A magnesium-lithium binary alloy powder and a method for preparing the same

Abstract

The application provides a magnesium-lithium binary alloy fuel powder and a preparation method thereof. The magnesium-lithium binary alloy fuel powder contains 3-20% of lithium in mass, preferably 3-15%, and the sphericity is not less than 95%. The preparation method comprises the following steps: under the condition of argon positive pressure, melting the metal containing magnesium and lithium in a silicon carbide / high-purity graphite corrosion-resistant crucible melting furnace, and then delivering the obtained magnesium-lithium binary alloy liquid to a tightly-coupled gas atomization tank for atomization, and obtaining the magnesium-lithium binary alloy fuel powder after screening. The magnesium-lithium binary alloy fuel prepared by the application can not only maintain the low reaction temperature of the fuel, but also improve the oxidation reaction rate of the fuel, greatly improve the combustion rate of the fuel air explosive and magnesium water propellant, and further improve the energy.

Description

Technical Field

[0001] This invention relates to the field of alloys, and more specifically, to a magnesium-lithium binary alloy powder and its preparation method. Background Technology

[0002] Magnesium powder is a low-reaction-temperature metallic fuel with a high calorific value, widely used in various energetic materials such as thermobaric explosives, underwater explosives, fuel-air explosives, and magnesium-water propellants. However, magnesium has a high activation energy for oxidation, resulting in a low oxidation rate of magnesium powder when reacting with air in fuel-air explosives, leading to incomplete combustion. In magnesium-water propellants, the reaction between magnesium powder and water vapor is slow, causing unstable combustion. Lithium metal has a calorific value of 45.8 kJ / g, 1.75 times that of magnesium, and a higher oxidation rate. However, lithium is an extremely reactive metal and cannot be used alone in energetic materials.

[0003] Lithium metal is too reactive to be used alone to prepare fuel powder, while magnesium water propellant has the problem of unstable combustion. There is no existing technology for preparing magnesium-lithium alloy fuel powder. Summary of the Invention

[0004] In order to solve the technical problems existing in the prior art, the present invention provides a magnesium-lithium binary alloy fuel powder and its preparation method.

[0005] This invention creates a series of magnesium-lithium binary alloy fuels by combining magnesium and lithium in different proportions. This solves the problems of slow reaction between magnesium powder and water vapor in magnesium-water propellant, which leads to unstable combustion of magnesium-water propellant, and the problem that lithium metal is reactive but cannot be used alone. By combining the two to create magnesium-lithium binary alloy fuels, the invention can maintain a low reaction temperature of the fuel while increasing the oxidation reaction rate of the fuel. This can significantly improve the combustion rate of fuel-air explosives and magnesium-water propellants, thereby increasing energy.

[0006] One of the features of this method is that, based on magnesium powder fuel with a low reaction temperature, metallic lithium with a high oxidation reaction rate is introduced, and a magnesium-lithium binary alloy fuel with a low reaction temperature and a high reaction rate is designed by applying the theories of fuel combustion thermodynamics, combustion kinetics and alloy thermodynamics.

[0007] The second characteristic of this method is the comprehensive application of atomization powdering technology centered on "closely coupled gas atomization / high-speed argon condensation." The basic principle is to use a high-speed gas flow to pulverize a liquid metal stream into small droplets and rapidly solidify them into fine powder. The core is controlling the interaction between the gas and the liquid metal stream, maximizing the conversion of the gas flow's kinetic energy into the surface energy of the newly formed powder. All atomization processes require control of gas velocity, gas flow rate, and gas flow direction. Furthermore, to improve atomization efficiency, the closely coupled gas atomization equipment improves the nozzle structure, minimizing the distance from the gas outlet to the liquid stream, thus increasing the efficiency of gas kinetic energy transfer to the liquid metal stream. Compared to mechanical methods and ordinary centrifugal atomization, closely coupled gas atomization results in faster droplet flight speeds and shorter cooling times, leading to higher magnesium-lithium solid solubility, denser powder, better sphericity, and smaller particle size.

[0008] The third characteristic of this method is that it uses a "silicon carbide / high-purity graphite" corrosion-resistant crucible to melt the alloy and a "niobium alloy liner / stainless steel jacket" corrosion-resistant pipeline to transport the high-temperature liquid material, so as to prevent impurities from being introduced during the atomization process and to suppress the evaporation of lithium, thus ensuring the high purity and lithium content of the ternary alloy powder.

