Grain refiners, aluminum materials, preparation methods and applications

Abstract

This invention discloses a grain refiner, an aluminum material, a preparation method, and its uses. The preparation method of the grain refiner includes: (1) adding rare earth oxides and carbon-containing alumina powder to a salt solvent melt, stirring to form a liquid-solid mixture; cooling the liquid-solid mixture to obtain a precursor; (2) forming an aluminum melt from an aluminum ingot; adding potassium fluorotitanate and potassium fluoroborate to the aluminum melt and stirring, then adding the precursor obtained in step (1), continuing to stir and react until complete, removing the salt solvent melt to obtain an alloy solution; (3) sequentially refining, degassing, and slag removal from the alloy solution to obtain a slag-removed alloy solution, shaping the slag-removed alloy solution to obtain the grain refiner. The grain refiner of this invention has a fine-sized, dispersed, and uniformly composed grain refining phase.

Description

Technical Field

[0001] This invention relates to a grain refiner, aluminum material, preparation method, and applications. Background Technology

[0002] Grain refinement of aluminum alloys can result in a dense alloy structure, while also reducing the tendency for hot cracking and segregation in castings, lowering porosity, and thus improving the overall performance of the alloy. Currently, the most common and effective grain refinement method is the addition of grain refiners. However, the commonly used aluminum-titanium-boron (ATB) grain refiner suffers from reduced refining effect and duration due to the tendency of the TiB2 refining phase to agglomerate. Furthermore, the refining effect of ATB grain refiners is significantly reduced when refining high-silicon aluminum alloys (Si ≥ 3.0 wt.%), a phenomenon known as "Si poisoning." Aluminum-titanium-carbon (ATC) grain refiners, due to their finer TiC refining phase, uniform distribution, and resistance to agglomeration, as well as their better coherence with Al, offer superior refining effects compared to traditional ATB grain refiners and have attracted widespread attention and application. However, the poor wettability of C in Al makes preparation very difficult. The high cost of preparing ATC grain refiners through vigorous stirring or high-temperature reactions limits their widespread application.

[0003] In recent years, researchers have focused on developing novel grain refiners to address the aforementioned problems. For example, CN1108277374A, CN102784905B, CN111363936A, and CN114150173A disclose methods for preparing Al-Ti-CY, Al-Ti-C-Er, Al-Ti-C-La, and Al-Ti-C-Sc grain refiners, respectively. These methods use graphite powder or carbon powder as the carbon source. However, due to the poor wettability of C with Al, C is difficult to penetrate, and the process requires high temperatures and is costly. CN100467635C discloses a method for preparing an aluminum-titanium-carbon master alloy, using aluminum-carbon and aluminum-titanium alloys as raw materials. While the process is simple, it is costly and results in a large-sized refined phase. CN112899512B discloses a grain refiner for aluminum-titanium-carbon alloys and its preparation method, which uses nano-sized TiC as a carbon source. This method is costly, and the added TiC particles have poor wettability with Al, making it difficult to ensure uniform distribution of TiC in the Al melt. CN111996424B discloses a method for manufacturing TCB-Al seed alloys and a heritable aluminum alloy, using an Al-Al3BC master alloy as a carbon source. This master alloy is first prepared using powder metallurgy and then added to pure aluminum as a carbon source. However, this method has a long process and high cost.

[0004] CN118241081A discloses an aluminum-titanium-carbon-boron-cerium grain refiner, its preparation method, and its application. The grain refiner of this invention is composed of the following components: 3-5% titanium, 0.2-0.4% boron, 0.1-0.3% carbon, 2-6% cerium, and other impurities totaling ≤0.15%, with the balance being aluminum. The preparation method includes the following steps: aluminum powder, graphite powder, and potassium fluoride are mixed into a powder and divided into two portions; an aluminum-cerium master alloy is added to the aluminum melt for reaction, and after removing the slag, the temperature is raised to 1000-1200℃, and then the mixed powder is added in batches at intervals; after the reaction is completed, the temperature is lowered to 800-900℃, and an aluminum-boron master alloy is added to continue the reaction; a solvent is added for stirring and refining, the solvent being a mixture of potassium chloride, magnesium nitrate, sodium chloride, and calcium nitrate in a mass ratio of (5-10):(10-25):(1-3):(0.2-0.3); after refining and holding at heat, the mixture is cast to obtain the aluminum-titanium-carbon-boron-cerium grain refiner. The invention uses graphite powder as the carbon source and also employs an aluminum-boron intermediate alloy, which makes it difficult for carbon to penetrate, and the high temperature and high preparation cost also contribute to the high cost. Summary of the Invention

