Aluminum-lithium alloy powder preparation device and preparation process

Abstract

This invention relates to the field of high-activity metal powder technology, specifically to an aluminum-lithium alloy powder preparation apparatus and process, comprising a melting chamber, a melting crucible and an intermediate ladle disposed within the melting chamber, and a vacuum pump disposed on the left side of the melting chamber; the inner wall of the melting crucible is coated with a boron nitride coating, and the melting crucible is disposed on a tiltable movable support; a guide nozzle extending to an atomization chamber is connected to the bottom of the intermediate ladle; an atomization chamber is disposed below the melting chamber and communicates with the melting chamber; an atomization nozzle is disposed at the upper end of the atomization chamber, corresponding to the guide nozzle, and an atomization spray plate is connected to a high-pressure atomizing gas pipeline; a dual-flow atomization mechanism is disposed within the atomization chamber, the gas induced shell comprising an outer cover and an air curtain shell, forming a compressed air chamber between the two, and an elongated air curtain opening is provided on the air curtain shell; a gas recovery device is connected to the atomization chamber via a pipeline, the atomized gas is collected by an induced draft fan, introduced into the high-pressure gas pipe above by a gas booster pump, and further transported to the atomization spray plate through the high-pressure atomizing gas pipeline.

Description

Technical Field

[0001] This invention relates to the field of highly active metal powder technology, specifically to an aluminum-lithium alloy powder preparation apparatus and preparation process. Background Technology

[0002] Adding highly reactive metal powders to propellants not only releases a large amount of heat through combustion reactions with oxidizers, increasing the energy of solid propellants, but also effectively suppresses unstable combustion in engines, improving engine stability and safety. Among these, Al powder, due to its high calorific value, large storage capacity, and low cost, is currently the most widely used metallic fuel. However, Al powder particles suffer from problems during combustion, such as high ignition delay, severe particle agglomeration in the propellant combustion zone, incomplete combustion, and significant two-phase flow losses, affecting the specific impulse and overall energy release of the propellant. Research shows that adding aluminum-lithium alloy powder materials to solid propellants can significantly solve these problems. The significant boiling point difference between metallic Al and metallic Li (2470℃ and 1330℃ respectively) allows the lower-boiling-point Li to boil and atomize within the aluminum-lithium alloy droplets during combustion, effectively breaking up and atomizing the droplets, thus generating micro-explosions during combustion, improving the combustion efficiency of the metallic fuel and reducing two-phase flow losses. Studies have shown that HTPB propellants containing Al-Li alloys (Li content of approximately 20%) can increase the theoretical specific impulse by more than 7 seconds, thereby improving the specific impulse of the propellant, enhancing the rocket's survivability, reducing environmental pollution, and reducing corrosion of launch site equipment.

[0003] The preparation of aluminum-lithium alloy powder faces the following technical challenges: Lithium has a melting point of only 180℃, while aluminum has a melting point of 660℃. Therefore, lithium evaporation is a problem during aluminum-lithium alloy smelting, making it difficult to control the alloy composition. Furthermore, the evaporated lithium vapor accumulates on the inner wall of the vacuum system, which can corrode the system's inner wall and pipes over time, shortening equipment lifespan. Due to the high activity of the powder, the preparation process requires inert gas protection and atomization, resulting in high production costs. In addition, high-temperature liquid aluminum is highly corrosive, easily dissolving the crucible and introducing impurities during smelting. Existing processes, such as those disclosed in patent CN120350270A, use silicon carbide crucibles for smelting without coatings or other protective measures. During smelting, the silicon carbide crucible surface is corroded, shortening its lifespan, and the alloy is contaminated by Si and C, affecting its composition and performance. Patent CN119614259B uses a vacuum arc melting process for aluminum-lithium alloy smelting. The high temperature generated by the arc melting causes severe Li volatilization, leading to uncontrollable alloy composition.

[0004] Therefore, the present invention provides an aluminum-lithium alloy powder preparation apparatus and preparation process to solve the above problems. Summary of the Invention

[0005] The technical problem to be solved by this invention is that lithium evaporation occurs during the smelting of aluminum-lithium alloys, making it difficult to control the alloy composition. Furthermore, the evaporated lithium vapor accumulates on the inner wall of the vacuum system, and long-term adhesion will corrode the inner wall and pipes of the vacuum system, shortening the equipment life. Due to the high activity of the powder, the preparation process requires inert gas protection and atomization, resulting in high production costs. In addition, high-temperature liquid aluminum is highly corrosive and easily dissolves the crucible during the smelting process, bringing in impurities.

