Vanadium-aluminum intermediate alloy for aerospace titanium alloy and preparation method of vanadium-aluminum intermediate alloy

Abstract

The invention relates to the technical field of preparation of intermediate alloys for aerospace-grade titanium alloys, and discloses a vanadium-aluminum intermediate alloy for an aerospace-grade titanium alloy and a preparation method of the vanadium-aluminum intermediate alloy. According to preparation of the alloy, high-purity aluminum particles, vanadium pentoxide, calcium oxide, cryolite and aluminum foil serve as raw materials, a primary alloy is prepared through a vacuum aluminothermy method based on an aluminum foil bag-shaped powder bag type material, then the primary alloy is subjected to finishing treatment to obtain alloy particles, then the alloy particles are sequentially subjected to alkali washing, filtering, vacuum heat treatment and other links, and the aluminum foil bag type aluminum alloy is obtained. And finally, the AlV65 alloy which is higher in purity, better in component uniformity and purer in microstructure is prepared. The method can emphatically solve the problems that the existing vanadium-aluminum alloy is high in gas phase impurity content, heavy in component segregation and more in microscopic inclusion, and is of great significance to construction of a more tough aerospace industry chain and promotion of high-quality development of the industry.

Description

Technical Field

[0001] The present invention relates to the technical field of preparing intermediate alloys for aerospace-grade titanium alloys, and more particularly to a method for preparing a vanadium-aluminum alloy with higher purity, better component uniformity and purer microstructure. Background Art

[0002] Currently, driven by the rapid evolution of aerospace technology and surging demand, the titanium alloy industry chain is experiencing unprecedented development opportunities. Master alloys and titanium sponge, as the primary raw materials for smelting and preparing titanium alloys, hold strategic importance within the industry chain.

[0003] Vanadium-aluminum master alloys are key raw materials for the preparation of aerospace titanium alloys such as Ti-6Al-4V and Ti-8Al-1Mo-1V. Their quality significantly impacts the final quality of titanium alloys. Significantly improving the purity, compositional uniformity, and microstructural purity of these alloys will have a positive impact on improving the ductility, corrosion resistance, formability, and mechanical properties of titanium alloys.

[0004] The main production processes for vanadium-aluminum master alloys include a one-step process (thermite) and a two-step process (thermite + induction melting). The one-step process involves a direct thermite reaction in an atmospheric atmosphere, resulting in lower alloy purity, greater component segregation, and a high concentration of microscopic impurities. Patent CN110592453B discloses a one-step process for preparing vanadium-aluminum alloys. However, this process only aims to achieve an oxygen content below 0.04 wt%, without addressing the nitrogen content as an impurity, nor does it address the uniformity of composition across different regions of the alloy ingot or the purity of the microstructure. The two-step process requires a longer process flow, requires more expensive induction melting equipment, increases production costs, and results in lower single-furnace output. The improvement in alloy purity and microstructural purity is not significant. Patent CN103849787A discloses a two-step process for preparing vanadium-aluminum alloys. After the thermite process, the aluminum content required for induction melting must be precisely calculated, resulting in complex batching. Furthermore, the impurity levels of oxygen and nitrogen must both be at least 0.02 wt%, and microstructural purity is also not addressed. These methods are difficult to meet the current demand for high-quality vanadium-aluminum alloys in aerospace-grade titanium alloys.

[0005] In recent years, the vacuum aluminothermic process has garnered significant industry attention. However, this method relies solely on heat release to maintain separation between the alloy and slag, failing to control the steady release of heat, making alloy quality difficult to guarantee. Patent CN117604354A discloses the use of a vacuum reactor to prepare vanadium-aluminum alloys. However, the mixed materials must be dry-mixed, and the bottom of the crucible must be covered with vanadium-aluminum return slag. Impurities such as oxygen and nitrogen are not below 0.01 wt%, and no attention is paid to the compositional uniformity and microstructural purity of different regions of the alloy ingot.

[0006] In summary, vanadium-aluminum master alloy products produced using current processes suffer from problems such as high impurity content, severe composition segregation, and numerous microscopic inclusions, which have limited the high-quality development of the titanium alloy industry. Furthermore, it is worth noting that published patents often target vanadium-aluminum alloys such as AlV55 and AlV85, but lack relevant reports on AlV65 (V content of 62-68 wt%) alloys, which are more universal internationally.

