CN112976718B

CN112976718B - 1420Al-Li/Mg-9Li/1420Al-Li composite board and preparation method thereof

Info

Publication number: CN112976718B
Application number: CN202110162953.8A
Authority: CN
Inventors: 边丽萍; 吴世松; 张红芳; 梁伟; 赵兴国; 刘涛; 田丰
Original assignee: Taiyuan University of Technology
Current assignee: Taiyuan University of Technology
Priority date: 2021-02-05
Filing date: 2021-02-05
Publication date: 2022-12-02
Anticipated expiration: 2041-02-05
Also published as: CN112976718A

Abstract

The invention discloses a 1420Al-Li/Mg-9Li/1420Al-Li composite board and a preparation method thereof, and relates to the field of metal composite board manufacturing. The preparation method of the composite board comprises the following steps: preparing a single plate, preprocessing, pre-rolling, assembling, hot rolling and annealing. The 1420Al-Li/Mg-9Li/1420Al-Li composite board prepared by the invention has the advantages of ultra-light weight, high strength, corrosion resistance, good plasticity and toughness and the like, solves the problems of low absolute strength, poor corrosion resistance, low plasticity and toughness and the like of the magnesium-lithium alloy, and expands the application range of the magnesium-lithium alloy and the aluminum-lithium alloy in the light weight fields of aerospace, rail transit and the like.

Description

1420Al-Li/Mg-9Li/1420Al-Li composite board and preparation method thereof

Technical Field

The invention relates to the field of metal composite board manufacturing, in particular to a 1420Al-Li/Mg-9Li/1420Al-Li composite board and a preparation method thereof.

Background

The magnesium-lithium alloy is used as an ultra-light structure material, and the density is only 1.4-1.6 g/cm ³ The magnesium alloy has the characteristics of higher specific strength and specific stiffness, better damping shock absorption, electromagnetic shielding and plastic formability and the like compared with the conventional magnesium alloy, and is widely applied to the light weight fields of automobiles, aerospace, 3C and the like. However, the application range of the magnesium-lithium alloy is severely limited by the defects of low absolute strength, poor corrosion resistance and the like of the magnesium-lithium alloy. The existing method for improving the strength and the corrosion resistance of the magnesium-lithium alloy mainly comprises the following steps: alloying, processing deformation, heat treatment, surface modification and aluminum-coated Mg-Li alloy layered composite board. Matsumoto H et Al (Matsumoto H, watanabe S, handa S. Contamination of pure Al/Mg-Li alloy plate and its mechanical properties [ J]Journal of Materials Processing Technology,2005,169 (1): 9-15.) Al/Mg-9.5Li/Al composite panels were prepared by cold rolling with yield strengths up to about 170MPa and no plasticity; the plasticity is improved by annealing above 423K, but the yield strength is sharply reduced to below 138 MPa. Ji P et Al (Ji P, ma X, wu R, et Al. Effect of connecting Temperature on the microscopic and Mechanical Properties of the Al/Mg-8Li-3Al-1Zn/Al Composite Plates Fabricated by Hot Rolling [ J]The Physics of Metals and metallurgical, 2019,120 (5): 447-453) produced by hot rolling and annealing at 400 ℃ 1050Al/Mg-8Li-3Al-1Zn/1050Al composite plates having a tensile strength of about 210MPa and an elongation of 19%. Microstructure and mechanical properties of Ma Xudong (Ma Xudong. Composite rolled and cumulatively laminated Mg-Li/Al composite Panel [ D]2016, harbin engineering university) studied a 1070Al/Mg-8Li-3Al-1Zn/1070Al three-layer plate which, after hot rolling and annealing, had a tensile strength of 204.51MPa and an elongation of 16.39%; after 6 passes of accumulative pack rolling annealing, the tensile strength of the plate is 290.54MPa, the elongation is 7.1 percent, but the edge crack of the plate is serious.

1420 aluminum lithium alloy is one of the lightest commercial aluminum alloys,the density is only 2.47g/cm ³ Has excellent corrosion resistance, welding performance, high elastic modulus and static strength, the method is widely applied in the field of aerospace. However, 1420Al-Li alloy has the problems of anisotropic mechanical property, poor plastic toughness and poor formability.

