High-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing rib and preparation method thereof

Abstract

The invention discloses a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for an ultra-large aircraft wing rib and a preparation method of the high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile, the Al-Zn-Mg-Cu aluminum alloy profile comprises the following alloy components in percentage by mass: 5.5-5.8% of Zn, 1.6-1.9% of Mg, 1.9-2.5% of Cu, 0.2-0.3% of Mn, 0.1-0.2% of Zr, 0.1-0.2% of Cr, 0.1-0.2% of Ti, less than or equal to 0.12% of Fe, less than or equal to 0.1% of Si and the balance of Al and inevitable impurities, and the content of a single impurity is not more than 0.05%. The total content of impurities does not exceed 0.15%; the preparation process comprises the steps of smelting casting, two-stage homogenizing annealing, extrusion, solution treatment, stretch straightening and two-stage artificial aging, a mold adopted during extrusion is a double-mold-hole mold, and mold holes of the mold are distributed left and right and are in central symmetry. According to the Al-Zn-Mg-Cu aluminum alloy and the preparation method thereof, by optimizing the alloy components, adjusting the layout of the die holes of the die and the solid solution and aging process, the grain structure of the profile is fine and uniform in distribution, and the Al-Zn-Mg-Cu aluminum alloy guarantees excellent strength while the fracture toughness is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of aluminum alloy preparation, and in particular to a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs and a preparation method thereof. Background Art

[0002] Aluminum alloys have the characteristics of low specific gravity, high specific strength, high specific rigidity, excellent processing properties, and low cost, and are widely used in defense and civilian industries such as aerospace, transportation, shipbuilding, and machinery and electrical appliances. Among them, Al-Zn-Mg-Cu alloys are widely used in the aerospace field because of their high strength, low density, good corrosion resistance and fatigue resistance. As the main structural material of aircraft wings, existing Al-Zn-Mg-Cu alloys (such as 7150, 7055, and 7449) can meet the performance requirements of current wing structures and large takeoff weights for wing structural materials (mainly upper wing structural materials). That is, they can meet the high compressive stresses that the upper wing of an aircraft needs to withstand during flight and have a certain degree of fracture toughness.

[0003] However, the advancement of aerospace technology has led to the development of larger, ultra-large jet aircraft with exceptionally high load capacities, placing new demands on wing structural materials to meet these new design criteria. For these ultra-large aircraft, the upper wing must withstand not only the high compressive stresses experienced during flight but also the high tensile stresses experienced during landing. This tensile stress stems from the downward bending loads exerted by the larger, heavier wings and the extra-heavy weight of the aircraft during landing. While current Al-Zn-Mg-Cu alloys meet the strength requirements of ultra-large aircraft, their fracture toughness falls short in this new operating environment, hindering the development of ultra-large aircraft wing structures. Therefore, to meet the mechanical performance requirements of these new large aircraft wings, the development of new Al-Zn-Mg-Cu alloys favors higher toughness and strength. However, fracture toughness generally decreases with increasing material strength. For metals such as steel, titanium, aluminum, magnesium, and their alloys, fracture toughness decreases with increasing yield strength. Therefore, the urgent problem to be solved is how to maintain high strength while achieving excellent fracture toughness. Summary of the Invention

[0004] To solve the above technical problems, the present invention provides a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs and a preparation method thereof, which can maintain high strength while having excellent fracture toughness.

[0005] The technical solution adopted in the present invention is:

[0006] In a first aspect, the present invention provides a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs. The alloy composition of the Al-Zn-Mg-Cu aluminum alloy profile includes, by mass percentage, 5.5-5.8% Zn, 1.6-1.9% Mg, 1.9-2.5% Cu, 0.2-0.3% Mn, 0.1-0.2% Zr, 0.1-0.2% Cr, 0.1-0.2% Ti, ≤0.12% Fe, ≤0.1% Si, and the remainder is Al and unavoidable impurities, and the content of a single impurity does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

[0007] Furthermore, the mass ratio of Zn to Mg is 2.9 to 3.6, and the total mass percentage of Zn, Mg and Cu is 9.0 to 9.8%.

