An aluminum alloy and a method for manufacturing the same

Abstract

The application belongs to the technical field of aluminum alloy, and discloses an aluminum alloy and a preparation method thereof.The aluminum alloy contains Mg with a weight ratio of 3.0-3.4%, Si with a weight ratio of 2.3-2.6%, Cu with a weight ratio of 0.9-1.2%, and further contains Zn with a weight ratio of 2.1-2.4%, Mn with a weight ratio of 0.35-0.50%, Er with a weight ratio of 0.18-0.22%, Zr with a weight ratio of 0.09-0.12%, B with a weight ratio of 0.02-0.04%, and the rest is Al.In the aluminum alloy, Er and Zr precipitate L12 type Al3(Er, Zr) nano dispersed phase, which can hinder grain boundary migration and inhibit dynamic recrystallization, and the recrystallized grains are small, B can remove impurity elements and purify grain boundary defects, harmful impurity defects are few, and Mn can convert coarse needle-like iron-rich brittle phase into short rod and near-spherical α-Al 12 Mn3(Fe, Si) composite dispersed phase.The aluminum alloy has strong resistance to alternating load, long fatigue life, high elongation, and excellent heat resistance under medium-temperature service working conditions.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy technology, and more specifically, to a high elongation aluminum alloy, its preparation method, and its applications. Background Technology

[0002] Most existing aluminum alloys are based on the Al-Si-Cu-Mg system, primarily adding 3.0-3.4% Mg, 2.3-2.6% Si, and 0.9-1.2% Cu by weight, supplemented with trace amounts of rare earth or transition elements. Through smelting and refining, casting, homogenization annealing, hot extrusion, solution treatment, and cooling, aluminum alloys with certain strength and elongation are obtained. These aluminum alloys are widely used in automotive structural components, electrical wires, and electronic device housings. However, existing aluminum alloys have the following disadvantages: (1) Low elongation.

[0003] The recrystallized grains are coarse, with numerous defects at the grain boundaries, harmful impurities, and large, acicular, brittle, iron-rich phase inclusions, resulting in low elongation and poor plasticity.

[0004] (2) Poor heat resistance.

[0005] Aluminum alloys lack a high-temperature stable dispersed pinned phase, so the strengthening phase tends to coarsen rapidly under medium-temperature service conditions, resulting in significant strength loss and insufficient heat resistance.

[0006] As mentioned above, aluminum alloy grain boundaries contain numerous defects and coarse, needle-like brittle iron-rich phase inclusions, which act as stress concentration sources at the phase interface. These stress concentration sources can become rapid crack propagation channels, resulting in weak resistance to alternating loads, short fatigue life, and susceptibility to fatigue failure under medium-temperature service conditions. Summary of the Invention

[0007] This invention provides an aluminum alloy with high elongation and superior heat resistance compared to existing technologies.

[0008] Another object of the present invention is to provide a method for preparing the aluminum alloy.

[0009] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: An aluminum alloy contains 3.0-3.4% Mg, 2.3-2.6% Si, and 0.9-1.2% Cu by weight, as well as 2.1-2.4% Zn, 0.35-0.50% Mn, 0.18-0.22% Er, 0.09-0.12% Zr, and 0.02-0.04% B, with the remainder being Al.

[0010] The aluminum alloy composition of this invention, with the additional addition of 0.18-0.22% Er, 0.09-0.12% Zr, 0.02-0.04% B, and 2.1-2.4% Zn, has the following technical effects: (1) High elongation rate.

[0011] On the one hand, Er and Zr precipitate L12-type Al3(Er,Zr) nano-dispersed phases, which can hinder grain boundary migration, inhibit dynamic recrystallization, and result in fine recrystallized grains. On the other hand, B can remove impurity elements and purify grain boundary defects, resulting in fewer harmful impurity defects. Moreover, Al-B borides, as heterogeneous nucleation cores, refine grains, effectively fix Fe impurities in the matrix, and avoid the formation of a large number of coarse needle-like brittle iron-rich phase inclusions.

[0012] (2) Excellent heat resistance.

