High-strength low-serrated flow 5xxx aluminum alloy sheet and method of making and using same

Abstract

The application discloses a kind of high-strength low-sawtooth rheological 5xxx aluminum alloy plate and its preparation method and application, belong to metal material processing technical field.The application adopts three-stage synergistic process: step 1: 5xxx aluminum alloy plate alloy is carried out two-stage high-temperature annealing pretreatment;Step 2: 5xxx aluminum alloy plate after step 1 processing is carried out friction stir processing (FSP);Step 3: 5xxx aluminum alloy plate after step 2 processing is carried out rolling deformation.The processing method of the application, process is simple, short cycle, low energy consumption, can make 5xxx aluminum alloy plate yield strength ≥389 MPa, tensile strength ≥407 MPa, elongation ≥7.5%;The average amplitude of sawtooth is reduced to low level of 0.28 MPa simultaneously, the application has high strength, good plasticity and the comprehensive performance of extremely inhibiting sawtooth rheological, provides new way for high service reliability 5xxx aluminum alloy plate preparation.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-strength low-serrated rheological 5xxx aluminum alloy plate and its preparation method and application, in particular to a high-strength low-serrated rheological 5xxx aluminum alloy plate realized by friction stir pretreatment coupled with large strain rolling and its preparation method and application. It belongs to the technical field of metal material processing. BACKGROUND

[0002] Aluminum alloy has a wide application prospect in the fields of aerospace, transportation, etc. due to its light weight, corrosion resistance and good processing performance. 5xxx aluminum alloy can refine grains and improve strength by adding Sc element to form nanoscale Al3Sc precipitates. However, the alloy has a serious plastic instability phenomenon under dynamic service load, i.e. serrated rheological behavior (Portevin-Le Chatelier effect). This stress mutation caused by the dynamic interaction of solute atoms and dislocations not only causes surface wrinkles of the material, reduces fatigue life, but also induces unpredictable sudden failure. Existing technical means are difficult to simultaneously solve the triple contradiction of strength-plasticity-deformation stability, for example, after applying 80% cold rolling deformation to Al-Mg-Sc alloy (see Figure 2 Comparison curve), the yield strength is increased to about 310 MPa, the tensile strength is increased to about 338 MPa, the serrated rheological behavior is partially relieved, but the elongation is usually reduced to less than 3%, which greatly limits its engineering application.

[0003] Friction stir processing is an effective means of grain refinement, which has been proved to improve the strength of 5xxx aluminum alloy. However, the existing technology only focuses on the improvement of its static mechanical properties, completely ignoring two key problems. On the one hand, conventional FSP itself causes a serrated amplitude of 4.3 MPa, even higher than the rolled alloy, for example, the recent cryogenic friction stir processing can achieve a tensile strength of 395 MPa and an elongation of 18.5%, but its yield strength is only 225 MPa and the serrated amplitude is as high as 3.8 MPa (see Figure 2 Comparison curve), which cannot meet the dual requirements of high yield strength and deformation stability for load-bearing components; on the other hand, the microstructure gradient between the FSP zone and the matrix causes strain localization in subsequent rolling, further deteriorating the rheological instability. Especially in the large strain rolling coupling process, how to simultaneously suppress the serrated rheology through FSP pretreatment is still a technical blind area that has not been explored.

[0004] Theoretical studies show that the serrated flow behavior is controlled by dislocation debonding activation energy and solute diffusion rate. To achieve the "high strength-good plasticity-low serrated flow" impossible triangle, a cross-scale synergistic regulation mechanism must be established: limiting the dynamic pinning of solute atoms at the nanoscale and constructing uniform dislocation slip channels at the micrometer scale. However, existing single processes (such as cryogenic FSP, warm rolling, and room temperature large deformation) or simple process combinations have not been able to break through the technical barriers of serrated flow inhibition due to the inability to coordinate the ternary interaction of "precipitate-dislocation-grain boundary". SUMMARY

[0005] In view of the above problems existing in the prior art, the purpose of the present application is to provide a method for preparing high-strength low-serrated flow 5xxx aluminum alloy plate by coupling friction stir pretreatment with large strain rolling, which builds a heterogeneous structure through friction stir processing pretreatment and activates back stress through rolling to solve the core problem of the triple contradiction of high strength, good plasticity and deformation stability.

[0006] Meanwhile, the present application provides a high-strength low-serrated flow 5xxx aluminum alloy plate.

