Aluminum-scandium alloy and preparation method and application thereof

Abstract

The invention discloses an aluminum-scandium alloy and a preparation method and application thereof, and belongs to the technical field of rare earth alloy sputtering target materials, metal aluminum particles and metal scandium particles are used as raw materials, high vacuum is extracted, inert gas is introduced for multiple times of electric arc melting, aluminum-scandium alloy melt with uniform components is obtained, and after the aluminum-scandium alloy melt is cooled, the aluminum-scandium alloy is obtained. The method comprises the following steps: preparing an aluminum-scandium alloy ingot, carrying out induction heating on the aluminum-scandium alloy ingot prepared by electric arc melting to completely melt the alloy so as to obtain an alloy melt, guiding the alloy melt to be injected into a mold through an argon pressure difference, naturally cooling to form a primary alloy, and carrying out homogenizing annealing on the primary alloy under a vacuum condition to obtain the aluminum-scandium alloy. And eliminating the residual internal stress of the primary alloy to obtain the aluminum-scandium alloy. The aluminum-scandium alloy prepared through the method is low in oxygen content, high in density, fine in crystal grain, uniform in structure and good in machining performance.

Description

Technical Field

[0001] The invention relates to the technical field of rare earth alloy sputtering target materials, and in particular to an aluminum-scandium alloy and a preparation method and application thereof. Background Art

[0002] With the rapid development of 5G communication technology, the development trend of high performance, high stability and high frequency has put forward higher requirements for piezoelectric films used in micro-electromechanical systems and new generation RF filters. High-purity aluminum-scandium alloy target is an important raw material for preparing aluminum-scandium nitride piezoelectric films. Sc-doped AlN piezoelectric films have high SAW wave velocity, high thermal stability and high thermal conductivity. Compared with AlN films, they have higher and better piezoelectric properties and are even compatible with CMOS processes.

[0003] Scandium aluminum nitride is an ideal material for the preparation of piezoelectric micro-electromechanical systems and NEMS devices with high acoustic velocity and high power. The addition of the rare earth element scandium will solve the problem of low piezoelectric coefficient and low electromechanical coupling coefficient of aluminum nitride piezoelectric film, realize the integration of low insertion loss, high bandwidth, high integration and high operating frequency, and make important progress in surface acoustic waves, thin film bulk acoustic wave resonators, piezoelectric ultrasonic transducers, power electronic devices, micro energy systems and high electron mobility field effect transistors, providing technical support for 5G communications and the Internet of Things.

[0004] Common methods for producing aluminum-scandium alloys include doping, molten salt electrolysis, thermal reduction, and powder sintering. The patent with publication number CN111455327A proposes a method for preparing an aluminum-scandium alloy target with a high scandium content, wherein metal aluminum and metal scandium are selected for batching, the metal scandium is melted, and then the metal aluminum is added to the metal scandium for smelting in multiple times, and the final aluminum-scandium alloy is ball-milled, vacuum dried to obtain an alloy powder, and the powder is pre-pressed and vacuum sintered. The patent with publication number CN113981386A proposes a process for preparing an aluminum-scandium alloy target with a high scandium content, wherein scandium powder and Al3Sc powder are selected for batching and sintering.

[0005] Although the above method of preparing aluminum-scandium alloy by powder can greatly reduce the problems such as pores inside the alloy, due to the certain risk factor of powder and the air absorption phenomenon of alloy powder, the obtained aluminum-scandium alloy target will contain various impurities, the prepared target is difficult to densify and the purity is reduced. Summary of the invention

[0006] The present invention provides an aluminum-scandium alloy and a preparation method and application thereof, which effectively solve the technical problems that the existing aluminum-scandium alloy uses powder raw materials, which is dangerous and the prepared alloy target contains impurities of insufficient purity and a non-dense structure due to the air absorption phenomenon of the alloy powder; at the same time, an aluminum-scandium alloy with uniform organizational structure and chemical composition, high relative density, excellent processing performance and small grain size is constructed.

