A rare earth aluminum master alloy and its preparation method

Abstract

This invention provides a rare earth aluminum master alloy and its preparation method. The preparation method includes the following steps: S1, removing slag from the surface of a first melt after melting to obtain a first melt; the first melt includes metallic aluminum and rare earth aluminum raw materials; the melting temperature is 800-1200℃; S2, heat-treating a second mixture to obtain a second melt; the second mixture includes the first melt, rare earth fluorides, and alkali metal halides; S3, separating the second melt to obtain molten metal and rare earth aluminum slag; S4, pouring the molten metal and cooling to obtain the rare earth aluminum master alloy. This method is simple, has a short operation process, is environmentally friendly and safe, has low cost, and a high yield of rare earth metals. Furthermore, the obtained rare earth aluminum master alloy exhibits minimal segregation, fine and uniformly distributed mesophase grains, and no agglomeration.

Description

Technical Field

[0001] This invention relates to a rare earth aluminum master alloy and its preparation method. Background Technology

[0002] In recent years, the application of lightweight alloys has received increasing attention. Among them, aluminum and aluminum alloys are widely used in aerospace, automotive, shipbuilding, cable and wire, and building construction due to their advantages such as low density, good electrical and thermal conductivity, good corrosion resistance, good plasticity, and ease of processing. However, with the increasing demands of use, there is a need to develop new high-performance aluminum alloy materials, and changing the alloy composition is one of the important methods for developing new aluminum alloys. Among these, rare earth elements, as one of the key and effective microalloying elements, are widely used in the preparation of high-performance aluminum and its alloy materials due to their special chemical properties.

[0003] Rare earth aluminum master alloys can be prepared by doping. However, due to the high reactivity of rare earth metals and their significant difference in melting point compared to metallic aluminum, the molten aluminum must be subjected to substantial superheat during smelting, resulting in significant burn-off. Furthermore, the resulting rare earth aluminum master alloys exhibit uneven distribution of the intermediate phase, large grain size, and agglomeration, which is detrimental to subsequent utilization. Additionally, the preparation of pure rare earth metals is costly and yields low, introducing impurities such as tungsten and calcium. Vacuum thermal reduction and molten salt electrolysis methods require complex equipment; the latter has low conversion rates, necessitates long-term continuous production, and the electrolysis mechanism is currently unclear, making practical operation difficult.

[0004] Therefore, there is an urgent need for a method for preparing rare earth aluminum master alloys that is simple in process, easy to operate, and can produce rare earth aluminum master alloys with good microstructure. Summary of the Invention

[0005] To overcome the limitations of existing technologies, such as complex processes, high operational difficulty, high costs, and difficulty in obtaining rare earth aluminum master alloys with uniform mesophase distribution, small grain size, and no agglomeration, this invention provides a rare earth aluminum master alloy and its preparation method. This method features a simple process, short operation flow, environmental friendliness and safety, low cost, and high rare earth metal yield. Furthermore, the obtained rare earth aluminum master alloy exhibits minimal segregation, fine and uniformly distributed mesophase grains, and no agglomeration. Moreover, the rare earth content of the master alloy remains relatively stable across batches.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] This invention provides a method for preparing a rare earth aluminum master alloy, which includes the following steps:

[0008] S1. Remove the slag from the surface of the first melt after melting to obtain the first melt; the first melt includes metallic aluminum and rare earth aluminum raw materials; the melting temperature is 800-1200℃; the rare earth aluminum raw materials are: rare earth aluminum slag obtained by aluminothermic reaction, and / or, the rare earth aluminum slag in step S3 below.

[0009] S2. The second mixture is subjected to heat treatment to obtain a second melt; the second mixture includes the first melt, rare earth fluorides and alkali metal halides; the heat treatment temperature is 800-1100℃.

[0010] S3. Separate the second melt to obtain molten metal and rare earth aluminum slag;

[0011] S4. Pour the molten metal and cool it to obtain a rare earth aluminum master alloy.

[0012] In this invention, the rare earth aluminum master alloy is prepared by an aluminothermic reduction reaction.

[0013] In step S1 of the present invention, the waste residue will affect the slag formation effect of subsequent addition of rare earth fluorides and alkali metal halides; by removing the waste residue, not only can the fluidity of the subsequently generated rare earth aluminum slag be improved, but the yield of rare earth elements can also be improved.

[0014] In some embodiments, in step S1, the rare earth aluminum raw material includes aluminum and rare earth elements; preferably, the rare earth elements include yttrium, scandium, lanthanum, neodymium, samarium, terbium, erbium, or thulium; preferably, the content of the rare earth elements is 0.5% or more, where % is the percentage of the mass of the rare earth elements in the total mass of the rare earth aluminum raw material.

[0015] In this invention, those skilled in the art should know that the rare earth elements in the rare earth aluminum raw material should be the same as the rare earth elements in the rare earth fluoride described in step S2.

[0016] In a specific embodiment, the content of the rare earth element is 1% or more, where % is the percentage of the mass of the rare earth element to the total mass of the rare earth aluminum raw material, preferably 1%-5%, for example 1.41% or 1.93%.

[0017] In a specific embodiment, the aluminum content is 3%-15%, where % is the percentage of the mass of aluminum in the total mass of rare earth aluminum raw materials, preferably 5%-10%, for example 5.61% or 6.26%.

[0018] In a specific implementation, the rare earth aluminum raw material also includes alkali metal elements, fluorine elements, and oxygen elements.

[0019] Preferably, the content of the alkali metal element is 10%-20%, where % is the percentage of the mass of the alkali metal element to the total mass of the rare earth aluminum raw material, and more preferably it is 12%-15%, for example 12.32% or 14.10%.

[0020] Preferably, the fluorine content is 50%-80%, where % is the percentage of fluorine by mass in the total mass of the rare earth aluminum raw material, and more preferably 65%-70%, for example 68.00% or 69.30%.

[0021] Preferably, the oxygen content is 5%-15%, where % is the percentage of oxygen by mass relative to the total mass of the rare earth aluminum raw material, and more preferably 10%-12%, for example 10.36% or 10.71%.

[0022] In one embodiment, in step S1, the rare earth aluminum raw material includes 68.00% F, 14.10% Na, 5.61% Al, 1.93% Sc and 10.36% O.

[0023] In one embodiment, in step S1, the waste residue includes 67.00% F, 13.43% Na, 7.81% Al, 0.63% Sc, and 11.13% O.

[0024] In this invention, the ratio of metallic aluminum to rare earth aluminum slag, as well as the appropriate melting temperature and time, are set to have a positive effect on the uniform distribution of the intermediate phase in the rare earth aluminum master alloy.

