Method for manufacturing scandium-containing alloy

Abstract

To provide a method for manufacturing a scandium-containing alloy containing at least one metal selected from aluminum or magnesium, by reducing a scandium compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride, in a way that is inexpensive, safe, environmentally friendly, and energy-efficient.SOLUTION: A method according to the present disclosure for manufacturing a scandium-containing alloy includes: a preparation step of preparing a composite powder including a scandium compound powder comprising at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride, and a metal powder comprising at least one of aluminum and magnesium, or both aluminum and magnesium; and a heating step of heating the composite powder at 500°C or higher in a vacuum atmosphere or an inert gas atmosphere.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for manufacturing scandium-containing alloys, for example, a technology for manufacturing aluminum-scandium alloys, magnesium-scandium alloys, or aluminum-magnesium-scandium alloys at low cost and with lower energy.

Background Art

[0002] Regarding scandium, alloys obtained by adding a trace amount of scandium to lightweight aluminum with higher strength than duralumin were used for military applications such as the Soviet Union's MIG29 during the Cold War. In addition, scandium alloys are for civilian use and their utilization as lightweight and high-strength structural materials such as the frames of high-end bicycles is expanding. Scandium alloys have significantly improved mechanical properties and weldability compared to duralumin and have high industrial utility value.

[0003] In addition, scandium has attracted attention as a new proton conductor additive in solid oxide fuel cells (SOFCs) that generate electricity from natural gas, and it is expected that inexpensive electricity can be obtained using solid oxide fuel cells.

[0004] Scandium is a main component of crystals for gadolinium-scandium-gallium garnet (GSGG) lasers, which have an energy intensity more than three times that of yttrium aluminum garnet (YAG), a common laser material. In addition, scandium is used for studio lighting in photography, movies, and television stations because a wide emission spectrum close to sunlight can be obtained.

[0005] Furthermore, a composite nitride thin film in which scandium is dissolved in aluminum nitride exhibits piezoelectricity more than five times that of aluminum nitride and has been found to show the highest value among nitrides. Since it can improve piezoelectric performance and achieve heat resistance for the evolution of communication systems such as 5G, it is used as a BAW high-frequency filter for mobile communication. In addition, a composite nitride thin film in which scandium is dissolved in aluminum nitride has the performance of a piezoelectric element whose crystal structure does not change even when heated to 500 °C, and is expected to be used as a high-temperature pressure sensor that does not contain harmful elements such as lead (PZT).

[0006] Therefore, productization is progressing in applications such as radio filters for 5G ultra-high-speed communication, control piezoelectric sensors for ultra-low emission turbines, high-performance ultrasonic sensors for supporting autonomous driving, ultrasonic probes for medical devices, or MEMS (Micro Electro Mechanical Systems), and the key material is scandium.

[0007] However, although scandium oxide is produced worldwide, the refining of reducing scandium oxide to metallic scandium has a high environmental impact, a high energy load, and concerns about safety. Moreover, the refining is only carried out in some countries such as China. For this reason, metallic scandium is very expensive and its use is limited.

[0008] The manufacturing method of metallic scandium is to fluorinate scandium oxide, which is thermodynamically extremely stable as a raw material, to form scandium fluoride that is easy to reduce. At this time, it is reduced at a high temperature of 1600 °C using metallic calcium as a reducing agent (see, for example, Non-Patent Document 1). The fluorination process has a large environmental impact. In addition, there are safety issues due to the use of metallic calcium. Furthermore, since a high temperature of 1600 °C is required, the energy load is high, the countries that can manufacture it are limited, and the price soars.

[0009] Scandium oxide is a thermodynamically very stable oxide and is not reduced as it is. Therefore, it is usually reduced according to (Chemical Formula 1) and (Chemical Formula 2). (Equation 1) Sc2O3+ 6NH4HF2→ 2ScF3+ 6NH4F + 3H2O (Equation 2) 2ScF3+ 3Ca → 2Sc + 3CaF2 There is a disclosure of a technology developed from this technology (see, for example, Patent Document 1). In Patent Document 1, scandium oxide and scandium fluoride are placed in a sealed container together with aluminum or magnesium, and further, metallic calcium is heated to 1000 °C in the sealed container to generate vapor. The scandium oxide or scandium fluoride is reduced by this metallic calcium reduction vapor to achieve alloying with aluminum or magnesium.

[0010] In addition, a method of producing pellets by mixing aluminum and scandium oxide and then putting them into a molten metal of aluminum or magnesium to form an alloy has been considered (see, for example, Patent Document 2). The technology of Patent Document 2 involves mixing a rare earth oxide such as scandium oxide with a light metal such as aluminum to form pellets. Further, aluminum or magnesium is melted, and the pellets are put into the molten metal for a reduction reaction.

