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

Ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and preparation method thereof Download PDF

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CN116179908A
CN116179908A CN202211715283.9A CN202211715283A CN116179908A CN 116179908 A CN116179908 A CN 116179908A CN 202211715283 A CN202211715283 A CN 202211715283A CN 116179908 A CN116179908 A CN 116179908A
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forging
annular forging
aluminum alloy
ingot
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吕丹
丛福官
刘显东
付金来
任伟才
徐磊
高永强
杨道磊
李棠旭
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Northeast Light Alloy Co Ltd
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C21/00—Alloys based on aluminium
    • C22C21/10—Alloys based on aluminium with zinc as the next major constituent
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/002—Hybrid process, e.g. forging following casting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
    • B21J5/02—Die forging; Trimming by making use of special dies ; Punching during forging
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21K—MAKING FORGED OR PRESSED METAL PRODUCTS, e.g. HORSE-SHOES, RIVETS, BOLTS OR WHEELS
    • B21K1/00—Making machine elements
    • B21K1/76—Making machine elements elements not mentioned in one of the preceding groups
    • B21K1/761—Making machine elements elements not mentioned in one of the preceding groups rings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D11/00—Continuous casting of metals, i.e. casting in indefinite lengths
    • B22D11/001—Continuous casting of metals, i.e. casting in indefinite lengths of specific alloys
    • B22D11/003—Aluminium alloys
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23P—METAL-WORKING NOT OTHERWISE PROVIDED FOR; COMBINED OPERATIONS; UNIVERSAL MACHINE TOOLS
    • B23P15/00—Making specific metal objects by operations not covered by a single other subclass or a group in this subclass
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/40—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rings; for bearing races
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C1/00—Making non-ferrous alloys
    • C22C1/02—Making non-ferrous alloys by melting
    • C22C1/026—Alloys based on aluminium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
    • C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
    • C22F1/04—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon
    • C22F1/053—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of aluminium or alloys based thereon of alloys with zinc as the next major constituent

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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

Ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and preparation method thereof
Technical Field
The invention relates to a superstrong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and a preparation method thereof.
Background
With the rapid development of aerospace industry in China, more severe requirements are put forward on basic materials. While the increase in the diameter and wall thickness dimensions of the forged annular forging is required, the performance of the forged annular forging is required to have higher toughness and corrosion resistance matching. The tensile strength is more than or equal to 600MPa, the yield strength is more than or equal to 570MPa, the elongation is more than or equal to 8%, and the fracture toughness is more than or equal to 27 KIC/MPa.m 1/2 The conductivity is more than or equal to 37 percent IACS, the peeling corrosion is performed on the annular forging with the maximum wall thickness of 115mm and the maximum diameter of 1500mm above the EB level, and the stabilized production process is formed. The existing aluminum alloy annular forging product is influenced by a deformation mode, the strength and the toughness are lower than those of extrusion materials made of the same material, and the tensile strength is 500MPa and the toughness are both higherIs lower than 25 KIC/MPa.m 1/2 The requirements of aerospace users on forging materials can not be met, better alloy component combination process control is needed, and comprehensive improvement of the performance of the annular forging product and coordination and matching of multiple performances such as strength, toughness, corrosion resistance and conductivity are achieved.
Disclosure of Invention
The invention aims to solve the problems that the existing aluminum alloy annular forging is low in performance and cannot meet the development needs of the aerospace industry, comprehensively improves the performance of annular forging products and realizes the coordination and matching of multiple performances such as strength, toughness, corrosion resistance and conductivity on the aspects of alloy proportion and process research, and provides a superstrong high-toughness corrosion-resistant aluminum alloy annular forging for aerospace and a preparation method thereof.
The invention relates to a superstrong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight, which comprises 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.
The preparation method of the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight comprises the following steps:
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.
According to the invention, through alloy component optimization, casting quality control, three-stage solid solution, low-temperature water quenching, cold compression control and two-stage aging, an aluminum alloy annular forging with high tensile strength, good fracture toughness and excellent corrosion resistance is produced, and the longitudinal tensile strength of the annular forging manufactured by the method is 612N/mm according to GB/T228 test 2 ～635N/mm 2 Non-proportional elongation strength 595N/mm is specified 2 ～619N/mm 2 The elongation after break is 9.2 to 12.3 percent; the fracture toughness of the annular forging is 27.78MPa m according to GB/T4161 test 1/2 ～33.73MPa·m 1/2 Conductivity was tested according to GB/T12966-2008 for 37.23% IACS to 37.68% IACS, and for the flaking-corrosion EB scale according to HB 5455.
