] Stepped melting: The first stage is melting at 680-695℃ for 60-75 minutes until complete liquefaction, and the second stage is heating to 720-740℃ and holding for 50-70 minutes to alloy.

[0015] Compound refining: Add compound solvent A at a rate of 0.4-0.65% of the total mass of the refined melt, and mechanically stir at 400-500 rpm for 15-20 minutes at 715-725℃.

[0016] Rotary degassing: The refined melt is transferred into a closed degassing chamber, and a mixture of Ar and Cl2 gas is introduced, with Cl2 accounting for 4%-7% of the total gas volume. The gas introduction rate is 1.5-2.0 L / min·kg, the rotor speed is 550-600 rpm, the processing time is 14-16 minutes, and the gas pressure in the closed degassing chamber is maintained at 0.28-0.35 MPa.

[0017] Modification treatment: Add composite modifier B to the degassed melt at a rate of 0.18-0.32% of the mass of the degassed melt, and keep it at 745-755℃ for 25-35 minutes; then immediately apply a pulsed magnetic field: magnetic field strength 1.0-1.3T, pulse frequency 15-25Hz, and application time 8-12 minutes.

[0018] Casting: Differential pressure casting process is adopted. The lower mold is preheated to 280-320℃. The filling pressure gradient increases: 18kPa within 0-5 seconds, 28kPa within 5-10 seconds, and the pressure is maintained at 45-55kPa during the holding stage until solidification is completed. After cooling, the finished aerospace aluminum alloy material is obtained.

[0019] In the raw material melting and mixing, the weight percentage of each raw material component according to the final melt chemical composition is as follows: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities.

[0020] In compound refining, the compound solvent A, by mass, is composed of the following raw materials:

[0021] 18-23 parts of basic magnesium carbonate powder;

[0022] 25-32 parts of modified cryolite powder were obtained by calcining cryolite powder at 550-570℃ for 1.5 hours.

[0023] 15-18 parts of anhydrous borax;

[0024] 8-11 parts of magnesium fluoride powder;

[0025] Add sodium chloride to bring the total to 100 parts.

[0026] The particle size ratio of the basic magnesium carbonate powder to anhydrous borax is between 2 and 3:1, with average particle sizes of 45-65 μm and 20-35 μm, respectively.

[0027] In the deterioration treatment, the preparation process of the composite deteriorator B includes the following steps:

[0028] 1. Place the Al-5Ti-1B alloy ingot in a vacuum induction furnace, evacuate to 10-2 Pa, then fill with argon gas to 0.5 MPa, and control the melting temperature to 1150-1200℃;

[0029] 2. Add nano-silicon carbide particles to the molten alloy obtained in the previous step, with an addition amount of 1.0-1.3% of the alloy mass. The nano-silicon carbide particles are pretreated, specifically by having a median particle size of 80 nm and a specific surface area of ​​18-22 m². 2 / g of nano-silicon carbide particles were soaked in 18% nitric acid solution and treated at 70°C for 1 hour, then washed with water and dried.

[0030] 3. Apply an ultrasonic oscillation field with a frequency of 28kHz, a power density of 1.8kW / kg, and an action time of 25-40 minutes;

[0031] IV. Spherical pre-alloyed powder is obtained by nitrogen atomization, and the particle size is 45-75μm after sieving. This is the composite modifier B.

[0032] Nano-tin oxide powder is added simultaneously with composite modifier B, with the amount of nano-tin oxide powder added being 0.8-1.2g per kilogram of melt.

[0033] The nano-tin oxide powder is prepared by the following process: tin tetrachloride is dissolved in ethanol to form a 0.6 mol / L solution; 12% by volume of polyvinylpyrrolidone dispersant is added, and the mixture is stirred at 55°C until completely dissolved; concentrated ammonia is added dropwise to adjust the pH to 9.5, and a colloidal stannic acid precipitate is formed; after centrifugation, the mixture is treated in a vacuum drying oven at 120°C for 2.5 hours to obtain nano-tin oxide powder.

[0034] During compound refining, an isolation layer is applied to the surface of the melt. The isolation layer is made by mixing boron nitride powder and expanded graphite in a mass ratio of 1:0.3-0.7, and the thickness of the isolation layer is 20-25 mm.

