Aluminum-lithium alloy powder fuel and preparation method thereof

Abstract

The invention belongs to the related technical field of metal fuels, and discloses an aluminum-lithium alloy powder fuel and a preparation method thereof, the aluminum-lithium alloy powder fuel is prepared from the following raw materials in percentage by mass: 2-10% of Li, 0.1-5% of Mg, 0.1-3% of RE and the balance of Al. The added Mg element can separate out stable, fine and uniformly-distributed intermetallic compounds besides a micro-explosion effect, the activity of Li in the alloy can be reduced, the stability of the fuel can be improved, the added RE element can form an Al3 (Li, RE) precipitated phase with a core-shell structure by taking the precipitated intermetallic compound Al3RE as a heterogeneous nucleation particle of a metastable phase delta '(Al3Li), and the stability of the fuel can be improved. Through targeted component design, the structure regulation and control of the precipitated phase in the alloy powder can be realized, so that the microstructure of the precipitated phase is improved, and the combustion performance of the fuel is improved.

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 found through a series of attempts that Al-Li alloy powders made by combining Li and Al elements at the atomic level through mechanical ball milling or droplet atomization can effectively improve the problems of ignition delay, incomplete combustion and two-phase flow loss of traditional micron Al powder. The excellent combustion performance of Al-Li alloy powder is mainly attributed to the low boiling point (about 1350℃) and high saturated vapor pressure of Li element, which can form a violent "micro-explosion" effect with Al droplets, so that Al particles are decomposed into smaller particles in situ, thereby reducing their residence time on the propellant surface and reducing agglomeration. In addition, Al-Li alloy powders are composed of highly active Al-Li intermetallic compound phases and α-Al(Li) solid solutions. This two-phase structure makes the oxide layer formed on the surface of the powder no longer dense, which promotes the exposure of the internal active Al; the final product of Li after combustion is gaseous LiCl, which can also greatly reduce the two-phase flow loss.

[0003] Ignition and combustion studies of Al-Li alloy powders show that the distribution of Li in the powder, that is, the microstructure of the Li-containing precipitate phase, significantly affects the probability and intensity of "micro-explosion" in the alloy, and thus affects the combustion efficiency and two-phase flow loss. At present, there are no reports on the organization control method of the precipitate phase in Al-Li alloy powders for solid propellants, that is, the current Al-Li alloy powder preparation technology for solid propellants lacks relevant technical means to improve the microstructure of the precipitate phase. Summary of the invention

[0004] In view of the above 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 relevant technical means for improving the microstructure of the precipitated phase.

[0005] To achieve the above objectives, 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 with Al.

[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 a regular spherical particle, and the average particle size of the spherical particle 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, which is used to prepare the aluminum-lithium alloy powder fuel described in any one of the above items, and the preparation method comprises:

[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 comprises:

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

[0017] The alloy matrix material prepared into granular form is melted at a temperature 50 to 100° C. above its melting point for 5 to 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.

[0018] According to the preparation method of 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 0.1-24 hours;

[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 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 comprises:

[0023] The powder obtained from 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 aluminum-lithium alloy powder fuel and the preparation method thereof provided by the present invention are as follows:

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

[0026] 2. The preparation method provided is to obtain Al-Li-Mg-RE aluminum alloy cast powder by atomization, and then perform solid solution treatment and aging treatment. The purpose of the solid solution treatment is to make some low melting point eutectic phases in the alloy dissolve into the matrix at high 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 make the Al3 (Li, RE) phase disperse and precipitate from the matrix. The 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 "micro-explosion" effect of micron Al-Li alloy powder, combustion efficiency, and reduce propellant two-phase flow losses. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0029] Figure 2 This is a TOF-SIMS photo 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) precipitation phase after heat treatment of the alloy in Example 1 of the present invention;

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

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

[0033] Figure 6 TEM photograph 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 purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain 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 can be combined with each other as long as they do not conflict with each other.

[0035] refer to Figure 1 and Figure 2 , Embodiment 1 of the present invention provides an aluminum-lithium alloy powder fuel, which is prepared from raw materials, and the mass percentage of each raw material is Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the rest is Al and some impurity elements that cannot be removed. Impurity elements are some elements that cannot be removed in each raw material. 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 proportion of each substance is as above. The above-mentioned substances are matched with raw materials in proportion, and the aluminum-lithium alloy powder fuel provided in this embodiment, that is, 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 can improve the microstructure of Al3 (Li, RE) phase precipitation in Al-Li-Mg-RE aluminum alloy powder used for solid propellant through targeted component design. Specifically, the addition of Li element in the aluminum alloy is first due to the "micro-explosion" effect. Compared with pure Al, the combustion efficiency of Al-Li alloy is significantly improved. At the same time, the particle size of the Al-Li alloy combustion product is smaller, thereby greatly reducing the two-phase flow loss and improving the energy performance. In addition, when the oxidant is AP, the metal Li is finally converted into gaseous LiCl after combustion, so the generation of HCl in the combustion product of AP-containing solid propellant can be reduced by 95%, which is 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 nucleation point of the metastable phase δ'(Al3Li) to form a core-shell structured 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 impurity elements that cannot be removed.

