Al-mg-zn-mn alloy, method for producing the same, and alloy member

Abstract

This invention relates to the field of metallic materials technology, and in particular to an Al-Mg-Zn-Mn alloy, its preparation method, and alloy parts. The Al-Mg-Zn-Mn alloy, by mass percentage, comprises: Mg 3.5%–8%, Zn 0.1%–2%, Mn 0.5%–1.5%, Ti ≤0.02%, with the remainder being Al and unavoidable impurities. This invention introduces appropriate amounts of Mg, Zn, and Mn into the alloy. Furthermore, through heat treatment, the synergistic effect of the T-phase substitution mechanism at grain boundaries and the induction of Mg element aggregation and precipitation within the grains by Al6Mn as a pre-existing compound particle of the T-phase, the content of the T-phase precipitate at grain boundaries is reduced, thus decreasing the continuous precipitation of the T-phase at grain boundaries and improving the overall performance and corrosion resistance of the alloy.

Description

Technical Field

[0001] This invention relates to the field of metallic materials technology, and in particular to an Al-Mg-Zn-Mn alloy, its preparation method, and alloy parts. Background Technology

[0002] Al-Mg alloys are widely used as lightweight alternatives to steel due to their high strength-to-weight ratio, excellent formability, and weldability. However, for Al-Mg alloys with a Mg content exceeding 3.5%, when exposed to seawater or other corrosive environments, Al3Mg2 (β phase) preferentially precipitates continuously or nearly continuously at grain boundaries during sensitization treatment. The potential difference between these precipitated β phases and the aluminum matrix forms galvanic cells in these special environments, leading to severe corrosion of the β phase at the grain boundaries and thus shortening the service life of the material. Existing research has found that adding Zn to Al-Mg alloys, under strict control of the Zn addition amount, will form a new ternary phase, Mg. 32 (Al,Zn) 49 The T phase replaces the original β phase, resulting in a smaller potential difference between the new precipitated T phase and the matrix, which improves corrosion resistance. However, the addition of Zn can also cause the T phase to precipitate continuously at grain boundaries, leading to a deterioration in corrosion resistance. Therefore, controlling the precipitation of the T phase is crucial. Furthermore, the strength improvement effect of the T phase on the alloy is limited by the amount of Zn added. To further improve the strength of Al-Mg-Zn alloys, existing studies have introduced Cu to improve overall performance through alloy hardening. However, in the Al-Mg-Zn alloy system, excessively high Cu content significantly increases corrosion susceptibility, leading to a sharp decline in the alloy's corrosion resistance.

[0003] Furthermore, the formation of the β phase increases with increasing Mg content in the alloy. As a brittle phase, the β phase significantly reduces the toughness of the alloy, thereby leading to poorer processing properties, especially casting and rolling properties.

[0004] Therefore, there is an urgent need to develop an Al-Mg-Zn alloy that can combine high strength, high corrosion resistance, and good processability.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an Al-Mg-Zn-Mn alloy, its preparation method, and alloy parts. By introducing appropriate amounts of Mg, Zn, and Mn into the alloy, the microstructure and the precipitation of phases at grain boundaries are controlled, thereby improving the overall mechanical properties, corrosion resistance, and processability of the alloy.

[0007] To achieve the above-mentioned objectives of the present invention, the first aspect of the present invention provides an Al-Mg-Zn-Mn alloy comprising, by mass percentage: Mg 3.5% to 8%, Zn 0.1% to 2%, Mn 0.5% to 1.5%, Ti ≤ 0.02%, with the remainder being Al and unavoidable impurities.

[0008] In a specific embodiment of the present invention, the Al-Mg-Zn-Mn alloy contains, by mass percentage, Fe ≤ 0.25%, Si ≤ 0.1%, Cu ≤ 0.05%, and Cr ≤ 0.12%.

[0009] In a specific embodiment of the present invention, the mass percentage of Mg in the alloy is 4% to 8%, preferably 4.5% to 8%.

[0010] In a specific embodiment of the present invention, the mass percentage of Zn in the alloy is 0.4% to 1%, preferably 0.45% to 0.8%.

