CN117286356A - Preparation method for improving anti-stripping corrosion performance of 7xxx aluminum alloy section - Google Patents
Preparation method for improving anti-stripping corrosion performance of 7xxx aluminum alloy section Download PDFInfo
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- CN117286356A CN117286356A CN202311230991.8A CN202311230991A CN117286356A CN 117286356 A CN117286356 A CN 117286356A CN 202311230991 A CN202311230991 A CN 202311230991A CN 117286356 A CN117286356 A CN 117286356A
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- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 52
- 230000007797 corrosion Effects 0.000 title claims abstract description 40
- 238000005260 corrosion Methods 0.000 title claims abstract description 40
- 238000002360 preparation method Methods 0.000 title claims abstract description 10
- 238000001125 extrusion Methods 0.000 claims abstract description 53
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 44
- 239000000956 alloy Substances 0.000 claims abstract description 44
- 230000003014 reinforcing effect Effects 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 16
- QQHSIRTYSFLSRM-UHFFFAOYSA-N alumanylidynechromium Chemical compound [Al].[Cr] QQHSIRTYSFLSRM-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910018580 Al—Zr Inorganic materials 0.000 claims abstract description 10
- 238000005266 casting Methods 0.000 claims abstract description 10
- 230000002441 reversible effect Effects 0.000 claims abstract description 6
- 238000003756 stirring Methods 0.000 claims description 13
- 238000001953 recrystallisation Methods 0.000 abstract description 13
- 239000000203 mixture Substances 0.000 abstract description 5
- 238000004519 manufacturing process Methods 0.000 abstract description 4
- 239000000463 material Substances 0.000 abstract description 4
- 229910052751 metal Inorganic materials 0.000 abstract description 4
- 239000002184 metal Substances 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 21
- 238000010438 heat treatment Methods 0.000 description 15
- 238000004901 spalling Methods 0.000 description 14
- 230000032683 aging Effects 0.000 description 10
- 239000000243 solution Substances 0.000 description 10
- 238000001816 cooling Methods 0.000 description 9
- 229910052782 aluminium Inorganic materials 0.000 description 6
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 6
- 238000010791 quenching Methods 0.000 description 6
- 230000000171 quenching effect Effects 0.000 description 6
- 238000000265 homogenisation Methods 0.000 description 4
- 239000002245 particle Substances 0.000 description 4
- 230000002829 reductive effect Effects 0.000 description 4
- 235000012438 extruded product Nutrition 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 230000005587 bubbling Effects 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 230000002401 inhibitory effect Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 230000000149 penetrating effect Effects 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000003746 solid phase reaction Methods 0.000 description 2
- 239000006104 solid solution Substances 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 239000002344 surface layer Substances 0.000 description 2
- 229910018569 Al—Zn—Mg—Cu Inorganic materials 0.000 description 1
- 229910000599 Cr alloy Inorganic materials 0.000 description 1
- 229910052691 Erbium Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000005275 alloying Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 239000002932 luster Substances 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000036961 partial effect Effects 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000003303 reheating Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
Classifications
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- 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
- C22C1/03—Making non-ferrous alloys by melting using master alloys
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C23/00—Extruding metal; Impact extrusion
- B21C23/002—Extruding materials of special alloys so far as the composition of the alloy requires or permits special extruding methods of sequences
-
- 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
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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
-
- 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
- C22F1/002—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working by rapid cooling or quenching; cooling agents used therefor
-
- 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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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
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- Metallurgy (AREA)
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- Crystallography & Structural Chemistry (AREA)
- Extrusion Of Metal (AREA)
Abstract
The invention provides a preparation method for improving the anti-stripping corrosion performance of a 7xxx aluminum alloy section, wherein in the casting process, the addition temperature of an Al-Cr intermediate alloy and an Al-Zr intermediate alloy is controlled between 730 ℃ and 750 ℃ and the mixture is fully stirred; in the extrusion process, a reverse extruder is adopted for extrusion, an extrusion hole and a reinforcing hole are arranged on an extrusion die, and the reinforcing hole and the extrusion hole are arranged in the same direction; and (3) arranging reinforcing holes around the extrusion holes according to the region to be reinforced of the profile. The preparation method can ensure that the 7xxx aluminum alloy keeps a metal streamline structure under a large extrusion ratio, does not generate obvious recrystallization, has a smaller grain length-width ratio, ensures that the material can be lifted again to resist peeling corrosion under the premise of excellent tensile strength, can keep good formability, expands the application range of the 7xxx aluminum alloy in the field of aviation, improves the production efficiency of products and saves the cost.