[0013] Er and Zr precipitate high-density, thermally stable Al3(Er,Zr) nanoparticles, which effectively pin the matrix structure, inhibit the coarsening of the main reinforcing phase, and stabilize the high-temperature strength; Zn forms fine MgZn2 nanoclusters with the matrix Mg, which further stabilizes the high-temperature strength.

[0014] Botanicals (B) can purify grain boundary defects, while manganese (Mn) can transform coarse, needle-like, iron-rich, brittle phases into short, rod-shaped, nearly spherical α-Al. 12 Mn3(Fe,Si) is a composite dispersed phase. The presence of B and Mn at the phase interface prevents stress concentration sources, thus avoiding stress concentration and rapid crack propagation pathways. Therefore, aluminum alloys exhibit strong resistance to alternating loads and long fatigue life under medium-temperature service conditions, and are less prone to fatigue failure.

[0015] Preferably, the aluminum alloy component further contains 0.05-0.10% Nb and 0.05-0.10% Ta.

[0016] The addition of Nb and Ta to aluminum alloys in this invention also has the effect of refining grain size, specifically: Nb and Ta react with Al to form high-melting-point Al3Nb and Al3Ta dispersed particles, which compensate for the shortcomings of Er and Zr in high-temperature stability. Moreover, Ta and Nb work together to refine the grains and improve the elongation.

[0017] The present invention also provides a method for preparing the aluminum alloy described in any of the above claims, comprising the steps of melting and refining, casting, homogenization annealing, hot extrusion, solution treatment, and cooling treatment. The homogenization annealing is a two-stage annealing, wherein the temperature of the first-stage homogenization annealing is 410~430℃ and the holding time is 6~10h, and the temperature of the second-stage homogenization annealing is 535~545℃ and the holding time is 20~28h. The cooling process employs gradient cryogenic treatment, specifically: the first cryogenic temperature is -196℃, held for 1.5~3 hours, and then allowed to naturally warm to room temperature after removal. Then, a second cryogenic treatment is performed at -85~-75℃, held for 3~6 hours.

[0018] In the method for preparing the aluminum alloy described in this invention, the homogenization annealing is a two-stage annealing, and the cooling treatment employs gradient deep cooling, which has the following technical effects: (1) High elongation. The two-stage homogenization annealing completely eliminates dendritic segregation and solute agglomeration in the ingot, greatly improving the uniformity of the aluminum alloy matrix structure. Moreover, the gradient double deep cooling + multi-stage segmented aging system precisely controls the morphology, size and distribution of precipitated phases, continuously optimizing the plastic structure of the matrix from the process end. The resulting aluminum alloy has a uniform and fine microstructure, free from mixed grains and coarse grain defects. The strengthening phases are fine, dispersed and uniformly distributed, with very few brittle inclusions, resulting in high elongation and excellent plasticity.

[0019] (2) Excellent heat resistance. The two-stage homogenization annealing achieves complete homogenization of the matrix solute, completely eliminating defects such as uneven composition, micro-porosity, and pores; the gradient deep cryogenic + multi-stage aging process can precisely control the precipitation behavior of the strengthening phase, greatly improving the thermal stability and distribution uniformity of the strengthening phase and the high-temperature stable dispersed phase. Moreover, the high-temperature stable dispersed phase can effectively hinder grain boundary migration and coarsening of precipitated phases under high temperature and alternating loads. The strength decay is small and the structural stability is strong under medium temperature conditions. The refined and uniform grains and clean grain boundaries can effectively inhibit crack propagation, significantly improving the aluminum alloy's resistance to alternating loads and fatigue life, and exhibiting excellent heat resistance and fatigue failure resistance.

[0020] Preferably, Er, Zr, Nb, and Ta are added in the form of intermediate alloys during the smelting and refining steps.

[0021] Preferably, the smelting and refining process specifically involves: placing Al ingots into a medium-frequency induction furnace or a resistance furnace, heating the furnace to 690-710°C to melt them, then heating the furnace to 740-760°C, sequentially adding Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys, and finally cooling the furnace to 720-730°C, adding pure Mg, pure Zn, pure Cu, and Al-Mn master alloys, and stirring until completely melted.