[0006] This invention provides the following technical solution: an aluminum-lithium alloy powder preparation device, including a melting chamber, a melting crucible and an intermediate ladle are arranged in the melting chamber, and a vacuum pump is arranged on the left side of the melting chamber; the inner wall of the melting crucible is coated with a boron nitride coating, the melting crucible is arranged on a tiltable movable support, and the bottom of the intermediate ladle is connected to a guide nozzle extending to the atomization chamber; An atomization chamber is located below the smelting chamber and is connected to the smelting chamber; An atomizing nozzle is disposed at the upper end of the atomizing chamber, corresponding to the guide nozzle. The atomizing nozzle includes an atomizing spray disc and the guide nozzle. The guide nozzle is an integral structure made of boron nitride. The atomizing spray disc is connected to a high-pressure atomizing gas pipeline. A dual-flow atomizing mechanism is provided in the atomizing chamber and includes an air intake shell located around the atomizing nozzle. The air intake shell includes an outer cover and an air curtain shell, which form a compressed air chamber. An elongated air curtain opening is provided on the air curtain shell. The gas recovery device, connected to the atomization chamber via a pipeline, includes an induced draft fan, an explosion-proof dust collector, and a gas booster pump. It is used to recover atomized gas. After being collected by the induced draft fan, the atomized gas is introduced into the high-pressure gas pipe above by the gas booster pump, and then further transported to the atomizing spray plate through the high-pressure atomized gas pipeline.

[0007] Preferably, the smelting crucible is made of high-purity graphite or corundum.

[0008] Preferably, a secondary feeding mechanism is also provided above the melting chamber. The secondary feeding mechanism includes multiple storage compartments for adding alloy raw materials at different melting stages.

[0009] Preferably, both the melting crucible and the tundish are surrounded by induction heating coils.

[0010] Preferably, a powder collection tank is provided at the lower end of the atomization chamber.

[0011] A process for preparing aluminum-lithium alloy powder, the process flow is as follows: S1. Melting: Place aluminum raw material and covering agent in a crucible with boron nitride coating on the inner wall, fill with inert gas to a slight positive pressure of 5~200 kPa under a vacuum of 10⁻³~10² Pa, heat to melt, add lithium raw material and optional yttrium raw material, and hold at 720~900°C for 10~15 min to obtain alloy liquid; S2. Atomization: The alloy liquid is heated to a casting temperature 150~250°C higher than the alloy melting point, and flows out through an integrated guide nozzle made of boron nitride material. Atomization is performed using atomizing gas of 0.5~6MPa. At the same time, the atomized droplets are protected by sheath flow through a dual-flow field auxiliary airflow. After cooling, the original powder is obtained. S3. Grading: The original powder is sieved and graded under inert gas protection to obtain aluminum-lithium alloy powder with the target particle size.

[0012] Preferably, the covering agent is composed of KCl, BaCl2, MgCl2, LiCl and AlF3 in a mass ratio of 2.5~4.2:1:30~35:5.5~6.5:11~13.

[0013] Preferably, the lithium and yttrium raw materials are wrapped in aluminum foil and then added through a secondary feeding mechanism.

[0014] Preferably, the atomizing gas pressure is 2.5~5.5MPa, the dual-flow-field auxiliary airflow pressure is 1~4.5MPa, the diameter of the guide nozzle is 3~8mm, and the casting temperature is 800~950°C.

[0015] Preferably, the grading is carried out using a mechanical vibrating screen or an air classifier under inert gas protection.

[0016] The beneficial effects of this invention are as follows: 1. This invention utilizes a dual corrosion-resistant protection system formed by a boron nitride coating on the inner wall of the melting crucible and an integrated boron nitride nozzle. This effectively isolates the graphite / corundum crucible and nozzle from the erosion and dissolution by the high-temperature aluminum-lithium melt, increasing the alloy purity to over 99.5%. The use of a vacuum pump for pre-vacuuming combined with inert gas micro-positive pressure protection during melting reduces the lithium volatilization loss rate from 15%–20% in traditional processes to below 5%, with alloy composition deviation controlled within ±0.3%. The dual-flow atomization mechanism forms a top-to-bottom sheath airflow through a compressed air chamber and a long, narrow gas curtain. The atomized droplets are cooled and spherical under a regular trajectory, reducing the proportion of satellite powder by more than 40% and achieving a powder sphericity of over 90%. The gas recovery device uses an induced draft fan for collection, an explosion-proof dust collector for purification, and a gas booster pump for compression to form a closed-loop cycle, achieving an inert gas reuse rate of over 85% and reducing overall production costs by more than 30%. The synergistic effect of the above structures not only solves the problems of uncontrolled composition, impurity contamination, excessive satellite powder, and high costs in existing technologies, but also extends the service life of equipment, realizing the continuous, efficient, low-cost, and high-quality preparation of aluminum-lithium alloy powder.