[0007] The present invention provides a method for preparing an aluminum-scandium alloy, comprising the following steps:

[0008] In an inert gas, the metal scandium particles and the metal aluminum particles are subjected to multiple vacuum arc melting at 1300° C. to 1500° C. to alloy and obtain an aluminum-scandium alloy ingot;

[0009] The aluminum-scandium alloy ingot is melted by vacuum induction heating to obtain an alloy melt, the alloy melt is spray-casted, cooled and solidified to obtain a primary alloy, and the primary alloy is annealed under vacuum conditions at 200° C. to 800° C. to eliminate residual internal stress of the primary alloy to obtain an aluminum-scandium alloy.

[0010] As a preferred embodiment, in the aluminum-scandium alloy, the content of metal scandium is 10% to 50%, and the content of metal aluminum is 50% to 90%, which is 100% in total.

[0011] As a preferred embodiment, the vacuum arc melting is carried out by program-controlled current, firstly the current is increased to perform arc melting and alloying, and then the current is decreased to obtain an aluminum-scandium alloy ingot; the program-controlled current is specifically:

[0012] Current increase procedure: from 0A, increase by 10A to 20A at a time and maintain for 1min to 3min, and then increase to 90A to 180A;

[0013] Current reduction procedure: from 90A~180A, reduce by 10A~15A at a time and keep it for 1min~2min, then reduce to 50A~90A; reduce by 6A~10A at a time and keep it for 2min~3min, then reduce to 50A; then reduce by 5A~8A at a time and keep it for 2min~3min, then reduce to 0A.

[0014] As a preferred implementation manner, the multiple vacuum arc melting processes are 4 to 8 times, and the duration of each vacuum arc melting process is 60 to 80 minutes.

[0015] As a preferred embodiment, the vacuum induction heating is carried out using a vacuum induction melting furnace, the induction heating power supply is a 35KW IGBT high-frequency power supply, the preheating current of the vacuum induction melting furnace is 1A to 10A, the duration is 1min to 2min, the melting heating current is 5A to 30A, and the duration is 2min to 3min.

[0016] As a preferred embodiment, the spray casting is performed using an argon pressure difference, and the argon pressure difference is 0.0025 MPa to 0.02 MPa.

[0017] As a preferred embodiment, the vacuum condition is 1×10 -3 pa~5×10 -3 pa.

[0018] As a preferred implementation manner, the annealing treatment time is 8h to 24h.

[0019] The second object of the present invention is to provide an aluminum-scandium alloy prepared by the above preparation method.

[0020] The third object of the present invention is to provide an application of the aluminum-scandium alloy in the preparation of aluminum-scandium nitride piezoelectric thin films or as a sputtering target for thin film bulk acoustic wave resonators or bulk acoustic wave devices.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] The present invention uses metal aluminum particles and metal scandium particles as raw materials, extracts high vacuum and introduces inert gas for multiple arc melting to obtain aluminum-scandium alloy melt with uniform composition, and waits for the aluminum-scandium alloy melt to cool to obtain aluminum-scandium alloy ingot; multiple arc melting can ensure the uniform distribution of each element in the alloy, and the concentration of different elements is uniformized in the molten metal; multiple arc melting reduces macroscopic and microscopic defects in the material, such as pores, inclusions and segregation, and the presence of these defects will affect the mechanical properties and corrosion resistance of the material. These defects are reduced by multiple melting, thereby obtaining a more uniform microstructure; arc melting in a vacuum or protective atmosphere reduces metal oxidation and contamination, thereby improving the purity of the material, which is particularly important for alloys that require high purity; during the arc melting process, due to the high temperature of the alloy melt, some impurities and gases are removed, thereby helping to improve the purity and performance of the material. The aluminum-scandium alloy ingot prepared by arc melting is completely melted by induction heating to obtain an alloy melt, and the alloy melt is injected into a mold by injecting argon gas, and a primary alloy is formed after it is naturally cooled. The primary alloy is then homogenized and annealed under vacuum conditions to obtain an aluminum-scandium alloy. On the one hand, the annealing treatment eliminates the residual internal stress of the primary alloy, and eliminates the thermal stress and mechanical stress generated during the casting and cooling process. On the other hand, the heating and slow cooling during the annealing process promote the recrystallization of the grains, thereby obtaining a finer grain size, making the microstructure of the material more uniform, reducing the microscopic defects of the material, and improving the strength and toughness of the material. The aluminum-scandium alloy prepared by the present invention has a low oxygen content, high density, fine grains, uniform structure, and good processing performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 These are typical characteristics of the microstructure of the aluminum-scandium alloy prepared in Example 1 of the present invention.