[0008] Furthermore, the Al-Zn-Mg-Cu aluminum alloy profile has a tensile strength of ≥70 ksi, a yield strength of ≥59 ksi, an elongation of ≥12%, and a fracture toughness along the LT direction of ≥38 MPa·m 1 / 2 , fracture toughness along TL direction ≥ 29MPa·m 1 / 2 .

[0009] The present invention also provides a method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for a super-large aircraft wing rib, comprising the steps of:

[0010] (1) calculating the amount of raw materials according to the alloy composition ratio of the Al-Zn-Mg-Cu aluminum alloy and preparing the materials, and obtaining an Al-Zn-Mg-Cu aluminum alloy ingot by smelting and casting;

[0011] (2) performing a double-stage homogenization annealing treatment on the Al-Zn-Mg-Cu aluminum alloy ingot;

[0012] (3) hot extruding the homogenized ingot to obtain an F-state Al-Zn-Mg-Cu aluminum alloy extruded profile;

[0013] (4) performing solid solution treatment on the F-state Al-Zn-Mg-Cu aluminum alloy extrusion profile;

[0014] (5) stretching and straightening the Al-Zn-Mg-Cu aluminum alloy extruded profile after solid solution treatment;

[0015] (6) The Al-Zn-Mg-Cu aluminum alloy extruded profile after stretching and straightening is subjected to secondary artificial aging to obtain a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile finished product.

[0016] Furthermore, the smelting and casting process in step (1) is specifically as follows: first, the raw materials after proportioning are added into the smelting furnace in the order of remelting ingot, copper plate, zinc ingot, scrap, aluminum-chromium master alloy, and aluminum-zirconium master alloy; after all the raw materials in the smelting furnace are melted, the melt temperature is measured, and slag is skimmed when the melt temperature is 700-745°C; then the melt is heated to 725-745°C and magnesium ingot and aluminum-beryllium alloy are added; after the melt is completely flattened, the aluminum-titanium master alloy is added, and refined, degassed, and filtered; then the melt is transferred from the furnace to the holding furnace and allowed to stand for 20-30 minutes before ingot casting; during the casting process, the casting temperature of the hot end of the flow plate is controlled to be 685-705°C.

[0017] Furthermore, the two-stage homogenization annealing process in step (2) is:

[0018] The uniform temperature of the first stage is 455-465℃, the holding time is 4-8h, and the heating rate is 50-70℃ / h;

[0019] The second stage homogenization temperature is 470-480°C, the holding time is 24-48h, and the heating rate is 10-30°C / h.

[0020] Furthermore, the extrusion parameters in step (3) are: mold temperature of 390-420°C, mold insulation time of 6-12h; ingot heating temperature of 390-410°C, insulation time of 10-30min; extrusion barrel temperature of 380-420°C, and extrusion speed of 0.5-1.0mm / s.

[0021] Furthermore, in the step (3), for the I-beam profile, the die used for extrusion is a double-die hole die, and the die holes of the die are distributed on the left and right and are centrally symmetrical.

[0022] Furthermore, in step (4), the solution treatment temperature is 472-482°C, the holding time is 120-180 min, the quenching delay time does not exceed 15 s, and after the solution treatment, an immersion water cooling quenching method is adopted, the immersion time is 10-15 min, and the water temperature before and after quenching is controlled below 25°C.

[0023] Furthermore, the stretching and straightening deformation rate in step (5) is 2.0-3.0%.

[0024] Furthermore, the double-stage artificial aging process in step (6) is:

[0025] The first stage artificial aging temperature is 120±5℃, and the holding time is 10-12h;

[0026] The second stage artificial aging temperature is 160±5℃, and the holding time is 8 to 10 hours.

