Aluminum-lithium alloy powder fuel and preparation method thereof

Abstract

The present invention belongs to the technical field related to metal fuels and discloses an aluminum-lithium alloy powder fuel and a preparation method thereof. The aluminum-lithium alloy powder fuel is prepared from raw materials, wherein the mass percentages of the raw materials are Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the remainder is Al. The addition of the Mg element in the present invention not only produces a "micro-explosion" effect but also precipitates stable, finely and evenly distributed intermetallic compounds, which can reduce the activity of Li in the alloy and improve the stability of the fuel. The addition of the RE element allows the precipitated intermetallic compound Al3RE to serve as a heterogeneous nucleation point for the metastable phase δ'(Al3Li), thereby forming an Al3(Li,RE) precipitated phase with a core-shell structure. Through targeted composition design, the microstructure of the precipitated phase in the alloy powder can be controlled, thereby improving the microstructure of the precipitated phase and enhancing the combustion performance of the fuel.

Description

Technical Field

[0001] The present invention belongs to the technical field related to metal fuels, and more specifically, relates to an aluminum-lithium alloy powder fuel and a preparation method thereof. Background Art

[0002] In recent years, researchers have discovered through a series of attempts that Al-Li alloy powders, produced by combining Li and Al elements at the atomic level through methods such as mechanical ball milling or droplet atomization, can effectively improve the problems of traditional micronized Al powders, such as ignition delay, incomplete combustion, and two-phase flow losses. The excellent combustion performance of Al-Li alloy powders is mainly attributed to the low boiling point (approximately 1350°C) and high saturated vapor pressure of Li element, which can form a violent "micro-explosion" effect with Al droplets, causing Al particles to decompose in situ into smaller particles, thereby reducing their residence time on the propellant surface and reducing agglomeration. In addition, Al-Li alloy powders are composed of a highly active Al-Li intermetallic compound phase and an α-Al(Li) solid solution. This two-phase structure makes the oxide layer formed on the powder surface less dense, promoting the exposure of the active Al inside. The final product of Li after combustion is gaseous LiCl, which can also significantly reduce two-phase flow losses.

[0003] Ignition and combustion studies of Al-Li alloy powders have shown that the distribution of Li in the powder, specifically the microstructure of the Li-containing precipitates, significantly affects the probability and intensity of micro-explosions, and thus combustion efficiency and two-phase flow losses. Currently, there are no reports on methods for controlling the microstructure of precipitates in Al-Li alloy powders for solid propellants. This means that current Al-Li alloy powder preparation technologies for solid propellants lack the necessary techniques to improve the microstructure of precipitates. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides an aluminum-lithium alloy powder fuel and a preparation method thereof, which are used to solve the problem that the current Al-Li alloy powder preparation technology used for solid propellants lacks technical means to improve the microstructure of the precipitated phase.

[0005] To achieve the above-mentioned purpose, according to one aspect of the present invention, there is provided an aluminum-lithium alloy powder fuel, characterized in that it is prepared from raw materials, the mass percentages of each raw material are Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the rest is Al.

[0006] According to the aluminum-lithium alloy powder fuel provided by the present invention, Al in each raw material is used as a matrix, and Li, Mg and RE exist in the aluminum-lithium alloy powder fuel in the form of intermetallic compounds S1 (Al2MgLi) and Al3 (Li, RE) phases.

[0007] According to the aluminum-lithium alloy powder fuel provided by the present invention, the mass percentages of the raw materials are Li: 3%, Mg: 0.5%, RE: 1%, and the rest is Al.

[0008] According to the aluminum-lithium alloy powder fuel provided by the present invention, RE is Y and / or Sc.

[0009] According to the aluminum-lithium alloy powder fuel provided by the present invention, the aluminum-lithium alloy powder fuel is regular spherical particles, and the average particle size of the spherical particles is 10-50 μm.

[0010] According to another aspect of the present invention, a method for preparing an aluminum-lithium alloy powder fuel is provided, for preparing any of the aluminum-lithium alloy powder fuels described above, the method comprising:

[0011] S1, preparing the raw material into a cast powder by gas atomization or centrifugal atomization powder making method;

[0012] S2, heating the as-cast powder from room temperature to a first preset temperature under a protective atmosphere, and keeping the temperature for a first preset time;

[0013] S3, cooling the powder obtained in S2 to a second preset temperature under a protective atmosphere, and keeping the temperature for a second preset time;

[0014] S4, cooling the powder obtained in S3 to room temperature under a protective atmosphere to obtain an aluminum-lithium alloy powder fuel.

