CN116179908A - Ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and preparation method thereof - Google Patents

Abstract

The invention relates to a superstrong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and a preparation method thereof, and aims to solve the problem that the existing aluminum alloy annular forging cannot meet the aerospace use requirement. According to the invention, through alloy composition optimization, ingot quality control, multistage homogenization treatment technology, forging forming technology, tertiary quenching of toughening heat treatment and two-stage aging technology, the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging is produced, and the residual stress of the annular forging is effectively reduced and the fracture toughness of the annular forging is improved by controlling the cold compression quantity and quenching water temperature. The invention is applied to the field of aluminum alloy annular forging preparation.

Description

A kind of super-strength, high-toughness, corrosion-resistant aluminum alloy annular forging for aerospace and preparation method thereof

technical field

The invention relates to an annular forging of super-strength, high-toughness and corrosion-resistant aluminum alloy for aerospace and a preparation method thereof.

Background technique

With the rapid development of my country's aerospace industry, more stringent requirements have been put forward for basic materials. While the diameter and wall thickness of forged ring forgings are required to increase, the performance of forged ring forgings is required to have higher strength, toughness, and corrosion resistance. Need to develop tensile strength ≥ 600MPa, yield strength ≥ 570MPa, elongation ≥ 8%, fracture toughness ≥ 27KIC/MPa m ^1/2 , electrical conductivity ≥ 37% IACS, exfoliation corrosion EB level or above, maximum wall thickness 115mm, Ring forgings with a maximum diameter of 1500mm and a stable production process. The existing aluminum alloy ring forging products are affected by the deformation mode, and the strength and toughness are lower than the extruded materials of the same material. The tensile strength is 500MPa and the toughness is lower than 25KIC/MPa·m ^1/2 , which is far from satisfying aerospace users. For the demand for forging materials, it is necessary to carry out better alloy composition and process control to achieve the overall improvement of the performance of ring forging products and the coordination and matching of various properties such as strength, toughness, corrosion resistance, and electrical conductivity.

Contents of the invention

The purpose of the present invention is to solve the problem that the existing aluminum alloy ring forgings have low performance and cannot meet the development needs of the aerospace industry, and realize the comprehensive improvement of the performance of the ring forging products and the strength, toughness, corrosion resistance, The coordination and matching of various properties such as electrical conductivity provides a super-strong, high-toughness, corrosion-resistant aluminum alloy ring forging for aerospace and a preparation method thereof.

A super-strength, high-toughness, corrosion-resistant aluminum alloy annular forging for aerospace in the present invention is composed of elements with mass percentages of Cu: 1.6% to 3.0%, Mg: 1.8% to 2.5%, Zn: 8.4% to 9.7%, and Zr: 0.10% to 0.15%, Cr: 0.02% to 0.04%, Ti: 0.015% to 0.04%, and the balance of Al.

A method for preparing a super-strong, high-toughness, corrosion-resistant aluminum alloy annular forging for aerospace, according to the following steps:

1. According to the mass percentage of elements, Cu: 1.6%-3.0%, Mg: 1.8%-2.5%, Zn: 8.4%-9.7%, Zr: 0.10%-0.15%, Cr: 0.02%-0.04%, Ti : 0.015% to 0.004% and the balance is Al. Weigh aluminum ingots, cathode copper, primary magnesium ingots, zinc ingots, aluminum-zirconium alloy ingots, aluminum-chromium master alloy ingots and aluminum-titanium wire to obtain raw materials, and then in the melting furnace Medium smelting raw materials, melting temperature 720 ℃ ~ 760 ℃, to obtain molten aluminum alloy;

2. Casting the molten aluminum alloy obtained in step 1 into a round ingot by semi-continuous casting;

3. Remove the casting scale of the round ingot at room temperature to obtain an aluminum alloy round ingot from which the scale has been removed;

4. Heat the aluminum alloy round ingot with the scale removed at a temperature of 420°C to 440°C for 12 hours, then heat it up to 470°C for 60 hours, and cool it naturally to room temperature after being released from the furnace to obtain an annealed round ingot. ingot;

