Heat-resistant aluminum alloy and method for manufacturing the same

Abstract

The application belongs to the technical field of aluminum alloy materials, and provides a heat-resistant aluminum alloy and a preparation method thereof.A multi-element formula is designed, in which main alloying elements include copper (Cu), magnesium (Mg) and manganese (Mn), and micro-alloying elements include nickel (Ni), silver (Ag), zirconium (Zr), cerium (Ce), samarium (Sm), iron (Fe) and silicon (Si), so that material basis conditions can be created for the cultivation, formation and grain refinement of heat-stable phases and strengthening phases in the preparation process of the heat-resistant aluminum alloy; the main alloying elements and the micro-alloying elements can precipitate heat-stable phases in the preparation process, and at the same time, the cast grain structure is significantly refined, so that a grain structure with small grain size is obtained, and the degree of reduction of the mechanical properties of the aluminum alloy caused by the coarsening of partially precipitated phases under high-temperature conditions is reduced.

Description

Technical Field

[0001] This invention belongs to the field of aluminum alloy materials technology, specifically relating to a heat-resistant aluminum alloy and its preparation method. Background Technology

[0002] Heat-resistant aluminum alloys are aluminum alloys that possess sufficient oxidation resistance at high temperatures and resist plastic deformation (creep) and failure under prolonged temperature and load (dynamic and static loads). Due to their high thermal conductivity and low density, heat-resistant aluminum alloys have been widely used in the aerospace field, such as in aero-engine cylinder heads and pistons, aircraft skins, and can also be used to manufacture hot-end components and structural parts such as aircraft blades, helicopter propellers, and engine impellers.

[0003] Currently, Al-Cu-Mg-Ag series heat-resistant aluminum alloys with room temperature yield strength >400MPa, high-temperature yield strength >300MPa at 180℃, and adaptability to long-term service under medium temperature (180℃-200℃) and high stress (>200MPa) conditions have been developed. Although these heat-resistant aluminum alloys have good comprehensive mechanical properties at room temperature, their mechanical properties are poor at high temperatures (especially >300℃). For example, for the 7050 series aluminum alloys, which have high room temperature mechanical properties, the tensile strength at 200℃ and 300℃ is only 30% and 10% of that at room temperature, respectively. This severely limits their application scenarios under high-temperature conditions (especially in the 300℃-500℃ temperature range). Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention provides a heat-resistant aluminum alloy and its preparation method. By designing and controlling the content range of alloying elements and combining this invention with its preparation process, this invention can form a large number of thermally stable phases within the aluminum alloy matrix. The effective pinning of dislocations and grain boundaries by these thermally stable phases improves the heat resistance of the aluminum alloy. Simultaneously, by refining the grain size within the aluminum alloy matrix, the coarsening degree of the strengthening phases within the matrix is ​​reduced, further enhancing the heat resistance of the aluminum alloy.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] A heat-resistant aluminum alloy comprising the following components by mass percentage: Cu 4.5%-6.5%, Mg 0.5%-0.7%, Mn 0.3%-0.5%, Ni 0.20%-0.40%, Ag 0.5%-0.8%, Zr 0.08%-0.2%, Ce 0.6%-0.75%, Sm 0.30%-0.45%, Fe 0.65%-0.90%, Si 0.25%-0.45%, with the balance being Al and unavoidable impurity components.

[0007] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 4.5%, 4.6%, 4.7%, 4.8%, 4.9%, 5.0%, 5.1%, 5.2%, 5.3%, 5.4%, 5.5%, 5.6%, 5.7%, 5.8%, 5.9%, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, or 6.5% Cu element.

[0008] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.50%, 0.55%, 0.60%, 0.65%, or 0.70% Mg.

[0009] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.30%, 0.35%, 0.40%, 0.45%, or 0.50% Mn element.

[0010] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.20%, 0.25%, 0.30%, 0.35%, or 0.40% Ni.

[0011] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, or 0.80% Ag element.

[0012] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.08%, 0.10%, 0.12%, 0.15%, 0.16%, 0.18%, or 0.20% Zr element.

[0013] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.60%, 0.65%, 0.70%, or 0.75% Ce element.

[0014] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.30%, 0.35%, 0.40%, or 0.45% Sm element.

[0015] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, or 0.90% Fe element.

[0016] According to an embodiment of the present invention, the heat-resistant aluminum alloy comprises 0.25%, 0.30%, 0.35%, 0.40%, or 0.45% Si.

[0017] According to an embodiment of the present invention, the sum of the mass percentages of Cu, Mg, and Mn elements (Cu + Mg + Mn) is 6.0%-7.3%, for example, 6.0%, 6.1%, 6.2%, 6.3%, 6.4%, 6.5%, 6.6%, 6.7%, 6.8%, 6.9%, 7.0%, 7.1%, 7.2%, or 7.3%. Studies have found that when the sum of the mass percentages of Cu, Mg, and Mn elements (Cu + Mg + Mn) in the heat-resistant aluminum alloy is 6.0%-7.3%, the obtained aluminum alloy matrix can form phases such as Al6Mn, Al2Cu, Mg5Si6, AlCuMgSi, Al2CuMg, AlCuMn, and Al... 12 CuMn2 phase, Al 20 Strengthening phases such as Cu2Mn3 and others can significantly improve the mechanical properties of aluminum alloys at room temperature; some of these phases are precipitated phases such as Mg5Si6, AlCuMgSi, and Al... 12 CuMn2 phase also has high temperature resistance, which can prevent the strengthening phase from coarsening in the aluminum alloy matrix during heating, and help improve the mechanical properties of aluminum alloys under high temperature conditions.

[0018] According to an embodiment of the present invention, the mass ratio of Cu to Mg, Cu / Mg, is ≥8, for example, 8-12, such as 8, 8.5, 9, 9.5, 10, 10.5, 11, 11.5, or 12; the mass ratio of Ag to Mg, Ag / Mg, is 0.95-1.05, for example, 0.95, 0.98, 1, 1.02, or 1.05. Studies have found that when the mass ratio of Cu to Mg, Cu / Mg, is ≥8, and the mass ratio of Ag to Mg, Ag / Mg, is 0.95-1.05, it can promote the formation of an Ω phase in the aluminum alloy matrix, that is, Mg atoms and Ag atoms are wrapped around the outside of the Al2Cu phase, obtaining a microstructure strengthening phase with high heat resistance. At the same time, Mn atoms and Zr atoms in the aluminum alloy matrix will also gather around this strengthening phase, further improving the heat resistance stability of the aluminum alloy.