Drawings
FIG. 1 is a schematic diagram of a forging process in step six of the present invention;
FIG. 2 is an as-cast low magnification metallographic photograph of the round ingot of example 2;
FIG. 3 is a photograph of a round ingot as-cast high magnification metallographic image of example 2;
FIG. 4 is a low-magnification SEM photograph of a round ingot after homogenizing annealing of example 2;
FIG. 5 is a high-magnification SEM photograph of a round ingot after homogenizing annealing in example 2;
FIG. 6 is a low-power diagram of the metallographic structure of the annular forging blank of the embodiment 2;
FIG. 7 is a high-power diagram of the metallographic structure of the annular forging blank of the embodiment 2;
FIG. 8 is a low-magnification SEM photograph of a ring forging blank of example 2;
FIG. 9 is a high-magnification SEM photograph of a ring forging blank of example 2;
FIG. 10 is a low-magnification SEM photograph of a ring forging after three-stage solid solution of example 2;
FIG. 11 is a high-magnification SEM photograph of a ring forging after three-stage solid solution of example 2;
FIG. 12 is a TEM image of solid solution tissue at different deformation temperatures;
FIG. 13 shows the TEM structure of the forging after quenching at different water temperatures;
FIG. 14 is a TEM photograph of the intragranular after the T6 peak aging;
FIG. 15 is a TEM photograph of grain boundaries after aging of the T6 peak;
FIG. 16 is an intra-crystal TEM photograph of a ring forging after a two-stage aging treatment;
FIG. 17 is a grain boundary TEM photograph of an annular forging after double stage aging treatment.
Detailed Description
The technical scheme of the invention is not limited to the specific embodiments listed below, but also includes any combination of the specific embodiments.
The first embodiment is as follows: the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight is formed by 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.
The second embodiment is as follows: the preparation method of the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight in the embodiment comprises 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.
And a third specific embodiment: this embodiment differs from the first or second embodiment in that: the aluminum alloy annular forging comprises the following elements 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. The other embodiments are the same as those of the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one of the first to third embodiments in that: in the fifth step, the heating temperature of the round ingot is 430 ℃. The other is the same as in one of the first to third embodiments.
Fifth embodiment: this embodiment differs from one to four embodiments in that: and step six, forging is started under the condition that the air is naturally cooled to the surface temperature of 350 ℃ after the ingot is heated. The others are the same as in one to one fourth embodiments.
Specific embodiment six: this embodiment differs from one of the first to fifth embodiments in that: the forging process of the step six is as follows: 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. The other is the same as in one of the first to fifth embodiments.
Seventh embodiment: this embodiment differs from one of the first to sixth embodiments in that: in the eighth step, the temperature is kept for 2 hours at 450 ℃ in a resistance heating furnace, the temperature is raised to 470 ℃ and kept for 5 hours, then the temperature is raised to 475 ℃ and kept for 1 hour, 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. The others are the same as in one of the first to sixth embodiments.
Eighth embodiment: this embodiment differs from one of the first to seventh embodiments in that: and step nine, carrying out compression stress relief treatment through low-temperature quenching. The other is the same as in one of the first to seventh embodiments.
Detailed description nine: this embodiment differs from one to eight of the embodiments in that: the stress-relieving compression amount in the step nine is controlled to be 1-3%. The others are the same as in one to eight embodiments.
Detailed description ten: this embodiment differs from one of the embodiments one to nine in that: the stress-relieving compression amount in the step nine is controlled to be 2%. The other is the same as in one of the embodiments one to nine.
Eleventh embodiment: this embodiment differs from one to ten embodiments in that: and in the tenth step, heating to 118 ℃, preserving heat for 9 hours, then heating to 162 ℃, preserving heat for 11 hours, and performing overaging treatment. The others are the same as in one to one tenth embodiments.