[0025] In this field, the rare earth element content in the rare earth aluminum raw materials is low, and they are generally collected and processed separately. Furthermore, the detection of rare earth element content in rare earth aluminum raw materials or rare earth aluminum slag fluctuates significantly, with no specific content value; if introduced into the raw materials, it will affect the stability of the rare earth content in the intermediate alloy.

[0026] In some embodiments, in step S1, the mass ratio of metallic aluminum to rare earth aluminum raw materials is 1:(0.03-0.1), preferably 1:(0.04-0.08), more preferably 1:(0.04-0.06, for example 1:0.04, 1:0.041, 1:0.045, 1:0.049, 1:0.051, 1:0.054, 1:0.057, or 1:0.06. By controlling the above ratio of metallic aluminum to rare earth aluminum raw materials, a stable intermediate alloy with rare earth content can be further obtained.

[0027] In some embodiments, in step S1, the melting temperature is 850-1100°C, preferably 880-1050°C, for example 880°C, 900°C, 920°C, 950°C or 1050°C.

[0028] In some embodiments, in step S1, the aluminothermic reaction is: reacting metallic aluminum with rare earth fluorides.

[0029] In some embodiments, in step S1, the aluminothermic reaction is: reacting metallic aluminum with rare earth oxides.

[0030] In some embodiments, the temperature of the aluminothermic reaction in step S1 is 800-1200°C.

[0031] In some embodiments, in step S1, the aluminum metal comprises aluminum ingots.

[0032] In some embodiments, in step S1, the melting time is 10-30 min, preferably 10-20 min, more preferably 10-15 min, for example 10 min or 15 min.

[0033] In some embodiments, in step S1, the melting process is carried out in a crucible of a medium-frequency induction melting furnace.

[0034] In this invention, if continuous stirring is carried out during the melting process, i.e., the time interval between the first stirring is low or zero, the aluminum liquid will be exposed, resulting in the loss of rare earth elements. If the stirring interval is long during the melting process, such as 15 minutes, the reaction will be incomplete.

[0035] In some embodiments, in step S1, the melting process is carried out under a first stirring, the interval of the first stirring is 5-10 minutes, preferably 5-8 minutes, for example 5 minutes; the first stirring method includes induction cooker stirring and / or mechanical stirring; preferably, the mechanical stirring includes graphite rod stirring.

[0036] In some embodiments, in step S2, the mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.03-0.18), preferably 1:(0.05-0.15), more preferably 1:(0.05-0.13), for example 1:0.05, 1:0.059, 1:0.06, 1:0.07 or 1:0.13.

[0037] In some embodiments, in step S2, the mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.03-0.08), preferably 1:(0.03-0.07), more preferably 1:(0.035-0.07), for example 1:0.035, 1:0.04, 1:0.05, 1:0.06 or 1:0.07.

[0038] In some embodiments, in step S2, the temperature of the heat preservation treatment is 900-1100°C, more preferably 920-1070°C, for example 920°C, 950°C, 970°C, 980°C, 1000°C or 1070°C.

[0039] In some embodiments, the heat preservation treatment time in step S2 is 30-60 minutes, preferably 40-60 minutes, for example 40 minutes, 50 minutes or 60 minutes.

[0040] In some embodiments, in step S2, the heat preservation process is carried out under a second stirring, the interval of the second stirring is 5-10 minutes, preferably 5 minutes; the second stirring method includes induction cooker stirring and / or mechanical stirring; preferably, the mechanical stirring is graphite rod stirring.

[0041] The simultaneous use of induction stirring and mechanical stirring can reduce the size of the mesophase grains in rare earth aluminum alloys, making the composition more uniform. Kinetically, it promotes the reaction between the molten metal and the slag, further improving the yield and reducing the reaction time.

[0042] In some embodiments, in step S2, the rare earth fluoride is yttrium fluoride, scandium fluoride, lanthanum fluoride, neodymium fluoride, samarium fluoride, terbium fluoride, erbium fluoride, or thulium fluoride; the rare earth elements in the rare earth fluoride are the same as those in the rare earth aluminum alloy material.

[0043] In this invention, the rare earth elements in the rare earth aluminum raw material in step S1 and the rare earth elements in the rare earth fluoride in step S2 can be the same or different; when the two rare earth elements are the same, the final product is a binary master alloy; when the two rare earth elements are different, the final product is a ternary master alloy.

[0044] In this invention, the alkali metal halide does not participate in the aluminothermic reaction, but it can lower the melting point of the slag system and dissolve the preferably added oxides, thus having a wetting effect on the aluminum melt and the slag system and promoting the aluminothermic reaction. Here, the slag system can be rare earth aluminum slag.

[0045] In some embodiments, in step S2, the alkali metal halide is potassium fluoride, lithium fluoride, sodium fluoride, sodium fluoroaluminate, potassium fluorochlorate, or calcium fluoride.

[0046] In some embodiments, in step S2, the second mixture further includes rare earth oxides; the rare earth oxides are identical to the rare earth elements in the rare earth fluorides. By adding the rare earth oxides, a portion of the rare earth fluorides can be replaced, resulting in a rare earth aluminum master alloy without affecting the yield, thus reducing some of the fluorination costs.

[0047] In specific embodiments, the rare earth oxides include yttrium oxide, scandium oxide, lanthanum oxide, neodymium oxide, samarium oxide, terbium oxide, erbium oxide, or thulium oxide.

[0048] In a specific embodiment, the mass ratio of the metallic aluminum to the rare earth oxide is 1:(0.002-0.02), preferably 1:(0.002-0.01), for example 1:0.002, 1:0.006, 1:0.007, 1:0.008, 1:0.009 or 1:0.01.

[0049] In some embodiments, in step S2, the second mixture does not contain potassium cryolite and sodium cryolite.

[0050] In some embodiments, in step S3, the separation temperature is 750-900°C, preferably 780-900°C, for example 780°C, 800°C, 810°C, 820°C or 900°C.

[0051] In this invention, the second melt obtained in step S2 is a molten metal with rare earth aluminum slag on its surface.

[0052] In some embodiments, step S3 involves separating the rare earth aluminum slag from the surface of the second melt.

[0053] In one embodiment, in step S3, the rare earth aluminum slag material includes 69.30% F, 12.32% Na, 6.26% Al, 1.41% Sc and 10.71% O.

[0054] In this invention, the pouring temperature is higher than the liquidus temperature, which refers to the highest temperature at which the melt changes from a liquid to a solid state, also known as the "primary crystallization temperature".

[0055] In this invention, the cooling process is designed to ensure rapid solidification of the rare earth aluminum master alloy in order to suppress the growth and agglomeration of the meso phase.

[0056] In some implementations, in step S4, the cooling method includes water cooling, air cooling, or cooling with a cooler.

[0057] In some embodiments, the pouring temperature is 750-900°C, preferably 780-900°C, for example 780°C, 800°C, 810°C, 820°C or 900°C.

[0058] In some embodiments, the pouring rate is 0.25-0.3 L / s.