[0019] According to an embodiment of the present invention, the sum of the mass percentages of Fe and Si elements, Fe+Si, is 0.95%-1.25%, for example, 0.95%, 1%, 1.05%, 1.1%, 1.15%, 1.2%, or 1.25%. Studies have found that when the sum of the mass percentages of Fe and Si elements, Fe+Si, in the heat-resistant aluminum alloy is 0.95%-1.25%, a large amount of Al9FeNi phase and Al2O3 phase can precipitate in the obtained aluminum alloy matrix. 13 Heat-resistant and stable phases such as Fe4 phase and α-AlFeSi phase can firmly anchor the α-Al phase at the grain boundaries. Furthermore, the presence of various types of heat-resistant and stable phases can effectively pin and hinder the dislocation movement and grain boundary slip of the precipitated phases inside the aluminum alloy matrix, which is beneficial to improving the mechanical properties of heat-resistant aluminum alloys under high-temperature conditions.

[0020] According to an embodiment of the present invention, the mass ratio of Zr to Ce, Zr / Ce, is 0.13-0.25, for example, 0.13, 0.14, 0.15, 0.16, 0.18, 0.2, 0.22, 0.24, or 0.25; the mass ratio of Ce to Sm, Ce / Sm, is 1.8-2.2, for example, 1.8, 1.85, 1.9, 1.95, 2, 2.05, 2.1, 2.15, or 2.2; research has found that when the mass ratio of Zr to Ce, Zr / Ce, is 0. When the mass ratio of Ce to Sm is 1.8-2.2 (13-0.25), Sm, Zr, and Ce can precipitate a large amount of thermally stable Al3(Zr,Ce,Sm) phase in the aluminum alloy matrix. This Al3(Zr,Ce,Sm) phase has a network structure and can be uniformly distributed on the α-Al phase in the aluminum alloy matrix, improving the heat resistance of the aluminum alloy while also improving its mechanical properties and hardness. After interaction, Ce and Sm can segregate at the grain boundaries to form α-Ce3Al. 11 Phase, Al 11 Precipitated phases such as Sm3 and Al2Sm help to break dendrites inside the aluminum alloy matrix, refine the grain size and the size of the precipitated phases inside the aluminum alloy matrix, and the formation of finer grains can effectively suppress the coarsening of the strengthening phase in the aluminum alloy matrix under high temperature conditions, which is beneficial to obtaining aluminum alloys with high temperature resistance. Ce can also form AlFeSiCe phase with Fe and Si elements. AlFeSiCe phase can also effectively refine the grains of aluminum alloy, and similarly suppress the coarsening of the strengthening phase in the aluminum alloy matrix under high temperature conditions, thereby obtaining aluminum alloys with high temperature resistance.

[0021] According to an embodiment of the present invention, the mass ratio of Ni to Ag, Ni / Ag, is 0.4-0.65, for example, 0.4, 0.45, 0.5, 0.55, 0.6, or 0.65. When the mass ratio of Ni to Ag, Ni / Ag, is 0.4-0.65, on the one hand, an Al9FeNi heat-resistant phase can be formed in the aluminum alloy matrix, and the precipitation of the Al9FeNi heat-resistant phase can significantly improve the mechanical properties of the heat-resistant aluminum alloy under high-temperature conditions; on the other hand, it can also refine the eutectic structure inside the aluminum alloy matrix, improve the grain size and uniformity of the precipitated phase, thereby improving the mechanical properties of the heat-resistant aluminum alloy, especially the mechanical properties of the heat-resistant aluminum alloy under high-temperature conditions; furthermore, the addition of Ag can promote the in-situ precipitation of a high volume fraction of Al9FeNi heat-resistant phase at the grain boundaries, which is beneficial to improving the heat resistance of the aluminum alloy.

[0022] According to the embodiments of the present invention, traditional aluminum alloys have good comprehensive properties at room temperature, but their mechanical properties are significantly reduced at high temperatures. This is mainly because the strengthening phases formed between alloying elements inside the aluminum alloy (such as Al2Cu phase, Al2CuMg phase, etc.) gradually coarsen during heating, resulting in a significant decrease in the ability of grain boundary pinning dislocations, thereby causing a serious degradation of the high-temperature mechanical properties of the aluminum alloy. The inventors of this application unexpectedly discovered through research that by designing a multi-element formula including copper (Cu), magnesium (Mg), and manganese (Mn) as the main alloying elements, and nickel (Ni), silver (Ag), zirconium (Zr), cerium (Ce), samarium (Sm), iron (Fe), and silicon (Si) as microalloying elements, the material basis conditions for the cultivation, formation, and grain refinement of thermally stable and strengthening phases during the preparation of heat-resistant aluminum alloys can be created. During the preparation process (such as homogenization treatment, forging, solution quenching treatment, and aging treatment), these main alloying elements and microalloying elements can precipitate thermally stable phases and significantly refine the as-cast grain structure, obtaining a grain structure with fine grain size, thereby reducing the degree of reduction in the mechanical properties of aluminum alloys caused by the coarsening of partial precipitated phases under high-temperature conditions. Furthermore, the heat-resistant aluminum alloy of the present invention has thermally stable phases with multi-component structures formed at the grain boundaries, which have different heat resistance temperature ranges. The interaction between these thermally stable phases with different heat resistance temperature ranges can pin and hinder dislocation movement and grain boundary slip within the aluminum alloy matrix in a multi-level and all-round manner, inhibiting the recrystallization of the alloy structure within the aluminum alloy matrix. This effectively improves the high-temperature performance of the aluminum alloy (such as tensile strength and hardness), raising the upper limit of the service temperature of the heat-resistant aluminum alloy to 400°C, and significantly increasing the service temperature of the heat-resistant aluminum alloy.

[0023] According to an embodiment of the present invention, the heat-resistant aluminum alloy has a tensile strength of 500 MPa or higher and a hardness of 240 HV or higher at room temperature.

[0024] According to an embodiment of the present invention, at a temperature of 250°C, the tensile strength of the heat-resistant aluminum alloy is above 400 MPa and the hardness is above 235 HV.

[0025] According to an embodiment of the present invention, at a temperature of 350°C, the tensile strength of the heat-resistant aluminum alloy is above 300 MPa and the hardness is above 230 HV.

[0026] The present invention also provides a method for preparing the above-mentioned heat-resistant aluminum alloy, the method comprising the following steps:

[0027] (1) High-purity aluminum ingots, high-purity magnesium ingots, high-purity silver ingots, Al-Cu master alloy, Al-Mn master alloy, Al-Ni master alloy, Al-Zr master alloy, Al-Ce master alloy, Al-Sm master alloy, Al-Fe master alloy, and Al-Si master alloy are sequentially added to a melting furnace for melting to obtain aluminum alloy melt.