[0009] The fourth characteristic of this method is the use of a full-process "oxygen-free closed-loop / argon positive pressure" gas and material path control to ensure the safety of batch powder production.

[0010] One of the objectives of this invention is to provide a magnesium-lithium binary alloy fuel powder.

[0011] The lithium content in the magnesium-lithium binary alloy powder is 3% to 20% by mass; preferably 3% to 15%.

[0012] The density of the magnesium-lithium binary alloy powder is 1.50–1.70 g / cm³. 3 The preferred value is 1.56–1.70 g / cm³. 3 ;

[0013] The calorific value is 25.21–29.49 kJ / g, preferably 25.21–27.49 kJ / g;

[0014] The ignition temperature is 320.0–589.0℃, preferably 428.5–486.2℃;

[0015] The activation energy is 33.0–226.6 kJ / mol, preferably 60.1–226.6 kJ / mol;

[0016] The sphericity of the magnesium-lithium binary alloy powder is not less than 95%.

[0017] A second objective of this invention is to provide a method for preparing magnesium-lithium binary alloy fuel powder, comprising:

[0018] (1) Under positive pressure of argon, the metal containing magnesium and lithium is melted in a silicon carbide / high-purity graphite anti-corrosion crucible melting furnace to obtain magnesium-lithium binary alloy liquid.

[0019] (2) Under positive pressure of argon, magnesium-lithium binary alloy liquid is transported to a tightly coupled gas atomizing tank through a stainless steel conveying pipe. After being atomized by tightly coupled gas and screened, the magnesium-lithium binary alloy fuel powder is obtained.

[0020] The silicon carbide / high-purity graphite corrosion-resistant crucible melting furnace is a crucible with a stainless steel outer shell and an inner lining made of a mixture of silicon carbide and graphite in a ratio of approximately 50:50.

[0021] In a preferred embodiment of the present invention,

[0022] Step (1),

[0023] In the magnesium-lithium binary alloy base alloy, the lithium mass content is 3% to 20%; preferably 3% to 15%.

[0024] In a preferred embodiment of the present invention,

[0025] Step (1),

[0026] The oxygen volume content in the "silicon carbide / high-purity graphite" corrosion-resistant crucible melting furnace is kept to no more than 0.01% by vacuuming and purging with argon.

[0027] During the melting process, the positive pressure of argon gas is in the range of 103 kPa to 105 kPa;

[0028] The melting superheat is 90℃~180℃;

[0029] The melting temperature is 650–750℃;

[0030] The melting time is 1 to 2 hours.

[0031] In a preferred embodiment of the present invention,

[0032] Step (2),

[0033] The oxygen volume content in the tightly coupled gas atomizer is kept no greater than 0.01% by evacuation and argon filling;

[0034] The positive pressure of argon gas in the tightly coupled gas atomizing canister and pipeline is 102 kPa to 105 kPa;

[0035] The pressure difference between the tightly coupled gas atomizing canister and the silicon carbide crucible melting furnace is 1 kPa to 2 kPa;

[0036] The mass flow rate of the liquid feed is 11 g / s to 14 g / s;

[0037] The high-pressure gas flow rate of the tightly coupled atomized gas is 25m.3 / h~30m 3 / h.

[0038] In a preferred embodiment of the present invention,

[0039] Step (2),

[0040] The tightly coupled atomizing canister has an annular slit atomizing nozzle, the diameter of which is 3mm to 8mm, preferably 3mm to 5mm.

[0041] The annular slit atomizing nozzle has a nozzle at its end, and the eccentricity angle of the nozzle is 3° to 7°, preferably 3° to 5°.

[0042] The stainless steel conveying pipe has a niobium alloy liner. Lithium alloy is corrosive, so a niobium alloy liner needs to be added.

[0043] The atomization pressure is 2.0MPa-3.0MPa.

[0044] In a preferred embodiment of the present invention,

[0045] Step (2),

[0046] Under positive pressure of argon gas, powder of different particle sizes is obtained by mechanical screening and airflow separation.

[0047] The third objective of this invention is to provide a magnesium-lithium binary alloy fuel powder prepared by the above-mentioned preparation method.

