Welding seam defect control method for 2195 aluminum-lithium alloy plate stirring and friction welding

Abstract

The invention discloses a 2195 aluminum-lithium alloy plate and a friction stir welding seam defect control method, and belongs to the technical field of ultra-large storage tank bottom manufacturing. Specifically, aiming at the problem of weld defect control of friction stir welding of the 2195 aluminum-lithium alloy plate, a 2195 aluminum-lithium alloy plate friction stir welding and weld defect control process path is planned and designed as a whole, and a two-stage aging process is adopted, so that a strengthening phase T1 phase, a strengthening phase delta'and a strengthening phase beta 'are kept small in size and are massively dispersed and distributed; by means of stepped heat treatment, residual stress is relieved / eliminated, strengthening phases in the weld joint and the base metal tend to be coordinated and consistent, the heat stability of the strengthening phases delta'and beta 'is guaranteed, grain boundaries are effectively pinned, grain growth is restrained, the strength level of the weld joint is guaranteed through a large number of T1 phases, and the continuity of the base metal-weld joint interface structure is improved.

Description

Technical Field

[0001] The present application belongs to the technical field of super-large tank bottom manufacturing, and relates to a method for controlling weld defects of friction stir welding (FSW) of aluminum-lithium alloy plates, and in particular to a method for controlling weld defects of friction stir welding of 2195 aluminum-lithium alloy plates. Background Art

[0003] The use of more efficient rocket body structures and lighter and higher-strength rocket body structural materials is an effective way to achieve lightweight and high reliability of launch vehicles. In order to meet the lightweight and high reliability requirements of super-large launch vehicles, it puts forward the demand for the integral manufacturing technology of the hemispherical shell of the Φ5000mm diameter 2195 aluminum-lithium alloy tank.

[0004] For the ultra-large, lightweight, high-strength 2195 aluminum-lithium alloy tank hemispherical shell with an inner diameter of ≥ Ф5000mm, a height of ≥ 1200mm, and a wall thickness of ≤ 2mm, the width of the plate used for its integral forming must be greater than 5000mm, while the maximum width of the current domestic rolling equipment is 4300mm, and the effective width of the plate after trimming is ≤ 4100mm, which cannot meet the integral forming requirements of the ultra-large, lightweight, high-strength 2195 aluminum-lithium alloy tank hemispherical shell of Ф5000mm. The use of welding technology to assemble and weld the plates with smaller widths to form ultra-large wide plates with a width greater than 5000mm can solve the problem of the demand for raw materials for the integral forming of the ultra-large 2195 aluminum-lithium alloy tank hemispherical shell.

[0005] The following are the processes for welding small width plates into large width plates: argon arc welding, laser welding, electron beam welding, stir friction welding, etc. Among them, stir friction welding has a higher welding coefficient (≥0.8) and is particularly suitable for the assembly and connection of aluminum alloy materials such as 2219 and 2195. Therefore, it is widely used in the preparation of large width / ultra-large width aluminum alloy plates in the aerospace field.

[0006] Small-width 2195 aluminum-lithium alloy plates are used to assemble and connect them through stir friction welding to form large-width 2195 aluminum plates. The main difficulty is that after stir friction welding, the weld position of the 2195 aluminum plate is prone to partial incomplete fusion; in addition, the weld position has uneven structure, and the microstructure of the parent material and the weld position is significantly different; in addition, after stir friction welding, abnormal grain growth is very likely to occur in the weld structure, which seriously affects the mechanical properties of the weld position of the 2195 aluminum plate, resulting in instability and cracking of the weld position during the subsequent overall forming process. Summary of the invention

[0007] The technical problem solved by the present application is: to overcome the shortcomings of the prior art and provide a method for controlling weld defects in friction stir welding of 2195 aluminum-lithium alloy plates, to ensure uniform dispersion and precipitation of strengthening phases at the welds through a two-stage aging process, to pin grain boundaries, and to inhibit abnormal grain growth at the welds; to regulate the uniformity of weld structure through a step heat treatment process, to make the second phase of the weld consistent with that of the base material, to improve the continuity of the base material-weld interface structure while alleviating / eliminating residual stress.