[0059] In some embodiments, the time for the molten metal to cool to a completely solidified state is less than 20 seconds.

[0060] In some embodiments, the molten metal is cooled to room temperature for 10-15 minutes in order to demold.

[0061] The present invention also provides a rare earth aluminum master alloy, which is prepared by the rare earth aluminum master alloy preparation method described above.

[0062] In some embodiments, the rare earth element content of the rare earth aluminum master alloy is less than 10%, where % is the ratio of the mass of the rare earth element to the total mass of the rare earth aluminum master alloy; preferably, it is greater than 1.5% and less than 8.5%.

[0063] Based on common knowledge in the field, the above-mentioned preferred conditions can be combined arbitrarily to obtain various preferred embodiments of the present invention.

[0064] The reagents and raw materials used in this invention are all commercially available.

[0065] The positive and progressive effects of this invention are as follows:

[0066] 1. In the preparation process of this invention, rare earth aluminum slag produced by the aluminothermic reaction is used to recycle the rare earth aluminum slag, which reduces the amount of fluoride used, making it more environmentally friendly and economical, and the yield of rare earth elements in the raw materials is relatively high.

[0067] 2. The preparation method of the present invention can achieve a high yield of rare earth metals, and the preferred scheme can achieve at least 79%.

[0068] 3. The molten salt system in this invention uses a fluoride salt system, which is more stable and less prone to moisture absorption than the chloride salt system, making production safer and more stable.

[0069] 4. The rare earth aluminum master alloy prepared by this invention has a uniform distribution of intermediate phase and a relatively small grain size; moreover, the rare earth content of the master alloy is relatively stable between batches. Attached Figure Description

[0070] Figure 1 This is a process flow diagram of the preparation of rare earth aluminum master alloy in Example 1 of the present invention;

[0071] Figure 2This is an electron microscope image of the aluminum-scandium master alloy obtained in Example 2 of the present invention;

[0072] Figure 3 This is an electron microscope image of the aluminum-scandium master alloy prepared in Comparative Example 1 of the present invention. Detailed Implementation

[0073] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0074] Example 1

[0075] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy. Figure 1 This is a process flow diagram for preparing rare earth aluminum master alloys in this embodiment.

[0076] The aluminum yttrium slag used in this embodiment is the slag obtained from the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 900°C for 10 minutes, then yttrium oxide, yttrium fluoride and potassium fluoride are added, and the mixture is kept at this temperature for 40 minutes. The slag is then removed from the surface of the high-temperature liquid phase using a tool. The mass ratio of aluminum ingots, yttrium oxide, yttrium fluoride and potassium fluoride is 1:0.008:0.09:0.04.

[0077] The preparation steps are as follows:

[0078] The materials used in this preparation method are: 16.5 kg aluminum ingot, 0.743 kg yttrium aluminum slag, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, with a mass ratio of 1:0.045:0.008:0.09:0.04.

[0079] S1. Add aluminum ingots and yttrium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900°C for 10 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0080] S2. Add the above-mentioned mass of yttrium oxide, yttrium fluoride, and potassium fluoride to the first melt, and heat to 900°C to completely melt the material. Hold the temperature for 40 minutes, and stir the material evenly with a graphite rod every 5 minutes to obtain the second melt.

[0081] S3. After the heat preservation is completed, wait until the temperature drops to 800℃, then use a tool to remove and preserve the aluminum yttrium slag material on the surface of the second melt as the aluminum yttrium slag material in step S1.

[0082] S4. Pour the molten metal into a cooler to cool, and obtain an aluminum-yttrium master alloy; the pouring temperature is 750-900℃, the pouring speed is 0.25-0.3L / s; the time for the molten metal to cool to a completely solidified state is less than 20s; the time for the molten metal to cool to room temperature is 10-15min.

[0083] Example 2

[0084] This embodiment discloses a method for preparing an aluminum-scandium intermediate alloy.

[0085] The aluminum scandium slag used in this embodiment is the slag obtained from the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 900°C for 15 minutes, then scandium oxide, scandium fluoride and sodium fluoride are added, and the mixture is kept at this temperature for 40 minutes. The aluminum scandium slag is then removed from the surface of the high-temperature liquid phase using a tool. The mass ratio of aluminum ingots, scandium oxide, scandium fluoride and sodium fluoride is 1:0.002:0.059:0.06.

[0086] The preparation steps are as follows:

[0087] The materials used in this preparation method are: 20 kg aluminum ingot, 0.8 kg scandium aluminum slag, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 1.2 kg sodium fluoride, with a mass ratio of 1:0.04:0.002:0.059:0.06.

[0088] S1. Add aluminum ingots and scandium aluminum slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900℃ for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0089] S2. Add the above-mentioned mass of scandium oxide, scandium fluoride, and sodium fluoride to the first melt, and heat to 1000℃. The material is completely melted and kept at this temperature for 60 minutes. During this period, the material is stirred evenly with a graphite rod every 5 minutes to obtain the second melt.

[0090] S3. After the heat preservation is completed, wait until the temperature drops to 900℃, then use a tool to remove and preserve the aluminum scandium slag material on the surface of the second melt as the aluminum scandium slag material in step S1.

[0091] S4. Pour the molten metal into a cooler to cool it, and obtain an aluminum-scandium intermediate alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0092] The aluminum scandium slag in step S1 comprises 68.00% F, 14.10% Na, 5.61% Al, 1.93% Sc and 10.36% O.

[0093] The waste residue in step S1 includes 67.00% F, 13.43% Na, 7.81% Al, 0.63% Sc and 11.13% O.

[0094] The aluminum scandium slag in step S3 contains 69.30% F, 12.32% Na, 6.26% Al, 1.41% Sc, and 10.71% O. The elemental contents of the slag and waste residue were obtained by XRF scanning analysis.

[0095] Example 3

[0096] This embodiment discloses a method for preparing an aluminum-lanthanum intermediate alloy.

[0097] The lanthanum aluminum slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 950°C for 15 minutes. Lanthanum oxide, lanthanum fluoride and sodium fluoride are then added to the furnace and kept at this temperature for 50 minutes. The slag is then removed from the surface of the high-temperature liquid phase using a tool. The mass ratio of aluminum ingots, lanthanum oxide, lanthanum fluoride and sodium fluoride is 1:0.006:0.07:0.04.

[0098] The preparation steps are as follows:

[0099] The materials used in this preparation method are: 14.5 kg aluminum ingot, 0.827 kg lanthanum aluminum slag, 0.087 kg lanthanum oxide, 1.015 kg lanthanum fluoride, and 0.58 kg sodium fluoride, with a mass ratio of 1:0.057:0.006:0.07:0.04.