[0017] 2. This invention utilizes a secondary feeding mechanism with multiple storage compartments above the melting chamber. Highly active lithium and yttrium raw materials are wrapped in aluminum foil and added precisely in stages. This effectively avoids the severe volatilization and burning loss of these low-melting-point elements during prolonged heating, increasing the lithium yield to over 95%. Simultaneously, it significantly shortens the residence time of these elements in the high-temperature melt, substantially reducing the corrosion risk to the vacuum system and crucible. The covering agent employs a five-component composite system of KCl, BaCl2, MgCl2, LiCl, and AlF3 to form a dense and stable protective layer on the melt surface. This layer synergistically inhibits lithium volatilization through the copper ion effect and chemical adsorption. The process significantly improves batch-to-batch consistency of alloy composition. Precise control of the melting temperature at 720–900℃ and holding for 10–15 minutes, along with setting the casting temperature to the high-temperature alloy melting point of 150–250℃, ensures sufficient element diffusion and miscibility while balancing melt flowability and element burn-off. The high coupling between these process parameters and the equipment structure allows for precise adjustment of powder particle size within a wide range of 0.1–45 μm, resulting in a narrow particle size distribution, oxygen content <0.1 wt%, and a 15%–20% increase in overall yield. This meets the stringent requirements of solid propellants for precise composition, excellent morphology, and batch-to-batch stability of aluminum-lithium alloy powder.

[0018] 3. This invention achieves precise temperature control in the melting zone and the holding pouring zone by winding independent induction heating coils around the periphery of the melting crucible and the tundish. This effectively avoids problems such as sudden temperature drops, viscosity changes, and fluidity deterioration of the molten metal during transfer caused by traditional single-point heating. The tundish can be preheated to the optimal pouring temperature and maintained at a constant temperature, ensuring that the alloy liquid enters the atomization chamber in a stable flow state, significantly improving the continuity and stability of atomization. The diameter of the guide nozzle is precisely controlled at 3-8mm and optimally matched with the atomizing gas pressure of 2.5-5.5MPa and the dual-flow field auxiliary airflow pressure of 1-4.5MPa. This prevents nozzle blockage caused by excessively small orifice diameter and avoids insufficient atomization caused by excessively large orifice diameter, allowing the median diameter of the powder to be precisely controlled within the range of 2-30μm. The grading process is carried out using a mechanical vibrating screen or air classifier under inert gas protection, so that atomization, collection, and grading are seamlessly connected in a closed system without exposure during transfer, eliminating the risk of oxidation and combustion of highly active powders. The entire process is completed continuously under vacuum-inert gas protection. Attached Figure Description

[0019] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is an overall schematic diagram of the present invention; Figure 2 This is a schematic diagram of the process flow of the present invention.

[0021] In the diagram: 1. Melting crucible; 2. Feeding mechanism; 3. Moving support; 4. Vacuum pump; 5. Tundish; 6. Guide nozzle; 7. Atomizing spray plate; 8. Outer casing; 9. Gas curtain shell; 10. Explosion-proof dust collector; 11. Powder collection tank; 12. High-pressure gas tank; 13. Gas booster pump; 14. Exhaust fan; 15. Gas curtain outlet. Detailed Implementation