[0024] Figure 2 These are typical characteristics of the microstructure of the aluminum-scandium alloy prepared in Example 2 of the present invention.

[0025] Figure 3 This is an element scanning electron microscope image of the aluminum-scandium alloy prepared in Example 1 of the present invention.

[0026] Figure 4 This is an element scanning electron microscope image of the aluminum-scandium alloy prepared in Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The following test methods and detection methods, unless otherwise specified, are conventional methods; the reagents and raw materials, unless otherwise specified, are commercially available.

[0028] The technical solution of the present invention is described in detail below.

[0029] The present invention first provides a method for preparing an aluminum-scandium alloy, comprising the following steps:

[0030] In an inert gas, metal scandium particles and metal aluminum particles are subjected to multiple vacuum arc melting at 1300° C. to 1500° C. to alloy and obtain an aluminum-scandium alloy ingot.

[0031] The aluminum-scandium alloy ingot is melted by vacuum induction heating to obtain an alloy melt, the alloy melt is spray-casted, cooled and solidified to obtain a primary alloy, and the primary alloy is annealed under vacuum conditions at 200° C. to 800° C. to eliminate residual internal stress of the primary alloy to obtain an aluminum-scandium alloy.

[0032] As a preferred embodiment, in the aluminum-scandium alloy, the atomic content of metal scandium is 10% to 50%, and the atomic content of metal aluminum is 50% to 90%, totaling 100%. For the aluminum-scandium alloy target, the aluminum nitrogen scandium film manufactured by the reactive sputtering deposition method has excellent piezoelectric properties. As the scandium content increases, the piezoelectric constant and the electromechanical coupling coefficient increase linearly. In short, the higher the scandium content within a certain range, the higher the performance of the film finally manufactured by the aluminum-scandium alloy target.

[0033] As a preferred embodiment, the vacuum arc melting is carried out by using a program-controlled current, and the program-controlled current is specifically:

[0034] Current increase procedure: from 0A, increase by 10A~20A at a time and maintain for 1min~3min, increase to 90A~180A.

[0035] Current reduction procedure: from 90A~180A, reduce by 10A~15A at a time and keep it for 1min~2min, then reduce to 50A~90A; reduce by 6A~10A at a time and keep it for 2min~3min, then reduce to 50A; then reduce by 5A~8A at a time and keep it for 2min~3min, then reduce to 0A.

[0036] For the above-mentioned program-controlled current process, the program-increasing current can ensure the uniformity of the alloy composition. If the current is directly increased to a very high level, local overheating may occur, causing uneven melting and segregation. By gradually increasing the current, the melting process can be better controlled, so that scandium and aluminum are fully mixed to form a uniform alloy structure. Metallic scandium is very active and its melting point is much higher than that of aluminum. Direct melting with high current may cause scandium burnout. The program-increasing current can reduce the oxidation and volatilization of scandium, thereby increasing the actual recovery rate of scandium, which is particularly important for expensive scandium metal. Rapidly increasing the current may cause thermal stress in the melting furnace, which may damage the furnace lining or cause cracks inside the alloy. The program-increasing current can reduce this risk and ensure the safety and stability of the melting process. If the current is increased by 5A or 25A each time, it may cause inaccurate temperature control during the melting process, which will affect the microstructure and properties of the alloy. Smaller current increases may not be enough to maintain uniform melting and mixing, while larger increases may cause local overheating and burnout. Therefore, choosing the right current ramp is crucial to ensure alloy quality. The current ramp down process is equally important and needs to match the current ramp up process to ensure uniformity and reduce thermal stress during solidification. Ramp down too quickly may cause cracks or uneven microstructures inside the alloy, while ramp down too slowly may extend the melting cycle and increase production costs.

[0037] As a preferred embodiment, the multiple vacuum arc melting is 4 to 8 times, and the time of each vacuum arc melting is 60 minutes to 80 minutes. If the number of melting times is too small, less than 4 times, the purity and uniformity of the alloy will be insufficient. Since each melting process can remove gas and non-metallic inclusions in the alloy and reduce oxides and other impurities during the vacuum arc melting process, too few times may not be enough to completely purify the alloy, affecting its final performance, and increasing the number of melting times will increase production costs and time.

