High-strength and high-conductivity 7050 aluminum alloy and short-process preparation process thereof

Abstract

The invention belongs to the technical field of wrought aluminum alloy material processing, and relates to a high-strength high-conductivity 7050 aluminum alloy and a short-process preparation process thereof.The process comprises the steps that pure metal aluminum, pure metal zinc, pure metal magnesium, pure metal copper and pure aluminum-zirconium intermediate alloy serve as raw materials, 6.1-6.3 wt.% of Zn, 2.3-2.5 wt.% of Mg, 2.4-2.6 wt.% of Cu and 0.12-0.14 wt.% of Zr are matched, smelting, melt refining and refining treatment are carried out, and then the high-strength high-conductivity 7050 aluminum alloy is obtained; sub-rapid solidification of a melt is realized by adopting water-cooling copper mold casting, as-cast grains are remarkably refined, and formation of a coarse second phase is inhibited; traditional multi-stage annealing is replaced with single-stage homogenizing annealing, so that the residual phase area percentage is smaller than or equal to 1.0%, and the maximum residual phase size lt is achieved; 30 [mu] m; and by combining multi-pass hot rolling and solid solution-aging cooperative regulation and control, the problem of intensity-conductivity inversion caused by second phase distribution and grain boundary segregation is solved. Compared with a traditional process, the homogenization time is shortened by 50% or above, the total technological process is reduced by 30%-40%, and finally the high-performance 7050 aluminum alloy with the tensile strength larger than or equal to 650 MPa and the electric conductivity larger than or equal to 40% IACS is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of deformed aluminum alloy material processing, and relates to a high-strength and high-conductivity 7050 aluminum alloy and a short-process preparation process thereof. Background Art

[0002] As a representative of the Al-Zn-Mg-Cu alloy family, 7050 aluminum alloy demonstrates broad application prospects in aerospace and rail transportation due to its outstanding advantages, including high strength, low density, excellent toughness, and fatigue resistance. In aerospace, improving aircraft performance and controlling weight are crucial. 7050 aluminum alloy can be used to manufacture key components such as wings and fuselages. Its low density significantly reduces aircraft weight, thereby improving flight performance, such as increasing range and reducing fuel consumption. This has positive implications for the economic and environmental performance of air transportation. In rail transportation, as trains evolve towards lighter weight and higher performance, 7050 aluminum alloy also plays a significant role. It can be used to manufacture suspension connectors and body structural components, reducing weight while maintaining structural strength. This helps increase train speeds, reduce energy consumption, and enhance overall rail transportation efficiency.

[0003] However, the traditional preparation process of 7050 aluminum alloy has a series of bottleneck problems that need to be solved urgently.

[0004] First, there is the prominent problem of coarsening of the solidification structure. During conventional casting, due to the slow cooling rate, the interdendritic eutectic phase is large. During the subsequent plastic deformation, these coarse eutectic phases are difficult to completely break up, thus affecting the mechanical properties and processing performance of the alloy.

[0005] Second, homogenization annealing is inefficient. To eliminate coarse secondary phases in the as-cast state, such as η-MgZn2 and S-Al2CuMg, conventional processes require lengthy, multi-stage homogenization annealing. This not only significantly increases energy consumption but also prolongs production cycles, severely limiting production efficiency and cost control.

[0006] Third, there's an inverse relationship between strength and conductivity. While high Zn / Mg contents effectively improve the alloy's strength, they exacerbate grain boundary segregation and the presence of residual phases, leading to significant electron scattering, making it difficult for the alloy's conductivity to exceed 35% IACS. While existing technologies attempt to improve conductivity by adding rare earth elements, this significantly increases smelting costs.

[0007] In summary, the development of a short-process, low-cost preparation process that can synergistically improve the strength and conductivity of 7050 aluminum alloy has important practical significance and broad market prospects for promoting the widespread application of 7050 aluminum alloy in fields such as aerospace and rail transportation. Summary of the Invention

[0008] In view of this, the purpose of the present invention is to provide a high-strength and high-conductivity 7050 aluminum alloy and a short-process preparation process thereof. By optimizing the alloy composition design, sub-rapid solidification control and single-stage homogenization heat treatment, the homogenization time is significantly shortened to less than 4 hours. At the same time, the second phase morphology and distribution are synergistically regulated to break through the strength-conductivity inversion bottleneck, and ultimately obtain a high-performance aluminum alloy with a tensile strength ≥650MPa and a conductivity ≥40% IACS, providing a low-cost, short-cycle material solution for high-load conductive components for aerospace and rail transportation.