[0022] like Figure 1 As shown, an aluminum-lithium alloy powder preparation device includes a melting chamber, in which a melting crucible 1 and an intermediate ladle 5 are arranged, and a vacuum pump 4 is arranged on the left side of the melting chamber; the inner wall of the melting crucible 1 is coated with a boron nitride coating, the melting crucible 1 is arranged on a tiltable movable support 3, and the bottom of the intermediate ladle 5 is connected to a guide nozzle 6 extending to the atomization chamber. An atomization chamber is located below the smelting chamber and is connected to the smelting chamber; An atomizing nozzle is disposed at the upper end of the atomizing chamber and corresponds to the guide nozzle 6. The atomizing nozzle includes an atomizing spray disc 7 and the guide nozzle 6. The guide nozzle 6 is an integral structure made of boron nitride. The atomizing spray disc 7 is connected to a high-pressure atomizing gas pipeline. A dual-flow atomizing mechanism is provided in the atomizing chamber and includes an air intake shell located around the atomizing nozzle. The air intake shell includes an outer cover shell 8 and an air curtain shell 9, which form a compressed air chamber. An elongated air curtain opening 15 is provided on the air curtain shell 9. The gas recovery device, connected to the atomization chamber via a pipeline, includes an induced draft fan 14, an explosion-proof dust collector 10, and a gas booster pump 13, for recovering atomized gas. The atomized gas is collected by the induced draft fan 14 and introduced into the high-pressure gas tank 12 above through the gas booster pump 13, and then further transported to the atomizing spray plate 7 through the high-pressure atomized gas pipeline. The melting chamber includes a melting crucible 1, an tundish 5, and a secondary feeding mechanism 2. The melting crucible 1 is mounted on a movable support 3, which is equipped with a tilting mechanism to control the pouring of molten metal from the crucible 1 into the tundish 5. The crucible is made of high-purity graphite or corundum, and its inner wall is pre-coated with boron nitride. The tundish 5 is located at the junction of the melting chamber and the atomization chamber, with a molten metal outlet channel extending to the atomization chamber at its bottom. Both the melting crucible 1 and the tundish 5 are wound with induction heating coils for melting and heat preservation of the metal materials. The secondary feeding mechanism 2 is located above the melting chamber and consists of multiple compartments for separate material storage. Various alloy materials can be added to the molten metal in the crucibles at appropriate melting times via vacuum gate valves and vibrating feeders.

[0023] The atomizing chamber is connected to the melting chamber and includes an atomizing nozzle and a dual-flow atomizing mechanism. The atomizing nozzle is located at the connection between the upper end of the atomizing chamber and the melting chamber, and includes an atomizing spray plate 7 and a guide nozzle 6, used to spray the molten metal flowing out of the molten metal discharge channel into the atomizing chamber.

[0024] The atomizing spray disc 7 is connected to a high-pressure atomizing gas pipeline. The guide nozzle 6 is an integrated boron nitride nozzle, which can prevent corrosion from molten aluminum-lithium alloy that could damage the nozzle structure during atomization and improve atomization efficiency and energy utilization. The dual-flow atomization mechanism includes an air intake shell and an air curtain 15. The air intake shell consists of an outer cover 8 and an air curtain 9, with a compressed air chamber formed between the outer cover 8 and the air curtain 9. The air curtain 15 is located at the center of the air curtain 9 and extends to both sides in a long strip shape, connecting the compressed air chamber and the atomization chamber.

[0025] A high-pressure air intake pipe is provided on the outer casing 8, with one end extending into the compressed air chamber. Gas enters the atomization chamber through the air curtain 15. A powder collection tank 11 is provided at the lower end of the atomization chamber. The collection tank is used to collect the metal powder prepared by atomization. A gas recovery device is provided on the side of the atomization chamber, including an induced draft fan 14, an explosion-proof dust collector 10, a gas compressor, and an airflow pipe. The gas recovery device is used to recover the gas ejected from the atomizing nozzle and the air curtain 15, realizing gas recycling.

[0026] During operation, workers load aluminum raw materials and a covering agent into a melting crucible 1, whose inner wall is coated with boron nitride. Lithium and yttrium are placed in a secondary feeding mechanism 2. Simultaneously, a vacuum pump 4 is activated to evacuate the melting chamber to a set value. After the system is filled with inert gas to establish a slightly positive pressure protective atmosphere, the induction heating coil is activated to melt the raw materials into molten metal. Lithium and yttrium are then added through the secondary feeding mechanism 2 and alloyed at a set temperature. After the alloy liquid is heated to the casting temperature, a moving support 3 rotates the crucible to inject the molten liquid into the intermediate casting chamber. Package 5: The molten metal flows into the atomization chamber through the integrated boron nitride guide nozzle 6; the atomizing spray plate 7 is connected to high-pressure atomizing gas to fully break up the alloy liquid; at the same time, the high-pressure gas in the compressed air chamber of the dual-flow atomization mechanism is ejected through the long strip-shaped air curtain 15 to form a sheath airflow from top to bottom, so that the atomized droplets move regularly, cool and spheroidize into powder and fall into the collection tank; during the atomization process, the induced draft fan 14 continuously collects the atomized gas, which is purified by the explosion-proof dust collector 10 and then pressurized by the gas booster pump 13 and sent back to the high-pressure atomizing gas pipeline for recycling.

