A vanadium-aluminum master alloy for aerospace-grade titanium alloys and its preparation method

Abstract

This invention relates to the field of intermediate alloy preparation technology for aerospace-grade titanium alloys, and discloses a vanadium-aluminum intermediate alloy for aerospace-grade titanium alloys and its preparation method. The alloy preparation uses high-purity aluminum granules, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil as raw materials. First, a primary alloy is prepared using a vacuum aluminothermic method based on an "aluminum foil-encased powder package" material. Then, the primary alloy undergoes finishing treatment to obtain alloy particles. These particles are then subjected to alkaline washing, filtration, and vacuum heat treatment, ultimately yielding an AlV65 alloy with higher purity, better compositional uniformity, and a purer microstructure. This method effectively addresses the challenges of high vapor phase impurity content, significant component segregation, and numerous microscopic inclusions in existing vanadium-aluminum alloys, and is of great significance for building a more resilient aerospace industry chain and promoting high-quality industrial development.

Description

Technical Field

[0001] This invention relates to the field of intermediate alloy preparation technology for aerospace-grade titanium alloys, and more specifically to a method for preparing vanadium-aluminum alloys with higher purity, better compositional uniformity, and purer microstructure. Background Technology

[0002] Currently, driven by both the rapid iteration of aerospace technology and surging demand, the titanium alloy industry chain is ushering in unprecedented development opportunities. Master alloys and sponge titanium, as the main raw materials for smelting and preparing titanium alloys, hold significant strategic importance in the industry chain.

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

[0004] The main production processes for vanadium-aluminum master alloys include one-step (aluminothermic) and two-step (aluminothermic + induction melting) methods. The one-step method involves a direct aluminothermic reaction in atmospheric conditions, resulting in alloys with lower purity, more severe component segregation, and a higher number of microscopic impurities. Patent CN110592453B discloses a one-step method for preparing vanadium-aluminum alloys; however, its goal is only to achieve an oxygen content below 0.04 wt%, without addressing the nitrogen impurity index or the issues of compositional uniformity and microstructure purity in different regions of the alloy ingot. The two-step method involves a longer process flow, requires more expensive induction melting equipment, increases production costs, and results in lower output per furnace, with limited improvement in alloy purity and microstructure purity. Patent CN103849787A discloses a two-step method for preparing vanadium-aluminum alloys, but after the aluminothermic process, precise calculation of the aluminum content required for induction melting is necessary, leading to complex batching. Furthermore, both oxygen and nitrogen impurities are not less than 0.02 wt%, and similarly, the issue of microstructure purity is not addressed. These methods are insufficient 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 attracted much attention in the industry. However, the vacuum method relies solely on its own exothermic reaction to maintain the separation of the alloy from the slag, making it impossible to control the stable release of heat and ensuring the quality of the alloy. Patent CN117604354A discloses the preparation of vanadium-aluminum alloys using a vacuum reactor; however, the mixed materials need to be dried, the bottom of the crucible needs to be covered with vanadium-aluminum return slag, and the impurity elements oxygen and nitrogen are both not less than 0.01 wt%, failing to address the issues of compositional uniformity and microstructure purity in different regions of the alloy ingot.

[0006] In summary, vanadium-aluminum master alloys prepared using current processes suffer from problems such as high impurity content, severe compositional segregation, and numerous microscopic inclusions, which limit the high-quality development of the titanium alloy industry. Furthermore, it is worth noting that published patents often focus on vanadium-aluminum alloys such as AlV55 and AlV85, lacking reports on AlV65 alloys (V content 62–68 wt%), while AlV65 alloys have greater international applicability.

[0007] Therefore, how to provide a method for preparing vanadium-aluminum alloys to solve the above problems, and to prepare them using AlV65 alloy as the target, has become an urgent problem to be solved in the current titanium alloy industry chain, and is also the key to the future development of aerospace technology. Summary of the Invention

[0008] In view of this, the present invention provides a vanadium-aluminum master alloy for aerospace-grade titanium alloys and its preparation method, focusing on solving the problems of high oxygen and nitrogen gaseous impurity content, severe chemical composition segregation, and numerous microscopic inclusions in existing alloys. Meanwhile, the present invention uses AlV65 alloy as the research object.