[0007] Therefore, how to provide a preparation method of vanadium-aluminum alloy to solve the above problems, and at the same time prepare it with AlV65 alloy as the object, has become a difficult problem that urgently needs to be solved in the current titanium alloy industry chain, and it is also the key to the future development of aerospace technology. Summary of the Invention

[0008] In light of this, the present invention provides a vanadium-aluminum master alloy for aerospace-grade titanium alloys and its preparation method, focusing on addressing the challenges of existing alloys, such as high oxygen and nitrogen vapor-phase impurity content, severe chemical composition segregation, and numerous microscopic inclusions. Furthermore, the present invention utilizes AlV65 alloy as the research target.

[0009] One of the purposes of the present invention is to provide a method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy, comprising the following steps:

[0010] (1) High-purity aluminum particles, vanadium pentoxide, calcium oxide, and cryolite are uniformly mixed, and the mixed raw materials are wrapped using a powder packaging machine equipped with an aluminum foil packaging device to prepare a plurality of "aluminum foil capsule powder bags";

[0011] (2) Placing the "aluminum foil capsule powder bag" in a layered layout with each layer tightly stacked in a vacuum aluminothermic furnace, placing an aluminum foil wrapped with an ignition agent at the center of the top of the material, and then performing a vacuum aluminothermic reaction to produce a primary vanadium aluminum alloy;

[0012] (3) performing a finishing treatment on the primary vanadium-aluminum alloy to obtain alloy particles;

[0013] (4) The alloy particles are subjected to alkaline washing, filtration, vacuum drying and other steps in sequence to obtain AlV65 alloy.

[0014] Furthermore, in step (1), the purity of the high-purity aluminum particles and vanadium pentoxide are both ≥99.8%, and the particle size is 80-120 mesh; the purity of the calcium oxide and cryolite are both ≥99.5%, and the particle size is 290-310 mesh. The purpose is to ensure the high purity of the raw materials, to minimize the introduction of excessive impurities into the reaction system, and to ensure that the particle size of the raw materials meets the optimal range, to promote the full progress of the reaction, and to improve the uniformity of the smelting.

[0015] Preferably, the raw materials are mixed uniformly, that is, a V-shaped mixer is used to mix the raw materials at a speed of 30 to 50 rpm for 20 to 40 minutes. This is to ensure that the raw materials are mixed uniformly, which is conducive to the subsequent aluminothermic reduction reaction, thereby further improving the uniformity of the chemical composition of the alloy ingot.

[0016] Furthermore, in step (1), considering that aluminum foil is used to wrap the powder and also serves as a raw material for the thermite reaction, the weight of the aluminum foil must be designed into the raw material ratio. The mass ratio of the high-purity aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is (490-510): (890-910): (70-90): (6-8): (180-200). The purpose is to prepare an AlV65 alloy with a V content of 62-68 wt%.

[0017] Furthermore, in step (1), the mixed raw materials are packaged using a powder packaging machine equipped with an aluminum foil packaging device. The mixed raw materials need to be evenly divided according to the total weight of the aluminum foil and the total weight of other raw materials, and the weight of each package needs to be evenly divided. The packaging speed of the powder packaging machine is 10 to 30 packages / minute, the packaging capacity is 60 to 80 g / package, and the edge size of the "aluminum foil capsule powder package" is 20 to 40 mm.

[0018] Preferably, the layered layout is to place the "aluminum foil powder bags" as close to each other as possible and stack them layer by layer in an orderly manner. The purpose is to ensure that the self-propagating behavior of the thermite reaction can be continuous and sufficient, while improving the uniformity of the composition at different locations in the reactor body.

[0019] Furthermore, in step (2), the ignition agent is potassium permanganate, and the amount of potassium permanganate used is 30 to 50 g.

[0020] Preferably, the aluminum foil wrapped with the ignition agent is formed by placing 30-50 g of potassium permanganate ignition agent in a piece of aluminum foil and simply wrapping it to ensure that the potassium permanganate does not spill. The purpose is to ensure that the subsequent resistance wire can contact the ignition agent and that the thermite reaction can be smoothly triggered during ignition.