[0011] The second aspect of the present invention provides a method for preparing an Al-Mg-Zn-Mn alloy according to the first aspect, comprising the following steps: preparing materials according to the composition of the Al-Mg-Zn-Mn alloy, melting and casting to obtain an alloy ingot.

[0012] In a specific embodiment of the present invention, the preparation method further includes: heat treatment of the alloy ingot; the heat treatment includes: holding at 400±5℃ for 4 to 6 hours, then raising the temperature to 425±5℃ and holding for 1 to 3 hours, and then raising the temperature to 450±5℃ and holding for 2 to 4 hours.

[0013] In a specific embodiment of the present invention, the preparation method further includes: deforming the heat-treated alloy ingot and then performing a graded annealing treatment. Further, the graded annealing treatment includes: first holding at 350±5℃ for 1–3 hours, and then holding at 200℃±5℃ for 1–3 hours.

[0014] In a specific embodiment of the present invention, the deformation process includes hot rolling deformation. Further, the hot rolling deformation includes: holding at 400–420°C for 1–3 hours, followed by hot rolling. The deformation amount per pass is ≤10%.

[0015] The third aspect of the present invention provides an Al-Mg-Zn-Mn alloy part prepared by the preparation method of the second aspect.

[0016] In a specific embodiment of the present invention, the tensile strength of the Al-Mg-Zn-Mn alloy part is ≥450MPa, the yield strength is ≥380MPa, and the elongation is ≥12%.

[0017] In a specific embodiment of the present invention, the self-corrosion potential of the Al-Mg-Zn-Mn alloy component in a 3.5wt% NaCl aqueous solution at 25°C is -1.43 to -1.24 V, and the self-corrosion current density is -6.9 to -5.5 A / cm². 2 .

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The alloy of the present invention introduces appropriate amounts of Mg, Zn and Mn. Under the synergistic effect of the T phase substitution mechanism at the grain boundary and the induction of Mg element to aggregate and precipitate in the grain by Al6Mn as a pre-existing compound particle of T phase, the content of T phase precipitates at the grain boundary is reduced, the continuous precipitation of T phase at the grain boundary is reduced, and the precipitation of β phase in the grain is induced, thereby improving the overall performance, corrosion resistance and processability of the alloy.

[0020] (2) By performing appropriate annealing treatment on the alloy, the T phase is partially dissolved and then precipitated, and the distribution of the T phase in the alloy is readjusted, which significantly improves the problem of continuous precipitation of the T phase at the grain boundary and makes it precipitate in the grain, thereby increasing the matrix strength and improving the corrosion resistance. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 The as-cast microstructures of the Al-Mg-Zn-Mn alloys provided in Examples 1-3 of this invention;

[0023] Figure 2 EDS composition analysis results for four marked points corresponding to the Al-Mg-Zn-Mn alloy provided in Example 1 of this invention;

[0024] Figure 3 The SEM microstructure of the Al-Mg-Zn-Mn alloy provided in Example 1 of this invention after heat treatment;

[0025] Figure 4 These are TEM images of Al-Mg-Zn-Mn alloy plates provided in Examples 1-3 of the present invention at the same magnification; wherein (a) to (c) correspond to Examples 1-3, respectively.

[0026] Figure 5The distribution of precipitated phases at grain boundaries in Al-Mg-Zn-Mn alloy plates provided in Examples 1 to 3 of the present invention is shown; wherein (a) to (c) correspond to Examples 1 to 3, respectively.

[0027] Figure 6 TEM images of the Al-Mg-Zn-Mn alloy plate provided in Example 2 of the present invention before (a) and after (b) annealing treatment;

[0028] Figure 7 The mechanical property test results and Tafel curves of Al-Mg-Zn-Mn alloy plates in the embodiments and comparative examples of the present invention are shown. Detailed Implementation

[0029] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0030] The first aspect of the present invention provides an Al-Mg-Zn-Mn alloy comprising, by mass percentage: Mg 3.5%–8%, Zn 0.1%–2%, Mn 0.5%–1.5%, Ti ≤0.02%, with the remainder being Al and unavoidable impurities.