[0005] In view of this, one object of the present invention is to provide a method for preparing a grain refiner, which has good process repeatability, a simple method for introducing carbon sources, and is easier to integrate into molten aluminum. Another object of the present invention is to provide a grain refiner in which the refined phase is small in size, dispersed in distribution, and uniform in composition. A further object of the present invention is to provide a method for preparing an aluminum material. Yet another object of the present invention is to provide an aluminum material. A still another object of the present invention is to provide an application of the grain refiner.

[0006] On one hand, the present invention provides a method for preparing a grain refiner, comprising the following steps:

[0007] (1) Add 10-60 parts by weight of rare earth oxides and 5-30 parts by weight of carbon-containing alumina powder to 30-80 parts by weight of salt solvent melt, stir, and prepare a liquid-solid mixture; cool the liquid-solid mixture to obtain the precursor;

[0008] (2) Form an aluminum melt by taking 900 to 1000 parts by weight of aluminum ingots; add 150 to 250 parts by weight of potassium fluorotitanate and 40 to 70 parts by weight of potassium fluoroborate to the aluminum melt and stir, then add 20 to 50 parts by weight of the precursor obtained in step (1), continue stirring and reacting until complete, remove the salt solvent melt, and obtain an alloy solution.

[0009] (3) The alloy solution is refined, degassed and slag removed in sequence to obtain the alloy solution after slag removal. The alloy solution after slag removal is shaped to obtain a grain refiner.

[0010] According to the preparation method of the present invention, preferably, the rare earth element in the rare earth oxide is selected from one or more of lanthanum, cerium, yttrium, erbium, and scandium.

[0011] According to the preparation method of the present invention, preferably, the salt solvent melt is prepared by heating cryolite, sodium chloride and potassium chloride; wherein, based on the mass of the salt solvent melt, the content of cryolite is 65-85 wt%, the content of sodium chloride is 8-15 wt%, and the content of potassium chloride is 10-15 wt%.

[0012] According to the preparation method of the present invention, preferably, aluminum citrate is prepared under a vacuum of 10... -2 Heating at 8–15 °C / min to 750–850 °C and holding for 20–60 min under Pa conditions forms carbon-containing alumina powder.

[0013] According to the preparation method of the present invention, preferably, the alloy nucleation phases of the grain refiner include TiAl3 phase, C-doped TiB2, B-doped TiC phase, and Ti2Al phase. 20 One or more of the RE phases, with the matrix phase being the α-Al phase.

[0014] According to the preparation method of the present invention, preferably, the size of the TiAl3 phase is less than or equal to 20 μm; the size of the C-doped TiB2 phase is less than or equal to 1 μm; the size of the B-doped TiC phase is less than or equal to 1 μm; and the size of the Ti2Al phase is less than or equal to 1 μm. 20 The size of the RE phase is less than or equal to 10 μm.

[0015] On the other hand, the present invention also provides a grain refiner prepared according to the method described above.

[0016] Furthermore, the present invention also provides a method for preparing aluminum material, comprising the following steps:

[0017] Aluminum raw materials or aluminum-silicon alloys are melted to obtain a melt; a grain refiner as described above is added to the melt and mixed to obtain a molten metal; the molten metal is refined, degassed, and slag is removed, then cooled, and then solidified to obtain aluminum material.

[0018] The amount of the grain refiner added is 0.05 to 0.6% of the melt mass.

[0019] In another aspect, the present invention also provides an aluminum material prepared by the preparation method described above.

[0020] In another aspect, the present invention provides the use of the grain refiner described above in refining the grain size of aluminum or its alloys.

