A rare earth doped aluminum alloy that can be compression cast and a method of making the same

Abstract

The present application relates to a kind of rare earth doped aluminum alloy and its preparation method, belong to aluminum alloy technical field, by matching the matching range of multiple alloy elements, alloy melt has good fluidity and filling capacity, can be adapted to high pressure die casting near net shape forming process, realize the efficient scale preparation of complex structure parts;At the same time, by introducing high melting point Ti2AlC-TiB2 complex ceramic phase and rare earth intermetallic compound, significantly improve the high temperature softening resistance of alloy, solve the industry pain point that traditional die casting aluminum alloy temperature resistance is insufficient, deformation aluminum alloy die casting formability is poor, under the premise of guaranteeing die casting filling capacity, significantly improve the high temperature softening resistance of alloy, give consideration to scale die casting production efficiency and service demand.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy technology, and relates to a die-castable rare earth-doped aluminum alloy and its preparation method. Background Technology

[0002] With the continuous increase in the integration of high-power electronic devices, thermal management substrates such as liquid-cooled flow channels have placed higher demands on heat dissipation efficiency, structural strength, and manufacturing costs. Their fabrication must simultaneously meet the requirements of high thermal conductivity, resistance to brazing temperatures above 600°C, and large-scale, efficient production. Traditional thermal management substrates are mostly made from 6-series aluminum profiles through CNC machining. Although they have high solidus temperatures and are compatible with hard brazing processes, their material utilization rate is low, resulting in high production costs. Die-cast aluminum alloys can significantly reduce costs and increase efficiency due to their near-net-shape advantages. However, the solidus temperatures of mainstream Al-Si and Al-Mg series casting alloys are generally below 590°C, making them prone to softening and deformation during brazing, which cannot meet the requirements of high-temperature brazing. On the other hand, 6-series wrought aluminum alloys have a high tendency for hot cracking and poor filling performance, making them difficult to adapt to die-casting processes. Rare earth elements, due to their unique electronic structure and strong interfacial activity, are known as "industrial vitamins" and have significant value in the field of microalloying modification of aluminum alloys. Their modification mechanism is mainly reflected in three aspects: First, melt purification, which can generate high-melting-point compounds with impurities such as hydrogen, oxygen, and sulfur and float to form slag, reducing the gas content and inclusion content of the melt, and reducing porosity and slag inclusion defects in castings; Second, modification and refinement, which agglomerates at the solid-liquid interface front, inhibiting the preferential growth of grains and eutectic phases, promoting the transformation of coarse dendrites into fine equiaxed grains, and transforming acicular eutectic silicon into granular or fibrous forms, thereby improving the plasticity and toughness of the alloy; Third, microstructure regulation, which forms multi-metallic compounds with Fe, Si, etc., improving the morphology and distribution of harmful iron-rich phases, reducing their cutting effect on the matrix, and some rare earth elements can also form dispersed second phases, exerting grain boundary strengthening and dispersion strengthening effects.

[0003] Chinese invention patent application CN118910473A discloses a high-strength rare-earth-doped aluminum alloy and its preparation method, comprising alloy materials and rare-earth materials. The alloy materials include the following raw materials: magnesium, silicon, lithium, zirconium, copper, and titanium. The rare-earth materials include the following raw materials: cerium, lanthanum, neodymium, and scandium, with the balance being aluminum and unavoidable impurities. Based on the aluminum alloy material, rare-earth elements cerium, lanthanum, neodymium, and scandium are doped to obtain a high-strength rare-earth-doped aluminum alloy. The performance of the aluminum alloy is improved by utilizing rare-earth elements. At the same time, the strength and hardness of the aluminum alloy matrix material are improved by adding copper, magnesium, and lithium elements. Furthermore, the performance of the aluminum alloy matrix material is improved by adding silicon and titanium elements, thereby comprehensively improving the strength of the rare-earth-doped aluminum alloy.

[0004] The aluminum alloy in the above technical solution contains lithium. Lithium evaporates and burns rapidly in aluminum melt above 700°C, and it readily undergoes violent oxidation reactions with oxygen and water vapor in the environment, resulting in low lithium yield and large fluctuations. Conventional pre-furnace composition control is difficult to achieve precise control of its content, which easily leads to poor compositional consistency between batches of die castings. At the same time, lithium significantly increases the hydrogen solubility of aluminum melt, and the lithium hydride products generated by its reaction with trace amounts of water vapor in the melt further increase the gas content of the melt. The high-speed filling and rapid solidification process characteristics of die casting prevent the gas from floating out in time, easily forming diffuse pinholes and porosity defects inside the casting. Summary of the Invention

[0005] The purpose of this invention is to provide a die-castable rare earth-doped aluminum alloy and its preparation method. By strengthening with rare earth-modified Ti2AlC-TiB2 and controlling the microstructure through stepwise melting, the invention achieves a balance between high-pressure die-casting formability, high-temperature resistance, and good strength and toughness.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a die-castable rare-earth-doped aluminum alloy, the composition of which, by mass percentage, is as follows:

[0008] RE: 0.8-1%, Mn: 0.4-0.8%, Cr: 0.02-0.18%, Mg: 0.1-0.3%, Fe: 0.8-1.4%, Zr: 0.1-0.3%, Gd: 0.1-0.3%, Si: 0.08-0.28%, ceramic phase rare earth modified composite powder: 5-8%, balance is Al and unavoidable impurities.