[0007] Meanwhile, the present application provides a high-strength low-serrated flow 5xxx aluminum alloy plate.

[0008] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0009] A high-strength low-serrated flow 5xxx aluminum alloy plate and a method for preparing the same, specifically comprising the following steps:

[0010] Step 1: Two-stage high-temperature annealing pretreatment is performed on the 5xxx aluminum alloy plate.

[0011] Step 2: The 5xxx aluminum alloy plate treated in step 1 is subjected to friction stir processing.

[0012] Step 3: The 5xxx aluminum alloy plate treated in step 2 is subjected to rolling deformation.

[0013] Preferably, in step 1, the first-stage annealing temperature is 380-410℃, the holding time is 1h, and then water quenching is performed to room temperature; the second-stage annealing temperature is 430-450℃, the holding time is 1h, and then water quenching is performed to room temperature.

[0014] Preferably, in step 2, the 5xxx aluminum alloy plate is processed by a friction stir processing device, which can be single pass or multiple passes, the processing temperature is maintained at 20-25℃, the rotation speed of the stirring head is 350-550rpm, the travel speed is controlled at 80-150mm / min, the inclination angle of the stirring head is 1-3°, and the stirring head feature can be a conical needle.

[0015] Preferably, in step 3, the rolling temperature is kept at 20-25℃, the total rolling deformation (reduction) is kept at 80-85%, the final rolling thickness of the plate is in the range of 1.1-0.7mm, preferably 1.0-0.75mm, and the pass reduction is kept at 10%.

[0016] Preferably, step 1 cooperates with step 2, and step 2 cooperates with step 3.

[0017] Preferably, the 5xxx aluminum alloy plate can be an Al-Mg-Sc alloy.

[0018] A high-strength low-sawteeth rheology 5xxx aluminum alloy plate comprises a non-homogeneous layered structure, i.e. an upper and lower fine layer structure and a coarse layer structure, the fine layer structure is a mixed distribution of fine lamella and subgrains, and the coarse layer structure is a mixed distribution of coarse lamella and subgrains.

[0019] Preferably, the width of the fine lamella is less than 10µm, preferably 4.5µm; the width of the coarse lamella is greater than 10µm, preferably 30µm; and the subgrain is a deformed grain with an orientation difference less than 2°.

[0020] The deformed grain is formed together with the layered structure in the rolling process and is a deformation characteristic of the material; the judgment feature of the subgrain is that the orientation difference is less than 2°.

[0021] The high-strength low-sawteeth rheology 5xxx aluminum alloy plate of the present application is suitable for continuous production of large-size plates, and the length of the plate is ≥940mm and the width is ≥80mm.

[0022] The application of a high-strength low-sawteeth rheology 5xxx aluminum alloy plate in a dynamic load-bearing component, the dynamic load-bearing component comprising a suspension control arm, a steering knuckle, a battery pack shell / structural support, a UAV body structure / boom connecting piece, an industrial robot joint arm / link, a key connecting piece of an excavator / loader boom / dipper.

[0023] Specifically, the dynamic load-bearing component of the present application is a high-reliability dynamic load-bearing component, which can be applied in the following fields: automobile / transportation field: suspension control arm, steering knuckle, battery pack shell / structural support; industrial machinery / robot field: UAV body structure / boom connecting piece, industrial robot joint arm / link, key connecting piece of engineering machinery (excavator, loader) boom / dipper.

[0024] A dynamic load-bearing component is prepared from a high-strength low-sawteeth rheology 5xxx aluminum alloy plate according to the present application.

[0025] A high-strength low-sawteeth rheology 5xxx aluminum alloy plate, which has a non-homogeneous layered structure as a microstructure feature.

[0026] The present application has the following beneficial effects:

[0027] 1、 The present application reduces the average amplitude of sawtooth to 0.28 MPa (measured value) under the condition of 80%-85% large strain rolling through annealing-FSP-rolling triple synergistic regulation, which is reduced by 93% compared with the conventional friction stir processing process (4.3 MPa) and reduced by 92% compared with the cryogenic friction stir processing process (3.6 MPa). This effect solves the problem of plastic instability caused by dislocation-solute interaction out of control under high strength and large deformation of 5xxx aluminum alloy, and provides key support for high-reliability dynamic load-bearing components.