[0048] The present invention can specifically adopt the following technical solutions:

[0049] 1. Low-reaction-temperature, high-reaction-rate magnesium-lithium binary alloy fuels with three different alloy ratios

[0050] It utilizes the low reaction temperature of magnesium and the high reaction rate of lithium to achieve both low reaction temperature and high reaction rate.

[0051] (1) MgLi3 alloy fuel: theoretical density 1.70 g / cm³ 3 It has a theoretical calorific value greater than 26 kJ / g, and its main metallographic components are the magnesium solid solution phase α-Mg and the alloy compound Li3Mg. 17 ;

[0052] (2) MgLi5 alloy fuel: theoretical density 1.68 g / cm³ 3 It has a theoretical calorific value greater than 27 kJ / g, and its main metallographic composition consists of the solid solution phase of magnesium α-Mg and the alloying compound Li. 0.92 Mg 4.08 ;

[0053] (3) MgLi15 alloy fuel: theoretical density 1.56 g / cm³ 3 It has a theoretical calorific value greater than 28 kJ / g, and its main metallographic structure consists of lithium solid solution phases α-Mg and β-Li and alloy compound Li. 0.92 Mg 4.08 .

[0054] 2. Mass production method of magnesium-lithium binary alloy atomized spherical powder via "tightly coupled gas atomization / high-speed argon condensation"

[0055] This method integrates a tightly coupled gas atomization / argon high-speed condensation atomizing vessel, a corrosion-resistant crucible alloy melting furnace, a corrosion-resistant feed pipe, and a full-process oxygen-free closed-loop / argon positive pressure safety system. This ensures high purity, high sphericity, and high density of the powder while effectively guaranteeing production safety. The prepared magnesium-lithium binary alloy has low impurity content, low oxygen and nitrogen content, a powder density not less than 99% of the theoretical density, a loose packing density not less than 50% of the theoretical density, a sphericity not less than 95%, a smooth surface, and no satellite powder. The metallographic structure shows no severe segregation.

[0056] (1) Smelting magnesium-lithium binary basic alloy in a "silicon carbide / high-purity graphite" corrosion-resistant crucible

[0057] First, the MgLi15 base alloy is smelted. To prevent the liquid alloy from corroding the crucible and introducing impurities, and to effectively suppress lithium volatilization during the high-temperature smelting of the magnesium-lithium alloy, a silicon carbide / high-purity graphite corrosion-resistant crucible and precise temperature control technology using an argon positive pressure environment are employed. Metallic magnesium and lithium are placed in a... Figure 1 In the sealed melting furnace 1 shown, the furnace is first evacuated to 0.1 kPa and then filled with argon to 1 atm; the second evacuation is performed to 10 kPa and argon is filled to 1 atm. The superheat of the molten material is set to 90℃~180℃, therefore the temperature is controlled at 650℃~750℃. The oxygen content is monitored using an oxygen content detector until it is no more than 0.01% (sensor value). During the alloy melting process, the positive pressure of argon in the furnace is controlled within the range of 103 kPa~105 kPa. Argon stirring is used to achieve uniform composition, and the maximum batch size is 50 kg / batch.

[0058] (2) Smelting magnesium-lithium binary target alloy in a "silicon carbide / high-purity graphite" corrosion-resistant crucible

[0059] The first step in atomization powder production is to smelt the target alloy using MgLi15 base alloy and lithium ingots as raw materials.

[0060] Magnesium-lithium alloys with a target lithium content of less than 15%: The feed ratio and total yield are calculated according to formulas (1) and (2).

[0061]

[0062] M=M(Mg)+M(MgLi15) (2)

[0063] In equations (1) and (2), x represents the lithium content of the target alloy, and M(MgLi15), M(Li), M(Mg) and M represent the amount of base alloy, lithium metal, magnesium metal added, and the total amount of target alloy, respectively.

[0064] Similarly, to avoid the introduction of impurities due to corrosion of the crucible by the liquid alloy and to effectively suppress lithium volatilization during the high-temperature melting of magnesium-lithium alloys, a silicon carbide / high-purity graphite anti-corrosion crucible and precise temperature control technology using an argon positive pressure environment are employed. Metallic magnesium and the magnesium-lithium 15 base alloy are placed in a... Figure 1 In the sealed melting furnace 1 shown, the furnace is first evacuated to 0.1 kPa and then filled with argon gas to 1 atm; the second evacuation is performed to 10 kPa and then filled with argon gas to 1 atm. The oxygen content is monitored using an oxygen content detector until it is no more than 0.01% (sensor value). During the alloy melting process, the positive pressure of argon gas in the furnace is controlled within the range of 103 kPa to 105 kPa. Argon gas stirring is used to achieve uniform composition, and the maximum batch size is 50 kg / batch.