[0009] In order to achieve the above object, the present invention provides the following technical solutions:

[0010] A short-process preparation process for a high-strength and high-conductivity 7050 aluminum alloy comprises the following steps:

[0011] Raw material ratio: Pure aluminum, pure zinc, pure magnesium, pure copper and aluminum-zirconium master alloy as raw materials, and calculated by weight percentage: Zn: 6.1-6.3wt.%, Mg: 2.3-2.5wt.%, Cu: 2.4-2.6wt.%, Zr: 0.12-0.14wt.%, the balance being Al and unavoidable impurities, with the total impurity content not exceeding 0.15wt.%;

[0012] Alloy smelting: Place pure aluminum and aluminum-zirconium master alloy in a resistance smelting furnace and heat to 720-740°C for primary smelting. After they are completely melted, add pure copper and pure zinc in sequence, and control the melt temperature to no more than 760°C. Remove the surface oxide slag for 5 minutes.

[0013] When the temperature drops to 735-745°C, pure magnesium metal is added by the graphite bell jar pressure method with a pressure depth of not less than 200 mm. After the pure magnesium metal is melted, electromagnetic stirring is used for 10 minutes to achieve pre-homogenization of the composition. After stirring, the temperature is lowered to the refining temperature range at a rate of 2-3°C / min.

[0014] Melt refining and refinement treatment: including graded degassing refining, static slag removal and grain refinement in sequence;

[0015] Water-cooled copper mold casting: The melt that has undergone melt refining and refinement treatment is poured into a water-cooled copper mold to obtain a 7050 aluminum alloy ingot;

[0016] Homogenization annealing: Single-stage homogenization annealing, heating stage: heating to 470℃ at 5℃ / min, keeping at this temperature for 4h, then air cooling to room temperature, and controlling the area percentage of residual phase in the as-cast structure to be below 1.0%, and the maximum residual phase size to be less than 30μm;

[0017] Hot rolling deformation: The 7050 aluminum alloy ingot after homogenization annealing is subjected to hot rolling plastic deformation at a rolling temperature of 430±5°C and a total deformation of 70% to obtain a 7050 aluminum alloy rolled piece;

[0018] Solution-aging treatment: The 7050 aluminum alloy rolled piece is kept at 470°C for 1 hour for solution treatment, and then kept at 120°C for 24 hours for aging treatment to obtain a 7050 aluminum alloy piece.

[0019] The "short process" is defined as: the homogenization annealing holding time is shortened to 4 hours, which is more than 50% less than the traditional annealing process (≥8 hours); the pre-rolling annealing step in the traditional process is omitted; the homogenization annealing is directly connected with the hot rolling process, and the total process time is shortened by more than 30%.

[0020] Furthermore, the purity of the pure metal aluminum, pure metal zinc, pure metal magnesium and pure metal copper is 99.9%, the Zr content in the aluminum-zirconium master alloy is 10 wt.%, and the balance is Al.

[0021] Furthermore, the frequency of the electromagnetic stirring is 20 Hz and the current is 100 A.

[0022] Furthermore, the graded degassing refining includes:

[0023] Stage 1: When the melt temperature drops to 730°C, 0.3 wt.% of refining agent is added to the melt by the graphite bell pressure method. After no obvious bubbles appear on the melt surface, the graphite bell is removed and the melt is connected to the argon injection system for 5 minutes.

[0024] The second stage: 0.3wt.% refining agent was added by the graphite bell press method. After no obvious bubbles were found on the melt surface, the graphite bell was removed and then ultrasonic-assisted treatment was performed for 5 minutes.

[0025] Furthermore, the refining agent is hexachloroethane; the purity of the argon in the argon blowing system is ≥99.99%, and the flow rate is 1.5 L / min; the frequency of the ultrasonic-assisted treatment is 15-20 kHz, and the power is 200 W.

[0026] Furthermore, the static slagging is:

[0027] After refining, let it stand at 730℃ for 20 minutes to allow inclusions to float fully and completely remove the slag on the surface of the melt;

[0028] The grain refinement is:

[0029] A titanium alloy bell jar preheated to 400°C was used to press-in 0.05wt.% of grain refiner, and the melt temperature was controlled to be no higher than 730°C and kept warm for 10 minutes.