[0021] The grain refiner of this invention produces grains with small, dispersed, and uniformly composed refinement phases. The preparation method of this grain refiner exhibits high effective element yield and demonstrates better refining effect compared to grain refiners prepared using existing technologies. Furthermore, the preparation process is simpler and less costly. The preparation method of this invention involves in-situ generation of C-doped TiB2 phase and B-doped TiC, TiAl3, and Ti2Al phases. 20 The RE phase method uses calcined aluminum citrate as the carbon source, making it easier for carbon to enter the molten aluminum. Rare earth elements are added in oxide form, which is also less costly. C-doped TiB2 phase can reduce the size of the refined TiB2 phase, decrease its growth and agglomeration tendency, and suppress the "Si poisoning" phenomenon in the grain refiner. B-doped TiC can prevent TiC growth and enhance the heterogeneous nucleation ability of the refined TiC phase. Rare earth purification refiner alloys, and the rare earth compounds formed with Al and other impurities, can also act as nucleation sites for α-Al, thus playing a grain refining role. The grain refiner prepared by this invention has a wide variety of effective nucleation sites, a high number density, and high refining efficiency. Attached Figure Description

[0022] Figure 1 The images are XRD patterns of Examples 1 and 2.

[0023] Figure 2a The image shows the microstructure of the TiB2 phase in the C-doped TiB2 phase of the Al-Ti-BC-LaCe grain refiner in Example 1.

[0024] Figure 2b The elemental distribution diagram of the C-doped TiB2 phase in the Al-Ti-BC-LaCe grain refiner of Example 1 is shown.

[0025] Figure 2c for Figure 2b A magnified view of a portion of the image.

[0026] Figure 3a The image shows the morphology of the B-doped TiC phase in the Al-Ti-BC-LaCe grain refiner of Example 1.

[0027] Figure 3b The image shows the elemental distribution of the B-doped TiC phase in the Al-Ti-BC-LaCe grain refiner of Example 1.

[0028] Figure 3c for Figure 3b A magnified view of a portion of the image.

[0029] Figure 4 This is a SEM scan of Example 1.

[0030] Figure 5Metallographic structures of refined aluminum obtained from aluminum raw materials, Experimental Example 1, Experimental Example 2, Experimental Example 3, Experimental Example 4, and Comparative Experimental Example 1 are shown.

[0031] Figure 6 The image shows the metallographic structure of the aluminum-silicon alloy from Experimental Example 5. Among them, Figure 6 a is the metallographic structure diagram before refinement. Figure 6 b is the refined metallographic structure diagram. Detailed Implementation

[0032] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] <Preparation method of grain refiner>

[0034] The preparation method of the grain refiner of the present invention includes the following steps: (1) preparation of precursor; (2) preparation of alloy solution; (3) preparation of grain refiner.

[0035] Preparation of precursors

[0036] This invention utilizes cryolite, sodium chloride, and potassium chloride to form a salt solvent melt, which is then used as a solvent to form a precursor containing rare earth elements and carbon. This facilitates the dispersion of rare earth elements and carbon, improves reaction efficiency, and helps prevent the precipitation of finer phases.

[0037] Rare earth oxides and carbon-containing alumina powder are added to a salt solvent melt, mixed, and cooled to obtain the precursor.

[0038] The rare earth element in the rare earth oxide may be selected from one or more of lanthanum, cerium, yttrium, erbium, and scandium; preferably from one or more of lanthanum, cerium, and yttrium; more preferably from lanthanum and / or cerium. The mass of the rare earth oxide may be 10 to 60 parts by weight; preferably 15 to 50 parts by weight; more preferably 30 to 45 parts by weight.

[0039] In some embodiments, the rare earth oxides may be lanthanum oxide and cerium oxide; wherein the mass of lanthanum oxide may be 5 to 20 parts by weight, preferably 10 to 18 parts by weight, more preferably 10 to 15 parts by weight. The mass of cerium oxide may be 5 to 40 parts by weight, preferably 15 to 35 parts by weight, more preferably 20 to 30 parts by weight.

[0040] Aluminum citrate (C6H5AlO7) can be processed under a vacuum of 10... -2Alumina powder containing carbon is formed by calcination at Pa. The calcination temperature can be 750–850℃, preferably 780–850℃, and more preferably 800–820℃. The heating rate can be 8–15℃ / min, preferably 10–13℃ / min. The holding time can be 20–60 min, preferably 25–50 min, and more preferably 30–40 min.

