An Al-Ti-C-Ce master alloy using titanium carbide as both Ti and C sources, its preparation method, and its applications.

Abstract

This invention discloses an Al-Ti-C-Ce master alloy using titanium carbide as both Ti and C sources, its preparation method, and its application. Titanium carbide powder is mixed with aluminum powder and ball-milled to obtain an Al-coated TiC core-shell composite powder. The core-shell composite powder is pressed into preforms. These preforms are then pressed into the bottom of molten aluminum in batches using graphite bell jars. The mixture is first held at 760-850℃, then cooled to 700-750℃. An Al-30Ce master alloy is then added, followed by a second holding period. The mixture is then slag-removed and refined, and finally cast into a mold to obtain the Al-Ti-C-Ce master alloy. The Al-Ti-C-Ce master alloy provided by this invention refines the grain size of A356 alloy to 106 μm (ASTM grade 5), and even in low-content systems, a grain size refinement level of less than 120 μm can be maintained.

Description

Technical Field

[0001] This invention relates to the field of refining agent technology, specifically to an Al-Ti-C-Ce master alloy using titanium carbide as both Ti and C sources, its preparation method, and its application. Background Technology

[0002] Aluminum alloys are increasingly widely used in various fields of modern society, and the demand for their performance is becoming more and more important. Therefore, achieving high-quality as-cast microstructures is crucial. Research shows that when aluminum-based alloys obtain a uniform and refined equiaxed grain structure, their mechanical strength, plastic deformation capacity, and formability all reach optimal levels. Currently, the most widely used method for refining materials is the addition of grain refiners.

[0003] Al-Ti-C master alloys, as an important component of aluminum alloy grain refiners, have seen significant progress in their preparation processes, grain refinement mechanisms, and applications since their initial proposal in the 1970s. The development of Al-Ti-C master alloys began with the need to improve upon traditional Al-Ti-B grain refiners. Banerji et al. first proposed in 1983 the idea of ​​using TiC particles as heterogeneous nucleation cores for α-Al. Studies have shown that the mismatch between the lattice constant of TiC (a=0.432 nm) and α-Al (a=0.404 nm) is only 6.9%, significantly better than TiB's 8.6%, indicating higher nucleation efficiency. However, current Al-Ti-C grain refiner preparation processes still face challenges such as extremely poor wettability between the carbon source and molten aluminum, difficulty in combining the carbon source with Ti atoms in the molten aluminum to generate a sufficient number of TiC particles, uneven TiC particle distribution, and severe agglomeration, limiting their industrial application. Summary of the Invention

[0004] To address the aforementioned technical problems, the first objective of this invention is to provide a method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source.

[0005] The second objective of this invention is to provide an Al-Ti-C-Ce master alloy prepared by the above-described preparation method.

[0006] The third objective of this invention is to provide an application of the Al-Ti-C-Ce master alloy prepared by the above preparation method. Using the Al-Ti-C-Ce master alloy as a grain refiner can significantly improve the grain structure of aluminum-silicon alloys and has excellent anti-poisoning and anti-fading properties, thus playing an effective grain refinement role in aluminum-silicon alloys.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] This invention discloses a method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both Ti and C sources. The method involves ball milling titanium carbide powder and aluminum powder to obtain an Al-coated TiC core-shell composite powder. The Al-coated TiC core-shell composite powder is then pressed into preforms. These preforms are pressed into the bottom of molten aluminum in batches using a graphite bell jar. The mixture is then held at 760-850°C for the first time, then cooled to 700-750°C. An Al-30Ce master alloy is then added, followed by a second holding period. The mixture is then slag-refined and poured into a mold to obtain the Al-Ti-C-Ce master alloy.

[0009] The Al-Ti-C-Ce master alloy has the following composition by mass percentage: Ti: 0.5-7%, C: 0.5-2%, Ce: 0.05-1%, with the balance being Al.