[0065] (3) Corrosion-resistant pipeline material transport with "niobium alloy lining / stainless steel outer layer"

[0066] To prevent the alloy molten material from corroding the pipeline and introducing impurities, a "niobium alloy liner / stainless steel jacket" conveying pipe and argon positive pressure conveying technology are used. Figure 1 As shown. The feed pipe is first evacuated to 0.1 kPa, then purged with argon to 1 atm; a second evacuation is performed to 10 kPa, followed by purging with argon to 1 atm. The positive pressure of argon relative to the atomizing tank in the feed pipe is controlled within the range of 102 kPa to 105 kPa. During the feed liquid delivery process, the atomizing gas pressure is adjusted using a pressure regulating valve to maintain it at approximately 2.0 MPa to 3.0 MPa. The atomization status and the operation of each instrument are continuously monitored during atomization for timely adjustments.

[0067] (4) "Tightly coupled gas atomization / argon high-speed condensation" atomization powder production

[0068] Feed flow rate control: Mass flow rate of feed liquid The temperature T of the smelting furnace and conveying pipeline, the difference between the furnace pressure P2 and the tank pressure P3, the length L and cross-sectional area S of the material conveying pipe in the atomizing tank are controlled by parameters such as the temperature T of the smelting furnace and conveying pipeline, the difference between the furnace pressure P2 and the tank pressure P3, and the length L and cross-sectional area S of the material conveying pipe in the atomizing tank, as shown in Equation (3).

[0069]

[0070] In equation (3), F1(β, T) is the resistance function of material conveying, and β is the resistance coefficient between the material and the pipe.

[0071] Gas flow rate control: High-pressure gas is transported through an argon cylinder. The gas flow rate is controlled by parameters such as the difference between furnace pressure P2 and cylinder pressure P3, gas cylinder pipe flow rate v1, gas delivery pipe length L2 of the annular nozzle, nozzle inclination angle α, and argon density. The material transport resistance function F2(β,T) is shown in equation (4).

[0072]

[0073] Tightly Coupled Gas Atomization Pressure and Flow Rate Control: Working Principle of Tightly Coupled Gas Atomizers (e.g.) Figure 2 The diameter of the annular slit-type gas atomizing nozzle is designed to be 3mm–5mm, and the pressure difference between the tank and the furnace is 1kPa–2kPa. Therefore, the mass flow rate of the liquid feed is controlled within the range of 11g / s–14g / s. The atomization pressure is 2.0–3.0 MPa, and the supersonic argon gas flow rate is 25m / s. 3 / h~30m 3 / h, nozzle eccentricity angle 3°~7°.

[0074] The relationship between atomization pressure and average powder particle size is as follows:

[0075]

[0076] In the formula, P is the atomization pressure; n and C are constants related to the equipment and melt properties.

[0077] The solidification time and spheroidization time of the liquid droplets are respectively:

[0078]

[0079] In the formula t sol For solidification time, t sph sphericization time, h c c is the heat transfer coefficient. p T is the specific heat of liquid metal. l T g T m These represent the superheat temperature of the liquid, the gas temperature, and the melting point of the liquid metal, respectively. ΔH is the enthalpy change.

[0080]

[0081] In the formula t sph Spheroidization time, V is the droplet volume; R and r are the radii of the droplet before and after spheroidization, respectively.

[0082] The implementation process of the method is as follows: Figure 3 As shown.

[0083] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0084] This invention utilizes a high-speed argon gas flow to pulverize liquid alloy flow into small droplets, which then rapidly solidify into powder. This results in a shorter cooling time. In the tightly coupled gas atomization method, the melting furnace and atomizing tank are placed vertically, and the feed pipe is shorter, which helps reduce impurities caused by pipeline corrosion. The valve in the middle of the feed pipe can control the flow rate of the liquid over a wide range.

[0085] By improving the nozzle structure to minimize the distance between the airflow outlet and the liquid flow, turbulence is created between the liquid material and the airflow in the atomization chamber, increasing the efficiency of the transfer of gas kinetic energy to the molten metal flow.