[0022] Preferably, the casting step is a semi-continuous casting process, with a pouring temperature of 700~715℃, a primary cooling water pressure of 0.05~0.1MPa, and a secondary cooling water pressure of 0.01~0.05MPa.

[0023] Preferably, the heating temperature of the hot extrusion step is 420~450℃.

[0024] Preferably, the solution treatment temperature is 530~540℃.

[0025] Preferably, the cooling process includes an aging treatment between the first and second deep cryogenic treatments, with a temperature of 155~170℃ and a holding time of 6~10h.

[0026] Preferably, after the cooling treatment, a final stabilization aging treatment is performed at a temperature of 110~130℃ for 10~14h.

[0027] The method for preparing the aluminum alloy of the present invention includes the following steps: Step 1: Melting and Refining: Place Al ingots into a medium-frequency induction furnace or resistance furnace and heat to 690-710℃ to melt. Then heat to 740-760℃ and add Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys sequentially. After each addition, stir electromagnetically for 3-8 minutes to ensure complete dissolution. Then lower the temperature to 720-730℃ and add pure Mg, pure Zn, pure Cu, and Al-Mn master alloys, stirring until completely melted. Finally, add Al-B master alloy or KBF4 (wrapped in aluminum foil and pressed in), and hold for 8-15 minutes. Refine for 15-25 minutes by rotary jetting of Ar or Ar+5%Cl2 at a gas flow rate of 10-25 L / min. After standing for 15-25 minutes, remove slag to obtain molten aluminum alloy. Step 2 Casting: Semi-continuous casting is adopted. The aluminum alloy liquid is poured at a pouring temperature of 700-715℃, the ingot diameter is Φ100~150mm, the casting speed is 80-130 mm / min, the primary cooling is 0.05-0.1MPa, the secondary cooling is 0.01-0.05MPa, and the cooling water temperature is 15~30℃ to obtain the ingot.

[0028] Step 3: Two-stage homogenization annealing: The ingot is placed in a heat treatment furnace for primary and secondary homogenization annealing treatments, specifically as follows: The ingot undergoes primary homogenization annealing at a temperature of 410~430℃ for 6~10 hours; then, it undergoes secondary homogenization annealing at a temperature of 535~545℃ for 20~28 hours; finally, it is furnace cooled to 180~220℃ (furnace cooling rate 10~30℃ / h), removed, and air-cooled to room temperature to obtain the homogenized ingot. The heating rate from primary to secondary homogenization is 30~50℃ / h.

[0029] Step 4 Hot extrusion: The homogenized ingot is heated to 420-450℃ and loaded into an extrusion cylinder (extrusion cylinder temperature is 410~450℃) for forward or reverse extrusion. The outlet is cooled by water mist (water temperature 20-25℃). The extrusion ratio (extrusion coefficient) is 15-25 and the extrusion speed is 2-6 mm / s (depending on the equipment) to obtain the extruded billet.

[0030] Step 5: Solution treatment: Load the extruded billet into a solution furnace. The solution treatment temperature is 530~540℃ (close to but below the overheating temperature), and the solution treatment time is 1~2h (based on a 25mm cross-section, adjusted according to the cross-section thickness). For larger cross-sections, extend the time by 0.3~0.6h for every 10mm increase. After solution treatment, quickly transfer the billet to a room temperature water bath for quenching to obtain a solution-quenched billet. The quenching medium is room temperature water (15~30℃), the quenching transfer time is <15s, and the quenching water temperature is 15~35℃. Step 6: Gradient cryogenics and aging: First deep cryogenic treatment: Place the billet after solution quenching into a liquid nitrogen tank (-196℃) and keep it at that temperature for 1.5~3 hours. After taking it out, allow it to naturally warm to room temperature in the air (about 1-2 hours). Aging treatment: After the first deep cooling, the billet is placed in an aging furnace at 155~170℃ and held for 6~10 hours, then air-cooled to room temperature; Second cryogenic treatment: The aging-treated billet is placed in a cryogenic chamber at a cooling temperature of -85~-75℃, with dry ice and alcohol as the cooling medium. The holding time is 3~6 hours. After being taken out, it is allowed to naturally return to room temperature to obtain aluminum alloy. Step 7 Final stabilization aging: Place the aluminum alloy in an aging furnace, stabilize and age it at a temperature of 110~130℃ for 10~14h, and then air cool it to room temperature to obtain the final aluminum alloy. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments.