Description
Technical Field
The invention relates to the technical field of aluminum alloy processing, in particular to a preparation method for improving the anti-spalling corrosion performance of a 7xxx aluminum alloy section.
Background
In recent years, the aviation industry has put higher demands on the comprehensive properties of 7xxx series alloys, and materials are required to have excellent corrosion resistance under the premise of high strength; however, the current 7xxx series alloy is easy to generate spalling corrosion under the marine environment, so that the 7xxx series alloy has limited application; to improve the spalling corrosion resistance of 7xxx series alloys, the prior art has been primarily improved with respect to control of the alloying elements and heat treatment processes.
In the patent document of the application number CN201810684710.9 and the theme name of the high-performance and high-spalling-corrosion-resistance aluminum alloy section and the processing technology thereof, the rare earth element La is added to purify the melt on the basis of the 7xxx alloy, so that the inclusion and hydrogen content in the manufacturing process of the aluminum alloy are reduced, the grain refinement is facilitated, and the strength is ensured; and a multi-stage homogenizing annealing process, a multi-stage solid solution treatment process and a multi-stage aging process are adopted to ensure the anti-spalling corrosion performance of the 7xxx alloy.
In the patent document of the preparation method of 7000 series aluminum alloy with 680MPa strength and high anti-spalling corrosion performance, as the application number is CN201810982175.5, the multi-stage homogenization of 400+/-5 ℃ multiplied by 6h+420+/-5 ℃ multiplied by 6h+440+/-5 ℃ multiplied by 6h+460+/-5 ℃ multiplied by 6h, multi-stage solid solution of 450 ℃ multiplied by 2h+460 ℃ multiplied by 2h+470 ℃ multiplied by 2h and double-stage overaging of 121 ℃ multiplied by 5h+153 ℃ multiplied by 16h is adopted to improve the strength of the aluminum alloy and enhance the anti-spalling corrosion performance.
In the patent document of the application number of CN201410099547.1 and the topic name of the technology for double-stage aging of erbium-containing Al-Zn-Mg-Cu alloy with the peeling corrosion resistance, the alloy with the characteristics of Zn7.6wt%, mg3.2wt%, cu0.5wt%, mn0.5wt%, zr0.2wt% and Er0.15wt% is subjected to double-stage overaging treatment of 120 ℃/4h+160 ℃/(8-16) h, so that the alloy has excellent peeling corrosion resistance and high strength and other comprehensive properties.
Research shows that not only alloy components and heat treatment process can influence the spalling corrosion performance, but also the morphology of alloy grains has an important influence on the spalling corrosion performance, and the current domestic research on aviation profiles is still in a starting stage, and the research on how to control the grain length-width ratio of the profile by mainly focusing on regulating and controlling the alloy components and changing the heat treatment process so as to improve the spalling corrosion resistance of the material is lacking.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides the preparation method for improving the anti-stripping corrosion performance of the 7xxx aluminum alloy section, which can ensure that the 7xxx aluminum alloy maintains a metal streamline structure under a large extrusion ratio, does not generate obvious recrystallization, has a smaller grain length-width ratio, ensures that the section can improve the anti-stripping corrosion performance of the material again under the premise of having excellent tensile strength, can maintain good formability, expands the application range of the 7xxx aluminum alloy in the field of aviation, improves the production efficiency of products and saves the cost.