[0009] Furthermore, the RE is composed of lanthanum and cerium in a mass ratio of 1:1.

[0010] This invention also provides a method for preparing a die-castable rare-earth-doped aluminum alloy, comprising the following steps:

[0011] Step 1: Wet ball milling of titanium powder, aluminum powder, boron carbide powder and anhydrous ethanol, drying and sieving to obtain mixed powder; hot pressing sintering of the mixed powder under argon protection, followed by crushing, sieving and drying to obtain Ti2AlC-TiB2 powder; mixing and grinding of lanthanum salt, cerium salt, citric acid and Ti2AlC-TiB2 powder, drying and calcining under argon protection to obtain rare earth modified composite powder.

[0012] Step 2: Melt and adjust the composition of pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy in stages. After powder spraying and refining, add rare earth modified composite powder accounting for 5-8% of the total mass of the melt and stir for 10 minutes to obtain a clean aluminum alloy melt.

[0013] Step 3: Transfer the molten aluminum alloy into a die-casting machine for die casting to obtain a die-castable rare earth-doped aluminum alloy.

[0014] Furthermore, the specific preparation process of the mixed powder is as follows:

[0015] Titanium powder, aluminum powder, and boron carbide powder were loaded into an agate ball mill jar in a mass ratio of 4:1.2:1. Anhydrous ethanol was added, with a mass ratio of anhydrous ethanol to raw material powder of 3:10. The grinding balls were made of agate with a diameter of 3-12 mm, and the mass ratio of grinding balls to the material to be ground was 3:1. The mixture was wet-milled using a planetary ball mill for 12-14 hours, dried, cooled to room temperature, and sieved to obtain a mixed powder.

[0016] Furthermore, the specific preparation process of Ti2AlC-TiB2 powder is as follows:

[0017] BN powder is uniformly coated on the inner wall of a graphite hot pressing mold as a release agent. The mixed powder is then filled into the mold and sent into a hot pressing furnace as a whole. Under argon protection, the temperature is raised to 1350-1400℃ at a heating rate of 10℃ / min and held at 30-40MPa axial pressure for 1-2 hours. The furnace is then cooled to room temperature to obtain Ti2AlC-TiB2 sintered blocks. These blocks are then crushed into micron-sized powders by a jaw crusher and planetary ball mill, sieved, and dried to obtain Ti2AlC-TiB2 powder.

[0018] Furthermore, the specific preparation process of the rare earth modified composite powder is as follows:

[0019] Lanthanum salt, cerium salt, and Ti2AlC-TiB2 powder were added to a reaction vessel, citric acid monohydrate was added, and the mixture was transferred to an agate mortar and ground for 20-30 minutes. The mixture was then placed in a muffle furnace and heated to 800-820℃ under argon protection and calcined for 3-4 hours. The mixture was then allowed to cool naturally to room temperature. After grinding and sieving, rare earth modified composite powder was obtained.

[0020] Furthermore, the mass ratio of lanthanum salt, cerium salt, Ti2AlC-TiB2 powder and citric acid monohydrate is 4.3-6.5:4.3-7.1:100-150:4.2-6.4.

[0021] Furthermore, the lanthanum salt is any one of lanthanum nitrate hexahydrate, anhydrous lanthanum nitrate, and lanthanum acetate hydrate.

[0022] Furthermore, the cerium salt is either cerium nitrate hexahydrate or cerium acetate trihydrate.

[0023] Furthermore, the specific preparation process of the aluminum alloy melt is as follows:

[0024] Pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy are dried at 190-210℃ to remove moisture. The pure aluminum ingots are placed in a melting crucible and heated until completely melted. The melt temperature is raised to 750-800℃, and aluminum-zirconium alloy, aluminum-lanthanum alloy, and aluminum-chromium alloy are added sequentially, stirring until completely melted. The melt temperature is lowered to 720-750℃, and aluminum-silicon alloy, aluminum-manganese alloy, and aluminum-iron alloy are added, stirring until completely melted. The temperature is lowered to 700-720℃, and pure magnesium ingots and aluminum-gadolinium alloy are added. After all materials have melted and been thoroughly stirred, adjust the composition and raise the temperature to a refining temperature of 720-730℃. Use a rotary jetting device to introduce argon gas carrying refining agent powder into the melt for powder spraying refining, degassing, and slag removal treatment. The refining agent is a salt flux that can adsorb impurities in the melt, and the amount added is 0.3%-2.0% of the total weight of the melt. After refining, let the melt stand for 10-15 minutes, perform surface slag removal treatment, add 5-8% of rare earth modified composite powder according to the total mass of the melt, stir for 10 minutes, and obtain a clean aluminum alloy melt.