[0031] The alloy of this invention incorporates an appropriate amount of Mn. Mn primarily enhances the mechanical properties of the alloy through dispersion strengthening and solid solution hardening. In the as-cast alloy of this invention, Al6Mn exists as a refractory phase. The pre-existing compound particles of the T phase induce partial aggregation and precipitation of the T phase within the grains, increasing matrix strength and reducing the content of T phase precipitates at grain boundaries, thereby improving the overall mechanical properties and corrosion resistance of the alloy. Furthermore, the addition of Mn further refines the as-cast microstructure of the Al-Mg-Zn-Mn alloy, reducing the grain size of the as-cast microstructure. Moreover, Mn is low in cost, significantly reducing the overall cost of the alloy. The Zn element forms a T phase within the alloy, which replaces the β phase, a common precipitate at grain boundaries in Al-Mg alloys. The T phase substitution mechanism at grain boundaries and the synergistic effect of Al6Mn as a pre-existing compound particle of the T phase inducing the aggregation and precipitation of Mg within the grains reduce the content of T phase precipitates at grain boundaries and induce the precipitation of the β phase within the grains, thereby improving the overall performance, corrosion resistance, and processing properties of the alloy.

[0032] In different embodiments, the Al-Mg-Zn-Mn alloy may contain Mg in the range of 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, 7%, 7.5%, 8%, or any combination thereof, by mass percentage; Zn may contain 0.1%, 0.3%, 0.5%, 0.8%, 1%, 1.2%, 1.5%, 1.8%, 2%, or any combination thereof; and Mn may contain 0.5%, 0.8%, 1%, 1.2%, 1.5%, or any combination thereof.

[0033] Research has found that the use of a certain amount of Mn in the alloy of this invention can simultaneously improve the alloy's corrosion resistance and mechanical properties. Specifically, the invention uses a certain amount of Mn, and Al6Mn, as a sparingly soluble phase, is present in the alloy after casting. Furthermore, the Al6Mn phase, as a pre-existing compound particle of the T phase, affects the precipitation behavior of the T phase during annealing, causing the T phase to nucleate at the interface of the pre-existing compound particles within the grains, reducing its content in the precipitated phase at the grain boundaries, decreasing the continuous precipitation of the T phase at the grain boundaries, reducing the potential difference between the precipitated phase at the grain boundaries and the Al matrix, and improving the stability of the grain boundaries. Further research revealed that when the Mn content is too low, the amount of Al6Mn phase precipitated within the grains is insufficient. As the amount of Al6Mn phase decreases, the T phase preferentially precipitates at the grain boundaries, resulting in a large number of continuously precipitated T phases at the grain boundaries, which leads to poor corrosion resistance. When the Mn content is too high, it increases the possibility of Al6Mn phase precipitation at the grain boundaries, causing a rapid deterioration in the rollability of the alloy, resulting in a large number of cracks during rolling, and at the same time, the intergranular corrosion resistance deteriorates.

[0034] In specific embodiments of the present invention, the Ti content in the Al-Mg-Zn-Mn alloy can be 0%, 0.001%, 0.005%, 0.01%, 0.015%, 0.02%, or any combination thereof. In practice, during the smelting process of the Al-Mg-Zn-Mn alloy, an appropriate Al-Ti-B refining agent can be added to refine the alloy as needed, which may introduce trace amounts of Ti. The specific Ti content is not limited, but it should not exceed 0.02%.

[0035] In a specific embodiment of the present invention, in the Al-Mg-Zn-Mn alloy, by mass percentage, Fe≤0.25%, Si≤0.1%, Cu≤0.05%, and Cr≤0.12%.

[0036] In a specific embodiment of the present invention, the mass percentage of Mg in the alloy is 4% to 8%, preferably 4.5% to 8%.

[0037] In a specific embodiment of the present invention, the mass percentage of Zn in the alloy is 0.4% to 1%, preferably 0.45% to 0.8%.

[0038] The second aspect of the present invention provides a method for preparing an Al-Mg-Zn-Mn alloy according to the first aspect, comprising the following steps: preparing materials according to the composition of the Al-Mg-Zn-Mn alloy, melting and casting to obtain an alloy ingot.