The technical scheme of the invention is as follows:
the preparation method for improving the anti-peeling corrosion performance of the 7xxx aluminum alloy section comprises casting, homogenizing and extruding;
adding an Al-Cr intermediate alloy and an Al-Zr intermediate alloy in the casting process, controlling the adding temperature of the Al-Cr intermediate alloy and the Al-Zr intermediate alloy to be 730-750 ℃, and fully stirring;
the aluminum alloy cast ingot containing Cr is obtained after casting, wherein the alloy element Cr is mostly in a supersaturated state, and Cr undergoes solid phase reaction in the homogenization process to form dispersed particles with chemical composition similar to AlCrMgMn, and the dispersed particles have the effect of pinning grain boundaries, so that recrystallization is inhibited; zr element in the Cr-containing aluminum alloy cast ingot and Al generated in the homogenizing process 3 Zr can prevent the aluminum alloy from recrystallization, so that the aluminum alloy can be prevented from recrystallization when the disperse phase in the aluminum alloy cast ingot is uniformly distributed at high density, and the aluminum alloy section has a streamline structure;
in the extrusion process, a reverse extruder is adopted for extrusion, an extrusion die is matched with the reverse extruder, an extrusion hole and a reinforcing hole are formed in the extrusion die, and the reinforcing hole and the extrusion hole are arranged in the same direction;
according to the region to be reinforced of the profile, reinforcing holes are formed in the periphery of the extrusion holes;
extruding by adopting a reverse extruder, wherein in the extruding process, reinforcing holes are arranged around the extruding holes and are parallel to the region to be reinforced of the profile; the arrangement ensures that the section obtained after extrusion has smaller grain length-width ratio in the reinforcing area close to the reinforcing hole, thereby effectively reducing the peeling corrosion rate of the reinforcing area of the extruded section; for example, a location of the profile is often exposed to corrosive environments during use, and reinforcing holes are positioned proximate the location to reduce the aspect ratio of the grains therein and increase the spalling corrosion resistance therein; for example, the profile side surface is often exposed to a corrosive environment with reinforcing holes parallel to the profile side surface and reinforcing hole widths equal to the profile side surface widths, which serve to reduce the grain aspect ratio of the profile side surface and increase the spalling corrosion resistance thereat.
Preferably, the stirring is carried out twice, the interval between the stirring and the stirring is 20-30 min, and the stirring time is 10-15 min each time.
Preferably, the extrusion orifice shape of the extrusion die includes, but is not limited to, J-shape, I-shape, L-shape, T-shape, and double cross shape; the anti-stripping corrosion performance of the extruded member is improved by adding the reinforcing holes.
Preferably, the 7xxx series aluminum alloys include 7x75, 7x50, 7x55; the alloy structure of the 7xxx aluminum alloy section prepared by the method does not generate obvious recrystallization basically, is a typical streamline structure, and is widened near the reinforcing hole, the aspect ratio of crystal grains is reduced, and the anti-spalling corrosion performance is improved.
Compared with the prior art, the invention has the beneficial effects that:
1. the invention can ensure that the 7xxx alloy maintains the metal streamline structure without obvious recrystallization under the condition that the extrusion ratio is more than 20, and simultaneously has smaller grain length-width ratio, so that the section bar has excellent anti-stripping corrosion performance while ensuring the strength.
2. In the invention, the content of Fe and Si is reduced again on the basis of the 7xxx series alloy, and the final performance of the product is improved from the source.
3. According to the preparation method, after the Al-Cr intermediate alloy and the Al-Zr intermediate alloy are added, the mixture is fully stirred, so that Cr and Zr elements in the prepared 7XXX system cast ingot can be uniformly distributed.
