CN115747590B - Damage-resistant aluminum lithium alloy and preparation method and application thereof - Google Patents
Damage-resistant aluminum lithium alloy and preparation method and application thereof Download PDFInfo
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- JFBZPFYRPYOZCQ-UHFFFAOYSA-N [Li].[Al] Chemical compound [Li].[Al] JFBZPFYRPYOZCQ-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 229910001148 Al-Li alloy Inorganic materials 0.000 title claims abstract description 64
- 239000001989 lithium alloy Substances 0.000 title claims abstract description 64
- 230000006378 damage Effects 0.000 title claims abstract description 42
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 239000000463 material Substances 0.000 claims abstract description 50
- 239000000956 alloy Substances 0.000 claims abstract description 41
- 229910045601 alloy Inorganic materials 0.000 claims abstract description 37
- 230000032683 aging Effects 0.000 claims abstract description 29
- 238000012545 processing Methods 0.000 claims abstract description 18
- 229910052782 aluminium Inorganic materials 0.000 claims abstract description 9
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000004519 manufacturing process Methods 0.000 claims abstract description 3
- 238000000034 method Methods 0.000 claims description 39
- 238000000265 homogenisation Methods 0.000 claims description 32
- 238000000137 annealing Methods 0.000 claims description 25
- 238000001816 cooling Methods 0.000 claims description 21
- 238000005266 casting Methods 0.000 claims description 15
- 238000005098 hot rolling Methods 0.000 claims description 11
- 238000004321 preservation Methods 0.000 claims description 11
- 238000003723 Smelting Methods 0.000 claims description 10
- 238000005275 alloying Methods 0.000 claims description 10
- 238000007670 refining Methods 0.000 claims description 10
- 239000006104 solid solution Substances 0.000 claims description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 8
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 7
- 229910052748 manganese Inorganic materials 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 7
- 230000008018 melting Effects 0.000 claims description 7
- 238000010791 quenching Methods 0.000 claims description 7
- 230000000171 quenching effect Effects 0.000 claims description 7
- 229910052710 silicon Inorganic materials 0.000 claims description 7
- 239000010703 silicon Substances 0.000 claims description 7
- 238000005097 cold rolling Methods 0.000 claims description 6
- 229910052751 metal Inorganic materials 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 5
- 239000012298 atmosphere Substances 0.000 claims description 4
- 239000002184 metal Substances 0.000 claims description 4
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 238000005096 rolling process Methods 0.000 claims description 3
- 238000005482 strain hardening Methods 0.000 claims description 3
- 229910000838 Al alloy Inorganic materials 0.000 claims description 2
- 229910052802 copper Inorganic materials 0.000 abstract description 5
- 238000010438 heat treatment Methods 0.000 abstract description 4
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000203 mixture Substances 0.000 description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 4
- 230000001276 controlling effect Effects 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000009286 beneficial effect Effects 0.000 description 3
- 238000000465 moulding Methods 0.000 description 3
- 230000001105 regulatory effect Effects 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000005728 strengthening Methods 0.000 description 3
- 230000035882 stress Effects 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 238000013329 compounding Methods 0.000 description 2
- 125000004122 cyclic group Chemical group 0.000 description 2
- 238000007872 degassing Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000004615 ingredient Substances 0.000 description 2
- 239000000155 melt Substances 0.000 description 2
- 239000012768 molten material Substances 0.000 description 2
- 238000001556 precipitation Methods 0.000 description 2
- 230000001681 protective effect Effects 0.000 description 2
- 229910052706 scandium Inorganic materials 0.000 description 2
- 229910018131 Al-Mn Inorganic materials 0.000 description 1
- 229910018461 Al—Mn Inorganic materials 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- 239000012300 argon atmosphere Substances 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 230000001427 coherent effect Effects 0.000 description 1
- OPHUWKNKFYBPDR-UHFFFAOYSA-N copper lithium Chemical compound [Li].[Cu] OPHUWKNKFYBPDR-UHFFFAOYSA-N 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
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- 230000009977 dual effect Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000008832 photodamage Effects 0.000 description 1
- 230000003014 reinforcing effect Effects 0.000 description 1
- 238000010008 shearing Methods 0.000 description 1
- 229910052709 silver Inorganic materials 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 230000001550 time effect Effects 0.000 description 1
- 239000011573 trace mineral Substances 0.000 description 1
- 235000013619 trace mineral Nutrition 0.000 description 1
Abstract
The invention provides a damage-resistant aluminum-lithium alloy material, a preparation method and application thereof, and belongs to the technical field of preparation and processing of aerospace craft structural materials; the aluminum-lithium alloy material comprises, by mass, 1.3-1.8% of Cu, 1.5-1.9% of Li, 0.6-1.0% of Mg, 0.05-0.2% of a first microalloying element and/or 0.05-0.1% of a second microalloying element and aluminum; according to the invention, the damage resistance of the aluminum lithium alloy material is ensured by controlling the contents of Cu, li and Mg elements; meanwhile, microalloying elements are added, so that the cold plastic deformation processability of the aluminum lithium alloy material is further improved, the alloy has a damage-resistant aging heat treatment time window with wider aging state of the aluminum lithium alloy, and the industrial engineering production and application requirements of high damage resistance and strong cold plastic deformation processability of the aluminum lithium alloy material for aerospace at present can be met.