[0015] According to the method for preparing the aluminum-lithium alloy powder fuel provided by the present invention, S1 specifically includes:

[0016] The raw materials are melted by vacuum arc melting at a temperature of 100 to 150° C. above the corresponding melting point for 10 to 30 minutes to prepare an alloy base material, and the alloy base material is prepared into granules;

[0017] The alloy base material prepared into granular form is melted at a temperature 50-100° C. above its melting point for 5-10 minutes by gas atomization or centrifugal atomization powder making method, and then atomized and condensed to prepare the cast powder in the form of spherical particles.

[0018] According to the preparation method of the aluminum-lithium alloy powder fuel provided by the present invention, S2 specifically comprises: heating the cast powder from room temperature to 500-600°C at an average heating rate of 10-300°C / min under a protective atmosphere, and keeping the temperature for 0.1-24h;

[0019] S3 specifically includes: cooling the powder obtained in S2 to 25-450° C. at an average cooling rate of 10-300° C. / min under a protective atmosphere, and keeping the temperature for 0.1-24 hours.

[0020] According to the method for preparing the aluminum-lithium alloy powder fuel provided by the present invention, S4 specifically comprises: cooling the powder obtained in S3 to room temperature at a cooling rate of 5 to 300° C. / min under a protective atmosphere;

[0021] The protective atmosphere in S2, S3 and S4 is at least one of argon, CO2 and nitrogen.

[0022] According to the method for preparing the aluminum-lithium alloy powder fuel provided by the present invention, S3 specifically includes:

[0023] The powder obtained in S2 is cooled to 200-450°C at an average cooling rate of 10-300°C / min under a protective atmosphere and kept at this temperature for 0.1-0.5h.

[0024] In general, compared with the prior art, the above technical solutions conceived by the present invention provide aluminum-lithium alloy powder fuel and its preparation method:

[0025] 1. Adding Li to aluminum alloys can produce a "micro-explosion" effect, improving alloy combustion efficiency and reducing two-phase flow losses. Adding Mg, in addition to the "micro-explosion" effect, can also precipitate stable, finely distributed intermetallic compounds, which can reduce the activity of Li in the alloy and improve fuel stability. Adding RE can use the precipitated intermetallic compound Al3RE as a heterogeneous nucleation point for the metastable phase δ'(Al3Li), thereby forming a core-shell structured Al3(Li,RE) precipitation phase. Through targeted composition design, the microstructure of the precipitation phase in the alloy powder can be controlled, thereby improving the microstructure of the precipitation phase and enhancing fuel combustion performance.

[0026] 2. The preparation method provided is to prepare the Al-Li-Mg-RE aluminum alloy cast powder by atomization, followed by solution treatment and aging treatment. The purpose of the solution treatment is to allow some low-melting-point eutectic phases in the alloy to dissolve into the matrix at high temperature during the transition from low temperature to high temperature, thereby promoting the dispersion and precipitation of the Al3(Li, RE) phase during the subsequent aging process. The purpose of the aging treatment is to cause the Al3(Li, RE) phase to disperse and precipitate from the matrix. This preparation method can obtain a microstructure in which the Al3(Li, RE) phase is dispersed in the α-Al matrix.

[0027] 3. The aluminum-lithium alloy powder fuel provided is prepared through targeted composition design and heat treatment (including solution treatment and aging treatment) methods. The powder has fine grains, uniform composition, and fine and uniform distribution of intermetallic compounds. It is of great significance to improve the current micron Al-Li alloy powder "micro-explosion" effect, combustion efficiency, and reduce propellant two-phase flow loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 This is a TOF-SIMS photograph of the Li element distribution of the alloy before heat treatment in Example 1 of the present invention;

[0029] Figure 2 This is a TOF-SIMS photograph of the Li element distribution of the alloy after heat treatment in Example 1 of the present invention;

[0030] Figure 3 This is a TEM photograph of the Al3(Li, Y) precipitated phase after heat treatment of the alloy in Example 1 of the present invention;

[0031] Figure 4 This is a TOF-SIMS photograph of the Li element distribution of the alloy before heat treatment in Example 2 of the present invention;

[0032] Figure 5 This is a TOF-SIMS photograph of the Li element distribution of the alloy after heat treatment in Example 2 of the present invention;