[0032] Example 1 An aluminum alloy contains 3.2% Mg, 2.5% Si, 2.2% Zn, 1.1% Cu, 0.4% Mn by weight, with the remainder being Al, and also contains 0.20% Er, 0.10% Zr, 0.03% B, 0.08% Nb, and 0.08% Ta.

[0033] The method for preparing the aluminum alloy includes the following steps: Step 1: Melting and Refining: Place Al ingots into a medium-frequency induction furnace or resistance furnace and heat to 700℃ to melt. Then heat to 750℃ and sequentially add Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys, stirring electromagnetically for 5 minutes after each addition to ensure complete dissolution. Cool to 725℃ and add pure Mg, pure Zn, pure Cu, and Al-Mn master alloys, stirring until completely melted. Finally, add Al-B master alloy or KBF4 (wrapped in aluminum foil and pressed in), and hold for 12 minutes. Refine for 20 minutes by rotary jetting of Ar or Ar + 5% Cl2 at a gas flow rate of 18 L / min. After standing for 20 minutes, remove slag to obtain molten aluminum alloy. Step 2 Casting: Semi-continuous casting is adopted. The aluminum alloy liquid is poured at a pouring temperature of 710℃, the ingot diameter is Φ100~150mm, the casting speed is 100mm / min, the primary cooling is 0.07MPa, the secondary cooling is 0.03MPa, and the cooling water temperature is 23℃ to obtain the ingot.

[0034] Step 3: Two-stage homogenization annealing: The ingot is placed in a heat treatment furnace for primary and secondary homogenization annealing treatments, specifically as follows: The ingot undergoes primary homogenization annealing at a temperature of 420℃ for 8 hours; then, it undergoes secondary homogenization annealing at a temperature of 540℃ for 25 hours; finally, it is cooled in the furnace to 200℃ (furnace cooling rate 20℃ / h), removed, and air-cooled to room temperature to obtain the homogenized ingot. The heating rate from primary to secondary homogenization is 40℃ / h.

[0035] Step 4 Hot extrusion: The homogenized ingot is heated to 440°C and loaded into an extrusion cylinder (extrusion cylinder temperature is 430°C) for forward or reverse extrusion. The outlet is cooled by water mist (water temperature 23°C). The extrusion ratio (extrusion coefficient) is 20, and the extrusion speed is 2-6 mm / s to obtain the extruded billet.

[0036] Step 5: Solution treatment: The extruded billet is placed in a solution furnace at a temperature of 535℃ (close to but below the overheating temperature) for 1-2 hours. After solution treatment, it is quickly transferred to a room temperature water bath for quenching to obtain a solution-quenched billet. The quenching medium is room temperature water (23℃), the quenching transfer time is <15s, and the quenching water temperature is 25℃. Step 6: Gradient cryogenics and aging: First deep cryogenic treatment: The billet after solution quenching is placed in a liquid nitrogen tank (-196℃) and kept at that temperature for 2.5 hours. After being taken out, it is allowed to naturally warm to room temperature in the air (about 1-2 hours). Aging treatment: After the first deep cooling, the billet is placed in an aging furnace at 160℃ and held for 8 hours, then air-cooled to room temperature; Second cryogenic process: The aging-treated billet is placed in a cryogenic chamber at a cooling temperature of -80℃, with dry ice and alcohol as the cooling medium. The holding time is 4 hours. After being taken out, it is allowed to naturally return to room temperature to obtain aluminum alloy. Step 7 Final stabilization aging: Place the aluminum alloy in an aging furnace, stabilize and age it at 120℃ for 12 hours, and then air cool it to room temperature to obtain the final aluminum alloy.