[0027] In the above technical solution, the present invention ensures that the Al-Zn-Mg-Cu aluminum alloy profile has both high strength and high fracture toughness by combining the following aspects:

[0028] In the first aspect, the present invention optimizes the alloy composition of the Al-Zn-Mg-Cu aluminum alloy, wherein the content of the alloying elements Zn, Mg, and Cu is mainly optimized, and the mass ratio of Zn and Mg is adjusted to 2.9-3.6, and the total mass percentage of Zn, Mg, and Cu is 9.0-9.8%, which promotes the precipitation of the grain boundary phase MgZn2 in the form of fine dispersed precipitation rather than continuous grain boundary precipitation. If the Zn and Mg content is too high, such as Zn 5.8-6.9% and Mg 2.2-2.5%, although it can improve the strength, it will cause excessive precipitation of the grain boundary phase MgZn2 and form a continuous network structure, which becomes a crack propagation channel; In addition, the Fe and Si content is reduced to reduce brittle intermetallic compounds such as Al7Cu2Fe and Mg2Si, reducing the probability of crack initiation. Through the above alloy composition optimization, the grain boundary brittleness is reduced and the crack propagation resistance is improved. In addition, a certain amount of Zr element is added to regulate the uniformity of the grain structure, making the grains small and uniform, and improving a certain strength through fine grain strengthening;

[0029] Secondly, the present invention also optimizes the die hole layout of the extrusion die based on the optimization of the alloy composition. The die is designed as a dual-die die with two die holes distributed left and right and symmetrically centered. The die hole layout can adjust the metal flow, effectively control the grain morphology and size, and effectively improve the fracture toughness of the material. At the same time, the change in the die hole layout will affect the stress distribution, and the stress will have a certain promoting effect on the aging process. The promoting effect here mainly refers to the strengthening aging effect, which can improve the strength of the material to a certain extent.

[0030] On the third aspect, the present invention also adjusts the solution process and aging process based on the optimization of alloy composition to make up for the strength loss caused by the optimization of alloy composition. Specifically, during the solution treatment, a solution process of 472-482℃*120-180min is adopted, and an immersion water-cooled quenching method is adopted, with an immersion time of 10-15min. The solution treatment fully dissolves the second phases such as η(MgZn2) and S(Al2CuMg) at the grain boundaries and in the grains at a higher temperature to form a supersaturated solid solution, providing the necessary element basis for subsequent precipitation strengthening; at the same time, optimizing the holding time can effectively inhibit local melting of grain boundaries and element segregation; during the aging treatment, a double-stage aging process of 120±5℃*10-12h+160±5℃*8-10h is adopted. The temperature and time are regulated by the aging process to control the nucleation density, size and distribution state of the η' phase, which directly affects the strengthening behavior and fracture mechanism of the alloy. The present invention employs a two-stage aging process (first promoting η′ nucleation at a low temperature, then promoting its growth and uniform distribution at a moderate temperature) to produce a large number of fine η′ phases dispersed within the grains, achieving high strength. Simultaneously, it inhibits the continuous precipitation of coarse η phases at grain boundaries, helping to improve grain boundary toughness and corrosion resistance. Overall, the present invention, through the coordinated optimization of the solution-aging process, effectively achieves a transition from coarse, continuous precipitate phase morphology to fine, dispersed precipitates, promoting a synergistic improvement in both strength and fracture toughness.

[0031] The beneficial effects of the present invention are:

[0032] The present invention provides a method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs. By optimizing the alloy composition, adjusting the mold hole layout, and the solid solution and aging processes, the grains are made fine and evenly distributed, and the precipitation of the MgZn2 phase at the grain boundary is promoted to be fine and dispersed rather than continuous grain boundary precipitation. At the same time, the precipitation content of the brittle phase at the grain boundary is reduced, that is, the segregation of coarse η phase and θ phase is reduced, thereby not only improving the fracture toughness of the Al-Zn-Mg-Cu aluminum alloy, but also ensuring excellent strength. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a die hole layout diagram of the extrusion die of Example 1 of the present invention;

[0034] Figure 2 This is a die hole layout diagram of the extrusion die of Comparative Example 1 of the present invention;