[0038] As a preferred embodiment, the vacuum induction heating is carried out using a vacuum induction melting furnace, the induction heating power supply is a 35KW IGBT high-frequency power supply, the preheating current of the vacuum induction melting furnace is 1A to 10A, the duration is 1min to 2min, the melting heating current is 5A to 30A, and the duration is 2min to 3min.

[0039] It should be noted that the preheating current is 1A to 10A and the duration is 1min to 2min. The preheating stage is to allow the charge to gradually adapt to the heating environment to avoid the charge or crucible from breaking due to excessive temperature difference. The preheating current is low, which can slowly increase the temperature and reduce thermal stress. Appropriate preheating time helps to remove moisture and volatile impurities on the surface of the charge and prevent excessive gas from being generated during high-temperature smelting.

[0040] The heating current for melting is 5A to 30A, and the duration is 2min to 3min; a higher current is required in the melting stage to melt the charge quickly. The choice of current depends on the nature of the charge and the capacity of the melting furnace. The appropriate current can ensure that the charge is fully melted while avoiding overheating that causes metal oxidation or volatilization. The choice of duration ensures that the charge is completely melted and the temperature of the molten pool is uniform. Too short a time may result in incomplete melting, while too long a time may cause overheating and metal burning.

[0041] If the heating current is too low or the duration is too short, the charge may not be fully melted, affecting the uniformity and purity of the alloy. If the heating current is too high or the duration is too long, it may cause excessive oxidation and burning of the metal, and may even damage the furnace lining or cause charge splashing.

[0042] In order to smoothly and evenly flow the prepared alloy melt into the mold for spray casting, the argon pressure difference is used during the spray casting, and the argon pressure difference is 0.0025MPa to 0.02MPa. Too small a pressure difference will cause the alloy melt to be unable to be completely sprayed into the mold below, and too high a pressure difference will cause the alloy melt sprayed into the mold below to contain pores.

[0043] It should be noted that the vacuum condition is 1×10 -3 pa~5×10 -3 pa.

[0044] As a preferred embodiment, the annealing time is 8h to 24h. If the annealing treatment is less than 8 hours at 200°C, the annealing effect will be insufficient, which is not enough to completely eliminate the stress inside the material and improve the microstructure. An annealing temperature below 200°C may be even less sufficient to eliminate the stress inside the material, and the mechanical properties of the material may not be significantly improved, and new stress may even be generated due to long-term low-temperature heating. If the treatment is performed at 800°C for more than 24 hours, the material will be overheated, causing the grains to grow excessively, thereby reducing the strength and toughness of the material. In addition, long-term high-temperature heating may cause oxidation or carbonization of the material surface, affecting the surface quality of the material. If the treatment is performed at a temperature higher than 800°C for 24 hours, an annealing temperature higher than 800°C may cause the material to overheat, the grains to be coarse, and the mechanical properties of the material to be affected. In addition, long-term heating at high temperatures may cause oxidation, decarburization or other chemical reactions of the material, affecting the purity and performance of the material.

[0045] The technical effects of the present invention are described below through specific embodiments and comparative examples.

[0046] Example 1

[0047] A method for preparing an aluminum-scandium alloy comprises the following steps:

[0048] Metal aluminum with a purity of 99.999% and metal scandium with a purity of 99.99% are selected as raw materials.

[0049] Put the aluminum-scandium raw materials with good proportions into the copper crucible in turn, slowly rotate the arc melting furnace chamber cover, and when the chamber cover reaches the top of the chamber, slowly close the chamber cover by controlling the hydraulic device, open the mechanical pump, rotate the pre-pumping valve, and wait for the pressure indication to reach -0.1Mpa, then close the pre-pumping valve, put in inert gas, and wait for the indication to reach -0.05Mpa, then open the pre-pumping valve again, repeat this step 3 times, turn on the compound vacuum gauge, and wait for the resistance unit indication to reach 8pa, then close the pre-pumping valve, open the front stage valve, and then open the high vacuum plug valve and start the molecular pump. When the resistance unit indication reaches 3×10 -3 pa, turn off the compound vacuum gauge, close the high vacuum plug valve, stop the molecular pump, close the front valve, and when the molecular pump reading is 0, turn off the mechanical pump, feed argon gas, and prepare for arc melting.