[0028] (2) The aluminum alloy melt from step (1) is refined, slag removed, degassed and filtered to obtain aluminum alloy melt;

[0029] (3) Cast the aluminum alloy melt from step (2) to prepare an aluminum alloy ingot;

[0030] (4) The aluminum alloy ingot from step (3) is subjected to homogenization treatment, forging, solution quenching treatment and aging treatment to prepare the heat-resistant aluminum alloy.

[0031] According to an embodiment of the present invention, in step (1), the purity of the high-purity aluminum ingot is ≥99.99%. The purity of the high-purity magnesium ingot is ≥99.99%. The purity of the high-purity Ag ingot is ≥99.99%. The Al-Cu master alloy is, for example, an Al-20Cu master alloy or an Al-30Cu master alloy, and the purity of the Al-Cu master alloy is ≥99%, wherein the purity of the Al-Cu master alloy refers to the sum of the contents of Al and Cu elements in the master alloy. The Al-Mn master alloy is, for example, an Al-9Mn master alloy, an Al-10Mn master alloy, or an Al-11Mn master alloy, and the purity of the Al-Mn master alloy is ≥99%, wherein the purity of the Al-Mn master alloy refers to the sum of the contents of Al and Mn elements in the master alloy. The Al-Ni master alloy is, for example, an Al-10Ni master alloy or an Al-50Ni master alloy, with a purity ≥99%. The purity of the Al-Ni master alloy refers to the sum of the contents of Al and Ni elements in the master alloy. The Al-Si master alloy is, for example, an Al-10Si master alloy, an Al-12Si master alloy, or an Al-50Si master alloy, with a purity ≥99%. The purity of the Al-Si master alloy refers to the sum of the contents of Al and Si elements in the master alloy. The Al-Ce master alloy is, for example, an Al-6Ce master alloy, an Al-10Ce master alloy, or an Al-20Ce master alloy, with a purity ≥99%. The purity of the Al-Ce master alloy refers to the sum of the contents of Al and Ce elements in the master alloy. The Al-Sm master alloy is, for example, an Al-5Sm master alloy, an Al-10Sm master alloy, or an Al-15Sm master alloy, wherein the purity of the Al-Sm master alloy is ≥99%, and the purity of the Al-Sm master alloy refers to the sum of the contents of Al and Sm elements in the master alloy. The Al-Zr master alloy is, for example, an Al-4Zr master alloy, an Al-5Zr master alloy, or an Al-6Zr master alloy, wherein the purity of the Al-Zr master alloy is ≥99%, and the purity of the Al-Zr master alloy refers to the sum of the contents of Al and Zr elements in the master alloy. The Al-Fe master alloy is, for example, an Al-5Fe master alloy or an Al-10Fe master alloy, wherein the purity of the Al-Fe master alloy is ≥99%, and the purity of the Al-Fe master alloy refers to the sum of the contents of Al and Fe elements in the master alloy.

[0032] According to an embodiment of the present invention, in step (1), the smelting process is as follows: high-purity aluminum ingots, high-purity silver ingots and Al-Cu master alloys are simultaneously added to a smelting furnace and smelted at 790-800°C for 20-30 minutes; the smelting temperature is reduced to 780-790°C, and Al-Mn master alloys, Al-Ni master alloys, Al-Zr master alloys and Al-Fe master alloys are added to the smelting furnace and smelted for 10-30 minutes; the smelting temperature is reduced to 750-760°C, and Al-Ce master alloys, Al-Sm master alloys and Al-Si master alloys are added to the smelting furnace and smelted for 10-30 minutes; the smelting temperature is reduced to 720-740°C, and high-purity magnesium ingots are added and smelted for another 15-25 minutes. The above-mentioned smelting operation can effectively avoid the burn-off of low-melting-point metal elements and ensure the full dissolution of high-melting-point metal elements. More importantly, by adding different alloy raw materials in different smelting temperature ranges, it is beneficial to precipitate a high volume fraction of thermally stable phase in the aluminum alloy matrix, thereby significantly improving the heat resistance of the aluminum alloy.

[0033] According to an embodiment of the present invention, in step (2), the refining, slag removal, degassing and filtration processes are achieved by the cooperation of a settling furnace, a slag removal spoon, an online degassing device and a filtration device; for example, refining is carried out in a settling furnace, the slag removal spoon is used to remove impurities such as oxide inclusions at the top of the settling furnace, an online degassing device is set at the bottom of the settling furnace for degassing, and the filtration device is used to filter the aluminum alloy melt.

[0034] According to an embodiment of the present invention, in step (2), a refining agent and high-purity argon are used as the refining medium. The purity of the high-purity argon is not less than 99.999%, and the flow rate of the high-purity argon is 400-700 L / h, for example, 400 L / h, 450 L / h, 500 L / h, 550 L / h, 600 L / h, 650 L / h, or 700 L / h. The introduction time of the high-purity argon is 10-15 min. The refining agent comprises the following parts by weight. The components are: 40-80 parts by weight of C2Cl6, 5-20 parts by weight of CaCO3, 5-20 parts by weight of MgSO4, 5-10 parts by weight of CaCl2, and 5-10 parts by weight of Al2O3; the refining agent is added at a rate of 3-8 kg / min, for example, 3 kg / min, 4 kg / min, 5 kg / min, 6 kg / min, 7 kg / min or 8 kg / min; the refining agent is added at a time of 10-15 min.

[0035] According to an embodiment of the present invention, in step (2), a rotary jet degassing device is used to degas the aluminum alloy melt, using high-purity argon as the degassing medium. The nozzle rotation speed is 350-550 r / min, for example, 350 r / min, 400 r / min, 450 r / min, 500 r / min, or 550 r / min; the high-purity argon flow rate is 500-800 L / h, for example, 500 L / h, 600 L / h, 700 L / h, or 800 L / h; and the degassing time is 15-20 min. By selecting the above degassing process, hydrogen dissolved in the aluminum alloy melt can be effectively removed, reducing the hydrogen content in the aluminum alloy melt to less than 0.10 μg / g, which is beneficial for obtaining high-quality aluminum alloy melt.

[0036] According to an embodiment of the present invention, in step (2), a two-stage plate filter with a resolution of 30 PPI + 50 PPI is used to filter the aluminum alloy melt. Compared with a single-stage plate filter with a resolution of 60 PPI, the two-stage plate filter with a resolution of 30 PPI + 50 PPI of the present invention can effectively filter out the tiny solid inclusions in the aluminum alloy melt, which is beneficial to obtaining high-quality aluminum alloy melt.