[0037] Example 2 The process is basically the same as in Example 1, except that the aluminum alloy contains 3.0% Mg, 2.3% Si, 2.1% Zn, 0.9% Cu, 0.35% Mn by weight, with the remainder being Al, and also contains 0.18% Er, 0.09% Zr, 0.02% B, 0.05% Nb, and 0.05% Ta.

[0038] Example 3 The process is basically the same as in Example 1, except that the aluminum alloy contains 3.4% Mg, 2.6% Si, 2.4% Zn, 1.2% Cu, 0.50% Mn by weight, with the remainder being Al, and also contains 0.22% Er, 0.12% Zr, 0.04% B, 0.10% Nb, and 0.10% Ta.

[0039] Example 4 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, in step 1 of melting and refining, Al ingots are loaded into a medium-frequency induction furnace or resistance furnace and heated to 690°C to melt. Then, the temperature is raised to 740°C, and Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys are added in sequence. After each addition, the mixture is electromagnetically stirred for 3-8 minutes to ensure complete dissolution, and then the temperature is lowered to 720°C.

[0040] Example 5 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, in step 1 of melting and refining, Al ingots are loaded into a medium-frequency induction furnace or resistance furnace and heated to 710°C to melt. Then, the temperature is raised to 760°C, and Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys are added in sequence. After each addition, the mixture is electromagnetically stirred for 3-8 minutes to ensure complete dissolution, and then the temperature is lowered to 730°C.

[0041] Example 6 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, Er, Zr, Nb, Ta, and B are added in the form of pure Er, pure Zr, pure Nb, pure Ta, and pure B in step 1 of melting and refining.

[0042] Example 7 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, the first-stage homogenization annealing temperature in step 3 is 410℃ and the holding time is 6h; the second-stage homogenization annealing temperature is 535℃ and the holding time is 20h.

[0043] Example 8 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, the first-stage homogenization annealing temperature in step 3 is 430°C and the holding time is 10h; the second-stage homogenization annealing temperature is 545°C and the holding time is 28h.

[0044] Example 9 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, the first deep cryogenic holding time in step 6 of gradient deep cryogenics and aging is 1.5 hours; the aging treatment temperature is 155°C and the holding time is 6 hours; the second deep cryogenic cooling temperature is -85°C and the holding time is 3 hours.

[0045] Example 10 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, the first deep cryogenic holding time in step 6, gradient deep cryogenics and aging, is 3 hours; the aging treatment temperature is 170°C and the holding time is 10 hours; the second deep cryogenic cooling temperature is -75°C and the holding time is 6 hours.

[0046] Example 11 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, after the first cryogenic treatment in step 6 (gradient cryogenic and aging), no aging treatment is performed, and the second cryogenic treatment is performed directly.

[0047] Example 12 The method is basically the same as in Example 1, except that the aluminum alloy preparation method is different. In step 2, the pouring temperature is 700℃, the casting speed is 80 mm / min, the primary cooling is 0.05MPa, the secondary cooling is 0.01MPa, and the cooling water temperature is 15℃. In step 4, during hot extrusion, the homogenized ingot is heated to 420°C, the extrusion cylinder temperature is 410°C, the water mist cooling water temperature is 20-25°C, and the extrusion ratio is 15-25. In step 5, the solution treatment temperature is 530℃. In step 7, the final stabilization aging process involves a stabilization temperature of 110℃ and a stabilization time of 10 hours.

[0048] Example 13 The method is basically the same as in Example 1, except that the aluminum alloy preparation method is different. In step 2, the pouring temperature is 715℃, the casting speed is 130 mm / min, the primary cooling is 0.1MPa, the secondary cooling is 0.05MPa, and the cooling water temperature is 30℃. In step 4, the homogenized ingot is heated to 450°C, the extrusion cylinder temperature is 450°C, the water mist cooling water temperature is 25°C, and the extrusion ratio is 25. In step 5, the solution treatment temperature is 540℃. In step 7, the final stabilization aging process involves a stabilization temperature of 130℃ and a stabilization time of 14 hours.