Disclosure of Invention

The invention aims to provide a 1420Al-Li/Mg-9Li/1420Al-Li composite plate and a preparation method thereof, which aim to solve the problems in the prior art, and the prepared 1420Al-Li/Mg-9Li/1420Al-Li composite plate has the characteristics of high strength, high ductility and toughness and high corrosion resistance.

In order to achieve the purpose, the invention provides the following scheme:

one of the purposes of the invention is to provide a preparation method of a 1420Al-Li/Mg-9Li/1420Al-Li composite plate, which comprises the following steps:

the method comprises the following steps: preparing a single plate: preparing an as-cast 1420Al-Li single plate and an as-cast Mg-9Li single plate;

step two: pretreatment: carrying out solid solution treatment and water quenching on the 1420Al-Li single plate to obtain a pretreated 1420Al-Li single plate;

step three: pre-rolling: heating the pretreated 1420Al-Li single plate in a protective atmosphere, and immediately rolling;

step four: assembling: respectively polishing, cleaning and drying one side plate surface of the pre-rolled 1420Al-Li single plate obtained in the third step and two side plate surfaces of the as-cast Mg-9Li single plate obtained in the first step to obtain a 1420Al-Li single plate and a Mg-9Li single plate with the surfaces treated; stacking 2 single boards of 1420Al-Li and 1 single board of Mg-9Li in sequence of 1420Al-Li/Mg-9Li/1420Al-Li to assemble a blank, enabling the polished surfaces of the single boards of 1420Al-Li and Mg-9Li to be in contact, and tightly coating the composite blank by using aluminum foil; step five: hot rolling: heating the aluminum foil coated composite blank obtained in the fourth step in a protective atmosphere, and immediately rolling to obtain a hot rolled plate;

step six: and (3) annealing treatment: and annealing the hot rolled plate obtained in the fifth step to obtain the 1420Al-Li/Mg-9Li/1420Al-Li composite plate.

Further, the 1420Al-Li component is Al-5Mg-2Li-0.1Zr.

Further, in the first step, the thickness ratio of the 1420Al-Li single plate to the Mg-9Li single plate is 2.

Further, before the solution treatment, the 1420Al-Li single plate in the second step further includes a step of tightly wrapping with aluminum foil and deeply burying in fine graphite powder for compaction; the solution treatment comprises the following steps: putting 1420Al-Li single board wrapped by aluminum foil and deeply buried in fine graphite powder at 200 ℃, heating to 350-400 ℃ at a heating rate of 10 ℃/min, preserving heat for 1.5-2.5 h, and then heating to 420-470 ℃ at a heating rate of 10 ℃/min, preserving heat for 1.5-2.5 h.

Further, the 1420Al-Li single sheet in step three further includes a step of cladding with aluminum foil before hot rolling; the heating temperature is 400-500 ℃, and the heating time is 10-20 min; the rolling is carried out for three times, the reduction of each time is 30-40%, and the total reduction is 75%.

Further, in the fifth step, the heating temperature is 420-470 ℃ and the time is 15min. The rolling is one-time rolling, and the rolling reduction is 50% of that of the composite blank.

Further, the annealing treatment in the sixth step is as follows: and (4) heating the 1420Al-Li/Mg-9Li/1420Al-Li hot-rolled composite plate obtained in the fifth step to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, and cooling the hot-rolled composite plate to room temperature along with the furnace.

Further, the protective atmosphere is an argon atmosphere.

The second purpose of the invention is to provide a 1420Al-Li/Mg-9Li/1420Al-Li composite board prepared by the preparation method.

The invention discloses the following technical effects:

(1) Compared with the traditional aluminum alloy, the 1420Al-Li alloy has the advantages of low density, high specific strength, high specific rigidity and the like, and has the characteristics of light weight and excellent corrosion resistance. The invention adopts 1420Al-Li alloy as the clad plate to be compounded with the magnesium-lithium alloy, thereby solving the technical problems of low absolute strength and poor corrosion resistance of the magnesium-lithium alloy. Meanwhile, the magnesium-lithium alloy is compounded with 1420Al-Li alloy by utilizing the characteristics of ultralight weight, good toughness and plasticity and the like of the magnesium-lithium alloy, so that the technical problem of poor plasticity and toughness of the 1420Al-Li alloy is solved.