5. Put the annealed round ingot into a resistance heating furnace and heat it to 400°C to 450°C to obtain a hot forging ring forging billet;

6. After the ingot is released from the furnace, under the condition of natural air cooling to a surface temperature of 300°C to 400°C, use a forging press to forge the hot forged ring forging blank obtained in step 5 into a ring forging blank to obtain a hot forging ring forging blank;

7. Carry out rough machining of hot forged ring forging wool to obtain rough machined ring forging wool;

8. Put the roughly processed ring forging wool into a resistance heating furnace, keep it at 430-460°C for 2h-4h, heat it up to 470°C for 4h-6h, then raise it to 472°C-480°C for 1h-3h and then quench it , the water temperature before quenching is ≤19°C, the water temperature after quenching is ≤21°C, and the immersion time of forgings in water is 10min～20min;

Nine, the rough-processed ring forging blanks processed in step 8 are subjected to cold compression stress relief treatment to obtain the rough-processed ring forging blanks after stress relief;

10. Put the roughly machined ring forging wool after stress relief into a resistance heating furnace and heat it to a temperature of 115°C to 121°C. After heat preservation treatment for 6h to 12h, the temperature is raised to 154°C to 165°C. After heat preservation treatment for 6h to 12h, the obtained Overaged ring forgings;

11. Process the aging-treated ring forging according to the size of the finished product to obtain the finished ring forging.

The invention produces aluminum with high tensile strength, good fracture toughness and excellent corrosion resistance through the optimization of alloy composition, casting quality control, three-stage solid solution, low-temperature water quenching, cold compression control and double-stage aging. Alloy ring forgings, ring forgings manufactured by the present invention, tested according to GB/T228, longitudinal tensile strength 612N/mm ² ~ 635N/mm ² , non-proportional elongation strength 595N/mm ² ~ 619N/mm ² , elongation after fracture 9.2% to 12.3%; according to GB/T4161, the fracture toughness of ring forgings is 27.78MPa·m ^1/2 to 33.73MPa·m ^1/2 ; according to GB/T12966-2008, the electrical conductivity is 37.23%IACS to 37.68%IACS, According to HB5455 test exfoliation rot EB level.

Description of drawings

Fig. 1 is the step six forging process schematic diagram of the present invention;

Fig. 2 is the low magnification metallographic photograph of the round ingot cast state of embodiment 2;

Fig. 3 is the high power metallographic photograph of the cast state of the round ingot of embodiment 2;

Fig. 4 is the low-magnification SEM photo of the round ingot after the homogenization annealing of embodiment 2;

Fig. 5 is the high-magnification SEM photo of the round ingot after the homogenization annealing of embodiment 2;

Fig. 6 is the low magnification diagram of the metallographic structure of the ring forging piece of embodiment 2;

Fig. 7 is the high magnification diagram of the metallographic structure of the ring forging material of embodiment 2;

Fig. 8 is the low magnification SEM photograph of embodiment 2 annular forging rough material;

Fig. 9 is the high-magnification SEM photograph of the ring forging rough material of embodiment 2;

Fig. 10 is the low magnification SEM photo of the ring forging after the third stage solid solution of embodiment 2;

Fig. 11 is the high-magnification SEM photo of the ring forging after the third-stage solid solution of Example 2;

Figure 12 is a TEM photo of the solid solution structure at different deformation temperatures;

Figure 13 shows the TEM structure of forgings after quenching at different water temperatures;

Figure 14 is a TEM photo of the crystal after T6 peak aging;

Figure 15 is a TEM photo of grain boundaries after T6 peak aging;

Figure 16 is the intragranular TEM photo of the ring forging after dual-stage aging treatment;

Figure 17 is a TEM photo of the grain boundaries of the ring forging after dual-stage aging treatment.

Detailed ways

The technical solution of the present invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.

Specific implementation mode 1: In this implementation mode, a super-strong, high-toughness, corrosion-resistant aluminum alloy annular forging for aerospace is composed of Cu: 1.6% to 3.0%, Mg: 1.8% to 2.5%, and Zn: 8.4%. ～9.7%, Zr: 0.10%～0.15%, Cr: 0.02%～0.04%, Ti: 0.015%～0.04%, and the balance of Al.