Description
Technical Field
The invention relates to the technical field of preparation and processing of aerospace craft structural materials, in particular to a damage-resistant aluminum-lithium alloy and a preparation method and application thereof.
Background
The aluminum-lithium alloy has the excellent performance attributes of low density, high strength, high specific stiffness, fatigue resistance, corrosion resistance and the like, is considered as a novel damage-resistant light structural material with great development potential, and has wide prospect in the application of the aerospace field. With the continuous technological breakthrough and development of the aerospace field, the demand for reinforcing and reducing the weight of the structural parts of the light damage-resistant large aircraft is increasing. Aluminum lithium alloys are of great interest because of their excellent light weight and high strength properties. The new generation of aluminum-lithium alloy has excellent comprehensive properties, and the workability, particularly cold plastic workability, and the damage resistance performance under the service environment become the key of whether the material can be further used for engineering. Thus, cold workability of damage tolerant aluminum lithium alloys is an important consideration for whether or not they can be made into efficient structural profile industrial manufacturing and equipment. In addition, how to maintain the aging state of the aluminum-lithium alloy and a wider aging time window with excellent damage resistance performance also become the key of whether the alloy can maintain the stability of damage resistance attribute and whether the alloy can be successfully matched with other engineering application fields to pay attention to key performances.
In the traditional low-Cu high-Li aluminum lithium alloy, a large number of dispersed fine delta' particles are repeatedly cut by dislocation to form concentrated and distributed coplanar sliding, dislocation accumulation and entanglement are caused at the grain boundary or the front end of the second phase, and finally, the rheological stress is quickly increased, so that the bearing limit of the material is exceeded without entering a softening stage, and brittle fracture occurs.
Disclosure of Invention
Based on the technical problems in the prior art, one of the purposes of the invention is to provide a preparation method of a damage-resistant aluminum-lithium alloy, wherein the aluminum-lithium alloy comprises specific content of metal elements and aluminum, and is processed by combining a specific method, so that the obtained aluminum-lithium alloy has stronger cold plastic workability and a wide damage-resistant performance aging treatment time window, and can meet the requirements of the processing and use service performance of the aluminum-lithium alloy material for aerospace at present.
In order to achieve the above object, the technical scheme of the present invention is as follows:
The preparation method of the damage-resistant aluminum-lithium alloy material comprises the following elements in percentage by mass:
Cu 1.3～1.8％
Li 1.5～1.9％
Mg 0.6～1.0％
And:
0.05 to 0.2% of a first microalloying element, and/or 0.05 to 0.1% of a second microalloying element;
The content of unavoidable impurities is controlled below 0.05wt%, wherein the content of iron element is controlled below 0.02wt%, and the content of silicon element is controlled below 0.02 wt%; the balance being aluminum.