[0037] According to an embodiment of the present invention, in step (2), it was found that by refining, slag removal, degassing and filtering the aluminum alloy melt in the above manner, the hydrogen content in the aluminum alloy melt can be significantly reduced to below 0.10 μg / g. It can also significantly reduce the small solid inclusions present in the aluminum alloy melt. By reducing the hydrogen content and small solid inclusions in the aluminum alloy melt, factors that have an adverse effect on the performance of the aluminum alloy are eliminated. Furthermore, it can effectively promote the nucleation of the aluminum alloy matrix during the solidification process, improve the grain refinement effect in the aluminum alloy matrix, thereby inhibiting the coarsening of the precipitated phase under high temperature conditions and significantly improving the heat resistance of the aluminum alloy.

[0038] According to an embodiment of the present invention, in step (3), the aluminum alloy melt flows evenly into the crystallizer after passing through the diversion tank. When the alloy liquid level in the crystallizer reaches a height of 20-30 mm above the top of the crystallizer, the casting machine is started for billet casting. The casting speed is 90-120 mm / min, for example, 90 mm / min, 95 mm / min, 100 mm / min, 105 mm / min, 110 mm / min, 115 mm / min or 120 mm / min. The casting speed is 700-715℃, for example, 700℃, 705℃, 710℃, or 715℃; the cooling water flow rate is 120-145L / min, for example, 120L / min, 125L / min, 130L / min, 135L / min, 140L / min, or 145L / min; the cooling water pressure is 0.06MPa-0.09MPa, for example, 0.06MPa, 0.07MPa, 0.08MPa, or 0.09MPa. Studies have found that when using a semi-continuous casting method that meets the above parameters, high-quality aluminum alloy ingots can be obtained quickly, saving preparation time and reducing production costs. Furthermore, the grain structure within the aluminum alloy matrix can be refined, resulting in smaller grains. Additionally, the obtained aluminum alloy ingots are free from defects such as tensile cracking.

[0039] According to an embodiment of the present invention, in step (3), during the casting process, an ultrasonic probe can be inserted into the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer respectively to apply ultrasonic crushing treatment to the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer; the frequency of the ultrasound is 25-50kHz, for example, 25kHz, 30kHz, 35kHz, 40kHz, 45kHz or 50kHz; the power of the ultrasound is 50-500W, for example, 50W, 100W, 150W, 200W, 250W, 300W, 350W, 400W or 450W. The ultrasonic crushing treatment can effectively remove the gas generated inside the alloy melt, improve the flow properties of the alloy melt, and accelerate the casting speed of the aluminum alloy ingot; the "cavitation" effect generated by the ultrasonic crushing treatment can also cause the solidified dendrites to break and refine the grains.

[0040] According to an embodiment of the present invention, in step (3), the aluminum alloy ingot is an aluminum alloy flat ingot or an aluminum alloy round ingot. Exemplarily, the aluminum alloy ingot is an aluminum alloy flat ingot with a thickness of 520 mm × 1620 mm (width) and / or an aluminum alloy round ingot with a diameter of 1000 mm.

[0041] According to an embodiment of the present invention, in step (4), the homogenization process is as follows: the obtained ingot is kept at 440-450℃ (e.g., 442℃, 443℃, 445℃, 446℃ or 448℃) for 10-18 hours (e.g., 10 hours, 12 hours, 14 hours, 15 hours, 16 hours or 18 hours), the temperature is raised to 490-500℃ (e.g., 490℃, 492℃, 494℃, 495℃, 496℃ or 498℃) within 4-8 minutes and kept at that temperature for 5-8 hours (e.g., 5 hours, 6 hours or 8 hours), the temperature is raised to 525-535℃ (e.g., 525℃, 526℃, 528℃, 530℃, 532℃ or 535℃) within 5-10 minutes and kept at that temperature for 25-30 hours (e.g., 25 hours, 26 hours, 28 hours or 30 hours); after the holding time is completed, it is cooled to room temperature with the furnace. Studies have found that when aluminum alloy ingots are held at temperatures between 440-450℃, coarse non-equilibrium phases and low-melting-point phases generated during the non-equilibrium cooling process of casting can be eliminated, preventing overburning of alloying elements under high-temperature conditions. When aluminum alloy ingots are held at temperatures between 490-500℃, the low-melting-point phases remaining after holding at the previous temperature range can be redissolved into the aluminum alloy matrix, preventing overburning at higher temperatures. When aluminum alloy ingots are held at temperatures between 525-535℃, the low-melting-point phases remaining in the aluminum alloy matrix can be redissolved, and uniform and fine precipitated strengthening phases can be precipitated. The homogenization process can completely dissolve a large number of coarse non-equilibrium phases (such as those formed by the enrichment of elements such as Cu, Mg, and Ag) existing at grain boundaries and within grains in the cast aluminum alloy matrix without burning alloying elements, obtaining uniform and fine precipitated strengthening phases, and ultimately achieving the purpose of composition homogenization.

[0042] According to an embodiment of the present invention, in step (4), the aluminum alloy ingot after homogenization is milled, and the milled ingot is heated to 460℃-480℃ (such as 460℃, 462℃, 465℃, 468℃, 470℃, 472℃, 474℃, 475℃, 476℃, 478℃ or 480℃) and kept at that temperature for 10-20 hours (such as 10 hours, 12 hours, 15 hours, 16 hours, 18 hours or 20 hours).

[0043] According to an embodiment of the present invention, in step (4), the initial forging temperature is 460℃-480℃, such as 460℃, 462℃, 465℃, 468℃, 470℃, 472℃, 474℃, 475℃, 476℃, 478℃, or 480℃; the final forging temperature is ≥350℃. The forging adopts two upsetting and two drawing processes, and the processing method of the two upsetting and two drawing processes is, in sequence, one upsetting, reversing drawing, two upsetting, reversing drawing, and squarening.

[0044] According to an embodiment of the present invention, the forging is specifically carried out by the following method:

[0045] 1) At a temperature of 460℃-480℃, the milled aluminum alloy ingot is subjected to one upsetting and one drawing process. The die pressing speed during the upsetting process is 30-35mm / s, and the die pressing speed during the drawing process is 30-35mm / s. The direction of the first upsetting is perpendicular to the direction of the first drawing. The height of the billet after the first upsetting is H / 2-H / 3. The diameter of the billet after the first drawing is (0.6-0.8)φ. H is the height of the milled aluminum alloy ingot, and φ is the diameter of the milled aluminum alloy ingot.