[0049] Example 14 The method is basically the same as in Example 1, except that step 7 is not included in the aluminum alloy preparation method. The aluminum alloy is obtained directly after gradient deep cooling and aging treatment in step 6.

[0050] Comparative Example 1 It is basically the same as Example 1, except that the aluminum alloy component does not contain Er.

[0051] Comparative Example 2 It is basically the same as Example 1, except that the aluminum alloy composition does not contain Zr.

[0052] Comparative Example 3 It is basically the same as Example 1, except that the aluminum alloy composition does not contain Nb.

[0053] Comparative Example 4 It is basically the same as Example 1, except that the aluminum alloy component does not contain Ta.

[0054] Comparative Example 5 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, step 6, gradient deep cooling and aging, is replaced with conventional cooling treatment. Specifically, the billet after solution quenching is placed in a liquid nitrogen tank (-196°C) and kept at that temperature for 2.5 hours. After being taken out, it is allowed to naturally warm to room temperature in the air.

[0055] Comparative Example 6 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, step 3, the two-stage homogenization annealing, is replaced by conventional single-stage homogenization annealing. Specifically, the ingot is placed in a heat treatment furnace for single-stage homogenization annealing. The single-stage homogenization annealing temperature is 420°C and the holding time is 8 hours. Then, it is cooled to 200°C in the furnace (furnace cooling rate 20°C / h), and then taken out and air-cooled to room temperature to obtain the homogenized ingot.

[0056] Comparative Example 7 The method is basically the same as in Example 1, except that in the aluminum alloy preparation method, step 3, the two-stage homogenization annealing, is replaced by conventional single-stage homogenization annealing. The ingot is placed in a heat treatment furnace for single-stage homogenization annealing, and the temperature of the second-stage homogenization annealing is 540°C, with a holding time of 25 hours. Then, it is cooled to 200°C in the furnace (furnace cooling rate 20°C / hour), and then taken out and air-cooled to room temperature to obtain the homogenized ingot.

[0057] Performance testing: 1. Elongation The elongation of the aluminum alloys obtained in Examples 1-14 and Comparative Examples 1-7 was tested according to GB / T 228.1-2021 Metallic Materials - Tensile Testing, as follows: (1) Sample preparation Sampling location: For all Examples 1-14 and Comparative Examples 1-7, tensile specimens were cut along the middle of the extrusion longitudinal direction of the finished aluminum alloy profiles, avoiding areas with surface peeling, cracks, segregation, and coarse grains; 3 standard specimens were prepared in parallel for each component.

[0058] Specimen specifications: Rectangular cross-section specimens are used, with an original gauge length L0=50mm, a parallel section width of 12.5mm, a thickness of 6mm, and a total length of 200mm; if the profile thickness is insufficient, it is uniformly processed into a 3mm thick thin plate tensile specimen with a gauge length L0=50mm.

[0059] Processing requirements: Milling, round the edges of the sample with a radius of 0.5mm, and remove tool marks and burrs; after processing, use 400# and 800# sandpaper to grind the surface of the parallel section in stages to eliminate processing stress.

[0060] Marking the gauge length: Use a dot-type gauge length meter to mark the original gauge length of 50 mm on the parallel section of the sample. The depth of the dots should not exceed 5% of the sample thickness to avoid premature breakage.

[0061] (2) Test equipment and environment Equipment: Universal electronic tensile testing machine, force accuracy grade 0.5, extensometer gauge length 50mm, measuring range 0~10mm; Environment: Room temperature 23±2℃, relative humidity 40%~60%; Loading rate: 2 mm / min for the tensile rate during the plastic deformation stage of the parallel section, with uniform static load tensile throughout the entire process.

[0062] (3) Testing operation procedure Clamping the specimen: Clamp both ends of the specimen in the upper and lower clamps of the testing machine, ensuring that the specimen axis coincides with the loading center line, without tilting or eccentricity; after clamping, install the extensometer and clamp it in the 50mm original gauge length section.