[0039] Al, Mg, and Zn elements are introduced through pure aluminum, pure magnesium, and pure zinc, respectively, while Mn element is introduced through an Al-Mn master alloy, such as an Al-20Mn master alloy.

[0040] In practice, the smelting process can be carried out in a vacuum resistance furnace, and the specific smelting method can refer to the smelting method of conventional Al-Mg-Zn-Mn alloys.

[0041] In a specific embodiment of the present invention, the melting temperature is 740–760°C.

[0042] In a specific embodiment of the present invention, the preparation method further includes: heat treatment of the alloy ingot; the heat treatment includes: holding at 400±5℃ for 4 to 6 hours, then raising the temperature to 425±5℃ and holding for 1 to 3 hours, and then raising the temperature to 450±5℃ and holding for 2 to 4 hours.

[0043] In the heat treatment, the holding time at 400±5℃ can be 4h, 5h, or 6h, the holding time at 425±5℃ can be 1h, 2h, or 3h, and the holding time at 450±5℃ can be 2h, 3h, or 4h. The heating process is carried out in a furnace, specifically with a heating rate of 35–45℃ / h for heating from 400±5℃ to 420±5℃ and from 425±5℃ to 450±5℃, for example, 40℃ / h. This heat treatment ensures more uniform precipitation of the remaining Mn element within the crystal.

[0044] In a specific embodiment of the present invention, after the above-mentioned heat treatment, water quenching is performed.

[0045] In a specific embodiment of the present invention, the preparation method further includes: deforming the heat-treated alloy ingot and then annealing it. Further, the annealing process includes: first holding at 350±5℃ for 1–3 hours, and then holding at 200℃±5℃ for 1–3 hours.

[0046] This invention anneales the deformed alloy parts to fully release residual stress within the material, improving the uniformity and stability of the material's microstructure. Furthermore, through appropriate annealing, the T-phase partially dissolves and then precipitates again, readjusting its distribution within the alloy and significantly improving the problem of continuous T-phase precipitation at grain boundaries. This allows the T-phase to precipitate within the grains, increasing the matrix strength. For example, in different embodiments, the holding time at 350±5℃ can be 1h, 2h, 3h, etc., and the holding time at 200±5℃ can be 1h, 2h, 3h, etc.

[0047] In specific embodiments of the present invention, the deformation processing method includes, but is not limited to, hot rolling deformation, and can be conventionally adjusted according to actual application requirements. For example, when it is necessary to prepare alloy plates, hot rolling deformation can be used. Specific hot rolling deformation includes: holding at 400-420℃ for 1-3 hours for hot rolling processing. The reduction amount per pass is ≤10%.

[0048] The third aspect of the present invention provides an Al-Mg-Zn-Mn alloy part prepared by the preparation method of the second aspect.

[0049] In a specific embodiment of the present invention, the average size of the precipitated phase (Al6Mn phase) in the Al-Mg-Zn-Mn alloy is 0.2 to 0.55 μm, for example, it can be a range of 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.55 μm or any combination thereof.

[0050] In specific embodiments of the present invention, the tensile strength of Al-Mg-Zn-Mn alloy parts is ≥450 MPa, for example, it can be within the range of 450 MPa, 455 MPa, 460 MPa, 465 MPa, 470 MPa, 474 MPa, or any combination thereof; the yield strength is ≥380 MPa, for example, it can be within the range of 380 MPa, 385 MPa, 390 MPa, 395 MPa, 400 MPa, 405 MPa, 410 MPa, 416 MPa, or any combination thereof; the elongation is ≥12%, for example, it can be within the range of 12%, 12.5%, 13%, 13.5%, 14%, 14.1%, or any combination thereof. The mechanical properties of alloy parts prepared using the alloy composition and preparation method of the present invention are significantly improved.

[0051] In a specific embodiment of the present invention, the self-corrosion potential of Al-Mg-Zn-Mn alloy parts in a 3.5wt% NaCl aqueous solution at 25°C is -1.43 to -1.24 V, and the self-corrosion current density is -6.9 to -5.5 A / cm². 2 .