[0035] Figure 3 This is a die hole layout diagram of the extrusion die of Comparative Example 2 of the present invention;

[0036] Figure 4 Schematic diagram of sampling positions for mechanical properties and fracture toughness testing;

[0037] Figure 5This is a metallographic photograph of the profile prepared in Example 1;

[0038] Figure 6 This is a metallographic photograph of the profile prepared in Comparative Example 1;

[0039] Figure 7 This is a bright field transmission electron microscope image of the profile prepared in Example 1;

[0040] Figure 8 This is a bright field transmission electron microscope image of the profile prepared in Comparative Example 3;

[0041] Figure 9 This is a metallographic photograph of the profile prepared in Comparative Example 3. DETAILED DESCRIPTION

[0042] The present invention provides a method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs. To clarify the objectives, technical solutions, and advantages of the present invention, the present invention is described in further detail below. It should be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention.

[0043] Example 1

[0044] This embodiment prepares a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs. The profile is an I-beam profile. The steps are as follows:

[0045] (1) Melting and casting

[0046] The raw material dosage is calculated and prepared according to the alloy composition ratio of Al-Zn-Mg-Cu aluminum alloy, which is: Zn 5.6%, Mg 1.7%, Cu 2.3%, Mn 0.25%, Zr 0.15%, Cr 0.2%, Ti 0.18%, Fe 0.10%, Si 0.10%, and the remainder is Al and unavoidable impurities. The content of each impurity shall not exceed 0.05%, and the total content of impurities shall not exceed 0.15%;

[0047] After the material preparation is completed, the raw materials with the completed proportions are first added to the smelting furnace in the order of remelting ingots, copper plates, zinc ingots, scrap materials, aluminum-chromium master alloys, and aluminum-zirconium master alloys. After all the raw materials in the smelting furnace are melted, the melt temperature is measured, and slag is skimmed when the melt temperature is 720°C; the melt is then heated to 735°C and magnesium ingots and aluminum-beryllium alloys are added. After the melt is completely leveled, the aluminum-titanium master alloy is added, and refined, degassed, and filtered. The melt is then transferred from a converter to a holding furnace and allowed to stand for 30 minutes before ingot casting. During the casting process, the casting temperature of the hot end of the flow plate is controlled to be 690-695°C to obtain an Al-Zn-Mg-Cu aluminum alloy ingot.

[0048] (2) Two-stage homogenization annealing treatment

[0049] The ingot after casting is subjected to homogenization annealing, wherein the first stage homogenization temperature is 460°C, the holding time is 6 hours, and the heating rate is 60°C / h; the second stage homogenization annealing temperature is 473°C, the holding time is 36 hours, and the heating rate is 20°C / h. After the second stage homogenization and holding is completed, the ingot is air-cooled to room temperature;

[0050] (3) Extrusion molding

[0051] After homogenization is completed, the ingot is first lathed and peeled 7mm on one side; then the ingot is hot extruded to obtain F-state Al-Zn-Mg-Cu aluminum alloy extruded profiles; specifically:

[0052] Mould: The mould of I-beam profile is designed as a double-mould-hole mould. The mould holes are distributed on the left and right and are centrally symmetrical. The hole spacing is 60mm. Figure 1 As shown; the mold preheating temperature is 410℃, the holding time is 6h, and the mold transfer time is 8min;

[0053] Ingot casting: The preheating temperature of the ingot is 400℃ and the holding time is 18min;

[0054] Extrusion barrel: The preheating temperature of the extrusion barrel is 410℃;

[0055] Extrusion: The extrusion was carried out by reverse extrusion with an extrusion ratio of 50.88, an extrusion speed of 0.8 mm / s, and an ingot pressure of 60 mm to obtain an F-state I-beam extruded semi-finished product;

[0056] Pre-stretching: pre-stretch the I-beam extruded profile, and the pre-stretching deformation is 1.0%;

[0057] Pre-sawing: Pre-saw the pre-stretched I-beam extruded profile, cutting off 1200mm at the head end and 1000mm at the tail end;

[0058] (4) Solution treatment

[0059] The pre-sawn I-beam profiles were solution treated, specifically at 482°C for 180 minutes, and quenched by immersion water cooling with a quenching delay of 12 seconds. After the profiles were completely immersed in water, they were kept immersed for 10 minutes. The water temperature was controlled at 22°C before and after quenching.