[0035] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows:

[0036] 1. This innovative rotary degassing process treats the melt in a pressurized environment using a specific ratio of argon-chlorine mixed gas. The trace amounts of chlorine effectively break down the oxide film on the melt surface, while the pressurized environment significantly enhances the diffusion and penetration of the gas within the melt, promoting the migration of hydrogen atoms into the bubbles and thus avoiding hydrogen embrittlement during subsequent solidification. This design is specifically tailored to the high viscosity of high-zinc alloy melts, overcoming the shortcomings of traditional methods that result in slow bubble rise.

[0037] 2. To address the problem of oxide inclusions, this invention develops a composite refining agent system. In this system, basic magnesium carbonate decomposes at the smelting temperature, releasing carbon dioxide to form a microbubble network. This network, combined with modified cryolite, efficiently captures tiny alumina fragments. More importantly, the insulating layer covering the melt surface employs a composite structure of boron nitride and expanded graphite, which both isolates it from atmospheric oxidation and adsorbs floating slag through capillary action, reducing inclusion formation at its source.

[0038] 3. The modification process of this application creatively encapsulates nano-silicon carbide particles in an aluminum-titanium-boron carrier, achieving uniform distribution of these particles within the aluminum matrix through ultrasonic dispersion during preheating of the melt. Subsequent application of a pulsed magnetic field generates periodic Lorentz force impacts, which not only break up primary dendrites but also prevent secondary agglomeration of the nanoparticles. This dual effect significantly improves both the dispersion density and uniformity of the reinforcing phase within the matrix.

[0039] 4. To solve the problem of insufficient feeding, the specially designed pressure gradient control in differential pressure casting achieves precise feeding: the lower pressure in the early stage ensures that the melt fills the mold smoothly and reduces eddy air entrapment; the step-by-step pressure increase in the middle stage pushes the melt to penetrate into the dendrite gaps; and finally, the high pressure is maintained until complete solidification. This strategy effectively inhibits the formation of shrinkage porosity and significantly reduces the volume of process risers.

[0040] 5. The added nano-tin oxide undergoes a selective reduction reaction in the high-temperature melt, and the generated active tin atoms preferentially occupy grain boundary sites, preventing the continuous precipitation of magnesium-zinc compounds along the grain boundaries. This is particularly important for improving the material's ductility. Simultaneously, the residual tin oxide particles act as heterogeneous nucleation cores, complementing the zirconium-aluminum intermetallic compounds. Regarding the control of intermetallic compounds, strict control of the stepped melting parameters ensures the full dissolution of zirconium, resulting in the formation of uniformly sized, fine, and independently distributed blocky ZrAl3 phases during subsequent solidification. The rational distribution of these intermetallic compounds contributes to precipitation strengthening without disrupting the matrix, becoming a crucial support for the material's high strength and toughness.

[0041] 6. Vacuum argon protection during the preparation of the composite modifier prevents the oxidation and sintering of nanoparticles. The spherical powder obtained by nitrogen atomization exhibits good flowability and wettability. When added to the melt, it can be rapidly and uniformly dispersed, avoiding localized enrichment areas that could affect the uniformity of material properties. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] The sources of various raw materials in this application are briefly described as follows:

[0044] Electrolytic aluminum ingots: No. 1 electrolytic aluminum ingots produced by China Aluminum Corporation, grade Al99.7, with an aluminum content of not less than 99.70%, conforming to the national standard GB / T 1196-2020.

[0045] Al-50Cu master alloy block: The master alloy is provided by Liaoning Zhongwang Group, grade ALCu50, with copper content controlled at 50±0.5% and the balance being aluminum.

[0046] Al-10Zr master alloy ingot: purchased from Hunan Jintian Titanium Industry Technology Co., Ltd., grade AlZr10, zirconium content 10.0±0.3%, aluminum base metal purity 99.5%.

[0047] Magnesium ingots: Grade 1 magnesium ingots produced by Ningxia Shengyan Industrial Group, grade Mg9995, with a magnesium content ≥99.95%, conforming to national standard GB / T 3499-2011.