The following examples are used to verify the benefits of the present invention:
the preparation method of the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight comprises the following steps of:
1. the mass percentage of elements is as follows: 2.4%, mg:2.3%, zn:9.4%, zr:0.14%, cr:0.03%, ti: weighing 0.027% of aluminum ingot, cathode copper, primary magnesium ingot, zinc ingot, aluminum zirconium alloy ingot, aluminum chromium intermediate alloy ingot and aluminum titanium wire which are taken as raw materials according to the proportion of the balance Al, and smelting the raw materials in a smelting furnace to obtain 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 the temperature of 440 ℃, then preserving heat of the aluminum alloy round ingot for 60 hours at the temperature of 470 ℃, discharging, and naturally cooling to room temperature to obtain an annealed round ingot;
5. placing the annealed round ingot into an induction heating furnace, and heating to 435 ℃ to obtain a hot forging annular forging blank;
6. after the ingot is discharged from the furnace, under the condition that air is naturally cooled to the surface temperature of 352 ℃, 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 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 hours at 450 ℃, raising the temperature to 470 ℃, preserving heat for 5 hours, raising the temperature to 473 ℃ and preserving heat for 2 hours, then quenching, wherein the water temperature before quenching is 15 ℃, the water temperature after quenching is 17 ℃, and the immersion time of the forging in water is 15 minutes;
9. and (3) carrying out cold compression stress relief treatment on the rough machined annular forging blank processed in the step (eight), so as to obtain the rough machined annular forging blank subjected to stress relief, wherein the stress relief cold compression quantity is controlled to be 2%, and the purposes of improving the fracture toughness of the annular forging and effectively reducing the residual stress of the annular forging are achieved through low-temperature quenching and cold compression stress relief treatment.
10. Placing the rough machined annular forging blank after stress removal into a resistance heating furnace to be heated to 118 ℃, carrying out heat preservation treatment for 8 hours, then heating to 157 ℃, carrying out heat preservation treatment for 12 hours, and obtaining an overaging annular forging;
11. and (3) accurately machining the annular forging subjected to the overaging treatment according to the finished product size to obtain the finished annular forging.
In this embodiment, as shown in fig. 1, the forging process in step six is repeated three times to perform longitudinal compression according to the diameter-height ratio of 0.40-0.45, circumferential deformation and elongation, and finally longitudinal compression to cake shape, and ring forging is performed after center punching.
According to the embodiment, the ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging is produced by alloy component optimization, ingot quality control, multistage homogenization treatment technology, forging forming technology and toughening heat treatment technology, and the annular forging manufactured by the embodiment has longitudinal tensile strength of 618-635N/mm according to GB/T228 test 2 Specifying the non-proportional elongation strength 601-619N/mm 2 The elongation after break is 9.5-12.3%; the fracture toughness of the annular forging piece is 29.14-33.73 MPa m according to GB/T4161 test 1/2 Conductivity 37.35-37.68% IACS was tested according to GB/T12966-2008 and spalling corrosion EB grade was tested according to HB 5455.
Example 2, an industrialized preparation method of a superstrong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight is carried out according to the following steps:
1. the mass percentage of elements is as follows: 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, and then the raw materials are smelted in a smelting furnace at 760 ℃ for 6 hours to obtain 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 430 ℃, 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 an induction heating furnace, and heating to 430 ℃ to obtain a hot forging annular forging blank;
6. after the ingot is discharged from the furnace, forging the hot forging annular forging blank obtained in the step five into an annular forging blank under the condition that air is naturally cooled to the surface temperature of 350 ℃ to obtain the 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 hours at 450 ℃, raising the temperature to 470 ℃, preserving heat for 5 hours, raising the temperature to 475 ℃ and preserving heat for 1 hour, then quenching, wherein 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 15 minutes;
9. carrying out 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, wherein the stress relief compression amount is controlled to be 1.5%;
10. placing the rough machined annular forging blank after stress removal into a resistance heating furnace for heating to 118 ℃, preserving heat for 9 hours, then heating to 162 ℃, and preserving heat for 11 hours to obtain an overaging annular forging;
11. and (3) accurately machining the annular forging subjected to the overaging treatment according to the finished product size to obtain the finished annular forging.