Wherein the first microalloying element is at least one of Mn, ag, zr, sc; the second micro-alloy element is Ti and/or Ni;
the preparation method of the aluminum lithium alloy comprises the following steps:
S1, proportioning according to the metal element proportion, and sequentially smelting, refining and casting the proportioned raw materials to obtain an ingot;
S2, homogenizing the cast ingot to obtain a homogenized alloy cast ingot;
s3, sequentially carrying out cold and hot processing and temperature control annealing processes on the homogenized alloy cast ingot to obtain a molded blank;
s4, sequentially carrying out solid solution, quenching and aging treatment on the molded blank to obtain the aluminum-lithium alloy material;
In the step S3, the temperature of the annealing process is 400-490 ℃; the heat preservation time is 1.8-3.2 h; the cooling of the annealing process is carried out in at least three stages, specifically:
the temperature of the self-annealing at the first stage is reduced by 80-100 ℃ at a speed of 60-80 ℃/h;
the second stage continuously reduces the temperature from the end temperature of the first stage to 60-80 ℃ at a speed of 65-75 ℃/h;
the third stage is to continuously cool the temperature from the end point temperature of the second stage to 80-90 ℃ and the cooling rate to 60-68 ℃;
And then taking out the blank for air cooling.
In some embodiments, the mass ratio of Cu to Li is 0.9 to 1.8; and/or the mass ratio of Cu to Mg is 1.3-3.0. The stability and the workability of the service strength of the aluminum-lithium alloy material can be further enhanced by controlling the mass ratio of Cu to Mg; the stability of the service strength of the aluminum-lithium alloy material can be further enhanced by controlling the mass ratio of Cu to Li.
In some embodiments, the aluminum lithium alloy material comprises the following components in mass percent:
Cu 1.3～1.8％
Li 1.5～1.9％
Mg 0.6～1.0％
0.05 to 0.2 percent of first microalloying element
0.05 To 0.1 percent of second microalloying element
The content of unavoidable impurities is controlled below 0.05wt%, wherein the content of iron element is controlled below 0.02wt%, and the content of silicon element is controlled below 0.02 wt%; the balance being aluminum.
In the embodiment of any of the above embodiments, the Cu is preferably added in an amount of 1.4 to 1.7% by mass, more preferably 1.5 to 1.6%; the Li addition amount is 1.6 to 1.8%, more preferably 1.7 to 1.8%; the mass ratio of Cu to Li is 1.2-1.6; the mass ratio of Cu to Mg is 1.6-2.6.
In some embodiments, mn is added in an amount of preferably 0.08 to 0.16%, more preferably 0.10 to 0.12% by mass; the Ag addition amount is preferably 0.05 to 0.15%, more preferably 0.08 to 0.12%; the addition amount of Zr is preferably 0.08 to 0.16%, more preferably 0.08 to 0.12%; the addition amount of Sc is preferably 0.08 to 0.16%, more preferably 0.08 to 0.12%; the addition amount of Ti is preferably 0.08-0.10%; the addition amount of Ni is preferably 0.08 to 0.10%.
In some embodiments, the aluminum lithium alloy comprises the following components in mass percent:
Cu 1.3～1.8％
Li 1.5～1.9％
Mg 0.6～1.0％
0.05 to 0.15 percent of first microalloying element
0.05 To 0.08 percent of second microalloying element
The content of unavoidable impurities is controlled below 0.05wt%, wherein the content of iron element is controlled below 0.02wt%, and the content of silicon element is controlled below 0.02 wt%; the balance being aluminum.
In some embodiments, in step S1, the smelting temperature is 680-780 ℃; and/or refining temperature is 690-740 ℃; the first microalloying element and the second microalloying element are added in a master alloy manner; and when the trace alloying element is Ti and/or Ni, the mass of Ti or Ni: the total mass of the intermediate alloy is less than or equal to 10 percent.
In some embodiments, in step S2, the homogenization treatment is a single-stage homogenization treatment or a dual-stage homogenization treatment; when the homogenization treatment is two-stage homogenization treatment, the temperature of the first-stage homogenization treatment is 440-480 ℃ and the treatment time is 8-12 h; the second homogenization treatment is carried out at 500-550 ℃ for 24-36 h; the homogenization treatment process is carried out under an air atmosphere.
In some embodiments, the hot rolling process is started at a temperature of 450-500 ℃ during cold and hot working; the temperature of the blank in the hot rolling process is 350-370 ℃; the deformation of the hot rolling is 30-90%; the cold working adopts room temperature working, and the deformation of the cold rolling is 20-80%.
In some embodiments, in step S4, the solution temperature is 500 to 530 ℃; the aging treatment temperature is 150-180 ℃ and the treatment time is 8-140 h.