[0048] Zinc ingots: Selected from No. 0 zinc ingots of Zhuzhou Smelting Group Co., Ltd., grade Zn99.995, zinc purity ≥99.995%, conforming to national standard GB / T 470-2008.

[0049] Basic magnesium carbonate powder: purchased from Shandong Haihua Group, industrial grade, 99% purity, CAS No. 39409-82-0, average particle size range 45-65μm.

[0050] Cryolite powder: purchased from Duofuduo New Materials Co., Ltd., grade high molecular weight cryolite, used after calcination modification at 550-570℃.

[0051] Anhydrous borax: Made from Liaoning Shougang Boron Iron Chemical Products, chemically pure, CAS No. 1330-43-4, fineness meets the requirement of 20-35μm.

[0052] Magnesium fluoride powder: Selected from Charles River Company products, analytical grade, CAS No. 7783-40-6, particle size controlled above 400 mesh.

[0053] Sodium chloride: Refined industrial salt from China National Salt Industry Corporation, CAS No. 7647-14-5, passed through a 40-mesh sieve to meet the requirements for compounding.

[0054] Nano-silicon carbide particles: Purchased from Suzhou Youzirconium Nanomaterials Co., Ltd., model UG-SI50C, median particle size 80nm, specific surface area 20±1m². 2 / g.

[0055] Al-5Ti-1B alloy ingot: using grain refiner from Hunan Jinrui New Material Technology Co., Ltd., grade AlTi5B1, with titanium content of 5.0±0.2% and boron content of 1.0±0.1%.

[0056] Tin tetrachloride: Selected from Shanghai Aladdin Biochemical Technology Co., Ltd., analytical grade reagent, CAS No. 7646-78-8, tin content ≥46.5%.

[0057] Polyvinylpyrrolidone: Purchased from Sinopharm Chemical Reagents, model PVP-K30, CAS number 9003-39-8.

[0058] Boron nitride powder: The product used is from Saint-Gobain Ceramic Materials, model HCPF, hexagonal crystal form, 99% purity, and average particle size of 8μm.

[0059] Expanded graphite: Selected from Qingdao Heilong Graphite Co., Ltd., grade ED-300, expansion ratio ≥300mL / g, CAS number 7782-42-5.

[0060] An aerospace aluminum alloy material, the chemical composition of which, by weight percentage, comprises: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities.

[0061] The microstructure of this aerospace aluminum alloy material contains the ZrAl3 phase, which is distributed in a blocky manner with an average size of 0.8-1.2 μm; the average grain size is 60-70 μm, the tensile strength is greater than 495 MPa, and there are no continuous network compounds at the grain boundaries.

[0062] A process for preparing an aerospace aluminum alloy material, the process comprising the following steps:

[0063] Raw material melting and mixing: Electrolytic aluminum ingots, Al-50Cu master alloy blocks, Al-10Zr master alloy ingots, metallic magnesium ingots, and metallic zinc ingots are loaded into a graphite crucible, with the total loading amount controlled to be 75-85% of the crucible volume;

[0064] Stepped melting: The first stage is melting at 680-695℃ for 60-75 minutes until complete liquefaction, and the second stage is heating to 720-740℃ and holding for 50-70 minutes to alloy.

[0065] Compound refining: Add compound solvent A at a rate of 0.4-0.65% of the total mass of the refined melt, and mechanically stir at 400-500 rpm for 15-20 minutes at 715-725℃.

[0066] Rotary degassing: The refined melt is transferred into a closed degassing chamber, and a mixture of Ar and Cl2 gas is introduced, with Cl2 accounting for 4%-7% of the total gas volume. The gas introduction rate is 1.5-2.0 L / min·kg, the rotor speed is 550-600 rpm, the processing time is 14-16 minutes, and the gas pressure in the closed degassing chamber is maintained at 0.28-0.35 MPa.

[0067] Modification treatment: Add composite modifier B to the degassed melt at a rate of 0.18-0.32% of the mass of the degassed melt, and keep it at 745-755℃ for 25-35 minutes; then immediately apply a pulsed magnetic field: magnetic field strength 1.0-1.3T, pulse frequency 15-25Hz, and application time 8-12 minutes.