Specific embodiment two: In this embodiment, a method for preparing a super-strong, high-toughness, corrosion-resistant aluminum alloy ring forging for aerospace is carried out according to the following steps:

1. According to the mass percentage of elements, Cu: 1.6%-3.0%, Mg: 1.8%-2.5%, Zn: 8.4%-9.7%, Zr: 0.10%-0.15%, Cr: 0.02%-0.04%, Ti : 0.015% to 0.004% and the balance is Al. Weigh aluminum ingots, cathode copper, primary magnesium ingots, zinc ingots, aluminum-zirconium alloy ingots, aluminum-chromium master alloy ingots and aluminum-titanium wire to obtain raw materials, and then in the melting furnace Medium smelting raw materials, melting temperature 720 ℃ ~ 760 ℃, to obtain molten aluminum alloy;

2. Casting the molten aluminum alloy obtained in step 1 into a round ingot by semi-continuous casting;

3. Remove the casting scale of the round ingot at room temperature to obtain an aluminum alloy round ingot from which the scale has been removed;

4. Heat the aluminum alloy round ingot with the scale removed at a temperature of 420°C to 440°C for 12 hours, then heat it up to 470°C for 60 hours, and cool it naturally to room temperature after being released from the furnace to obtain an annealed round ingot. ingot;

5. Put the annealed round ingot into a resistance heating furnace and heat it to 400°C to 450°C to obtain a hot forging ring forging billet;

6. After the ingot is released from the furnace, under the condition of natural air cooling to a surface temperature of 300°C to 400°C, use a forging press to forge the hot forged ring forging blank obtained in step 5 into a ring forging blank to obtain a hot forging ring forging blank;

7. Carry out rough machining of hot forged ring forging wool to obtain rough machined ring forging wool;

8. Put the roughly processed ring forging wool into a resistance heating furnace, keep it at 430-460°C for 2h-4h, heat it up to 470°C for 4h-6h, then raise it to 472°C-480°C for 1h-3h and then quench it , the water temperature before quenching is ≤19°C, the water temperature after quenching is ≤21°C, and the immersion time of forgings in water is 10min～20min;

Nine, the rough-processed ring forging blanks processed in step 8 are subjected to cold compression stress relief treatment to obtain the rough-processed ring forging blanks after stress relief;

10. Put the roughly machined ring forging wool after stress relief into a resistance heating furnace and heat it to a temperature of 115°C to 121°C. After heat preservation treatment for 6h to 12h, the temperature is raised to 154°C to 165°C. After heat preservation treatment for 6h to 12h, the obtained Overaged ring forgings;

11. Process the aging-treated ring forging according to the size of the finished product to obtain the finished ring forging.

Embodiment 3: The difference between this embodiment and Embodiment 1 or 2 is that the aluminum alloy ring forging is Cu: 2.2%, Mg: 2.2%, Zn: 9.2%, Zr: 0.11% by mass percentage of elements , Cr: 0.02%, Ti: 0.022%, and the balance is Al. Weigh aluminum ingots, cathode copper, primary magnesium ingots, zinc ingots, aluminum-zirconium alloy ingots, aluminum-chromium master alloy ingots and aluminum-titanium wires as raw materials. Others are the same as those in Embodiment 1 or 2.

Embodiment 4: This embodiment differs from Embodiment 1 to Embodiment 3 in that: the heating temperature of the round ingot in step 5 is 430°C. Others are the same as one of the specific embodiments 1 to 3.

Embodiment 5: This embodiment differs from Embodiments 1 to 4 in that: in step 6, after the ingot is heated, the air is naturally cooled to a surface temperature of 350° C., and the forging is started. Others are the same as one of the specific embodiments 1 to 4.

Specific Embodiment 6: The difference between this embodiment and one of specific embodiments 1 to 5 is that the forging process in step 6 is: according to the diameter-to-height ratio of 0.40 to 0.45 forging material, the longitudinal compression is repeated three times, the circumferential deformation is elongated, and finally Compressed longitudinally to cake shape, ring forged after center punching. Others are the same as one of the specific embodiments 1 to 5.