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

[0010] (1) Mix high-purity aluminum granules, vanadium pentoxide, calcium oxide and cryolite raw materials evenly, and use a powder packaging machine equipped with aluminum foil packaging device to wrap the mixed raw materials to make several "aluminum foil capsule powder bags";

[0011] (2) The “aluminum foil bag-shaped powder package” is placed in a vacuum aluminothermic furnace in a layered layout with each layer tightly stacked. An aluminum foil containing an ignition agent is placed at the center of the top of the material. Then, a vacuum aluminothermic reaction is carried out to obtain a primary vanadium-aluminum alloy.

[0012] (3) The primary vanadium-aluminum alloy is finished to obtain alloy particles;

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

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

[0015] Preferably, the raw materials are mixed uniformly, i.e., a V-shaped mixer is used to mix the raw materials at a speed of 30-50 r / min for a mixing time of 20-40 min. The purpose is to ensure uniform mixing of the raw materials, which is beneficial for the full progress of the subsequent aluminothermic reduction reaction, thereby further improving the uniformity of the chemical composition in the alloy ingot.

[0016] Furthermore, in step (1), considering that aluminum foil is used to wrap the powder and that the aluminum foil also serves as a raw material for the aluminothermic reaction, the weight of the aluminum foil needs to be incorporated into the raw material ratio. The mass ratio of the high-purity aluminum granules, 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, wherein the V content is between 62 and 68 wt%.

[0017] Furthermore, in step (1), the powder packaging machine equipped with an aluminum foil packaging device is used to wrap the mixed raw materials. This is based on the total weight of the aluminum foil and the total weight of the other raw materials, and the materials are evenly distributed according to the weight of a single package. The packaging speed of the powder packaging machine is 10 to 30 packages / minute, and the packaging capacity is 60 to 80g / package. The edge size of the "aluminum foil bag-shaped powder package" is 20 to 40mm.

[0018] Preferably, the layered layout involves stacking the aluminum foil-shaped powder packets as close to each other as possible, layer by layer in an orderly manner. The purpose is to ensure the continuous and complete self-propagating behavior of the aluminothermic reaction, while simultaneously improving the compositional uniformity at different locations within the reactor.

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

[0020] Preferably, the aluminum foil used to wrap the igniter is simply a piece of aluminum foil containing 30-50g of potassium permanganate igniter, wrapped to prevent spillage. The purpose is to ensure that the resistance wire can contact the igniter and that the aluminothermic reaction can be successfully triggered during ignition.

[0021] Further, in step (2), the vacuum aluminothermic reaction is specifically operated as follows: a nickel-chromium resistance wire is made into a spiral shape, and then the two ends of the resistance wire are connected to two aluminum wires in the circuit system inside the furnace, and the resistance wire is brought close to the potassium permanganate powder; the purpose is that the subsequent start of the igniter will cause the resistance wire to heat up, which will stimulate the reaction between potassium permanganate and the material, and the system temperature will rise sharply, thus promoting the aluminothermic reaction. Then, the vacuum aluminothermic furnace is evacuated to ≤10Pa, the evacuation is stopped, argon gas is introduced until the vacuum degree is 200-300Pa, the igniter is started to discharge, the ignition ammeter reading is 0, the ignition ends, the vacuum is continued, and 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 aluminothermic reaction is within the optimal vacuum degree range and to achieve effective separation of oxygen and nitrogen gaseous impurities in the alloy ingot.

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

[0023] Preferably, slag removal involves removing the top layer of slag from the alloy ingot taken from the vacuum aluminothermic furnace, which can be done by hammering off the slag. Crushing involves using a hydraulic press to crush the alloy ingot into small pieces with an edge size of 50-100mm. Sandblasting involves placing the small alloy pieces in a sandblasting machine to further remove any remaining slag and impurity film around the pieces. Grinding involves using an inert gas-protected continuous grinding equipment to grind the alloy ingot into particles with an edge size of 1-3mm. The purpose is to ensure that subsequent alkaline washing can effectively remove the alumina impurities attached to the particles, thereby improving the purity of the alloy's microstructure.

[0024] Furthermore, in step (4), the alkaline washing involves completely immersing the alloy particles in an alkaline washing tank containing a sodium hydroxide solution with a mass concentration of 4-6% for 20-30 minutes. During the immersion process, the alkaline solution is stirred appropriately. The purpose is to remove the alumina inclusions present in the vanadium-aluminum alloy through the chemical reaction between alumina and sodium hydroxide, thereby reducing the impurity oxygen content in the final vanadium-aluminum alloy and significantly improving the purity of the alloy's microstructure. Appropriate stirring of the alkaline solution can increase the cleaning rate and improve the cleaning effect.