[0025] Furthermore, the process parameters for rotary jet blowing are: rotor speed of 450-550 r / min, degassing time of 5-10 min, gas source pressure of 0.30-0.40 MPa, and gas flow rate of 10-20 L / min.

[0026] Furthermore, the process parameters for die casting are an injection speed of 1.5-3 m / s and a casting pressure of 80-120 MPa.

[0027] The beneficial effects of this invention are:

[0028] 1. This invention, by matching the proportions of multiple alloying elements, enables the alloy melt to possess excellent fluidity and filling ability, making it suitable for near-net-shape forming processes in high-pressure die casting and achieving efficient large-scale preparation of complex structural parts. At the same time, by introducing high-melting-point Ti2AlC-TiB2 multiphase ceramic phase and rare earth intermetallic compounds, the high-temperature softening resistance of the alloy is significantly improved, solving the industry pain points of insufficient temperature resistance of traditional die-cast aluminum alloys and poor die-casting formability of wrought aluminum alloys. While ensuring die-casting filling ability, the high-temperature softening resistance of the alloy is significantly improved, taking into account both the efficiency of large-scale die-casting production and service requirements.

[0029] 2. On the one hand, this invention uses Ti2AlC-TiB2 multiphase ceramic particles as the reinforcing phase to improve the strength and modulus of the alloy matrix through fine grain strengthening and dispersion strengthening mechanisms. On the other hand, through the process of "rare earth salt-citric acid mixed grinding-argon protective calcination", a uniform lanthanum and cerium rare earth oxide modification layer is generated in situ on the surface of the ceramic particles, which effectively improves the interfacial wettability between the ceramic phase and the aluminum melt, reduces the interfacial energy, inhibits the agglomeration of ceramic particles, and promotes their uniform dispersion in the aluminum matrix. At the same time, the rare earth modification layer can strengthen the interfacial bonding strength between the ceramic phase and the aluminum matrix, ensuring that the applied load can be effectively transferred from the matrix to the ceramic reinforcing phase. This fully releases the reinforcing potential of the ceramic phase and avoids stress concentration and plastic deterioration caused by weak interfacial areas. Under the premise of ensuring the usable plasticity of the alloy, the reinforcing effect of the ceramic phase is fully released, achieving a good match between strength and plasticity.

[0030] 3. This invention optimizes the alloy microstructure from multiple dimensions through the synergistic effect of various rare earth elements such as lanthanum, cerium, and gadolinium with alloying elements such as Mn, Cr, Zr, and Fe. Rare earth elements can agglomerate at the solid-liquid interface front, inhibiting preferential grain growth and refining the grains of the as-cast matrix. They can also interact with iron elements to regulate the morphology and distribution of iron-rich phases, transforming acicular and flaky harmful phases into granular phases and reducing their cutting effect on the matrix. At the same time, rare earth elements have a melt purification effect, combining with hydrogen and oxide impurities in the melt to form high-melting-point compounds that float to the surface and are removed, reducing the risk of porosity and inclusion defects during the die-casting process. This simultaneously improves the strength and toughness matching of the alloy from the perspectives of microstructure homogenization and purity.

[0031] 4. This invention employs an argon-protected hot-pressing sintering and calcination process, which avoids oxidation and deterioration of the ceramic phase and rare earth components throughout the process, ensuring the structural integrity of the reinforcing phase and the purity of the modified layer. The step-by-step temperature-controlled melting and feeding process is adapted to the melting characteristics and burn-off patterns of different intermediate alloys, enabling precise control of the alloy composition. The ceramic powder addition process is placed after refining and slag removal, which not only ensures the purification effect of the melt but also avoids the loss of the ceramic reinforcing phase caused by the refining and slag-making process. The high-pressure die-casting process parameters are compatible with the characteristics of the alloy melt, ensuring complete mold filling while improving the density of the casting. The entire process is highly feasible and suitable for large-scale industrial production. Detailed Implementation

[0032] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0033] Example 1: This example provides a die-castable rare-earth-doped aluminum alloy, prepared through the following steps:

[0034] S1: Titanium powder, aluminum powder, and boron carbide powder are loaded into an agate ball mill jar at a mass ratio of 4:1.2:1. Anhydrous ethanol is added, with a mass ratio of anhydrous ethanol to raw material powder of 3:10. The grinding balls are made of agate and have a diameter of 3 mm. The mass ratio of grinding balls to the material to be ground is 3:1. The ball milling and mixing are carried out on a planetary ball mill and wet-milled for 12 hours. The mixed powder is then dried in an oven and cooled to room temperature. The raw material powder and agate balls are separated by sieving through a 100-mesh stainless steel sieve to obtain a mixed powder.