[0028] 2、 The present application realizes yield strength ≥ 389 MPa and tensile strength ≥ 407 MPa under the premise of ensuring elongation ≥ 7.5%. Compared with the cryogenic friction stir processing process (yield strength 225 MPa), the yield strength is increased by 77%; compared with the traditional 80% cold rolling process (elongation < 3%), the plasticity is increased by more than 3 times, and the synergistic gain of strength and plasticity-stability is achieved simultaneously in large deformation rolling.

[0029] 3、 The present application uses friction stir pretreatment and rolling large deformation processing method to process 5xxx aluminum alloy plate, realizes non-homogeneous layered structure in a short operation time, promotes dislocation accumulation at the soft / hard interface during soft domain deformation, induces back stress (measured value ≥ 100 MPa), and significantly improves the work hardening capacity.

[0030] 4、 The present application completes the friction stir pretreatment and rolling deformation at room temperature, discards the complex processes such as cryogenic and multi-pass annealing, and the total time of double-stage annealing is ≤ 3h, and the rolling has no temperature control requirement; the energy consumption is reduced by more than 40%, which is suitable for continuous production of large-size plate.

[0031] The application relates to the technical field of metal material processing, and particularly discloses a preparation method for realizing high-strength low-serrated rheology of 5xxx aluminum alloy plate through friction stir pretreatment coupling large-strain rolling. In view of the core problem of the existing contradiction between high strength and low serrated rheology of the 5xxx aluminum alloy, a three-stage synergistic process is adopted: step 1: double-stage high-temperature annealing pretreatment is carried out on the 5xxx aluminum alloy plate; the first-stage annealing temperature is 380-410 DEG C, the holding time is 1 h, and then the temperature is cooled to room temperature; the second-stage annealing temperature is 430-450 DEG C, the holding time is 1 h, and then the temperature is cooled to room temperature; step 2: the 5xxx aluminum alloy plate treated in step 1 is subjected to friction stir processing (FSP); the processing temperature is kept at 20 DEG C-25 DEG C, the rotating speed of the stirring head is 350 rpm-550 rpm, the advancing speed is controlled to be 80 mm / min-150 mm / min, and the inclination angle of the stirring head is 1 DEG -3 DEG; and step 3: the 5xxx aluminum alloy plate treated in step 2 is subjected to rolling deformation; the rolling temperature is kept at 20 DEG C-25 DEG C, the total rolling deformation (reduction rate) is kept at 80%-85%, and the final rolling thickness of the plate ranges from 1.1 mm to 0.7 mm. By adopting the treatment method, the process is simple, the cycle is short, and the energy consumption is low, so that the yield strength of the 5xxx aluminum alloy plate is greater than or equal to 389 MPa, the tensile strength is greater than or equal to 407 MPa, and the elongation is greater than or equal to 7.5%; meanwhile, the average amplitude of the serration is reduced to a low level of 0.28 MPa, which is reduced by 93% compared with 4.3 MPa of a conventional FSP process and is reduced by 92% compared with 3.6 MPa of a cryogenic FSP process. By means of the annealing-FSP-rolling triple synergistic regulation mechanism, the grain is super-fined, the dislocation movement characteristics are optimized, the comprehensive performance of high strength, good plasticity and extreme inhibition of serrated rheology is achieved, and a new way is provided for the preparation of the 5xxx aluminum alloy plate with high service reliability. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 The flowchart of the method is shown in the application;

[0033] Figure 2 The stress-strain curves of the examples and the comparative examples are shown in the application;

[0034] Figure 3 The heterogeneous layered structure organization photo of example 1 of the application is shown in the application;

[0035] Figure 4 The sub-grain photo of example 1 of the application is shown in the application;

[0036] Figure 5 The quantitative statistical results of the serrated rheological behavior of example 1 and the comparative example are shown in the application;

[0037] Figure 6 The transmission electron microscope organization photo of example 1 and comparative example 5 of the application is shown in the application. Detailed Implementation

[0038] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Example 1

[0039] according to Figure 1 The flowchart shown is a schematic diagram of the method. The material used is an Al-3Mg-0.25Sc (wt.%) alloy with a thickness of 5 mm.

[0040] The Al-Mg-Sc alloy contains the following composition by mass percentage: Mg: 3%, Sc: 0.25%, and the balance Al.

[0041] A high-strength, low-serration rheological 5xxx aluminum alloy sheet and its preparation method, specifically including the following steps:

[0042] Step 1: Perform a first-stage annealing at 380℃ for 1 hour and a second-stage annealing at 430℃ for 1 hour on the Al-Mg-Sc alloy sheet, followed by water quenching to room temperature.