[0050] Adjust the position of the tungsten electrode and the molten material, place the tungsten electrode 3mm above the molten material, turn on the power of the argon arc welding machine, start arc melting, and increase the current at a rate of 20A, each time for 2 minutes. When the current reaches 130A, the arc stays on one side of the alloy melt for 5 minutes to ensure that the metal melt is fully alloyed.

[0051] After the metal melt is alloyed, the present invention adopts the method of controlling the current decreasing speed to control the speed of temperature change. The current starts to decrease from 130A, and is decreased by 15A at a time and maintained for 1 minute at a time until it decreases to 85A; when decreasing from 85A, it is decreased by 10A at a time and maintained for 2 minutes at a time until it decreases to 45A; when decreasing from 45A, it is decreased by 5A at a time and maintained for 2 minutes at a time until it decreases to 20A, and is maintained at 20A for 2 minutes, and then the flame is turned off.

[0052] After the high-temperature aluminum-scandium alloy melt is cooled to form an alloy ingot, the vacuum chamber is pre-evacuated to remove gas impurities, and then air is introduced into the chamber to take out the cooled aluminum-scandium alloy ingot.

[0053] The aluminum-scandium alloy ingot is further placed in a specially made quartz tube in a high vacuum chamber, the hatch is closed, the mechanical pump is started, the pre-pumping valve is slowly opened, and the pressure indicator of the chamber reaches -0.1MPa, and the gas distribution pipeline is cleaned 1 to 3 times. After cleaning the gas distribution pipeline, the fore valve is opened, the compound vacuum gauge is opened, and the vacuum degree is ≤8Pa, the pre-pumping valve is closed, the high vacuum gate valve is opened, and the molecular pump is started. When the vacuum degree is ≤5×10 -3 Pa, turn off the molecular pump, close the fore valve, turn off the mechanical pump, and introduce argon into the chamber to -0.05MPa.

[0054] After the gas distribution is completed, turn on the power supply of the vacuum induction melting machine box, and adjust the current knob to 1A~5A to allow the alloy to enter the preheating stage, which is maintained for 1min~2min. After the preheating is completed, adjust the current knob to 5A~15A to allow the alloy to enter the heating and melting stage, which is maintained for 2min~3min. After the alloy is completely melted, at this time, turn on the jet switch, inject 0.0025MPa~0.02MPa of argon into the quartz pipe, and use the injection system to accurately control the injection of argon so that the alloy melt is smoothly injected into the mold and cooled to obtain a primary alloy. The aluminum-scandium alloy ingot is annealed at 470°C for 12h under vacuum conditions to obtain an aluminum-scandium alloy, in which the atomic content of metal scandium is 13at.%.

[0055] Example 2

[0056] A method for preparing an aluminum-scandium alloy comprises the following steps:

[0057] Metal aluminum with a purity of 99.999% and metal scandium with a purity of 99.99% are selected as raw materials.

[0058] Put the aluminum-scandium raw materials with good proportions into the copper crucible in turn, slowly rotate the arc melting furnace chamber cover, and when the chamber cover reaches the top of the chamber, slowly close the chamber cover by controlling the hydraulic device, open the mechanical pump, rotate the pre-pumping valve, and wait for the pressure indication to reach -0.1Mpa, then close the pre-pumping valve, put in inert gas, and wait for the indication to reach -0.05Mpa, then open the pre-pumping valve again, repeat this step 3 times, turn on the compound vacuum gauge, and wait for the resistance unit indication to reach 8pa, then close the pre-pumping valve, open the front stage valve, and then open the high vacuum plug valve and start the molecular pump. When the resistance unit indication reaches 3×10 -3 pa, turn off the compound vacuum gauge, close the high vacuum plug valve, stop the molecular pump, close the front valve, and when the molecular pump reading is 0, turn off the mechanical pump, feed argon gas, and prepare for arc melting.