[0011] In addition, aluminum and scandium halide are subjected to thermal reduction at 800 °C to 1000 °C using a metal reducing agent such as Li, Ca, or Mg, and further, lithium fluoride or calcium chloride is added as a flux. The melt is slowly cooled to form an AlSc alloy-enriched portion. As a result, a scandium concentration of 7 wt% or more is obtained, and there is a technology of cutting out the enriched portion for use (see, for example, Patent Document 3).

[0012] In addition, there is a technology of heating scandium fluoride, aluminum fluoride, sodium fluoride, and scandium oxide to 1000 °C to produce an AlSc alloy by molten salt electrolysis (see, for example, Patent Document 4).

[0013] In addition, in molten salt electrolysis, there is a method of reducing a rare earth oxide or fluoride in molten aluminum to perform alloying with high efficiency (see, for example, Patent Document 5).

[0014] In addition, a method for producing an AlSc alloy is described in which calcium or magnesium, which is a reducing agent, is placed in a container containing scandium oxide and aluminum, and the ceramics are heated with microwaves to vaporize the reducing agent and reduce the scandium oxide (see, for example, Patent Document 6). This production method shows a reduction rate of 69.8% at a low temperature of 660°C. (See Non-Patent Document 2.)

[0015] Furthermore, the reduction of scandium oxide using microwaves is the same as in Patent Document 6. However, in order to improve the problematic productivity, a technique is provided in which the microwave for heating the reducing metal to form a plasma and the microwave for heating the members to be alloyed such as scandium oxide and aluminum are separated and performed with high efficiency (see, for example, Patent Document 7).

Prior Art Documents

Patent Documents

[0016]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Patent Document 7

Non-Patent Documents

[0017]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0018] However, in the technique described in Patent Document 1, it is necessary to heat to a high temperature of 1000°C to produce metallic calcium vapor, and furthermore, it is necessary to use a pressure-resistant container. Although the reduction of scandium oxide and scandium fluoride can be achieved, due to the use of high temperature, high energy is required, and due to the use of a pressure-resistant container, there are also problems in terms of safety. In addition, the produced alloy also contains calcium as a reducing agent, and the process for removing it increases, making the process complicated.

[0019] Also, in the technique described in Patent Document 2, it is necessary to make the ratio of aluminum to scandium oxide greater than about 30. Furthermore, there is a problem that the yield is reduced due to oxidation from the molten atmosphere.

[0020] Also, in the technique described in Patent Document 3, the temperature is high, fluxes and metal reducing agents are mixed in, and it is difficult to remove them. Furthermore, even if enrichment is carried out to extract the site, it takes a lot of man-hours and the yield is low.

[0021] Also, in the technique described in Patent Document 4, there are problems in terms of safety because a molten salt using fluoride is made. Furthermore, since electrolysis is carried out at a high temperature of 1000°C, a lot of energy is required. Naturally, the mixing of impurities cannot be avoided, and it is difficult to achieve high purity.

[0022] In addition, the technique described in Patent Document 5 is a method in which a Sc-containing alloy can be obtained with high efficiency by performing the process at 700°C or higher and 1000°C or lower, which is the melting temperature of aluminum. However, since it is molten salt electrolysis, there are difficulties in terms of safety and energy efficiency. Furthermore, in molten salt electrolysis, rare earth oxides or fluorides are reduced and alloyed in aluminum. Although graphite and iron are exemplified for the cathode, since iron reacts with aluminum to form impurities, graphite is mainly used. Therefore, since gases such as carbon tetrafluoride, carbon monoxide, and carbon dioxide are generated on the anode surface during electrolysis, it is recommended to provide a gas vent. According to this method, aluminum is melted at 850°C, and a current of 50 A is passed through a graphite electrode for electrodeposition. Although the exemplified one is a yttrium-aluminum alloy, generation of harmful gases cannot be avoided, and since electrodeposition takes time, the necessary energy also tends to increase.

[0023] In addition, the technique described in Patent Document 6 is a very simple and effective reduction method. However, due to the mixing of reducing metals, it takes man-hours to achieve high purity. Furthermore, industrially, it is necessary to improve the reduction rate, and a decrease in the reduction rate will result in an increase in cost. Furthermore, since microwaves are used, the size and shape of the container are likely to be restricted, making mass production difficult.

[0024] In addition, the technique described in Patent Document 7 is considered to improve productivity and contribute to cost reduction compared to the technique of Patent Document 6. However, although it may be sufficient for about several kilograms, large-scale equipment is required for production on the order of several hundred kilograms or tons, and the cost of the AlSc alloy may increase.

[0025] An object of the present disclosure is to provide a method for producing a Sc-containing alloy containing at least one of aluminum and magnesium by reducing a Sc compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride in an inexpensive, safe, low environmental impact, and energy-saving manner.