[0043] Step 2: Perform friction stir processing on the Al-Mg-Sc alloy sheet processed in Step 1. The processing temperature is maintained at 20℃, the stirring head rotation speed is 350rpm, the stirring head travel speed is 80mm / min, and the stirring head tilt angle is 1°.

[0044] Step 3: Roll the Al-Mg-Sc alloy sheet after Step 2. The rolling deformation is maintained at 80%, the rolling temperature is 20℃, and the final rolled thickness of the sheet is 1.0 mm.

[0045] This embodiment of a high-strength, low-serration rheological 5xxx aluminum alloy sheet includes a heterogeneous layered structure, namely, a fine layer structure and a coarse layer structure distributed vertically. The fine layer structure is a mixed distribution of fine lamellar layers and subgrains, and the coarse layer structure is a mixed distribution of coarse lamellar layers and subgrains. In this experiment, the average width of the fine lamellar layers is approximately 4.5µm; the average width of the coarse lamellar layers is approximately 30µm. Figure 4 As shown, the subgrains are deformed grains with an orientation difference of less than 2°.

[0046] This embodiment describes a high-strength, low-serration rheological 5xxx aluminum alloy sheet, suitable for continuous production of large-size sheets, with a length ≥ 940 mm and a width ≥ 80 mm.

[0047] The application of the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment in a dynamic load-bearing component, the dynamic load-bearing component including a suspension control arm, a steering knuckle, a battery package shell / structural support, a UAV body structure / boom connecting piece, an industrial robot joint arm / link, an excavator / loader boom / dipper key connecting piece.

[0048] A dynamic load-bearing component is prepared from the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment.

[0049] The aluminum alloy plate obtained in the embodiment is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 390 MPa, the tensile strength is 407 MPa, and the elongation is 7.7%. Embodiment 2

[0050] According to the flowchart of the method shown in Figure 1 The material used is an Al-3Mg-0.25Sc (wt.%) alloy with a thickness of 5 mm.

[0051] Step 1: The Al-Mg-Sc alloy plate is subjected to primary annealing at 410℃ / 1h and secondary annealing at 450℃ / 1h, and is water quenched to room temperature.

[0052] Step 2: The Al-Mg-Sc alloy plate after step 1 processing is subjected to friction stir processing, the processing temperature is kept at 20℃, the rotation speed of the stirring head is 350 rpm, the travel speed of the stirring head is 80 mm / min, and the inclination angle of the stirring head is 1°.

[0053] Step 3: The Al-Mg-Sc alloy plate after step 2 processing is subjected to rolling deformation, and the rolling deformation amount is kept at 80%, and the rolling temperature is 20℃.

[0054] The aluminum alloy plate obtained in the embodiment is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 391 MPa, the tensile strength is 408 MPa, and the elongation is 7.5%.

[0055] The high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment includes a non-homogeneous layered structure, i.e., an upper and lower distribution of fine layer structure and coarse layer structure, the fine layer structure is a mixed distribution of fine lamella and subgrains, and the coarse layer structure is a mixed distribution of coarse lamella and subgrains. The average width of the fine lamella in the experiment is about 4.5µm; the average width of the coarse lamella in the experiment is about 30µm; and the subgrain is a deformed grain with an orientation difference of less than 2°.

[0056] The high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment is suitable for continuous production of large-size plates, and the length of the plate is ≥940mm and the width is ≥80mm.

[0057] This embodiment describes the application of high-strength, low-serration rheological 5xxx aluminum alloy sheet in dynamic load-bearing components, including suspension control arms, steering knuckles, battery pack housings / structural supports; UAV body structures / arm connectors, industrial robot articulated arms / links, and key connectors for excavator / loader booms / sticks.

[0058] A dynamic load-bearing component is prepared from a high-strength, low-serration rheological 5xxx aluminum alloy sheet according to this embodiment. Example 3

[0059] according to Figure 1 The flowchart shown is a schematic diagram of the method. The material used is an Al-3Mg-0.25Sc (wt.%) alloy with a thickness of 5 mm.

[0060] Step 1: Perform a first-stage annealing at 380℃ for 1 hour and a second-stage annealing at 430℃ for 1 hour on the Al-Mg-Sc alloy sheet, followed by water quenching to room temperature.