[0046] 2) Reheat the billet from step 1) in the furnace and hold it at 460℃-480℃ for 5-10 hours;

[0047] 3) The billet from step 2) is subjected to secondary upsetting, secondary drawing, and squaring in sequence; the die pressing speed during the upsetting process is 10-15 mm / s, the die pressing speed during the cross drawing process is 10-15 mm / s, the direction of the secondary upsetting is perpendicular to the direction of the secondary drawing, the direction of squaring is perpendicular to the direction of upsetting and parallel to the direction of drawing; and the height of the billet after the secondary upsetting is the same as the height of the billet after the primary upsetting, and the final forging temperature is controlled to be ≥350℃.

[0048] According to an embodiment of the present invention, research has found that when the forging is carried out at a temperature of 460℃-480℃, the original grain structure of the aluminum alloy ingot can be fully fragmented, which helps the uniform precipitation of thermally stable phases and strengthening phases at grain boundaries within the aluminum alloy matrix. Simultaneously, the aforementioned two-upsetting and two-drawing forging method can effectively increase the core deformation of the aluminum alloy ingot, which is beneficial for obtaining a heat-resistant aluminum alloy with a more uniform internal structure, finer grains, and better heat resistance. In particular, the forging method of the present invention first employs rapid deformation (die pressing speed of 30-35 mm / s) for a single upsetting and a single drawing, followed by slow deformation (die pressing speed of 10-15 mm / s) for a second upsetting and a second drawing. This forging method is more conducive to the full fragmentation of the original grain structure within the aluminum alloy ingot, resulting in smaller grains and the precipitation of thermally stable phases and strengthening phases at grain boundaries within the aluminum alloy matrix, thus further contributing to obtaining a heat-resistant aluminum alloy with superior heat resistance.

[0049] According to an embodiment of the present invention, in step (4), the solution quenching process is as follows: the forged aluminum alloy forging is heated to a temperature of 530-540℃, for example, 530℃, 532℃, 535℃, 536℃, 538℃ or 540℃; the holding time is 60-120min, for example, 60min, 70min, 80min, 90min, 100min, 110min or 120min; then water quenching is performed, the quenching water temperature is room temperature, and the quenching transfer time does not exceed 25s. Studies have found that when solution treatment is performed within this temperature range, a large number of solute atoms in the aluminum alloy matrix can be dissolved into the matrix, reaching a supersaturated state, so that more thermally stable phases and strengthening phases can precipitate at the grain boundaries in the aluminum alloy matrix during subsequent aging treatment.

[0050] According to an embodiment of the present invention, in step (4), the aging treatment includes a primary aging treatment and a secondary aging treatment. The temperature of the primary aging treatment is 170-190℃, for example, 170℃, 175℃, 180℃, 185℃ or 190℃; the time of the primary aging treatment is 10-25 hours, for example, 10 hours, 12 hours, 15 hours, 16 hours, 18 hours, 20 hours or 24 hours; the temperature of the secondary aging treatment is 220-240℃, for example, 220℃, 225℃, 230℃, 235℃ or 240℃; the time of the primary aging treatment is 20-30 hours, for example, 20 hours, 24 hours, 25 hours, 26 hours, 28 hours or 30 hours; the heating rate of the aging treatment is 60-70℃ / h, for example, 60℃ / h, 62℃ / h, 65℃ / h, 68℃ / h or 70℃ / h. For example, the furnace temperature is first raised to 170-190°C at a heating rate of 60-70°C / h and held for 10-25 hours. Then, the furnace temperature is raised to 220-240°C at a heating rate of 60-70°C / h and held for 20-30 hours. Subsequently, the furnace is cooled to room temperature. By controlling the heating rate of the aging treatment, aging treatment under a combination of variable and constant temperatures is achieved. This not only refines the grain size but also suppresses the coarsening of precipitates, resulting in a significant improvement in the mechanical and heat resistance properties of the aluminum alloy.

[0051] According to an embodiment of the present invention, in step (4), the time interval between the solution quenching treatment and the aging treatment is ≤40 min.

[0052] The beneficial effects of this invention are:

[0053] This invention provides a heat-resistant aluminum alloy and its preparation method. By designing a multi-element formula with main alloying elements including copper (Cu), magnesium (Mg), and manganese (Mn), and microalloying elements including nickel (Ni), silver (Ag), zirconium (Zr), cerium (Ce), samarium (Sm), iron (Fe), and silicon (Si), the material basis conditions for the cultivation, formation, and grain refinement of thermally stable and strengthening phases during the preparation of the heat-resistant aluminum alloy can be created. During the preparation process (such as homogenization treatment, forging, solution quenching treatment, and aging treatment), these main alloying elements and microalloying elements can precipitate thermally stable phases and significantly refine the as-cast grain structure, obtaining a fine-grained grain structure, thereby reducing the degree of mechanical property reduction of aluminum alloy caused by coarsening of partial precipitated phases under high-temperature conditions. The heat-resistant aluminum alloy of the present invention has thermally stable phases with multi-component structures formed at the grain boundaries, which also have different heat-resistant temperature ranges. The interaction between these thermally stable phases with different heat-resistant temperature ranges can pin and hinder dislocation movement and grain boundary slip in the aluminum alloy matrix in a multi-level and all-round way, inhibiting the recrystallization of the alloy structure in the aluminum alloy matrix, thereby effectively improving the high-temperature performance of the aluminum alloy (such as tensile strength and hardness), increasing the upper limit of the service temperature of the heat-resistant aluminum alloy to 400°C, and significantly improving the service temperature of the heat-resistant aluminum alloy. Attached Figure Description

[0054] Figure 1 The image shows the metallographic structure and primary phase morphology of the cast aluminum alloy in Example 1.

[0055] Figure 2 The image shows the metallographic structure and primary phase morphology of the aluminum alloy after homogenization treatment in Example 1. Detailed Implementation

[0056] The preparation method of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0057] Unless otherwise specified, the experimental methods used in the following examples are conventional methods; unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0058] Example 1

[0059] The method for preparing the heat-resistant aluminum alloy in this embodiment includes the following steps:

[0060] (1) Weigh high-purity aluminum ingots, high-purity magnesium ingots, high-purity silver ingots, Al-Cu master alloy, Al-Mn master alloy, Al-Ni master alloy, Al-Zr master alloy, Al-Ce master alloy, Al-Sm master alloy, Al-Fe master alloy, and Al-Si master alloy according to the mass percentage shown in Table 1. Then, put the high-purity aluminum ingots, high-purity silver ingots, and Al-Cu master alloy into the melting furnace at 795°C for 25 min. Reduce the melting temperature to 785°C and put the Al-Mn master alloy, Al-Ni master alloy, Al-Zr master alloy, and Al-Fe master alloy into the melting furnace for 20 min. Reduce the melting temperature to 755°C and put the Al-Ce master alloy, Al-Sm master alloy, and Al-Si master alloy into the melting furnace for 20 min. Reduce the melting temperature to 730°C and put the high-purity magnesium ingot into the furnace. Continue to melt for 20 min to obtain aluminum alloy melt.