(2) Compared with other compounding methods such as friction stir welding, diffusion welding, explosion compounding and the like, the preparation method of the invention adopting rolling compounding has the advantages of simple operation, environmental friendliness, suitability for mass production and the like. The composite material can be compounded through one-time rolling, and the mechanical property is greatly improved. According to the invention, 1420Al-Li alloy is tightly coated with aluminum foil and deeply buried in fine graphite powder for solution treatment, so that the oxidation of a sample in the heating process is effectively prevented; according to the invention, the aluminum foil covers the surface of the composite plate blank, and the composite plate blank is heated and rolled under the argon protective atmosphere, so that the technical problems of surface lithium removal and interface oxidation and difficulty in combination of the magnesium-lithium alloy and the aluminum-lithium alloy in the rolling and compounding process are solved.

(3) According to the invention, after the rolling is finished, the composite plate is annealed, so that the diffusion of alloy elements such as aluminum, magnesium and lithium can be accelerated, the mechanical engagement of the hot-rolled composite plate is converted into metallurgical bonding, and the bonding strength of an interface is obviously improved; meanwhile, a large amount of fine dispersed precipitated phases are precipitated in the Al-Li alloy through annealing to strengthen the alloy, and residual internal stress generated in the alloy in the rolling process is eliminated through recovery and recrystallization, so that the strength, the plastic toughness, the plate quality and the stability of the composite plate are greatly improved. The 1420Al-Li/Mg-9Li/1420Al-Li composite board prepared by the invention has tensile strength up to 338MPa at room temperature, elongation up to 14.7 percent and excellent corrosion resistance, and greatly expands the application range of magnesium-lithium alloy and aluminum-lithium alloy in the fields of automobiles, aerospace and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required in the embodiments will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic rolling diagram of a 1420Al-Li/Mg-9Li/1420Al-Li composite plate of the present invention, wherein a represents a 1420Al-Li single plate, and b represents a Mg-9Li single plate;

FIG. 2 is a gold phase diagram (OM diagram) of each individual plate in the 1420Al-Li/Mg-9Li/1420Al-Li composite plate prepared in example 1, wherein: (a) The metallographic structure diagram of the Mg-9Li side, (b) the metallographic structure diagram of the 1420Al-Li side;

FIG. 3 is a BSEM map of a 1420Al-Li/Mg-9Li/1420Al-Li composite plate prepared in example 1;

FIG. 4 is a graph of tensile stress-strain at room temperature for the 1420Al-Li/Mg-9Li/1420Al-Li composite panel made in example 1.

FIG. 5 is a Tafel plot of 1420Al-Li and as-cast Mg-9Li after the 1420Al-Li and Mg-9Li composite plates prepared in example 1 are peeled apart.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention.

It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In addition, for numerical ranges in the present disclosure, it is understood that each intervening value, to the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

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. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference herein for the purpose of disclosing and describing the methods and/or materials associated with the documents. In case of conflict with any incorporated document, the present specification will control.

It will be apparent to those skilled in the art that various modifications and variations can be made in the specific embodiments of the present disclosure without departing from the scope or spirit of the disclosure. Other embodiments will be apparent to those skilled in the art from consideration of the specification. The specification and examples are exemplary only.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including but not limited to.

Example 1

The method comprises the following steps: smelting 1420Al-Li and Mg-9Li ingots in the protective atmosphere of argon by adopting a common gravity casting method, cutting the 1420Al-Li ingots into veneers with the size of 50 multiplied by 14 multiplied by 4mm, and cutting the Mg-9Li ingots into veneers with the size of 50 multiplied by 14 multiplied by 2 mm;

step two: wrapping 1420Al-Li single board with aluminum foil, burying deeply in fine graphite powder, placing in a box-type resistance furnace at 200 deg.C, heating to 380 deg.C at 10 deg.C/min, maintaining for 2h, heating to 450 deg.C at 10 deg.C/min, maintaining for 2h, performing solid solution treatment, and water quenching;