[0061] Step 2: Perform friction stir processing on the Al-Mg-Sc alloy sheet processed in Step 1. The processing temperature is maintained at 20℃, the stirring head rotation speed is 550rpm, the stirring head travel speed is 150mm / min, and the stirring head tilt angle is 1°.

[0062] Step 3: Roll the Al-Mg-Sc alloy sheet after Step 2, keeping the rolling deformation at 80% and the rolling temperature at 20℃.

[0063] The aluminum alloy sheet obtained in this embodiment was subjected to room temperature mechanical property tests, and the results are shown in Table 1. The yield strength was 389 MPa, the tensile strength was 408 MPa, and the elongation was 7.8%.

[0064] This embodiment presents a high-strength, low-serration rheological 5xxx aluminum alloy sheet, comprising a heterogeneous layered structure, namely, a fine layer structure and a coarse layer structure distributed vertically. The fine layer structure is a mixture of fine lamellar layers and subgrains, while the coarse layer structure is a mixture of coarse lamellar layers and subgrains. In this experiment, the average width of the fine lamellar layers is approximately 4.5 µm; the average width of the coarse lamellar layers is approximately 30 µm; and the subgrains are deformed grains with an orientation difference of less than 2°.

[0065] This embodiment describes a high-strength, low-serration rheological 5xxx aluminum alloy sheet, suitable for continuous production of large-size sheets, with a length ≥ 940 mm and a width ≥ 80 mm.

[0066] The application of the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment in a dynamic load-bearing component, the dynamic load-bearing component including a suspension control arm, a steering knuckle, a battery package shell / structural support; a UAV body structure / boom connecting piece, an industrial robot joint arm / link, an excavator / loader boom / dipper key connecting piece.

[0067] A dynamic load-bearing component is prepared from the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment. Embodiment 4

[0068] According to Figure 1 The flowchart of the method is shown, and the material used is an Al-3Mg-0.25Sc (wt.%) alloy with a thickness of 5 mm.

[0069] Step 1: The Al-Mg-Sc alloy plate is subjected to primary annealing at 380℃ / 1h and secondary annealing at 430℃ / 1h, and is water quenched to room temperature.

[0070] Step 2: The Al-Mg-Sc alloy plate after step 1 processing is subjected to friction stir processing, the processing temperature is kept at 25℃, the rotation speed of the stirring head is 350 rpm, the travel speed of the stirring head is 80 mm / min, and the inclination angle of the stirring head is 3°.

[0071] Step 3: The Al-Mg-Sc alloy plate after step 2 processing is subjected to rolling deformation, the rolling deformation amount is kept at 85%, and the rolling temperature is 25℃. The final rolling thickness of the plate is 0.75 mm.

[0072] The aluminum alloy plate obtained in the embodiment is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 391 MPa, the tensile strength is 409 MPa, and the elongation is 7.7%.

[0073] The high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment includes a non-homogeneous layered structure, i.e., an upper and lower distribution of fine layer structure and coarse layer structure, the fine layer structure is a mixed distribution of fine lamellar layer and subgrains, and the coarse layer structure is a mixed distribution of coarse lamellar layer and subgrains. The average width of the fine lamellar layer in the experiment is about 4.5µm; the average width of the coarse lamellar layer in the experiment is about 30µm; and the subgrain is a deformed grain with an orientation difference of less than 2°.

[0074] The high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment is suitable for continuous production of large-size plates, and the length of the plate is ≥940mm and the width is ≥80mm.

[0075] The application of the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment in a dynamic load-bearing component, the dynamic load-bearing component including a suspension control arm, a steering knuckle, a battery package shell / structural support; a UAV body structure / boom connecting piece, an industrial robot joint arm / link, an excavator / loader boom / dipper key connecting piece.

[0076] A dynamic load-bearing component is prepared from the high-strength low-serrated rheological 5xxx aluminum alloy plate of the embodiment.

[0077] Comparative Example 1

[0078] The material used is an Al-3Mg-0.25Sc alloy with a thickness of 5 mm. The Al-Mg-Sc alloy plate is subjected to primary annealing at 380℃ / 1h and secondary annealing at 430℃ / 1h, and water quenching to room temperature.

[0079] The difference between this comparative example and Example 1 is that no friction stir processing and rolling deformation are performed.

[0080] The aluminum alloy plate obtained in this comparative example is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 106 MPa, the tensile strength is 202 MPa, and the elongation is 19.8%.