[0041] The amount of carbon-containing alumina powder used can be 5 to 30 parts by weight, preferably 10 to 25 parts by weight, and more preferably 10 to 20 parts by weight.

[0042] The mass of the salt solvent melt can be 30-80 parts by weight, preferably 40-70 parts by weight, and more preferably 40-60 parts by weight. Based on the total weight of the salt solvent melt, cryolite is 65-85 wt%, sodium chloride is 8-15 wt%, and potassium chloride is 10-15 wt%. Preferably, based on the total weight of the salt solvent melt, cryolite is 70-80 wt%, sodium chloride is 10-15 wt%, and potassium chloride is 11-14 wt%. More preferably, based on the total weight of the salt solvent melt, cryolite is 72-75 wt%, sodium chloride is 12-14 wt%, and potassium chloride is 13-14 wt%.

[0043] Preparation of alloy solution

[0044] Aluminum ingots are formed into aluminum melt; potassium fluorotitanate and potassium fluoroborate are added to the aluminum melt and stirred, then the obtained precursor is added, and the reaction is continued to be stirred until complete. The salt solvent melt is removed to obtain an alloy solution.

[0045] The mass of the aluminum melt can be 900 to 1000 parts by weight, preferably 920 to 980 parts by weight, and more preferably 940 to 960 parts by weight.

[0046] The mass of potassium fluorotitanate can be 150 to 250 parts by weight, preferably 160 to 230 parts by weight, and more preferably 170 to 200 parts by weight.

[0047] The mass of potassium fluoroborate can be 40 to 70 parts by weight, preferably 45 to 68 parts by weight, and more preferably 48 to 65 parts by weight.

[0048] The added precursor can be 20 to 50 parts by weight, preferably 25 to 48 parts by weight, and more preferably 27 to 46 parts by weight.

[0049] Preparation of grain refiner

[0050] The alloy solution is sequentially refined, degassed, and slag-removed to obtain a slag-removed alloy solution; the slag-removed alloy solution is then shaped to obtain a grain refiner.

[0051] In some embodiments, the alloy solution after slag removal can be cast into ingots to obtain a grain refiner.

[0052] In other embodiments, the alloy solution after slag removal can be cast into a rod and then extruded into a thin rod to obtain a grain refiner. The extrusion temperature can be 300–500°C, preferably 350–450°C, and more preferably 380–400°C. The extrusion speed can be 15–30 mm / min, preferably 20–28 mm / min, and more preferably 20–25 mm / min.

[0053] In some other embodiments, the alloy solution after slag removal can be cast into a rod, extruded into a thin rod, and then coiled to obtain a grain refiner. The continuous casting and rolling temperature can be 400–600°C, preferably 450–550°C, and more preferably 480–520°C. The continuous casting and rolling speed can be 1–3 m / min, preferably 1.2–2.5 m / min, and more preferably 1.5–2.0 m / min.

[0054] <Grain refiner>

[0055] The grain refiner of the present invention comprises Ti, B, C, Re, and Al. Preferably, the grain refiner of the present invention is composed of the aforementioned elements. Wherein, Re represents a rare earth element.

[0056] The Ti content can be 3.1 to 4.5 wt%, preferably 3.3 to 4.4 wt%, and more preferably 3.4 to 4.0 wt%.

[0057] The content of B can be 0.41 to 2.0 wt%, preferably 0.42 to 1.0 wt%, and more preferably 0.42 to 0.8 wt%.

[0058] The content of C can be 0.01 to 0.2 wt%, preferably 0.05 to 0.15 wt%, and more preferably 0.08 to 0.13 wt%.

[0059] The Re content can be 0.2 to 1.5 wt%, preferably 0.4 to 1.2 wt%, and more preferably 0.5 to 1.1 wt%.

[0060] The grain refiner of the present invention comprises alloy nucleation phases including TiAl3 phase, C-doped TiB2, B-doped TiC phase, and Ti2Al phase. 20 One or more of the RE phases, with the matrix phase being the α-Al phase.

[0061] The size of the TiAl3 phase is less than or equal to 20 μm, preferably less than or equal to 10 μm; the size of the C-doped TiB2 phase is less than or equal to 1 μm, preferably less than or equal to 0.5 μm; the size of the B-doped TiC phase is less than or equal to 1 μm, preferably less than or equal to 0.5 μm; Ti2Al 20 The size of the RE phase is less than or equal to 10 μm, preferably less than or equal to 5 μm.