[0010] The preparation method of this invention involves first mixing and ball-milling titanium carbide powder and aluminum powder to obtain an Al-coated TiC core-shell structured composite powder, which is then pressed into a preform. The preform is then added to molten aluminum, where an interfacial reaction occurs between the preform surface and the molten aluminum: TiC + 3Al → TiAl3 + C. Next, an Al-3OCe master alloy is added, resulting in the reaction 2Al3Ti + Ce + 14Al → Al. 20 The reaction of Ti₂Ce allows the released Ti to further react with Al to regenerate Al₃Ti, ultimately resulting in the Al-Ti-C-Ce master alloy prepared in this invention having TiC, Al₃Ti, and Al phases. 20 Ti2Ce-dominant, serving as novel heterogeneous nucleation sites, refined the grains, and Al 20 The grain boundary pinning effect of Ti2Ce inhibits grain boundary slip and improves the high-temperature elongation of the material.

[0011] In this invention, TiC is used instead of Ti and C sources, eliminating the need for strong exothermic reactions to synthesize TiC on-site and avoiding the growth of harmful Al4C3 and Ce2C phases. However, using TiC powder directly as raw material requires first mixing and ball milling titanium carbide powder with aluminum powder to obtain a core-shell structured composite powder with Al coating TiC. If the coating structure is not formed, gravity segregation will occur, causing TiC to sink and form local high hardness. The contact angle between TiC and aluminum is greater than 120°, and the powder is exposed on the surface of the melt, resulting in floating loss and oxidation to form TiO2 / Al2O3. In addition, a preform needs to be added to the aluminum melt first, and after holding it at a certain temperature for a period of time, Al-30Ce master alloy is added. If the preform and Al-30Ce master alloy are added to the aluminum melt simultaneously, Ce will react with TiC to form a hard and brittle Ce2C phase, resulting in severe Ce burn-off.

[0012] In the first stage of heat preservation, a slightly higher temperature is used to allow TiC and aluminum to fully react and form Al3Ti. Then, the temperature is slightly lowered before adding an Al-30Ce master alloy, which allows Ce to preferentially react with Al3Ti to undergo a peritectic reaction to form Al. 20 Ti2Ce.

[0013] In a preferred embodiment, the titanium carbide powder has a particle size of 1.0-2.0 μm, and the aluminum powder has a particle size of 45-75 μm.

[0014] Experiments have shown that the optimal performance is achieved when the particle size of titanium carbide powder and aluminum powder is controlled within the above-mentioned range. If the particle size of titanium carbide powder is too large, the coating will be uneven, resulting in exposed TiC. If the particle size is too small, it is easy to agglomerate. If the particle size of aluminum powder is too large, the aluminum powder will not be ductile enough and cannot completely coat the particles. If the particle size is too small, it is also easy to agglomerate.

[0015] In a preferred embodiment, the titanium carbide powder is first dried in a vacuum environment at 100-200℃ for 2-4 hours, with a vacuum degree ≤10. -2 Pa. Vacuum drying of titanium carbide powder is not only a physical removal of water, but also a core pretreatment to block surface chemical corrosion and ensure nano-dispersion and interfacial reaction. If TiC adsorbs water molecules and forms TiO2-OH, its contact angle is large, and ball milling due to water absorption will cause agglomeration.

[0016] In a preferred embodiment, the TiC:Al composite powder coated with Al has a mass ratio of TiC:Al of 1:2-4. In this invention, the mass ratio of TiC to Al in the core-shell composite powder needs to be effectively controlled. If TiC is excessive (>1:2), the free TiC reacts with Ce to form Ce₂C₃, leading to an increase in the aluminum loss rate of Ce. Furthermore, the aluminum coating layer becomes thinner, and the melt cannot completely wet the powder. If Al is excessive (<1:4), the excess aluminum consumes cerium to form CeAl₄, resulting in a reduction in effective Ce and a deterioration in the refining effect.

[0017] In a preferred embodiment, the ball mill rotation speed is 150-250 r / min, preferably 150-220 r / min, the ball milling time is 30-60 min, the ball-to-material ratio is 10-15:1, preferably 10-12:1, and the grinding ball material is WC-Co.