[0068] Casting: Differential pressure casting process is adopted. The lower mold is preheated to 280-320℃. The filling pressure gradient increases: 18kPa within 0-5 seconds, 28kPa within 5-10 seconds, and the pressure is maintained at 45-55kPa during the holding stage until solidification is completed. After cooling, the finished aerospace aluminum alloy material is obtained.

[0069] In the raw material melting and mixing, the weight percentage of each raw material component according to the final melt chemical composition is as follows: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities.

[0070] In compound refining, the compound solvent A, by mass, is composed of the following raw materials:

[0071] 18-23 parts of basic magnesium carbonate powder;

[0072] 25-32 parts of modified cryolite powder were obtained by calcining cryolite powder at 550-570℃ for 1.5 hours.

[0073] 15-18 parts of anhydrous borax;

[0074] 8-11 parts of magnesium fluoride powder;

[0075] Add sodium chloride to bring the total to 100 parts.

[0076] The particle size ratio of the basic magnesium carbonate powder to anhydrous borax is between 2 and 3:1, with average particle sizes of 45-65 μm and 20-35 μm, respectively.

[0077] In the deterioration treatment, the preparation process of the composite deteriorator B includes the following steps:

[0078] 1. Place the Al-5Ti-1B alloy ingot in a vacuum induction furnace, evacuate to 10-2 Pa, then fill with argon gas to 0.5 MPa, and control the melting temperature to 1150-1200℃;

[0079] 2. Add nano-silicon carbide particles to the molten alloy obtained in the previous step, with an addition amount of 1.0-1.3% of the alloy mass. The nano-silicon carbide particles are pretreated, specifically by having a median particle size of 80 nm and a specific surface area of ​​18-22 m². 2 / g of nano-silicon carbide particles were soaked in 18% nitric acid solution and treated at 70°C for 1 hour, then washed with water and dried.

[0080] 3. Apply an ultrasonic oscillation field with a frequency of 28kHz, a power density of 1.8kW / kg, and an action time of 25-40 minutes;

[0081] IV. Spherical pre-alloyed powder is obtained by nitrogen atomization, and the particle size is 45-75μm after sieving. This is the composite modifier B.

[0082] Nano-tin oxide powder is added simultaneously with composite modifier B, with the amount of nano-tin oxide powder added being 0.8-1.2g per kilogram of melt.

[0083] The nano-tin oxide powder is prepared by the following process: tin tetrachloride is dissolved in ethanol to form a 0.6 mol / L solution; 12% by volume of polyvinylpyrrolidone dispersant is added, and the mixture is stirred at 55°C until completely dissolved; concentrated ammonia is added dropwise to adjust the pH to 9.5, and a colloidal stannic acid precipitate is formed; after centrifugation, the mixture is treated in a vacuum drying oven at 120°C for 2.5 hours to obtain nano-tin oxide powder.

[0084] During compound refining, an isolation layer is applied to the surface of the melt. The isolation layer is made by mixing boron nitride powder and expanded graphite in a mass ratio of 1:0.3-0.7, and the thickness of the isolation layer is 20-25 mm.

[0085] The technical solutions of the present invention are further illustrated below through examples and comparative examples, but the scope of protection of the present invention is not limited thereto.

[0086] Example 1

[0087] The raw material melting and mixing process is carried out in a graphite crucible, which is loaded with electrolytic aluminum ingots, Al-50Cu master alloy blocks, Al-10Zr master alloy ingots, magnesium ingots, and zinc ingots, with the total load controlled to 85% of the crucible volume. During the raw material melting and mixing, the weight percentages of each raw material component according to the final melt chemical composition are: Cu: 4%, Zn: 0.2%, Mg: 1.9%, Zr: 0.22%, Fe≤0.12%, Si≤0.10%.

[0088] The stepped melting process is carried out in two stages: in the first stage, the temperature is controlled at 695℃ and the melting continues for 75 minutes until complete liquefaction is achieved; in the second stage, the temperature is raised to 740℃ and held for 70 minutes to complete alloying.