[0030] The grain refiner is an Al-3Ti-B master alloy, the composition of which is: Ti: 3.0wt.%, B: 1.0wt.%, and the balance is Al.

[0031] Furthermore, the cooling water temperature of the water-cooled copper mold is not higher than 5° C., and the solidification cooling rate of the melt is controlled to be 25-30° C. / s.

[0032] Furthermore, the area percentage of the residual phase of the as-cast structure is sampled and detected in at least 3 different viewing fields using a metallographic microscope, and the average value is ≤1.0%.

[0033] Furthermore, in the hot rolling deformation, the rolling is carried out in 7 passes, and the reduction rate of each pass is 15%.

[0034] A high-strength and high-conductivity 7050 aluminum alloy is prepared by the above-mentioned preparation process. The composition of the 7050 aluminum alloy includes, by weight percentage, 6.1-6.3 wt.% of Zn, 2.3-2.5 wt.% of Mg, 2.4-2.6 wt.% of Cu, and 0.12-0.14 wt.% of Zr. The remainder is Al and unavoidable impurities, and the total amount of impurities is not higher than 0.15 wt.%.

[0035] The beneficial effects of the present invention are:

[0036] 1. Shorten the process and make it more efficient

[0037] This technical solution significantly improves production efficiency and achieves short process and high efficiency by optimizing the preparation process of 7050 aluminum alloy. In the casting stage, water-cooled copper mold casting technology is adopted to make the melt solidification cooling rate reach sub-rapid solidification (25-30℃ / s), far exceeding the 5-10℃ / s of the traditional process. This high cooling rate effectively refines the cast grains and reduces the formation of coarse phases, providing a high-quality foundation for subsequent processes. In addition, the homogenization annealing adopts a single-stage process and only needs to be kept at 470℃ for 4 hours, which is more than 50% shorter than the traditional multi-stage annealing (total time ≥8 hours). The overall process time is reduced by 30% to 40%, which greatly improves production efficiency and provides a faster and more economical solution for industrial applications.

[0038] 2. Synergistic performance improvement

[0039] This solution significantly improves the overall performance of 7050 aluminum alloy while shortening the process, achieving synergistic optimization of strength and electrical conductivity. First, the sub-rapid solidification of water-cooled copper mold casting refines the as-cast grains and inhibits the formation of coarse second phases, reducing micro defects. Second, single-stage homogenization annealing precisely controls the residual phase (area percentage ≤1.0%, size <30μm), optimizing the microstructure. Finally, the synergistic effect of hot rolling and solution-aging treatment further improves the performance. The alloy's tensile strength reaches ≥650MPa, an increase of approximately 8% over the 603MPa of the traditional process. The electrical conductivity reaches ≥40% IACS, which is better than the 35% IACS of the traditional process. This balance of strength and conductivity breaks through the limitations of traditional processes and meets the needs of high-performance applications.

[0040] 3. Cost controllable

[0041] This technical solution not only improves efficiency and performance, but also strictly controls production costs, and has significant economic advantages. Conventional pure metal raw materials (such as pure aluminum, zinc, magnesium, and copper) and aluminum-zirconium intermediate alloys are selected during the preparation process to avoid the use of expensive rare earth elements, effectively reducing raw material costs. In addition, the short process design reduces energy consumption and equipment occupancy time, further reducing production expenses. Compared with traditional processes, this solution not only has better performance, but also has cost controllability, providing cost-effective material options for aerospace, rail transportation and other fields, showing broad application potential.

[0042] Other advantages, objects, and features of the present invention will be described in part in the following description and, in part, will be apparent to those skilled in the art upon examination of the following description or may be learned from practice of the present invention. The objects and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below with reference to the accompanying drawings, in which:

[0044] Figure 1 A flow chart of a short-process preparation process for a high-strength and high-conductivity 7050 aluminum alloy provided by the present invention;

[0045] Figure 2 This is a microstructure diagram of the 7050 aluminum alloy ingot prepared in Comparative Example 1;

[0046] Figure 3 This is the microstructure diagram of the 7050 aluminum alloy ingot prepared in Comparative Example 1 after homogenization annealing;

[0047] Figure 4This is a microstructure diagram of the high-strength and high-conductivity 7050 aluminum alloy ingot prepared in Example 2;

[0048] Figure 5 This is the microstructure diagram of the high-strength and high-conductivity 7050 aluminum alloy ingot prepared in Example 2 after homogenization annealing. DETAILED DESCRIPTION

[0049] The following describes the embodiments of the present invention by means of specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments are only schematic illustrations of the basic concept of the present invention, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0050] Among them, the accompanying drawings are only for illustrative purposes and represent only schematic diagrams rather than actual pictures, and should not be understood as limiting the present invention. In order to better illustrate the embodiments of the present invention, some parts of the accompanying drawings may be omitted, enlarged or reduced, and do not represent the dimensions of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions may be omitted in the accompanying drawings.