[0018] Because Al is a soft metal, it easily undergoes plastic deformation under the high-energy collisions of ball milling, forming thin flakes or flat particles. TiC, on the other hand, is a hard ceramic and primarily serves as a core to maintain its shape during ball milling. Therefore, ball milling allows Al to be deformed through repeated collisions, and under mechanical force, the deformed Al adheres tightly to the TiC surface. Furthermore, the ball milling process promotes physical / chemical bonding between the Al and TiC interfaces, ultimately forming a coating layer on the TiC surface. The ball milling process reduces the contact angle of TiC with the pre-coated Al layer in the molten aluminum, whereas the contact angle of free graphite in traditional processes is larger, leading to cerium enrichment at the interface and the formation of CeC2 inclusions. Ball milling also improves the reactivity of the raw material powder, making it more readily reactable in the melt. It yields Al-coated TiC core-shell composite powders, preferentially generating AlTi3 and suppressing the formation of harmful Al4C3 phases. The direct addition of TiC also significantly improves Ce utilization. Simultaneously, high-energy ball milling improves powder dispersibility, ensuring uniform distribution of the reaction throughout the melt.

[0019] However, to obtain Al-coated TiC core-shell composite powder, it is necessary to control the milling speed, time, and ball-to-material ratio. The energy should be sufficient to drive Al deformation without excessively damaging the TiC structure, allowing Al to deform preferentially and coat the hard TiC. If the milling time is too short, the coating will be incomplete, and the TiC particles will not be fully coated by Al, forming a mixed structure rather than a core-shell structure. If the time is too long, it may lead to excessive deformation / cold welding of Al, forming large particles, and also increase the risk of oxidation. If the milling speed is too fast or too slow, Al-coated TiC cannot be obtained. This is because if the speed is too slow, there is insufficient energy, and Al is difficult to plastically deform. If the speed is too fast, local overheating will cause Al to stick together or partially melt, destroying the core-shell structure; it may even cause TiC to break or Al to oxidize. The ball-to-material ratio is also important. If it is too low, there is insufficient grinding media and low coating efficiency. If it is too high, excessive impact will cause TiC to break or Al to be excessively cold-welded.

[0020] In a preferred embodiment, the particle size of the Al-coated TiC core-shell composite powder is 0.8-1 μm. Ball milling under the above parameters not only forms the Al-coated TiC core-shell composite powder, but also ensures that the particle size of the Al-coated TiC core-shell composite powder is within the range of this invention, resulting in optimal dispersibility in the melt.

[0021] In a preferred embodiment, the pressing and molding method is hydraulic molding, with a pressure of 15-20 kN and a holding time of 10-20 s. In actual operation, a TYA-600 hydraulic testing machine is used for hydraulic molding.

[0022] In a preferred embodiment, the precast block is a cylinder or block with dimensions of 20-40 mm × 10-80 mm and a height-to-diameter ratio of 0.5-2.

[0023] In this invention, there are no strict restrictions on the shape of the preform. Simple cylindrical or square shapes are preferred. To facilitate the design of the die-casting mold and uniform stress distribution, there are no strict requirements on the size. However, the height-to-diameter ratio should be controlled between 0.5 and 2 to avoid uneven density during pressing due to excessive height. The preferred size is a height of 20-40 mm and a width, length, or diameter of 10-80 mm. If the size is too small, it may increase the edge effect and affect the sintering consistency. If it is too large, it may cause uneven pressure distribution during pressing, requiring layered pressing or isostatic pressing assistance.

[0024] The addition of preforms can avoid segregation caused by density differences; it isolates the direct reaction between TiC and the melt, decomposing the strong exothermic reaction into a multi-step mild reaction; the aluminum layer isolation reduces the contact probability between TiC and Ce, reduces the Ce burn-off rate, and controls the reaction path to suppress Al4C3.