[0033] Figure 6 TEM photos of Al3(Li, Sc) and Al2MgLi precipitation phases after heat treatment of the alloy in Example 2 of the present invention. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely for the purpose of explaining the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0035] refer to Figure 1 and Figure 2 In a first embodiment of the present invention, an aluminum-lithium alloy powder fuel is provided. The aluminum-lithium alloy powder fuel is prepared from raw materials, wherein the mass percentages of the raw materials are Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the remainder is Al and some non-removable impurity elements. Impurity elements are some elements that cannot be removed from the raw materials. That is, the substances in the aluminum-lithium alloy powder fuel mainly include aluminum Al, lithium Li, magnesium Mg, and rare earth elements RE, and the mass proportions of each substance are as shown above. The raw materials are prepared with the above substances in proportion, and the aluminum-lithium alloy powder fuel provided in this embodiment, namely, Al-Li-Mg-RE aluminum alloy powder, is prepared according to the relevant preparation method of aluminum-lithium alloy powder.

[0036] Specifically, Al in each raw material is used as a matrix, and Li, Mg and RE exist in the aluminum-lithium alloy powder fuel in the form of intermetallic compound S1 (Al2MgLi) and Al3 (Li, RE) phases with Al.

[0037] The aluminum-lithium alloy powder fuel provided in this embodiment, through targeted component design, can improve the microstructure of the Al3(Li, RE) phase precipitation in the Al-Li-Mg-RE aluminum alloy powder used in solid propellants. Specifically, the addition of the Li element to the aluminum alloy is primarily due to the "micro-explosion" effect. Compared with pure Al, the combustion efficiency of the Al-Li alloy is significantly improved. At the same time, the particle size of the Al-Li alloy combustion product is smaller, thereby significantly reducing two-phase flow losses and improving energy performance. In addition, when the oxidant is AP, the metallic Li is ultimately converted into gaseous LiCl after combustion. This can reduce the generation of HCl in the combustion products of AP-containing solid propellants by 95%, making it clean and environmentally friendly.

[0038] In addition to the "micro-explosion" effect, the addition of Mg element can also precipitate stable and finely evenly distributed S1 (Al2MgLi) intermetallic compounds, which can reduce the activity of Li in the alloy and improve the stability of the fuel.

[0039] The addition of RE element is mainly due to the fact that the dispersed Al3RE can serve as the heterogeneous nucleus of the metastable phase δ'(Al3Li), forming a core-shell structure of dispersed Al3(Li,RE). In addition, it can refine the grain size of the alloy powder and obtain a non-dendritic structure.

[0040] Preferably, the mass percentages of the raw materials are Li: 3%, Mg: 0.5%, RE: 1%, and the rest are Al and some non-removable impurity elements.

[0041] Optionally, RE is Y and / or Sc.

[0042] Specifically, the aluminum-lithium alloy powder fuel is in the form of regular spherical particles, and the average particle size of the spherical particles is 10-50 μm.

[0043] The second embodiment provides a method for preparing an aluminum-lithium alloy powder fuel, which is used to prepare any of the aluminum-lithium alloy powder fuels described above. The method comprises:

[0044] S1, preparing the raw materials into cast powder by gas atomization or centrifugal atomization powder making method to obtain Al-Li-Mg-RE aluminum alloy cast powder; this embodiment further proposes that the preparation method also includes:

[0045] S2, heating the as-cast powder from room temperature to a first preset temperature under a protective atmosphere, and keeping the temperature for a first preset time;

[0046] S3, cooling the powder obtained in S2 to a second preset temperature under a protective atmosphere, and keeping the temperature for a second preset time;

[0047] S4, cooling the powder obtained in S3 to room temperature under a protective atmosphere to obtain an aluminum-lithium alloy powder fuel.

[0048] This embodiment provides a method for improving the precipitation of Al3(Li, RE) phase in Al-Li-Mg-RE aluminum alloy powder used for solid propellant. On the basis of atomization powder production (i.e., S1), heat treatment methods (i.e., S2, S3, and S4) are further proposed. This breaks the microstructure of Al3(Li, RE) phase precipitated in the form of laths or continuous networks at the grain boundaries in the Al-Li-Mg-RE aluminum alloy cast powder obtained by gas atomization or centrifugal atomization powder production, and can obtain a microstructure in which the Al3(Li, RE) phase is dispersed in the α-Al matrix.

[0049] After the Al-Li-Mg-RE aluminum alloy cast powder is prepared by gas atomization, it is immediately subjected to solution treatment and aging treatment. The purpose of the solution treatment is to allow some low-melting-point eutectic phases in the alloy to dissolve into the matrix at low temperature when transitioning from low temperature to high temperature, thereby promoting the dispersion and precipitation of Al3(Li, RE) phase in the subsequent aging process; the purpose of the aging treatment is to allow the Al3(Li, RE) phase to disperse and precipitate from the matrix.