[0051] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if there are terms such as "upper", "lower", "left", "right", "front", "back", etc. indicating directions or positional relationships, they are based on the directions or positional relationships shown in the drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operate in a specific direction. Therefore, the terms describing the positional relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0052] See also Figure 1 The present invention provides a short-process process for preparing a high-strength, high-conductivity 7050 aluminum alloy. To clarify the objectives, technical solutions, and effects of the present invention, the following is a detailed description with reference to comparative examples and examples. It should be understood that the specific examples described herein are intended only to illustrate the present invention and are not intended to limit its scope.

[0053] Comparative Example 1: Traditional process

[0054] (1) Raw material ratio:

[0055] Pure aluminum, zinc, magnesium, copper and aluminum-zirconium master alloy are used as raw materials, and the raw material components are proportioned. In terms of weight percentage, the raw material components include: Zn: 6.2wt.%, Mg: 2.4wt.%, Cu: 2.5wt.%, Zr: 0.13wt.%, and the balance is Al and unavoidable impurities (the total amount of impurities is not higher than 0.15wt.%).

[0056] (2) Alloy smelting:

[0057] Pure aluminum and Al-10Zr master alloy are placed in a resistance melting furnace and heated to 740°C for primary melting. After they are completely melted, pure copper and pure zinc are added in sequence, and the melt temperature is controlled not to be higher than 760°C. After 5 minutes, the surface oxide slag is scraped off. When the melt is cooled to 740°C, pure magnesium is added by the graphite bell pressing method with a pressing depth of 200mm. After the pure magnesium is melted, mechanical stirring is used for 10 minutes. After stirring, the temperature is lowered to 730°C at a rate of 2°C / min.

[0058] (3) Melt refining and refinement:

[0059] Degassing refining: When the melt temperature drops to 730°C, 0.6 wt.% of hexachloroethane (C2Cl6) is added at one time through a graphite bell jar. After no obvious bubbles appear on the melt surface, the graphite bell jar is removed and an argon injection system (Ar purity ≥ 99.99%, flow rate 1.5 L / min) is connected for 10 minutes.

[0060] Standing slag removal: After refining, stand at 730℃ for 20 minutes to completely remove the slag on the surface of the melt;

[0061] Grain refinement: A titanium alloy bell jar preheated to 400°C was pressed into 0.05wt.% of Al-3Ti-B master alloy, the melt temperature was controlled not to exceed 730°C, and the temperature was kept for 10 minutes.

[0062] (4) Ordinary steel mold casting:

[0063] The melt is poured into a common steel mold, and the melt solidifies at a cooling rate of 5 to 10°C / s to obtain a 7050 aluminum alloy ingot.

[0064] (5) Homogenization annealing:

[0065] The ingot was subjected to two-stage homogenization annealing. In the first stage, the temperature was increased to 400°C at 2°C / min and kept at this temperature for 2 h. In the second stage, the temperature was increased to 470°C at 5°C / min and kept at this temperature for 8 h, and then air-cooled to room temperature.

[0066] (6) Pre-rolling annealing:

[0067] The ingot after homogenization annealing was heated to 400°C at a rate of 3°C / min and kept at this temperature for 2 h, and then air-cooled to room temperature.

[0068] (7) Hot rolling deformation:

[0069] The ingot after pre-rolling annealing is subjected to hot rolling plastic deformation at a rolling temperature of 430±5°C in 12 passes, with a single pass reduction of 10% and a total deformation of 70%.

[0070] (7) Solution-aging treatment:

[0071] The rolled pieces were subjected to solution treatment (keeping at 470°C for 1 hour) and aging treatment (keeping at 120°C for 24 hours).

[0072] The above steps were used to process 7050 aluminum alloy parts using traditional technology. The residual phase area percentage in the as-cast structure after homogenization annealing was 1.71%, the maximum residual phase size was 58 μm, the strength after aging treatment was 603 MPa, the conductivity was 35% IACS, and the total process time was 52 h.