Embodiment 7: The difference between this embodiment and one of Embodiments 1 to 6 is that in step 8, in a resistance heating furnace, keep warm at 450°C for 2h, heat up to 470°C for 5h, and then heat up to 475°C for 1h. Quenching treatment, the water temperature before quenching is 16°C, the water temperature after quenching is ≤18°C, and the immersion time of forgings in water is 10min to 20min. Others are the same as one of the specific embodiments 1 to 6.

Embodiment 8: The difference between this embodiment and one of Embodiments 1 to 7 is that in step 9, the stress relief treatment is performed by low-temperature water quenching and cold compression. Others are the same as one of the specific embodiments 1 to 7.

Embodiment 9: This embodiment is different from Embodiment 1 to Embodiment 8 in that: the amount of stress relief compression in step 9 is controlled at 1-3%. Others are the same as one of the specific embodiments 1 to 8.

Embodiment 10: This embodiment is different from one of Embodiments 1 to 9 in that: in step 9, the amount of stress relief compression is controlled at 2%. Others are the same as one of the specific embodiments 1 to 9.

Embodiment 11: This embodiment differs from Embodiments 1 to 10 in that: in step 10, heat to 118°C, keep warm for 9 hours, then heat up to 162°C, keep warm for 11 hours, and perform overaging treatment. Others are the same as those in the first to tenth specific embodiments.

Adopt the following examples to verify the beneficial effects of the present invention:

Embodiment 1. In this embodiment, a method for preparing a super-strength, high-toughness, corrosion-resistant aluminum alloy annular forging for aerospace use is carried out according to the following steps:

1. Weigh the aluminum ingot according to the percentage content of the element mass: Cu: 2.4%, Mg: 2.3%, Zn: 9.4%, Zr: 0.14%, Cr: 0.03%, Ti: 0.027%, and the balance is Al. Cathode copper, primary magnesium ingot, zinc ingot, aluminum-zirconium alloy ingot, aluminum-chromium master alloy ingot and aluminum-titanium wire are used as raw materials, and then the raw materials are smelted in a melting furnace to obtain aluminum alloy melt;

2. Casting the molten aluminum alloy obtained in step 1 into a round ingot by semi-continuous casting;

3. Remove the casting scale of the round ingot at room temperature to obtain an aluminum alloy round ingot from which the scale has been removed;

4. Heat the aluminum alloy round ingot with the scale removed at a temperature of 440°C for 12 hours, then heat it up to 470°C for 60 hours, and cool it to room temperature naturally after being out of the furnace to obtain an annealed round ingot;

5. Put the annealed round ingot into an induction heating furnace and heat it to 435°C to obtain a hot forging ring forging blank;

6. After the ingot is released from the furnace, under the condition of natural air cooling to a surface temperature of 352°C, use a forging press to forge the hot forged ring forging blank obtained in step 5 into a ring forging blank to obtain a ring forging blank;

7. Carry out rough machining of hot forged ring forging wool to obtain rough machined ring forging wool;

8. Put the roughly processed ring forging wool into a resistance heating furnace, keep it at 450°C for 2 hours, heat it up to 470°C for 5 hours, then raise it to 473°C for 2 hours and then quench it. The water temperature before quenching is 15°C, and the water temperature after quenching is 17°C. ℃, forgings immersed in water for 15 minutes;

Nine, the rough processed ring forging wool after step 8 is processed to carry out cold compression stress relief treatment, and the rough processed ring forging wool after stress relief is obtained, the stress relief cold compression is controlled at 2%, and cold compression is added by low temperature water quenching Stress relief treatment can achieve the purpose of improving the fracture toughness of the ring forging and effectively reducing the residual stress of the ring forging.

10. Put the roughly processed ring forging wool after stress relief into a resistance heating furnace and heat it to a temperature of 118°C. After heat preservation treatment for 8 hours, the temperature is raised to 157°C. After heat preservation treatment for 12 hours, an over-aging ring forging is obtained;

11. Precisely machine the aging-treated ring forging according to the size of the finished product to obtain the finished ring forging.