[0025] Preferably, the filtration involves passing the material in the alkaline washing tank through a filter screen to separate alloy particles with an edge size of 1-3 mm. The vacuum drying involves placing the separated alloy particles in a vacuum heat treatment furnace for vacuum drying, with a vacuum degree of 10... -3 ~10 -5 The heat treatment temperature is 100–120℃, and the holding time is 60–90 min. The final product obtained is a vanadium-aluminum alloy with high purity, good compositional uniformity, and a relatively pure microstructure.

[0026] The second objective of this invention is to provide an AlV65 alloy for aerospace-grade titanium alloys.

[0027] As can be seen from the above technical solution, compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0028] 1) This invention is the first to use calcium oxide and cryolite together as raw materials for vacuum aluminothermic reaction. The simultaneous use of the two has the effects of lowering the temperature of the aluminothermic reaction system, improving reaction kinetics, and dissolving alumina inclusions. This not only facilitates a thorough, complete, and efficient aluminothermic reaction, but also ensures good separation of the alloy ingot and slag after the aluminothermic reaction, and further improves the microstructure purity of the alloy ingot.

[0029] 2) This invention is the first to use "aluminum foil bag-shaped powder pack" as the material for vacuum aluminothermic reaction, and each powder pack is stacked as close to each other as possible and layer by layer in an orderly manner. This special material form and distribution method is the first to be applied to aluminothermic reaction, which makes the self-propagating reaction in the furnace more continuous and more complete, and can greatly improve the uniformity of chemical composition in different positions of alloy ingot.

[0030] 3) This invention places the raw material within several "aluminum foil-shaped powder packets," avoiding direct contact between the raw material and surrounding refractory materials and the furnace atmosphere, effectively reducing the content of impurity elements. Furthermore, the subsequent alkaline washing and vacuum heat treatment operations thoroughly remove alumina inclusions from the vanadium-aluminum alloy without increasing oxygen and nitrogen gaseous impurities. Alkaline washing is being applied for the first time to vanadium-aluminum master alloys, effectively reducing the content of impurity elements in the alloy. More importantly, it significantly reduces microscopic alumina inclusions in the alloy, greatly improving the purity of the alloy's microstructure.

[0031] In summary, this invention is uniquely innovative in the vanadium-aluminum master alloy industry. For example, it is the first to combine calcium oxide and cryolite as raw materials for the aluminothermic reaction, the first to use "aluminum foil-shaped powder package" materials, and the first to introduce alkaline washing process. This unique synergistic and comprehensive control of raw materials and processes ultimately leads to significant improvements in the purity, compositional uniformity, and microstructure purity of vanadium-aluminum alloys.

[0032] Furthermore, it is worth noting that, based on currently published patents, there are almost no reports on vanadium-aluminum alloys with impurity oxygen and nitrogen levels both below 0.01 wt%, and even fewer reports on microstructural purity. This invention, through the synergistic coordination of raw material selection, material distribution method, preparation method, and post-processing method, has for the first time successfully prepared a vanadium-aluminum 65 alloy with impurity oxygen and nitrogen levels significantly below 0.01 wt%, a chemical composition range both below 0.01 wt%, and good microstructural purity. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 This diagram illustrates the material distribution inside the crucible in a vacuum aluminothermic furnace.

[0035] Figure 2 This diagram shows the main element test locations of the alloy ingots prepared by Examples 1-3 and Comparative Examples 1-3.

[0036] Figure 3 Micrographs showing the microstructure 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 Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] Example 1

[0039] A V-shaped mixer was used to uniformly mix aluminum granules (99.8% purity, 100 mesh), vanadium pentoxide (99.9% purity, 100 mesh), calcium oxide (99.5% purity, 300 mesh), and cryolite (99.8% purity, 300 mesh). The mixer speed was 40 r / min, and the mixing time was 30 minutes. A powder packaging machine was used to package the mixed materials into "aluminum foil capsule-shaped powder packages" with an edge size of 30 mm. The mass ratio of aluminum granules, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil was 500:900:80:7:190. The "aluminum foil capsule-shaped powder packages" were placed in a vacuum aluminothermic furnace in a layered layout with each layer tightly stacked. A piece of aluminum foil containing 30g of potassium permanganate igniter was placed at the center of the top of the material. Then, a vacuum aluminothermic reaction was carried out to prepare a primary vanadium-aluminum alloy. At this point, it is necessary to... Figure 2Sampling was performed to test the chemical composition of the alloy ingot at different locations. The alloy was then subjected to slag removal, crushing, sandblasting, and grinding processes to obtain particles with a size of 1–3 mm. Subsequently, the alloy particles were completely immersed in an alkaline washing tank containing a 5% (mass fraction) sodium hydroxide solution for 30 minutes, with appropriate stirring of the alkaline solution. The material in the alkaline washing tank was then sieved through a filter screen to obtain alloy particles with an edge size of 1–3 mm. The sieved alloy particles were then placed in a vacuum heat treatment furnace for vacuum drying at a vacuum level of 10 °C. -4 The heat treatment was carried out at 120°C for 60 minutes. The resulting vanadium-aluminum alloy particles were then removed from the furnace. The chemical composition and microstructure of the alloy particles were then analyzed.