[0073] Example 1: A short-process preparation process for a high-strength and high-conductivity 7050 aluminum alloy provided by this application

[0074] (1) Raw material ratio:

[0075] Pure aluminum, zinc, magnesium, copper and aluminum-zirconium master alloy are used as raw materials, and the raw material components are proportioned. In terms of weight percentage, the raw material components include: Zn: 6.1wt.%, Mg: 2.5wt.%, Cu: 2.6wt.%, Zr: 0.12wt.%, and the balance is Al and unavoidable impurities (the total amount of impurities is not higher than 0.15wt.%).

[0076] (2) Alloy smelting:

[0077] Pure aluminum and Al-10Zr master alloy are placed in a resistance melting furnace and heated to 740°C for primary melting. After they are completely melted, pure copper and pure zinc are added in sequence, and the melt temperature is controlled not to be higher than 760°C. After 5 minutes, the surface oxide slag is scraped off. When the melt is cooled to 740°C, pure magnesium is added by the graphite bell jar pressing method with a pressing depth of 210mm. After the pure magnesium is melted, electromagnetic stirring is used for 10 minutes with an electromagnetic stirring frequency of 20Hz and a current of 100A. After stirring, the temperature is lowered to 730°C at a rate of 2°C / min.

[0078] (3) Melt refining and refinement:

[0079] Grading degassing refining:

[0080] Stage 1: When the melt temperature drops to 730°C, 0.3 wt% hexachloroethane is added through a graphite bell jar. After no obvious bubbles appear on the melt surface, the graphite bell jar is removed and connected to an argon injection system for a continuous treatment of 5 minutes.

[0081] The second stage: preliminary slag removal, adding 0.3wt.% hexachloroethane, and after no obvious bubbles on the melt surface, taking out the graphite bell jar and using ultrasonic assisted treatment for 5 minutes, the ultrasonic assisted treatment frequency is 15kHz and the power is 200W;

[0082] Standing slag removal: After refining, stand at 730℃ for 20 minutes to completely remove the slag on the surface of the melt;

[0083] Grain refinement: A titanium alloy bell jar preheated to 400°C was used to press-in 0.05 wt.% of grain refiner, the melt temperature was controlled not to exceed 730°C, and the temperature was kept for 10 minutes.

[0084] (4) Water-cooled copper mold casting:

[0085] The melt was poured into a water-cooled copper mold with a cooling water temperature of 5°C and a melt solidification cooling rate of 28°C / s to obtain a 7050 aluminum alloy ingot.

[0086] (5) Homogenization annealing:

[0087] The ingot was subjected to single-stage homogenization annealing, heating to 470°C at 5°C / min and holding for 4 h, and then air-cooled to room temperature.

[0088] (6) Hot rolling deformation:

[0089] The ingot after homogenization annealing is subjected to hot rolling plastic deformation at a rolling temperature of 430±5°C in 7 passes, with a single pass reduction of 15% and a total deformation of 70%.

[0090] (7) Solution-aging treatment:

[0091] The rolled pieces were subjected to solution treatment (keeping at 470°C for 1 hour) and aging treatment (keeping at 120°C for 24 hours).

[0092] The above steps realize the processing of 7050 aluminum alloy parts using the patented process. After homogenization annealing, the residual phase area percentage in the cast structure is 0.91%, the maximum residual phase size is 30μm, the strength after aging treatment is 653MPa, the conductivity is 42%IACS, and the total process time is 36h.

[0093] Example 2: Optimized short-process preparation process for high-strength and high-conductivity 7050 aluminum alloy

[0094] (1) Raw material ratio:

[0095] Pure aluminum, pure zinc, pure magnesium, pure copper and aluminum-zirconium master alloy are used as raw materials, and the raw material components are proportioned. In terms of weight percentage, the raw material components include: Zn: 6.3wt.%, Mg: 2.3wt.%, Cu: 2.4wt.%, Zr: 0.14wt.%, and the balance is Al and unavoidable impurities (the total amount of impurities is not higher than 0.15wt.%).