[0061] (2) The aluminum alloy melt from step (1) is refined, slag removed, degassed, and filtered to obtain an aluminum alloy melt; wherein, a refining agent and high-purity argon are used as the refining medium, the purity of the high-purity argon is not less than 99.999%, the flow rate of the high-purity argon is 400 L / h, and the introduction time of the high-purity argon is 15 min; the refining agent includes the following components in parts by weight: 60 parts by weight of C2Cl6, 10 parts by weight of CaCO3, 10 parts by weight of MgSO4, 10 parts by weight of CaCl2, and 10 parts by weight of Al2O3; the addition rate of the refining agent is 8 kg / min; and the addition time of the refining agent is 10 min. A slag-removing spoon is used to remove oxide inclusions and other impurities from the surface of the refined aluminum alloy melt. A rotary jet degassing device was used to degas the molten aluminum alloy, using high-purity argon as the degassing medium. The nozzle speed was 350 r / min, the high-purity argon flow rate was 800 L / h, and the online degassing time was 15 min. A two-stage plate filter with a 30 PPI + 50 PPI filter was used to filter the molten aluminum alloy.

[0062] (3) After the aluminum alloy melt from step (2) flows evenly into the crystallizer through the diversion tank, when the alloy liquid level in the crystallizer reaches a height of 25 mm from the top of the crystallizer, the casting machine is started to perform billet casting to prepare an aluminum alloy flat ingot with a thickness of 520 mm × 1620 mm (width); wherein, the casting speed is 90 mm / min; the casting temperature is 700℃; the cooling water volume is 120 L / min; and the cooling water pressure is 0.06 MPa.

[0063] (4) Hold the aluminum alloy ingot from step (3) at 440°C for 18 hours, raise the temperature to 490°C for the first time within 4-8 minutes and hold for 8 hours, raise the temperature to 525°C for the second time within 5-10 minutes and hold for 25 hours; after the holding period, cool it to room temperature with the furnace.

[0064] (5) The aluminum alloy ingot after homogenization treatment in step (4) is milled, and the milled ingot is heated to 480°C and kept at that temperature for 20 hours.

[0065] (6) At a temperature of 480℃, the aluminum alloy ingot after milling in step (5) is subjected to one upsetting and one drawing in sequence; the die pressing speed during the upsetting process is 30mm / s, the die pressing speed during the drawing process is 30mm / s, the direction of the first upsetting is perpendicular to the direction of the first drawing; and the height of the billet after the first upsetting is H / 2; the diameter of the billet after the first drawing is (0.8)φ; H is the height of the aluminum alloy ingot after milling, and φ is the diameter of the aluminum alloy ingot after milling. The billet is reheated in the furnace and held at 480℃ for 10 hours. The held billet is then subjected to secondary upsetting, secondary drawing, and squaring in sequence. During the upsetting process, the die pressing speed is 10mm / s, and during the cross drawing process, the die pressing speed is 10mm / s. The direction of the secondary upsetting is perpendicular to the direction of the secondary drawing, and the direction of squaring is perpendicular to the direction of upsetting and parallel to the direction of drawing. The height of the billet after the secondary upsetting is the same as the height of the billet after the primary upsetting, and the final forging temperature is controlled to be ≥350℃.

[0066] (7) Heat the aluminum alloy forging after step (6) to a temperature of 530°C and hold for 60 minutes for solution treatment; then perform water quenching at room temperature and the quenching transfer time shall not exceed 25 seconds.

[0067] (8) The forgings after solution quenching in step (7) are subjected to aging treatment. The aging treatment involves heating the furnace to 190°C at a heating rate of 60°C / h and holding for 15 hours, then heating the furnace to 240°C at a heating rate of 60°C / h and holding for 20 hours, and then cooling the furnace to room temperature.

[0068] Examples 2-6

[0069] The preparation method of the heat-resistant aluminum alloy is the same as that in Example 1, except that the composition of the alloying elements is different from that in Example 1, as shown in Table 1.

[0070] Example 7

[0071] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0072] During the casting process, an ultrasonic probe is inserted into the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer to apply ultrasonic crushing treatment to the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer; the frequency of the ultrasound is 50kHz; the power of the ultrasound is 500W.

[0073] Since ultrasonic crushing treatment was introduced in Example 7 during the casting process, the ultrasonic crushing treatment can effectively remove the gas generated inside the alloy liquid, improve the flow properties of the alloy liquid, and accelerate the casting speed of aluminum alloy ingots; the "cavitation" effect generated by the ultrasonic crushing treatment can also cause the solidified dendrites to break and the grains to be refined, which is conducive to obtaining aluminum alloys with excellent heat resistance.

[0074] Comparative Examples 1-2

[0075] The preparation method of the heat-resistant aluminum alloy is the same as that in Example 1, except that the composition of the alloying elements is different from that in Example 1, as shown in Table 1.

[0076] Comparative Example 3

[0077] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0078] (1) High-purity aluminum ingots, high-purity silver ingots, Al-Cu master alloy, Al-Mn master alloy, Al-Ni master alloy, Al-Zr master alloy, Al-Ce master alloy, Al-Sm master alloy, Al-Fe master alloy, and Al-Si master alloy are simultaneously put into a melting furnace and melted at 785°C for 100 min; the melting temperature is reduced to 730°C, high-purity magnesium ingots are added, and melting is continued for 20 min to obtain aluminum alloy melt.

[0079] Since Comparative Example 3 involves adding all alloy raw materials except for high-purity magnesium ingots into the melting furnace at once, this requires not only a longer melting time but also a higher melting temperature. This operation not only wastes energy but also fails to guarantee the burn-off of low-melting-point metal elements and the full dissolution of high-melting-point metal elements. This is not conducive to the precipitation of high-volume-fraction thermally stable phases in the heat-resistant aluminum alloy and can easily lead to a reduction in the thermal stability of the heat-resistant aluminum alloy.

[0080] Comparative Example 4

[0081] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0082] (2) The aluminum alloy melt from step (1) is refined, slag removed, degassed, and filtered to obtain an aluminum alloy melt. High-purity argon is used as the refining medium, with a purity of not less than 99.999%, a flow rate of 400 L / h, and a flow time of 15 min. A slag-removing spoon is used to remove oxide inclusions and other impurities from the surface of the refined aluminum alloy melt. A rotary jet degassing device is used to degas the aluminum alloy melt, using high-purity argon as the degassing medium. The nozzle speed is 250 r / min, the high-purity argon flow rate is 400 L / h, and the online degassing time is 15 min. A 60 PPI single-stage plate filter is used to filter the aluminum alloy melt.