Step 6 forging process in this embodiment is shown in Figure 1. According to the diameter-to-height ratio of 0.40 to 0.45 forging material, longitudinal compression is repeated three times, the circumferential deformation is elongated, and finally longitudinally compressed to cake shape, and ring forging is carried out after center punching .

In this embodiment, through alloy composition optimization, ingot quality control, multi-level homogenization treatment technology, forging molding technology, and toughening heat treatment technology, a super-strong, high-toughness and corrosion-resistant aluminum alloy ring forging is produced. The ring forging manufactured in this embodiment Forgings, tested according to GB/T228, the longitudinal tensile strength is 618-635N/mm ² , the specified non-proportional elongation strength is 601-619N/mm ² , and the elongation after fracture is 9.5-12.3%; the fracture toughness of ring forgings is tested according to GB/T4161 It is 29.14～33.73MPa·m ^1/2 , the electrical conductivity is 37.35～37.68%IACS according to GB/T12966-2008, and the exfoliation corrosion EB level is tested according to HB5455.

Embodiment 2. An industrialized preparation method of a super-strength, high-toughness, corrosion-resistant aluminum alloy ring forging for aerospace is carried out according to the following steps:

1. Weigh the aluminum ingot according to the percentage content of the element mass: Cu: 2.2%, Mg: 2.2%, Zn: 9.2%, Zr: 0.11%, Cr: 0.02%, Ti: 0.022%, and the balance is Al. Cathode copper, primary magnesium ingot, zinc ingot, aluminum-zirconium alloy ingot, aluminum-chromium master alloy ingot and aluminum-titanium wire are used as raw materials, and then the raw materials are smelted in a melting furnace at a temperature of 760°C for 6 hours to obtain an aluminum alloy melt.

2. Casting the molten aluminum alloy obtained in step 1 into a round ingot by semi-continuous casting;

3. Remove the casting scale of the round ingot at room temperature to obtain an aluminum alloy round ingot from which the scale has been removed;

4. Heat the aluminum alloy round ingot with the scale removed at a temperature of 430°C for 12 hours, then heat it up to 470°C for 60 hours, and cool it to room temperature naturally after being out of the furnace to obtain an annealed round ingot;

5. Put the annealed round ingot into an induction heating furnace and heat it to 430°C to obtain a hot forging ring forging blank;

6. After the ingot is released from the furnace, under the condition of natural air cooling to a surface temperature of 350° C., forge the hot forged ring forging blank obtained in step 5 into a ring forging blank to obtain a ring forging blank;

7. Carry out rough machining of hot forged ring forging wool to obtain rough machined ring forging wool;

8. Put the roughly processed ring forging wool into a resistance heating furnace, keep it at 450°C for 2 hours, heat it up to 470°C for 5 hours, and then heat it up to 475°C for 1 hour and then quench it. The water temperature before quenching is 16°C, and the water temperature after quenching is ≤ 18°C, forgings immersed in water for 15 minutes;

Nine, the rough-processed ring forging wool after step 8 is processed is carried out cold compression stress relief treatment, obtains the rough-processed ring forging wool after stress relief, and the stress relief compression is controlled at 1.5%;

10. Put the roughly processed ring forging wool after stress relief into a resistance heating furnace and heat it to 118°C, heat it up to 162°C after 9 hours of heat preservation, and hold it for 11 hours to obtain an over-aging ring forging;

11. Precisely machine the aging-treated ring forging according to the size of the finished product to obtain the finished ring forging.

The forging process in Step 6 of this embodiment is to forge material with diameter-to-height ratio of 0.40 to 0.45, perform longitudinal compression three times, deform and elongate in the circumferential direction, and finally compress longitudinally to cake shape, and perform ring forging after center punching.

The ring-shaped forging produced in this embodiment is tested according to GB/T228. The longitudinal tensile strength is 612N/mm ² to 624N/mm ² , the specified non-proportional elongation strength is 595N/mm ² to 610N/mm ² , and the elongation after fracture is 9.2% to 12.0%; According to GB/T4161, the fracture toughness of ring forgings is 27.78MPa m ^1/2 ~ 31.92MPa m ^1/2 , the electrical conductivity is 37.23 ~ 37.45% IACS according to GB/T12966-2008, and the exfoliation corrosion is tested according to HB5455 Grade EB.