Means for Solving the Problems

[0026] In order to solve the above problems, the present inventors have conducted intensive studies. As a result, without requiring high temperature and high pressure, with low energy, ensuring high safety by not using a highly active reducing metal, and further solving the difficult problem of a technology that can reduce man-hours, be inexpensive, and be mass-produced, they have found a method for producing metallic scandium from a scandium compound containing scandium oxide, which has been conventionally considered thermodynamically impossible, and producing a scandium-containing alloy having aluminum and / or magnesium as a base material with high purity, thus completing the present invention. That is, the method for producing a scandium-containing alloy according to the present invention includes a preparation step of preparing a composite powder including a powder of a scandium compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride, and a metal powder containing at least one of aluminum or magnesium, or both aluminum and magnesium, and a heating step of heating the composite powder to 500° C. or higher in a vacuum atmosphere or an inert gas atmosphere.

[0027] The method for producing a scandium-containing alloy according to the present invention further includes a molding step of putting the composite powder into a mold and a forming step of applying pressure to the composite powder to form a compact, and the heating step is preferably a step of heating the composite powder formed into the compact. Since the powder of the scandium compound and the metal powder come into contact more, the alloying reaction can be further promoted.

[0028] The method for producing a scandium-containing alloy according to the present invention further includes a molding step of putting the composite powder into a mold, and the heating step is preferably a step of heating the composite powder put into the mold under pressure in a vacuum atmosphere or an inert gas atmosphere. By heating under pressure in an atmosphere with less oxygen, the powder of the scandium compound and the metal powder come into contact more, so that the alloying reaction can be further promoted.

[0029] In the method for manufacturing a scandium-containing alloy according to the present invention, it further has a mechanical alloying step A of mechanically alloying the composite powder prepared in the preparation step, and it is preferable that the mold filling step is a step of charging the composite powder mechanically alloyed as the composite powder into the molding die. The powders of the scandium compound and the metal powder are refined, the powder of the scandium compound is dispersed with respect to the metal powder, and the alloying reaction can be further promoted even at a low temperature.

[0030] In the method for manufacturing a scandium-containing alloy according to the present invention, the composite powder prepared in the preparation step further contains at least one selected from the group consisting of carboxylic acid, ascorbic acid, and higher fatty acid as an auxiliary agent, and it further has a mechanical alloying step B of mechanically alloying the composite powder containing the auxiliary agent prepared in the preparation step, and it is preferable that the mold filling step is a step of charging the composite powder mechanically alloyed as the composite powder into the molding die. The formation of oxides on the surface of the metal powder is suppressed, the aggregation of the powders of the scandium compound or the metal powders is suppressed, the contact area is improved, and the alloying reaction can be further promoted even at a low temperature.

[0031] In the method for manufacturing a scandium-containing alloy according to the present invention, it is preferable that the particle size of the powder of the scandium compound is 1000 μm or less. By making the particle size of the powder of the scandium compound finer, the alloying reaction can be further promoted.

[0032] In the method for manufacturing a scandium-containing alloy according to the present invention, it is preferable that the particle size of the metal powder is 2000 μm or less. By making the particle size of the metal powder finer, the alloying reaction can be further promoted.

[0033] In the method for manufacturing a scandium-containing alloy according to the present invention, in the molding step, it is preferable that the pressure applied to the composite powder is 5 MPa or more. Since the powders of the scandium compound and the metal powder come into contact more, the alloying reaction can be further promoted.

[0034] In the method for producing a scandium-containing alloy according to the present invention, in the heating step, the pressure applied to the composite powder is preferably 5 MPa or more. Since the powder of the scandium compound and the metal powder come into contact more, the alloying reaction can be further promoted.

[0035] In the method for producing a scandium-containing alloy according to the present invention, the scandium-containing alloy obtained through the heating step includes an aluminum-scandium-containing alloy, and the aluminum-scandium alloy in the aluminum-scandium-containing alloy includes a form containing at least one selected from the group consisting of an aluminum-scandium solid solution alloy, an Al3Sc intermetallic compound, an Al2Sc intermetallic compound, and an AlSc intermetallic compound.

[0036] In the method for producing a scandium-containing alloy according to the present invention, the scandium-containing alloy obtained through the heating step includes a magnesium-scandium-containing alloy, and the magnesium-scandium alloy in the magnesium-scandium-containing alloy includes a form containing at least one selected from the group consisting of a magnesium-scandium solid solution alloy and an MgSc intermetallic compound.

[0037] In the method for producing a scandium-containing alloy according to the present invention, it is preferable to further have a purification step of melting the scandium-containing alloy obtained through the heating step and either aluminum or magnesium, or both aluminum and magnesium, in a vacuum atmosphere or an inert gas atmosphere to remove impurities. A higher-purity scandium-containing alloy can be obtained.

[0038] In the method for producing a scandium-containing alloy according to the present invention, the impurities include a form containing at least one selected from the group consisting of aluminum oxide, magnesium oxide, and scandium oxide.

Advantages of the Invention

[0039] According to the present disclosure, a scandium compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride is reduced inexpensively, safely, with low environmental impact, and energy-saving to provide a method for producing a scandium-containing alloy containing at least one of aluminum and magnesium metals.