[0035] S2: BN powder is uniformly coated on the inner wall of the graphite hot pressing mold as a release agent. The mixed powder is filled into the mold and then sent into the hot pressing furnace as a whole. Under the protection of argon, the temperature is raised to 1350℃ at a heating rate of 10℃ / min and held at 30MPa axial pressure for 1h. The mixture is then cooled to room temperature with the furnace to obtain Ti2AlC-TiB2 sintered block. The sintered block is first crushed into micron-sized powder by jaw crusher and planetary ball mill. Large particles are removed by passing through a 200-mesh sieve and then dried at 200℃ for 2h to obtain Ti2AlC-TiB2 powder.

[0036] S3: Add 4.3g of lanthanum nitrate hexahydrate, 4.3g of cerium nitrate hexahydrate and 100g of Ti2AlC-TiB2 powder to a reaction vessel, add 4.2g of citric acid monohydrate, mix and then transfer to an agate mortar for grinding for 20min. Dry at 110℃ for 10h, place in a muffle furnace, heat to 800℃ under argon protection, calcine for 3h, and allow to cool naturally to room temperature. Grind and pass through a 500-mesh sieve to obtain rare earth modified composite powder.

[0037] S4: Place pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy into a preheating device for drying. The preheating temperature is controlled at 190℃ to remove moisture adsorbed on the surface of the raw materials and prevent hydrogen addition to the melt. Place the pure aluminum ingots in a melting crucible and heat until completely melted. Raise the melt temperature to 750℃, then add aluminum-zirconium alloy, aluminum-lanthanum alloy, and aluminum-chromium alloy in sequence, stirring until completely melted. Cool the melt to 720℃, then add aluminum-silicon alloy, aluminum-manganese alloy, and aluminum-iron alloy, stirring until completely melted. Cool to 700℃, then add pure magnesium ingots and aluminum-gadolinium alloy. After all materials have melted and been thoroughly stirred, allow to stand and take samples for pre-furnace composition analysis. Based on the test results, replenish or flush the melt. After adjusting the composition to ensure that the content of each element is within the designed range, the temperature is raised to a refining temperature of 720℃. Argon gas carrying refining agent powder is introduced into the melt using a rotary jetting device for powder spraying refining, degassing, and slag removal. The rotary jetting process parameters are: rotor speed 450 r / min, degassing time 5 min, gas source pressure 0.30 MPa, gas flow rate 10 L / min, and the refining agent is a salt flux that can adsorb impurities in the melt, with an addition amount of 0.3% of the total melt weight. After refining, the melt is allowed to stand for 10 min to allow inclusions to float to the surface. Then, surface slag removal is performed, and rare earth modified composite powder accounting for 5% of the total melt mass is added and stirred for 10 min to obtain a clean aluminum alloy melt.

[0038] S5: The clean aluminum alloy melt is adjusted to a casting temperature of 690℃ and transferred to a die casting machine for high-pressure die casting. The die casting process parameters are set as follows: injection speed is 1.5m / s, casting pressure is 80MPa. After the melt solidifies rapidly in the mold, the mold is opened and the casting is taken out to obtain a die-castable rare earth doped aluminum alloy.

[0039] The composition of this die-castable rare-earth-doped aluminum alloy, by mass percentage, is as follows:

[0040] RE (La: 0.4%, Ce: 0.4%), Mn: 0.4%, Cr: 0.02%, Mg: 0.1%, Fe: 0.8%, Zr: 0.1%, Gd: 0.1%, Si: 0.08%, ceramic phase rare earth modified composite powder: 5%, balance is Al and unavoidable impurities.

[0041] Example 2: This example provides a die-castable rare-earth-doped aluminum alloy, prepared through the following steps:

[0042] S1: Titanium powder, aluminum powder, and boron carbide powder are loaded into an agate ball mill jar at a mass ratio of 4:1.2:1. Anhydrous ethanol is added, with a mass ratio of anhydrous ethanol to raw material powder of 3:10. The grinding balls are made of agate and have a diameter of 7mm. The mass ratio of grinding balls to the material to be ground is 3:1. The ball milling and mixing are carried out on a planetary ball mill and wet-milled for 13 hours. The mixed powder is then dried in an oven and cooled to room temperature. The raw material powder and agate balls are separated by sieving through a 100-mesh stainless steel sieve to obtain a mixed powder.

[0043] S2: BN powder is uniformly coated on the inner wall of the graphite hot pressing mold as a release agent. The mixed powder is filled into the mold and then sent into the hot pressing furnace as a whole. Under argon protection, the temperature is raised to 1375℃ at a heating rate of 10℃ / min and held at 35MPa axial pressure for 1.5h. The mixture is then cooled to room temperature in the furnace to obtain Ti2AlC-TiB2 sintered block. The sintered block is first crushed into micron-sized powder by jaw crusher and planetary ball mill. Large particles are removed by passing through a 200-mesh sieve and then dried at 250℃ for 2.5h to obtain Ti2AlC-TiB2 powder.