[0060] (5) Stretch straightening

[0061] The I-beam profile after solution treatment is stretched and straightened, with a stretching and straightening deformation of 2.0%. The interval between the completion of stretching and straightening and the completion of solution treatment is 2.5 hours;

[0062] (6) Artificial aging

[0063] The I-beam profile after stretching and straightening is subjected to secondary artificial aging. The aging process is: 120℃±5℃*640min+160℃±5℃*600min. The maximum deviation of the insulation time is 2min. After aging, a high-strength and high-toughness I-beam profile product is obtained.

[0064] Example 2

[0065] This embodiment prepares a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs. The profile is an I-beam profile. The steps are as follows:

[0066] (1) Melting and casting

[0067] The raw material dosage is calculated and prepared according to the alloy composition ratio of Al-Zn-Mg-Cu aluminum alloy, which is: Zn 5.8%, Mg 1.8%, Cu 2.0%, Mn 0.24%, Zr 0.17%, Cr 0.18%, Ti 0.15%, Fe 0.11%, Si 0.10%, and the remainder is Al and unavoidable impurities, with the content of each impurity not exceeding 0.05%, and the total content of impurities not exceeding 0.15%;

[0068] After the material preparation is completed, the raw materials with the completed proportions are first added to the smelting furnace in the order of remelting ingots, copper plates, zinc ingots, scrap materials, aluminum-chromium master alloys, and aluminum-zirconium master alloys. After all the raw materials in the smelting furnace are melted, the melt temperature is measured, and slag is skimmed when the melt temperature is 710°C; the melt is then heated to 740°C and magnesium ingots and aluminum-beryllium alloys are added. After the melt is completely flattened, the aluminum-titanium master alloy is added, and refined, degassed, and filtered. The melt is then transferred from a converter to a holding furnace and allowed to stand for 30 minutes before ingot casting. During the casting process, the casting temperature of the hot end of the flow plate is controlled within the range of 690-695°C to obtain an Al-Zn-Mg-Cu aluminum alloy ingot.

[0069] (2) Two-stage homogenization annealing treatment

[0070] The ingot after casting is subjected to homogenization annealing, wherein the first stage homogenization temperature is 460°C, the holding time is 6 hours, and the heating rate is 60°C / h; the second stage homogenization annealing temperature is 470°C, the holding time is 48 hours, and the heating rate is 20°C / h. After the second stage homogenization and holding is completed, the ingot is air-cooled to room temperature;

[0071] (3) Extrusion molding

[0072] After homogenization is completed, the ingot is first lathed and peeled 8mm on one side; then the ingot is hot extruded to obtain F-state Al-Zn-Mg-Cu aluminum alloy extruded profiles; specifically:

[0073] Mold: The mold for the I-beam profile is designed as a double-mold mold. The mold holes are distributed left and right and are centrally symmetrical, with a hole spacing of 50mm. The mold preheating temperature is 410℃, the holding time is 12h, and the mold transfer time is 10min.

[0074] Ingot casting: The preheating temperature of the ingot is 400℃ and the holding time is 30min;

[0075] Extrusion barrel: The preheating temperature of the extrusion barrel is 420℃;

[0076] Extrusion: The extrusion was carried out by reverse extrusion with an extrusion ratio of 50.88, an extrusion speed of 0.8 mm / s, and an ingot pressure of 80 mm to obtain an F-state I-beam extruded semi-finished product;

[0077] Pre-stretching: pre-stretch the I-beam extruded profile, and the pre-stretching deformation is 0.8%;

[0078] Pre-sawing: Pre-saw the pre-stretched I-beam extruded profile, cutting 1300mm at the head end and 800mm at the tail end;

[0079] (4) Solution treatment

[0080] The pre-sawn I-beam profiles were solution treated, specifically at 475°C for 140 minutes, and quenched by immersion water cooling with a quenching delay of 10 seconds. After the profiles were completely immersed in water, they were kept immersed for 11 minutes. The water temperature was controlled at 20°C before and after quenching.