[0100] S1. Add aluminum ingots and lanthanum aluminum slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 950°C for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0101] S2. Add the above-mentioned mass of lanthanum oxide, lanthanum fluoride, and sodium fluoride to the first melt; and heat to 970°C until the material is completely melted. Hold the temperature for 50 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0102] S3. After the heat preservation is completed, wait until the temperature drops to 780℃, then use a tool to remove and preserve the aluminum lanthanum slag on the surface of the second melt as the aluminum lanthanum slag in step S1.

[0103] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-lanthanum master alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0104] Example 4

[0105] This embodiment discloses a method for preparing an aluminum-neodymium intermediate alloy.

[0106] The aluminum-neodymium slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 900°C for 15 minutes, then neodymium oxide, neodymium fluoride and lithium fluoride are added, the temperature is maintained for 40 minutes, and then the aluminum-neodymium slag is obtained by removing it from the surface of the high-temperature liquid phase with a tool. The mass ratio of aluminum ingots, neodymium oxide, neodymium fluoride and lithium fluoride is 1:0.007:0.05:0.06.

[0107] The preparation steps are as follows:

[0108] The materials used in this preparation method are: 13.8 kg aluminum ingot, 0.566 kg aluminum neodymium slag, 0.097 kg neodymium oxide, 0.69 kg neodymium fluoride, and 0.828 kg lithium fluoride, with a mass ratio of 1:0.041:0.007:0.05:0.06;

[0109] S1. Add aluminum ingots and neodymium aluminum slag to the graphite crucible of the medium-frequency induction furnace; heat and melt at 920℃ for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0110] S2. Add the above-mentioned mass of neodymium oxide, neodymium fluoride, and lithium fluoride to the first melt; and heat to 950°C until the material is completely melted. Hold the temperature for 40 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0111] S3. After the heat preservation is completed, wait until the temperature drops to 820℃, then use a tool to remove and preserve the aluminum-neodymium slag on the surface of the second melt as the aluminum-neodymium slag in step S1.

[0112] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-neodymium master alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0113] Example 5

[0114] This embodiment discloses a method for preparing an aluminum-samarium intermediate alloy.

[0115] The aluminum samarium slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 950°C for 15 minutes, then samarium oxide, samarium fluoride and sodium fluoride are added, and the mixture is kept at this temperature for 60 minutes. The slag is then removed from the surface of the high-temperature liquid phase with a tool to obtain the aluminum samarium slag. The mass ratio of aluminum ingots, samarium oxide, samarium fluoride and sodium fluoride is 1:0.009:0.06:0.035.

[0116] The preparation steps are as follows:

[0117] The materials used in this preparation method are: 14.8 kg aluminum ingot, 0.725 kg samarium aluminum slag, 0.133 kg samarium oxide, 0.888 kg samarium fluoride, and 0.518 kg sodium fluoride, with a mass ratio of 1:0.049:0.009:0.06:0.035.

[0118] S1. Add aluminum ingots and aluminum samarium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900°C for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0119] S2. Add the above-mentioned mass of samarium oxide, samarium fluoride, and sodium fluoride to the first melt; and heat to 950°C until the material is completely melted. Hold the temperature for 60 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0120] S3. After the heat preservation is completed, when the temperature drops to 810℃, use a tool to remove and preserve the aluminum samarium slag material on the surface of the second melt as the aluminum samarium slag material in step S1.

[0121] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-samarium master alloy; the casting conditions in this embodiment are the same as those in Embodiment 1.

[0122] Example 6

[0123] This embodiment discloses a method for preparing an aluminum-terbium intermediate alloy.

[0124] The aluminum terbium slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 880°C for 15 minutes, then terbium oxide, terbium fluoride and lithium fluoride are added, the temperature is maintained for 50 minutes, and then the slag is removed from the surface of the high-temperature liquid phase with a tool to obtain the aluminum terbium slag. The mass ratio of aluminum ingots, terbium oxide, terbium fluoride and lithium fluoride is 1:0.01:0.05:0.05.

[0125] The preparation steps are as follows:

[0126] The materials used in this preparation method are: 15.1 kg aluminum ingot, 0.906 kg aluminum terbium slag, 0.151 kg terbium oxide, 0.755 kg terbium fluoride, and 0.755 kg lithium fluoride, with a mass ratio of 1:0.06:0.01:0.05:0.05;

[0127] S1. Add aluminum ingots and aluminum terbium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 880°C for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0128] S2. Add the above-mentioned mass of terbium oxide, terbium fluoride, and lithium fluoride to the first melt; and heat to 920°C until the material is completely melted. Hold the temperature for 50 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0129] S3. After the heat preservation is completed, wait until the temperature drops to 800℃, then use a tool to remove and preserve the aluminum terbium slag on the surface of the second melt as the aluminum terbium slag in step S1.

[0130] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-terbium intermediate alloy; the casting conditions in this embodiment are the same as those in Embodiment 1.

[0131] Example 7

[0132] This embodiment discloses a method for preparing an aluminum-erbium intermediate alloy.

[0133] The aluminum erbium slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 1050°C for 15 minutes, then erbium oxide, erbium fluoride and sodium fluoride are added, and the mixture is kept at this temperature for 40 minutes. The slag is then removed from the surface of the high-temperature liquid phase using a tool. The mass ratio of aluminum ingots, erbium oxide, erbium fluoride and sodium fluoride is 1:0.008:0.13:0.07.

[0134] The preparation steps are as follows:

[0135] The materials used in this preparation method are: 13.6 kg aluminum ingot, 0.694 kg aluminum erbium slag, 0.109 kg erbium oxide, 1.768 kg erbium fluoride, and 0.952 kg sodium fluoride, with a mass ratio of 1:0.051:0.008:0.13:0.07.

[0136] S1. Add aluminum ingots and aluminum erbium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 1050℃ for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0137] S2. Add the above-mentioned mass of erbium oxide, erbium fluoride, and sodium fluoride to the first melt; and heat to 1070°C until the material is completely melted. Hold the temperature for 40 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0138] S3. After the heat preservation is completed, wait until the temperature drops to 810℃, then use a tool to remove and preserve the aluminum erbium slag on the surface of the second melt as the aluminum erbium slag in step S1.

[0139] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-erbium intermediate alloy; the casting conditions in this embodiment are the same as those in Embodiment 1.

[0140] Example 8

[0141] This embodiment discloses a method for preparing an aluminum thulium intermediate alloy.

[0142] The aluminum thulium slag used in this embodiment is the slag obtained by the previous aluminothermic reaction. The aluminothermic reaction is as follows: aluminum ingots are placed in a medium-frequency induction furnace and melted at 1050°C for 15 minutes. Then, thulium oxide, thulium fluoride and sodium fluoride are added to it, and the mixture is kept at this temperature for 40 minutes. The slag is then removed from the surface of the high-temperature liquid phase with a tool to obtain the aluminum thulium slag. The mass ratio of aluminum ingots, thulium oxide, thulium fluoride and sodium fluoride is 1:0.009:0.06:0.05.