[0081] Comparative Example 2

[0082] The material used is an Al-3Mg-0.25Sc alloy with a thickness of 5 mm. The Al-Mg-Sc alloy plate is subjected to primary annealing at 380℃ / 1h and secondary annealing at 430℃ / 1h, and water quenching to room temperature. The processed Al-Mg-Sc alloy plate is subjected to single-pass room temperature friction stir processing, the processing temperature is kept at 20℃, the rotation speed of the stirring head is 350 rpm, the travel speed of the stirring head is 80 mm / min, and the inclination angle of the stirring head is 1°.

[0083] The difference between this comparative example and Example 1 is that no rolling deformation is performed.

[0084] The aluminum alloy plate obtained in this comparative example is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 169 MPa, the tensile strength is 299 MPa, and the elongation is 22.4%.

[0085] Comparative Example 3

[0086] The material used is Al-3Mg-0.25Sc alloy with a thickness of 5 mm. The Al-Mg-Sc alloy sheet is subjected to a primary annealing treatment at 380°C / 1 h and a secondary annealing treatment at 430°C / 1 h, and is water quenched to room temperature. The treated Al-Mg-Sc alloy sheet is subjected to single-pass cryogenic friction stir processing at a processing temperature of -150°C, a stirring head rotation speed of 350 rpm, a stirring head travel speed of 80 mm / min, and a stirring head tilt angle of 1°.

[0087] That is, the difference between the present comparative example and Example 1 is that the room temperature friction stirring of Example 1 is replaced by cryogenic friction stirring at -150°C, and the present comparative example is not subjected to rolling deformation.

[0088] The aluminum alloy sheet obtained in the present comparative example is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 225 MPa, the tensile strength is 395 MPa, and the elongation is 18.5%.

[0089] Comparative Example 4

[0090] The material used is Al-3Mg-0.25Sc alloy with a thickness of 5 mm. The Al-Mg-Sc alloy sheet is subjected to a primary annealing treatment at 380°C / 1 h and a secondary annealing treatment at 430°C / 1 h, and is water quenched to room temperature. The treated Al-Mg-Sc alloy sheet is subjected to single-pass room temperature friction stir processing at a processing temperature of 20°C, a stirring head rotation speed of 350 rpm, a stirring head travel speed of 80 mm / min, and a stirring head tilt angle of 1°. The treated Al-Mg-Sc alloy sheet is subjected to rolling deformation, and the rolling deformation amount is maintained at 50%, and the rolling temperature is 20°C.

[0091] The aluminum alloy sheet obtained in the present comparative example is subjected to room temperature mechanical property testing, and the results are shown in Table 1, wherein the yield strength is 302 MPa, the tensile strength is 335 MPa, and the elongation is 5.8%.

[0092] Comparative Example 5

[0093] The material used is Al-3Mg-0.25Sc alloy with a thickness of 5 mm. The Al-Mg-Sc alloy sheet is subjected to a primary annealing treatment at 380°C / 1 h and a secondary annealing treatment at 430°C / 1 h, and is water quenched to room temperature. The treated Al-Mg-Sc alloy sheet is subjected to rolling deformation, and the rolling deformation amount is maintained at 80%, and the rolling temperature is 20°C.

[0094] That is, the difference between the present comparative example and Example 1 is that no friction stir processing is performed.

[0095] The aluminum alloy plate obtained by the above comparative example was subjected to room temperature mechanical property test, and the results are shown in Table 1, wherein the yield strength is 340 MPa, the tensile strength is 354 MPa, and the elongation is 3.0%.

[0096] The room temperature mechanical property test was carried out on the aluminum alloy plates of all the above examples and comparative examples, and the test method adopted the national standard GB / T228.1-2010, and the results are shown in Table 1. The sawtooth average amplitude of the mechanical property data of the aluminum alloy plates of the above example 1 and comparative examples 2-4 was quantitatively counted, and all the stress drops from yield to fracture of each group of samples were counted, and the results are shown in Table 2.