Brief Description of Drawings

[0040]

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Figure 5B

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Figure 10

Mode for Carrying Out the Invention

[0041] Hereinafter, embodiments of the present invention will be shown and described in detail, but the present invention is not construed as being limited to these descriptions. As long as the effects of the present invention are achieved, the embodiments may be variously modified.

[0042] The method for producing a scandium-containing alloy according to this embodiment includes a preparation step of preparing a composite powder including a powder of a scandium compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride, and a metal powder containing at least one of aluminum or magnesium, or both aluminum and magnesium, and a heating step of heating the composite powder to 500 °C or higher in a vacuum atmosphere or an inert gas atmosphere. Hereinafter, each step will be described.

[0043] [Preparation Step] [Raw Materials] As a raw material, a composite powder containing scandium compound powder and metal powder is prepared. As the scandium compound powder, there are (1) scandium oxide powder, (2) scandium fluoride powder, (3) scandium chloride powder, (4) a combination of scandium oxide powder and scandium fluoride powder, (5) a combination of scandium oxide powder and scandium chloride powder, (6) a combination of scandium fluoride powder and scandium chloride powder, (7) a combination of scandium oxide powder, scandium fluoride powder and scandium chloride powder. As the metal powder, there are (1) aluminum powder, (2) magnesium powder, (3) a combination of aluminum powder and magnesium powder. The raw material is prepared by combining these powders, and the combined powder is referred to as "composite powder" in this embodiment. The composite powder is preferably a mixed powder. The particle size of the scandium compound powder is preferably 1000 μm or less, more preferably 800 μm or less, and even more preferably 100 μm or less. The lower limit of the particle size of the scandium compound powder is not particularly limited, but is preferably, for example, 1 μm or more. The volume-based D50 particle size of the scandium compound powder is preferably 10 to 500 μm, and more preferably 10 to 200 μm. The particle size of the metal powder is preferably 2000 μm or less, more preferably 1000 μm or less, and even more preferably 500 μm or less. The lower limit of the particle size of the metal powder is not particularly limited, but is preferably, for example, 10 μm or more. The volume-based D50 particle size of the metal powder is preferably 30 to 500 μm, and more preferably 30 to 200 μm. When the particle size becomes smaller, the mixing time can be shortened. To obtain a mixed powder, various powders are put into a mixing device, and the atmosphere in the mixing tank is preferably filled with an inert gas such as argon, and mixing is performed in a state where oxygen is discharged.

[0044] In any composition ratio of the composite powder, scandium compounds are reduced. For example, scandium oxide is reduced to metallic scandium, which then alloyizes with aluminum. At this time, as shown in Fig. 1, since scandium does not dissolve well in the aluminum side, an intermetallic compound Al3Sc is formed. Therefore, it is preferable to prepare the scandium compound to be blended at a molar ratio of 3:1 with metallic aluminum and metallic scandium. Also, the aluminum and scandium compound to be blended may be prepared within the range of a molar ratio of metallic aluminum to metallic scandium in the range of 10:1 to 1:1. Specifically, the molar ratios are 9:1, 5:1, 2:1, 1:1, etc.

[0045] (Auxiliary agent) The composite powder preferably further contains at least one selected from the group consisting of carboxylic acid, ascorbic acid, and higher fatty acid as an auxiliary agent. The auxiliary agents are (1) carboxylic acid, (2) ascorbic acid, (3) higher fatty acid, (4) a combination of carboxylic acid and ascorbic acid, (5) a combination of carboxylic acid and higher fatty acid, (6) a combination of ascorbic acid and higher fatty acid, (7) a combination of carboxylic acid, ascorbic acid, and higher fatty acid. By adding these auxiliary agents to the composite powder, a composite powder containing the auxiliary agent is obtained. The composite powder containing the auxiliary agent is preferably in a mixed state of the auxiliary agent and the composite powder. The blending amount of the auxiliary agent with respect to 100 parts by mass of the composite powder is preferably 1 part by mass or less. The lower limit of the blending amount of the auxiliary agent is preferably 0.1 part by mass. In order to improve the yield, it is preferable to add the auxiliary agent. Examples of the auxiliary agent include alcohol, hydrocarbon, carboxylic acid, higher fatty acid, etc. Examples of alcohol include methanol. Examples of hydrocarbon include heptane. Examples of carboxylic acid include acetic acid, oxalic acid, benzoic acid, etc. Examples of higher fatty acid include stearic acid, oleic acid, etc. The factor that reduces the yield is the strong oxide film present on the surface of the aluminum or magnesium metal raw material, which inhibits the reaction with the scandium compound. Therefore, the above-mentioned auxiliary agent is added to act as an auxiliary agent for removing the surface oxide film and improve the yield.