[0143] The preparation steps are as follows:

[0144] The materials used in this preparation method are: 16.0 kg aluminum ingot, 0.864 kg aluminum thulium slag, 0.144 kg thulium oxide, 0.96 kg thulium fluoride, and 0.8 kg sodium fluoride, with a mass ratio of 1:0.054:0.009:0.06:0.05;

[0145] S1. Add aluminum ingots and aluminum thulium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 950°C for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0146] S2. Add the above-mentioned mass of thulium oxide, thulium fluoride, and sodium fluoride to the first melt; and heat to 980°C until the material is completely melted. Hold the temperature for 50 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0147] S3. After the heat preservation is completed, wait until the temperature drops to 900℃, then use a tool to remove and preserve the aluminum thulium slag on the surface of the second melt as the aluminum thulium slag in step S1.

[0148] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-thulium intermediate alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0149] Example 9

[0150] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with Embodiment 1, no stirring is performed during the heat preservation process in step S2 in this embodiment.

[0151] Specifically, the preparation steps are as follows:

[0152] The materials used in this preparation method are: 16.5 kg aluminum ingot, 0.743 kg yttrium aluminum slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, with a mass ratio of 1:0.045:0.008:0.09:0.04;

[0153] S1. Add aluminum ingots and yttrium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900°C for 10 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0154] S2. Add the above-mentioned amounts of yttrium oxide, yttrium fluoride, and potassium fluoride to the first melt; and heat to 900°C until the material is completely melted, and keep at that temperature for 40 minutes (without stirring).

[0155] S3. After the heat preservation is completed, wait until the temperature drops to 800℃, then use a tool to remove and preserve the aluminum yttrium slag on the surface of the second melt.

[0156] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-yttrium master alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0157] Example 10

[0158] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with Embodiment 1, this embodiment has a higher melting temperature in step S1 and a higher holding temperature in step S2, which is 1200°C.

[0159] Specifically, the preparation steps are as follows:

[0160] The materials used in this preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, with a mass ratio of 1:0.045:0.008:0.09:0.04.

[0161] S1. Add aluminum ingots and yttrium slag to the graphite crucible of the medium-frequency induction furnace according to the above-mentioned amounts; heat and melt at 1200℃ for 10 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0162] S2. Add the above-mentioned mass of yttrium oxide, yttrium fluoride, and potassium fluoride to the first melt; and heat to 1200℃ until the material is completely melted. Hold the temperature for 40 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0163] S3. After the heat preservation is completed, wait until the temperature drops to 800℃, then use a tool to remove and preserve the aluminum yttrium slag material on the surface of the second melt as the aluminum yttrium slag material in step S1.

[0164] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-yttrium master alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0165] Example 11

[0166] This embodiment describes a method for preparing an aluminum-erbium intermediate alloy. Compared to Example 7, the holding time in step S2 is shorter in this embodiment, at 20 minutes.

[0167] Specifically, the preparation steps are as follows:

[0168] The materials used in this preparation method are: 18.6 kg aluminum ingot, 0.949 kg aluminum erbium slag obtained in step S3 of Example 7, 0.149 kg erbium oxide, 2.418 kg erbium fluoride, and 1.302 kg sodium fluoride, with a mass ratio of 1:0.051:0.008:0.13:0.07.

[0169] S1. Add aluminum ingots and aluminum erbium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 1050℃ for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0170] S2. Add the above-mentioned mass of erbium oxide, erbium fluoride, and sodium fluoride to the first melt; and heat to 1070°C until the material is completely melted. Hold the temperature for 20 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0171] S3. After the heat preservation is completed, wait until the temperature drops to 810℃, then use a tool to remove and store the aluminum erbium slag material of the second molten material.

[0172] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-erbium intermediate alloy; the casting conditions in this embodiment are the same as those in Embodiment 1.

[0173] Example 12

[0174] This embodiment describes a method for preparing an aluminum-scandium intermediate alloy. Compared to Example 2, the amount of sodium fluoride added in step S2 is lower, at 0.4 kg; the mass ratio of aluminum ingot to sodium fluoride is 1:0.02.

[0175] Specifically, the preparation steps are as follows:

[0176] The materials used in this preparation method are: 20 kg aluminum ingot, 0.8 kg scandium aluminum slag, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 0.4 kg sodium fluoride, with a mass ratio of 1:0.04:0.002:0.059:0.02;

[0177] S1. Add aluminum ingots and scandium aluminum slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900°C for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0178] S2. Add the above-mentioned mass of scandium oxide, scandium fluoride, and sodium fluoride to the first melt; and heat to 1000℃ until the material is completely melted. Hold the temperature for 60 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0179] S3. After the heat preservation is completed, wait until the temperature drops to 900℃, then use a tool to remove and preserve the aluminum scandium slag on the surface of the second melt.

[0180] S4. Pour the molten metal into a cooler to cool it, and obtain an aluminum-scandium intermediate alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0181] Example 13

[0182] This embodiment discloses a method for preparing an aluminum-yttrium intermediate alloy; compared with embodiment 2, the amount of sodium fluoride added in step S2 of this embodiment is higher, at 1.6 kg; the mass ratio of aluminum ingot to sodium fluoride is 1:0.08.

[0183] Specifically, the preparation steps are as follows:

[0184] The materials used in this preparation method are: 20 kg aluminum ingot, 0.8 kg of aluminum scandium slag obtained in step S3 of Example 2, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 1.6 kg sodium fluoride, with a mass ratio of 1:0.04:0.002:0.059:0.08;

[0185] S1. Add aluminum ingots and scandium aluminum slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 900℃ for 15 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue on the surface of the first melt to obtain the first melt.

[0186] S2. Add the above-mentioned mass of scandium oxide, scandium fluoride, and sodium fluoride to the first melt; and heat to 1000℃ until the material is completely melted. Hold the temperature for 60 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0187] S3. After the heat preservation is completed, wait until the temperature drops to 900℃, then use a tool to remove and preserve the aluminum scandium slag material on the surface of the second melt as the aluminum scandium slag material in step S1.

[0188] S4. Pour the molten metal into a cooler to cool it, and obtain an aluminum-scandium intermediate alloy; the casting conditions in this embodiment are the same as those in Example 1.

[0189] Example 14

[0190] This embodiment describes a method for preparing an aluminum-neodymium intermediate alloy. Compared to Embodiment 4, this embodiment does not include aluminum-neodymium slag in step S1.