[0040] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.008 wt% and 0.005 wt%, respectively, meeting the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.08 wt% and 0.06 wt%, respectively, both less than 0.1 wt%, indicating good chemical composition uniformity of the alloy ingot. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the microstructure of the alloy is 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 granules, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is 490:910:85:6:190.

[0043] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.009 wt% and 0.007 wt%, respectively, meeting the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.06 wt% and 0.05 wt%, respectively, both less than 0.1 wt%, indicating good chemical composition uniformity of the alloy ingot. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the microstructure of the alloy is relatively pure.

[0044] Example 3

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

[0046] Table 1 shows that the gaseous impurity elements oxygen and nitrogen in the alloy are 0.006 wt% and 0.007 wt%, respectively, meeting the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.07 wt% and 0.05 wt%, respectively, both less than 0.1 wt%, indicating good chemical composition uniformity of the alloy ingot. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the microstructure of the alloy is relatively pure.

[0047] Comparative Example 1

[0048] The preparation method of this comparative example is similar to that of Example 1, except that: aluminum foil is not used in the raw materials, and the mass ratio of aluminum granules, vanadium pentoxide, calcium oxide, and cryolite is 690:900:80:7, and it is not prepared into an "aluminum foil capsule powder package". After the raw materials are mixed evenly, they are placed directly in a vacuum aluminothermic furnace, and 30g of potassium permanganate is placed at the center of the top of the material.

[0049] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.021 wt% and 0.012 wt%, respectively, failing to meet the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different locations in the alloy ingot are 0.66 wt% and 0.46 wt%, respectively, both far exceeding 0.1 wt%, indicating poor chemical composition uniformity of the alloy ingot. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, indicating that the microstructure of the alloy is impure.

[0050] In summary, the use of non-aluminum foil in the preparation of "aluminum foil capsule powder" materials has a significant impact on the content of gaseous impurity elements, the uniformity of chemical composition, and the purity of microstructure.

[0051] Comparative Example 2

[0052] The preparation method of this comparative example is similar to that of Example 1, except that cryolite is not included in the raw materials, and the mass ratio of aluminum particles, vanadium pentoxide, calcium oxide, and aluminum foil is 500:900:87:190.

[0053] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.039 wt% and 0.015 wt%, respectively, which does not meet the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different locations in the alloy ingot are 0.09 wt% and 0.06 wt%, respectively, both less than 0.1 wt%, indicating that the chemical composition of the alloy ingot is relatively uniform. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, indicating that the microstructure of the alloy is impure.

[0054] In summary, the failure to use cryolite and calcium oxide simultaneously significantly impacts the content of gaseous impurity elements and the purity of the microstructure.

[0055] Comparative Example 3

[0056] The preparation method of this comparative example is similar to that of Example 1, except that: calcium oxide is not included in the raw materials, and the mass ratio of aluminum particles, vanadium pentoxide, cryolite, and aluminum foil is 500:900:87:190.

[0057] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.035 wt% and 0.013 wt%, respectively, which does not meet the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different locations in the alloy ingot are 0.07 wt% and 0.08 wt%, respectively, both less than 0.1 wt%, indicating that the chemical composition of the alloy ingot is relatively uniform. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, indicating that the microstructure of the alloy is impure.

[0058] In summary, the failure to use calcium oxide and cryolite simultaneously significantly impacts the content of gaseous 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 this invention). 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] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.018 wt% and 0.015 wt%, respectively, which does not meet the target of oxygen and nitrogen contents being less than 0.01 wt%. Table 2 shows that the ranges of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.06 wt% and 0.07 wt%, respectively, both less than 0.1 wt%, indicating that the chemical composition of the alloy ingot is relatively uniform. Figure 3 It can be seen that inclusions such as black alumina of various shapes and sizes can be observed, indicating that the microstructure of the alloy is impure.