[0046] [Mechanical alloying process A · Mechanical alloying process B] It is preferable to further have a mechanical alloying process A for mechanically alloying the composite powder prepared in the preparation process. Alternatively, it is preferable to further have a mechanical alloying process B for mechanically alloying the composite powder containing the auxiliary agent prepared in the preparation process. When mixing a powder of a scandium compound such as scandium oxide with aluminum powder and / or magnesium powder as the base material, by adding a process of mechanical alloying (mechanical alloying) with high energy, it becomes possible to reduce the scandium compound at a lower temperature. Mechanical alloying is a method of obtaining an alloy by putting a composite powder or a composite powder containing an auxiliary agent into a ball mill together with a grinding medium such as ceramics and rotating it so that the grinding medium repeatedly pressurizes and spreads the composite powder or the composite powder containing the auxiliary agent. In order to obtain a mechanically alloyed composite powder, various powders are put into a mixing device, and the atmosphere in the mixing tank is preferably filled with an inert gas such as argon, and oxygen is discharged, and then mixed. Furthermore, as a mixing member, ceramic balls such as alumina and zirconia are put in and sealed. When applying a large amount of energy in a short time, a planetary ball mill, an attritor, a bead mill, etc. are used. In order to obtain a composite powder obtained by mechanically alloying a composite powder containing an auxiliary agent, various powders are put into a mixing device together with the auxiliary agent, and the same operation as the operation of mechanically alloying the composite powder not containing the above auxiliary agent is performed. A mixed composite powder can be obtained by performing mechanical alloying for 10 minutes or more.

[0047] [Molding process] The molding process is a process of putting the composite powder or the composite powder containing the auxiliary agent into a molding die. In the mechanical alloying process A or the mechanical alloying process B, when a mechanically alloyed composite powder is obtained, the molding process is a process of putting the mechanically alloyed composite powder into a molding die. Examples of the molding die include a die for press molding, a carbon die, and a rubber die for cold isostatic pressing.

[0048] [Forming process] In this embodiment, after the die filling step, there may be a step of applying pressure to the composite powder or the mechanically alloyed composite powder to form a compact. In this case, a heating step is performed as a subsequent step to the forming step. In the forming step, the pressure applied to the composite powder or the mechanically alloyed composite powder is preferably 5 MPa or more, more preferably 30 MPa or more, and even more preferably 50 MPa or more.

[0049] [Heating Step] The heating step includes two methods: (1) Step A of heating the composite powder or the mechanically alloyed composite powder formed into a compact when passing through the die filling step and the forming step; and (2) Step B of heating the composite powder or the mechanically alloyed composite powder introduced into the mold under pressure in a vacuum atmosphere or an inert gas atmosphere without passing through the forming step after passing through the die filling step. In Step A, since the handling of the compact is easy, heat treatment can be performed in a heating furnace, a high-frequency furnace, etc. that can be adjusted to a vacuum atmosphere or an inert gas atmosphere. In Step B, heat and pressure treatment can be performed using a hot press, HIP, a spark plasma sintering machine, etc. that can be adjusted to a vacuum atmosphere or an inert gas atmosphere. The heating temperature is 500 °C or more, preferably 550 to 900 °C, and more preferably 600 to 750 °C. In Step B of the heating step, the pressure applied to the composite powder is preferably 5 MPa or more, and more preferably 30 MPa or more. The inert gas atmosphere is, for example, an argon atmosphere, a nitrogen atmosphere, etc. The vacuum atmosphere is, for example, 5 Pa or less.

[0050] [After Heating Step] The scandium-containing alloy obtained through the heating process includes an aluminum-scandium-containing alloy. The aluminum-scandium alloy in the aluminum-scandium-containing alloy includes at least one selected from the group consisting of an aluminum-scandium solid solution alloy, an Al3Sc intermetallic compound, an Al2Sc intermetallic compound, and an AlSc intermetallic compound. Further, the scandium-containing alloy obtained through the heating process includes a magnesium-scandium-containing alloy. The magnesium-scandium alloy in the magnesium-scandium-containing alloy includes at least one selected from the group consisting of a magnesium-scandium solid solution alloy and an MgSc intermetallic compound. Additionally, the scandium-containing alloy obtained through the heating process includes an aluminum-magnesium-scandium-containing alloy. The aluminum-magnesium-scandium alloy in the aluminum-magnesium-scandium-containing alloy includes at least one selected from the group consisting of an aluminum-scandium solid solution alloy, an Al3Sc intermetallic compound, an Al2Sc intermetallic compound, and an AlSc intermetallic compound, and at least one selected from the group consisting of a magnesium-scandium solid solution alloy and an MgSc intermetallic compound.

