High-strength and high-toughness aluminum-lithium alloy as well as preparation method and application thereof

Abstract

The invention discloses a high-strength and high-toughness aluminum lithium alloy and a preparation method and application thereof, and belongs to the technical field of aluminum lithium alloy material preparation and thermomechanical treatment thereof. The obdurability of the low-Cu / Li-ratio aluminum-lithium alloy is improved through cooperation of hot rolling deformation, solid solution and aging treatment, alpha-Al and Al2Cu eutectic phases at the grain boundary are crushed and partially re-dissolved into a matrix mainly through large-deformation rolling, the grain boundary weakening effect of the alpha-Al and Al2Cu eutectic phases on the alloy is reduced, micron-sized Cu-rich phases and Er-rich phases are eliminated through solid solution treatment, the plasticity of the alloy is improved, and the mechanical property of the alloy is improved. And meanwhile, lattice distortion of the aluminum-lithium alloy is increased, and driving force is provided for subsequent aging precipitation. And a large number of dispersively distributed nanoscale Al3Li phases and core-shell structure phases are separated out in the subsequent aging treatment process, so that the strength of the aluminum-lithium alloy is further improved, and the aluminum-lithium alloy with the low Cu / Li ratio obtains excellent strength and plasticity.

Description

Technical Field

[0001] The invention relates to a high-strength and high-toughness aluminum-lithium alloy and a preparation method and application thereof, belonging to the technical field of aluminum-lithium alloy material preparation and deformation heat treatment thereof. Background Art

[0002] Lithium is the metal element with the lowest density in nature. Its density is about 1 / 5 of aluminum. When 1wt.% of Li is added to aluminum alloy, the alloy density decreases by 3% and the elastic modulus increases by 6%. Lithium can not only reduce the weight of aluminum alloy, but also precipitate Al3Li precipitation strengthening phase in the subsequent aging process to achieve good hardening effect.

[0003] In recent years, aluminum-lithium alloys have replaced traditional aluminum alloys in many aspects and become alloys with greater development potential due to their combination of low density, high elastic modulus, high specific strength, high fracture toughness, good corrosion resistance and high and low temperature performance. Widely used in the aerospace field, they can reduce the weight of parts by 10% to 15% and save fuel consumption. The fuselage skin, long stringers, floor beams, seat slides, boundary beams, cabin floor support columns and other parts of the domestic C919 large passenger aircraft all use the third-generation aluminum-lithium alloy. The use of aluminum-lithium alloy accounts for 7.4% of the weight of the fuselage structure, reducing the overall weight of the aircraft by 7%.

[0004] Strength and plasticity are important indicators for the application of aluminum-lithium alloys. After several generations of development, the third-generation high Cu / Li ratio aluminum-lithium alloys are widely used in the aerospace field due to their good strength and toughness. However, compared with low Cu / Li ratio aluminum-lithium alloys, their weight reduction effect is not good, fuel consumption is increased, and flight costs are increased. Therefore, the preparation of low Cu / Li ratio high-strength and high-toughness aluminum-lithium alloys is a problem that needs to be overcome at present. Deformation heat treatment is an effective way to prepare high-strength and high-toughness aluminum-lithium alloys. And this process does not require high equipment, is simple and easy to operate, and is more suitable for industrial production. Therefore, it is very necessary to provide a deformation heat treatment method that can improve the strength and toughness of low Cu / Li ratio aluminum-lithium alloys. Summary of the invention

[0005] The present invention aims to solve the above technical problems existing in the existing aluminum-lithium alloys, improve the strength and toughness of the aluminum-lithium alloy with a low Cu / Li ratio by thermomechanical treatment, and provide a high-strength and high-toughness aluminum-lithium alloy and its preparation method and application.

[0006] The technical solution of the present invention:

[0007] One of the purposes of the present invention is to provide a high-strength and high-toughness aluminum-lithium alloy, which is composed of the following components in mass percentage: 0.8% to 1.2% Cu, 2.8% to 3.5% Li, 0.3% to 0.5% Mg, 0.08% to 0.15% Zr, 0.08% to 0.15% Er, and the balance is Al.