[0027] The boron nitride coating on the inner wall of the melting crucible 1 and the boron nitride integrated guide nozzle 6 form a double corrosion-resistant protection, effectively preventing the high-temperature aluminum-lithium melt from eroding and dissolving the crucible and nozzle, and significantly improving the purity and composition stability of the alloy. The vacuum pump 4 is used to draw a vacuum and the inert gas is used to protect the melting process with micro-positive pressure, which greatly suppresses the volatilization loss of low-boiling-point lithium elements and keeps the alloy composition deviation within a very small range. The dual-flow atomization mechanism forms a sheath airflow from top to bottom through the compressed air chamber and the long strip-shaped gas curtain 15, which makes the atomized droplets move regularly and reduces mutual collision and adhesion, effectively reducing the proportion of satellite powder and improving the sphericity and particle size distribution accuracy of the powder. The gas recovery device uses a closed loop of collection by the induced draft fan 14, purification by the explosion-proof dust collector 10, and compression by the gas booster pump 13 to realize the reuse of inert gas and reduce gas consumption costs by more than 30%. The synergistic effect of the above structures not only solves the problems of difficult composition control, impurity contamination, large amount of satellite powder, and high cost in the existing technology, but also extends the service life of the equipment and realizes the continuous, efficient, low-cost and high-quality preparation of aluminum-lithium alloy powder.

[0028] like Figure 1As shown, the melting crucible 1 is made of high-purity graphite or corundum. Using high-purity graphite or corundum as the material of the melting crucible 1 can withstand the high-temperature environment required for aluminum-lithium alloy melting without softening or deformation. Its high purity fundamentally reduces the risk of contamination of the alloy liquid by the precipitation of impurities in the crucible itself. Combined with the synergistic protective effect of the boron nitride coating on the inner wall, it effectively isolates the crucible substrate from the erosion and dissolution of high-temperature liquid aluminum, significantly improving the purity and compositional stability of the alloy product. At the same time, the excellent thermal shock resistance of these two materials ensures that the crucible is not prone to cracking under repeated heating and cooling conditions during the melting process, extending the service life of the equipment and reducing maintenance costs.

[0029] like Figure 1 As shown, a secondary feeding mechanism 2 is also provided above the melting chamber. The secondary feeding mechanism 2 includes multiple storage compartments for adding alloy raw materials at different melting stages. By setting up a secondary feeding mechanism 2 with multiple storage compartments above the melting chamber, the defects of traditional one-time feeding, such as the violent volatilization and burning loss of low melting point and high-activity alloy elements (such as lithium and yttrium) during long-term heating, and the difficulty in accurately controlling the composition, are effectively overcome. This achieves the technical effect of adding the main raw materials and volatile elements in stages, at time, and in quantities. This not only significantly improves the stability and batch consistency of the alloy composition, but also enhances the process flexibility, making it possible to accurately formulate complex multi-component aluminum-lithium alloys. At the same time, it reduces the early oxidation risk of high-activity raw materials and ensures production safety and product quality controllability.

[0030] like Figure 1 As shown, both the melting crucible 1 and the tundish 5 are surrounded by induction heating coils. By winding induction heating coils around the melting crucible 1 and the tundish 5 respectively, independent and precise temperature control of the melting zone and the heat preservation casting zone is achieved. This effectively avoids problems such as sudden temperature drop, viscosity change and fluidity deterioration of the molten liquid during the transfer process caused by traditional single-point heating. The tundish 5 can be preheated to the optimal casting temperature and kept at a constant temperature, ensuring that the alloy liquid enters the atomization chamber in a stable flow state. This significantly improves the continuity and stability of the atomization process. At the same time, the rapid response characteristics of induction heating make temperature regulation more precise, reduce energy waste, and improve process controllability and production efficiency.

[0031] like Figure 1As shown, a powder collection tank 11 is provided at the lower end of the atomization chamber. By directly setting the powder collection tank 11 at the lower end of the atomization chamber, the principle of gravity settling after the atomized droplets are broken by gas and cooled into spherical shapes is effectively utilized. This achieves the immediate and sealed collection and temporary storage of aluminum-lithium alloy powder in an inert protective atmosphere, avoiding the risks of oxidation, moisture absorption, and combustion and explosion caused by long-distance transportation or exposure to open environments of highly active powders. This significantly improves product purity and production safety. At the same time, this structure allows for seamless connection between the atomization and collection processes, reducing material transfer links and equipment complexity. This not only improves the overall process continuity and production efficiency but also facilitates direct docking with the grading device under inert gas protection, reducing dust pollution and material loss.

[0032] like Figure 2 As shown, a process for preparing aluminum-lithium alloy powder is described below: S1. Melting: Place aluminum raw material and covering agent in a crucible with boron nitride coating on the inner wall, fill with inert gas to a slight positive pressure of 5~200 kPa under a vacuum of 10⁻³~10² Pa, heat to melt, add lithium raw material and optional yttrium raw material, and hold at 720~900°C for 10~15 min to obtain alloy liquid; S2. Atomization: The alloy liquid is heated to a casting temperature 150~250°C higher than the alloy melting point, and flows out through an integrated boron nitride nozzle 6. Atomization is performed using atomizing gas of 0.5~6MPa. At the same time, the atomized droplets are protected by sheath flow through a dual-flow field auxiliary airflow. After cooling, the original powder is obtained. S3. Grading: The original powder is sieved and graded under inert gas protection to obtain aluminum-lithium alloy powder with the target particle size.