[0051] [Purification Process] The refining process is a process of melting a scandium-containing alloy obtained through a heating process with either aluminum or magnesium, or both aluminum and magnesium, in a vacuum atmosphere or an inert gas atmosphere to remove impurities. A higher-purity scandium-containing alloy can be obtained. Here, the impurities include at least one selected from the group consisting of aluminum oxide, magnesium oxide, and scandium oxide. The inert gas atmosphere is, for example, an argon atmosphere, a nitrogen atmosphere, etc. The vacuum atmosphere is, for example, 5 Pa or less. The melting temperature is, for example, 700 to 1450 °C. By this process, the impurities do not dissolve into the melt phase consisting of either aluminum or magnesium, or both aluminum and magnesium, and remain outside the melt phase. By removing the outer portion of the melt phase containing impurities after cooling, a high-purity scandium-containing alloy can be obtained. The method for removing impurities includes, for example, physical cutting, such as methods using a band saw or churning.

[0052] In the method for producing a scandium-containing alloy according to this embodiment, for example, the adjustment of the composition ratio of Al and Sc includes, in addition to adjusting the composite powder from the beginning so as to obtain the finally targeted composition ratio, once a scandium-containing alloy is produced, and then, the case of adjusting the concentration of the Al-Sc alloy with Al, and the case of adjusting the concentration of the Al-Sc alloy with Sc. Also, for example, the adjustment of the composition ratio of Mg and Sc includes, in addition to adjusting the composite powder so as to obtain the finally targeted composition ratio, once a scandium-containing alloy is produced, and then, the case of adjusting the concentration of the Mg-Sc alloy with Mg, and the case of adjusting the concentration of the Mg-Sc alloy with Sc. Further, for example, the adjustment of the composition ratio of Al, Mg, and Sc includes, in addition to adjusting the composite powder so as to obtain the finally targeted composition ratio, once a scandium-containing alloy is produced, and then, the case of adjusting the concentration of the Al-Mg-Sc alloy with Al or Mg, and the case of adjusting the concentration of the Al-Mg-Sc alloy with Sc.

Example

[0053] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not construed as being limited to the examples.

[0054] (Example 1) Aluminum powder having the particle size distribution shown in Fig. 2 (particle size of 300 μm or less, volume-based D50 particle size of 45 μm, purity of 99.99%) and scandium oxide powder having the particle size distribution shown in Fig. 3 (particle size of 100 μm or less, volume-based D50 particle size of 16 μm, purity of 99.99%) were blended so that the molar ratio was Al:Sc = 5:1, put into a mixing bottle, and the powder was uniformly mixed to obtain a composite powder. Next, the composite powder was put into a stainless steel mold and compacted under a pressure of 111 MPa to obtain a pellet (formed body). The pellet was put into a high-frequency furnace in a vacuum atmosphere of 1 to 2 kPa and heat-treated under the conditions of 700 °C for 1 hour. After the heat-treated pellet was pulverized, it was measured with an X-ray diffractometer. The measurement results are shown in Fig. 4. Then, the conversion rate to Al3Sc was determined according to (Equation 1) from the X-ray diffraction graph. The conversion rate was 58%. (Equation 1) Conversion rate (%) = Intensity (A) of the strongest line of Al3Sc / (Intensity (A) of the strongest line of Al3Sc + Intensity (B) of the strongest line of Sc2O3) × 100

[0055] (Examples 2 to 3) Alloying was carried out in the same manner as in Example 1 except for the temperature of the heat treatment under the following conditions. The obtained samples were measured by X-ray diffraction in the same manner as in Example 1, and calculated from the X-ray diffraction graph in the same method as in Example 1. The results of obtaining the conversion rate to Al3Sc are shown below. Example 2: Heat treatment temperature 800 °C, conversion rate to Al3Sc 32% Example 3: Heat treatment temperature 900 °C, conversion rate to Al3Sc 19%

[0056] (Example 4) Instead of putting the powder into the mixing bottle, the powder was put into the pot of the planetary mill together with zirconia balls. The pot of the planetary mill was filled with argon, oxygen was discharged, and then it was sealed. Mechanical alloying was carried out under the conditions of a mixing time of 3 hours and 180 rpm. This composite powder was treated in the same manner as in Example 1, and the obtained sample was measured by X-ray diffraction in the same manner as in Example 1. The conversion rate to Al3Sc was calculated from the X-ray diffraction graph in the same manner as in Example 1. The conversion rate was 82%.