[0063] Zeroing calibration: The load, displacement, and extensibility count values ​​of the testing machine are all reset to zero, and the data acquisition program is started.

[0064] Tensile loading: Apply the load at a constant speed until the specimen breaks, and record the load-displacement curve and the gauge length after fracture.

[0065] Post-fracture measurement: Remove the fractured specimen, precisely align the two fracture surfaces, and measure the gauge length L after fracture using a vernier caliper with an accuracy of 0.01 mm. u .

[0066] Parallel test: Repeat the above operation for each group of 3 specimens, and discard invalid data with fracture location outside the gauge length or eccentric fracture.

[0067] (4) Method for calculating elongation Formula for calculating elongation at fracture (elongation A, in %): A=[(L u -L0) / L0]×100% L0: Original gauge length 50mm; L u : Gauge length after fracture; The arithmetic mean of 3 valid specimens in each group is taken as the final elongation of the specimen.

[0068] (5) Test judgment rules Valid data is obtained when the specimen breaks in the middle third of the gauge length. Samples that break at the clamping end, at the gauge mark, or have obvious machining defects are discarded and retested. If the range of 3 data points in the same group is greater than 1.5%, 2 more samples should be added for retesting.

[0069] The elongation test results of the aluminum alloys obtained in Examples 1-14 and Comparative Examples 1-7 are shown in Table 1.

[0070] 2. Heat resistance According to GB / T 2039-2012 "Metallic Materials - Uniaxial Tensile Creep and Indestructibility Test Method", the creep rupture time at 200℃ is used as the core evaluation index (the typical medium-temperature service temperature of this aluminum alloy is 200℃, and the load is uniformly set at 180MPa. The longer the creep rupture time, the better the heat resistance, fatigue resistance, and high-temperature strength retention ability; unit: h). Simultaneously, a 200℃ high-temperature tensile strength test is used as supplementary evidence. The specific testing method is as follows: (1) Sample preparation Sampling: Samples were taken from the longitudinal center of the extruded profiles of all examples and comparative examples, avoiding surface defects and coarse grain areas, with 3 parallel durable test specimens per group.

[0071] Specimen specifications: Standard circular endurance tensile specimen, parallel section diameter d=6mm, original gauge length L0=30mm, total length 180mm; threaded sections at both ends, free of burrs, cracks, and machining marks.

[0072] Pretreatment: Grind the parallel sections step by step with 400#~1000# sandpaper to eliminate residual stress from processing; ultrasonically clean with alcohol and dry for later use.

[0073] (2) Test equipment and test conditions Equipment: High-temperature creep testing machine, three-section temperature-controlled tubular heating furnace with an accuracy of ±1℃; high-temperature extensometer and load sensor (0.5 grade).

[0074] Test temperature: constant 200℃ (medium-temperature heat resistance test temperature for this alloy); Test load: Static tensile load 180 MPa; Environment: Air atmosphere, no corrosive media.

[0075] (3) Complete testing operation steps Sample loading: Install the long-term specimen on the upper and lower pull rods of the testing machine, center and calibrate it to ensure that there is no eccentricity or tilt, and tighten the threads; clamp the high-temperature extensometer into the 30mm gauge length section of the specimen.

[0076] Heating and holding: Seal the heating furnace and heat to 200℃ at a rate of 5℃ / min, then hold at a constant temperature for 60min to ensure that the overall temperature of the sample is uniform and stable.

[0077] Apply load: Slowly and uniformly apply load to the target stress of 180 MPa, with a loading time of ≤3 min. Start timing after the load stabilizes.

[0078] Continuous testing: The temperature was kept constant at 200℃ and the load constant at 180MPa throughout the test. The deformation and crack initiation time of the specimen were recorded in real time until the specimen completely fractured.

[0079] Record data: Record the total time from the completion of loading to fracture, which is the 200℃ / 180MPa sustained fracture time; simultaneously collect the high-temperature tensile strength at the moment of fracture.