[0062] <Preparation Methods of Aluminum Materials>

[0063] The present invention also provides a method for preparing aluminum material, comprising the following steps:

[0064] Aluminum raw materials are melted to obtain aluminum melt; the above-mentioned grain refiner is added to the aluminum melt and mixed to obtain molten metal; the molten metal is refined, degassed, and slag is removed, then cooled, and then solidified to obtain refined aluminum material.

[0065] In some embodiments, the aluminum material is pure aluminum, and in other embodiments, the aluminum material is an aluminum-silicon alloy; wherein the silicon content in the aluminum-silicon alloy is greater than or equal to 5 wt%, for example, it can be 7 wt%.

[0066] The refining agent can be any known in the art, for example, the refining agent can be selected from 25% Na3SiF6-12.5% ​​KCl-62.5% NaCl, 10% Na3AlF6-10% KCl-50% NaCl-30% NaF, or 15% Na3AlF6-45% NaCl-40% NaF.

[0067] In this invention, the amount of grain refiner added can be 0.05 to 0.6% of the mass of the aluminum melt; preferably, the amount of grain refiner added is 0.10 to 0.5% of the mass of the aluminum melt; more preferably, the amount of grain refiner added is 0.10 to 0.3% of the mass of the aluminum melt.

[0068] <Aluminum Materials>

[0069] The aluminum material of the present invention is prepared by the method described above. The grain size of the aluminum material prepared by the method of the present invention can be refined to below 90 μm; preferably, it can be refined to below 80 μm.

[0070] <Applications>

[0071] This invention also provides the use of the above-mentioned grain refiner in refining the grain size of aluminum or aluminum alloys. The aluminum alloy can be an aluminum-silicon alloy. The composition of the aluminum-silicon alloy is as described above and will not be repeated here.

[0072] <Analytical Methods>

[0073] Elemental analysis: Analyzed using a Shimadzu ICPS-8100 inductively coupled plasma optical generator (ICPS).

[0074] SEM analysis: Microstructure analysis was performed using a Zeiss SIGMA500 microscope from Germany;

[0075] XRD analysis: Phase composition analysis was performed using a Bruker AXSD8 X-ray diffractometer manufactured by Bruker GmbH, Germany.

[0076] Metallographic analysis: The microstructure was observed and analyzed using a Zeiss Axio Imager 2 metallographic microscope;

[0077] Grain size measurement: Grain size was measured using the metallographic image analysis software AON-STUDIO according to the standard for average grain size of metals (GB / T 6394-2017) - intercept method.

[0078] Example 1

[0079] Aluminum citrate (C6H5AlO7) was placed in a quartz container and subjected to a vacuum of 10... -2 Heating to 800℃ at 10℃ / min under Pa conditions and holding for 30min forms carbon-containing alumina powder (carbon content approximately 25%); 200g cryolite, 35g sodium chloride and 37g potassium chloride are placed in a graphite crucible and heated to prepare a salt solvent melt.

[0080] 15g of lanthanum oxide, 30g of cerium oxide and 15g of carbon-containing alumina powder were added to 40g of salt solvent melt and stirred to form a liquid-solid mixture. The liquid-solid mixture was then cooled to obtain the precursor.

[0081] 944g of aluminum ingot was formed into an aluminum melt, and the temperature of the aluminum melt was controlled at 900℃. 200g of potassium fluorotitanate and 64g of potassium fluoroborate were added to the aluminum melt in batches and stirred. After the potassium fluorotitanate and potassium fluoroborate were completely melted, 27g of precursor was added. After the precursor was completely melted, the reaction was continued with stirring to remove the salt solvent from the melt, and an alloy solution was obtained.

[0082] The alloy solution was sequentially refined, degassed, and slag removed, then cooled to 730℃ and cast into a rod. The rod was then hot-extruded into a thin rod with a diameter of 9.5 mm, and then coiled. The continuous casting and rolling process was carried out at a temperature of 500℃ and a speed of 1.5 m / min, resulting in a product grain refiner.