[0089] Next, composite refining was performed, with composite solvent A added at a rate of 0.4% of the total mass of the refined melt. The temperature was maintained at 715℃, and the mixture was mechanically stirred at 500 rpm for 20 minutes. Composite solvent A was composed of 23 parts of basic magnesium carbonate powder, 32 parts of modified cryolite powder (calcination process as in the original scheme), 18 parts of anhydrous borax, 11 parts of magnesium fluoride powder, and sodium chloride to make up to 100 parts. The particle size ratio of basic magnesium carbonate to anhydrous borax was 3:1, with average particle sizes of 65 μm and 35 μm, respectively. During refining, an isolation layer was placed on the surface of the melt. This isolation layer was made by mixing boron nitride powder and expanded graphite at a mass ratio of 1:0.3, with a thickness of 25 mm.

[0090] After refining, the melt is transferred to the rotary degassing process, where a mixture of Ar and Cl2 gas is introduced, with Cl2 accounting for 4%, the gas introduction rate is 2.0 L / min·kg, the rotor speed is 600 rpm, the processing time is 16 minutes, and the gas pressure in the degassing chamber is stabilized at 0.35 MPa.

[0091] During the modification treatment stage, composite modifier B was added at a rate of 0.25% of the melt mass, and the mixture was held at 755℃ for 35 minutes. The preparation of composite modifier B included: melting Al-5Ti-1B alloy ingots at 1150℃ (vacuum induction furnace treatment); adding nano-silicon carbide particles pretreated with nitric acid (addition amount 1.3%); applying an ultrasonic oscillation field at 28kHz for 40 minutes; nitrogen atomization to sieve to a particle size of 75μm; immediately after the modifier was added, applying a pulsed magnetic field with a magnetic field strength of 1.3T and a frequency of 25Hz for 12 minutes; and simultaneously adding nano-tin oxide powder (1.0g per kilogram of melt).

[0092] Finally, differential pressure casting is used for casting. The lower mold is preheated to 300℃, and the filling pressure gradient is as follows: 18kPa is reached in 0-5 seconds, 28kPa is raised in 5-10 seconds, and the pressure is maintained at 50kPa until solidification is completed.

[0093] Example 2

[0094] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0095] The total charge volume in the raw material mixing process is set at 75% of the crucible volume. In the raw material mixing process, the weight percentages of each raw material component according to the final melt chemical composition are as follows: Cu: 4.6%, Zn: 7%, Mg: 1.7%, Zr: 0.15%, Fe≤0.12%, Si≤0.10%.

[0096] The first stage of the stepped melting process involves operating at 680℃ for 60 minutes to liquefy the material, and the second stage involves holding at 720℃ for 50 minutes.

[0097] In the composite refining step, the amount of composite solvent A added is 0.65%, the temperature is set at 725℃, and the stirring speed is 400 rpm for 15 minutes. The composition of composite solvent A is 18 parts of basic magnesium carbonate powder, 25 parts of modified cryolite powder, 15 parts of anhydrous borax, 8 parts of magnesium fluoride powder, and sodium chloride to make up the difference. The particle size ratio is controlled at 2:1, the average particle size of basic magnesium carbonate is 45 μm, and the anhydrous borax is 20 μm. The isolation layer has a coverage thickness of 25 mm, and the mixing ratio is 1:0.7 of boron nitride powder and expanded graphite.

[0098] The rotary degassing system uses 7% Cl2, with a gas flow rate of 1.5 L / min·kg, a rotor speed of 550 rpm, a processing time of 14 minutes, and a gas pressure of 0.28 MPa.

[0099] The modification treatment involved adding 0.18% of composite modifier B and holding at 745℃ for 25 minutes. The melting temperature of modifier B was 1200℃, 1.0% of nano-silicon carbide was added, the ultrasonic treatment lasted for 25 minutes, and the particle size was sieved to 45μm. Subsequently, a pulsed magnetic field was applied with the following parameters: intensity 1.0T, frequency 15Hz, and time 8 minutes. At the same time, 0.8g of nano-tin oxide powder was added per kilogram of melt.

[0100] During the casting stage, the mold preheating temperature is 280℃ and the holding pressure is 45kPa.