In the prepared 7X75 alloy cast ingot, cr plays a role in inhibiting recrystallization, most of Cr is in a supersaturated state, and solid phase reaction occurs in the homogenization process to form dispersed particles with chemical composition similar to AlCrMgMn, and the dispersed particles have a role in pinning grain boundaries, so that the recrystallization is inhibited; for the 7X50 aluminum alloy and the 7055 aluminum alloy, zr element is used for inhibiting the recrystallized aluminum alloy, and the aluminum alloy is produced in the homogenization processRaw Al 3 Zr may prevent the aluminum alloy from recrystallization. When the disperse phase in the cast ingot is uniformly distributed at high density, the aluminum alloy can be prevented from recrystallization, so that the aluminum alloy profile has a streamline structure.
4. The invention is particularly suitable for use with aircraft structural members such as wing stringers, floor beams, and the like. These include commercial airliners, cargo aircraft, and certain military aircraft. To a lesser extent, the alloys of the present invention are suitable for use in other aircraft including, but not limited to, turboprop aircraft. Furthermore, the invention is applicable to the production or application of any structural member.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the description of the embodiments or the prior art will be briefly described below, and it will be obvious to those skilled in the art that other drawings can be obtained from these drawings without inventive effort.
Fig. 1 is a schematic cross-sectional view of a double cross-shaped extrusion die used in example 1.
Fig. 2 is a schematic cross-sectional view of a T-shaped extrusion die used in example 2.
Fig. 3 is a schematic cross-sectional view of a J-shaped extrusion die used in example 3.
Fig. 4 is a schematic cross-sectional view of a double cross-shaped extrusion die used in comparative example 1.
Fig. 5 is a schematic cross-sectional view of a T-shaped extrusion die used in comparative example 2.
Fig. 6 is a schematic cross-sectional view of a J-shaped extrusion die used in comparative example 3.
FIG. 7 is a schematic diagram showing the change of the morphology of the grains at the strengthening positions before and after the mold improvement.
FIG. 8 is a strengthening position grain morphology of example 2.
FIG. 9 is a graph of the morphology of the reinforced position grains of comparative example 2.
FIG. 10 is a photograph of example 2 after spalling corrosion.
FIG. 11 is a photograph of comparative example 2 after spalling corrosion.
In the figure, 1-body, 2-vertical hole A, 3-vertical hole B, 4-vertical hole C, 5-transverse hole A, 6-reinforcing hole, 7-vertical hole D, 801-horizontal section A, 802-horizontal section B, 901-horizontal section C, 902-horizontal section D, 10-vertical hole E, 11-transverse hole D, 12-reinforcing area.
Detailed Description
In order that those skilled in the art will better understand the technical solutions of the present invention, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the present invention without making any inventive effort, shall fall within the scope of the present invention.
Example 1
For 7175 aluminum alloy section, the alloy components comprise the following components in percentage by mass:
zn 5.8%, mg 2.5%, cu 1.7%, cr 0.2%, mn 0.01%, ti 0.05%, zr 0.0029%, fe 0.09%, si 0.045% and the balance of aluminum, wherein the addition temperature of the Al-Cr and Al-Zr intermediate alloy is 740 ℃, stirring is carried out twice, each stirring time is 14min, and the interval is 23min;
the aluminum alloy is cast in a semi-continuous mode, and the diameter of an ingot is 600mm;
homogenizing: slowly heating the cast ingot for about 9 to 460 ℃, keeping the temperature in the cast ingot for 8 hours, then continuously heating the cast ingot for 1 to 473 ℃, preserving the heat for 24 hours, and cooling the cast ingot to room temperature by air;
cooling the homogenized cast ingot to room temperature by air cooling, sawing the cast ingot into a blank with proper length, and peeling to obtain a cast rod;