[0086] The prepared magnesium-lithium alloy powder has a median particle size of 5μm to 80μm, a sphericity of not less than 95%, a smooth surface, no satellite powder, a purity of more than 99.5%, a powder density of not less than 99% of the theoretical density, a loose packing density of not less than 50% of the theoretical density, a uniform metallographic structure, and no serious segregation. Attached Figure Description

[0087] Figure 1 A schematic diagram of the system equipment for preparing magnesium-lithium binary alloy powder;

[0088] Among them, 1 is a silicon carbide / high-purity graphite corrosion-resistant crucible melting furnace, 2 is a material conveying pipe, 3 is a tightly coupled gas atomizing canister, 4 is a mechanical screening machine, 5 is an airflow separator, and 6 is a high-pressure argon gas canister.

[0089] Figure 2 This is a schematic diagram of a tightly coupled gas atomizer in the system;

[0090] 3-1 Metal melt channel, 3-2 Gas channel, 3-3 Annular slit nozzle radius r, 3-4 Nozzle tilt angle α, 3-5 Gas outlet, 3-6 Melt outlet, 3-7 Metal melt;

[0091] Figure 3 Flowchart for the atomization powder production of magnesium-lithium binary alloy;

[0092] Figure 4 The image shows the surface morphology of the MgLi3 powder in Example 1 using SEM.

[0093] Figure 5 This is a partial magnified SEM image of the surface morphology of the MgLi3 powder in Example 1.

[0094] Figure 6 Metallographic photograph of MgLi3 powder in Example 1;

[0095] Figure 7 This is a graph showing the oxidation reaction rate of MgLi3 powder in Example 1;

[0096] Where the left vertical axis represents mass change and the right vertical axis represents heat flow;

[0097] Figure 8 The image shows the surface morphology of the MgLi5 powder in Example 2 using SEM.

[0098] Figure 9 This is a partial magnified SEM image of the surface morphology of MgLi5 powder in Example 2;

[0099] Figure 10 Metallographic photograph of MgLi5 powder in Example 2;

[0100] Figure 11 The graph shows the oxidation reaction rate of MgLi5 powder in Example 2.

[0101] Where the left vertical axis represents mass change and the right vertical axis represents heat flow;

[0102] Figure 12 The image shows the surface morphology of the MgLi15 powder in Example 3 using SEM.

[0103] Figure 13 This is a partial SEM image of the surface morphology of the MgLi15 powder in Example 3.

[0104] Figure 14 Metallographic photograph of MgLi15 powder in Example 3;

[0105] Figure 15 The graph shows the oxidation reaction rate of MgLi15 powder in Example 3;

[0106] The left vertical axis represents mass change, and the right vertical axis represents heat flow. Detailed Implementation

[0107] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0108] All raw materials used in the examples are commercially available.

[0109] Example 1

[0110] Preparation of MgLi3 alloy powder:

[0111] Using system devices such as Figure 1 As shown;

[0112] 1. Preparation and melting of the target alloy

[0113] Take 10 kg of magnesium-lithium binary alloy raw material (MgLi15), and according to (1) and (2), 40 kg of magnesium should be added. Place 50 kg of raw material in melting furnace 2. First, evacuate to 0.1 kPa and purge with argon to 1 atm for stirring; second, evacuate to 10 kPa and purge with argon to 103 kPa for stirring. The oxygen content in the furnace is measured to be 0.01%. The superheat setting of the melt is 170 ± 10 °C, and the temperature is raised to 700 °C. The melting time is 1.5 h to obtain magnesium-lithium binary alloy liquid.

[0114] 2. Atomizer can pressure configuration

[0115] The first vacuum was evacuated to 0.1 kPa and then filled with argon to 1 atm; the second vacuum was evacuated to 10 kPa and then filled with argon to 105 kPa. The oxygen content in the furnace was measured to be 0.01%; the pressure difference between the tightly coupled gas atomizer and the silicon carbide crucible melting furnace was 1 kPa.

[0116] 3. Liquid conveying and atomization

[0117] Maintain the liquid mass flow rate at approximately 13.5 g / s. Select a 5 mm diameter annular slit-type atomizing nozzle and control the nozzle eccentricity angle at 5°. Turn on the atomizing gas and adjust the atomizing pressure to approximately 3.0 MPa using the pressure regulating valve. Continuously monitor the atomization status and the operation of each instrument during atomization to make timely adjustments. Ensure the high-pressure gas flow rate is 30 m / s. 3 / h or so.