[0101] Example 3

[0102] In this embodiment, the similarities to those in Embodiment 1 will not be repeated, and the differences are as follows:

[0103] The raw material loading volume is controlled to 80% of the crucible volume. During raw material mixing, the weight percentages of each raw material component according to the final melt chemical composition are as follows: Cu: 3.8%, Zn: 6.3%, Mg: 1.5%, Zr: 0.19%, Fe≤0.12%, Si≤0.10%.

[0104] The first stage of the stepped melting process is carried out at 687.5℃ for 67.5 minutes, and the second stage is held at 730℃ for 60 minutes.

[0105] The compound refining process involved adding 0.525% of compound solvent A at a temperature of 720℃ and a stirring speed of 450 rpm for 17.5 minutes. Compound solvent A consisted of 20.5 parts of basic magnesium carbonate, 28.5 parts of modified cryolite, 16.5 parts of anhydrous borax, 9.5 parts of magnesium fluoride, and sodium chloride. The particle size ratio was 2.5:1, with an average particle size of 55 μm for basic magnesium carbonate and 27.5 μm for anhydrous borax. The isolation layer thickness was 22.5 mm, and the mass ratio of boron nitride powder to expanded graphite was 1:0.5.

[0106] The rotary degassing process used a Cl2 content of 5.5%, a gas velocity of 1.75 L / min·kg, a rotor speed of 575 rpm, a processing time of 15 minutes, and a gas pressure of 0.315 MPa.

[0107] The modified treatment was carried out with 0.32% composite modifier B added and held at 750℃ for 30 minutes; the melting temperature of modifier B was 1175℃, 1.15% nano-silicon carbide was added, the ultrasonic treatment time was 32.5 minutes, and the particle size was 60μm; the pulse magnetic field parameters were set with an intensity of 1.15T, a frequency of 20Hz, and a time of 10 minutes; and 1.2g of nano-tin oxide powder was added per kilogram of melt.

[0108] The preheating temperature of the casting mold is 320℃, and the holding pressure is 55kPa.

[0109] Comparative Example 1

[0110] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0111] The rotary degassing process was replaced by the traditional argon bubbling method, which does not control the gas pressure and chlorine ratio, and the gas rate is only 0.8 L / min·kg.

[0112] Comparative Example 2

[0113] In this comparative example, the similarities with Example 2 will not be repeated, and the differences are as follows:

[0114] The composite solvent A is not added during the composite refining process, and the isolation layer covering step is also omitted.

[0115] Comparative Example 3

[0116] In this comparative example, the similarities with Example 3 will not be repeated, and the differences are as follows:

[0117] No composite modifier B was added during the modification treatment stage, and the application of pulsed magnetic field was also cancelled, retaining only the basic alloying elements.

[0118] Comparative Example 4

[0119] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0120] The casting process was changed to gravity casting, with no pressure gradient control, and the holding pressure remained constant at 20 kPa.

[0121] Comparative Example 5

[0122] In this comparative example, the similarities with Example 1 will not be repeated, and the differences are as follows:

[0123] The addition of nano-tin oxide powder was omitted to ensure that other conditions were consistent in order to observe the effect of grain boundaries.

[0124] Performance Test Results and Analysis

[0125] Materials were prepared according to the parameters of the examples and comparative examples, and their performance was tested. The test results are shown in Table 1. Tensile strength was tested according to ASTM E8; hydrogen content was determined by vacuum thermal extraction (unit: ml / 100gAl); X-ray flaw detection porosity was rated according to ASTM E505 (lower rating is better); and average grain size was calculated using metallographic microscopy.

[0126] Table 1 Analysis of Test Results

[0127]

[0128]

[0129] As can be seen from Table 1, the advantages of the rotary degassing process of this application are significantly reflected in the results of the examples: the pressurized environment combined with chlorine components effectively breaks down the oxide film in the melt, enhancing hydrogen diffusion efficiency and maintaining the hydrogen content in all examples at 0.09-0.10 ml / 100gAl, far below the safety threshold of 0.15 ml / 100gAl mentioned in the background art. Comparative Example 1 did not use this process, and the hydrogen content rose to 0.22 ml / 100gAl, proving that traditional degassing methods have low hydrogen removal efficiency in high-zinc melts; consistent with the description of beneficial effects, the specific ratio of argon-chlorine mixed gas solves the problem of hydrogen residue caused by slow bubble rise.