[0021] Furthermore, in step (2), the vacuum thermite reaction is specifically performed as follows: a nickel-chromium resistance wire is formed into a spiral shape, and then the two ends of the resistance wire are respectively connected to two aluminum wires of the circuit system in the furnace body, and the resistance wire is placed close to the potassium permanganate powder; the purpose is that the subsequent activation of the igniter will cause the resistance wire to heat up, stimulating the reaction between the potassium permanganate and the material, causing the system temperature to rise sharply, thereby promoting the thermite reaction. The vacuum thermite furnace is then evacuated to ≤10Pa, the evacuation is stopped, and argon gas is passed through until the vacuum degree reaches 200-300Pa, the igniter is activated to discharge, and the ignition current display shows 0, the ignition is terminated, and the vacuum is continued. At the same time, the furnace is cooled for 6-10 hours before being taken out of the furnace to obtain the primary vanadium aluminum alloy. The purpose is to ensure that the thermite reaction is within the optimal vacuum range and to achieve effective separation of oxygen and nitrogen gas phase impurities in the alloy ingot.

[0022] Furthermore, in step (3), the finishing treatment includes four steps: slag removal, crushing, sandblasting, and grinding.

[0023] Preferably, slag removal is to remove the upper layer of slag from the alloy ingot taken out of the vacuum aluminothermic furnace by smashing the slag with a hammer. Crushing is to use a hydraulic press to crush the alloy ingot into small pieces with an edge size of 50 to 100 mm. Sandblasting is to place the alloy ingots in a sandblasting machine to further remove the slag and impurity film that have not been removed around the alloy ingots. Grinding is to use an inert gas-protected continuous grinding equipment to grind the alloy ingot into particles with an edge size of 1 to 3 mm. The purpose is to ensure that the subsequent alkaline washing can fully remove the aluminum oxide impurities attached to the particles, thereby improving the purity of the alloy microstructure.

[0024] Furthermore, in step (4), the alkali washing is performed by completely immersing the alloy particles in an alkali washing tank containing a sodium hydroxide solution having a mass concentration of 4-6% and a soaking time of 20-30 minutes. During the soaking process, the alkali solution is appropriately stirred. This is to remove aluminum oxide inclusions present in the vanadium-aluminum alloy through the chemical reaction between aluminum oxide and sodium hydroxide, thereby reducing the impurity oxygen content in the final vanadium-aluminum alloy and significantly improving the purity of the alloy microstructure. Appropriate stirring of the alkali solution can increase the cleaning rate and improve the cleaning effect.

[0025] Preferably, the filtering is to pass the material in the alkali washing tank through the filter to screen out the alloy particles with an edge size of 1 to 3 mm. The vacuum drying is to place the screened alloy particles in a vacuum heat treatment furnace for vacuum drying, and the vacuum degree in the furnace is 10 -3 ~10 -5 Pa, heat treatment temperature is 100-120℃, holding time is 60-90min. Finally, out of the furnace, a vanadium-aluminum alloy with high purity, good composition uniformity and pure microstructure can be obtained.

[0026] A second object of the present invention is to provide an AlV65 alloy for aerospace-grade titanium alloy.

[0027] It can be seen from the above technical solutions that, compared with the prior art, the present invention has the following beneficial effects:

[0028] 1) This invention is the first to use both calcium oxide and cryolite as raw materials for a vacuum thermite reaction. Their simultaneous use reduces the temperature of the thermite reaction system, improves reaction kinetics, and dissolves alumina inclusions. This not only facilitates a thorough, full, and efficient thermite reaction, but also ensures good separation of the alloy ingot and slag after the thermite reaction, further improving the microstructural purity of the alloy ingot.

[0029] 2) This invention is the first to use "aluminum foil capsule powder bags" as raw materials for vacuum thermite reactions. The powder bags are stacked as closely as possible and in an orderly layer. This unique material form and distribution method, a first for thermite reactions, enables a more continuous and complete self-propagating reaction within the furnace, significantly improving the chemical composition uniformity at different locations within the alloy ingot.