[0062] In summary, the ratio of calcium oxide and cryolite used is outside the scope of this invention, which has a significant impact on the content of gaseous 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 were not subjected to alkaline washing, filtration, or vacuum heat treatment. After the vacuum aluminothermic reaction, the alloy was subjected to slag removal, crushing, sandblasting, and grinding operations in sequence to obtain particles with a size of 1-3 mm.

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

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

[0067] Comparative Example 6

[0068] The preparation method of this comparative example is similar to that of Example 1, except that the concentration of sodium hydroxide solution during alkaline washing of the alloy particles is 2% (mass fraction).

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

[0070] In summary, if the concentration of alkaline washing of alloy particles is lower than that of this invention, the removal effect of inclusions such as alumina in the alloy will be very poor, ultimately resulting in excessively high oxygen content of impurity elements and poor microstructure purity.

[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 granules, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil in the raw materials is 96:184:14:1:32.

[0073] Table 1 shows that the gaseous impurities oxygen and nitrogen in the alloy are 0.009 wt% and 0.006 wt%, respectively, meeting the target of oxygen and nitrogen contents being less than 0.01 wt%. However, the vanadium content is 75.82 wt%, failing to meet the target for preparing AlV65 (V content 62-68 wt%). Table 2 shows that the ranges of the main elements vanadium and aluminum at different positions in the alloy ingot are 0.14 wt% and 0.16 wt%, respectively, both greater than 0.1 wt%, indicating slightly poor chemical composition uniformity of the alloy ingot. It is evident that changes in raw material quality and proportions can alter the heat, rate, and other states of the aluminothermic reaction, slightly reducing the chemical composition uniformity of the alloy ingot. Figure 3 It can be seen that no inclusions such as black alumina were observed, and the microstructure of the alloy is relatively pure.

[0074] In summary, since the quality and proportion of raw materials are not within the scope of this 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 (unit: wt%) of the alloy particles prepared in Examples 1-3 and Comparative Examples 1-5.

[0076] Table 1

[0077]

[0078]

[0079] Table 2 shows the content of major elements 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 enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those 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 invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded 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 alloys, characterized in that, Includes the following steps: (1) Mix high-purity aluminum granules, vanadium pentoxide, calcium oxide and cryolite raw materials evenly, wrap the mixed raw materials with aluminum foil, and make several "aluminum foil capsule powder packets"; (2) The "aluminum foil bag-shaped powder package" is placed in a vacuum aluminothermic furnace in a layered layout with each layer tightly stacked. An aluminum foil containing an ignition agent is placed at the center of the top of the material to carry out a vacuum aluminothermic reaction and obtain a primary vanadium-aluminum alloy. (3) The primary vanadium-aluminum alloy is finished to obtain alloy particles; (4) The alloy particles were successively subjected to alkaline washing, filtration and vacuum drying to obtain AlV65 alloy; In step (1), the mass ratio of the high-purity aluminum granules, vanadium pentoxide, calcium oxide, cryolite, and aluminum foil is (490-510):(890-910):(70-90):(6-8):(180-200). In step (4), the alkaline washing involves completely immersing the alloy particles in a sodium hydroxide solution with a mass concentration of 4-6% and an immersion time of 20-30 minutes.

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

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

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

5. The method for preparing a vanadium-aluminum master alloy for aerospace-grade titanium alloys according to claim 1, characterized in that, In step (2), the vacuum aluminothermic reaction is specifically operated as follows: the nickel-chromium resistance wire is made into a spiral shape, and then the two ends of the resistance wire are connected to the two aluminum wires of the circuit system in the furnace body respectively, and the resistance wire is close to the potassium permanganate powder; then the vacuum aluminothermic furnace is evacuated to ≤10Pa, the evacuation is stopped, argon gas is introduced until the vacuum degree is 200~300Pa, the igniter is started to discharge, the ignition ammeter reading is 0, the ignition ends, the evacuation continues, and the furnace is cooled for 6~10h before being taken out of the furnace to obtain the primary vanadium-aluminum alloy.

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

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

8. The application of a vanadium-aluminum master alloy prepared by any one of the preparation methods of claims 1-7 in AlV65 alloy.

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