[0083] Since no refining agent was introduced during the refining process of Comparative Example 4, and only a single-stage plate filter was used for filtration, the hydrogen content in the aluminum alloy melt could not be significantly reduced. The hydrogen content in the obtained aluminum alloy melt was about 0.20 μg / g. Due to the presence of hydrogen and tiny solid inclusions in the aluminum alloy melt, the quality of the aluminum alloy melt decreased significantly. This would accelerate the coarsening of the precipitated phase in the aluminum alloy matrix under high temperature conditions and significantly deteriorate the heat resistance of the aluminum alloy.

[0084] Comparative Example 5

[0085] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0086] (3) After the aluminum alloy melt from step (2) flows evenly into the crystallizer through the diversion tank, when the alloy liquid level in the crystallizer reaches a height of 25 mm from the top of the crystallizer, the casting machine is started to perform billet casting to prepare an aluminum alloy flat ingot of 520 mm (thickness) × 1620 mm (width); wherein, the casting speed is 50 mm / min; the casting temperature is 700℃; the cooling water volume is 60 L / min and the cooling water pressure is 0.02 MPa.

[0087] Compared with the casting parameters of Example 1, the solidification rate of the aluminum alloy melt in the crystallizer of Comparative Example 5 is relatively slow. This makes it impossible to refine the grains inside the aluminum alloy matrix, which is not conducive to suppressing the coarsening of the strengthening phase inside the aluminum alloy matrix, and will also deteriorate the heat resistance of the aluminum alloy material under high temperature conditions.

[0088] Comparative Example 6

[0089] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0090] (4) Hold the aluminum alloy ingot from step (3) at 420°C for 18 hours, raise the temperature to 465°C for the first time within 4-8 minutes and hold for 8 hours, raise the temperature to 485°C for the second time within 5-10 minutes and hold for 25 hours; after the holding period, cool it to room temperature with the furnace.

[0091] Comparative Example 6 uses a relatively low temperature for homogenization treatment. At this temperature, it is impossible to effectively eliminate the coarse non-equilibrium phase and low-melting-point phase generated during the non-equilibrium cooling process of melting and casting. As a result, the aluminum alloy matrix prepared in this way cannot obtain uniform and fine precipitated strengthening phases, thus weakening the purpose of homogenization treatment.

[0092] Comparative Example 7

[0093] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0094] (6) At a temperature of 420℃, the aluminum alloy ingot after milling in step (5) is subjected to one upsetting and one drawing in sequence; the die pressing speed during the upsetting process is 20mm / s, the die pressing speed during the drawing process is 20mm / s, the direction of the first upsetting is perpendicular to the direction of the first drawing; and the height of the billet after the first upsetting is H / 2; the diameter of the billet after the first drawing is (0.8)φ; H is the height of the aluminum alloy ingot after milling, and φ is the diameter of the aluminum alloy ingot after milling. The billet is reheated in the furnace and held at 420℃ for 10 hours. The held billet is then subjected to secondary upsetting, secondary drawing, and squaring in sequence. The die pressing speed during the upsetting process is 20mm / s, and the die pressing speed during the cross drawing process is 20mm / s. The direction of the secondary upsetting is perpendicular to the direction of the secondary drawing, and the direction of squaring is perpendicular to the direction of upsetting and parallel to the direction of drawing. The height of the billet after the secondary upsetting is the same as the height of the billet after the primary upsetting, and the final forging temperature is controlled to be ≥350℃.

[0095] The forging temperature of Comparative Example 7 is significantly lower than that of Example 1. This is not conducive to the full fragmentation of the grain structure in the aluminum alloy matrix, nor to the uniform precipitation of the thermally stable phase and strengthening phase at the grain boundaries in the aluminum alloy matrix. At the same time, the forging process of Comparative Example 7 adopts a uniform deformation method (the pressing speed of the die) to perform one upsetting, one drawing, two upsetting and two drawing. Such a forging method is also not conducive to the full fragmentation of the original grain structure in the aluminum alloy ingot, smaller grains, and the precipitation of the thermally stable phase and strengthening phase at the grain boundaries in the aluminum alloy matrix. Therefore, it is impossible to obtain an aluminum alloy with excellent heat resistance.

[0096] Comparative Example 8

[0097] The composition of the alloying elements is the same as in Example 1, the only difference being the preparation method of the heat-resistant aluminum alloy, as detailed below:

[0098] (7) Heat the aluminum alloy forging after step (6) to a temperature of 490℃ and hold for 60 minutes for solution treatment; then perform water quenching at room temperature and the quenching transfer time does not exceed 25 seconds.

[0099] The solution treatment temperature of Comparative Example 8 is much lower than that of Example 1. Within this temperature range, it is not possible to effectively dissolve a large number of solute atoms in the aluminum alloy matrix into the matrix, which is not conducive to the formation of thermally stable phases and strengthening phases at the grain boundaries in the aluminum alloy matrix during subsequent aging, thus hindering the improvement of the heat resistance of the aluminum alloy.

[0100] Table 1. Alloy element composition of the examples and comparative examples

[0101]

[0102] Table 2 Performance test results of aluminum alloys in the examples and comparative examples

[0103]

[0104] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A heat-resistant aluminum alloy, wherein, The heat-resistant aluminum alloy comprises the following components by mass percentage: Cu 4.5%-6.5%, Mg 0.5%-0.7%, Mn 0.3%-0.5%, Ni 0.20%-0.40%, Ag 0.5%-0.8%, Zr 0.08%-0.2%, Ce 0.6%-0.75%, Sm 0.30%-0.45%, Fe 0.65%-0.90%, Si 0.25%-0.45%, with the balance being Al and unavoidable impurities. The sum of the mass percentages of Cu, Mg, and Mn (Cu + Mg + Mn) is 6.0%-7.3%; the mass ratio of Cu to Mg (Cu / Mg) is ≥8; the mass ratio of Ag to Mg (Ag / Mg) is 0.95-1.05; the sum of the mass percentages of Fe and Si (Fe + Si) is 0.95%-1.25%; the mass ratio of Zr to Ce (Zr / Ce) is 0.13-0.25; the mass ratio of Ce to Sm (Ce / Sm) is 1.8-2.2; and the mass ratio of Ni to Ag (Ni / Ag) is 0.4-0.