[0025] The preferred method is to add the preformed blocks to the molten aluminum in two batches. By adding them to the molten aluminum in two batches, the bottom TiC can be prevented from sintering into blocks. Secondly, since the reaction between TiC and Al is an exothermic reaction, adding them in two batches can prevent the temperature from becoming too high, which would cause the coating layer of the preformed blocks to melt and fail prematurely due to high temperature.

[0026] In a preferred embodiment, during the first heat treatment, the temperature is first maintained for 20-30 minutes, and then maintained for 2-5 minutes with stirring at a rate of 2000-3000 r / min, preferably 2000-2500 r / min. This operation eliminates any potential second-phase segregation in the refining agent and promotes a uniform distribution of chemical components in the melt.

[0027] During the first heat preservation process, the preform is held at a constant temperature for 20-30 minutes. During this process, an interfacial reaction occurs between the surface of the preform and the molten aluminum. The generated TiAl3 gradually diffuses into the molten aluminum. By stirring, TiAl3 and TiC are fully dispersed into the melt. If the heat preservation is not performed first and stirring is performed directly, the reaction on the surface of the preform will not be fully carried out, and undissolved TiC particles will easily form, leading to component segregation. If the stirring time is too long, TiAl3 and TiC particles will be mechanically broken into nanoscale particles, thus losing their nucleation ability. If the stirring time is too short, TiAl3 and TiC cannot be fully dispersed. If the stirring speed is too slow, TiAl3 and TiC will also be not fully dispersed. If the stirring speed is too fast, the fine phase may be destroyed.

[0028] In a preferred embodiment, during the second heat preservation process, the temperature is first maintained for 20-30 minutes, and then maintained for 2-5 minutes with stirring at a rate of 2000-3000 r / min, preferably 2000-2500 r / min. During the second heat preservation process, the temperature is first maintained and allowed to stand to allow Ce and AlTi3 to react fully, and then high-speed stirring is used to refine and fully disperse the resulting phase.

[0029] In the preferred embodiment, the slag removal and refining process involves first skimming the slag off the melt, and then adding carbon hexachloride for slag removal and refining. Adding C2Cl6 to the aluminum melt for degassing and refining allows C2Cl6 to decompose and generate gas, and the small amounts of Cl2 and C2Cl6 gas produced are immiscible with the aluminum melt.

[0030] In a preferred embodiment, the mold is a graphite mold; the mold is preheated to 100-200℃ before casting, and then water-cooled after casting. Water cooling can suppress Ce segregation and prevent the growth of Al-Ce and Al3Ti phases.

[0031] In a preferred embodiment, the mass fraction of Ce in the Al-Ti-C-Ce master alloy is 0.25-1%, preferably 0.25-0.5%. Experiments have shown that the mass fraction of Ce has a significant impact on the final refining effect, and the refining effect is optimal within this range.

[0032] In a preferred embodiment, the Al-Ti-C-Ce master alloy has the following composition by mass percentage: Ti: 5%, C: 1.2%, Ce: 0.25-0.5%, with the balance being Al.

[0033] In a further preferred embodiment, the Al-Ti-C-Ce master alloy has the following composition by mass percentage: Ti: 5%, C: 1.2%, Ce: 0.5%, with the balance being Al.

[0034] In the preferred embodiment, the unavoidable impurity content in the Al-Ti-C-Ce master alloy is ≤0.15%.

[0035] The present invention also provides an Al-Ti-C-Ce master alloy prepared by the above preparation method.

[0036] In a preferred embodiment, the Al-Ti-C-Ce master alloy contains a refined nucleation phase, which includes TiC, Al3Ti, and Al 20 Ti2Ce.

[0037] The present invention also provides the application of the Al-Ti-C-Ce master alloy prepared by the above preparation method, using the Al-Ti-C-Ce master alloy as a refining agent for aluminum-silicon alloys.

[0038] Furthermore, the amount of Al-Ti-C-Ce master alloy used is 0.5-1 wt. of that of aluminum-silicon alloy.

[0039] Furthermore, the aluminum-silicon alloy is an A356 alloy.