[0030] 3) The present invention places the raw materials in a number of "aluminum foil capsule powder bags", which avoids direct contact between the raw materials and the surrounding refractory materials, furnace atmosphere, etc., and effectively reduces the content of impurity elements. Moreover, the subsequent alkali washing and vacuum heat treatment operations completely remove the aluminum oxide inclusions present in the vanadium aluminum alloy without causing an increase in oxygen and nitrogen gas phase impurities. Alkaline washing is applied to vanadium aluminum master alloys for the first time, effectively reducing the content of impurity elements in the alloy. More importantly, it significantly reduces the microscopic inclusions of aluminum oxide in the alloy, which can greatly improve the purity of the alloy's microstructure;

[0031] In summary, the present invention is unique and creative in the vanadium-aluminum intermediate alloy industry. For example, it is the first time that calcium oxide and cryolite are combined as raw materials for thermite reaction, the first time that "aluminum foil capsule powder bag" type materials are used, and the first time that an alkaline washing process is introduced. This unique coordinated comprehensive control of raw materials and processes ultimately leads to significant improvements in the purity, composition uniformity and microstructural purity of vanadium-aluminum alloys.

[0032] It's also worth noting that, based on currently published patents, there are virtually no reports on vanadium-aluminum alloys with impurity levels of oxygen and nitrogen below 0.01wt%, let alone microstructural purity. The present invention, through the coordinated selection of raw materials, material distribution, preparation, and post-processing methods, has for the first time produced a vanadium-aluminum 65 alloy with impurity levels of oxygen and nitrogen significantly below 0.01wt%, a chemical composition range below 0.01wt%, and excellent microstructural purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0034] Figure 1 Schematic diagram showing the material inside the crucible in a vacuum thermite furnace.

[0035] Figure 2 Schematic diagram showing the main element test positions of the alloy ingots prepared by Examples 1-3 and Comparative Examples 1-3.

[0036] Figure 3 Microstructure photographs of alloy particles prepared by Examples 1-3 and Comparative Examples 1-5: (a) Example 1; (b) Example 2; (c) Example 3; (d) Comparative Example 1; (e) Comparative Example 2; (f) Comparative Example 3; (g) Comparative Example 4; (h) Comparative Example 5; (i) Comparative Example 6; (j) Comparative Example 7. DETAILED DESCRIPTION

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0038] Example 1

[0039] A V-shaped mixer is used to mix the raw materials of aluminum particles (purity 99.8%, particle size 100 mesh), vanadium pentoxide (purity 99.9%, particle size 100 mesh), calcium oxide (purity 99.5%, particle size 300 mesh), and cryolite (purity 99.8%, particle size 300 mesh) evenly. The mixer speed is 40r / min and the mixing time is 30 minutes. A powder packaging machine is used to wrap the mixed raw materials into an "aluminum foil capsule powder bag" type material with an edge size of 30mm. The mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is 500:900:80:7:190. The "aluminum foil capsule powder bag" is placed in a vacuum thermite furnace in a layered layout with each layer tightly stacked. An aluminum foil wrapped with 30g of potassium permanganate ignition agent is placed at the top center of the material. A vacuum thermite reaction is then carried out to prepare a primary vanadium aluminum alloy. At this time, it is necessary to follow the Figure 2Take samples and test the chemical composition content of different positions of the alloy ingot. Then the alloy is deslagging, crushing, sandblasting and grinding operations are carried out in sequence to obtain particles with a size of 1 to 3 mm. Subsequently, the alloy particles are completely immersed in an alkaline washing tank with a concentration of 5% (mass fraction) of sodium hydroxide solution for 30 minutes, while stirring the alkaline solution appropriately. Then the material in the alkaline washing tank is filtered through a filter to filter out alloy particles with an edge size of 1 to 3 mm. The sieved alloy particles are placed in a vacuum heat treatment furnace for vacuum drying treatment, and the vacuum degree in the furnace is 10 -4 Pa, heat treatment temperature of 120 degrees Celsius, holding time of 60 minutes. Finally, vanadium-aluminum alloy particles were obtained from the furnace. Chemical composition testing and microstructural observation of the alloy particles were performed.

[0040] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.008wt% and 0.005wt% respectively, which meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.08wt% and 0.06wt% respectively, which are both less than 0.1wt%. The chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the alloy microstructure was relatively pure.

[0041] Example 2

[0042] The preparation method of this embodiment is similar to that of Example 1, except that the mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is 490:910:85:6:190.

[0043] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.009wt% and 0.007wt% respectively, which meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.06wt% and 0.05wt% respectively, which are both less than 0.1wt%. The chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the alloy microstructure was relatively pure.