[0052] Example 1

[0053] This embodiment provides an Al-Mg-Zn-Mn alloy, comprising by mass percentage: Mg 4.5%, Zn 0.5%, Mn 0.5%, Ti ≤ 0.02%, Fe ≤ 0.25%, Si ≤ 0.1%, Cu ≤ 0.05%, Cr ≤ 0.12%, with the remainder being Al and unavoidable impurities.

[0054] The preparation method of the Al-Mg-Zn-Mn alloy in this embodiment includes the following steps:

[0055] (1) Pure aluminum, pure magnesium, pure zinc, and Al-20Mn are added to a vacuum resistance furnace containing molten pure aluminum according to the composition of the Al-Mg-Zn-Mn alloy. The temperature is raised to 750℃ and held until melted. A suitable amount of conventional Al-5Ti-B refining agent is added, and the mixture is stirred evenly and allowed to stand for 30 minutes. Then the melt is poured into a mold with dimensions of 30mm×80mm×30mm and cooled to room temperature to obtain an alloy ingot.

[0056] (2) The alloy ingot is held at 400℃ for 5 hours, then heated to 425℃ with the furnace at a heating rate of 40℃ / h and held for 2 hours, then heated to 450℃ with the furnace at a heating rate of 40℃ / h and held for 3 hours, and finally placed in cold water for quenching to preserve the internal morphology of the alloy.

[0057] (3) Heat the alloy ingot after heat treatment in step (2) to 420°C and hold for 2 hours, and then perform multiple hot rolling processes. During the hot rolling process, the amount of pressure in each pass is 3 mm, and the alloy ingot with an initial thickness of 30 mm is gradually rolled thin to obtain a plate with a thickness of 3 mm.

[0058] (4) Heat the plate obtained in step (3) to 350°C for 1 hour of annealing, and then anneal at 200°C for 3 hours.

[0059] Example 2

[0060] This embodiment refers to the Al-Mg-Zn-Mn alloy and its preparation method in Example 1, the only difference being that the composition of the Al-Mg-Zn-Mn alloy is different.

[0061] The Al-Mg-Zn-Mn alloy of this embodiment comprises, by mass percentage: Mg 4.5%, Zn 0.5%, Mn 1.0%, Ti≤0.02%, Fe≤0.25%, Si≤0.1%, Cu≤0.05%, Cr≤0.12%, with the remainder being Al and unavoidable impurities.

[0062] Example 3

[0063] This embodiment refers to the Al-Mg-Zn-Mn alloy and its preparation method in Example 1, the only difference being that the composition of the Al-Mg-Zn-Mn alloy is different.

[0064] The Al-Mg-Zn-Mn alloy of this embodiment comprises, by mass percentage: Mg 4.5%, Zn 0.5%, Mn 1.5%, Ti≤0.02%, Fe≤0.25%, Si≤0.1%, Cu≤0.05%, Cr≤0.12%, with the remainder being Al and unavoidable impurities.

[0065] Example 4

[0066] This embodiment refers to the Al-Mg-Zn-Mn alloy and its preparation method in Example 1. The only difference is that the heat treatment in step (2) of the preparation method of the Al-Mg-Zn-Mn alloy is different.

[0067] Step (2) of this embodiment includes: holding the alloy ingot at 450°C for 8 hours, and then directly quenching it in cold water.

[0068] Example 5

[0069] This embodiment refers to the Al-Mg-Zn-Mn alloy and its preparation method in Example 2. The only difference is that the heat treatment in step (2) of the preparation method of the Al-Mg-Zn-Mn alloy is different.

[0070] Step (2) of this embodiment includes: holding the alloy ingot at 450°C for 8 hours, and then directly quenching it in cold water.

[0071] Comparative Example 1

[0072] Comparative Example 1 refers to the Al-Mg-Zn-Mn alloy and its preparation method in Example 1, the difference being that the composition of the Al-Mg-Zn-Mn alloy is different.

[0073] The Al-Mg-Zn-Mn alloy of Comparative Example 1, by mass percentage, includes: Mg 4.5%, Zn 0.5%, Mn 0.1%, Ti≤0.02%, Fe≤0.25%, Si≤0.1%, Cu≤0.05%, Cr≤0.12%, with the remainder being Al and unavoidable impurities.