[0040] The present invention has the following beneficial effects:

[0041] 1. The preparation method of this invention rationally controls the amount of titanium, carbon, and cerium added, and replaces the Ti source and C source with TiC. It eliminates the need for a strong exothermic reaction to synthesize TiC on-site, avoiding the violent exothermic reaction of titanium powder + graphite. The traditional process suffers from local overheating of 1500℃, which leads to crucible erosion and component segregation. The 740℃ temperature field of the TiC process is much more stable. Furthermore, the direct addition of TiC reduces the amount of Al4C3 generated. In the traditional process, titanium powder is flammable and explosive (ignition energy <10mJ), while TiC is much safer. The TiC solution avoids graphite dust (inhalable particulate matter) and CO generation (greenhouse gas), which is in line with the trend of green manufacturing.

[0042] 2. The preparation method of the present invention does not require complex equipment or high temperature and high pressure conditions. It is simple, low in cost, has a significant refining effect, and is environmentally friendly.

[0043] 3. Compared with traditional fluoride salt reactions, the preparation method of this invention does not emit harmful gases such as HF and Cl2, and uses an aluminum-cerium master alloy to avoid the introduction of other impurities.

[0044] 4. The grain refiner of this invention can significantly improve the grain structure of aluminum-silicon alloys and has excellent anti-poisoning and anti-fading properties, thus playing an effective refining role in the refining of aluminum-silicon alloys. Attached Figure Description

[0045] Figure 1 The XRD patterns are of the intermediate alloys prepared in Example 1 and Comparative Example 1, wherein... Figure 1 (a) is the XRD pattern of the Al-Ti-C-Ce master alloy prepared in Example 1. Figure 1 (b) is the XRD pattern of the Al-Ti-C master alloy prepared in Comparative Example 1.

[0046] Figure 2 The microstructure diagrams are of the intermediate alloys of Example 1 and Comparative Example 1, wherein... Figure 2 (a) is a microstructure diagram of the Al-Ti-C-Ce master alloy prepared in Example 1. Figure 2 (b) is a microstructure diagram of the Al-Ti-C master alloy prepared in Comparative Example 1.

[0047] Figure 3 Macroscopic grain diagram of A356 alloy without added grain refiner.

[0048] Figure 4 This is a macroscopic view of the grain size of the A356 alloy after being refined by the refining agent in Example 1.

[0049] Figure 5 Macroscopic image of the grains of A356 alloy after refinement by the refiner in Comparative Example 1.

[0050] Figure 6 Macroscopic image of the grains of A356 alloy after refinement by the refiner in Comparative Example 2.

[0051] Figure 7 This is a process flow diagram of the present invention. Detailed Implementation

[0052] The principles and features of this invention are described below. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0053] Example 1

[0054] An Al-Ti-C-Ce master alloy comprises, by mass percentage: 5% titanium, 1.2% carbon, 0.5% cerium, ≤0.1% impurities, and the balance being aluminum.

[0055] Its preparation method includes the following steps:

[0056] Step 1: Dry titanium carbide powder with a particle size of 1.0-2.0 μm in a vacuum oven at 200℃ for 2 hours. Mix it with aluminum powder with a particle size of 45-75 μm at a ratio of TiC:Al=1:3, and ball mill the powder at 200 r / min for 60 min, controlling the ball-to-powder ratio at 12:1. The grinding ball material is WC-Co. After ball milling, a core-shell structured composite powder of Al-coated TiC with a particle size of 0.8-1 μm is obtained. Then, it is hydraulically molded to obtain a cylindrical preform with a size of 20×15 mm.

[0057] Step 2: Place the pure aluminum ingot into a graphite crucible and heat it to 850℃ until completely melted. Then, press the preform obtained in Step 1 into the bottom of the melt in two batches through a graphite bell jar to prevent it from floating. Hold the mixture at this temperature for 25 minutes under an argon-protected atmosphere, and then hold it at this temperature for 3 minutes with stirring at a rate of 2500 r / min.

[0058] Step 3: Cool down to 750℃ and add the Al-30Ce alloy block directly. Hold for 25 minutes, then hold for 4 minutes with stirring at 2500r / min.