[0044] Example 3

[0045] The preparation method of this embodiment is similar to that of Example 1, except that the edge size of the "aluminum foil capsule powder bag" is 40 mm.

[0046] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.006wt% and 0.007wt% respectively, which meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.07wt% and 0.05wt% respectively, which are both less than 0.1wt%. The chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the alloy microstructure was relatively pure.

[0047] Comparative Example 1

[0048] The preparation method for this comparative example was similar to that of Example 1, except that no aluminum foil was used in the raw materials. The mass ratio of aluminum granules, vanadium pentoxide, calcium oxide, and cryolite was 690:900:80:7, and no "aluminum foil capsule" was prepared. After the raw materials were evenly mixed, they were placed directly in a vacuum thermite furnace, and 30g of potassium permanganate was placed at the center of the top of the materials.

[0049] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.021wt% and 0.012wt% respectively, which does not meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.66wt% and 0.46wt% respectively, which are far more than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is poor. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0050] In summary, the failure to use aluminum foil to prepare the "aluminum foil capsule powder bag" material has a great impact on the gas phase impurity element content, chemical composition uniformity, and microstructure purity.

[0051] Comparative Example 2

[0052] The preparation method of this comparative example is similar to that of Example 1, except that: there is no cryolite in the raw materials, and the mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, and aluminum foil is 500:900:87:190.

[0053] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.039wt% and 0.015wt% respectively, which does not meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.09wt% and 0.06wt% respectively, which are both less than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0054] In summary, the failure to use cryolite and calcium oxide simultaneously has a significant impact on the gas phase impurity element content and microstructure purity.

[0055] Comparative Example 3

[0056] The preparation method of this comparative example is similar to that of Example 1, except that: there is no calcium oxide in the raw materials, and the mass ratio of aluminum particles, vanadium pentoxide, cryolite, and aluminum foil is 500:900:87:190.

[0057] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.035wt% and 0.013wt% respectively, which does not meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.07wt% and 0.08wt% respectively, which are both less than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0058] In summary, the failure to use calcium oxide and cryolite simultaneously has a significant impact on the content of gas-phase impurity elements and the purity of the microstructure.

[0059] Comparative Example 4

[0060] The preparation method of this comparative example is similar to that of Example 1, except that the ratio of calcium oxide and cryolite in the raw materials is different (the ratio is not within the scope of the present invention), and the mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is 500:900:95:5:190, that is, 100:180:19:1:38.

[0061] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.018wt% and 0.015wt% respectively, which does not meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.06wt% and 0.07wt% respectively, which are both less than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0062] In summary, the usage ratio of calcium oxide and cryolite is not within the scope of the present invention, which has a great impact on the content of gas-phase impurity elements and the purity of the microstructure.

[0063] Comparative Example 5

[0064] The preparation method of this comparative example is similar to that of Example 1, except that the alloy particles are not subjected to the alkaline washing, filtration, and vacuum heat treatment steps. After the vacuum thermite reaction furnace, the alloy is sequentially subjected to slag removal, crushing, sandblasting, and grinding to obtain particles with a size of 1 to 3 mm.

[0065] As shown in Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.037wt% and 0.010wt% respectively, which does not meet the target of oxygen and nitrogen content less than 0.01wt% respectively. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum in different positions of the alloy ingot are 0.07wt% and 0.06wt% respectively, which are both less than 0.1wt%. The chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0066] In summary, the lack of alkaline washing, filtration, and vacuum heat treatment of alloy particles will make it difficult to remove inclusions such as alumina in the alloy, ultimately leading to excessively high oxygen content of impurity elements and poor purity of the microstructure.

[0067] Comparative Example 6

[0068] The preparation method of this comparative example is similar to that of Example 1, except that: when the alloy particles are alkali-washed, the concentration of the sodium hydroxide solution is 2% (mass fraction).

[0069] As shown in Table 1, the gaseous impurity element oxygen in the alloy is 0.031wt%, which does not meet the target of oxygen content less than 0.01wt%. As shown in Table 2, the extreme differences of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.07wt% and 0.06wt% respectively, both less than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is good. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, and the alloy microstructure is impure.

[0070] In summary, when the concentration of the alloy particles during alkali washing is lower than the range of the present invention, the removal effect of inclusions such as aluminum oxide in the alloy will become very poor, and ultimately lead to excessively high oxygen content of impurity elements and poor purity of the microstructure.