step three: wrapping an aluminum foil on the surface of 1420Al-Li, placing the aluminum foil in a tube type heating furnace filled with argon at 450 ℃, heating the aluminum foil for 15min, taking out the aluminum foil, rapidly rolling the aluminum foil at the reduction of 30-40%, and repeating the steps for three times to roll 1420Al-Li to the thickness of 1 mm;

step four: polishing the surfaces of the Mg-9Li single plate and the rolled 1420Al-Li single plate by using a stainless steel brush, cleaning the surfaces by using alcohol, and drying the surfaces by using a blower; placing the plate blank with the treated surface in the sequence of 1420Al-Li/Mg-9Li/1420Al-Li to obtain a composite blank, wrapping an aluminum foil on the surface of the composite blank, and fixing the upper end and the lower end of the composite blank by iron wires;

step five: the thickness of the composite blank is about 4mm, the composite blank is put into a tubular heating furnace filled with argon to be heated for 15min at the temperature of 450 ℃, the composite blank is taken out and then is rapidly sent into a rolling mill to be rolled, and the rolling reduction is 50 percent of that of the composite blank;

step six: and putting the obtained hot rolled plate into a tubular furnace at room temperature, heating the hot rolled plate to 200 ℃ along with the furnace at the speed of 10 ℃/min, preserving the heat for 1h, and cooling along with the furnace to obtain the 1420Al-Li/Mg-9Li/1420Al-Li composite plate, wherein the thickness of the composite plate is 2mm.

The 1420Al-Li/Mg-9Li/1420Al-Li composite board is detected, and the detection result is as follows: the tensile strength is 338MPa and the elongation is 14.7 percent at room temperature; the gold phase diagrams of 1420Al-Li single plates and Mg-9Li single plates are shown in FIG. 2; the bonding interface of 1420Al-Li single plate and Mg-9Li single plate is shown in FIG. 3; the stress-strain curve of 1420Al-Li/Mg-9Li/1420Al-Li composite plate is shown in FIG. 4.

Electrochemical corrosion is respectively carried out on 1420Al-Li and as-cast Mg-9Li stripped from the 1420Al-Li/Mg-9Li/1420Al-Li composite plate, and the self-corrosion potential-0.76V of the 1420Al-Li is much higher than that of the Mg-9 Li-1.53V; 1420Al-Li corrosion current density is 0.19 muA far lower than that of Mg-9Li by 5.48 muA; from the corrosion rate, 1420Al-Li is 0.0023mm/a, and is also far lower than 0.1435mm/a of Mg-9 Li; the Tafel plot and the fitting results are shown in FIG. 5 and Table 1.

TABLE 1

Example 2

The method comprises the following steps: smelting 1420Al-Li and Mg-9Li cast ingots in the protective atmosphere of argon by adopting a common gravity casting method, cutting the 1420Al-Li cast ingots into single plates with the size of 50 multiplied by 14 multiplied by 8mm, and cutting the Mg-9Li cast ingots into single plates with the size of 50 multiplied by 14 multiplied by 4 mm;

step two: 1420Al-Li is wrapped by aluminum foil, deeply buried in fine graphite powder, placed in a box-type resistance furnace at 200 ℃, heated to 350 ℃ at a rate of 10 ℃/min, insulated for 1.5h, heated to 420 ℃ at a rate of 10 ℃/min, insulated for 1.5h, subjected to solution treatment, and then water-quenched;

step three: wrapping an aluminum foil on the surface of 1420Al-Li, placing the 1420Al-Li in a tubular heating furnace filled with argon at 400 ℃, heating the 1420Al-Li for 10min, taking out the 1420Al-Li, and rapidly rolling the 1420Al-Li to the thickness of 2mm by rolling the 1420Al-Li at the reduction of 30-40 percent after the heating for 10 min;

step five: the thickness of the composite blank is about 8mm, the composite blank is placed into a tubular heating furnace filled with argon to be heated for 15min at the temperature of 420 ℃, the composite blank is taken out and then is rapidly sent into a rolling mill to be rolled, and the rolling reduction is 50% of that of the composite blank;

step six: and putting the obtained hot rolled plate into a tubular furnace at room temperature, heating the hot rolled plate to 200 ℃ along with the furnace at the speed of 10 ℃/min, preserving the heat for 1h, and cooling along with the furnace to obtain the 1420Al-Li/Mg-9Li/1420Al-Li composite plate, wherein the thickness of the composite plate is 4mm.