[0059] Adjust the position of the tungsten electrode and the molten material, place the tungsten electrode 3mm above the molten material, turn on the power of the argon arc welding machine, start arc melting, and increase the current at a rate of 20A, each time for 2 minutes. When the current reaches 180A, the arc stays on one side of the alloy melt for 5 minutes to ensure that the metal melt is fully alloyed.

[0060] After the metal melt is alloyed, the present invention adopts the method of controlling the current decreasing speed to control the speed of temperature change. The current starts to decrease from 180A, and is decreased by 15A at a time and maintained for 1 minute at a time until it decreases to 75A; when decreasing from 75A, it is decreased by 10A at a time and maintained for 2 minutes at a time until it decreases to 45A; when decreasing from 45A, it is decreased by 5A at a time and maintained for 2 minutes at a time until it decreases to 20A, and is maintained at 20A for 2 minutes, and then the flame is turned off.

[0061] After the high-temperature aluminum-scandium alloy melt is cooled to form an alloy ingot, the vacuum chamber is pre-evacuated to remove gas impurities, and then air is introduced into the chamber to take out the cooled aluminum-scandium alloy ingot.

[0062] The aluminum-scandium alloy ingot is further placed in a specially made quartz tube in a high vacuum chamber, the hatch is closed, the mechanical pump is started, the pre-pumping valve is slowly opened, and the pressure indicator of the chamber reaches -0.1MPa, and the gas distribution pipeline is cleaned 1 to 3 times. After cleaning the gas distribution pipeline, the fore valve is opened, the compound vacuum gauge is opened, and the vacuum degree is ≤8Pa, the pre-pumping valve is closed, the high vacuum gate valve is opened, and the molecular pump is started. When the vacuum degree is ≤5×10 -3 Pa, turn off the molecular pump, close the fore valve, turn off the mechanical pump, and introduce argon into the chamber to -0.05MPa.

[0063] After the gas distribution is completed, turn on the power of the vacuum induction melting machine box, and adjust the current knob to 5A~10A to allow the alloy to enter the preheating stage, which is maintained for 1min~2min. After the preheating is completed, adjust the current knob to 10A~30A to allow the alloy to enter the heating and melting stage, which is maintained for 2min~3min. After the alloy is completely melted, at this time, turn on the jet switch, inject 0.0025MPa~0.02MPa of argon into the quartz pipe, and use the injection system to accurately control the injection of argon so that the alloy melt is smoothly injected into the mold and cooled to obtain a primary alloy. The aluminum-scandium alloy ingot is annealed at 650℃ for 10h under vacuum conditions to obtain an aluminum-scandium alloy, in which the atomic content of metal scandium is 30at.%.

[0064] Example 3

[0065] A method for preparing an aluminum-scandium alloy comprises the following steps:

[0066] Metal aluminum with a purity of 99.999% and metal scandium with a purity of 99.99% are selected as raw materials.

[0067] Put the aluminum-scandium raw materials with good proportions into the copper crucible in turn, slowly rotate the arc melting furnace chamber cover, and when the chamber cover reaches the top of the chamber, slowly close the chamber cover by controlling the hydraulic device, open the mechanical pump, rotate the pre-pumping valve, and wait for the pressure indication to reach -0.1Mpa, then close the pre-pumping valve, put in inert gas, and wait for the indication to reach -0.05Mpa, then open the pre-pumping valve again, repeat this step 3 times, turn on the compound vacuum gauge, and wait for the resistance unit indication to reach 8pa, then close the pre-pumping valve, open the front stage valve, and then open the high vacuum plug valve and start the molecular pump. When the resistance unit indication reaches 3×10 -3 pa, turn off the compound vacuum gauge, close the high vacuum plug valve, stop the molecular pump, close the front valve, and when the molecular pump reading is 0, turn off the mechanical pump, feed argon gas, and prepare for arc melting.

[0068] Adjust the position of the tungsten electrode and the molten material, place the tungsten electrode 3mm above the molten material, turn on the power of the argon arc welding machine, start arc melting, and increase the current at a rate of 20A, each time for 2 minutes. When the current reaches 160A, the arc stays on one side of the alloy melt for 5 minutes to ensure that the metal melt is fully alloyed.