[0071] Comparative Example 7

[0072] The preparation method of this comparative example is similar to that of Example 1, except that the mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil in the raw materials is 96:184:14:1:32.

[0073] As can be seen from Table 1, the gaseous impurity elements oxygen and nitrogen in the alloy are 0.009wt% and 0.006wt% respectively, which meet the goal of oxygen and nitrogen content being less than 0.01wt% respectively. However, the content of vanadium element is 75.82wt%, which does not reach the goal of preparing AlV65 (V content is 62-68wt%). As can be seen from Table 2, the extreme differences of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.14wt% and 0.16wt% respectively, which are both greater than 0.1wt%, indicating that the chemical composition uniformity of the alloy ingot is slightly poor. It can be seen that changes in the quality and proportion of raw materials can cause changes in the heat, speed and other conditions of the thermite reaction, and the chemical composition uniformity of the alloy ingot is slightly reduced. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the alloy microstructure was relatively pure.

[0074] In summary, the quality and proportion of the raw materials are not within the scope of the present invention, it is difficult to obtain AlV65 alloy, and the chemical composition uniformity of the alloy ingot is slightly poor.

[0075] Table 1 shows the chemical composition results of the alloy particles prepared in Examples 1-3 and Comparative Examples 1-5 (unit: wt %).

[0076] Table 1

[0077]

[0078]

[0079] Table 2 shows the main element contents at different positions in the alloy ingots prepared by Examples 1-3 and Comparative Examples 1-5 (unit: wt %).

[0080] Table 2

[0081]

[0082] The above description of the disclosed embodiments is intended to enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is intended to conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy, characterized in that: The following steps are involved: (1) High-purity aluminum particles, vanadium pentoxide, calcium oxide, and cryolite are mixed evenly, and the mixed raw materials are wrapped with aluminum foil to prepare a number of "aluminum foil capsule powder bags"; (2) Placing the "aluminum foil capsule powder bag" in a layered layout with each layer tightly stacked in a vacuum aluminothermic furnace, placing an aluminum foil wrapped with an ignition agent at the center of the top of the material, and performing a vacuum aluminothermic reaction to produce a primary vanadium aluminum alloy; (3) performing a finishing treatment on the primary vanadium-aluminum alloy to obtain alloy particles; (4) The alloy particles are sequentially subjected to alkali washing, filtration, and vacuum drying to obtain AlV65 alloy.

2. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (1), the purity of the high-purity aluminum particles and vanadium pentoxide are both ≥99.8%, and the particle size is 80-120 mesh; the purity of the calcium oxide and cryolite are both ≥99.5%, and the particle size is 290-310 mesh.

3. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (1), the mass ratio of the high-purity aluminum particles, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is (490-510): (890-910): (70-90): (6-8): (180-200).

4. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (1), the edge size of the "aluminum foil capsule powder bag" is 20 to 40 mm.

5. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (2), the ignition agent is potassium permanganate, and the amount of potassium permanganate is 30 to 50 g.

6. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (2), the vacuum thermite reaction is specifically performed as follows: a nickel-chromium resistance wire is formed into a spiral shape, and then both ends of the resistance wire are respectively connected to two aluminum wires of the circuit system in the furnace body, and the resistance wire is placed close to the potassium permanganate powder; then the vacuum thermite furnace is evacuated to a vacuum degree of ≤10Pa, the evacuation is stopped, argon gas is passed through until the vacuum degree is 200-300Pa, the igniter is started to discharge, and the ignition current display number is 0, the ignition is ended, and the vacuum is continued. At the same time, the furnace is cooled for 6-10 hours before being taken out of the furnace to obtain a primary vanadium aluminum alloy.

7. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (3), the finishing treatment includes four steps: slag removal, crushing, sandblasting, and grinding.

8. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (3), the edge size of the alloy particles is 1 to 3 mm.

9. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloy according to claim 1, characterized in that: In step (4), the alkali washing is to completely immerse the alloy particles in a sodium hydroxide solution, the mass concentration of the sodium hydroxide solution is 4-6%, and the immersion time is 20-30 minutes.

10. Use of the vanadium-aluminum master alloy prepared by the preparation method according to any one of claims 1 to 9 in AlV65 alloy.

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