The 1420Al-Li/Mg-9Li/1420Al-Li composite board is detected, and the detection result is as follows: the tensile strength is 329MPa and the elongation is 12.3 percent at room temperature; the corrosion resistance was similar to that of example 1.

Example 3

The method comprises the following steps: smelting 1420Al-Li and Mg-9Li ingots in an argon protective atmosphere by adopting a common gravity casting method, cutting the 1420Al-Li ingots into single plates with the size of 50 multiplied by 14 multiplied by 6mm, and cutting the Mg-9Li ingots into single plates with the size of 50 multiplied by 14 multiplied by 3 mm;

step two: wrapping 1420Al-Li single board with aluminum foil, burying deeply into fine graphite powder, placing in a box-type resistance furnace at 200 deg.C, heating to 400 deg.C at 10 deg.C/min, maintaining for 2.5h, heating to 470 deg.C at 10 deg.C/min, maintaining for 2.5h for solution treatment, and water quenching;

step three: wrapping an aluminum foil on the surface of 1420Al-Li, placing the tube-type heating furnace filled with argon at 500 ℃, heating the tube-type heating furnace for 20min, taking out the tube-type heating furnace, rapidly rolling the tube-type heating furnace at the reduction of 30-40%, and repeating the steps for three times to roll 1420Al-Li to the thickness of 1.5 mm;

step five: the thickness of the composite blank is about 6mm, the composite blank is placed into a tubular heating furnace filled with argon gas at 470 ℃ to be heated for 15min, the composite blank is taken out and then is rapidly sent into a rolling mill to be rolled, and the rolling reduction is 50% of that of the composite blank;

step six: and putting the obtained hot rolled plate into a tubular furnace at room temperature, heating the hot rolled plate to 200 ℃ along with the furnace at the speed of 10 ℃/min, preserving the heat for 1h, and cooling along with the furnace to obtain the 1420Al-Li/Mg-9Li/1420Al-Li composite plate, wherein the thickness of the composite plate is 3mm.

The 1420Al-Li/Mg-9Li/1420Al-Li composite board is detected, and the detection result is as follows: the tensile strength is 330MPa and the elongation is 14.5 percent at room temperature; the corrosion resistance was similar to that of example 1.

Comparative example 1

The difference from the embodiment 1 is that the heat preservation time of the 1420Al-Li single board is changed to 380 ℃ heat preservation for 1h and 450 ℃ heat preservation for 1h during the solution treatment.

The 1420Al-Li/Mg-9Li/1420Al-Li composite plate is detected, and the detection result is as follows: the tensile strength is 275MPa and the elongation is 10.5 percent at room temperature.

Comparative example 2

The difference from example 1 is that the heating time of the composite billet in the tubular furnace is 30min.

The 1420Al-Li/Mg-9Li/1420Al-Li composite board is detected, and the detection result is as follows: the tensile strength is 290MPa and the elongation is 11.4 percent at room temperature.

Comparative example 3

The difference from the embodiment 1 is that 1420Al — Li single plate is replaced with pure Al single plate.

The 1420Al-Li/Mg-9Li/1420Al-Li composite plate is detected, and the detection result is as follows: the tensile strength is 200MPa and the elongation is 18 percent at room temperature.

Comparative example 4

The difference from example 1 is that the step of coating with aluminum foil is omitted entirely.

As a result: the surface oxidation of the single plate in the heating process is serious, so that the 1420Al-Li single plate and the Mg-9Li single plate cannot be combined.

Comparative example 5

The difference from example 1 is that the step of annealing in step six is omitted.

The 1420Al-Li/Mg-9Li/1420Al-Li composite plate is detected, and the detection result is as follows: the tensile strength is 278MPa and the elongation is 12.3 percent at room temperature.

Comparative example 6

The difference from example 1 is that the annealing temperature in step seven is 300 ℃.

The 1420Al-Li/Mg-9Li/1420Al-Li composite plate is detected, and the detection result is as follows: the tensile strength is 298MPa and the elongation is 10.7 percent at room temperature.

Comparative example 7

The difference from example 1 is that the annealing time in step seven is 4 hours.