The invention also provides the aluminum-lithium alloy material obtained by the preparation method of any embodiment.
The invention also provides application of the aluminum-lithium alloy material as an aerospace structural material.
Compared with the prior art, the invention has the following beneficial effects:
According to the technical scheme, the aluminum-lithium alloy material with strong processability and damage resistance is prepared by adding Cu, li and Mg with specific contents and a specific amount of trace elements into aluminum and combining a specific annealing process, and particularly, the method is beneficial to generating the reasonable volume proportion of three main strengthening phases T1 (Al 2 CuLi), delta 'phase (Al 3 Li) and S' phase (Al 2 CuMg) of the alloy by controlling the contents of the Cu, li and Mg elements, so that the shearing easiness and the coplanar sliding degree of a precipitated phase are influenced. Particularly, the self-healing effect of delta' relative fatigue damage in a longer aging treatment time interval is fully utilized, and the alloy has a wider aging treatment time window to maintain stable and excellent long-term damage resistance on the basis of ensuring the alloy to have damage resistance properties.
In addition, the micro-alloying elements Zr and Sc are easy to form a core-shell structure phase Al3Li (Zr and Sc) which is coherent with the matrix, thereby being beneficial to the alloy having better cold molding processability; the micro alloying elements Ti and Ni are easy to form a dispersed second phase with larger size in alloy crystal and grain boundary, which is favorable for the alloy to have better cold plastic processability; the microalloying elements Mn and Ag are added, and meanwhile, the grain structure characteristic regulation and control of the alloy under the annealing in the cold and hot processing process are effectively regulated and controlled, and the optimal duty ratio of a main precipitated phase delta 'phase (Al 3 Li) and an S' phase (Al 2 CuMg) in a four precipitation strengthening mode is effectively regulated and controlled when the alloy is in an ageing state. The flaky phases such as T 1 or S' obviously improve the coplanar sliding of the alloy, weaken the hardening rate trend of the cyclic stress, promote the alloy to enter the cyclic stress stabilization period, further improve the cold molding processability of the aluminum-lithium alloy, promote the formation of a damage-resistant aging wide time window of the alloy, and can meet the requirements of cold processing and damage-resistant use service performance of the aluminum-lithium alloy material for the current aerospace.
Furthermore, the invention can further enhance the workability of the aluminum lithium alloy and widen the aging treatment time window of the damage-resistant aluminum lithium alloy by controlling the types of the micro-alloying elements, the content of each micro-alloying element and the ratio of Cu to Li mass to Cu to Mg mass and regulating the duty ratio of delta 'phase (Al 3 Li) and S' phase (Al 2 CuMg) in the four precipitation strengthening system modes.
The damage-resistant aluminum-lithium alloy material provided by the invention has strong cold molding processability, wide damage-resistant aging treatment time window, excellent fatigue crack propagation resistance of the aging state alloy in different aging heat treatment processes, and the corresponding da/dn of K=30MPa.m1/2 is 1-2× -3 mm/cycle, so that the requirements of the processing and use service performance of the current aluminum-lithium alloy material for aerospace can be met.
Drawings
FIG. 1 is a graph showing fatigue crack growth curves of samples of the aluminum-lithium alloy obtained in example 7 at a T6 single-stage aging schedule;
FIG. 2 is a graph showing fatigue crack growth curves of samples of the alloy material obtained in example 7 at a T8 single-stage aging regimen;
FIG. 3 is a graph showing fatigue crack growth curves of the alloy material obtained in example 7 when a two-stage aging system is combined.
Detailed Description
In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention. The invention may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit or scope of the invention, which is therefore not limited to the specific embodiments disclosed below.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.