[0057] (Examples 5 to 15) Alloying was carried out in the same manner as in Example 4 except for the following conditions, i.e., the mixing time and the heat treatment temperature. The obtained sample was measured by X-ray diffraction in the same manner as in Example 1. The results of calculating the conversion rate to Al3Sc from the X-ray diffraction graph in the same manner as in Example 1 are shown below. Example 5: Mixing time 3 hours, heat treatment temperature 600 °C, conversion rate to Al3Sc 9% Example 6: Mixing time 3 hours, heat treatment temperature 800 °C, conversion rate to Al3Sc 78% Example 7: Mixing time 3 hours, heat treatment temperature 900 °C, conversion rate to Al3Sc 44% Example 8: Mixing time 6 hours, heat treatment temperature 600 °C, conversion rate to Al3Sc 14% Example 9: Mixing time 6 hours, heat treatment temperature 700 °C, conversion rate to Al3Sc 88% Example 10: Mixing time 6 hours, heat treatment temperature 800 °C, conversion rate to Al3Sc 85% Example 11: Mixing time 6 hours, heat treatment temperature 900 °C, conversion rate to Al3Sc 35% Example 12: Mixing time 9 hours, heat treatment temperature 600 °C, conversion rate to Al3Sc 35% Example 13: Mixing time 9 hours, heat treatment temperature 700 °C, conversion rate to Al3Sc 92% Example 14: Mixing time 9 hours, heat treatment temperature 800 °C, conversion rate to Al3Sc 88% Example 15: Mixing time 9 hours, heat treatment temperature 900 °C, conversion rate to Al3Sc 51%

[0058] (Example 16) Aluminum powder having the particle size distribution shown in Fig. 2 (particle size of 300 μm or less, volume-based D50 particle size of 45 μm, purity of 99.99%) and scandium oxide powder having the particle size distribution shown in Fig. 3 (particle size of 100 μm or less, volume-based D50 particle size of 16 μm, purity of 99.99%) were blended so that the molar ratio was Al:Sc = 1:1. Instead of a planetary mill, they were put into the mixing tank of a nanomec reactor capable of high energy milling (hereinafter referred to as HEM), filled with argon, exhausted of oxygen, sealed, and mechanical alloying was carried out. Mechanical alloying was carried out for 115 minutes under the condition of alternately repeating 1000 rpm × 45 seconds and 500 rpm × 15 seconds. This composite powder was put into a stainless steel mold and compacted under a pressure of 87 MPa to obtain a pellet (formed body). Thereafter, it was treated in the same manner as in Example 1, and the obtained sample was measured for X-ray diffraction in the same manner as in Example 1. The conversion rate to Al3Sc was calculated from the X-ray diffraction graph in the same manner as in Example 1. The conversion rate was 45%.

[0059] (Examples 17 to 18) Alloying was carried out under the following conditions, that is, the same as in Example 16 except for the heat treatment temperature. The obtained sample was measured for X-ray diffraction in the same manner as in Example 1. The results of calculating the conversion rate to Al3Sc from the X-ray diffraction graph in the same manner as in Example 1 are shown below. Example 17: Heat treatment temperature 500 °C, conversion rate to Al3Sc 16% Example 18: Heat treatment temperature 600 °C, conversion rate to Al3Sc 45%

[0060] In the HEM treatment using the nanomec reactor of Examples 16 to 18, SEM observation and EDS mapping of the composite powder were carried out after the HEM time was 10 minutes, 55 minutes, and 155 minutes. The observation results are shown in Figs. 5(A), 5(B), and 5(C).

[0061] (Example 19) A mechanically alloyed composite powder was obtained in the same manner as in Example 4, except that the mixing time of mechanical alloying was 9 hours. After putting the mechanically alloyed composite powder into a carbon mold, the atmosphere was made into a vacuum of about 2 Pa in a spark plasma sintering (SPS) apparatus, and then a heat and pressure treatment was carried out at 600 °C under a pressure of 30 MPa for 1 hour. X-ray diffraction measurement was performed on the obtained sample in the same manner as in Example 1. The measurement results are shown in Fig. 9. Then, the conversion rate to Al3Sc was calculated in the same manner as in Example 1 from the X-ray diffraction graph. The conversion rate was 98%.

[0062] (Example 20) The sample obtained in Example 19 and Al were put into a boron nitride crucible and heated to 1450 °C by high-frequency heating to dissolve Al. The sample of the scandium-containing alloy dissolved in Al and Al was cooled, and SEM observation and EDS mapping of the cross section were performed. The observation results are shown in Figs. 10(a), 10(b), 10(c) and 10(d). From the results of SEM observation and EDS mapping, Al and Sc were confirmed in the Al phase portion. Also, oxygen (O) was not detected.

[0063] In the comparison of Examples 1 to 3, reduction proceeded even at the heat treatment temperatures of 800 °C and 900 °C, but the conversion rate was the highest at 700 °C. As it was closer to the melting point of Al (660 °C), a result that reduction proceeded more easily was obtained.

[0064] In the comparison of Examples 4 to 15, in all cases of temperature, the longer the mechanical alloying time, the higher the conversion rate tended to be. It is considered that the longer the time, the more the refinement of the particle size of each powder and the increase in the contact area between the powders contributed.