Figures 2 and 3 show the as-cast metallographic photos of the aluminum alloy round ingot in this example. From Figures 2 and 3, it can be seen that the as-cast structure of the alloy is a typical dendrite structure, and the coarse primary solidification precipitates are located at the grain boundaries. There are also a large number of fine precipitates near the grain boundary in the grain. The high-magnification microstructure photos show that there is an obvious lamellar structure at the grain boundary. The AlZnMgCu quaternary phase formed during solidification forms a continuous network with the α(Al) phase. The grain boundary of lamellar eutectic structure distribution, and the second phase of fine size precipitated along the grain boundary in the matrix is MgZn ₂ phase. The overall grain size is relatively uniform.

The purpose of the homogenization treatment of 7000 series alloys is to promote the dissolution of the coarse primary solidification precipitated phase. In addition, it is necessary to promote the dispersed precipitation of Al ₃ Zr particles at high temperature. This phase can pin the grain boundary during subsequent deformation processing and heat treatment. Inhibit recrystallization and improve alloy properties. The temperature range of higher Al ₃ Zr nucleation rate is 420-450°C. Therefore, in order to take into account the dispersion and precipitation of Al ₃ Zr particles and the re-dissolution of the primary solidified phase, after the first-stage homogenization annealing treatment at 420°C to 440°C for 12 hours, perform a high-temperature treatment at 470°C for 60 hours, and then cool naturally after being out of the furnace to room temperature. The SEM photos of the round ingot after homogenization annealing are shown in Figures 4 and 5. It can be seen from the figures that the precipitated phases in the structure after homogenization treatment are fully dissolved back, and the lamellar eutectic structure of the as-cast alloy completely disappears, only sporadic white phases The energy spectrum analysis shows that it is Fe-rich phase, the number and distribution of Fe-rich phase do not change significantly with the prolongation of homogenization time, and the grain size of the alloy does not change significantly after homogenization annealing.

The metallographic structure observation was carried out on the longitudinal section of the aluminum alloy ring forging blank (Fig. 6 and 7). It can be found that the metallographic structure has obvious streamlined characteristics, and there are densely distributed and fine-sized Mg(Zn,Cu,Al) ₂ phases in the alloy, and Fe-containing phases are also observed. The SEM image of the aluminum alloy ring forging wool (Figure 8 and Figure 9), it can be seen that most of the residual phase is Mg(Zn,Cu,Al)2 phase, and it is finely fragmented along the deformation direction, and only contains a small amount of Fe-containing phase. Mutually.

The three-stage quenching process is adopted. The first-stage solution temperature is lower, which can release more deformation storage energy, reduce the recrystallization driving force of high-temperature solution treatment, and retain a higher proportion of deformed structures in ring forgings. The second stage uses Higher temperature treatment ensures that most of the second phase of the alloy dissolves back into the matrix and increases the over-burning temperature of the material. The third-level treatment selects a short-term treatment close to the over-burning temperature to ensure the second phase back-dissolving to the maximum extent, which is the best for the alloy. Strong toughness matching provides maximum space. It can be seen from Figures 10 and 11 that after the three-stage solid solution treatment, the second phase is fully dissolved back, and only a small amount of Fe-rich second phase remains, and the size is relatively small. Figure 12 is a TEM photo of the solid solution structure at different deformation temperatures; where b, d are at 320°C and a, c are at 400°C. After solution treatment, the MgZn ₂ phase in the deformed structure dissolves back, dislocations disappear, and clear and straight subgrain boundaries are formed, as shown by the white arrows in (a) and (b). In addition, nanoscale Al ₃ Zr phases are also found in the solid solution structure, as shown by the white dashed arrows in (c)(d), the Al ₃ Zr phases in the 7xxx series aluminum alloys are precipitated during the homogenization heat treatment process, and the During treatment and solid solution treatment, there is a pinning and drag effect on dislocations and grain boundaries, which can inhibit recrystallization and grain growth.