[0008] The technical solutions provided by this application are as follows:

[0009] A method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding comprises the following steps:

[0010] S1. Preparation of small width 2195 aluminum-lithium alloy plates;

[0011] S2. Solution treatment and double-stage aging treatment are sequentially performed on small width 2195 aluminum-lithium alloy plates;

[0012] S3. Carry out milling and polishing of small width 2195 aluminum-lithium alloy plates;

[0013] S4, welding at least two small width 2195 aluminum-lithium alloy plates by friction stir welding to prepare a large width 2195 aluminum-lithium alloy plate; the width of the small width 2195 aluminum-lithium alloy plate is less than the width of the large width 2195 aluminum-lithium alloy plate, so it is a small width 2195 aluminum-lithium alloy plate;

[0014] S5. Step heat treatment of wide width 2195 aluminum-lithium alloy plates.

[0015] The solution treatment process comprises: heat preservation at 520-540° C. for 90-150 minutes and then quenching treatment, and the quenching transfer time is ≤40 seconds.

[0016] The two-stage aging treatment includes low-temperature pre-aging and high-temperature aging performed sequentially, wherein the low-temperature pre-aging is to keep the temperature at 100-120° C. for 4-8 hours and then air-cool, and the high-temperature aging is to keep the temperature at 170-180° C. for 32-36 hours and then air-cool.

[0017] After the double-stage aging treatment, the second phases δ′ and β′ in the alloy of the small width 2195 aluminum-lithium alloy plate are dispersed and have sizes of 20 to 50 nm and 20 to 70 nm, respectively; at the same time, a large amount of T1 phase is precipitated in the alloy, and the T1 phase is evenly distributed and arranged in parallel in a needle shape and has a size of 100 to 150 nm.

[0018] The milled and polished plane is the subsequent welding surface of the small-width 2195 aluminum-lithium alloy plate, and its surface roughness reaches 6.3 and the flatness is ≤0.1.

[0019] Large-width 2195 aluminum-lithium alloy plates were obtained by stir friction welding and subjected to step heat treatment to relieve / eliminate internal residual stress while achieving synergy between the strengthening phases in the weld and the base material, and on this basis suppressing abnormal grain growth at the weld position.

[0020] The step heat treatment comprises:

[0021] Place the wide 2195 aluminum-lithium alloy plate into a heat treatment furnace, heat it to 260-330°C, the heating rate is 5-8°C / s, and the holding time is 16-18h;

[0022] Continue to heat up to 360-460°C with the furnace, the heating rate is 3-5°C / h, and the holding time is 12-14h;

[0023] Cool down to 260-330℃ with the furnace, the cooling rate is 3-5℃ / h, and the holding time is 4-6h;

[0024] The wide 2195 aluminum-lithium alloy sheets are taken out of the furnace and air-cooled to room temperature.

[0025] During the step heat treatment process, the δ′ phase and β′ phase located at the grain boundary have strong thermal stability, can pin the grain boundary, and effectively inhibit the abnormal growth of weld grains; at the same time, a large amount of T1 phase ensures the strength level of the weld and improves the continuity of the parent material-weld interface structure.

[0026] A 2195 aluminum-lithium alloy plate is prepared using any of the above-mentioned methods for controlling weld defects in friction stir welding of a 2195 aluminum-lithium alloy plate.

[0027] In summary, this application at least includes the following beneficial technical effects:

[0028] (1) In view of the difficulty in controlling weld defects in friction stir welding of 2195 aluminum-lithium alloy plates, the present invention comprehensively plans and designs a process path for friction stir welding and weld defect control of 2195 aluminum-lithium alloy plates. Through a two-stage aging process, the strengthening phases T1 phase, δ′ phase, and β′ phase are kept small in size and dispersed in large quantities. Through step heat treatment, while relieving / eliminating residual stress, the strengthening phases in the weld and the base material tend to be coordinated and consistent, ensuring the thermal stability of the strengthening phases δ′ phase and β′ phase, so that they can effectively pin the grain boundaries and inhibit grain growth. A large amount of T1 phase ensures the strength level of the weld and improves the continuity of the base material-weld interface structure.