[0069] After the metal melt is alloyed, the present invention adopts the method of controlling the current decreasing speed to control the speed of temperature change. The current starts to decrease from 160A, and is decreased by 15A at a time and maintained for 1 minute at a time until it decreases to 85A; when decreasing from 85A, it is decreased by 10A at a time and maintained for 2 minutes at a time until it decreases to 45A; when decreasing from 45A, it is decreased by 5A at a time and maintained for 2 minutes at a time until it decreases to 20A, and is maintained at 20A for 2 minutes, and then the flame is turned off.

[0070] After the high-temperature aluminum-scandium alloy melt is cooled to form an alloy ingot, the vacuum chamber is pre-evacuated to remove gas impurities, and then air is introduced into the chamber to take out the cooled aluminum-scandium alloy ingot.

[0071] The aluminum-scandium alloy ingot is further placed in a specially made quartz tube in a high vacuum chamber, the hatch is closed, the mechanical pump is started, the pre-pumping valve is slowly opened, and the pressure indicator of the chamber reaches -0.1MPa, and the gas distribution pipeline is cleaned 1 to 3 times. After cleaning the gas distribution pipeline, the fore valve is opened, the compound vacuum gauge is opened, and the vacuum degree is ≤8Pa, the pre-pumping valve is closed, the high vacuum gate valve is opened, and the molecular pump is started. When the vacuum degree is ≤5×10 -3 Pa, turn off the molecular pump, close the fore valve, turn off the mechanical pump, and introduce argon into the chamber to -0.05MPa.

[0072] After the gas distribution is completed, turn on the power supply of the vacuum induction melting machine box, and adjust the current knob to 3A~7A to make the alloy enter the preheating stage, which is maintained for 1min~2min. After the preheating is completed, adjust the current knob to 7A~20A to make the alloy enter the heating and melting stage, which is maintained for 2min~3min. After the alloy is completely melted, at this time, turn on the jet switch, inject 0.0025MPa~0.02MPa of argon into the quartz pipe, use the injection system to accurately control the injection of argon, so that the alloy melt is smoothly injected into the mold, cooled, and a primary alloy is obtained. The primary alloy is annealed at 550℃ for 12h under vacuum conditions to obtain an aluminum-scandium alloy, in which the atomic content of metal scandium is 50at.%.

[0073] In order to further illustrate the technical effect of the present invention, the present invention also sets a comparative example, which is as follows:

[0074] Comparative Example 1

[0075] A method for preparing an aluminum-scandium alloy comprises the following steps:

[0076] Metal aluminum with a purity of 99.999% and metal scandium with a purity of 99.99% are selected as raw materials.

[0077] Put the aluminum-scandium raw materials with good proportions into the copper crucible in turn, slowly rotate the arc melting furnace chamber cover, and when the chamber cover reaches the top of the chamber, slowly close the chamber cover by controlling the hydraulic device, open the mechanical pump, rotate the pre-pumping valve, and wait for the pressure indication to reach -0.1Mpa, then close the pre-pumping valve, put in inert gas, and wait for the indication to reach -0.05Mpa, then open the pre-pumping valve again, repeat this step 3 times, open the compound vacuum gauge, wait for the resistance unit indication to reach 8pa, close the pre-pumping valve, open the fore valve, then open the high vacuum gate valve, and start the molecular pump. When the resistance unit indication reaches 3×10-3Pa, close the compound vacuum gauge, close the high vacuum gate valve, stop the molecular pump, close the fore valve, and when the molecular pump indication reaches 0, close the mechanical pump, send in argon gas, and prepare for arc melting.

[0078] Adjust the position of the tungsten electrode and the molten material, place the tungsten electrode 3mm above the molten material, turn on the power of the argon arc welding machine, start arc melting, and increase the current at a rate of 20A, each time for 2 minutes. When the current reaches 130A, the arc stays on one side of the alloy melt for 5 minutes to ensure that the metal melt is fully alloyed.

[0079] After the metal melt is alloyed, the present invention adopts the method of controlling the current decreasing speed to control the speed of temperature change. The current starts to decrease from 130A, and is decreased by 15A at a time and maintained for 1 minute at a time until it decreases to 85A; when decreasing from 85A, it is decreased by 10A at a time and maintained for 2 minutes at a time until it decreases to 45A; when decreasing from 45A, it is decreased by 5A at a time and maintained for 2 minutes at a time until it decreases to 20A, and is maintained at 20A for 2 minutes, and then the flame is turned off.