[0008] It is further defined that the aluminum-lithium alloy is obtained by smelting and casting aluminum ingots, Mg, metallic lithium, intermediate alloys Al-50wt.% Cu, Al-10wt.% Er and Al-10wt.% Zr as raw materials to obtain a cast alloy, and then undergoing homogenization annealing, hot rolling, solid solution and aging treatment.

[0009] The second object of the present invention is to provide a method for preparing the above-mentioned high-strength and high-toughness aluminum-lithium alloy, the method comprising the following steps:

[0010] (1) melting and casting to obtain a cast AlLiCuMgErZr alloy;

[0011] (2) The cast AlLiCuMgErZr alloy is subjected to homogenization annealing, hot rolling, solid solution and aging treatment to obtain a high-strength and high-toughness aluminum-lithium alloy.

[0012] It is further defined that the smelting temperature in (1) is 720-780°C.

[0013] It is further defined that the homogenization annealing temperature in (2) is 480-520° C. and the time is 16-32 h.

[0014] It is further defined that the hot rolling treatment temperature in (2) is 475-525°C and the cumulative deformation is 90%.

[0015] It is further defined that the solution treatment temperature in (2) is 550-580°C and the time is 3-5h.

[0016] It is further defined that the aging treatment temperature in (2) is 180-210°C and the time is 0-10h.

[0017] It is further defined that the aging treatment time in (2) is 7 h.

[0018] The third object of the present invention is to provide an application of the above-mentioned high-strength and high-toughness aluminum-lithium alloy, specifically as a lightweight, high-strength and high-toughness aluminum-lithium alloy.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention improves the toughness of the low Cu / Li ratio aluminum-lithium alloy by hot rolling deformation, solid solution and aging treatment. The large deformation rolling is mainly used to crush the α-Al and Al2Cu eutectic phases at the grain boundary, partially dissolve back into the matrix, reduce the grain boundary weakening effect of the alloy, and eliminate the micron-level Cu-rich phase and Er-rich phase by solid solution treatment, improve the alloy plasticity, and increase the lattice distortion of the aluminum-lithium alloy, providing a driving force for subsequent aging precipitation. In addition, a large number of dispersed nano-scale Al3Li phases and core-shell structure phases are precipitated during the aging treatment, further improving the strength of the aluminum-lithium alloy, so that the low Cu / Li ratio aluminum-lithium alloy has excellent strength and plasticity, and its tensile strength can reach 501MPa, and the elongation can reach 10.3%, achieving excellent strength-plasticity matching. In addition, the present invention has simple deformation and heat treatment processes, low equipment requirements, reduced industrial preparation costs, and is easier to achieve industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 TEM images of the Al-3Li-1Cu-0.4Mg-0.1Zr-0.1Er alloy prepared in Example 1: (a) bright field phase within the grain; (b) bright field phase at the grain boundary; (c) bright field image; (d) dark field phase and diffraction spots;

[0022] Figure 2 The stress-strain curve of the Al-3Li-1Cu-0.4Mg-0.1Zr-0.1Er alloy prepared in Example 1;

[0023] Figure 3 This is the stress-strain curve of the Al-3Li-1Cu-0.4Mg-0.1Zr-0.1Er alloy prepared in Comparative Example 1. DETAILED DESCRIPTION

[0024] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0025] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0026] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0027] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0028] Example 1

[0029] The aluminum-lithium alloy prepared in this embodiment is composed of the following components in mass percentage: Li 3%, Cu 1%, Mg 0.4%, Er 0.1%, Zr 0.1%, and the balance is Al, abbreviated as Al-3Li-1Cu-0.4Mg-0.1Er-0.1Zr.

[0030] The process steps for preparing the Al-3Li-1Cu-0.4Mg-0.1Er-0.1Zr alloy in this embodiment are as follows:

[0031] (1) Melting and casting

[0032] Industrial pure Al, industrial pure Li, Al-50wt.% Cu master alloy, Al-10wt.% Zr master alloy, Al-10wt.% Er master alloy are added into a crucible resistance furnace in the order of industrial pure aluminum, master alloy, industrial pure magnesium, and industrial pure lithium, and heated until the alloy is completely melted. After slag removal and refining treatment, they are cast into a metal mold.