[0081] (5) Stretch straightening

[0082] The I-beam profile after solution treatment is stretched and straightened, with a stretching and straightening deformation of 2.5%. The interval between the completion of stretching and straightening and the completion of solution treatment is 2.5 hours;

[0083] (6) Artificial aging

[0084] The I-beam profile after stretching and straightening is subjected to secondary artificial aging. The aging process is: 120℃±5℃*640min+160℃±5℃*600min. The maximum deviation of the insulation time is 13min. After aging, a high-strength and high-toughness I-beam profile product is obtained.

[0085] Comparative Example 1

[0086] The difference between this comparative example and Example 1 is:

[0087] The alloy composition ratio in this comparative example is: Zn 6.3%, Mg 2.9%, Cu 1.8%, Mn 0.15%, Cr 0.2%, Ti 0.18%, Fe 0.15%, Si 0.15%, and the balance is Al and unavoidable impurities;

[0088] The mold in this comparative example is a double-mold mold, and the mold holes of the mold are distributed left and right and are axisymmetric. Figure 2 As shown;

[0089] In this comparative example, the solution treatment process was 477°C*120min;

[0090] The aging process in this comparative example is 120°C*24h.

[0091] The other parameters are the same.

[0092] Comparative Example 2

[0093] The difference between this comparative example and Example 1 is:

[0094] The alloy composition ratio in this comparative example is: Zn 6.3%, Mg 2.9%, Cu 1.8%, Mn 0.15%, Cr 0.2%, Ti 0.18%, Fe 0.15%, Si 0.15%, and the balance is Al and unavoidable impurities;

[0095] The mold in this comparative example is a single-hole mold, and the mold hole of the mold is located in the center of the mold. Figure 3 As shown;

[0096] In this comparative example, the solution treatment process was 477°C*120min;

[0097] The aging process in this comparative example is 120°C*24h.

[0098] The other parameters are the same.

[0099] Comparative Example 3

[0100] The difference between this comparative example and Example 1 is:

[0101] In this comparative example, the alloy composition ratio is: Zn 6.3%, Mg 2.9%, Cu 1.8%, Mn 0.15%, Cr 0.2%, Ti 0.18%, Fe 0.15%, Si 0.15%, and the balance is Al and unavoidable impurities;

[0102] In this comparative example, the solution treatment process was 477°C*120min;

[0103] The aging process in this comparative example is 120°C*24h.

[0104] The other parameters are the same.

[0105] Comparative Example 4

[0106] The difference between this comparative example and Example 1 is:

[0107] The alloy composition ratio in this comparative example is: Zn 6.3%, Mg 2.9%, Cu 1.8%, Mn 0.15%, Cr 0.2%, Ti 0.18%, Fe 0.15%, Si 0.15%, and the balance is Al and unavoidable impurities.

[0108] The other parameters are the same.

[0109] The finished I-beam profiles prepared in Examples 1, 2 and Comparative Examples 1-4 were prepared as follows: Figure 4 The samples were taken at position A and position B, and their mechanical properties and fracture toughness were tested. The test results are shown in Table 1 and Table 2, respectively.

[0110] Table 1 Mechanical properties test results (sampling along the longitudinal direction)

[0111]

[0112] Table 2 Fracture toughness test results

[0113]

[0114] Note: L refers to longitudinal direction and T refers to transverse direction.