extruding: reheating the cast rod to 420 ℃, and then performing backward extrusion on a 150MN extruder, wherein the extrusion ratio is 25.9, and the hole arrangement mode of an extrusion die is shown in figure 1;
referring to fig. 1, the extrusion die comprises a body 1, wherein a double cross extrusion hole is formed in the center of the body 1, and comprises a vertical hole A2, a vertical hole B3 and a vertical hole C4;
the vertical hole A2, the vertical hole B3 and the vertical hole C4 are connected with a transverse hole A5, one end of the transverse hole A5 is communicated with the vertical hole A2, and the other end penetrates through the vertical hole C4 and is positioned outside the vertical hole C4;
the penetrating position of the transverse hole A5 and the vertical hole B3 is communicated, and the penetrating position of the transverse hole A5 and the vertical hole C4 is communicated;
in this embodiment, the reinforcing region 12 of the 7175 aluminum alloy profile is formed by the top of the section of the transverse hole A5 between the vertical hole A2 and the vertical hole B3 by extrusion, and therefore, the reinforcing hole 6 is disposed between the vertical hole A2 and the vertical hole B3, and the reinforcing hole 6 is disposed above the transverse hole A5;
stretching and straightening the extruded section bar at 475 ℃ for 2.5h of solution heat treatment;
after solution heat treatment, spray quenching is carried out on the product; after quenching, pre-stretching the extruded product by 1.5% to form enough strength, relieving internal stress and straightening the product;
and (3) carrying out single-stage aging treatment on the pre-stretched aluminum profile, wherein the aging temperature is 120 ℃, and the heat preservation time is 24 hours, so as to obtain the 7175 aluminum alloy profile.
Example 2
For 7175 aluminum alloy section, the alloy components comprise the following components in percentage by mass:
zn 5.8%, mg 2.9%, cu 1.5%, cr 0.17%, mn 0.12%, ti 0.1%, zr 0.003%, fe 0.09%, si 0.48% and the balance of aluminum, wherein the addition temperature of the Al-Cr and Al-Zr intermediate alloy is 740 ℃, stirring is carried out twice, each stirring time is 13min, and the interval is 25min;
the aluminum alloy is cast in a semi-continuous mode, and the diameter of an ingot is 600mm;
homogenizing: slowly heating the cast ingot for 8 to 460 ℃, keeping the cast ingot for 8 hours, then continuously heating the cast ingot for 1 to 473 ℃, preserving the heat for 24 hours, and cooling the cast ingot to room temperature by air;
cooling the homogenized alloy to room temperature by air cooling, sawing an ingot into blanks with proper length, and peeling to obtain a casting rod;
extruding: the casting rod is reheated to 420 ℃, and then is reversely extruded on a 150MN extruder, the extrusion ratio is 31.3, and the hole arrangement mode of the extrusion die is shown in figure 2;
referring to fig. 2, the extrusion die comprises a body 1, wherein a T-shaped extrusion hole is formed in the center of the body 1, the extrusion hole comprises a vertical hole D7 and a transverse hole B, the middle parts of the vertical hole D7 and the transverse hole B are communicated, the transverse hole B comprises a horizontal section a801 and a horizontal section B802, and the horizontal section a801 and the horizontal section B802 are positioned on two sides of the vertical hole D7;
in the present embodiment, the reinforcing region 12 of the 7175 aluminum alloy profile is extruded from the bottom of the horizontal segment a801, and therefore, the reinforcing hole 6 is provided below the horizontal segment a 801;
stretching and straightening the extruded section bar, and carrying out solution heat treatment for 2.5 hours at the temperature of 477 ℃;
after solution heat treatment, spray quenching is carried out on the product; after quenching, pre-stretching the extruded product by 1.5% to form enough strength, relieving internal stress and straightening the product;
and (3) performing two-stage aging treatment on the pre-stretched aluminum profile, wherein the first-stage aging temperature is 120 ℃, the heat preservation is performed for 12 hours, the second-stage aging temperature is 165 ℃, and the heat preservation is performed for 8 hours, so that the 7175 aluminum alloy profile is obtained.