In the embodiment, the forging process in step six is to repeatedly perform longitudinal compression for three times according to the diameter-height ratio of 0.40-0.45, circumferentially deform and stretch, and finally perform longitudinal compression to be cake-shaped, and perform ring forging after center punching.
The annular forging manufactured in the embodiment has the longitudinal tensile strength of 612N/mm according to GB/T228 test 2 ～624N/mm 2 Non-proportional elongation strength 595N/mm is specified 2 ～610N/mm 2 The elongation after break is 9.2 to 12.0 percent; the fracture toughness of the annular forging is 27.78MPa m according to GB/T4161 test 1/2 ～31.92MPa·m 1/2 Conductivity 37.23-37.45% IACS was tested according to GB/T12966-2008 and spalling corrosion EB grade was tested according to HB 5455.
As shown in FIGS. 2 and 3, the cast structure of the aluminum alloy is a typical dendrite structure, and coarse primary solidification precipitation phases segregate at grain boundaries, and a large amount of fine grains exist in the grain boundariesThe high-power structure photo shows that obvious lamellar structure exists at the crystal boundary, the AlZnMgCu quaternary phase and alpha (Al) phase formed in the solidification process form continuous network lamellar eutectic structure distributed crystal boundary, and the second phase with small size precipitated along the crystal boundary in the matrix is MgZn 2 And (3) phase (C). The grain size is uniform as a whole.
The 7000 series alloy homogenization treatment aims to promote the dissolution back of coarse primary solidification precipitation phases and further promote Al at high temperature 3 The Zr particles are dispersed and separated out, and the phase can pin grain boundaries in the subsequent deformation processing and heat treatment processes, inhibit recrystallization and improve alloy performance. Al (Al) 3 The temperature range with higher Zr nucleation rate is 420-450 ℃. Therefore in order to give consideration to Al 3 The dispersion precipitation of Zr particles and the dissolution back of primary solidification phase are carried out, after the first-stage homogenization annealing treatment of heat preservation for 12h at 420-440 ℃, the high-temperature treatment of heat preservation for 60h at 470 ℃ is carried out, and the furnace is taken out and naturally cooled to room temperature. As shown in fig. 4 and 5, SEM pictures of round ingots after homogenization treatment show that precipitated phases in the tissues after homogenization treatment are fully dissolved, the lamellar eutectic structure of the as-cast alloy completely disappears and only a scattered white phase remains, and energy spectrum analysis shows that the alloy is an Fe-rich phase, the quantity and distribution of the Fe-rich phase are not obviously changed along with the extension of homogenization time, and the grain size of the alloy is not obviously changed after homogenization treatment.
Metallographic structure observation is carried out on the longitudinal section of the blank of the aluminum alloy annular forging (figures 6 and 7). It can be found that the metallographic structure has obvious streamline characteristics, and Mg (Zn, cu, al) with dense distribution and small size exists in the alloy 2 Phases, while Fe-containing phases are observed. SEM pictures of aluminum alloy annular forging burrs (fig. 8 and 9) show that most of the residual phases are Mg (Zn, cu, al) 2 phases, and are distributed in a fine crushing manner along the deformation direction, and only contain a small amount of Fe-containing phases.
The three-stage quenching process is adopted, the solid solution temperature of the first stage is lower, more deformation energy storage can be released, the recrystallization driving force of high-temperature solid solution treatment is reduced, the annular forging piece keeps a higher proportion of deformed structure, the second stage adopts higher-temperature treatment, most of the alloy second phase is ensured to be redissolved to the matrix, and the method is carried outAnd the overburning temperature of the high material is high, the short-time treatment close to the overburning temperature is selected for the third-stage treatment, the second phase dissolution is ensured to the maximum extent, and the maximum space is provided for the strength and toughness matching of the alloy. As can be seen from fig. 10 and 11, after three-stage solution treatment, the second phase is sufficiently dissolved back, and only a small amount of Fe-rich second phase remains, and the size is relatively small. FIG. 12 is a TEM image of solid solution tissue at different deformation temperatures; wherein b, d is 320 ℃ and a, c is 400 ℃. After solution treatment, mgZn in deformed tissue 2 The phases dissolve back and the dislocation disappears, forming a clear flat subgrain boundary, as indicated by the white arrows in (a) and (b). In addition, nano-scale Al was found in solid solution structure 3 Zr phase, al in 7xxx series aluminum alloy, as indicated by arrow (c) (d) Bai Xuxian 3 Zr phase is precipitated in the homogenization heat treatment process, and has pinning and dragging effects on dislocation and grain boundary in the deformation treatment and the solution treatment, thereby playing roles in inhibiting recrystallization and grain growth.