65. At room temperature, the tensile strength of the heat-resistant aluminum alloy is above 500 MPa; at a temperature of 250°C, the tensile strength of the heat-resistant aluminum alloy is above 400 MPa.

2. The heat-resistant aluminum alloy according to claim 1, wherein, At room temperature, the hardness of the heat-resistant aluminum alloy is above 240 HV; And / or, at a temperature of 250°C, the hardness of the heat-resistant aluminum alloy is above 235HV.

3. The heat-resistant aluminum alloy according to claim 1 or 2, wherein, At a temperature of 350℃, the tensile strength of the heat-resistant aluminum alloy is above 300MPa and the hardness is above 230HV.

4. A method for preparing the heat-resistant aluminum alloy according to any one of claims 1-3, the method comprising the following steps: (1) High-purity aluminum ingots, high-purity magnesium ingots, high-purity silver ingots, Al-Cu master alloy, Al-Mn master alloy, Al-Ni master alloy, Al-Zr master alloy, Al-Ce master alloy, Al-Sm master alloy, Al-Fe master alloy, and Al-Si master alloy are sequentially added to a melting furnace for melting to obtain aluminum alloy melt. (2) The aluminum alloy melt from step (1) is refined, slag removed, degassed and filtered to obtain aluminum alloy melt; (3) Cast the aluminum alloy melt from step (2) to prepare an aluminum alloy ingot; (4) The aluminum alloy ingot from step (3) is subjected to homogenization treatment, forging, solution quenching treatment and aging treatment to prepare the heat-resistant aluminum alloy.

5. The preparation method according to claim 4, wherein, In step (1), the smelting process is as follows: high-purity aluminum ingots, high-purity silver ingots, and Al-Cu master alloys are simultaneously added to a smelting furnace and smelted at 790-800℃ for 20-30 minutes; the smelting temperature is reduced to 780-790℃, and Al-Mn master alloys, Al-Ni master alloys, Al-Zr master alloys, and Al-Fe master alloys are added to the smelting furnace and smelted for 10-30 minutes; the smelting temperature is reduced to 750-760℃, and Al-Ce master alloys, Al-Sm master alloys, and Al-Si master alloys are added to the smelting furnace and smelted for 10-30 minutes; the smelting temperature is reduced to 720-740℃, and high-purity magnesium ingots are added and smelted for another 15-25 minutes.

6. The preparation method according to claim 4, wherein, In step (2), a refining agent and high-purity argon are used as the refining medium. The purity of the high-purity argon is not less than 99.999%, and the flow rate of the high-purity argon is 400-700 L / h. The introduction time of the high-purity argon is 10-15 min. The refining agent comprises the following components in parts by weight: 40-80 parts by weight of C2Cl6, 5-20 parts by weight of CaCO3, 5-20 parts by weight of MgSO4, 5-10 parts by weight of CaCl2, and 5-10 parts by weight of Al2O3. The addition rate of the refining agent is 3-8 kg / min, and the addition time of the refining agent is 10-15 min. And / or, in step (2), a rotary jet degassing device is used to degas the aluminum alloy melt, with high-purity argon as the degassing medium, the nozzle speed is 350-550 r / min; the high-purity argon flow rate is 500-800 L / h; and the degassing time is 15-20 min. And / or, in step (2), a two-stage plate filter device with 30PPI+50PPI is used to filter the aluminum alloy melt.

7. The preparation method according to claim 4, wherein, In step (3), the aluminum alloy melt flows evenly into the crystallizer after passing through the diversion tank. When the alloy liquid level in the crystallizer reaches a height of 20-30 mm above the top of the crystallizer, the casting machine is started for billet casting. The casting speed is 90-120 mm / min; the casting temperature is 700-715℃; the cooling water volume is 120-145 L / min; and the cooling water pressure is 0.06 MPa-0.09 MPa.

8. The preparation method according to claim 7, wherein, In step (3), during the casting process, an ultrasonic probe is inserted into the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer respectively to apply ultrasonic crushing treatment to the aluminum alloy melt in the diversion tank and the aluminum alloy melt in the crystallizer; the frequency of the ultrasonic is 25-50kHz; the power of the ultrasonic is 50-500W.

9. The preparation method according to claim 4, wherein, In step (4), the homogenization process is as follows: the obtained ingot is kept at 440-450℃ for 10-18 hours, heated to 490-500℃ in 4-8 minutes and kept at that temperature for 5-8 hours, heated to 525-535℃ in 5-10 minutes and kept at that temperature for 25-30 hours; after the holding period, it is cooled to room temperature with the furnace. And / or, in step (4), the initial temperature of the forging is 460℃-480℃; the final forging temperature of the forging is ≥350℃; the forging adopts two upsetting and two drawing, and the processing method of the two upsetting and two drawing is, in sequence, one upsetting, reversing drawing, two upsetting, reversing drawing, and square forming; And / or, in step (4), the solution quenching process is as follows: the forged aluminum alloy forging is heated to a temperature of 530-540℃; the holding time is 60-120min; and then water quenching is performed, the water temperature for quenching is room temperature, and the quenching transfer time does not exceed 25s. And / or, in step (4), the aging treatment includes a primary aging treatment and a secondary aging treatment. The temperature of the primary aging treatment is 170-190℃; the time of the primary aging treatment is 10-25 hours; the temperature of the secondary aging treatment is 220-240℃; the time of the primary aging treatment is 20-30 hours; and the heating rate of the aging treatment is 60-70℃ / h.

10. The preparation method according to claim 9, wherein, The forging process is specifically carried out using the following method: 1) At a temperature of 460℃-480℃, the milled aluminum alloy ingot is subjected to one upsetting and one drawing process. The die pressing speed during the upsetting process is 30-35mm / s, and the die pressing speed during the drawing process is 30-35mm / s. The direction of the first upsetting is perpendicular to the direction of the first drawing. The height of the billet after the first upsetting is H / 2-H / 3. The diameter of the billet after the first drawing is (0.6-0.8)φ. H is the height of the milled aluminum alloy ingot, and φ is the diameter of the milled aluminum alloy ingot. 2) Reheat the billet from step 1) in the furnace and hold it at 460℃-480℃ for 5-10 hours; 3) The billet from step 2) is subjected to secondary upsetting, secondary drawing, and squaring in sequence; the die pressing speed during the upsetting process is 10-15 mm / s, the die pressing speed during the cross drawing process is 10-15 mm / s, the direction of the secondary upsetting is perpendicular to the direction of the secondary drawing, the direction of squaring is perpendicular to the direction of upsetting and parallel to the direction of drawing; and the height of the billet after the secondary upsetting is the same as the height of the billet after the primary upsetting, and the final forging temperature is controlled to be ≥350℃.

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