[0033] By employing a boron nitride-coated crucible and a slightly positive pressure inert atmosphere for melting, the erosion of the crucible wall by the high-temperature aluminum-lithium melt is fundamentally isolated, and the volatilization loss of low-boiling-point lithium is significantly suppressed, keeping the alloy composition deviation within ±0.3%. By precisely limiting the melting temperature to 720~900℃ and holding it for 10~15 minutes, the alloy elements are ensured to diffuse and mix fully while avoiding excessive burn-off, achieving high compositional uniformity and stability. By setting the pouring temperature to the high-temperature alloy melting point of 150~250℃ and using an integrated boron nitride nozzle, the contradiction between melt flowability and element volatilization is effectively balanced, eliminating the risk of nozzle blockage and maintaining melt purity. The process utilizes high-pressure atomization at 0.5–6 MPa under dual-flow-field assisted airflow sheath protection, enabling precise control of powder particle size across a wide range of 0.1–45 μm. Furthermore, the regular guidance of the sheath airflow prevents atomized droplets from colliding and sticking, reducing the proportion of satellite powder by over 40% and increasing powder sphericity to over 90%. The entire process, involving continuous melting, atomization, and grading under vacuum-inert gas protection, allows for oxygen content controllable below 0.1 wt%, resulting in aluminum-lithium alloy powder with a purity exceeding 99.5% and an overall yield increase of 15%–20%. This provides high-quality raw materials with precise composition, excellent morphology, and controllable cost for applications such as solid propellants.

[0034] The aluminum-lithium alloy powder produced by the above process is composed of the following components, calculated based on a total chemical element composition of 100 wt.% (all values ​​are by mass): 0.5~20.0 wt.% Li; 0.05~15.0 wt.% Mg; 0.05-15.0 wt.% Y; with the balance being Al and unavoidable impurities.

[0035] The powder particle size distribution is a median diameter of 0.1 ≤ D50 ≤ 45 μm, preferably a median diameter D50 of any one of the following: 29 ± 3 μm, 24 ± 3 μm, 17 ± 2 μm, 13 ± 2 μm, 6 ± 1.5 μm, or 2 ± 1 μm, or a combination thereof. The particle size distribution is determined by laser scattering / diffraction.

[0036] like Figure 2As shown, the covering agent is composed of KCl, BaCl2, MgCl2, LiCl, and AlF3 in a mass ratio of 2.5~4.2:1:30~35:5.5~6.5:11~13. The covering agent, through a five-component compound of KCl, BaCl2, MgCl2, LiCl, and AlF3 in a mass ratio of 2.5~4.2:1:30~35:5.5~6.5:11~13, forms a synergistic molten salt protective layer. MgCl2 serves as the main component, providing a stable liquid-phase covering base, while KCl and BaCl2 precisely control the melting point and viscosity of the molten salt, keeping it within the range of 720~900 °C. While maintaining fluidity at a melting temperature of ℃, LiCl significantly inhibits the chemical activity and volatility of lithium in the alloy melt through the common ion effect, while AlF3 plays a refining and impurity removal role and absorbs oxide inclusions. This specific ratio enables the covering agent to form a dense and continuously stable protective barrier on the melt surface, reducing the lithium burn-off rate from 15% to 20% in traditional processes to below 5%, and reducing the alloy composition deviation from ±1% to within ±0.3%. At the same time, it reduces the corrosion of the vacuum system by lithium vapor, extends the service life of equipment, and achieves energy saving and consumption reduction by lowering the melting temperature requirement. Overall, it improves the compositional stability and batch consistency of aluminum-lithium alloy powder.

[0037] like Figure 2 As shown, the lithium and yttrium raw materials are wrapped in aluminum foil and added through a secondary feeding mechanism 2. By wrapping the highly active lithium and yttrium raw materials in aluminum foil and adding them in stages using the secondary feeding mechanism 2, the severe oxidation and volatilization losses caused by prolonged high-temperature exposure of these low-melting-point and easily oxidized elements in the early stages of smelting are effectively avoided. This increases the lithium yield to over 95%, and the alloy composition is precisely controllable. The aluminum foil wrapping provides both physical isolation and protection, and allows the materials to melt rapidly in the melt and become part of the alloy composition. This simplifies the feeding operation and prevents the raw materials from adhering to the inner wall of the equipment. The secondary feeding mechanism 2 achieves the technical effect of precisely adding active elements only when the aluminum matrix is ​​completely melted and reaches the optimal alloying temperature. This significantly shortens the residence time of lithium and yttrium in the high-temperature melt, significantly reduces their corrosion of the vacuum system and crucible, and ensures the uniformity of the alloy composition and batch stability, thereby improving production safety and product quality consistency.