[0096] (2) Alloy smelting:

[0097] Pure aluminum and Al-10Zr master alloy are placed in a resistance melting furnace and heated to 740°C for primary melting. After they are completely melted, pure copper and pure zinc are added in sequence, and the melt temperature is controlled not to be higher than 760°C. After 5 minutes, the surface oxide slag is scraped off. When the melt is cooled to 740°C, pure magnesium is added by the graphite bell jar pressing method with a pressing depth of 210mm. After the pure magnesium is melted, electromagnetic stirring is used for 10 minutes with an electromagnetic stirring frequency of 20Hz and a current of 100A. After stirring, the temperature is lowered to 730°C at a rate of 3°C / min.

[0098] (3) Melt refining and refinement:

[0099] Grading degassing refining:

[0100] Stage 1: When the melt temperature drops to 730°C, 0.3 wt% hexachloroethane is added through a graphite bell jar. After no obvious bubbles appear on the melt surface, the graphite bell jar is removed and connected to an argon injection system for a continuous treatment of 5 minutes.

[0101] The second stage: preliminary slag removal, adding 0.3wt.% hexachloroethane, and after no obvious bubbles on the melt surface, taking out the graphite bell jar and using ultrasonic assisted treatment for 5 minutes, the ultrasonic assisted treatment frequency is 20kHz and the power is 200W;

[0102] Standing slag removal: After refining, stand at 730℃ for 20 minutes to completely remove the slag on the surface of the melt;

[0103] Grain refinement: A titanium alloy bell jar preheated to 400°C was used to press-in 0.05 wt.% of grain refiner, the melt temperature was controlled not to exceed 730°C, and the temperature was kept for 10 minutes.

[0104] (4) Water-cooled copper mold casting:

[0105] The melt was poured into a water-cooled copper mold with a cooling water temperature of 3°C and a melt solidification cooling rate of 30°C / s to obtain a 7050 aluminum alloy ingot.

[0106] (5) Homogenization annealing:

[0107] The ingot was subjected to single-stage homogenization annealing, heating to 470°C at 5°C / min and holding for 4 h, and then air-cooled to room temperature.

[0108] (6) Hot rolling deformation:

[0109] The ingot after homogenization annealing is subjected to hot rolling plastic deformation at a rolling temperature of 430±5°C in 7 passes, with a single pass reduction of 15% and a total deformation of 70%.

[0110] (7) Solution-aging treatment:

[0111] The rolled pieces were subjected to solution treatment (keeping at 470°C for 1 hour) and aging treatment (keeping at 120°C for 24 hours).

[0112] The above steps realize the processing of 7050 aluminum alloy parts using the patented process. After homogenization annealing, the residual phase area percentage in the cast structure is 0.73%, the maximum residual phase size is 25μm, the strength after aging treatment is 662MPa, the conductivity is 43%IACS, and the total process time is 36h.

[0113] See also Figures 2 to 5 , are microstructure diagrams of the 7050 aluminum alloy ingots prepared in Comparative Example 1 and Example 2, and microstructure diagrams of the 7050 aluminum alloy ingots after homogenization annealing, respectively;

[0114] pass Figure 4 and Figure 2 By comparison, it can be seen intuitively that the alloy grains and the second phase of Example 2 are finer and more uniform, and the structure is denser;

[0115] pass Figure 5 and Figure 3 From the comparison, it can be seen intuitively that the alloy of Example 2 has less residual phase and smaller size after homogenization annealing.

[0116] Table 1 Homogenization effect, aging performance and total process time of 7050 aluminum alloy prepared in comparative examples and examples

[0117]

[0118] Table 1 clearly shows the advantages of the short-process preparation process for high-strength and high-conductivity 7050 aluminum alloy provided by the present invention in improving alloy performance and shortening the preparation cycle. The total process time is shortened by 16 hours, and the tensile strength and conductivity are also significantly improved.

[0119] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions, which should all be included in the scope of the claims of the present invention.