[0059] Step 4: After skimming the slag off the melt, add carbon hexachloride for slag removal and refining, then quickly pour it into a mold to cool, and obtain the Al-Ti-C-Ce master alloy.

[0060] Example 2

[0061] An Al-Ti-C-Ce master alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, 0.25% cerium, ≤0.15% impurities, and the balance being aluminum.

[0062] Its preparation method includes the following steps:

[0063] Step 1: Dry titanium carbide powder with a particle size of 1.0-2.0 μm in a vacuum oven at 200℃ for 2 hours. Mix it with aluminum powder with a particle size of 45-75 μm at a ratio of TiC:Al=1:3, and ball mill the powder at 150 r / min for 60 min, controlling the ball-to-powder ratio at 10:1. The grinding ball material is WC-Co. After ball milling, a core-shell structured composite powder of Al-coated TiC with a particle size of 0.8-1 μm is obtained. Then, it is hydraulically molded to obtain a cylindrical preform with a size of 20×30 mm.

[0064] Step 2: Place the pure aluminum ingot into a graphite crucible and heat it to 850℃ until completely melted. Then, press the preform obtained in Step 1 into the bottom of the melt in two batches through a graphite bell jar to prevent it from floating. Hold the mixture at this temperature for 20 minutes under an argon-protected atmosphere, and then hold it at this temperature for 2 minutes with stirring at a rate of 2000 r / min.

[0065] Step 3: Cool down to 750℃ and add the Al-30Ce alloy block directly. Hold for 20 min, then hold for 2 min with stirring at 2000 r / min.

[0066] Step 4: After skimming the slag off the melt, add carbon hexachloride for slag removal and refining, then quickly pour it into a mold to cool, and obtain the Al-Ti-C-Ce master alloy refiner.

[0067] Example 3

[0068] An Al-Ti-C-Ce master alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, 1.0% cerium, ≤0.15% impurities, and the balance being aluminum.

[0069] Its preparation method includes the following steps:

[0070] Step 1: Dry titanium carbide powder with a particle size of 1.0-2.0 μm in a vacuum oven at 200℃ for 2 hours. Mix it with aluminum powder with a particle size of 45-75 μm at a ratio of TiC:Al=1:3, and ball mill the powder at 250 r / min for 60 min, controlling the ball-to-powder ratio at 15:1. The grinding ball material is WC-Co. After ball milling, a core-shell structured composite powder of Al-coated TiC with a particle size of 0.8-1 μm is obtained. Then, it is hydraulically molded to obtain a cylindrical preform with a size of 25×40 mm.

[0071] Step 2: Place the pure aluminum ingot into a graphite crucible and heat it to 850℃ until completely melted. Then, press the preform obtained in Step 1 into the bottom of the melt in two batches through a graphite bell jar to prevent it from floating. Hold the mixture at this temperature for 30 minutes under an argon-protected atmosphere, and then hold it at this temperature for 5 minutes with stirring at a rate of 3000 r / min.

[0072] Step 3: Cool down to 750℃ and add the Al-30Ce alloy block directly. Hold for 30 min, then hold for 5 min with stirring at 3000 r / min.

[0073] Step 4: After skimming the slag off the melt, add carbon hexachloride for slag removal and refining, then quickly pour it into a mold to cool, and obtain the Al-Ti-C-Ce master alloy refiner.

[0074] Comparative Example 1

[0075] An Al-Ti-C intermediate alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, ≤0.1% impurities, and the balance being aluminum; its preparation method differs from that of Example 1 in that aluminum-cerium alloy is not added in step 3.

[0076] Comparative Example 2

[0077] An Al-Ti-C-Ce intermediate alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, 0.5% cerium, ≤0.1% impurities, and the balance being aluminum. Its preparation method differs from that of Example 1 in that titanium powder and graphite are used instead of titanium carbide as the titanium source and carbon source in step 1.