[0191] Specifically, the preparation steps are as follows:

[0192] The materials used in this preparation method are: 13.8 kg aluminum ingot, 0.097 kg neodymium oxide, 0.69 kg neodymium fluoride, and 0.828 kg lithium fluoride, with a mass ratio of 1:0.007:0.05:0.06;

[0193] S1. Add aluminum ingots, neodymium oxide, neodymium fluoride, and lithium fluoride to a graphite crucible in a medium-frequency induction furnace; heat to 950℃ and melt for 40 minutes, stirring the material evenly with a graphite rod every 5 minutes to obtain the melt.

[0194] S2. After the heat preservation is completed, wait until the temperature drops to 820℃, then use a tool to remove and preserve the aluminum-neodymium slag on the surface of the molten material.

[0195] S3. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-neodymium master alloy; the casting conditions in this embodiment are the same as those in Embodiment 1.

[0196] Example 15

[0197] This embodiment describes a method for preparing an aluminum-scandium intermediate alloy. Compared to Example 2, this embodiment involves mixing and melting aluminum ingots, aluminum-scandium slag, scandium oxide, scandium fluoride, and sodium fluoride together.

[0198] Specifically, the preparation steps are as follows:

[0199] The materials used in this preparation method are: 20 kg aluminum ingot, 0.8 kg of aluminum scandium slag obtained in step S3 of Example 2, 0.04 kg scandium oxide, 1.18 kg scandium fluoride, and 1.2 kg sodium fluoride, with a mass ratio of 1:0.04:0.002:0.059:0.06;

[0200] S1. Add aluminum ingots, scandium aluminum slag, scandium oxide, scandium fluoride, and sodium fluoride to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat to 1000℃ and heat and melt for 60 minutes to completely melt the materials. During this period, stir the materials evenly with a graphite rod every 5 minutes to obtain the melt.

[0201] S2. After the heat preservation is completed, wait until the temperature drops to 900℃, then use a tool to remove and preserve the aluminum scandium slag on the surface of the molten material.

[0202] S3. Pour the molten metal into a cooler to cool it, and obtain an aluminum-scandium intermediate alloy; the casting conditions in this embodiment are the same as those in embodiment 1.

[0203] In the above examples and comparative examples, the purity of the aluminum ingots used was 99.99% or higher, the purity of the rare earth oxides and fluorides was 99.9% or higher, and the purity of the alkali metal halides was 99.7% or higher.

[0204] Comparative Example 1

[0205] This comparative example illustrates a method for preparing an aluminum-scandium master alloy, which includes the following steps:

[0206] (1) For the production of aluminum-scandium intermediate alloy by doping method, weigh 20 kg of aluminum ingot and 0.04 kg of metallic scandium, with a mass ratio of 1:0.002, wherein the metallic scandium is crude scandium obtained by calcothermal reduction of scandium fluoride.

[0207] (2) Open the high vacuum medium frequency induction melting furnace and put the aluminum ingot and scandium metal into the graphite crucible;

[0208] (3) Close the furnace cover and vent valve, turn on the vacuum system, and evacuate to a vacuum level below 0.1 Pa;

[0209] (4) Turn on the medium frequency power supply, adjust the power to 15kw, bake the furnace for 20 minutes, then adjust it to 45kw, observe the situation inside the furnace, and when the material is completely melted and reaches 1000℃ through infrared temperature measurement, reduce the power to 20kw and keep it at 1000℃ for 30 minutes.

[0210] (5) After the heat preservation is completed, turn off the power and pour the molten metal into the mold to obtain the aluminum-scandium intermediate alloy.

[0211] Comparative Example 2

[0212] This comparative example illustrates the preparation method of an aluminum-yttrium intermediate alloy. Compared to Example 1, this comparative example has a lower melting temperature in step S1 and a lower holding temperature in step S2, both at 750°C, and there is no cooling process after the holding process.

[0213] Specifically, the preparation steps are as follows:

[0214] The materials used in this preparation method are: 16.5 kg aluminum ingot, 0.743 kg aluminum yttrium slag obtained in step S3 of Example 1, 0.132 kg yttrium oxide, 1.485 kg yttrium fluoride, and 0.66 kg potassium fluoride, with a mass ratio of 1:0.045:0.008:0.09:0.04.

[0215] S1. Add aluminum ingots and yttrium slag to the graphite crucible of the medium-frequency induction furnace according to the above dosage; heat and melt at 750°C for 10 minutes, stirring the material evenly with a graphite rod every 5 minutes to form the first melt; then remove the waste residue from the surface of the first melt to obtain the first melt.

[0216] S2. Add the above-mentioned mass of yttrium oxide, yttrium fluoride, and potassium fluoride to the first melt; and heat to 750°C until the material is completely melted. Hold the temperature for 40 minutes, stirring the material evenly with a graphite rod every 5 minutes during this period to obtain the second melt.

[0217] S3. After the heat preservation is completed, use a tool to remove and preserve the aluminum yttrium slag on the surface of the second melt.

[0218] S4. The molten metal is poured into a cooler to cool, thus obtaining an aluminum-yttrium master alloy; the casting conditions of this comparative example are the same as those of Example 1.

[0219] Example 1

[0220] Samples of the rare earth aluminum master alloys of Examples 1-15 and Comparative Examples 1-2 were taken at four different locations to detect their rare earth main components. The rare earth main component analysis method adopted was the conventional chemical titration method in the art. The samples were dissolved in acid, and titrated with EDTA standard solution using xylenol orange as an indicator. The rare earth content was determined by EDTA titration, with a determination range of 1%-20%wt. The procedure was: dissolution → volume adjustment → sampling → titration → result calculation.

[0221] Table 1 shows the principal component analysis data for samples from Examples 1-8, and Table 2 shows the principal component analysis data for samples from Comparative Examples 1-2 and Examples 9-15. The average value was used to obtain the rare earth content of the alloy ingot, and the yield was calculated as follows: Yield = Mass of rare earth elements in the alloy ingot / (Mass of rare earth elements in rare earth oxides + Mass of rare earth elements in rare earth fluorides). The results show that the yield of rare earth aluminum master alloys prepared by this method in the examples is all above 60%.

[0222] Table 1

[0223] project Sample Name Testing items Position 1 Position 2 Position 3 Position 4 mean yield Example 1 aluminum yttrium alloy Y%(wt) 4.52％ 5.12％ 5.05％ 4.93％ 4.91％ 85.30％ Example 2 Aluminum Scandium Alloy Sc%(wt) 2.35％ 2.45％ 2.29％ 2.38％ 2.37％ 89.00％ Example 3 Aluminum-lanthanum alloy La%(wt) 4.51％ 4.56％ 4.72％ 4.32％ 4.53％ 92.00％ Example 4 aluminum-neodymium alloy Nd% (wt) 3.22％ 3.33％ 3.17％ 3.30％ 3.26％ 81.20％ Example 5 Aluminum-Samarium Alloy Sm%(wt) 4.26％ 4.30％ 4.52％ 4.70％ 4.45％ 91.20％ Example 6 Aluminum Terbium Alloy Tb% (wt) 4.08％ 3.78％ 3.95％ 3.75％ 3.89％ 89.50％ Example 7 Aluminum-Erbium Alloy Er% (wt) 8.19％ 7.44％ 8.03％ 8.24％ 7.98％ 84.70％ Example 8 Aluminum thulium alloy Tm% (wt) 4.56％ 4.63％ 4.52％ 4.60％ 4.58％ 91.50％

[0224] Table 2

[0225]

[0226]

[0227] Compared with Example 1, Example 9 lacks the graphite rod stirring during the heat preservation process, resulting in a 21.3% decrease in yield. During the heat preservation process, the slag floats on the surface of the molten metal. The electromagnetic stirring of the medium-frequency induction furnace coil itself is not enough. Mechanical stirring is also required to increase the contact area between the metal and the slag, thereby promoting the reaction kinetically and increasing the yield.