The 1420Al-Li/Mg-9Li/1420Al-Li composite board is detected, and the detection result is as follows: the tensile strength is 274MPa and the elongation is 12.6 percent at room temperature.

Compared with comparative examples 1 and 2, the 1420Al-Li/Mg-9Li/1420Al-Li composite boards prepared in examples 1 to 3 have greatly improved strength and elongation, which indicates that the set temperature and time parameters of the invention are optimal; compared with a comparative example 3, the 1420Al-Li/Mg-9Li/1420Al-Li composite plates prepared in the embodiments 1 to 3 have the advantages that although the elongation is reduced, the strength is greatly improved, and the application range of the magnesium-lithium alloy in the aerospace field is expanded; compared with comparative examples 4 to 7, the 1420Al-Li/Mg-9Li/1420Al-Li composite boards prepared in examples 1 to 3 have greatly improved strength and elongation, because the interface of the composite board is converted from mechanical engagement to metallurgical bonding by the diffusion of the annealing promoting element, so that the interface bonding strength is improved, and the effects of precipitation strengthening, improvement of ductility and toughness and elimination of residual stress are achieved. Too high an annealing temperature can result in brittle intermetallic compounds at the composite interface, causing premature fracture of the material; too long an annealing time may result in growth of precipitated phases, thereby affecting the strength and plasticity of the material.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. A method for preparing a 1420Al-Li/Mg-9Li/1420Al-Li composite plate is characterized by comprising the following steps:

step four: assembling: respectively polishing, cleaning and drying one side plate surface of the pre-rolled 1420Al-Li single plate obtained in the third step and two side plate surfaces of the as-cast Mg-9Li single plate obtained in the first step to obtain a 1420Al-Li single plate and a Mg-9Li single plate with the surfaces treated; stacking 2 1420Al-Li single plates and 1 Mg-9Li single plate in sequence of 1420Al-Li/Mg-9Li/1420Al-Li to assemble, contacting the polished surfaces of the 1420Al-Li and Mg-9Li single plates, and tightly coating the composite blank by using aluminum foil;

step five: hot rolling: heating the aluminum foil coated composite blank obtained in the fourth step under a protective atmosphere, and immediately rolling to obtain a hot rolled plate;

step six: and (3) annealing treatment: annealing the hot rolled plate obtained in the fifth step to obtain a 1420Al-Li/Mg-9Li/1420Al-Li composite plate;

in the second step, the 1420Al-Li veneer also comprises the steps of tightly coating with aluminum foil and deeply burying in fine graphite powder for compaction before the solution treatment; the solid solution treatment comprises the following steps: putting 1420Al-Li single board wrapped by aluminum foil and deeply embedded in fine graphite powder at 200 ℃, heating to 350-400 ℃ at a heating rate of 10 ℃/min, preserving heat for 1.5-2.5 h, then heating to 420-470 ℃ at 10 ℃/min, preserving heat for 1.5-2.5 h;

in the third step, the 1420Al-Li veneer also comprises a step of coating with aluminum foil before hot rolling; the rolling is carried out for three times, the reduction of each time is 30-40%, and the total reduction is 75%;

step five, the rolling is one-time rolling, and the rolling reduction is 50% of that of the composite blank;

the annealing treatment in the sixth step comprises the following steps: and (4) heating the 1420Al-Li/Mg-9Li/1420Al-Li hot-rolled composite plate obtained in the fifth step to 200 ℃ at the speed of 10 ℃/min, preserving heat for 1h, and then cooling the plate to room temperature along with the furnace.

2. A method of manufacturing as claimed in claim 1 wherein the composition of 1420Al-Li is Al-5Mg-2Li-0.1Zr.

3. A method of manufacturing according to claim 1, wherein the thickness ratio of 1420Al-Li single plates to Mg-9Li single plates in step one is 2.

4. A preparation method according to claim 1, wherein the heating temperature in step three is 400-500 ℃ and the heating time is 10-20 min.

5. The preparation method of claim 1, wherein the heating temperature in step five is 420-470 ℃ for 15min.

6. A method of manufacture as claimed in claim 1, wherein the protective atmosphere is an argon atmosphere.

7. The 1420Al-Li/Mg-9Li/1420Al-Li composite panel produced by the method of any one of claims 1 to 6.