Claims

1. A short-process preparation process for high-strength and high-conductivity 7050 aluminum alloy, characterized in that: The following steps are involved: Raw material ratio: Pure aluminum, pure zinc, pure magnesium, pure copper and aluminum-zirconium master alloy as raw materials, and calculated by weight percentage: Zn: 6.1-6.3wt.%, Mg: 2.3-2.5wt.%, Cu: 2.4-2.6wt.%, Zr: 0.12-0.14wt.%, the balance being Al and unavoidable impurities, with the total impurity content not exceeding 0.15wt.%; Alloy smelting: Place pure aluminum and aluminum-zirconium master alloy in a resistance smelting furnace and heat to 720-740°C for primary smelting. After they are completely melted, add pure copper and pure zinc in sequence, and control the melt temperature to no more than 760°C. Remove the surface oxide slag for 5 minutes. When the temperature drops to 735-745°C, pure magnesium metal is added by the graphite bell jar pressure method with a pressure depth of not less than 200 mm. After the pure magnesium metal is melted, electromagnetic stirring is used for 10 minutes to achieve pre-homogenization of the composition. After stirring, the temperature is lowered to the refining temperature range at a rate of 2-3°C / min. Melt refining and refinement treatment: including graded degassing refining, static slag removal and grain refinement in sequence; Water-cooled copper mold casting: The melt that has undergone melt refining and refinement treatment is poured into a water-cooled copper mold to obtain a 7050 aluminum alloy ingot; Homogenization annealing: Single-stage homogenization annealing, heating stage 5 ° C / min to 470 ° C, and keep warm for 4 hours, and then air-cooled to room temperature, so that the area percentage of the as-cast residual phase is less than 1.0%, and the maximum residual phase size is less than 30 μm; Hot rolling deformation: The 7050 aluminum alloy ingot after homogenization annealing is subjected to hot rolling plastic deformation at a rolling temperature of 430±5°C and a total deformation of 70% to obtain a 7050 aluminum alloy rolled piece; Solution-aging treatment: The 7050 aluminum alloy rolled piece is kept at 470°C for 1 hour for solution treatment, and then kept at 120°C for 24 hours for aging treatment to obtain a 7050 aluminum alloy piece.

2. The preparation process according to claim 1, characterized in that The purity of the pure metal aluminum, pure metal zinc, pure metal magnesium and pure metal copper is 99.9%. The Zr content in the aluminum-zirconium master alloy is 10 wt.%, and the balance is Al.

3. The preparation process according to claim 1, characterized in that The frequency of the electromagnetic stirring is 20 Hz and the current is 100 A.

4. The preparation process according to claim 1, characterized in that The graded degassing refining comprises: Stage 1: When the melt temperature drops to 730°C, 0.3 wt.% of refining agent is added to the melt by the graphite bell pressure method. After no obvious bubbles appear on the melt surface, the graphite bell is removed and the melt is connected to the argon injection system for 5 minutes. The second stage: 0.3wt.% refining agent was added by the graphite bell press method. After no obvious bubbles were found on the melt surface, the graphite bell was removed and then ultrasonic-assisted treatment was performed for 5 minutes.

5. The preparation process according to claim 4, characterized in that: The refining agent is hexachloroethane; the purity of the argon in the argon blowing system is ≥99.99% and the flow rate is 1.5 L / min; the frequency of the ultrasonic-assisted treatment is 15-20 kHz and the power is 200 W.

6. The preparation process according to claim 1, characterized in that The static slagging is: After refining, let it stand at 730℃ for 20 minutes to allow inclusions to float fully and completely remove the slag on the surface of the melt; The grain refinement is: A titanium alloy bell jar preheated to 400°C was used to press-in 0.05wt.% of grain refiner, and the melt temperature was controlled to be no higher than 730°C and kept warm for 10 minutes. The grain refiner is an Al-3Ti-B master alloy, the composition of which is: Ti: 3.0wt.%, B: 1.0wt.%, and the balance is Al.

7. The preparation process according to claim 1, characterized in that The cooling water temperature of the water-cooled copper mold is not higher than 5° C., and the solidification cooling rate of the melt is controlled to be 25-30° C. / s.

8. The preparation process according to claim 1, characterized in that: The area percentage of the residual phase of the as-cast structure is sampled and detected in at least 3 different viewing fields using a metallographic microscope, and the average value is ≤1.0%.

9. The preparation process according to claim 1, characterized in that: In the hot rolling deformation, the rolling is carried out in 7 passes, and the reduction rate of each pass is 15%.

10. A high-strength and high-conductivity 7050 aluminum alloy, characterized in that: The 7050 aluminum alloy is prepared by the preparation process according to any one of claims 1 to 9, and its composition includes, by weight percentage, 6.1 to 6.3 wt.% of Zn, 2.3 to 2.5 wt.% of Mg, 2.4 to 2.6 wt.% of Cu, and 0.12 to 0.14 wt.% of Zr, with the remainder being Al and unavoidable impurities, with the total amount of impurities not exceeding 0.15 wt.%.

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