The invention aims to provide a damage-resistant aluminum-lithium alloy material and a preparation method thereof as well as application thereof as an aerospace structural material, wherein the aluminum-lithium alloy material comprises, by mass, 1.3-1.8% of Cu, 1.5-1.9% of Li, 0.6-1.0% of Mg, 0.05-0.2% of a first microalloying element and/or 0.05-0.1% of a second microalloying element and aluminum, the unavoidable impurity content in the alloy material is controlled below 0.05wt%, wherein the iron element content is controlled below 0.02wt% and the silicon element content is controlled below 0.02 wt%; the preparation method of the aluminum lithium alloy comprises the following steps:
S1, proportioning according to the metal element proportion, and sequentially smelting, refining and casting the proportioned raw materials to obtain an ingot;
S2, homogenizing the cast ingot to obtain a homogenized alloy cast ingot;
s3, sequentially carrying out cold and hot processing and temperature control annealing processes on the homogenized alloy cast ingot to obtain a molded blank;
s4, sequentially carrying out solid solution, quenching and aging treatment on the molded blank to obtain the aluminum-lithium alloy material;
In the step S3, the temperature of the annealing process is 400-490 ℃; the heat preservation time is 1.8-3.2 h; the cooling of the annealing process is carried out in at least three stages, specifically:
The temperature is reduced by 80-100 ℃ in the first stage, and the temperature reduction rate is 60-80 ℃/h;
the second stage continuously reduces the temperature from the end temperature of the first stage to 60-80 ℃ at a speed of 65-75 ℃/h;
the third stage is to continuously cool the temperature from the end point temperature of the second stage to 80-90 ℃ and the cooling rate to 60-68 ℃;
And then taking out the blank for air cooling.
Specifically, the preparation method of the aluminum lithium alloy material comprises the following steps:
according to the composition of the damage-resistant aluminum-lithium alloy material, the ingredients are prepared. The present invention is not particularly limited to the process of compounding, and compounding processes well known in the art may be employed.
After the ingredients are prepared, the invention carries out smelting, refining and casting on the matched raw materials to obtain cast ingots. In the present invention, the smelting temperature is preferably 680 to 780 ℃, more preferably 700 to 740 ℃. In the present invention, the smelting is preferably performed under an argon atmosphere. In the present invention, the refining temperature is preferably 690 to 740 ℃, more preferably 700 to 735 ℃. The invention has no special requirements on the smelting, refining and casting processes, and smelting, refining and casting processes well known in the art can be adopted. The micro alloying element is added in a mode of intermediate alloy, wherein the element content of the intermediate alloy of high melting point elements such as Ti, ni and the like is not excessively high, and is controlled to be less than 10 percent, preferably less than 5 percent.
After the ingot is obtained, the ingot is subjected to homogenization treatment to obtain a homogenized alloy ingot. In the present invention, the homogenization treatment is a single-stage homogenization treatment or a double-stage homogenization treatment, preferably a double-stage homogenization treatment. The temperature of the first stage homogenization treatment of the two-stage homogenization heat treatment is preferably 440-480 ℃, more preferably 450-470 ℃; the heat preservation time of the first-stage homogenization treatment is preferably 8 to 12 hours, more preferably 9 to 11 hours; the temperature of the second homogenization treatment is preferably 500 to 550 ℃, more preferably 510 to 520 ℃; the holding time for the second homogenization treatment is preferably 24 to 36 hours, more preferably 28 to 30 hours. In the present invention, the two-stage homogenization treatment is preferably performed under a normal air atmosphere. The homogenization treatment can be utilized to promote the homogenization of chemical components and grain structure distribution in the alloy ingot.
After the homogenized alloy cast ingot is obtained, the homogenized cast ingot is sequentially subjected to cold and hot processing and temperature control annealing processes to obtain a molded blank. In the present invention, the initial rolling temperature of the hot rolling process in the process is preferably 450 to 500 ℃, more preferably 470 to 480 ℃; the temperature of the slab during the hot rolling is preferably 350 to 370 ℃. In the present invention, the deformation amount of the hot rolling is preferably 30 to 90%, more preferably 60 to 80%. Cold working adopts room temperature working, and the deformation of cold rolling is 20-80%; in the invention, the aluminum alloy meets the use requirement through various cold rolling processing deformation.