[0029] (2) The present invention performs a solution treatment on the 2195 aluminum-lithium alloy plate before friction stir welding, the solution temperature is 520-540°C, the insulation time is 90-150 min, and the plate is quenched after the insulation, and the quenching transfer time is ≤40 s, thereby ensuring the supersaturation of the alloy after the solution treatment and laying a foundation for subsequent aging precipitation.

[0030] (3) The present invention performs a double-stage aging treatment on the 2195 aluminum-lithium alloy plate before undergoing friction stir welding. The pre-aging temperature is 100-120°C, the holding time is 4-8 hours, and the plate is air-cooled after the holding period. The high-temperature aging temperature is 170-180°C, the holding time is 32-36 hours, and the plate is air-cooled after the holding period. The double-stage aging ensures that the second phases δ′ and β′ in the alloy are dispersed and have a size of 50-80 nm. At the same time, a large amount of T1 phase is precipitated in the alloy, and the T1 phase is evenly distributed and has a size of 100-150 nm.

[0031] (4) The present invention performs a step heat treatment process on the 2195 aluminum-lithium alloy plate after friction stir welding, which reduces / eliminates the residual stress of the assembly D while achieving coordinated strengthening between the weld and the base material.

[0032] (5) During the step heat treatment of the 2195 aluminum-lithium alloy plate after friction stir welding, the δ′ phase and β′ phase located at the grain boundary can pin the grain boundary and effectively inhibit the abnormal grain growth of the weld; at the same time, a large amount of T1 phase ensures the strength level of the weld and improves the continuity of the parent material-weld interface structure.

[0033] (6) The present invention relates to a method for controlling weld defects in friction stir welding of 2195 aluminum-lithium alloy plates. The friction stir welding and weld defect control process paths of the 2195 aluminum-lithium alloy plates are comprehensively planned and designed, and a two-stage aging process is adopted to keep the strengthening phases T1 phase, δ′ phase, and β′ phase small in size and dispersed in large quantities. Through step heat treatment, while relieving / eliminating residual stress, the strengthening phases in the weld and the base material tend to be coordinated and consistent, thereby ensuring the thermal stability of the strengthening phases δ′ phase and β′ phase, so that they can effectively pin the grain boundaries and inhibit grain growth. A large amount of T1 phase ensures the strength level of the weld and improves the continuity of the base material-weld interface structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a schematic diagram of a 1000mm×1000mm×30mm square plate;

[0035] Figure 2a Schematic diagram of the δ′ phase in the dark field image of a transmission electron microscope;

[0036] Figure 2b This is a schematic diagram of the β′ phase in the bright field image of a transmission electron microscope;

[0037] Figure 2c This is a schematic diagram of the T1 phase in the dark field image of a transmission electron microscope;

[0038] Figure 3 Schematic diagram of the friction stir welding process;

[0039] Figure 4a This is a schematic diagram of the δ′ phase at the grain boundary position in a transmission electron microscope bright field image;

[0040] Figure 4b Schematic diagram of the β′ phase and T1 phase at the grain boundary position in the dark field image of the transmission electron microscope. DETAILED DESCRIPTION

[0041] In order to make the objectives, technical solutions and advantages of the present invention more clear, the embodiments disclosed in the present invention will be further described in detail below with reference to the accompanying drawings.

[0042] The present application embodiment discloses a method for controlling weld defects of a 2195 aluminum-lithium alloy plate by friction stir welding, the method comprising the following steps:

[0043] (1) Preparation of small width 2195 aluminum-lithium alloy plates

[0044] Four 2195 aluminum-lithium alloy square plates with a size of 1000 mm × 1000 mm × 30 mm were cut successively from four annealed (O state) 2195 aluminum-lithium alloy square plates with a size of 1050 mm × 1050 mm × 30 mm, such as Figure 1 shown.