Example 3
For 7050 aluminum alloy section, the alloy comprises the following components in percentage by mass:
6.3% of Zn, 1.96% of Mg, 2.1% of Cu, 0.0056% of Cr, 0.1% of Mn, 0.05% of Ti, 0.11% of Zr, 0.01% of Fe, 0.043% of Si and the balance of aluminum, wherein the adding temperature of the Al-Cr and Al-Zr intermediate alloy is 750 ℃, and the mixture is stirred for two times for 10min each time at intervals of 30min;
the aluminum alloy is cast in a semi-continuous mode, and the diameter of an ingot is 600mm;
homogenizing: slowly heating the cast ingot for 10 hours to 460 ℃, keeping for 5 hours, then continuously heating for 1 hour to 477 ℃, preserving heat for 24 hours, and cooling to room temperature by air;
cooling the homogenized alloy to room temperature by air cooling, sawing an ingot into blanks with proper length, and peeling to obtain a casting rod;
extruding: the cast rod is reheated to 425 ℃, and then is reversely extruded on a 150MN extruder, the extrusion ratio is 29.5, and the hole arrangement mode of the extrusion die is shown in figure 3;
referring to fig. 3, the extrusion die comprises a body 1, wherein a J-shaped extrusion hole is formed in the center of the body 1, and comprises a transverse hole C, a vertical hole E10 and a transverse hole D11 which are sequentially communicated; wherein the bottom end of the vertical hole E10 is communicated with the middle part of the transverse hole C, and the top end of the vertical hole E10 is communicated with one end part of the transverse hole D11; the transverse hole C comprises a horizontal section C901 and a horizontal section D902, and the horizontal section C901 and the horizontal section D902 are positioned on two sides of the vertical hole E10;
in the present embodiment, the reinforcing region 12 of the 7050 aluminum alloy profile is extruded from the bottom of the horizontal section C901, and therefore, the reinforcing hole 6 is provided below the horizontal section C901;
stretching and straightening the extruded section bar at 475 ℃ for 3h of solution heat treatment;
after solution heat treatment, spray quenching is carried out on the product; after quenching, pre-stretching the extruded product by 1.5% to form enough strength, relieving internal stress and straightening the product;
performing two-stage aging treatment on the pre-stretched aluminum profile, wherein the first-stage aging temperature is 121 ℃ and is kept for 5 hours, and the second-stage aging temperature is 163 ℃ and is kept for 24 hours; and obtaining the 7050 aluminum alloy profile.
Comparative example 1
An aluminum alloy profile differing from example 1 only in that: in comparative example 1, the extrusion die hole pattern was as shown in fig. 4, and no reinforcing holes were provided.
Comparative example 2
An aluminum alloy profile, differing from example 2 in that: the Al-Cr intermediate alloy in comparative example 2 was added at 740℃and stirred for 1 time and 20 minutes; the extrusion die hole arrangement mode is as shown in fig. 5, and reinforcing holes are not formed.
Comparative example 3
An aluminum alloy profile, differing from example 3 in that: in comparative example 3, the extrusion die hole pattern was as shown in fig. 6, and no reinforcing holes were provided.