[0074] Experimental Example 1

[0075] Multiple samples with dimensions of 10 mm × 10 mm × 10 mm were taken from the rolled plates and ingots (as-cast state) of Examples 1 to 3, and characterized and analyzed by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Figure 1 The as-cast microstructures of the Al-Mg-Zn-Mn alloys provided in Examples 1-3 of this invention were analyzed statistically to obtain the variation trend of the average grain size of the as-cast alloys under different Mn contents. Figure 1 As can be seen, with the increase of Mn content from 0.5% to 1.5%, the grain size of the as-cast structure decreased significantly, indicating that the addition of an appropriate amount of Mn has a significant grain refining effect on the alloy. SEM observation revealed a small amount of precipitates in the shape of Chinese characters in the matrix. EDS compositional analysis results for the four marked points of the Al-Mg-Zn-Mn alloy provided in Example 1 are as follows: Figure 2 As shown, the results reveal the elemental composition at the marked locations, confirming that these precipitates are composed of Al6(Mn,Fe) and Al6Mn phases, with no obvious Mg signal detected. Figure 3 The SEM microstructure of the Al-Mg-Zn-Mn alloy provided in Example 1 of this invention after heat treatment in step (2) shows a typical elongated Al6Mn phase.

[0076] Figure 4 These are TEM images of the Al-Mg-Zn-Mn alloy sheets (rolled state) provided in Examples 1-3 of this invention, at the same magnification. Statistical analysis shows that the average precipitated phase sizes in the alloy sheets obtained in Examples 1-3 are 0.517 μm, 0.332 μm, and 0.288 μm, respectively. Figure 4In (a), elongated precipitates dominated by Al6Mn and a small amount of disc-shaped precipitates can be observed, while a large amount of Mg is visible at the grain boundaries. 32 (AlZn) 49 Phase precipitation; as the Mn content increases, from Figure 4 In (b), it can be observed that the amount of Al6Mn phase increases significantly, while the size of the precipitated phase gradually decreases; when the Mn content further increases, from Figure 4 In (c), it can be observed that the size of the precipitated phase does not change significantly, but the amount increases significantly.

[0077] Figure 5 The distribution of precipitated phases at grain boundaries in the Al-Mg-Zn-Mn alloy plates (annealed state) provided in Examples 1-3 of this invention is shown in the figures. As can be seen from the figures, when the Mn content is low, no Mn enrichment was observed near the grain boundaries; only Mg was found on the grain boundaries. 32 (AlZn) 49 Phase. As the Mn content increases to 1.0%, it is evident that Mn elements gradually migrate towards the grain boundaries and appear as pre-existing compounds; at this point, Mg... 32 (AlZn) 49 The phase uses Al6Mn as the nucleation site, exhibiting heterogeneous nucleation. When the Mn content continues to increase to 1.5%, more Al6Mn phase can be observed on the grain boundaries.

[0078] Figure 6 The images show TEM images of the Al-Mg-Zn-Mn alloy sheet provided in Example 2 of this invention before and after annealing. As can be seen from the images, before annealing, the precipitates are continuously precipitated under high magnification TEM. After annealing, the precipitates no longer exhibit a continuous precipitate form under low magnification TEM. This indicates that the continuous precipitation problem of grain boundary precipitates in the alloy of this invention is significantly improved after appropriate annealing.

[0079] Experiment Example 2

[0080] The room temperature tensile properties of alloy sheets from different embodiments and comparative examples were tested, and the test results are shown in [Figure number missing]. Figure 7 (a) and Table 1.

[0081] Table 1. Test results of mechanical properties of different alloy plates

[0082] serial number Tensile strength (MPa) Yield strength (MPa) Elongation (%) Example 1 454 389 12.8 Example 2 461 416 14.1 Example 3 474 404 14.0 Example 4 370 313 14.1 Example 5 405 331 14.1 Comparative Example 1 389 316 14.1

[0083] Further electrochemical corrosion performance (Tafel test) of alloy plate samples from different embodiments and comparative examples was tested in a 3.5 wt% NaCl aqueous solution at 25°C. The test results are shown in [Figure number missing]. Figure 7 (b) and Table 2.