[0044] S3: Add 5.4g of lanthanum nitrate hexahydrate, 5.7g of cerium nitrate hexahydrate and 125g of Ti2AlC-TiB2 powder to a reaction vessel, add 5.3g of citric acid monohydrate, mix and then transfer to an agate mortar for grinding for 25min. Dry at 115℃ for 11h, place in a muffle furnace, heat to 810℃ under argon protection, calcine for 3.5h, and allow to cool naturally to room temperature. Grind and pass through a 500-mesh sieve to obtain rare earth modified composite powder.

[0045] S4: Place pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy into a preheating device for drying. The preheating temperature is controlled at 200℃ to remove moisture adsorbed on the surface of the raw materials and prevent hydrogen addition to the melt. Place the pure aluminum ingots in a melting crucible and heat until completely melted. Raise the melt temperature to 775℃, then add aluminum-zirconium alloy, aluminum-lanthanum alloy, and aluminum-chromium alloy in sequence, stirring until completely melted. Cool the melt to 735℃, then add aluminum-silicon alloy, aluminum-manganese alloy, and aluminum-iron alloy, stirring until completely melted. Cool to 710℃, then add pure magnesium ingots and aluminum-gadolinium alloy. After all materials have melted and been thoroughly stirred, allow to stand and take samples for pre-furnace composition analysis. Based on the test results, replenish or dilute the melt. The mixture is prepared so that the content of each element is within the designed composition range. Then, the temperature is raised to a refining temperature of 725℃. Argon gas carrying refining agent powder is introduced into the melt using a rotary jetting device for powder spraying refining, degassing, and slag removal. The process parameters for rotary jetting are: rotor speed of 500 r / min, degassing time of 7 min, gas source pressure of 0.35 MPa, gas flow rate of 15 L / min, and the refining agent is a salt flux that can adsorb impurities in the melt, with an addition amount of 1.15% of the total weight of the melt. After refining, the melt is allowed to stand for 12 min to allow the inclusions to float to the surface. Then, surface slag removal is performed, and rare earth modified composite powder accounting for 6.5% of the total mass of the melt is added and stirred for 10 min to obtain a clean aluminum alloy melt.

[0046] S5: The clean aluminum alloy melt is adjusted to a casting temperature of 720℃ and transferred to a die casting machine for high-pressure die casting. The die casting process parameters are set as follows: injection speed of 2.25m / s and casting pressure of 100MPa. After the melt solidifies rapidly in the mold, the mold is opened and the casting is removed to obtain a die-castable rare earth doped aluminum alloy.

[0047] The composition of this die-castable rare-earth-doped aluminum alloy, by mass percentage, is as follows:

[0048] RE (La: 0.45%, Ce: 0.45%), Mn: 0.6%, Cr: 0.10%, Mg: 0.2%, Fe: 1.1%, Zr: 0.2%, Gd: 0.2%, Si: 0.18%, ceramic phase rare earth modified composite powder: 6.5%, balance being Al and unavoidable impurities.

[0049] Example 3: This example provides a die-castable rare-earth-doped aluminum alloy, prepared through the following steps:

[0050] S1: Titanium powder, aluminum powder, and boron carbide powder are loaded into an agate ball mill jar at a mass ratio of 4:1.2:1. Anhydrous ethanol is added, with a mass ratio of anhydrous ethanol to raw material powder of 3:10. The grinding balls are made of agate and have a diameter of 12mm. The mass ratio of grinding balls to the material to be ground is 3:1. The ball milling and mixing are carried out on a planetary ball mill and wet-milled for 14 hours. The mixed powder is then dried in an oven and cooled to room temperature. The raw material powder and agate balls are separated by sieving through a 100-mesh stainless steel sieve to obtain a mixed powder.

[0051] S2: BN powder is uniformly coated on the inner wall of the graphite hot pressing mold as a release agent. The mixed powder is filled into the mold and then sent into the hot pressing furnace as a whole. Under the protection of argon, the temperature is raised to 1400℃ at a heating rate of 10℃ / min and held at 40MPa axial pressure for 2h. The furnace is then cooled to room temperature to obtain Ti2AlC-TiB2 sintered block. The sintered block is first crushed into micron-sized powder by jaw crusher and planetary ball mill. Large particles are removed by passing through a 200-mesh sieve and then dried at 300℃ for 3h to obtain Ti2AlC-TiB2 powder.