The quenching water temperature control of ring forgings is the key point to improve its fracture toughness. After quenching at different water temperatures, the TEM photos of the alloy are compared as shown in Figure 13; where a is 20°C, b is 40°C, and c is 60°C; it can be seen from the figure that with With the increase of quenching cooling temperature, the size of precipitated phase increases gradually. After the sample was quenched at 20°C, the size of the precipitated phase at the grain boundary was only 8nm, and the size of the precipitated phase at the grain boundary was significantly smaller than that of other samples, and there was no PFZ at the grain boundary position; at 40°C, the grain boundary phase grew to 17nm, PFZ began to appear; the grain boundary phase increased to 19nm at 60°C, and obvious PFZ appeared. The size and distribution of precipitated phases have a significant impact on the strength and fracture toughness of the alloy. The grain boundary precipitated phase and grain boundary non-precipitated zone have a significant impact on the fracture toughness of the alloy, especially the coarse grain boundary precipitated phase is easy to become the source of cracks in the process of stress, which is very unfavorable to the fracture toughness of the alloy. In the quenching process after solid solution treatment, the quenching temperature is high, and the precipitation precipitation process of the alloy is more obvious. Compared with low temperature quenching, the size of the quenching precipitation phase produced at the grain boundary during high temperature quenching is coarser, which will significantly weaken the grain boundary. strength and reduce the fracture toughness of the alloy. Therefore, for materials with high fracture toughness requirements, low temperature quenching must be used. Therefore, the conventional forging quenching water temperature of 30° C. to 80° C. cannot be used for the forgings of the present invention.

The 7000 series aluminum alloy is a typical precipitation strengthening alloy and one of the main structural materials in the aerospace industry. After T6 peak aging treatment of 7000 series aluminum alloy, the intragranular precipitated phase is the precipitation of fine GP area and η′ phase. After aging for 24 hours, the size of the precipitated phase is concentrated in 2nm-5nm, and the number of precipitated phases with a unit nanometer size accounts for about 30%. Get the maximum strengthening effect. However, after reaching the peak value, fine semi-coherent dispersed phases are precipitated in the alloy grains, and coarse continuous chain particles are distributed on the grain boundaries. This kind of grain boundary structure is very sensitive to stress corrosion and exfoliation corrosion, and it is difficult to Give full play to its comprehensive performance, and organize photos as shown in Figures 14 and 15. In order to overcome the shortcomings of low corrosion performance and fracture toughness of T6 treatment, solve the contradiction between strength and stress corrosion resistance, and take into account the electrical conductivity and fracture toughness of ring forgings, the invention adopts the traditional semi-continuous casting method to obtain uniform grains Organization, using appropriate forging temperature and process, forging to obtain ring forgings, and adopting three-stage solid solution after machining. The low-temperature quenching process can improve the fracture toughness of the material, and cooperate with the appropriate dual-stage aging process (the microstructure photos after the dual-stage aging treatment are shown in Figures 16 and 17), so that the precipitates distributed on the grain boundaries are intermittently distributed, and the forging resistance can be improved. Corrosion performance, while ensuring that the size and distribution of intragranular precipitates are well controlled, to achieve the ideal matching effect of mechanical properties and fracture toughness, so as to meet the service conditions with higher comprehensive requirements.

Claims (10)

1. The ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight is characterized by comprising the following elements in percentage by mass: 1.6 to 3.0 percent of Mg:1.8 to 2.5 percent of Zn:8.4% -9.7%, zr:0.10 to 0.15 percent of Cr:0.02% -0.04%, ti:0.015 to 0.04 percent and the balance of Al.