After cold and hot processing is completed, the obtained alloy is subjected to temperature control annealing process treatment. In the invention, the temperature of the temperature-controlled annealing process is 400-490 ℃, preferably 420-480 ℃, more preferably 440-460 ℃; the heat preservation time is 1.8-3.2 h, preferably 2.0-3.0 h. In the present invention, the cooling mode of the temperature-controlled annealing process preferably includes multi-stage temperature-controlled stage division; the temperature control stage division is preferably three-stage temperature control or more than three-stage temperature control, preferably a three-stage temperature control annealing process treatment mode, the temperature control in the first stage is that the self-annealing temperature is 400-490 ℃ and the temperature is reduced by 80-100 ℃, and the temperature reduction rate in the first stage is preferably 60-80 ℃/h; the temperature control of the second stage is that the temperature is reduced by 60-80 ℃ from the end temperature of the first stage cooling, and the temperature reduction rate of the second stage temperature control is preferably 65-75 ℃/h; the temperature control in the third stage is 80-90 ℃ from the end temperature of the second stage cooling, and the temperature reduction rate of the temperature control in the third stage is preferably 60-68 ℃/h; and then taking out the blank for air cooling. In the present invention, the temperature-controlled annealing process means that the temperature control stage is nonlinear, which is closely related to the formation of different grains by adding microalloying elements and the evolution of the grain structure characteristics of the alloy. The invention can improve the processability and the damage resistance of the aluminum lithium alloy by utilizing the temperature control annealing process.
After the temperature control annealing process is completed, the obtained blank is subjected to cold and hot processing to obtain a molded blank. The invention has no special requirements on the cold and hot processing process, and the forming processing process well known in the field can be adopted. In the invention, the cold and hot processing technology has the function of meeting the actual industrial production and use requirements. Preferably, the cold and hot working treatment can be performed in the above manner.
After the molded blank is obtained, the molded blank is sequentially subjected to solid solution, quenching and aging treatment, so that the damage-resistant aluminum-lithium alloy with strong processability is obtained. In the present invention, the solid solution temperature is preferably 500 to 530 ℃, and the holding time is preferably 1h. After the completion of the solid solution, the present invention preferably subjects the obtained blank to a pre-deformation, and the plastic deformation amount of the pre-deformation is preferably 5 to 8%. The invention can obtain better service performance through pre-deformation. The invention has no special requirement on the quenching process, and adopts the normal-temperature water quenching process which is well known in the field. In the present invention, the temperature of the aging treatment is preferably 150 to 180 ℃, more preferably 150 to 170 ℃; the holding time is preferably 8 to 140 hours, more preferably 10 to 80 hours, and still more preferably 20 to 60 hours.
For a fuller understanding of the present invention, reference should be made to the following detailed description taken in conjunction with the accompanying drawings and preferred embodiments, but the scope of the invention is not limited to the following specific embodiments.
Example 1
The alloy compositions of the damage-resistant aluminum-lithium alloy material are shown in Table 1, specifically Cu 1.5 wt%, li 1.8 wt%, mg 0.8 wt%, mn 0.10 wt%, and unavoidable impurities <0.05 wt%, wherein iron is less than or equal to 0.02wt% and silicon is less than or equal to 0.02wt%; the balance of Al; the Cu/Li mass ratio was 0.83 and the Cu/Mg mass ratio was 1.8.
The preparation method of the aluminum lithium alloy material of the embodiment comprises the following steps:
Batching according to the component compositions of the damage-resistant aluminum-lithium alloy material shown in the table 1, and sequentially smelting, refining and casting the prepared raw materials to obtain an ingot; the specific casting steps are as follows: preheating the molten material, primary feeding, degassing and deslagging, secondary feeding, degassing and deslagging, adding lithium under protective gas, stirring, standing, and draining and pouring. The preheating temperature of the melting stock is 300-400 ℃ and the heat preservation time is 2-3h. In the casting process, the sequence of adding different samples is determined according to the different melting points of different added alloys so as to ensure the sufficient melting of the added molten materials and prevent the loss of casting setting elements. The high-melting-point intermediate alloy such as Al-Mn, al-Zr, al-Sc and the like needs to properly raise the temperature and prolong the melting time of the melt, and the abundant melting time is not less than 0.5h. The casting temperature is 760-780 ℃ and the heat preservation time is 30-40min. The lithium adding process should be performed under the protection of sufficient high-purity argon. The lithium is put into a high-temperature melt by using a special bell jar for adding lithium with special design, and meanwhile, the temperature of a furnace body is kept low, and the temperature is set to be 710-730 ℃. In the adding process, the mutual dissolution time of 5-10min is kept so as to ensure that the Li element is fully melted. Stirring after the addition of lithium is finished, stirring for 3min, keeping at 730-750 ℃ for 12 min, and pouring out the melt. The high-temperature melt of the aluminum-lithium alloy needs to be drained when being used for casting, the casting process needs to be carried out stably, the casting process needs to be kept under the protective atmosphere of high-purity argon, the water flow of a water outlet of a water cooling mould is controlled, and the flow rate is controlled to be 0.1-0.4m/s, so that the ideal cooling effect of casting ingots after heating is achieved.