[0130] The porosity level of Examples 1-3 is all grade 1, indicating that the microbubble network derived from the decomposition of basic magnesium carbonate and the capillary action of the isolation layer jointly reduce alumina inclusions; Comparative Example 2 omits these measures, and the porosity level deteriorates to grade 5, which is consistent with the risk of fatigue cracking; this result directly reflects the beneficial effect, indicating that the boron nitride expanded graphite composite structure not only isolates oxidation but also adsorbs slag, synergistically optimizing melt purity, and verifying the effectiveness of the composite refining agent and isolation layer design in this application.

[0131] In the microstructure optimization section, the synergistic effect of the modification treatment and the pulsed magnetic field is significant: the average grain size of the examples is controlled at 60-70 μm, with no continuous network compounds, and the tensile strength exceeds 510 MPa; in contrast, the strength of the comparative example 3 drops to 435 MPa, and the grain size reaches 88 μm, showing that the primary dendrites did not break when the composite modifier B and the magnetic field were missing; the uniform distribution of nano-silicon carbide particles was confirmed by testing, and the pulsed magnetic field prevents secondary agglomeration. This, combined with the size control of the ZrAl3 phase, supports the high strength and high toughness of the material, and there are no brittle phase fracture points at the grain boundaries.

[0132] In the three embodiments, the pressure gradient design during the holding stage achieved precise feeding, and the porosity level was 1 in all three embodiments. However, in Comparative Example 4, which used gravity casting, the porosity level increased to 6. This shows that the pressure strategy of low pressure at the beginning and high pressure at the end of differential pressure casting can penetrate the dendrite gaps and suppress shrinkage cavities. This also shows that the strategy of stable filling and high pressure maintenance in the early stage avoids the shrinkage porosity problem of thick cross sections. The improved feeding performance is reflected in the porosity level and strength.

[0133] The comparison of the three examples and Comparative Example 5 shows that it contributes to ductility, but the difference in strength is not significant; this may be because tin atoms occupy the grain boundaries and hinder the precipitation of brittle phases; the vacuum protection measures prepared by the composite modifier B enhance the uniformity of particle dispersion, and all examples show excellent wetting and avoidance of local enrichment.

[0134] The combination of parameters in the example achieves a strength of over 510 MPa, a hydrogen content of less than 0.10 ml / 100 g Al, and a porosity grade of 1, demonstrating that the optimization of each step from degassing to casting enhances each other; while the absence of any one step, as in the comparative example, leads to a sharp drop in performance.

[0135] Test results show that the process of this application uses rotary degassing to enhance hydrogen diffusion, composite refining agent to capture inclusions, modification treatment and pulsed magnetic field to optimize grain structure, and differential pressure casting pressure gradient to suppress shrinkage porosity, synergistically achieving high comprehensive performance of aerospace aluminum alloys.