[0078] Comparative Example 3

[0079] An Al-Ti-C-Ce intermediate alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, 0.5% cerium, ≤0.1% impurities, and the balance being aluminum. Its preparation method differs from that of Example 1 in that, instead of ball milling, step 1 involves simple mixing and pressing into preforms.

[0080] Comparative Example 4

[0081] An Al-Ti-C-Ce intermediate alloy refiner comprises the following components by mass percentage: 5% titanium, 1.2% carbon, 0.5% cerium, ≤0.1% impurities, and the balance being aluminum; its preparation method differs from that of Example 1 in that Al:TiC = 1:1 is ball-milled in step 1.

[0082] Performance Analysis 1

[0083] (1) To characterize the composition of the refining agent, X-ray diffraction analysis was performed on the refining agents of Example 1 and Comparative Example 1, respectively. The results are as follows: Figure 1 As shown, the phase composition of the refining agent in Example 1 is α-Al, TiC, Al3Ti, Al 20 Ti2Ce phase.

[0084] (2) In order to observe the microstructure of the refining agent, the refining agents of Example 1 and Comparative Example 1 were characterized by scanning electron microscopy, and the results are as follows: Figure 2 As shown, where, Figure 2 Figure (a) is a microstructure of the Al-Ti-C-Ce master alloy prepared in Example 1, and Figure (b) is a microstructure of the Al-Ti-C master alloy in Comparative Example 1.

[0085] Depend on Figure 2 It can be seen that the finer particles in Example 1 and Comparative Example 1 have uniform structures, and the particle sizes of the refined nucleation particles Al3Ti are 8-10 μm and 20-30 μm, respectively, while the particle size of TiC is less than 2-3 μm.

[0086] Performance Analysis 2

[0087] (1) The Al-Ti-C-Ce and Al-Ti-C intermediate alloy ingots of Examples 1-3 and Comparative Examples 1-4 were crushed and then ball-milled. The ball-to-material ratio was 10:1, the rotation speed was 300 rpm, and the time was 10 hours. At the same time, 0.5% ethanol was added to prevent cold welding.

[0088] (2) Weigh the aluminum-silicon A356 alloy into a clay crucible and place it in a crucible resistance furnace at a temperature of 750℃ to make it molten; then weigh the finer agent after ball milling in (1) at 0.2% of the mass of the molten aluminum-silicon alloy, add the finer agent to the molten aluminum-silicon alloy and keep it at a temperature of 15-300 min; then take the crucible out of the furnace, stir the melt thoroughly, pour it into the cast iron mold, cool and demold to obtain the fined A356 alloy ingot.

[0089] Macroscopic grain diagrams of the original A356 alloy and the refined A356 alloy ingot are shown below. Figures 3-5 As shown, where, Figure 3 It is an aluminum-silicon alloy without added refining agents. Figure 4To add macroscopic grain diagrams of aluminum-silicon alloys obtained from the Al-Ti-C-Ce master alloy in Example 1 at different holding times, Figure 5 Macroscopic grain diagrams of aluminum-silicon alloys obtained by adding the Al-Ti-C master alloy from Comparative Example 1 at different holding times. Figure 6 Macroscopic grain structures of aluminum-silicon alloys obtained by adding the Al-Ti-C-Ce master alloy from Comparative Example 2 at different holding times. Figure 3 It can be seen that the average grain size of the original A356 alloy is over 1200 μm, such as Figure 4 It can be seen that the Al-Ti-C-Ce master alloy in Example 1, after being held at a temperature for 15 minutes, resulted in grain refinement to 95 μm; respectively by Figure 4 , Figure 5 , Figure 6 It can be seen that after holding for 300 min, the average grain size of the A356 alloy ingots refined by the refining agents of Example 1, Comparative Example 1, and Comparative Example 2 decreased to below 106 μm, 278 μm, and 141 μm, respectively, which are 8.83%, 23.17%, and 11.75% of the original A356 alloy. This indicates that compared with the refining agents without rare earth cerium and those with titanium and cerium sources respectively, the Al-Ti-C-Ce refining agent prepared by Example 1 using TiC as raw material can more effectively improve the grain structure of aluminum-silicon alloys. In addition, the Al-Ti-C-Ce refining agent obtained in Example 2 reduced the grain size of A356 alloy to below 118 micrometers after holding for 300 min, which is a significant improvement for A356 aluminum-silicon alloys. The original grain size was 9.83%; in Example 3, the Al-Ti-C-Ce refining agent reduced the grain size of A356 alloy to below 128 micrometers after holding at a temperature for 300 min, which is 10.67% of the original grain size of A356 aluminum-silicon alloy; the Al-Ti-C-Ce refining agent prepared by adding Comparative Example 3 reduced the grain size of A356 alloy to below 227 micrometers after holding at a temperature for 300 min, which is 18.92% of the original grain size of A356 aluminum-silicon alloy; the Al-Ti-C-Ce refining agent prepared by adding Comparative Example 4 reduced the grain size of A356 alloy to below 171 micrometers after holding at a temperature for 300 min, which is 14.25% of the original grain size of A356 aluminum-silicon alloy.