Performing two-stage homogenization treatment on the obtained cast ingot, wherein the temperature of the first-stage two-stage homogenization treatment is 486 ℃, the heat preservation time is 12h, the temperature of the second-stage homogenization treatment is 520 ℃, and the heat preservation time is 28h, so as to obtain a homogenized cast ingot; the homogenized cast ingot is subjected to hot rolling (the initial rolling temperature is 460 ℃, the temperature of a blank in the hot rolling process is 360-370 ℃, the deformation amount is 80 percent), cold rolling and cold rolling at room temperature, wherein the deformation amount is 80 percent; temperature-controlled annealing (specifically, the annealing temperature is 460 ℃, the heat is preserved for 2.5 hours, then a controllable temperature furnace is used for three-stage temperature-controlled cooling, wherein the first-stage temperature control is that the temperature is reduced from 460 ℃ to 380 ℃ at the cooling rate of 80 ℃/h, the second-stage temperature control is that the temperature is reduced from 380 ℃ to 300 ℃ at the cooling rate of 70 ℃/h, the third-stage temperature control is that the temperature is reduced from 300 ℃ to 180 ℃ at the cooling rate of 65 ℃/h, and when the temperature reaches 180 ℃, a sample is taken out for air cooling) to obtain a molded blank; and (3) carrying out solid solution treatment (the solid solution temperature is 520 ℃, the heat preservation time is 1 h), quenching and aging treatment (the aging temperature is 160 ℃, and the heat preservation time is 24-60 h) on the molded blank in sequence to obtain the damage-resistant aluminum-lithium alloy material.
Examples 2 to 11
Examples 2 to 11 differ from example 1 only in the kinds and contents of the micro-alloying elements added to the aluminum lithium alloy material, and the specific compositions are shown in Table 1.
Comparative example 1
Comparative example 1 differs from example 11 only in the Cu, li content and the absence of added microalloying element (Mn, ag, zr, sc, ti, ni), the specific composition being shown in table 1.
Comparative example 2
Comparative example 2 differs from example 6 only in the Cu, li content and the absence of added microalloying element (Mn, zr, sc, ti, ni), the specific composition being shown in table 1.
Comparative example 3
Comparative example 3 differs from example 11 only in that no microalloying element (Mn, ag, zr, sc, ti, ni) was added, and the specific composition is shown in table 1.
Comparative example 4
Comparative example 4 differs from example 6 only in that no alloying element Mg and no micro-alloying element (Mn, ag, zr, sc, ti, ni) were added, and the specific composition is shown in table 1.
Table 1 composition (wt.%) of the aluminum lithium alloys of examples 1 to 11 and comparative examples 1 to 4
The aluminum-lithium alloy materials obtained in examples 1 to 11 were subjected to a damage resistance test under the condition that the aging system was T-150 ℃ X24 h-6%, and the test results are shown in Table 2.
TABLE 2 results of the damage resistance test of examples 1 to 11 at an aging degree T8 to 150X 120h-6% and an aging state comparative example
As shown in Table 2, the damage-resistant aluminum-lithium alloy material provided by the application has excellent damage resistance through reasonable metal element proportion.
The aluminum lithium alloy material obtained in example 7 was subjected to fatigue crack growth and low cycle fatigue performance test characterization of different processing techniques and heat treated samples, and the results are shown in tables 3,4 and fig. 1 to 3.
Table 3 shows the mechanical properties of example 7 under different time effects
Table 4 shows the mechanical properties of example 7 in different processing, annealing conditions and different directions
In tables 3 and 4, YS represents the yield strength of the material, UTS represents the tensile strength of the material, and Elongation represents the elongation of the material.
As can be seen from tables 3 and 4, the aluminum lithium alloy material obtained by the application has the dual high-quality industrial application essential performances of excellent damage resistance and wide aging time window for keeping the damage resistance property.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the invention, which are described in detail and are not to be construed as limiting the scope of the invention. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the invention, which are all within the scope of the invention. Accordingly, the scope of protection of the present invention is to be determined by the appended claims.