[0045] (2)Solid solution and two-stage aging treatment

[0046] The 2195 aluminum-lithium alloy square plate with a size of 1000 mm×1000 mm×30 mm obtained in step (1) is subjected to a solution treatment at a solution temperature of 520 to 540° C. and a holding time of 90 to 150 min. After the holding is completed, the plate is quenched and the quenching transfer time is ≤40 s, so that the alloy elements are dissolved into the Al matrix of the 2195 aluminum-lithium alloy as much as possible, creating conditions for subsequent aging precipitation strengthening phase.

[0047] The strengthening phases in 2195 aluminum-lithium alloy include long strip T1 phase (Al2CuLi), δ′ phase (Al3Li), and point / spherical β′ phase (Al3Zr). The small-sized strengthening phases and their large-scale dispersed distribution can effectively pin the grain boundaries and inhibit grain growth, especially the δ′ phase and β′ phase.

[0048] Step (1) The aging treatment of the 2195 aluminum-lithium alloy square plate with a size of 1000mm×1000mm×30mm is divided into two stages, namely, pre-aging at a lower temperature and high-temperature aging at a higher temperature. The pre-aging temperature is 100-120°C, the insulation time is 4-8h, and the furnace is air-cooled after the insulation is completed; the high-temperature aging temperature is 170-180°C, the insulation time is 32-36h, and the furnace is air-cooled after the insulation is completed.

[0049] After the 2195 aluminum-lithium alloy square plate with a size of 1000 mm×1000 mm×30 mm obtained in step (1) is subjected to double-stage aging treatment, the second phases δ′ phase and β′ phase in the alloy are dispersed and have a size order of 20 to 50 nm and 20 to 70 nm, respectively. Figure 2a and 2b As shown; at the same time, a large amount of T1 phase precipitates in the alloy, the T1 phase is evenly distributed and the size is 100-150nm, as shown Figure 2c shown.

[0050] (3) Milling and polishing

[0051] The 2195 aluminum-lithium alloy square plate having been processed in step (2) and having a size of 1000 mm×1000 mm×30 mm is milled and polished so that the plane surface of 1000 mm×30 mm is smooth, the surface roughness reaches 6.3, and the flatness is ≤0.1.

[0052] (4) Preparation of large width 2195 aluminum-lithium alloy plates

[0053] Two 2195 aluminum-lithium alloy square plates with a size of 1000mm×1000mm×30mm that have undergone step (3) are installed and fixed on a welding platform, a 1000mm×30mm plane is arbitrarily selected from one of the plates and defined as A1, and a 1000mm×30mm plane is arbitrarily selected from the other plate and defined as A2, and A1 and A2 are connected along the length direction of A1 and A2 by stir friction welding, the formed assembly is defined as A, and the weld is defined as A0.

[0054] Continue to select two 2195 aluminum-lithium alloy square plates with a size of 1000mm×1000mm×30mm that have undergone step (3) to repeat the above process. The contacting 1000mm×30mm planes are defined as B1 and B2 respectively. Stir friction welding is used to connect B1 and B2 along the length direction of B1 and B2. The formed assembly is defined as B, and the weld is defined as B0.

[0055] Install and fix the assembly A and B on the welding platform, and select a 2000mm×30mm plane from A at random and define it as A. 11 , select any 2000mm×30mm plane from B and define it as B 11 , using friction stir welding, along A 11 and B 11 A and B are connected in the length direction, the formed assembly is defined as C, and the weld is defined as C0.

[0056] A new weld is formed along the direction A0B0 by friction stir welding and is defined as D0, and the formed assembly is defined as D.

[0057] In the step (4), D0 starts at the A0 end and ends at the B0 end, and the distance between the starting position of D0 and C0 is A0 / 2, and the distance between the ending position of D0 and C0 is B0 / 2, such as Figure 3 shown.

[0058] In the step (4), the friction stir welding method used is double-sided welding, that is, after a certain weld is formed, the assembly is flipped 180° and welding is continued on the back side of the weld and along the direction of the weld.