[0118] 4. Discharge

[0119] Atomization is completed in approximately 60 minutes. After cooling for 3 hours, the collection bucket is removed, and the powder is poured into a sieve under an argon atmosphere. Powder particles larger than 200 mesh (80μm), 200–325 mesh (45μm), and 325–500 mesh (25μm) are removed. The remaining material smaller than 500 mesh is further processed by an air classifier. The particle size-classified powder is then stored in liquid alkanes.

[0120] 5. Implementation Results

[0121] Taking a powder with a median diameter of 25μm as an example, Figure 4 and Figure 5 The images show SEM images and magnified views of the surface morphology of the powder. They indicate that the sphericity of the lithium-magnesium alloy powder is greater than 0.95, and the surface is clean and smooth. Figure 6 Metallographic analysis, obtained using a Shanghai Changfang CMM-20 microscope, indicates that the microstructure is primarily dendritic, mainly composed of Li3Mg. 17 It is composed of α-Mg.

[0122] Figure 7The DSC / TG thermal oxidation curve of the powder in air atmosphere shows that the hot spot ignition temperature of the magnesium-lithium alloy ball is 486.2℃; calculated using the Kissinger method, it is 226.6 kJ / mol.

[0123] The calorific value released by the combustion of the powder in an oxygen environment of 3 MPa was tested using an oxygen bomb calorimeter. The density was tested using a JW-M100A series fully automatic true density tester, and the density of the alloy powder was measured to be 1.70 g / cm³. 3 The oxidation behavior of the powder in air at a heating rate of 10℃ / min was characterized using TG-DSC. The exothermic reaction and weight gain graph of the powder oxidation reaction showed that the oxidation reaction was rapid. The measured calorific value of the powder was 25.21 kJ / g, which, compared with the theoretical calorific value of 25.32 kJ / g in Table 1, represented an energy release rate of 99.56%.

[0124] Example 2

[0125] Preparation of MgLi5 alloy powder:

[0126] 1. Preparation and melting of the target alloy

[0127] Take 16.67 kg of magnesium-lithium binary alloy raw material (MgLi15), and according to (2), 33.34 kg of magnesium should be added. Place 50 kg of raw material in melting furnace 2. First, evacuate to 0.1 kPa and fill with argon to 1 atm for stirring; second, evacuate to 10 kPa and fill with argon to 104 kPa for stirring. The oxygen content in the furnace is 0.01%. The superheat setting of the melt is 130 ± 10 °C, and the temperature is raised to 680 °C. The melting time is 1 h to obtain magnesium-lithium binary alloy liquid.

[0128] 2. Atomizer can pressure configuration

[0129] The first vacuum was evacuated to 0.1 kPa and then filled with argon to 1 atm; the second vacuum was evacuated to 10 kPa and then filled with argon to 102 kPa. The oxygen content inside the furnace was measured to be 0.01%; the pressure difference between the tightly coupled gas atomizer and the silicon carbide crucible melting furnace was 1.5 kPa.

[0130] 3. Liquid conveying and atomization

[0131] Maintain the liquid mass flow rate at approximately 12.5 g / s. Select a 4 mm diameter annular slit-type atomizing nozzle and control the nozzle eccentricity angle at 4°. Turn on the atomizing gas and adjust the atomizing pressure to approximately 2.5 MPa using the pressure regulating valve. Continuously monitor the atomization status and the operation of each instrument during atomization to make timely adjustments. Ensure the high-pressure gas flow rate is 28 m / s. 3 / h or so.

[0132] 4. Discharge

[0133] Atomization is completed in approximately 40 minutes. After cooling for 3 hours, the collection bucket is removed, and the powder is poured into a sieve under an argon atmosphere. Powder particles larger than 200 mesh (80μm), 200–325 mesh (45μm), and 325–500 mesh (25μm) are removed. The remaining material smaller than 500 mesh is placed in an air classifier for further fine separation. The particle size-separated powder is then stored in liquid alkanes.

[0134] 5. Implementation Results

[0135] Taking a powder with a median diameter of 25μm as an example, Figure 8 and Figure 9 The images show SEM images and magnified views of the surface morphology of the powder. They indicate that the sphericity of the lithium-magnesium alloy powder is greater than 0.95, and the surface is clean and smooth. Figure 10 Metallographic analysis showed that the microstructure was mainly dendritic, primarily composed of Li. 0.92 Mg 4.08 It is composed of αMg.