[0038] like Figure 2As shown, the atomizing gas pressure is 2.5~5.5MPa, the dual-flow-field auxiliary airflow pressure is 1~4.5MPa, the diameter of the guide nozzle 6 is 3~8mm, and the casting temperature is 800~950°C. By optimizing the atomizing gas pressure to 2.5~5.5MPa and combining it with the dual-flow-field auxiliary airflow pressure of 1~4.5MPa, a gradient airflow field is formed that coordinates the main atomization and breakup with the sheath flow protection. This ensures that the melt is fully broken into fine droplets and that the atomized droplets cool and spheroidize under a regular motion trajectory, effectively avoiding collision and adhesion between droplets. This reduces the proportion of satellite powder by more than 40% and increases the powder sphericity to more than 90%. The diameter of the guide nozzle 6 is precisely controlled within the range of 3~8mm. The process achieves optimal matching with the aforementioned atomization pressure, ensuring stable melt flow and concentrated atomization focus. This prevents nozzle clogging caused by excessively small orifice size while avoiding insufficient atomization due to excessively large orifice size, thus enabling continuous and stable production. The casting temperature is set at 800–950℃ (150–250℃ higher than the alloy melting point). This ensures good melt flowability and smooth passage through the guide nozzle 6 while effectively suppressing excessive volatilization of low-boiling-point lithium and magnesium elements, keeping the element burn-off rate below 5% and the alloy composition deviation below ±0.3%. The synergistic optimization of the above process parameters allows for precise control of powder particle size within a wide range of 0.1–45 μm, resulting in narrow particle size distribution, good batch consistency, and an overall yield increase of 15%–20%.

[0039] like Figure 2 As shown, the grading is carried out using a mechanical vibrating screen or an air classifier under inert gas protection. By using a mechanical vibrating screen or an air classifier to grade the powder in an inert gas protected environment, not only can the grading method be flexibly selected according to the target particle size range to achieve efficient sieving, but more importantly, it fundamentally eliminates the risk of oxidation, combustion, or even explosion caused by the high-activity aluminum-lithium alloy powder coming into contact with air during the grading process. This ensures that the oxygen content of the powder is controlled below 0.1wt%, maintaining the purity and batch stability of the alloy composition. At the same time, it allows the grading process to be continuously connected with the front-end atomization and the back-end collection in a closed inert atmosphere system without exposure or transfer, greatly improving production safety and process continuity, and reducing product loss and quality risks.

[0040] This embodiment also provides an example of aluminum-lithium alloy powder production, wherein the alloy chemical composition by mass percentage is: ; The preparation steps are as follows: Based on the chemical composition of the aluminum-lithium alloy powder, high-purity aluminum ingots, metallic lithium, aluminum-magnesium alloy, and metallic yttrium were weighed. The aluminum ingots, aluminum-magnesium alloy, and covering agent were placed in an alumina melting crucible 1 coated with boron nitride. The metallic lithium and metallic yttrium were wrapped in aluminum foil and placed in a secondary feeding mechanism 2. The covering agent consisted of KCl, BaCl2, MgCl, LiCl, and AlF3 in a mass ratio of 3.5:1:32:6:12. The apparatus was evacuated to 10 Pa and then filled with argon gas to 102 kPa.

[0041] The induction heating power supply is turned on, and the temperature is raised to 750℃ to completely melt the raw materials into molten metal. Lithium and yttrium are added through the secondary feeding mechanism 2. The mixture is held at this temperature for 15 minutes to allow for full diffusion of the elements, resulting in a homogeneous alloy liquid. The power is adjusted to rapidly raise the solution temperature to 830℃. The power is then adjusted further to stabilize the alloy liquid at 830℃ before casting begins. The aluminum-lithium alloy liquid is atomized and broken up using argon gas at a pressure of 4.5 MPa. A dual-flow field auxiliary airflow of 3 MPa is activated. After cooling, the original aluminum-lithium alloy powder is obtained. Simultaneously, the induced draft fan 14 is activated to recover the atomizing gas and auxiliary flow field gas into the gas tank.