[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 the aluminum-lithium alloy powder fuel described in any one of the above items, and the preparation method comprises:

[0044] S1, preparing the raw material 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] The present 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 making (i.e., S1), a heat treatment method (i.e., S2, S3 and S4) is further proposed, which breaks the microstructure of Al3(Li, RE) phase precipitated in the grain boundary lath or continuous network in the Al-Li-Mg-RE aluminum alloy cast powder obtained by gas atomization or centrifugal atomization powder making method, and can obtain a microstructure in which Al3(Li, RE) phase is dispersed in the α-Al matrix.

[0049] After the Al-Li-Mg-RE aluminum alloy cast powder is obtained 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 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 particles. The raw materials can be melted separately by vacuum arc melting and then mixed together to prepare the alloy base material. When melting each raw material, a temperature of 100 to 150°C higher than the corresponding melting point is used and kept warm for 10 to 30 minutes.

[0052] The alloy parent material prepared into particles is heated to a temperature of 50 to 100°C above the melting point of the alloy parent material for 5 to 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. That is, the alloy parent material prepared into particles is heated to a temperature of 50 to 100°C above the melting point of the alloy parent material and heated for 5 to 10 minutes to melt, and then the melted alloy parent material is atomized. In the gas atomization powder making method, the moving atomizing gas is used to impact the molten alloy parent material to form atomized droplets, and the atomized droplets are condensed to form solid powder to maintain the 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 from 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 tubular 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 tubular furnace and / or the purge flow rate of the protective atmosphere.

[0060] The present 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, which 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 micron Al powder and reducing the two-phase flow loss.

[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 impurity elements that cannot be removed. The Al-Li-Mg-Y aluminum alloy cast powder obtained by gas atomization powder making method is heated from room temperature to 550°C at a heating rate of 10°C / min, and kept at this temperature for 2 hours. Then, the powder is cooled to 450°C at a cooling 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 the grain boundary segregation before the heat treatment to the dispersed distribution after the treatment. Figure 1 and Figure 2 shown.

[0063] Figure 3 TEM photo of the 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 dispersed core-shell Al3(Li,Y) phase in the crystal. Figure 1 By comparison, it can be seen that after heat treatment, the Li element segregated at the grain boundary redissolves into the crystal and disperses and precipitates 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 impurity elements that cannot be removed. The Al-Li-Mg-RE aluminum alloy powder obtained by gas atomization powder making method is heated from room temperature to 500°C at a heating rate of 100°C / min, and kept warm for 0.5h, and then the powder is cooled to 200°C at a cooling rate of 100°C / min using high-purity helium and kept warm for 2h. After keeping warm, 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, such as Figure 4 and Figure 5 shown.

[0066] Figure 6 TEM photos of Al3(Li, Sc) 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 redissolves into the crystal and disperses and precipitates in the crystal.

[0067] The present embodiment provides a controllable preparation technology of 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 and combustion efficiency of micron Al powder and reduce two-phase flow losses, which is beneficial to meet the urgent needs of aviation and aerospace fields.

[0068] It will be easily understood by those skilled in the art that the above description is only 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 protection scope of the present invention.

Claims

1. An aluminum-lithium alloy powder fuel, characterized in that: The raw materials are prepared by weight percentage of Li: 2-10%, Mg: 0.1-5%, RE: 0.1-3%, and the rest is Al.

2. The aluminum-lithium alloy powder fuel according to claim 1, 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 compounds S1 (Al2MgLi) and Al3 (Li, RE) with Al.

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

4. The aluminum-lithium alloy powder fuel according to claim 1, characterized in that: RE is Y and / or Sc.

5. The aluminum-lithium alloy powder fuel according to claim 1, 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.

6. A method for preparing aluminum-lithium alloy powder fuel, characterized in that: Used to prepare the aluminum-lithium alloy powder fuel according to any one of claims 1 to 5, the preparation method comprising: 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.

7. The method for preparing the aluminum-lithium alloy powder fuel according to claim 6, characterized in that: S1 specifically includes: The raw materials are melted at a temperature of 100 to 150° C. above the corresponding melting point for 10 to 30 minutes by vacuum arc melting to prepare an alloy base material, and the alloy base material is prepared into particles; The alloy matrix material prepared into granular form is melted at a temperature 50 to 100° C. above its melting point for 5 to 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.

8. The method for preparing the aluminum-lithium alloy powder fuel according to claim 6, characterized in that: 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.

9. The method for preparing the aluminum-lithium alloy powder fuel according to claim 6, characterized in that: 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.

10. The method for preparing the aluminum-lithium alloy powder fuel according to claim 8, characterized in that: S3 specifically includes: The powder obtained from 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.

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