[0136] Figure 11 The DSC / TG thermal oxidation curve of the powder in air atmosphere shows that the hot spot ignition temperature of the magnesium-lithium alloy ball is 475.1℃; the activation energy calculated using the Kissinger method is 136.3kJ / mol.

[0137] The calorific value released by the combustion of the powder in an oxygen environment of 3 MPa was tested using an oxygen bomb calorimeter. The density was tested using a JW-M100A series fully automatic true density tester, and the density of the alloy powder was measured to be 1.64 g / cm³. 3 The oxidation behavior of the powder in air at a heating rate of 10℃ / min was characterized using TG-DSC. The exothermic reaction and weight gain graph of the powder oxidation reaction showed that the oxidation reaction was rapid. The measured calorific value of the powder was 25.59 kJ / g, which, compared with the theoretical calorific value of 25.77 kJ / g in Table 1, represented an energy release rate of 99.30%.

[0138] Example 3

[0139] Prepare MgLi15 alloy powder.

[0140] 1. Preparation and melting of the target alloy

[0141] Take 50 kg of magnesium-lithium binary alloy raw material (MgLi15). Place the 50 kg raw material in melting furnace 2. First, evacuate to 0.1 kPa and purge with argon to 1 atm while stirring; second, evacuate to 10 kPa and purge with argon to 105 kPa while stirring. The oxygen content in the furnace is measured to be 0.01%. The superheat setting of the molten material is 100±10℃, heated to 650℃, and the melting time is 2 hours to obtain magnesium-lithium binary alloy liquid.

[0142] 2. Atomizer can pressure configuration

[0143] The first vacuum was evacuated to 0.1 kPa and then filled with argon to 1 atm; the second vacuum was evacuated to 10 kPa and then filled with argon to 102 kPa. The oxygen content in the furnace was measured to be 0.01%; the pressure difference between the tightly coupled gas atomizer and the silicon carbide crucible melting furnace was 2 kPa.

[0144] 3. Liquid conveying and atomization

[0145] Maintain the liquid mass flow rate at approximately 11.5 g / s. Select a 3 mm diameter annular slit-type atomizing nozzle and control the nozzle eccentricity angle at 3°. Turn on the atomizing gas and adjust the atomizing pressure to approximately 2.0 MPa using the pressure regulating valve. Continuously observe the atomization status and the operation of each instrument during atomization to make timely adjustments. Ensure the high-pressure gas flow rate is 25 m / s. 3 / h or so.

[0146] 4. Discharge

[0147] Atomization is completed in approximately 40 minutes. After cooling for 3 hours, the collection bucket is removed, and the powder is poured into a sieve under an argon atmosphere. Powder particles larger than 200 mesh (80μm), 200–325 mesh (45μm), and 325–500 mesh (25μm) are removed. The remaining material smaller than 500 mesh is placed in an air classifier for further fine separation. The particle size-separated powder is then stored in liquid alkanes.

[0148] 5. Implementation Results

[0149] Taking a powder with a median diameter of 25μm as an example, Figure 12 and Figure 13 The images show SEM images and magnified views of the surface morphology of the powder. They indicate that the sphericity of the lithium-magnesium alloy powder is greater than 0.95, and the surface is clean and smooth. Figure 14 Metallographic analysis showed that the microstructure was mainly dendritic, primarily composed of Li. 0.92 It consists of Mg4.08, β-Li and α-Mg.

[0150] Figure 15 The DSC / TG thermal oxidation curve of the powder in air atmosphere shows that the hot spot ignition temperature of the magnesium-lithium alloy ball is 428.5℃; the activation energy calculated using the Kissinger method is 60.1kJ / mol.

[0151] The calorific value released by the combustion of the powder in an oxygen environment of 3 MPa was tested using an oxygen bomb calorimeter. The density was tested using a JW-M100A series fully automatic true density tester, and the density of the alloy powder was measured to be 1.56 g / cm³. 3The oxidation behavior of the powder in air at a heating rate of 10℃ / min was characterized using TG-DSC. The exothermic reaction and weight gain graph of the powder oxidation reaction showed that the oxidation reaction was rapid. The measured calorific value of the powder was 27.49 kJ / g, which, compared with the theoretical calorific value of 27.56 kJ / g in Table 1, represented an energy release rate of 99.75%.