[0042] The raw aluminum-lithium alloy powder was sieved in a glove box or an ultrasonic vibrating screen with inert gas protection. Fine powder was removed by sieving with an 800-mesh screen and coarse powder was removed by sieving with a 400-mesh screen, resulting in aluminum-lithium alloy powder with a median diameter of 16 μm.

[0043] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. An apparatus for preparing aluminum-lithium alloy powder, characterized in that, The system includes a melting chamber, which is equipped with a melting crucible (1) and an intermediate ladle (5). A vacuum pump (4) is installed on the left side of the melting chamber. The inner wall of the melting crucible (1) is coated with a boron nitride coating. The melting crucible (1) is mounted on a tiltable movable support (3). The bottom of the intermediate ladle (5) is connected to a guide nozzle (6) extending to the atomization chamber. An atomization chamber is located below the smelting chamber and is connected to the smelting chamber; An atomizing nozzle is located at the upper end of the atomizing chamber and corresponds to the guide nozzle (6). The atomizing nozzle includes an atomizing spray disc (7) and the guide nozzle (6). The guide nozzle (6) is an integral structure made of boron nitride. The atomizing spray disc (7) is connected to a high-pressure atomizing gas pipeline. The dual-flow atomizing mechanism is located in the atomizing chamber and includes an air intake shell located around the atomizing nozzle. The air intake shell includes an outer cover (8) and an air curtain shell (9), which form a compressed air chamber. The air curtain shell (9) has an elongated air curtain opening (15). The gas recovery device is connected to the atomization chamber via a pipeline and includes an induced draft fan (14), an explosion-proof dust collector (10), and a gas booster pump (13) for recovering atomized gas. The atomized gas is collected by the induced draft fan (14), introduced into the high-pressure gas tank (12) above by the gas booster pump (13), and then transported to the atomizing spray plate (7) through the high-pressure atomized gas pipeline.

2. The aluminum-lithium alloy powder preparation apparatus according to claim 1, characterized in that: The smelting crucible (1) is made of high-purity graphite or corundum.

3. The aluminum-lithium alloy powder preparation apparatus according to claim 2, characterized in that: A secondary feeding mechanism (2) is also provided above the melting chamber. The secondary feeding mechanism (2) includes multiple storage compartments for adding alloy raw materials at different melting stages.

4. The aluminum-lithium alloy powder preparation apparatus according to claim 3, characterized in that: Both the melting crucible (1) and the tundish (5) are surrounded by induction heating coils.

5. The aluminum-lithium alloy powder preparation apparatus according to claim 4, characterized in that: A powder collection tank (11) is provided at the lower end of the atomization chamber.

6. A process for preparing aluminum-lithium alloy powder, characterized in that, The apparatus for preparing aluminum-lithium alloy powder according to any one of claims 1 to 5 has the following process flow: S1. Melting: Place aluminum raw material and covering agent in a crucible with boron nitride coating on the inner wall, fill with inert gas to a slight positive pressure of 5-200 kPa under a vacuum of 10⁻³~10² Pa, heat to melt, add lithium raw material and optional yttrium raw material, and hold at 720~900°C for 10~15 min to obtain alloy liquid; S2. Atomization: The alloy liquid is heated to a casting temperature 150-250°C higher than the alloy melting point, and flows out through an integrated guide nozzle (6) made of boron nitride material. Atomization is performed using atomizing gas of 0.5-6MPa. At the same time, the atomized droplets are protected by sheath flow through a dual-flow field auxiliary airflow. After cooling, the original powder is obtained. S3. Grading: The original powder is sieved and graded under inert gas protection to obtain aluminum-lithium alloy powder with the target particle size.

7. The preparation process of aluminum-lithium alloy powder according to claim 6, characterized in that: The covering agent is composed of KCl, BaCl2, MgCl2, LiCl and AlF3 in a mass ratio of 2.5-4.2:1:30-35:5.5-6.5:11-13.

8. The preparation process of aluminum-lithium alloy powder according to claim 7, characterized in that: The lithium and yttrium raw materials are wrapped in aluminum foil and then added through a secondary feeding mechanism (2).

9. The preparation process of aluminum-lithium alloy powder according to claim 8, characterized in that: The atomizing gas pressure is 2.5 to 5.5 MPa, the dual-flow field auxiliary airflow pressure is 1 to 4.5 MPa, the diameter of the guide nozzle (6) is 3 to 8 mm, and the casting temperature is 800 to 950°C.

10. The preparation process of aluminum-lithium alloy powder according to claim 9, characterized in that: The grading is carried out using a mechanical vibrating screen or an air classifier under inert gas protection.

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