[0083] Example 2

[0084] Aluminum citrate (C6H5AlO7) was placed in a quartz container and subjected to a vacuum of 10... -2Heating to 800℃ at 10℃ / min under Pa and holding for 30min forms carbon-containing alumina powder; 200g cryolite, 35g sodium chloride and 37g potassium chloride are placed in a graphite crucible and heated to prepare a salt solvent melt.

[0085] 10g of lanthanum oxide, 20g of cerium oxide and 10g of carbon-containing alumina powder were added to 60g of salt solvent melt and stirred to form a liquid-solid mixture. The liquid-solid mixture was cooled to obtain the precursor.

[0086] 950g of aluminum ingot was formed into an aluminum melt, and the temperature of the aluminum melt was controlled at 900℃. 170g of potassium fluorotitanate and 49g of potassium fluoroborate were added to the aluminum melt in batches and stirred. After the potassium fluorotitanate and potassium fluoroborate were completely melted, 46g of precursor was added. After the precursor was completely melted, the reaction was continued to be stirred to remove the salt solvent from the melt, and an alloy solution was obtained.

[0087] The alloy solution was successively refined, degassed, and slag removed, and then cooled to 730°C and cast into ingots to obtain a product grain refiner.

[0088] Example 3

[0089] Aluminum citrate (C6H5AlO7) was placed in a quartz container and subjected to a vacuum of 10... -2 Heating to 800℃ at 10℃ / min under Pa and holding for 30min forms carbon-containing alumina powder; 200g cryolite, 35g sodium chloride and 37g potassium chloride are placed in a graphite crucible and heated to prepare a salt solvent melt.

[0090] 10g of lanthanum oxide, 20g of cerium oxide and 20g of carbon-containing alumina powder were added to 50g of salt solvent melt and stirred to form a liquid-solid mixture. The liquid-solid mixture was then cooled to obtain the precursor.

[0091] 954g of aluminum ingot was formed into an aluminum melt, and the temperature of the aluminum melt was controlled at 900℃. 178g of potassium fluorotitanate and 51g of potassium fluoroborate were added to the aluminum melt in batches and stirred. After the potassium fluorotitanate and potassium fluoroborate were completely melted, 20g of precursor was added. After the precursor was completely melted, the reaction was continued with stirring to remove the salt solvent from the melt, and an alloy solution was obtained.

[0092] The alloy solution was sequentially refined, degassed, and slag removed, then cooled to 730℃ and cast into a rod. The rod was then hot-extruded into a thin rod with a diameter of 9.5 mm; the extrusion temperature was 400℃ and the extrusion speed was 20 mm / min, yielding a grain refiner.

[0093] Example 4

[0094] Aluminum citrate (C6H5AlO7) was placed in a quartz container and subjected to a vacuum of 10...-2 Heating to 800℃ at 10℃ / min under Pa and holding for 30min forms carbon-containing alumina powder; 200g cryolite, 35g sodium chloride and 37g potassium chloride are placed in a graphite crucible and heated to prepare a salt solvent melt.

[0095] 15g of lanthanum oxide and 10g of carbon-containing alumina powder were added to 75g of salt solvent melt and stirred to form a liquid-solid mixture. The liquid-solid mixture was then cooled to obtain the precursor.

[0096] 945g of aluminum ingot was formed into an aluminum melt, and the temperature of the aluminum melt was controlled at 900℃. 213g of potassium fluorotitanate and 63g of potassium fluoroborate were added to the aluminum melt in batches and stirred. After the potassium fluorotitanate and potassium fluoroborate were completely melted, 45g of precursor was added. After the precursor was completely melted, the reaction was continued with stirring to remove the salt solvent from the melt, and an alloy solution was obtained.

[0097] The alloy solution was successively refined, degassed, and slag removed, and then cooled to 730°C and cast into ingots to obtain a product grain refiner.

[0098] The chemical composition of the grain refiners obtained in Examples 1-4 was analyzed using inductively coupled plasma atomic emission spectrometry (ICP). The results are shown in Table 1.

[0099] Table 1

[0100]

[0101] The XRD patterns of Examples 1 and 2 are shown in the figure. Figure 1 .from Figure 1 It can be seen that the Al-Ti-BC-RE grain refiner mainly consists of α-Al phase, TiB2 phase, TiC phase, TiAl3 phase, and Ti2Al phase. 20 The composition is LaCe phase.