[0136] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A preparation process for an aerospace aluminum alloy material, characterized in that, The chemical composition of the aerospace aluminum alloy material, by weight percentage, includes: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities; The microstructure of the aerospace aluminum alloy material contains ZrAl3 phase, which is distributed in a blocky manner with an average size of 0.8-1.2 μm; the average grain size is 60-70 μm, the tensile strength is greater than 495 MPa, and there are no continuous network compounds at the grain boundaries. The preparation process of the aerospace aluminum alloy material includes the following steps: Raw material melting and mixing: Electrolytic aluminum ingots, Al-50Cu master alloy blocks, Al-10Zr master alloy ingots, metallic magnesium ingots, and metallic zinc ingots are loaded into a graphite crucible, with the total loading volume controlled to be 75-85% of the crucible volume; Step-by-step melting: The first stage is melting at 680-695 ℃ for 60-75 minutes until complete liquefaction, and the second stage is heating to 720-740 ℃ and holding for 50-70 minutes for alloying; Compound refining: Add compound solvent A at a rate of 0.4-0.65% of the total mass of the refined melt, and mechanically stir at 400-500 rpm for 15-20 minutes at 715-725 ℃; Rotary degassing: The refined melt is transferred into a closed degassing chamber, and a mixture of Ar and Cl2 gas is introduced, in which the volume percentage of Cl2 is 4%-7%, the gas introduction rate is 1.5-2.0 L / min·kg, the rotor speed is 550-600 rpm, the processing time is 14-16 minutes, and the gas pressure in the closed degassing chamber is maintained at 0.28-0.35 MPa; Modification treatment: Add composite modifier B to the degassed melt at a rate of 0.18-0.32% of the mass of the degassed melt, and keep it at 745-755 ℃ for 25-35 minutes; then immediately apply a pulsed magnetic field: magnetic field strength 1.0-1.3 T, pulse frequency 15-25 Hz, and application time 8-12 minutes; Casting: Differential pressure casting process is adopted. The lower mold is preheated to 280-320 ℃. The filling pressure gradient increases: 18 kPa within 0-5 seconds, 28 kPa within 5-10 seconds, and the pressure is maintained at 45-55 kPa during the holding stage until solidification is completed. After cooling, the finished aerospace aluminum alloy material is obtained. In compound refining, the compound solvent A, by mass, is composed of the following raw materials: 18-23 parts of basic magnesium carbonate powder; 25-32 parts of modified cryolite powder were obtained by calcining cryolite powder at 550-570 ℃ for 1.5 hours; 15-18 parts of anhydrous borax; 8-11 parts of magnesium fluoride powder; Add sodium chloride to bring the total to 100 parts; In the deterioration treatment, the preparation process of the composite deteriorator B includes the following steps:

1. Place the Al-5Ti-1B alloy ingot in a vacuum induction furnace and evacuate it to 10°C. - After 2 Pa, argon gas is introduced to 0.5 MPa, and the melting temperature is controlled at 1150-1200 ℃; 2. Add nano-silicon carbide particles to the molten alloy obtained in the previous step. The amount added is 1.0-1.3% of the alloy mass. The nano-silicon carbide particles are pretreated, specifically: nano-silicon carbide particles with a median particle size of 80nm and a specific surface area of ​​18-22m² / g are soaked in 18% nitric acid solution at 70℃ for 1 hour, then washed and dried.

3. Apply an ultrasonic oscillation field with a frequency of 28 kHz, a power density of 1.8 kW / kg, and an action time of 25-40 minutes; IV. Spherical pre-alloyed powder is obtained by nitrogen atomization, and the particle size is 45-75 μm after sieving. This is the composite modifier B.

2. The preparation process of an aerospace aluminum alloy material according to claim 1, characterized in that, In the raw material melting and mixing, the weight percentage of each raw material component according to the final melt chemical composition is as follows: Cu: 3.8-4.6%, Zn: 6.3-7.2%, Mg: 1.5-1.9%, Zr: 0.15-0.22%, Fe≤0.12%, Si≤0.10%, with the balance being Al and non-artificially added impurities.

3. The preparation process of an aerospace aluminum alloy material according to claim 1, characterized in that, The particle size ratio of the basic magnesium carbonate powder to anhydrous borax is between 2 and 3:1, with average particle sizes of 45-65 μm and 20-35 μm, respectively.

4. The preparation process of an aerospace aluminum alloy material according to claim 1, characterized in that, Nano-tin oxide powder is added simultaneously with composite modifier B, with the amount of nano-tin oxide powder added being 0.8-1.2 g per kilogram of melt.

5. The preparation process of an aerospace aluminum alloy material according to claim 4, characterized in that, The nano-tin oxide powder is prepared by the following process: tin tetrachloride is dissolved in ethanol to form a 0.6 mol / L solution; 12% of the solution volume of polyvinylpyrrolidone dispersant is added and stirred at 55°C until completely dissolved; concentrated ammonia is added dropwise to adjust the pH value to 9.5, and a colloidal stannic acid precipitate is formed; after centrifugation, it is treated in a vacuum drying oven at 120°C for 2.5 hours to obtain nano-tin oxide powder.

6. The preparation process of an aerospace aluminum alloy material according to claim 1, characterized in that, During compound refining, an isolation layer is applied to the surface of the melt. The isolation layer is composed of boron nitride powder and expanded graphite mixed at a mass ratio of 1:0.3-0.7, and the thickness of the isolation layer is 20-25 mm.

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