[0050] S1 specifically includes:

[0051] The raw materials are melted by vacuum arc melting at a temperature 100-150°C above the corresponding melting point for 10-30 minutes to prepare an alloy base material, and the alloy base material is prepared into particles. The raw materials can be melted separately by vacuum arc melting and then mixed together to prepare the alloy base material, and the raw materials are melted at a temperature 100-150°C higher than the corresponding melting point and kept warm for 10-30 minutes.

[0052] The granular alloy parent material is heated to a temperature 50-100°C above its melting point for 5-10 minutes using gas atomization or centrifugal atomization to melt the granular alloy parent material. The granular alloy parent material is then heated to a temperature 50-100°C above its melting point for 5-10 minutes to melt the granules. The molten alloy parent material is then atomized. In the gas atomization method, a moving atomizing gas impacts the molten alloy parent material to form atomized droplets, which are then condensed to form a solid powder to maintain sphericity.

[0053] S2 specifically comprises: heating the cast powder from room temperature to 500-600° C. at an average heating rate of 10-300° C. / min under a protective atmosphere, and keeping the temperature for 0.1-24 hours;

[0054] S3 specifically includes: cooling the powder obtained in S2 to 25-450° C. at an average cooling rate of 10-300° C. / min under a protective atmosphere, and keeping the temperature for 0.1-24 hours.

[0055] S4 specifically comprises: cooling the powder obtained in S3 to room temperature at a cooling rate of 5 to 300°C / min under a protective atmosphere;

[0056] The protective atmosphere in S2, S3 and S4 is at least one of argon, CO2 and nitrogen.

[0057] Preferably, S3 specifically includes:

[0058] The powder obtained in S2 is cooled to 200-450°C at an average cooling rate of 10-300°C / min under a protective atmosphere and kept at this temperature for 0.1-0.5h.

[0059] S2, S3 and S4 can be carried out in a tube furnace or other enclosed space with protective atmosphere, and the heating rate and cooling rate can be controlled by adjusting the heating power of the tube furnace and / or the purge flow rate of the protective atmosphere.

[0060] This embodiment provides a method for improving the precipitation of Al3(Li, RE) phase in Al-Li-Mg-RE aluminum alloy powder used for solid propellant. The method aims to control the dispersed nucleation and growth behavior of the precipitated phase in the matrix by adjusting the alloy composition and adjusting the heat treatment heating rate, holding temperature, holding time, and cooling rate, so as to obtain the optimal diameter size, number density, and uniform distribution state of the dispersed phase, thereby enhancing the "micro-explosion" effect, improving the combustion efficiency of micronized Al powder, and reducing two-phase flow losses.

[0061] Example 1

[0062] The weight percentage of Al-Li-Mg-Y aluminum alloy powder is Li: 3%, Mg: 0.5%, Y: 1%, and the rest is Al and unremovable impurity elements. The Al-Li-Mg-Y aluminum alloy cast powder is obtained by gas atomization pulverization method. The temperature is raised from room temperature to 550°C at a rate of 10°C / min and kept at this temperature for 2 hours. Then, the powder is cooled to 450°C at a rate of 100°C / min using high-purity helium and kept at this temperature for 2 hours. After the temperature is kept at this temperature, it is quickly cooled to room temperature with helium, so that the Li element in the aluminum-lithium alloy powder is improved from grain boundary segregation before heat treatment to dispersed distribution after treatment. Figure 1 and Figure 2 shown.

[0063] Figure 3 TEM photo of Al3(Li,Y) precipitated phase after heat treatment of the alloy in Example 1 of the present invention. It can be seen that there is no precipitated phase at the grain boundary, and there is a core-shell Al3(Li,Y) phase dispersed in the crystal. Figure 1 By comparison, it can be seen that after heat treatment, the Li element segregated at the grain boundary is redissolved into the crystal and dispersed and precipitated in the crystal.

[0064] Example 2

[0065] The weight percentage of Al-Li-Mg-Sc aluminum alloy powder is Li: 5%, Mg: 1%, Sc: 0.3%, and the rest is Al and unremovable impurity elements. The Al-Li-Mg-RE aluminum alloy powder is obtained by gas atomization powder preparation method. The temperature is raised from room temperature to 500°C at a rate of 100°C / min and kept at this temperature for 0.5h. Then, the powder is cooled to 200°C at a cooling rate of 100°C / min using high-purity helium and kept at this temperature for 2h. After the temperature is kept at this temperature, it is quickly cooled to room temperature with helium, so that the Li element in the aluminum-lithium alloy powder is improved from grain boundary segregation before heat treatment to dispersed distribution after treatment. Figure 4 and Figure 5 shown.