[0102] The morphology of the C-doped TiB2 phase in the Al-Ti-BC-LaCe grain refiner of Example 1 is shown in the figure. Figure 2a .from Figures 2a-2c It can be seen that the TiB2 phase particles in the Al-Ti-BC-LaCe grain refiner are relatively small, about 400 nm in size, and have C element enrichment on the surface, which hinders their growth and aggregation.

[0103] The morphology of the B-doped TiC phase in the Al-Ti-BC-LaCe grain refiner of Example 1 is shown in the figure. Figure 3a .from Figures 3a-3c As can be seen, the TiC particles in the Al-Ti-BC-LaCe grain refiner are relatively small, about 200 nm in size, and the surface is enriched with B element, which hinders their growth.

[0104] The SEM scan image of Example 1 is shown below. Figure 4 .from Figure 4 As can be seen from the microstructure of the Al-Ti-BC-RE alloy prepared in Example 1, there are gray blocky TiAl3 phases with an average size of less than 20 μm; and bright white Ti2Al... 20 RE phases are distributed around the TiAl3 phase and on the matrix, with an average size of less than 5 μm; finely dispersed C-doped TiB2 and B-doped TiC phases are also distributed in the matrix, with an average size of less than 0.5 μm.

[0105] Comparative Example 1

[0106] Aluminum citrate (C6H5AlO7) was placed in a quartz container and subjected to a vacuum of 10... -2 Heating to 800℃ at 10℃ / min under Pa and holding for 30min forms carbon-containing alumina powder; 200g cryolite, 35g sodium chloride and 37g potassium chloride are placed in a graphite crucible and heated to prepare a salt solvent melt.

[0107] 10g of carbon-containing alumina powder was added to a salt solvent melt and stirred to form a liquid-solid mixture. The liquid-solid mixture was then cooled to obtain the precursor.

[0108] 945g of aluminum ingot was formed into an aluminum melt, and the temperature of the aluminum melt was controlled at 900℃. 213g of potassium fluorotitanate and 63g of potassium fluoroborate were added to the aluminum melt in batches and stirred. After the potassium fluorotitanate and potassium fluoroborate were completely melted, 45g of precursor was added. After the precursor was completely melted, the reaction was continued with stirring to remove the salt solvent from the melt, and an alloy solution was obtained.

[0109] The alloy solution was successively refined, degassed, and slag removed, and then cooled to 730°C and cast into ingots to obtain a product grain refiner.

[0110] Experimental Example 1

[0111] Aluminum raw materials are melted to obtain aluminum melt; the grain refiner prepared in Example 1 is added to the aluminum melt and mixed evenly to obtain molten metal; a refining agent is added to the molten metal, and argon gas is simultaneously introduced into the molten metal for degassing using a degasser for 5 minutes. Slag is removed, and then the temperature is lowered to 720°C for solidification and shaping to obtain refined aluminum (also referred to as aluminum material). The mass of the grain refiner added is 0.1% of the mass of the aluminum melt.

[0112] Experiment Example 2

[0113] The difference from Experimental Example 1 is that the grain refiner prepared in Example 2 was used.

[0114] Experimental Example 3

[0115] The difference from Experimental Example 1 is that the grain refiner prepared in Example 3 was used.

[0116] Experiment Example 4

[0117] The difference from Experimental Example 1 is that the grain refiner prepared in Example 4 was used.

[0118] Experimental Example 5

[0119] The difference from Experimental Example 1 is that the aluminum raw material was replaced with an aluminum-silicon alloy (Al-7Si), and the grain refiner added was 0.5% of the mass of the aluminum-silicon melt.

[0120] Comparative Experiment Example 1

[0121] The difference from Experimental Example 1 is that the grain refiner prepared in Comparative Example 1 was used.

[0122] Metallographic diagrams of the aluminum raw material, Experimental Examples 1-4, and the refined aluminum obtained from Comparative Experiment 1 are shown below. Figure 5 (A, B, C, D, E, F in sequence). The grain size of aluminum refined by the grain refiner obtained in the embodiments of this application is significantly reduced.

[0123] The grain size measurement results of the refined aluminum obtained from aluminum raw materials, Experimental Examples 1-4, and Comparative Experimental Example 1 are shown in Table 2.