[0097] Table 1 Mechanical properties of examples and comparative examples

[0098]

[0099] Table 2 Sawtooth average amplitude of examples and comparative examples

[0100]

[0101] Performance analysis:

[0102] In combination with Figure 5 and Table 2, by comparing example 1 and comparative examples 2-4, it can be seen that the present application reduces the sawtooth average amplitude to 0.28 MPa (measured value) under the condition of large strain rolling by the three-level synergy of "double annealing-stir friction pretreatment-80% or more large strain rolling" (example 1), which is reduced by 93% compared with the conventional stir friction processing process (4.3 MPa, comparative example 2), reduced by 92% compared with the cryogenic stir friction processing process (3.6 MPa, comparative example 3), and reduced by 74.4% compared with the stir friction processing combined with medium rolling deformation process (1.1 MPa, comparative example 4). The effect proves that the synergy of large rolling amount (80%-85%) and FSP pretreatment has an extremely inhibitory effect on sawtooth rheology, and solves the problem of plastic instability caused by dislocation-solute interaction out of control under the condition of high strength and large deformation of 5xxx aluminum alloy.

[0103] In combination with Figure 2By comparing Example 1 and Comparative Examples 1-5, it can be seen that the present invention achieves a high yield strength of 390 MPa, an elongation of 7.7%, and an extremely low serration amplitude of 0.28 MPa in 5xxx aluminum alloy through the triple synergistic control of annealing-FSP-rolling (Example 1). Compared with the cryogenic stirring friction process (Comparative Example 3: yield strength 225 MPa / serration amplitude 3.6 MPa), the yield strength is increased by 73% and the serration suppression efficiency is increased by 92%. Compared with the traditional 80% cold rolling (Comparative Example 5: yield strength 340 MPa / elongation 3.0%), the strength is further increased by 14%, while the plasticity is increased by 2.5 times and the risk of high serration rheology is significantly reduced, successfully solving the irreconcilable triangle problem of "high strength, good plasticity and low serration rheology".

[0104] The high strength, good plasticity, and low serrated rheological properties are achieved because this invention utilizes a combined process of friction stir pretreatment and large deformation rolling to obtain a special heterogeneous layered structure in the alloy, such as... Figure 3 The image shown is a photograph of a heterogeneous layered tissue structure from Example 1, which contains two distinctly different characteristic structures (such as...). Figure 3 (a) Structures I and II are shown, as in Figure 3 Structure I shown in (c) is a mixed distribution of fine lamellar layers and subgrains, such as Figure 3 (b) shows another structure, namely structure II, which is a mixed distribution of coarse lamellae and subgrains. That is, structure I is a fine-layered structure, and structure II is a coarse-layered structure. The structural heterogeneity is mainly reflected in the lamellar width and lamellar distribution, such as Figure 3 As shown in (d), this is a schematic diagram of the fine-layered and coarse-layered structures. Furthermore, under the process of this invention, the transmission electron microscopy of the alloy reveals a regular arrangement of dislocations, such as... Figure 6 As shown, Example 1 is a precursor to dislocation rearrangement and polygonization, corresponding to a heterogeneous layered structure. In contrast, the alloy in Comparative Example 5, which did not undergo friction stir pretreatment, exhibits a large number of dislocation entanglements, which is highly detrimental to the alloy's plasticity. Therefore, due to this special heterogeneous layered structure and the microstructure with regularly arranged dislocations, the high density of geometrically necessary dislocations after rolling deformation is concentrated at the lamellar, large-angle grain boundaries. The more lamellar layers there are, the higher the back stress effect. The generation, movement, and accumulation of geometrically necessary dislocations related to back stress strengthening constitute additional strain hardening and are an important component of total strain hardening. Therefore, Examples 1-4, under the combined process of friction stir pretreatment and large deformation rolling, achieved a high yield strength of 389~391 MPa, an elongation of 7.5%~7.8%, and an extremely low serration amplitude of 0.28 MPa.

[0105] It should be understood that, for brevity and clarity sake, in the foregoing description of the exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description of related features. However, this method of disclosure should not be interpreted as reflecting an intention that the application requires more features than are explicitly recited in each claim. Rather, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the following claims are hereby expressly incorporated into this detailed description, with each claim acting as a separate embodiment of the application. In closing, the claims are what define the scope of the application. Therefore, the specific embodiments described in the specification are not to be construed as limiting the scope of the application. The scope of the application is to be determined by the claims.