[0059] (5) Step heat treatment

[0060] The assembly D obtained after step (4) is subjected to a step heat treatment to relieve / eliminate the residual stress of the assembly D while achieving synergy between the strengthening phases in the weld and the base material, thereby suppressing abnormal grain growth at the weld position.

[0061] In the step (5), the step heat treatment of the assembly D is as follows:

[0062] 1) Place the assembly D in a heat treatment furnace, heat it to 260-330°C, at a heating rate of 5-8°C / s, and keep it at this temperature for 16-18h;

[0063] 2) The assembly D in the heat treatment furnace is continuously heated to 360-460°C with the furnace, the heating rate is 3-5°C / h, and the holding time is 12-14h;

[0064] 3) Cooling the assembly D in the heat treatment furnace to 260-330°C, with a cooling rate of 3-5°C / h and a holding time of 4-6h;

[0065] 4) Take the assembly D out of the heat treatment furnace and air-cool it to room temperature.

[0066] In the step (5), during the step heat treatment of the assembly D, the δ′ phase and β′ phase located at the grain boundary have strong thermal stability and can pin the grain boundary, such as Figure 4a and Figure 4b As shown in the figure, the abnormal grain growth of the weld and the base material is effectively suppressed, especially at the weld position; at the same time, the strengthening phases in the weld and the base material tend to be coordinated and consistent, and a large amount of T1 phase ensures the strength level of the weld and the base material, especially at the weld position, and improves the continuity of the base material-weld interface structure.

[0067] Example 1

[0068] In this embodiment, the raw material is an annealed (O state) 2195 aluminum-lithium alloy square plate with a size of 1050 mm×1050 mm×30 mm. The following is a specific process of a method for controlling weld defects of a 2195 aluminum-lithium alloy plate by friction stir welding:

[0069] A method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding comprises the following steps:

[0070] Step (1) Preparation of small width 2195 aluminum-lithium alloy sheet

[0071] Four 2195 aluminum-lithium alloy square plates with a size of 1000 mm × 1000 mm × 30 mm were cut successively from four annealed (O state) 2195 aluminum-lithium alloy square plates with a size of 1050 mm × 1050 mm × 30 mm, such as Figure 1 shown.

[0072] Step (2) Solution treatment and two-stage aging treatment

[0073] The 2195 aluminum-lithium alloy square plate with a size of 1000 mm×1000 mm×30 mm obtained in step (1) is subjected to a solution treatment at a solution temperature of 530° C. and a holding time of 120 min. After the holding is completed, the plate is quenched and the quenching transfer time is ≤40 s, so that the alloy elements are dissolved into the Al matrix of the 2195 aluminum-lithium alloy as much as possible, creating conditions for the subsequent aging precipitation strengthening phase.

[0074] The strengthening phases in 2195 aluminum-lithium alloy include long strip T1 phase (Al2CuLi), δ′ phase (Al3Li), and point / spherical β′ phase (Al3Zr). The small-sized strengthening phases and their large-scale dispersed distribution can effectively pin the grain boundaries and inhibit grain growth, especially the δ′ phase and β′ phase.

[0075] Step (1) The aging treatment of the 2195 aluminum-lithium alloy square plate with a size of 1000mm×1000mm×30mm is divided into two stages, namely, pre-aging at a lower temperature and high-temperature aging at a higher temperature. The pre-aging temperature is 120°C, the holding time is 6h, and the plate is air-cooled after the holding is completed; the high-temperature aging temperature is 175°C, the holding time is 32h, and the plate is air-cooled after the holding is completed.

[0076] After the 2195 aluminum-lithium alloy square plate with a size of 1000 mm×1000 mm×30 mm obtained in step (1) is subjected to double-stage aging treatment, the second phases δ′ phase and β′ phase in the alloy are dispersed and have a size order of 20 to 50 nm and 20 to 70 nm, respectively. Figure 2a and 2b As shown; at the same time, a large amount of T1 phase precipitates in the alloy, the T1 phase is evenly distributed and the size is 100-150nm, as shown Figure 2c shown.