[0090] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source, characterized in that: Titanium carbide powder and aluminum powder are mixed and ball-milled to obtain Al-coated TiC core-shell structured composite powder. The Al-coated TiC core-shell structured composite powder is pressed into preforms. The preforms are pressed into the bottom of the aluminum melt in batches through a graphite bell jar. The temperature is first held at 760-850℃, then cooled to 700-750℃. Al-30Ce master alloy is then added, and the temperature is held a second time. The mixture is then slag removed and refined, and finally poured into a mold to obtain the Al-Ti-C-Ce master alloy. In the Al-coated TiC core-shell composite powder, the mass ratio of TiC:Al is 1:2-4. The Al-Ti-C-Ce master alloy has the following composition by mass percentage: Ti: 0.5-7%, C: 0.5-2%, Ce: 0.05-1%, with the balance being Al.

2. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The titanium carbide powder has a particle size of 1.0-2.0 μm, and the aluminum powder has a particle size of 45-75 μm. The titanium carbide powder is first dried in a vacuum environment at 100-200℃ for 2-4 hours, with a vacuum degree ≤10. -2 Pa.

3. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The ball mill rotates at a speed of 150-250 r / min, the milling time is 30-60 min, the ball-to-material ratio is 10-15:1, and the grinding balls are made of WC-Co. The particle size of the Al-coated TiC core-shell composite powder is 0.8-1 μm.

4. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The pressing and molding method is hydraulic molding, with a pressure of 15-20 kN and a holding time of 10-20 s; The precast block is a cylinder or block with dimensions of 20-40 mm × 10-80 mm and a height-to-diameter ratio of 0.5-2.

5. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The precast blocks were added to the molten aluminum in two batches. During the first heat preservation process, the heat preservation is first carried out for 20-30 minutes, and then the heat preservation is carried out for 2-5 minutes under stirring at a rate of 2000-3000 r / min. During the second heat preservation process, the temperature is first maintained for 20-30 minutes, and then maintained for 2-5 minutes with stirring at a rate of 2000-3000 r / min.

6. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The slag removal and refining process involves first skimming the slag off the melt, and then adding carbon hexachloride for slag removal and refining.

7. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: The mold is a graphite mold; the mold is preheated to 100-200℃ before pouring, and the mold is water-cooled after pouring.

8. The method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to claim 1, characterized in that: In the Al-Ti-C-Ce master alloy, the mass fraction of Ce is 0.25-1%.

9. The Al-Ti-C-Ce master alloy prepared by the method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both a Ti and C source according to any one of claims 1-8, characterized in that: The Al-Ti-C-Ce master alloy contains refined nucleation phases, which include TiC, Al3Ti, and Al. 20 Ti2Ce.

10. The application of the Al-Ti-C-Ce master alloy prepared by the method for preparing an Al-Ti-C-Ce master alloy using titanium carbide as both Ti and C sources according to any one of claims 1-8, characterized in that: Al-Ti-C-Ce master alloy was used as a refining agent for aluminum-silicon alloys.

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