[0080] Parallel retesting: Three samples were tested in each group. Invalid data such as eccentric fracture and abnormal furnace temperature fluctuations were removed, and the average value of the valid samples was taken as the final heat resistance performance index.

[0081] Supplementary judgment rules: If the sample does not break after 100 hours, terminate the test and record the duration as >100 hours. If the range of 3 data points in the same group is greater than 8 hours, 2 additional samples should be tested again.

[0082] (4) Auxiliary heat resistance index: 200℃ high temperature tensile strength test procedure Tensile specimens of the same specification were heated to 200℃ in a high-temperature furnace and held for 30 minutes. Tension rate 1 mm / min, stretch until fracture, and read the high temperature tensile strength (MPa). The average value of 3 samples in each group is taken, and the heat resistance is evaluated in combination with the duration of heat exposure.

[0083] The heat resistance test results of the aluminum alloys obtained in Examples 1-14 and Comparative Examples 1-7 are shown in Table 1.

[0084] Table 1. Elongation and heat resistance of aluminum alloys obtained in Examples 1-14 and Comparative Examples 1-7

[0085] The above description is merely an embodiment of the present invention and does not limit the scope of patent protection. Any non-substantial changes or substitutions made by those skilled in the art based on the present invention will still fall within the scope of patent protection.

Claims

1. An aluminum alloy containing 3.0-3.4% Mg, 2.3-2.6% Si, and 0.9-1.2% Cu by weight, characterized in that, It also contains 2.1-2.4% Zn, 0.35-0.50% Mn, 0.18-0.22% Er, 0.09-0.12% Zr, 0.02-0.04% B, and the remainder is Al.

2. The aluminum alloy according to claim 1, characterized in that, It also contains 0.05-0.10% Nb and 0.05-0.10% Ta.

3. The method for preparing the aluminum alloy according to any one of claims 1 to 2, comprising the steps of smelting and refining, casting, homogenizing annealing, hot extrusion, solution treatment, and cooling treatment, characterized in that: The homogenization annealing is a two-stage annealing, wherein the temperature of the first-stage homogenization annealing is 410~430℃ and the holding time is 6~10h, and the temperature of the second-stage homogenization annealing is 535~545℃ and the holding time is 20~28h. The cooling process employs a gradient cryogenic treatment, specifically: the first cryogenic temperature is -196℃, held for 1.5~3 hours, and then allowed to naturally warm to room temperature after removal. Then, a second cryogenic treatment is performed at -85~-75℃, held for 3~6 hours.

4. The method for preparing the aluminum alloy according to claim 3, characterized in that, Er, Zr, Nb, and Ta are added in the form of intermediate alloys during the smelting and refining steps.

5. The method for preparing the aluminum alloy according to claim 4, characterized in that, The smelting and refining process specifically involves: placing Al ingots into a medium-frequency induction furnace or resistance furnace, heating them to 690~710℃ to melt them, then heating them to 740~760℃, adding Al-Er, Al-Zr, Al-Nb, and Al-Ta master alloys in sequence, and finally cooling them to 720~730℃, adding pure Mg, pure Zn, pure Cu, and Al-Mn master alloys, and stirring until completely melted.

6. The method for preparing the aluminum alloy according to claim 3, characterized in that, The casting process employs semi-continuous casting, with a pouring temperature of 700~715℃, a primary cooling water pressure of 0.05~0.1MPa, and a secondary cooling water pressure of 0.01~0.05MPa.

7. The method for preparing the aluminum alloy according to claim 3, characterized in that, The heating temperature for the hot extrusion step is 420~450℃.

8. The method for preparing the aluminum alloy according to claim 3, characterized in that, The solution treatment temperature is 530~540℃.

9. The method for preparing the aluminum alloy according to claim 3, characterized in that, The cooling process includes an aging treatment between the first and second deep cryogenic treatments, with a temperature of 155~170℃ and a holding time of 6~10h.

10. The method for preparing the aluminum alloy according to claim 3, characterized in that, After the cooling treatment, a final stabilization and aging treatment is performed at a temperature of 110~130℃ for 10~14h.

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