[0077] Step (3) Milling and polishing

[0078] The 2195 aluminum-lithium alloy square plate having been processed in step (2) and having a size of 1000 mm×1000 mm×30 mm is milled and polished so that the plane surface of 1000 mm×30 mm is smooth, the surface roughness reaches 6.3, and the flatness is ≤0.1.

[0079] Step (4) Preparation of large width 2195 aluminum-lithium alloy sheet

[0080] Two 2195 aluminum-lithium alloy square plates with dimensions of 1000 mm × 1000 mm × 30 mm, which have been processed in step (3), are mounted and fixed on a welding platform. A 1000 mm × 30 mm plane is randomly selected from one of the plates and defined as A1. A 1000 mm × 30 mm plane is randomly selected from the other plate and defined as A2. A1 and A2 are connected along the length direction of A1 and A2 by friction stir welding. The formed assembly is defined as A, and the weld is defined as A0. Figure 3 shown.

[0081] Continue to select two 2195 aluminum-lithium alloy square plates with dimensions of 1000 mm × 1000 mm × 30 mm that have been processed in step (3) and repeat the above process. The contacting 1000 mm × 30 mm planes are defined as B1 and B2 respectively. B1 and B2 are connected along the length direction of B1 and B2 by stir friction welding. The formed assembly is defined as B, and the weld is defined as B0. Figure 3 shown.

[0082] Install and fix the assembly A and B on the welding platform, and select a 2000mm×30mm plane from A at random and define it as A. 11 , select any 2000mm×30mm plane from B and define it as B 11 , using friction stir welding, along A 11 and B 11 The length direction of A and B is connected, the resulting assembly is defined as C, and the weld is defined as C0. Figure 3 shown.

[0083] A new weld is formed along the direction A0B0 by friction stir welding and defined as D0, and the formed assembly is defined as D, such as Figure 3 shown.

[0084] In the step (4), D0 starts at the A0 end and ends at the B0 end, and the distance between the starting position of D0 and C0 is A0 / 2, and the distance between the ending position of D0 and C0 is B0 / 2, such as Figure 3 shown.

[0085] In the step (4), the friction stir welding method used is double-sided welding, that is, after a certain weld is formed, the assembly is flipped 180° and welding is continued on the back side of the weld and along the direction of the weld.

[0086] Step (5) Step heat treatment

[0087] The assembly D obtained after step (4) is subjected to a step heat treatment to relieve / eliminate the residual stress of the assembly D while achieving synergy between the strengthening phases in the weld and the base material, thereby suppressing abnormal grain growth at the weld position.

[0088] In the step (5), the step heat treatment of the assembly D is as follows:

[0089] 1) Place assembly D in a heat treatment furnace, heat it to 300°C, at a heating rate of 5°C / s, and keep it at this temperature for 16 hours;

[0090] 2) The assembly D in the heat treatment furnace is continuously heated to 420°C with the furnace, the heating rate is 3°C / h, and the holding time is 12h;

[0091] 3) Cooling the assembly D in the heat treatment furnace to 300°C with the furnace, with a cooling rate of 3°C / h and a holding time of 6h;

[0092] 4) Take the assembly D out of the heat treatment furnace and air-cool it to room temperature.

[0093] In the step (5), during the step heat treatment of the assembly D, the δ′ phase and β′ phase located at the grain boundary have strong thermal stability and can pin the grain boundary, as shown in FIG4 , effectively inhibiting the abnormal grain growth of the weld and the base material, especially at the weld position; at the same time, the strengthening phases in the weld and the base material tend to be coordinated and consistent, and a large amount of T1 phase ensures the strength level of the weld and the base material, especially at the weld position, thereby improving the continuity of the base material-weld interface structure.