The grain length, width and direction of the aluminum alloy profiles of examples 1 to 3 and comparative examples 1 to 3 were examined, and the aspect ratio of the grains was calculated, and the results are shown in Table 1 as follows:
table 1 grain aspect ratio of aluminum alloy section
| Numbering device | Alloy | Direction | Length of | Width of (L) | Ratio of |
| Example 1 | 7175 | Long transverse direction | 101.5 | 12.6 | 8.06 |
| Example 2 | 7175 | Long transverse direction | 113.8 | 11.4 | 9.98 |
| Example 3 | 7050 | Long transverse direction | 109.4 | 11.3 | 9.68 |
| Comparative example 1 | 7175 | Long transverse direction | 158.3 | 9.7 | 16.31 |
| Comparative example 2 | 7175 | Long transverse direction | 149.7 | 10.4 | 14.39 |
| Comparative example 3 | 7050 | Long transverse direction | 155.2 | 9.8 | 15.84 |
The mechanical properties and the anti-peeling corrosion properties of the aluminum alloy profiles of examples 1 to 3 and comparative examples 1 to 3 were measured, and the results are shown in Table 2, as follows:
TABLE 2 Performance test results
As can be seen from the comparison of tables 1 and 2, the length-width ratio of long transverse grains of the profile can be reduced by adjusting the stirring mode after adding the intermediate alloy of Al-Cr and Al-Zr and adding the reinforcing holes, the strength is basically kept unchanged, and the anti-stripping corrosion performance is greatly improved.
Fig. 7 shows the change in the morphology of the grains of all examples and comparative examples.
FIGS. 8 and 9 show the morphology of the grains at the same location in the profiles of example 1 and comparative example 1, respectively, wherein the structure of the profile is substantially a streamlined structure without significant recrystallization; the aspect ratio of the grains at the strengthening position in example 1 in combination with table 1 was 8.06, and the aspect ratio of the grains at the same position in comparative example 1 was 16.31; the alloy maintains a streamline structure, and obvious recrystallization does not occur, mainly because the Al-Cr alloy is fully stirred in the casting process, so that AlCrMgMn phases are uniformly distributed in the alloy; the grain aspect ratio of the aluminum alloy profile of example 1 is mainly due to the provision of reinforcing holes in the die, which causes the metal to split during extrusion of the cast rod, resulting in a smaller grain aspect ratio.
FIGS. 10 and 11 are photographs of the same positions of the profiles of example 2 and comparative example 2 after the peeling corrosion, wherein the bubbling appears on the surface of nearly half of the profile of example 2, the peeling occurs in part of the surface layer structure, the peeling corrosion is not serious, the corrosion products are less, and the corrosion grade is EA; the extruded profile of comparative example 2 has obvious peeling corrosion, the surface has no metallic luster, the surface layer tissue has serious bubbling and layering, part of the surface has chalking, a large amount of internal tissues are exposed in the corrosion solution, the partial peeling corrosion in the alloy is accelerated, the corrosion products are more, and the corrosion grade reaches EC.
Although the present invention has been described in detail by way of reference to preferred embodiments, the present invention is not limited thereto. Various equivalent modifications and substitutions may be made in the embodiments of the present invention by those skilled in the art without departing from the spirit and scope of the present invention, and it is intended that all such modifications and substitutions be within the scope of the present invention/be within the scope of the present invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (4)
1. The preparation method for improving the anti-peeling corrosion performance of the 7xxx aluminum alloy section is characterized by comprising casting, homogenizing and extruding;
adding an Al-Cr intermediate alloy and an Al-Zr intermediate alloy in the casting process, controlling the adding temperature of the Al-Cr intermediate alloy and the Al-Zr intermediate alloy to be 730-750 ℃, and fully stirring;
in the extrusion process, a reverse extruder is adopted for extrusion, an extrusion die is matched with the reverse extruder, an extrusion hole and a reinforcing hole are formed in the extrusion die, and the reinforcing hole and the extrusion hole are arranged in the same direction;
and (3) arranging reinforcing holes around the extrusion holes according to the region to be reinforced of the profile.
2. The method for preparing the 7xxx series aluminum alloy section with improved anti-peeling corrosion performance according to claim 1, wherein the stirring is carried out twice at intervals of 20-30 min, and the stirring time is 10-15 min each time.
3. The method of claim 1, wherein the extrusion orifice shape of the extrusion die includes, but is not limited to, J-shape, I-shape, L-shape, T-shape, and double cross shape.
4. The method of claim 1, wherein the 7 xxx-series aluminum alloy includes 7x75, 7x50, and 7x55.
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