Claims (7)
1. The preparation method of the damage-resistant aluminum-lithium alloy material is characterized by comprising the following elements in percentage by mass:
Cu 1.3~1.8%
Li 1.5~1.9%
Mg 0.6~1.0%
And:
0.05-0.2% of a first microalloying element and 0.05-0.1% of a second microalloying element;
The content of unavoidable impurities is controlled below 0.05wt%, wherein the content of iron element is controlled below 0.02wt%, and the content of silicon element is controlled below 0.02 wt%; the balance of aluminum;
Wherein the first microalloying element is at least one of Mn, ag, zr, sc; the second micro-alloy element is Ti and/or Ni;
the mass ratio of Cu to Li is 0.9-1.8;
The mass ratio of Cu to Mg is 1.3-3.0;
the preparation method of the aluminum lithium alloy material comprises the following steps:
S1, proportioning according to the metal element proportion, and sequentially smelting, refining and casting the proportioned raw materials to obtain an ingot;
S2, homogenizing the cast ingot to obtain a homogenized alloy cast ingot;
s3, sequentially carrying out cold and hot processing and temperature control annealing processes on the homogenized alloy cast ingot to obtain a molded blank;
s4, sequentially carrying out solid solution, quenching and aging treatment on the molded blank to obtain the aluminum-lithium alloy material;
in the step S3, the temperature of the annealing process is 400-490 ℃; the heat preservation time is 1.8-3.2 h; the cooling of the annealing process is carried out in at least three stages, specifically:
The self-annealing temperature in the first stage is reduced by 80-100 ℃, and the temperature reduction rate is 60-80 ℃/h;
the second stage is to continuously cool the temperature of the first stage by 60-80 ℃ from the end temperature of the first stage, wherein the cooling rate is 65-75 ℃/h;
the third stage is to continuously cool the temperature from the end temperature of the second stage by 80-90 ℃ and the cooling rate by 60-68 ℃;
Then taking out the blank for air cooling;
the solid solution temperature is 500-530 ℃; the aging treatment temperature is 150-180 ℃ and the treatment time is 8-140 h.
2. The method for preparing the damage-resistant aluminum-lithium alloy material according to claim 1, wherein the aluminum-lithium alloy comprises the following components in percentage by mass:
Cu 1.3~1.8%
Li 1.5~1.9%
Mg 0.6~1.0%
0.05-0.15% of a first microalloying element
0.05-0.08% Of a second microalloying element
The content of unavoidable impurities is controlled below 0.05wt%, wherein the content of iron element is controlled below 0.02wt%, and the content of silicon element is controlled below 0.02 wt%; the balance being aluminum.
3. The method for preparing a damage-resistant aluminum-lithium alloy material according to any one of claims 1 to 2, wherein in step S1, the melting temperature is 680 to 780 ℃; and/or refining at 690-740 ℃; the first microalloying element and the second microalloying element are added in a master alloy manner; and when the trace alloying element is Ti and/or Ni, the mass of Ti or Ni: the total mass of the intermediate alloy is less than or equal to 10 percent.
4. The method of producing a damage tolerant lithium aluminum alloy material according to any one of claims 1 to 2, wherein in step S2, the homogenization treatment is a single-stage homogenization treatment or a double-stage homogenization treatment; when the homogenization treatment is two-stage homogenization treatment, the temperature of the first-stage homogenization treatment is 440-480 ℃ and the treatment time is 8-12 h; the second-stage homogenization treatment is carried out at 500-550 ℃ for 24-36 hours; the homogenization treatment process is carried out under an air atmosphere.
5. The method for preparing a damage-resistant aluminum-lithium alloy material according to any one of claims 1 to 2, wherein the initial rolling temperature of the hot rolling process is 450-500 ℃ in the cold and hot working process; the temperature of the blank in the hot rolling process is 350-370 ℃; the deformation of the hot rolling is 30-90%; the cold working adopts room temperature working, and the deformation of the cold rolling is 20-80%.
6. An aluminum lithium alloy material obtained by the production method as claimed in any one of claims 1 to 5.
7. Use of the aluminum lithium alloy material as defined in claim 6 as an aerospace structural material.
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