The control of the quenching water temperature of the annular forging is a key point for improving the fracture toughness of the annular forging, and TEM photo pairs such as FIG. 13 of the alloy are obtained after quenching at different water temperatures; wherein a is 20 ℃, b is 40 ℃, and c is 60 ℃; as can be seen, the size of the desolventized phase gradually increases as the quench cooling temperature increases. After quenching at 20 ℃ water temperature, the size of a grain boundary precipitated phase is only 8nm, the size of a grain boundary desolventized phase is obviously smaller than that of other samples, and PFZ does not exist at the grain boundary position; the grain boundary phase grows to 17nm at 40 ℃ and starts to appear PFZ; the grain boundary phase increases to 19nm at 60℃and a significant PFZ appears. The size and distribution of the precipitated phases have a significant impact on the strength and fracture toughness of the alloy. The grain boundary precipitation phase and the grain boundary non-precipitation zone have obvious influence on the fracture toughness of the alloy, and particularly, the coarse grain boundary precipitation phase is easy to become a crack source in the stress process, and is quite unfavorable for the fracture toughness of the alloy. In the quenching process after solution treatment, the quenching temperature is high, the precipitation and precipitation process of the alloy is obvious, compared with low-temperature quenching, the quenching and precipitation phase size generated at the grain boundary in the high-temperature quenching is coarser, the grain boundary strength can be obviously weakened, and the fracture toughness of the alloy is reduced. Therefore, for materials with higher fracture toughness requirements, a low temperature quench must be employed. Therefore, the forging cannot adopt the conventional forging quenching water temperature of 30-80 ℃.
7000 series aluminum alloys are typical precipitation strengthening alloys, one of the main structural materials of the aerospace industry. After the 7000 series aluminum alloy T6 peak aging treatment, the intra-crystal precipitated phase is precipitated as a fine GP zone and eta' phase, after aging for 24 hours, the size of the precipitated phase is concentrated to 2 nm-5 nm, and the number of the precipitated phases in unit nanometer size is about 30%, so that the maximum strengthening effect is obtained. However, after the peak is reached, fine semi-coherent dispersed phase is precipitated in the alloy crystal, coarse continuous chain-like particles are distributed in the crystal boundary, the crystal boundary structure is very sensitive to stress corrosion and peeling corrosion, and the comprehensive performance is difficult to develop in practical application, and the structure photographs are shown in fig. 14 and 15. In order to overcome the defects of low corrosion performance and fracture toughness of T6 treatment, solve the contradiction between strength and stress corrosion resistance, and simultaneously give consideration to the conductivity and fracture toughness of the annular forging, the invention adopts a traditional semi-continuous casting mode to obtain a uniform grain structure, adopts proper forging temperature and process, forges the annular forging, and adopts three-stage solid solution after machining. The low-temperature cold quenching process improves the fracture toughness of the material, and is matched with a proper double-stage aging process (the tissue photographs after double-stage aging treatment are shown in figures 16 and 17), so that the precipitated phases distributed on the grain boundary are intermittently distributed, the corrosion resistance of the forging piece is improved, the size and the distribution state of the precipitated phases in the crystal are well controlled, and the ideal matching effect of the mechanical property and the fracture toughness is achieved, so that the service condition with higher comprehensive requirements is met.

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.
CN202211715283.9A 2022-12-29 2022-12-29 Ultra-strong high-toughness corrosion-resistant aluminum alloy annular forging for spaceflight and preparation method thereof Pending CN116179908A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117949450A (en) * 2024-03-26 2024-04-30 有研工程技术研究院有限公司 Method for evaluating homogenization effect of 6xxx series aluminum alloy cast ingot

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117949450A (en) * 2024-03-26 2024-04-30 有研工程技术研究院有限公司 Method for evaluating homogenization effect of 6xxx series aluminum alloy cast ingot

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