[0106] While the application has been described in terms of several embodiments, those skilled in the art will recognize that the application can be practiced with modifications and alterations limited only by the spirit and scope of the claims. Additionally, although the present technology has been described above in terms of specific embodiments, it is anticipated that alternatives, modifications and variations of the application will become apparent to those skilled in the art on the basis of the teachings set forth herein. Accordingly, the particular embodiments described in detail herein are shown by way of example only and are not meant to limit the scope of the application. Numerous variations, additions, and omissions will be apparent to one of ordinary skill in the art in light of the above teachings. Therefore, the scope of the application is to be limited only by the following claims.

[0107] The above description is intended to be illustrative and not restrictive. Many modifications and variations of the application will be apparent to those skilled in the art from this teaching without departing from the spirit or scope of the application. Accordingly, particular embodiments of the present application are provided for the purpose of illustration and description, and not intended to limit the scope of the application, which is defined by the following claims.

Claims

1. A method for preparing a high-strength, low-serration rheological 5xxx aluminum alloy sheet, characterized in that, Includes the following steps: Step 1: Perform a two-stage high-temperature annealing pretreatment on the 5xxx aluminum alloy sheet; the first-stage annealing temperature is 380~410℃, the holding time is 1h, and then it is quenched to room temperature by water; the second-stage annealing temperature is 430~450℃, the holding time is 1h, and then it is quenched to room temperature by water. Step 2: Perform friction stir processing on the 5xxx aluminum alloy sheet processed in Step 1; The friction stir processing equipment processes the 5xxx aluminum alloy sheet, the processing temperature is maintained at 20℃~25℃, the rotation speed of the stirring head is 350rpm~550rpm, the travel speed is controlled at 80mm / min~150mm / min, and the tilt angle of the stirring head is 1°~3°. Step 3: Roll the 5xxx aluminum alloy sheet processed in Step 2; maintain the rolling temperature at 20℃~25℃ and the total rolling deformation at 80%~85%; 5xxx aluminum alloy sheets are Al-Mg-Sc alloys. The Al-Mg-Sc alloy contains the following components by mass percentage: Mg: 3%, Sc: 0.25%, and the balance Al. The average amplitude of the saw teeth on the plate is 0.28 MPa, the elongation is ≥7.5%, the yield strength is ≥389 MPa, and the tensile strength is ≥407 MPa. The sheet material includes a heterogeneous layered structure, namely a fine layered structure and a coarse layered structure distributed vertically. The fine layered structure is a mixture of fine lamellar layers and subgrains, and the coarse layered structure is a mixture of coarse lamellar layers and subgrains. The width of the fine lamellae layer is less than 10µm; the width of the coarse lamellae layer is greater than 10µm. Subgrains are deformed grains with an orientation difference of less than 2°; The heterogeneous layered structure promotes dislocation accumulation at the soft / hard interface during soft deformation, inducing back stress. The measured back stress value is ≥100 MPa, which enhances the work hardening ability.

2. The preparation method according to claim 1, characterized in that, In step 2, the stirring head is a conical needle.

3. The preparation method according to claim 1, characterized in that, In step 3, the reduction rate of each rolling pass is maintained at 10%.

4. A high-strength, low-serration rheological 5xxx aluminum alloy sheet obtained by the preparation method according to any one of claims 1 to 3, characterized in that, The average amplitude of the saw teeth on the plate is 0.28 MPa, the elongation is ≥7.5%, the yield strength is ≥389 MPa, and the tensile strength is ≥407 MPa.

5. A high-strength, low-serration rheological 5xxx aluminum alloy sheet according to claim 4, characterized in that, It includes heterogeneous layered structures, namely fine-layered structures and coarse-layered structures distributed vertically. Fine-layered structures are a mixture of fine lamellars and subgrains, while coarse-layered structures are a mixture of coarse lamellars and subgrains.

6. The high-strength, low-serration rheological 5xxx aluminum alloy sheet according to claim 5, characterized in that, The width of the fine lamellae layer is less than 10µm; the width of the coarse lamellae layer is greater than 10µm. Subgrains are deformed grains with an orientation difference of less than 2°.

7. A high-strength, low-serration rheological 5xxx aluminum alloy sheet according to claim 4, characterized in that, The length of the board is ≥940mm and the width is ≥80mm.

8. The application of a high-strength, low-serration rheological 5xxx aluminum alloy sheet according to any one of claims 4 to 7 in dynamic load-bearing components, characterized in that, Dynamic load-bearing components include suspension control arms and steering knuckles.

9. A dynamic load-bearing component, characterized in that, The high-strength, low-serration rheological 5xxx aluminum alloy sheet is prepared according to any one of claims 4 to 7.

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