[0033] (2) Homogenization annealing treatment

[0034] The cast aluminum-lithium alloy was subjected to homogenization annealing at a temperature of 500°C for 24 hours. After the insulation, it was cooled in the furnace to eliminate the segregation of elements between dendrites.

[0035] (3) Hot rolling treatment

[0036] The aluminum-lithium alloy that has completed the annealing treatment is hot rolled at a temperature of 500° C. and a cumulative deformation of 90%, thereby obtaining an aluminum-lithium alloy rolled plate with a thickness of 2 mm.

[0037] (4) Solution treatment

[0038] The aluminum-lithium alloy rolled plate obtained after hot rolling was subjected to solid solution treatment at a temperature of 560°C for 4 hours.

[0039] (5) Aging treatment

[0040] The aluminum-lithium alloy rolled plate that has completed the solid solution treatment was subjected to aging treatment at a temperature of 200°C for 7 hours to obtain an Al-3Li-1Cu-0.4Mg-0.1Er-0.1Zr alloy.

[0041] The structure of the Al-3Li-1Cu-0.4Mg-0.1Er-0.1Zr alloy was characterized. Figure 1 As shown by Figure 1 It can be seen that after solution aging treatment, the large-sized Cu-rich phases in the grains and near the grain boundaries are dissolved into the matrix, and there are no large-sized precipitation phases at the grain boundaries, which reduces the influence of grain boundary weakening. The alloy consists of two strengthening phases, one is the uniformly distributed Al3(Er, Zr, Li) core-shell structure phase, and the other is a large amount of uniformly dispersed Al3Li phase.

[0042] The mechanical properties of the Al-3Li-1Cu-0.4Mg-0.1Er-0.1Zr alloy were characterized. The stress-strain curves are shown in Figure 2. Figure 2 As shown by Figure 2 It can be seen that its tensile strength reaches 501 MPa and its elongation reaches 10.3%.

[0043] Comparative Example 1

[0044] The difference between this comparative example and Example 1 is that no solid solution and aging treatment is performed, and the rest of the operation process is the same as that of Example 1.

[0045] The mechanical properties of the aluminum-lithium alloy obtained in this comparative example were characterized, and the stress-strain curve was as follows: Figure 3 As shown by Figure 3 It can be seen that its tensile strength is 362MPa.

[0046] Although the present invention has been disclosed as above in the preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A high-strength and high-toughness aluminum-lithium alloy, characterized in that: The invention is composed of the following components in percentage by mass: 0.8% to 1.2% Cu, 2.8% to 3.5% Li, 0.3% to 0.5% Mg, 0.08% to 0.15% Zr, 0.08% to 0.15% Er, and the balance is Al.

2. The high-strength and high-toughness aluminum-lithium alloy according to claim 1, characterized in that: Aluminum ingot, Mg, metallic lithium, intermediate alloy Al-50wt.%Cu, Al-10wt.%Er and Al-10wt.%Zr are used as raw materials, and a cast alloy is obtained by smelting and casting, and then subjected to homogenization annealing, hot rolling, solid solution and aging treatment.

3. A method for preparing a high-strength and high-toughness aluminum-lithium alloy according to any one of claims 1 to 2, characterized in that: include: (1) melting and casting to obtain a cast AlLiCuMgErZr alloy; (2) The cast AlLiCuMgErZr alloy is subjected to homogenization annealing, hot rolling, solid solution and aging treatment to obtain a high-strength and high-toughness aluminum-lithium alloy.

4. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (1) The melting temperature is 720-780°C.

5. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (2) The homogenization annealing temperature is 480-520°C and the time is 16-32h.

6. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (2) The hot rolling treatment temperature is 475-525°C, and the cumulative deformation is 90%.

7. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (2) The solution treatment temperature is 550-580°C and the time is 3-5h.

8. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (2) The medium aging treatment temperature is 180-210°C and the time is 0-10h.

9. The method for preparing a high-strength and high-toughness aluminum-lithium alloy according to claim 3, characterized in that: (2) The medium aging treatment time is 7h.

10. Use of the low anisotropic aluminum-lithium alloy according to claim 1 as a lightweight, high-strength and high-toughness aluminum-lithium alloy.

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