[0052] S3: Add 6.5g of lanthanum nitrate hexahydrate, 7.1g of cerium nitrate hexahydrate and 150g of Ti2AlC-TiB2 powder to a reaction vessel, add 6.4g of citric acid monohydrate, mix and then transfer to an agate mortar for grinding for 30min. Dry at 120℃ for 12h, place in a muffle furnace, heat to 820℃ under argon protection, calcine for 4h, and allow to cool naturally to room temperature with the furnace. After grinding, pass through a 500-mesh sieve to obtain rare earth modified composite powder.

[0053] S4: Place pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy into a preheating device for drying. The preheating temperature is controlled at 210℃ to remove moisture adsorbed on the surface of the raw materials and prevent hydrogen enrichment in the melt. Place the pure aluminum ingots in a melting crucible and heat until completely melted. Raise the melt temperature to 800℃, then add aluminum-zirconium alloy, aluminum-lanthanum alloy, and aluminum-chromium alloy in sequence, stirring until completely melted. Cool the melt to 750℃, then add aluminum-silicon alloy, aluminum-manganese alloy, and aluminum-iron alloy, stirring until completely melted. Cool to 720℃, then add pure magnesium ingots and aluminum-gadolinium alloy. After all materials have melted and been thoroughly stirred, allow to stand and take samples for pre-furnace composition analysis. Based on the test results, replenish or dilute the melt. Adjustments were made to ensure that the content of each element met the designed composition range. The temperature was then raised to a refining temperature of 730℃. Argon gas carrying refining agent powder was introduced into the melt using a rotary jetting device for powder spraying refining, degassing, and slag removal. The rotary jetting process parameters were: rotor speed 550 r / min, degassing time 10 min, gas source pressure 0.40 MPa, gas flow rate 20 L / min, and the refining agent was a salt flux that could adsorb impurities in the melt, with an addition amount of 2.0% of the total melt weight. After refining, the melt was allowed to stand for 15 min to allow inclusions to float to the surface. Then, surface slag removal was performed, and rare earth modified composite powder accounting for 8% of the total melt mass was added and stirred for 10 min to obtain a clean aluminum alloy melt.

[0054] S5: Adjust the clean aluminum alloy melt to a casting temperature of 750℃, transfer it to a die casting machine for high-pressure die casting. The die casting process parameters are set as follows: injection speed of 3m / s, casting pressure of 120MPa. After the melt solidifies rapidly in the mold, the mold is opened and the casting is removed to obtain a die-castable rare earth doped aluminum alloy.

[0055] The composition of this die-castable rare-earth-doped aluminum alloy, by mass percentage, is as follows:

[0056] RE (La: 0.5%, Ce: 0.5%), Mn: 0.8%, Cr: 0.18%, Mg: 0.3%, Fe: 1.4%, Zr: 0.3%, Gd: 0.3%, Si: 0.28%, ceramic phase rare earth modified composite powder: 8%, balance is Al and unavoidable impurities.

[0057] Example 4: This example provides a die-castable rare earth-doped aluminum alloy. The difference from Example 1 is that anhydrous lanthanum nitrate is used instead of lanthanum nitrate hexahydrate in step S3.

[0058] Example 5: This example provides a die-castable rare earth-doped aluminum alloy. The difference from Example 1 is that lanthanum acetate hydrate is used instead of lanthanum nitrate hexahydrate in step S3.

[0059] Example 6: This example provides a die-castable rare earth-doped aluminum alloy. The difference from Example 1 is that cerium acetate trihydrate is used instead of cerium nitrate hexahydrate in step S3.

[0060] Comparative Example 1: This comparative example provides a die-castable rare earth-doped aluminum alloy, which differs from Example 1 in that the rare earth modified composite powder is removed in step S4.

[0061] Comparative Example 2: This comparative example provides a die-castable rare earth-doped aluminum alloy. The difference from Example 1 is that step S3 is omitted, and the Ti2AlC-TiB2 powder prepared in step S2 is used instead of the rare earth modified composite powder prepared in step S4.

[0062] The performance of the die-castable rare-earth-doped aluminum alloys prepared in Examples 1-6 and Comparative Examples 1-2 was tested:

[0063] According to GB / T 228.1-2021 standard, the yield strength, tensile strength and elongation of die-castable rare earth doped aluminum alloy (width 16mm, thickness 4mm, length 100mm, conforming to the type A tensile specimen standard in GB / T 13822-2017) were tested.

[0064] Melt flowability test: A spiral die-cast sample with a zigzag shape was used, and the filling length was used to characterize the flowability of the alloy melt. Eight molds were die-cast for each set of parameters. After outliers were removed using the Grubbs test, the arithmetic mean of the remaining valid data was taken as the final test result to ensure the standardization and reliability of the data statistics.