[0065] In Examples 16 to 18, Al3Sc was confirmed not only at a heat treatment temperature of 700 °C, but also at 500 °C and 600 °C. It was suggested that the reaction from Sc2O3 to Al3Sc was promoted by HEM using a nanoreactor. Also, from the SEM image and EDS mapping results of the composite powder after HEM treatment, the dispersion of Sc2O3 in the Al powder was confirmed. Ten minutes after the treatment, Sc2O3 was sufficiently dispersed and in contact with Al, and was presumably alloyed. Furthermore, X-ray diffraction measurements were performed on the composite powder after HEM treatment using an X-ray diffractometer. The measurement results are shown in FIGS. 6 to 8. When confirmed by XRD, the full width at half maximum of the peak widened in the initial stage of mixing (FIGS. 6 and 7), indicating that it was refined. After that, the full width at half maximum returned to its original value (FIG. 8), and at this point, the peak of Al3Sc could not be confirmed. This is because scandium oxide has not been reduced, but it is considered that aluminum metal is in sufficient contact with scandium oxide and alloyed like an oxide dispersion material, which contributed to the reduction in a lower temperature range.

[0066] In Example 19, a conversion rate of 98% was achieved. It was suggested that the reaction from Sc2O3 to Al3Sc was promoted by heating under pressure.

[0067] In Example 20, Al and Sc were confirmed in the Al phase. The Al3Sc (melting point: about 1320 °C) produced in Example 19 melted together with Al (melting point about 660 °C) by heating. Then, it is considered that Al3Sc precipitated in the Al phase during cooling. Since oxides such as Sc2O3 have a high melting point relative to the heating temperature, it is considered that they remained in a lump without melting, and the scandium-containing alloy containing Al3Sc and Sc2O3 can be physically separated and removed.

Claims

1. A preparation step of preparing a composite powder including a powder of a scandium compound containing at least one selected from the group consisting of scandium oxide, scandium fluoride, and scandium chloride, and a metal powder containing at least one of aluminum or magnesium, or both aluminum and magnesium; A heating step of heating the composite powder to 500° C. or higher in a vacuum atmosphere or an inert gas atmosphere; A method for producing a scandium-containing alloy, characterized by comprising the above steps.

2. A mold-filling step of putting the composite powder into a mold; A molding step of applying pressure to the composite powder to form a molded body; further comprising, The heating step is a step of heating the composite powder formed into the molded body, and the method for producing a scandium-containing alloy according to claim 1, characterized in that.

3. Further comprising a mold-filling step of putting the composite powder into a mold, The heating step is a step of heating the composite powder put into the mold under pressure in a vacuum atmosphere or an inert gas atmosphere, and the method for producing a scandium-containing alloy according to claim 1, characterized in that.

4. Further comprising a mechanical alloying step A of mechanically alloying the composite powder prepared in the preparation step, The mold-filling step is a step of putting the composite powder mechanically alloyed as the composite powder into the mold, and the method for producing a scandium-containing alloy according to claim 2 or 3, characterized in that.

5. The composite powder prepared in the preparation step further contains at least one selected from the group consisting of carboxylic acid, ascorbic acid, and higher fatty acid as an auxiliary agent, Further comprising a mechanical alloying step B of mechanically alloying the composite powder containing the auxiliary agent prepared in the preparation step, The mold-filling step is a step of putting the composite powder mechanically alloyed as the composite powder into the mold, and the method for producing a scandium-containing alloy according to claim 2 or 3, characterized in that.

6. The particle size of the powder of the scandium compound is 1000 μm or less, and the method for producing a scandium-containing alloy according to claim 1, characterized in that.

7. The particle size of the metal powder is 2000 μm or less, and the method for producing a scandium-containing alloy according to claim 1, characterized in that.

8. In the molding step, the pressure applied to the composite powder is 5 MPa or more, and the method for producing a scandium-containing alloy according to claim 2, characterized in that.

9. The method for producing a scandium-containing alloy according to claim 3, wherein in the heating step, the pressure applied to the composite powder is 5 MPa or more.

10. The scandium-containing alloy obtained through the heating process includes an aluminum scandium-containing alloy, and the aluminum scandium alloy in the aluminum scandium-containing alloy is an aluminum scandium solid solution alloy, Al ３ Sc intermetallic compound, Al ２ The method for producing a scandium-containing alloy according to any one of claims 1 to 3, characterized by containing at least one selected from the group consisting of Sc intermetallic compound and AlSc intermetallic compound.

11. The scandium-containing alloy obtained through the heating step includes a magnesium scandium-containing alloy, and the magnesium scandium alloy in the magnesium scandium-containing alloy includes at least one selected from the group consisting of a magnesium scandium solid solution alloy and an MgSc intermetallic compound. The method for producing a scandium-containing alloy according to any one of claims 1 to 3.

12. The method for producing a scandium-containing alloy according to any one of claims 1 to 3, further comprising a purification step of melting the scandium-containing alloy obtained through the heating step with either aluminum or magnesium, or both aluminum and magnesium in a vacuum atmosphere or an inert gas atmosphere to remove impurities.

13. The method for producing a scandium-containing alloy according to claim 12, wherein the impurities include at least one selected from the group consisting of aluminum oxide, magnesium oxide, and scandium oxide.

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