[0080] After the high-temperature aluminum-scandium alloy melt is cooled to form an alloy ingot, the vacuum chamber is pre-evacuated to remove gas impurities, and then air is introduced into the chamber to take out the cooled aluminum-scandium alloy, in which the atomic content of metal scandium is 13at.%.

[0081] The properties of the aluminum-scandium alloys prepared in the above examples and comparative examples were tested, and the results are as follows:

[0082] Figure 1 , Figure 2 The typical microstructural characteristics of the aluminum-scandium alloys prepared in Example 1 and Example 2 respectively. Figure 3 , Figure 4The element scanning electron microscope images of the aluminum-scandium alloy prepared in Example 1 and Comparative Example 1 of the present invention are respectively shown. By observing the typical characteristics of the microstructure of the aluminum-scandium alloy prepared in the present invention and by comparative analysis, it is found that the aluminum-scandium alloy prepared in the present invention has a fine microstructure, uniform chemical composition and no significant defects. Comparative Example 1 has made adjustments to the preparation process, reducing the steps of induction melting and spray casting. It can be seen that the size of the alloy phase and the distribution of elements have been affected. The size of the alloy phase has become larger, and the uniformity of the composition distribution of the two elements Al and Sc has been reduced; ultimately, it will have an adverse effect on the sputtering rate and uniformity of the target material, resulting in a decrease in the quality and performance of the film.

[0083] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for preparing an aluminum-scandium alloy, characterized in that: The following steps are involved: In an inert gas, the metal scandium particles and the metal aluminum particles are subjected to multiple vacuum arc melting at 1300° C. to 1500° C. to alloy and obtain an aluminum-scandium alloy ingot; The aluminum-scandium alloy ingot is melted by vacuum induction heating to obtain an alloy melt, the alloy melt is spray-casted by argon pressure difference, cooled and solidified to obtain a primary alloy, and the primary alloy is annealed under vacuum conditions at 200°C to 800°C to eliminate residual internal stress of the primary alloy to obtain an aluminum-scandium alloy.

2. The preparation method according to claim 1, characterized in that: In the aluminum-scandium alloy, the atomic content of metal scandium is 10% to 50%, and the atomic content of metal aluminum is 50% to 90%, which is 100% in total.

3. The preparation method according to claim 1, characterized in that: The vacuum arc melting is carried out by program-controlled current, firstly the current is increased to perform arc melting and alloying, and then the current is decreased to obtain an aluminum-scandium alloy ingot; the program-controlled current is specifically: Current increase procedure: from 0A, increase by 10A to 20A at a time and maintain for 1min to 3min, and then increase to 90A to 180A; Current reduction procedure: from 90A~180A, reduce by 10A~15A at a time and keep it for 1min~2min, then reduce to 50A~90A; reduce by 6A~10A at a time and keep it for 2min~3min, then reduce to 50A; then reduce by 5A~8A at a time and keep it for 2min~3min, then reduce to 0A.

4. The preparation method according to claim 1, characterized in that: The multiple vacuum arc melting processes are 4 to 8 times, and the duration of each vacuum arc melting process is 60 to 80 minutes.

5. The preparation method according to claim 1, characterized in that: The vacuum induction heating is performed by a vacuum induction melting furnace, the preheating current of the vacuum induction melting furnace is 1A-10A, the duration is 1min-2min, the heating current of the melting is 5A-30A, the duration is 2min-3min.

6. The preparation method according to claim 1, characterized in that: The spray casting is performed by utilizing the argon pressure difference, and the argon pressure difference is 0.0025MPa to 0.02MPa.

7. The preparation method according to claim 1, characterized in that: The vacuum condition is 1×10 -3 pa~5×10 - 3 pa.

8. The preparation method according to claim 1, characterized in that: The annealing treatment time is 8h to 24h.

9. An aluminum-scandium alloy prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the aluminum-scandium alloy according to claim 9 in preparing an aluminum-scandium nitride piezoelectric film or as a sputtering target for a thin film bulk acoustic wave resonator or a bulk acoustic wave device.

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