[0124] Table 2

[0125]

[0126] As shown in Table 2, the grain size of blank aluminum (i.e., unrefined aluminum raw material) reached 486.1 μm. However, the grain size of aluminum refined using the grain refiner of this invention can be reduced to approximately 80 μm. While the grain size of aluminum refined with the grain refiner in Comparative Experiment 1 showed some refining effect, the effect was not as good as that of the grain refiner of this invention.

[0127] The grain size of the unrefined aluminum-silicon alloy was 176.46 μm, while the grain size of the refined aluminum-silicon alloy obtained in Experimental Example 5 was 77.78 μm. The metallographic structure of the refined aluminum-silicon alloy obtained in Experimental Example 5 is shown below. Figure 6 b. From Figure 6 a and Figure 6 b shows that after being refined by the grain refiner, the microstructure changed from coarse diameter to fine equiaxed crystals, indicating that the Al-Ti-BC-RE grain refiner prepared in this application has a strong grain refinement effect on Al-7Si alloy, solving the "Si poisoning" problem of traditional Al-Ti-B grain refiner.

[0128] This invention is not limited to the above-described embodiments. Any modifications, improvements, or substitutions that can be conceived by those skilled in the art without departing from the essential content of this invention fall within the scope of this invention.

Claims

1. A method for preparing a grain refiner, characterized in that, Includes the following steps: (1) Add 10-60 parts by weight of rare earth oxides and 5-30 parts by weight of carbon-containing alumina powder to 30-80 parts by weight of salt solvent melt, stir, and prepare a liquid-solid mixture; cool the liquid-solid mixture to obtain the precursor; the carbon-containing alumina powder is prepared by the following method: aluminum citrate is heated under a vacuum of 10 -2 Heating at 8–15 °C / min to 750–850 °C and holding for 20–60 min under Pa conditions forms carbon-containing alumina powder. (2) Form an aluminum melt by taking 900-1000 parts by weight of aluminum ingots; add 150-250 parts by weight of potassium fluorotitanate and 40-70 parts by weight of potassium fluoroborate to the aluminum melt and stir, then add 20-50 parts by weight of the precursor obtained in step (1), continue stirring and reacting until complete, remove the salt solvent melt, and obtain an alloy solution. (3) The alloy solution is refined, degassed and slag removed in sequence to obtain the alloy solution after slag removal. The alloy solution after slag removal is shaped to obtain a grain refiner.

2. The preparation method according to claim 1, characterized in that, The rare earth elements in the rare earth oxides are selected from one or more of lanthanum, cerium, yttrium, erbium, and scandium.

3. The preparation method according to claim 1, characterized in that, The salt solvent melt is prepared by heating cryolite, sodium chloride, and potassium chloride; wherein, based on the mass of the salt solvent melt, the content of cryolite is 65-85 wt%, the content of sodium chloride is 8-15 wt%, and the content of potassium chloride is 10-15 wt%.

4. The preparation method according to claim 1, characterized in that, The alloy nucleation phases of the grain refiner include TiAl3 phase, C-doped TiB2, B-doped TiC phase, and Ti2Al phase. 20 One or more of the RE phases, with the matrix phase being the α-Al phase.

5. The preparation method according to claim 4, characterized in that, The size of the TiAl3 phase is less than or equal to 20 μm; the size of the C-doped TiB2 phase is less than or equal to 1 μm; the size of the B-doped TiC phase is less than or equal to 1 μm; and the size of the Ti2Al phase is less than or equal to 1 μm. 20 The size of the RE phase is less than or equal to 10 μm.

6. A grain refiner, characterized in that, It is prepared by the method described in any one of claims 1 to 5.

7. A method for preparing an aluminum material, characterized in that, Includes the following steps: Aluminum raw materials or aluminum-silicon alloys are melted to obtain a melt; the grain refiner described in claim 6 is added to the melt and mixed to obtain a molten metal; the molten metal is refined, degassed, and slag is removed, then cooled, and then solidified to obtain aluminum material. The amount of the grain refiner added is 0.05 to 0.6% of the melt mass.

8. An aluminum material, characterized in that, It is prepared by the preparation method described in claim 7.

9. Use of the grain refiner as described in claim 6 in refining the grain size of aluminum or its alloys.

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