Claims

1. A magnesium-lithium binary alloy powder, characterized in that: The lithium mass content in the magnesium-lithium binary alloy powder is 3-20%; The density of the magnesium-lithium binary alloy powder is 1.50~1.70 g / cm³. 3 ; The calorific value is 25.21~29.49 kJ / g; The ignition temperature is 320.0~589.0℃; The activation energy is 33.0~226.6 kJ / mol; The sphericity of the magnesium-lithium binary alloy powder is not less than 95%; The preparation method of the magnesium-lithium binary alloy powder includes: (1) Under positive pressure of argon, the metal containing magnesium and lithium is melted in a silicon carbide / high-purity graphite anti-corrosion crucible melting furnace to obtain magnesium-lithium binary alloy liquid; (2) Under positive argon pressure, magnesium-lithium binary alloy liquid is transported to a tightly coupled gas atomizing tank through a stainless steel conveying pipe. After tight coupling gas atomization and sieving, the magnesium-lithium binary alloy powder is obtained. The tightly coupled gas atomizing tank has an annular slit-type gas atomizing nozzle with a diameter of 3mm to 8mm. The annular slit-type gas atomizing nozzle has a nozzle at its end with an eccentric angle of 3° to 7°. The liquid mass flow rate is 11g / s to 14g / s. The high-pressure gas flow rate of the tightly coupled gas atomizing tank is 25m. 3 / h~30m 3 / h; atomization pressure is 2.0MPa - 3.0MPa.

2. The magnesium-lithium binary alloy powder as described in claim 1, characterized in that: The lithium content in the magnesium-lithium binary alloy powder is 3-15% by mass; and / or, The density of the magnesium-lithium binary alloy powder is 1.56-1.70 g / cm 3 ; and / or, The calorific value is 25.21~27.49 kJ / g; and / or, The ignition temperature is 428.5~486.2℃; and / or, The activation energy is 60.1~226.6 kJ / mol.

3. A method of producing a magnesium-lithium binary alloy powder as claimed in claim 1 or 2, characterized in that The method includes: (1) Under positive pressure of argon, a metal containing magnesium and lithium is melted in a silicon carbide / high-purity graphite anti-corrosion crucible melting furnace to obtain a magnesium-lithium binary alloy liquid; the lithium content in the magnesium-lithium binary alloy liquid is 3~20% by mass; (2) Under positive argon pressure, the magnesium-lithium binary alloy liquid is transported to the tightly coupled gas atomizing tank through a stainless steel conveying pipe. After being atomized by the tightly coupled gas and sieved, the magnesium-lithium binary alloy powder is obtained. The mass flow rate of the liquid is 11 g / s to 14 g / s. The high-pressure gas flow rate of the tightly coupled gas atomizing tank is 25 m / s. 3 / h~30m 3 / h; atomization pressure is 2.0MPa - 3.0MPa.

4. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: The lithium mass content in the magnesium-lithium binary alloy solution is 3-15%.

5. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: Step (1), The oxygen volume content in the silicon carbide / high-purity graphite corrosion-resistant crucible melting furnace is kept to no more than 0.01% by vacuuming and purging with argon; and / or, During the melting process, the positive pressure of argon gas is in the range of 103 kPa to 105 kPa; and / or, The melting superheat is 90℃~180℃; and / or, The melting temperature is 650℃~750℃; and / or, The melting time is 1 to 2 hours.

6. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: Step (2), The oxygen volume content in the tightly coupled gas atomizer is kept no greater than 0.01% by evacuation and argon purging; and / or, The argon positive pressure of the tightly coupled gas atomizer and pipeline is 102 kPa to 105 kPa; and / or, The pressure difference between the tightly coupled gas atomizing canister and the silicon carbide crucible melting furnace is 1 kPa to 2 kPa.

7. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: Step (2), The stainless steel feed pipe has a niobium alloy lining.

8. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: The diameter of the circumferential slit atomizing nozzle is 3mm~5mm; and / or, The eccentricity angle of the nozzle is 3°~5°.

9. The method for preparing magnesium-lithium binary alloy powder as described in claim 3, characterized in that: Step (2), Under positive pressure of argon gas, powder of different particle sizes is obtained by mechanical screening and airflow separation.

Images