[0065] The test results are shown in the table below:

[0066] Table 1 Performance Test Overview

[0067] project Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative Example 1 Comparative Example 2 Yield strength (MPa) 118 126 132 117 120 119 92 102 Tensile strength (MPa) 251 265 276 249 256 254 201 218 Elongation (%) 7.0 6.2 5.3 7.1 7.3 7.2 8.2 5.5 Liquidity (mm) 1280 1220 1150 1195 1220 1210 1350 980

[0068] As shown in Table 1, the yield strength of Examples 1-6 is higher than that of Comparative Examples 1-2, and the yield strength of Examples 1-3 shows an increasing trend. This may be because Comparative Example 1 did not introduce the Ti2AlC-TiB2 ceramic reinforcing phase and relied solely on matrix alloying elements for strengthening, resulting in weak deformation resistance. Comparative Example 2 directly added unmodified Ti2AlC-TiB2 powder, resulting in poor wettability between ceramic particles and the aluminum matrix and weak interfacial bonding. The applied load could not be effectively transferred to the ceramic phase, and the dispersion strengthening effect was not fully released. In contrast, Examples 1-6 constructed a rare earth oxide modified layer on the surface of ceramic particles through rare earth salt complexation loading and argon-protected calcination, which improved the interfacial wettability of the two phases and strengthened the interfacial bonding strength. This allowed the Ti2AlC-TiB2 particles to fully exert their dislocation pinning and load transfer effects, and the alloy yield strength was improved through the synergistic effect of dispersion strengthening and grain refinement strengthening.

[0069] As shown in Table 1, the tensile strength of Examples 1-6 is higher than that of Comparative Examples 1-2. This may be because Comparative Example 1 lacks a ceramic phase to share the load, resulting in a low matrix bearing capacity. In Comparative Example 2, the unmodified ceramics are prone to agglomeration, leading to easy initiation and rapid propagation of cracks at the interface, resulting in premature fracture. The modified ceramics in Examples 1-6 are uniformly dispersed and have a strong interface, effectively sharing the load. Rare earth elements have both melt purification and microstructure modification effects, reducing defects and improving the morphology of harmful phases, which, combined with grain refinement, enhances the fracture bearing capacity of the alloy.

[0070] As shown in Table 1, the elongation of Examples 1-6 is slightly lower than that of Comparative Example 1 without ceramic phase, but significantly higher than that of Comparative Example 2 with direct addition of unmodified ceramic powder. This may be because the ceramic phase itself restricts the plastic deformation of the matrix to a certain extent, while the rare earth modified layer effectively improves the bonding state of the two-phase interface, reduces interface debonding and microcrack initiation, and greatly alleviates the deterioration effect of the ceramic phase on plasticity. This allows the alloy to maintain a usable level of plasticity while significantly improving its strength, thus meeting the requirements for use of die-cast components.

[0071] As shown in Table 1, the melt flowability of Examples 1-6 is significantly higher than that of Comparative Example 2, and is generally close to that of Comparative Example 1. Among them, the flowability of Examples 1-3 decreases slightly with the increase of ceramic phase addition. This may be because Comparative Example 1 has no ceramic particles to obstruct the flow, resulting in low melt viscosity and the best filling flowability. In contrast, the unmodified Ti2AlC-TiB2 particles in Comparative Example 2 are prone to agglomeration, which significantly increases the melt viscosity and disrupts the flow field, leading to a significant decrease in filling capacity and making it unsuitable for die casting of complex structures. The rare earth oxide modification layer on the surface of the ceramic particles in Examples 1-6 effectively improves the wettability of the two-phase interface, reduces the interfacial resistance between the particles and the melt, and makes the ceramic phase uniformly dispersed. The increase in melt viscosity is controllable, so the flowability is much better than that of the unmodified Comparative Example 2, and only slightly lower than that of Comparative Example 1 without ceramics. This can meet the filling requirements of high-pressure die casting. Among them, the particles modified with organic rare earth salts have better dispersibility and have less impact on melt flowability, showing better die casting adaptability.

[0072] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0073] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for preparing a die-castable rare-earth-doped aluminum alloy, characterized in that, Step 1: Titanium powder, aluminum powder, boron carbide powder, and anhydrous ethanol are wet-milled, dried, and sieved to obtain a mixed powder; the mixed powder is hot-pressed and sintered under argon protection, then crushed, sieved, and dried to obtain Ti2AlC-TiB2 powder; lanthanum salt, cerium salt, citric acid, and Ti2AlC-TiB2 powder are mixed and ground, dried, and calcined under argon protection to obtain rare earth modified composite powder; Step 2: Melt and adjust the composition of pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy in stages. After powder spraying and refining, add rare earth modified composite powder accounting for 5-8% of the total mass of the melt and stir for 10 minutes to obtain a clean aluminum alloy melt. Step 3: Transfer the molten aluminum alloy into a die-casting machine for die casting to obtain a die-castable rare earth-doped aluminum alloy.

2. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 1, characterized in that, The specific preparation process of the mixed powder in step one is as follows: Titanium powder, aluminum powder, and boron carbide powder were loaded into an agate ball mill jar in a mass ratio of 4:1.2:

1. Anhydrous ethanol was added, with a mass ratio of anhydrous ethanol to raw material powder of 3:

10. The grinding balls were made of agate with a diameter of 3-12 mm, and the mass ratio of grinding balls to the material to be ground was 3:

1. The mixture was wet-milled using a planetary ball mill for 12-14 hours, dried, cooled to room temperature, and sieved to obtain a mixed powder.

3. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 1, characterized in that, The specific preparation process of the Ti2AlC-TiB2 powder mentioned in step one is as follows: BN powder is uniformly coated on the inner wall of a graphite hot pressing mold as a release agent. The mixed powder is then filled into the mold and sent into a hot pressing furnace as a whole. Under argon protection, the temperature is raised to 1350-1400℃ at a heating rate of 10℃ / min and held at 30-40MPa axial pressure for 1-2 hours. The furnace is then cooled to room temperature to obtain Ti2AlC-TiB2 sintered blocks. These blocks are then crushed into micron-sized powders by a jaw crusher and planetary ball mill, sieved, and dried to obtain Ti2AlC-TiB2 powder.

4. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 1, characterized in that, The specific preparation process of the rare earth modified composite powder in step one is as follows: Lanthanum salt, cerium salt, and Ti2AlC-TiB2 powder were added to a reaction vessel, citric acid monohydrate was added, and the mixture was transferred to an agate mortar and ground for 20-30 minutes. The mixture was then placed in a muffle furnace and heated to 800-820℃ under argon protection and calcined for 3-4 hours. The mixture was then allowed to cool naturally to room temperature. After grinding and sieving, rare earth modified composite powder was obtained.

5. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 4, characterized in that, The mass ratio of the lanthanum salt, cerium salt, Ti2AlC-TiB2 powder, and citric acid monohydrate is 4.3-6.5:4.3-7.1:100-150:4.2-6.4; The lanthanum salt is any one of lanthanum nitrate hexahydrate, anhydrous lanthanum nitrate, and lanthanum acetate hydrate; The cerium salt is either cerium nitrate hexahydrate or cerium acetate trihydrate.

6. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 1, characterized in that, The specific preparation process of the aluminum alloy melt in step two is as follows: Pure aluminum ingots, pure magnesium ingots, aluminum-manganese alloy, aluminum-chromium alloy, aluminum-silicon alloy, aluminum-gadolinium alloy, aluminum-iron alloy, and aluminum-lanthanum alloy are dried at 190-210℃ to remove moisture. The pure aluminum ingots are placed in a melting crucible and heated until completely melted. The melt temperature is raised to 750-800℃, and aluminum-zirconium alloy, aluminum-lanthanum alloy, and aluminum-chromium alloy are added sequentially, stirring until completely melted. The melt temperature is lowered to 720-750℃, and aluminum-silicon alloy, aluminum-manganese alloy, and aluminum-iron alloy are added, stirring until completely melted. The temperature is lowered to 700-720℃, and pure magnesium ingots and aluminum-gadolinium alloy are added. After all materials have melted and been thoroughly stirred, the composition is adjusted, and the temperature is raised to a refining temperature of 720-730℃. Argon gas carrying refining agent powder is introduced into the melt using a rotary jetting device for powder spraying refining, degassing, and slag removal. The refining agent is a salt flux that can adsorb impurities in the melt, and the amount added is 0.3%-2.0% of the total weight of the melt. After refining, the melt is allowed to stand for 10-15 minutes, and surface slag is removed. Rare earth modified composite powder accounting for 5-8% of the total mass of the melt is added and stirred for 10 minutes to obtain a clean aluminum alloy melt.

7. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 6, characterized in that, The process parameters for the rotary jet blowing are: rotor speed of 450-550 r / min, degassing time of 5-10 min, gas source pressure of 0.30-0.40 MPa, and gas flow rate of 10-20 L / min.

8. The method for preparing a die-castable rare-earth-doped aluminum alloy according to claim 1, characterized in that, The process parameters for die casting in step three are: injection speed of 1.5-3 m / s and casting pressure of 80-120 MPa.

9. A die-castable rare-earth-doped aluminum alloy, characterized in that, The die-castable rare-earth-doped aluminum alloy is prepared by any one of the preparation methods of claims 1-8, and the composition of the die-castable rare-earth-doped aluminum alloy by mass percentage is as follows: RE: 0.8-1%, Mn: 0.4-0.8%, Cr: 0.02-0.18%, Mg: 0.1-0.3%, Fe: 0.8-1.4%, Zr: 0.1-0.3%, Gd: 0.1-0.3%, Si: 0.08-0.28%, ceramic phase rare earth modified composite powder: 5-8%, balance is Al and unavoidable impurities.

10. A die-castable rare-earth-doped aluminum alloy according to claim 9, wherein the RE is composed of lanthanum and cerium in a mass ratio of 1:1.