[0228] Compared with Example 1, Example 10 has a holding temperature 300°C higher and a yield 6.3% lower. High temperature promotes the forward reaction, but the higher temperature also causes rare earth elements in the alloy to burn off, resulting in a lower yield.

[0229] Compared with Example 1, Comparative Example 2 had a lower heat preservation temperature of 150°C and a 59% lower yield. During the heat preservation process, the slag formation effect on the surface of the molten metal was poor, the slag fluidity was poor, which hindered the reaction between the slag and the molten metal and reduced the yield.

[0230] Compared with Example 7, Example 11 had a 20-minute shorter holding time and a 14.5% lower yield. Insufficient holding time resulted in incomplete reaction between the metal and slag, leading to a lower yield.

[0231] Compared with Example 2, Example 12 has a lower sodium fluoride content by 0.04%, resulting in a 23.5% decrease in yield. The lower sodium fluoride content is not conducive to reducing the melting point of the slag, leading to poor slag formation and hindering the reaction between the slag and the molten metal, thus reducing the yield.

[0232] Compared with Example 2, Example 13 showed that the proportion of sodium fluoride added increased by 0.02, and the yield decreased by 1.3%. The addition of more sodium fluoride had a small impact on the yield. Therefore, the excess alkali metal halide had little impact on the reaction and would result in waste of raw materials.

[0233] Compared with Example 4, Example 14 did not add rare earth aluminum slag, resulting in a yield reduction of 8.9%. The process steps did not include the recycling of rare earth aluminum slag, further reducing the yield.

[0234] Compared with Example 2, in Example 15, scandium oxide, scandium fluoride and sodium fluoride were added together with the aluminum scandium slag in step (2) in step (4), resulting in a 17.95% decrease in yield. The aluminum scandium slag itself is a slag generated by the aluminothermic reaction. The synthesis step of melting will reduce the concentration of rare earth elements in the feed, reduce the fluidity of the slag, and inhibit the reaction.

[0235] Example 2

[0236] This effective embodiment analyzes the impurity content and purity of the products from Example 2 and Comparative Example 1. Other impurity elements in the aluminum-scandium alloy samples of Example 2 and Comparative Example 1 were also detected using conventional ICP testing methods. Table 3 shows the impurity detection data for the samples from Comparative Example 1 and Example 2.

[0237] Table 3

[0238]

[0239] It is evident that the aluminum-scandium alloy prepared by the doping method in Comparative Example 1 contains significantly more tungsten and calcium impurities. The main reason for this result is that during the process of preparing metallic scandium by calcium thermal reduction in the doping method, excessive calcium and the alloying of metallic scandium with the tungsten crucible introduce impurities from the raw materials into the aluminum-scandium alloy in Comparative Example 1. To avoid introducing impurities from the raw materials, the metallic scandium needs to be purified by secondary distillation, but this would lead to a more complex process and increased costs.

[0240] The preparation method of this application directly reduces and alloys rare earth elements in oxides and fluorides. Compared with the doping method, it reduces the intermediate metal purification process steps, has a shorter operation process and lower cost. Furthermore, this method can further improve the purity of aluminum-scandium alloy products and reduce the impurity content on the basis of existing technologies.

[0241] Example 3

[0242] This effect example analyzes the intermediate phase distribution and grain size of the products in Example 2 and Comparative Example 1.

[0243] Specifically, the alloy ingots obtained in Example 2 and Comparative Example 1 were wire-cut to obtain metallographic samples with a side length of less than 1 cm. Electron microscopy metallographic analysis was then performed on these samples to obtain… Figure 2 and Figure 3 The analysis results. Figure 2 Electron microscope image of the aluminum-scandium intermediate alloy in Example 2; Figure 3 Electron microscope image of aluminum-scandium intermediate alloy for Comparative Example 1.

[0244] contrast Figure 2 and Figure 3 The results show that the mesophase grains of the alloy samples prepared by the doping method exhibit agglomeration, with grain sizes ranging from 16 to 143 μm. These grains are large and unevenly distributed. In contrast, the alloy samples prepared by this method have a uniformly distributed mesophase and relatively small grain sizes, ranging from 10 to 34 μm.

Claims

1. A method for preparing a rare earth aluminum master alloy, characterized in that, It includes the following steps: S1. Remove the slag from the surface of the first melt after melting to obtain the first melt; the first melt includes metallic aluminum and rare earth aluminum raw materials; the melting temperature is 800-1200℃; the rare earth aluminum raw materials are: rare earth aluminum slag obtained by aluminothermic reaction, and / or, the rare earth aluminum slag in step S3 below. S2. The second mixture is subjected to heat treatment to obtain a second melt; the second mixture includes the first melt, rare earth fluorides and alkali metal halides; the heat treatment temperature is 800-1100℃. S3. Separate the second melt to obtain molten metal and rare earth aluminum slag; S4. Pour the molten metal and cool it to obtain a rare earth aluminum master alloy.

2. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, Step S1 satisfies one or more of the following conditions: ①The rare earth aluminum raw material includes aluminum and rare earth elements; ②The mass ratio of the metallic aluminum to rare earth aluminum raw materials is 1:(0.03-0.1). ③ The melting temperature is 850-1100℃; ④ The aluminothermic reaction is: reacting metallic aluminum with rare earth fluorides, and / or reacting metallic aluminum with rare earth oxides.

3. The method for preparing the rare earth aluminum master alloy as described in claim 2, characterized in that, In condition ①, the rare earth elements include yttrium, scandium, lanthanum, neodymium, samarium, terbium, erbium, or thulium.

4. The method for preparing the rare earth aluminum master alloy as described in claim 2, characterized in that, In condition ①, the mass percentage of the rare earth element in the total mass of the rare earth aluminum raw material is 0.5% or more.

5. The method for preparing the rare earth aluminum master alloy as described in claim 2, characterized in that, In condition ②, the mass ratio of the metallic aluminum to the rare earth aluminum raw material is 1:(0.04-0.08).