[0115] Analysis of the mechanical properties and fracture toughness test results in Tables 1 and 2 above shows that the profiles produced in Examples 1 and 2 of the present invention exhibit both high strength and fracture toughness. However, the profiles produced in Comparative Examples 1 and 2 exhibit high strength but low fracture toughness. The profile produced in Comparative Example 3 exhibits even higher strength but also low fracture toughness. Comparative Example 4, despite its high alloy composition and two-stage aging process, exhibits the highest strength, but also low fracture toughness. Furthermore, in Comparative Examples 1-3, only the die hole layout differs, demonstrating that die hole layout significantly influences the profile's mechanical properties and fracture toughness. Among them, for Comparative Example 1, due to its high overall alloy content, its strength meets the requirements, but its mold holes are distributed in a bilaterally symmetrical manner, which will amplify the anisotropy at different positions of the I-beam, resulting in deviations in the performance of different positions of the I-beam, especially for the fracture toughness, the fracture toughness difference between points A and B is obvious; for Comparative Example 2, due to its high overall alloy content, its strength meets the requirements, but its mold hole is a single mold hole. Due to the uneven metal flow and temperature distribution, coarse grains and inclusion concentration may be induced, which ultimately weaken the crack propagation resistance and affect the fracture toughness of the material; for Comparative Example 3, its mold holes are distributed in a centrally symmetrical manner. By adjusting the metal flow through the mold hole layout, the grain morphology and size can be effectively controlled, and the fracture toughness of the material can be effectively improved. In addition, the difference in fracture toughness at different positions is small. At the same time, the change in the mold hole layout will also affect the stress distribution, and stress will have a certain promoting effect on the aging process, which can improve the strength of the material to a certain extent, making the strength of Comparative Example 3 higher than that of Comparative Examples 1 and 2; Compared with Comparative Example 3, Comparative Example 4 optimizes the aging process, further improves the strength, and also improves the fracture toughness.

[0116] In addition, the profiles prepared in Example 1, Comparative Example 1 and Comparative Example 3 were subjected to metallographic examination, respectively. Figure 5 、 Figure 6 、 Figure 9 As shown. Figure 5 and Figure 6 、 Figure 9 It can be seen that the die hole layout can affect the grain morphology and size. Figure 5 and Figure 9 The grains in the steel are small and evenly distributed, which improves the strength and toughness; Figure 6 The coarse grains in the steel will not only reduce the overall strength and toughness of the material, but also reduce the grain boundary channels, making crack propagation easier, resulting in a further decrease in the fracture toughness in the LT direction. Moreover, its strong grain directionality will also enhance the anisotropy of the material itself.

[0117] In addition, the profiles prepared in Example 1 and Comparative Example 3 were tested by transmission electron microscopy. Figure 7 and Figure 8 As shown. Figure 7 and Figure 8 It can be seen from the comparison that after optimizing the alloy composition (especially the Zn / Mg ratio) and the solid solution and aging treatment processes (especially the aging process), Figure 7 The grain boundary area in the lattice is obviously more "clean", and the distribution of the second phase at the grain boundary tends to be discrete, avoiding Figure 8 The continuous "network structure" appears in the alloy. This structural change has a significant impact on fracture toughness: continuous grain boundary precipitates easily become crack initiation sources and rapid expansion paths under external loads, resulting in an increased tendency for intergranular fracture, thereby reducing the fracture toughness of the alloy; while the discontinuity of grain boundary precipitates helps deflect and passivate the crack expansion path, delaying the crack propagation process and improving the material's ability to absorb deformation energy, thereby significantly enhancing its fracture toughness. This also proves that the present invention can accurately control the grain boundary behavior in the aluminum alloy structure by optimizing the alloy composition and heat treatment process, and can effectively improve the fracture toughness.

[0118] It should be noted that the parts not described in the present invention can be implemented by adopting or drawing on existing technologies.

[0119] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the scope of protection of the present invention.

Claims

1. A high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for ultra-large aircraft wing ribs, characterized in that: The alloy composition of the Al-Zn-Mg-Cu aluminum alloy profile includes, by mass percentage, Zn 5.5-5.8%, Mg 1.6-1.9%, Cu 1.9-2.5%, Mn 0.2-0.3%, Zr 0.1-0.2%, Cr 0.1-0.2%, Ti 0.1-0.2%, Fe≤0.12%, Si≤0.1%, and the rest is Al and unavoidable impurities, and the content of a single impurity does not exceed 0.05%, and the total impurity content does not exceed 0.15%.