2. The preparation method of the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight is characterized by comprising the following steps of:

1. the mass percentage of elements is as follows: 1.6 to 3.0 percent of Mg:1.8 to 2.5 percent of Zn:8.4% -9.7%, zr:0.10 to 0.15 percent of Cr:0.02% -0.04%, ti: weighing an aluminum ingot, cathode copper, a primary magnesium ingot, a zinc ingot, an aluminum zirconium alloy ingot, an aluminum chromium intermediate alloy ingot and an aluminum titanium wire according to the proportion of 0.015% -0.004% and the balance of Al to obtain raw materials, and then smelting the raw materials in a smelting furnace at the smelting temperature of 720-760 ℃ to obtain an aluminum alloy melt;

2. casting the aluminum alloy melt obtained in the step one into a round cast ingot in a semi-continuous casting mode;

3. removing casting oxide skin of the round ingot under the room temperature condition to obtain an aluminum alloy round ingot with the oxide skin removed;

4. preserving heat of the aluminum alloy round ingot with the oxide removed for 12 hours at 420-440 ℃, then preserving heat of the aluminum alloy round ingot for 60 hours at 470 ℃, discharging, and naturally cooling to room temperature to obtain an annealed round ingot;

5. placing the annealed round ingot into a resistance heating furnace, and heating to 400-450 ℃ to obtain a hot forging press ring-shaped forging blank;

6. after the ingot is discharged from the furnace, under the condition that air is naturally cooled to 300-400 ℃ of surface temperature, forging the hot forging annular forging blank obtained in the step five into an annular forging blank by using a forging press, and obtaining the hot forging annular forging blank;

7. carrying out rough machining on the rough material of the hot forging annular forging to obtain rough machined rough material of the annular forging;

8. placing the rough machined annular forging blank into a resistance heating furnace, preserving heat for 2-4 h at 430-460 ℃, raising the temperature to 470 ℃, preserving heat for 4-6 h, raising the temperature to 472-480 ℃ and preserving heat for 1-3 h, then quenching, wherein the water temperature before quenching is less than or equal to 19 ℃, the water temperature after quenching is less than or equal to 21 ℃, and the immersion time of the forging in water is 10-20 min;

9. performing cold compression stress relief treatment on the rough machined annular forging blank processed in the step eight to obtain a rough machined annular forging blank subjected to stress relief;

10. placing the rough machined annular forging blank after stress relief into a resistance heating furnace to be heated to 115-121 ℃, heating to 154-165 ℃ after heat preservation treatment for 6-12 hours, and performing heat preservation treatment for 6-12 hours to obtain an overaging annular forging;

11. and processing the annular forging subjected to overaging treatment according to the finished product size to obtain the finished annular forging.

3. The method for preparing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight, which is characterized in that the aluminum alloy annular forging comprises the following components in percentage by mass: 2.2%, mg:2.2%, zn:9.2%, zr:0.11%, cr:0.02%, ti:0.022 percent of Al and the balance of Al are weighed as raw materials.

4. The method for preparing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, wherein the heating temperature of the round ingot in the fifth step is 430 ℃.

5. The method for manufacturing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, wherein in the sixth step, forging is started under the condition that air is naturally cooled to the surface temperature of 350 ℃ after ingot casting is heated.

6. The method for preparing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, which is characterized by comprising the following forging process in the step six: and (3) according to the diameter-height ratio of 0.40-0.45, repeatedly performing longitudinal compression for three times, performing circumferential deformation and elongation, and finally performing longitudinal compression to be cake-shaped, and performing ring forging after center punching.

7. The method for preparing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight, which is characterized in that in the eighth step, in a resistance heating furnace, the temperature is kept for 2 hours at 450 ℃, the temperature is kept for 5 hours at 470 ℃, the temperature is kept for 1 hour at 475 ℃ and then quenching treatment is carried out, the water temperature before quenching is 16 ℃, the water temperature after quenching is less than or equal to 18 ℃, and the immersion time of the forging in water is 10-20 minutes.

8. The method for manufacturing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, wherein the method is characterized in that compression stress relief treatment is performed through low-temperature quenching in the step nine.

9. The method for manufacturing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, wherein the stress-relieving compression amount in the step nine is controlled to be 1-3%.

10. The method for preparing the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight of claim 2, which is characterized in that in the step ten, the temperature is raised to 162 ℃ after 9h of heat preservation, and the heat preservation is carried out for 11h, so that overaging treatment is carried out.

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