6. The method for preparing the rare earth aluminum master alloy as described in claim 2, characterized in that, Step S1 satisfies one or more of the following conditions: ⑤ The mass percentage of the rare earth elements in the total mass of the rare earth aluminum raw materials is more than 1%; ⑥ The mass percentage of the aluminum element in the total mass of the rare earth aluminum raw material is 3%-15%; ⑦ The rare earth aluminum raw material also includes alkali metal elements, fluorine elements and oxygen elements; ⑧ The mass ratio of the metallic aluminum to the rare earth aluminum raw material is 1:(0.04-0.06). ⑨ The melting temperature is 880-1050℃; ⑩ The temperature of the aluminothermic reaction is 800-1200℃.

7. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑤, the mass percentage of the rare earth element in the total mass of the rare earth aluminum raw material is 1%-5%.

8. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑥, the mass percentage of the aluminum element accounts for 5%-10% of the total mass of the rare earth aluminum raw material.

9. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of the alkali metal element in the total mass of the rare earth aluminum raw material is 10%-20%.

10. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of the alkali metal element in the total mass of the rare earth aluminum raw material is 12%-15%.

11. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of the fluorine element in the total mass of the rare earth aluminum raw material is 50%-80%.

12. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of the fluorine element in the total mass of the rare earth aluminum raw material is 65%-70%.

13. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of oxygen element in the total mass of rare earth aluminum raw material is 5%-15%.

14. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑦, the mass percentage of oxygen element in the total mass of rare earth aluminum raw material is 10%-12%.

15. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition ⑧, the mass ratio of the metallic aluminum and rare earth aluminum raw materials is 1:0.04, 1:0.041, 1:0.045, 1:0.049, 1:0.051, 1:0.054, 1:0.057 or 1:0.

06.

16. The method for preparing the rare earth aluminum master alloy as described in claim 6, characterized in that, In condition 9, the melting temperature is 880°C, 900°C, 920°C, 950°C, or 1050°C.

17. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, Step S1 satisfies one or more of the following conditions: ①The aluminum metal includes aluminum ingots; ②The melting time is 10-30 min; ③ The melting process is carried out in the crucible of a medium-frequency induction melting furnace; ④ The melting process is carried out under the first stirring, and the interval of the first stirring is 5-10 min; the first stirring method includes electromagnetic stirring and / or mechanical stirring.

18. The method for preparing the rare earth aluminum master alloy as described in claim 17, characterized in that, In step S1, the melting time is 10-20 min.

19. The method for preparing the rare earth aluminum master alloy as described in claim 17, characterized in that, In condition ④, the interval between the first stirring is 5-8 minutes.

20. The method for preparing the rare earth aluminum master alloy as described in claim 17, characterized in that, The melting time is 10-15 min; And / or, in condition ④, the first stirring method includes mechanical stirring, and the mechanical stirring includes graphite rod stirring.

21. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, Step S2 satisfies one or more of the following conditions: ①The mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.03-0.18); ②The mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.03-0.08). ③ The heat preservation treatment time is 30-60 min; ④ The heat preservation process is carried out under the second stirring, and the interval between the second stirrings is 5-10 min; the second stirring method includes electromagnetic stirring and / or mechanical stirring; ⑤ The rare earth fluoride is yttrium fluoride, scandium fluoride, lanthanum fluoride, neodymium fluoride, samarium fluoride, terbium fluoride, erbium fluoride, or thulium fluoride; the rare earth elements in the rare earth fluoride are the same as those in the rare earth aluminum raw material. ⑥ The alkali metal halide is potassium fluoride, lithium fluoride, sodium fluoride, sodium fluoroaluminate, potassium fluorochlorate, or calcium fluoride; ⑦ The second mixture also includes rare earth oxides; the rare earth oxides are consistent with the rare earth elements in the rare earth fluorides.

22. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S2, the mass ratio of the aluminum metal to the alkali metal halide is 1:(0.03-0.07).

23. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S2, the heat preservation treatment time is 40-60 minutes.

24. The method for preparing the rare earth aluminum master alloy as described in claim 21, characterized in that, Step S2 satisfies one or more of the following conditions: ⑧ The mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.05-0.15); ⑨ The mass ratio of the metallic aluminum to the alkali metal halide is 1:(0.035-0.07). ⑩ The temperature for the heat preservation treatment is 900-1100℃; ⑪ The heat preservation treatment time is 40 min, 50 min or 60 min; ⑫ In condition ④, the second stirring method includes mechanical stirring, and the mechanical stirring includes graphite rod stirring; ⑬ In condition ⑧, the rare earth oxide is yttrium oxide, scandium oxide, lanthanum oxide, neodymium oxide, samarium oxide, terbium oxide, erbium oxide, or thulium oxide; ⑭ In condition ⑧, the mass ratio of the metallic aluminum to the rare earth oxide is 1:(0.002-0.02).

25. The method for preparing the rare earth aluminum master alloy as described in claim 21, characterized in that, In condition ①, the mass ratio of the metallic aluminum to the rare earth fluoride is 1:(0.05-0.13).

26. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, The temperature for the heat preservation treatment is 920-1070℃.

27. The method for preparing the rare earth aluminum master alloy as described in claim 24, characterized in that, In condition 14, the mass ratio of the metallic aluminum to the rare earth oxide is 1:(0.002-0.01).

28. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S3, the separation temperature is 750-900℃; And / or, the separation method includes removing rare earth aluminum slag from the surface of the second melt.

29. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S3, the separation temperature is 780-900℃.

30. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S3, the separation temperature is 780℃, 800℃, 810℃, 820℃ or 900℃.

31. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, Step S4 satisfies one or more of the following conditions: ①The cooling methods include water cooling, air cooling, or cooling with a cooler; ②The pouring temperature is 750-900℃; ③ The pouring speed is 0.25-0.3 L / s; ④ The time for the molten metal to cool to a completely solidified state is less than 20 seconds; ⑤ The time for the molten metal to cool to room temperature is 10-15 minutes.

32. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S4, the pouring temperature is 780-900℃.

33. The method for preparing the rare earth aluminum master alloy as described in claim 1, characterized in that, In step S4, the pouring temperature is 780℃, 800℃, 810℃, 820℃ or 900℃.

34. A rare earth aluminum master alloy, characterized in that, It is prepared by the method for preparing rare earth aluminum master alloy as described in any one of claims 1-33.

35. The rare earth aluminum master alloy as described in claim 34, characterized in that, The mass ratio of rare earth elements in the rare earth aluminum master alloy to the total mass of the rare earth aluminum master alloy is less than 10%.

36. The rare earth aluminum master alloy as described in claim 34, characterized in that, The mass ratio of rare earth elements in the rare earth aluminum master alloy to the total mass of the rare earth aluminum master alloy is greater than 1.5% and less than 8.5%.

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