[0066] Figure 6 TEM photos of Al3(Li, Sc) precipitates and Al2MgLi precipitates after heat treatment of the alloy in Example 2 of the present invention show that there is no continuous network precipitate at the grain boundary, and there are dispersed core-shell Al3(Li, Sc) phases and large Al2MgLi phases in the crystal. Figure 4 By comparison, it can be seen that after heat treatment, the Li element segregated at the grain boundary is redissolved into the crystal and dispersed and precipitated in the crystal.

[0067] This embodiment provides a controllable preparation technology for micro-homogeneous Al-Li alloy powder with dispersed distribution of precipitate phase. The aluminum alloy powder prepared by this method has uniform matrix composition and dispersed distribution of Al3(Li, RE) phase, which can effectively improve the "micro-explosion" effect, the combustion efficiency of micron Al powder and reduce the two-phase flow loss, which is conducive to meeting the urgent needs of the aviation and aerospace fields.

[0068] It will be easily understood by those skilled in the art that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing aluminum-lithium alloy powder fuel, characterized in that: The aluminum-lithium alloy powder fuel is prepared from raw materials, wherein the mass percentages of the raw materials are Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the rest is Al; the preparation method comprises: S1, preparing the raw material into a cast powder by gas atomization or centrifugal atomization powder making method; S2, heating the as-cast powder from room temperature to a first preset temperature under a protective atmosphere, and keeping the temperature for a first preset time; S3, cooling the powder obtained in S2 to a second preset temperature under a protective atmosphere, and keeping the temperature for a second preset time; S4, cooling the powder obtained in S3 to room temperature under a protective atmosphere to obtain an aluminum-lithium alloy powder fuel; S2 specifically comprises: heating the cast powder from room temperature to 500-600° C. at an average heating rate of 10-300° C. / min under a protective atmosphere, and keeping the temperature for 0.1-24 hours; S3 specifically includes: cooling the powder obtained in S2 to 25-450° C. at an average cooling rate of 10-300° C. / min under a protective atmosphere, and keeping the temperature for 0.1-24 hours.

2. The method for preparing the aluminum-lithium alloy powder fuel according to claim 1, wherein: S1 specifically includes: The raw materials are melted by vacuum arc melting at a temperature of 100-150°C above the corresponding melting point for 10-30 minutes to prepare an alloy base material, and the alloy base material is prepared into granules; The alloy base material prepared into granular form is melted at a temperature 50-100° C. above its melting point for 5-10 minutes by gas atomization or centrifugal atomization powder making, and then atomized and condensed to prepare the cast powder in the form of spherical particles.

3. The method for preparing the aluminum-lithium alloy powder fuel according to claim 1, wherein: S4 specifically comprises: cooling the powder obtained in S3 to room temperature at a cooling rate of 5 to 300°C / min under a protective atmosphere; The protective atmosphere in S2, S3 and S4 is at least one of argon, CO2 and nitrogen.

4. The method for preparing the aluminum-lithium alloy powder fuel according to claim 1, wherein: S3 specifically includes: The powder obtained in S2 is cooled to 200-450°C at an average cooling rate of 10-300°C / min under a protective atmosphere and kept at this temperature for 0.1-0.5h.

5. An aluminum-lithium alloy powder fuel, characterized in that: The raw materials are prepared by the preparation method according to any one of claims 1 to 4, wherein the mass percentages of the raw materials are Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the rest is Al.

6. The aluminum-lithium alloy powder fuel according to claim 5, characterized in that: Among the raw materials, Al is used as a matrix, and Li, Mg and RE exist in the aluminum-lithium alloy powder fuel in the form of intermetallic compound S1 (Al2MgLi) and Al3 (Li, RE) phases with Al.

7. The aluminum-lithium alloy powder fuel according to claim 5, characterized in that: The mass percentages of the raw materials are Li: 3%, Mg: 0.5%, RE: 1%, and the rest is Al.

8. The aluminum-lithium alloy powder fuel according to claim 5, characterized in that: RE is Y and / or Sc.

9. The aluminum-lithium alloy powder fuel according to claim 5, characterized in that: The aluminum-lithium alloy powder fuel is in the form of regular spherical particles, and the average particle size of the spherical particles is 10-50 μm.

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