[0094] In this embodiment, in order to solve the problem of weld defect control in friction stir welding of 2195 aluminum-lithium alloy plate, the friction stir welding and weld defect control process paths of 2195 aluminum-lithium alloy plate are comprehensively planned and designed, and a two-stage aging process is adopted to keep the strengthening phases T1 phase, δ′ phase, and β′ phase small in size and dispersed in large quantities; through step heat treatment, while reducing / eliminating residual stress, the strengthening phases in the weld and the base material tend to be coordinated and consistent, thereby ensuring the thermal stability of the strengthening phases δ′ phase and β′ phase, so that they can effectively pin the grain boundaries and inhibit grain growth. A large amount of T1 phase ensures the strength level of the weld and improves the continuity of the base material-weld interface structure.

[0095] The contents not described in detail in this application specification belong to the common knowledge of those skilled in the art.

[0096] The present application is described in detail above in conjunction with specific implementation methods and exemplary examples, but these descriptions cannot be understood as limiting the present application. Those skilled in the art understand that, without departing from the spirit and scope of the present application, a variety of equivalent replacements, modifications or improvements can be made to the technical solution of the present application and its implementation methods, all of which fall within the scope of the present application. The scope of protection of the present application shall be subject to the attached claims.

Claims

1. A method for controlling weld defects in friction stir welding of 2195 aluminum-lithium alloy plates, characterized in that: The steps include: S1. Preparation of small width 2195 aluminum-lithium alloy plates; S2. Solution treatment and double-stage aging treatment are sequentially performed on the small width 2195 aluminum-lithium alloy plate; S3. Carry out milling and polishing of small width 2195 aluminum-lithium alloy plates; S4, welding at least two small width 2195 aluminum-lithium alloy plates by friction stir welding to prepare a large width 2195 aluminum-lithium alloy plate; S5. Step heat treatment of wide width 2195 aluminum-lithium alloy plates.

2. The method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1, characterized in that: The solution treatment process comprises: heat preservation at 520-540° C. for 90-150 minutes and then quenching treatment, and the quenching transfer time is ≤40 seconds.

3. The method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1, characterized in that: The two-stage aging treatment includes low-temperature pre-aging and high-temperature aging performed sequentially, wherein the low-temperature pre-aging is to keep the temperature at 100-120° C. for 4-8 hours and then air-cool, and the high-temperature aging is to keep the temperature at 170-180° C. for 32-36 hours and then air-cool.

4. A method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1 or 3, characterized in that: After the double-stage aging treatment, the second phases δ′ and β′ in the alloy of the small width 2195 aluminum-lithium alloy plate are dispersed and have sizes of 20 to 50 nm and 20 to 70 nm, respectively; at the same time, a large amount of T1 phase is precipitated in the alloy, and the T1 phase is evenly distributed and arranged in parallel in a needle shape and has a size of 100 to 150 nm.

5. The method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1, characterized in that: The milled and polished plane is the subsequent welding surface of the small-width 2195 aluminum-lithium alloy plate, and its surface roughness reaches 6.3 and the flatness is ≤0.

1.

6. The method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1, characterized in that: The step heat treatment comprises: Place the wide 2195 aluminum-lithium alloy plate into a heat treatment furnace, heat it to 260-330°C, the heating rate is 5-8°C / s, and the holding time is 16-18h; Continue to heat up to 360-460°C with the furnace, the heating rate is 3-5°C / h, and the holding time is 12-14h; Cool down to 260-330℃ with the furnace, the cooling rate is 3-5℃ / h, and the holding time is 4-6h; The wide 2195 aluminum-lithium alloy sheets are taken out of the furnace and air-cooled to room temperature.

7. The method for controlling weld defects of 2195 aluminum-lithium alloy plate friction stir welding according to claim 1, characterized in that: During the step heat treatment process, the δ′ phase and β′ phase located at the grain boundary have strong thermal stability, can pin the grain boundary, and effectively inhibit the abnormal growth of weld grains; at the same time, a large amount of T1 phase ensures the strength level of the weld and improves the continuity of the parent material-weld interface structure.

8. A 2195 aluminum-lithium alloy plate, characterized in that: The invention is prepared by using a 2195 aluminum-lithium alloy plate friction stir welding weld defect control method as described in any one of claims 1 to 7.

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