2. The high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 1, characterized in that: The mass ratio of Zn to Mg is 2.9 to 3.6, and the total mass percentage of Zn, Mg and Cu is 9.0 to 9.8%.

3. The high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 1, characterized in that: The Al-Zn-Mg-Cu aluminum alloy profile has a tensile strength of ≥70 ksi, a yield strength of ≥59 ksi, an elongation of ≥12%, and a fracture toughness along the LT direction of ≥38 MPa·m 1 / 2 , fracture toughness along TL direction ≥ 29MPa·m 1 / 2 .

4. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for a super-large aircraft wing rib according to any one of claims 1 to 3, characterized in that: Including steps: (1) calculating the amount of raw materials according to the alloy composition ratio of the Al-Zn-Mg-Cu aluminum alloy and preparing the materials, and obtaining an Al-Zn-Mg-Cu aluminum alloy ingot by smelting and casting; (2) performing a double-stage homogenization annealing treatment on the Al-Zn-Mg-Cu aluminum alloy ingot; (3) hot extruding the homogenized ingot to obtain an F-state Al-Zn-Mg-Cu aluminum alloy extruded profile; (4) performing solid solution treatment on the F-state Al-Zn-Mg-Cu aluminum alloy extrusion profile; (5) stretching and straightening the Al-Zn-Mg-Cu aluminum alloy extruded profile after solid solution treatment; (6) The Al-Zn-Mg-Cu aluminum alloy extruded profile after stretching and straightening is subjected to secondary artificial aging to obtain a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile finished product.

5. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: The smelting and casting process in step (1) is specifically as follows: first, the raw materials after proportioning are added into the smelting furnace in the order of remelting ingot, copper plate, zinc ingot, scrap, aluminum-chromium master alloy, and aluminum-zirconium master alloy; after all the raw materials in the smelting furnace are melted, the melt temperature is measured, and slag is skimmed when the melt temperature is 700-745°C; then, the melt is heated to 725-745°C and magnesium ingot and aluminum-beryllium alloy are added; after the melt is completely flattened, the aluminum-titanium master alloy is added, and the melt is refined, degassed, and filtered; then, the melt is transferred from the furnace to the holding furnace and left to stand for 20-30 minutes before ingot casting; during the casting process, the casting temperature of the hot end of the flow plate is controlled to be 685-705°C.

6. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: The double-stage homogenization annealing process in step (2) is: The uniform temperature of the first stage is 455-465℃, the holding time is 4-8h, and the heating rate is 50-70℃ / h; The second stage homogenization temperature is 470-480°C, the holding time is 24-48h, and the heating rate is 10-30°C / h.

7. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: The extrusion parameters in step (3) are: mold temperature of 390-420° C., mold insulation time of 6-12 hours; ingot heating temperature of 390-410° C., insulation time of 10-30 minutes; extrusion barrel temperature of 380-420° C., and extrusion speed of 0.5-1.0 mm / s.

8. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: In the step (3), for the I-beam profile, the die used for extrusion is a double-die-hole die, and the die holes of the die are distributed on the left and right and are centrally symmetrical.

9. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: In the step (4), the solution treatment temperature is 472-482° C., the holding time is 120-180 min, the quenching delay time does not exceed 15 s, and after the solution treatment, an immersion water cooling quenching method is adopted, the immersion time is 10-15 min, and the water temperature before and after quenching is controlled below 25° C.

10. The method for preparing a high-strength and high-toughness Al-Zn-Mg-Cu aluminum alloy profile for super-large aircraft wing ribs according to claim 4, characterized in that: The double-stage artificial aging process in step (6) is: The first stage artificial aging temperature is 120±5℃, and the holding time is 10-12h; The second stage artificial aging temperature is 160±5℃, and the holding time is 8 to 10 hours.

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