[0084] Table 2. Electrochemical corrosion performance test results of different alloy plates

[0085] serial number Self-corrosion potential (V) <![CDATA[Self - corrosion current (A / cm 2 )]]> Example 1 -1.248 -6.833 Example 2 -1.427 -6.126 Example 3 -1.279 -5.564 Example 4 -1.08 -8.462 Example 5 -1.204 -5.723 Comparative Example 1 -1.125V -6.608

[0086] The test results above show that by introducing an appropriate amount of Mn into the alloy and combining it with certain heat treatment, the present invention, through the synergistic effect of the T-phase substitution mechanism at the grain boundaries and the induction of Mg element aggregation and precipitation within the grains by Al6Mn as a pre-existing compound particle of the T-phase, draws the precipitates on the grain boundaries into the grains, reduces the content of the T-phase precipitates at the grain boundaries, makes the precipitates on the grain boundaries discontinuous, reduces the possibility of corrosion channels, and thus improves the corrosion resistance of the grain boundaries; at the same time, it can increase the degree of alloying, increase the proportion of precipitates within the grains, and improve the mechanical properties of the alloy.

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An Al-Mg-Zn-Mn alloy, characterized in that, The composition by mass percentage includes: Mg 3.5%–8%, Zn 0.1%–2%, Mn 0.5%–1.5%, Ti ≤0.02%, with the remainder being Al and unavoidable impurities. The preparation method of the Al-Mg-Zn-Mn alloy includes: batching the materials according to the composition of the Al-Mg-Zn-Mn alloy, melting and casting to obtain an alloy ingot; heat-treating the alloy ingot; deforming the heat-treated alloy ingot, and then performing graded annealing. The heat treatment includes: holding at 400±5℃ for 4 to 6 hours, then raising the temperature to 425±5℃ and holding for 1 to 3 hours, and then raising the temperature to 450±5℃ and holding for 2 to 4 hours; the graded annealing treatment includes: first holding at 350±5℃ for 1 to 3 hours, and then holding at 200℃±5℃ for 1 to 3 hours. The alloy ingot contains the Al6Mn phase.

2. The Al-Mg-Zn-Mn alloy according to claim 1, characterized in that, In the Al-Mg-Zn-Mn alloy, by mass percentage, Fe≤0.25%, Si≤0.1%, Cu≤0.05%, and Cr≤0.12%.

3. The Al-Mg-Zn-Mn alloy according to claim 1, characterized in that, In the alloy, the mass percentage of Mg is 4% to 8%.

4. The Al-Mg-Zn-Mn alloy according to claim 3, characterized in that, The mass percentage of Mg is 4.5% to 8%.

5. The Al-Mg-Zn-Mn alloy according to claim 1, characterized in that, In the alloy, the mass percentage of Zn is 0.4% to 1%.

6. The Al-Mg-Zn-Mn alloy according to claim 5, characterized in that, The mass percentage of Zn is 0.45% to 0.8%.

7. A method for preparing Al-Mg-Zn-Mn alloys, characterized in that, The process includes the following steps: preparing the Al-Mg-Zn-Mn alloy according to any one of claims 1 to 6, smelting and casting to obtain an alloy ingot; The alloy ingot is heat-treated; the heat-treated alloy ingot is then deformed and then subjected to graded annealing. The heat treatment includes: holding at 400±5℃ for 4 to 6 hours, then raising the temperature to 425±5℃ and holding for 1 to 3 hours, and then raising the temperature to 450±5℃ and holding for 2 to 4 hours. The graded annealing process includes: first, holding at 350±5℃ for 1 to 3 hours, and then holding at 200℃±5℃ for 1 to 3 hours.

8. The preparation method according to claim 7, characterized in that, The deformation process includes hot rolling deformation.

9. The preparation method according to claim 8, characterized in that, The hot rolling deformation includes: holding at 400-420℃ for 1-3 hours for hot rolling processing.

10. An Al-Mg-Zn-Mn alloy component, characterized in that, It is prepared by the preparation method according to any one of claims 7 to 9.

11. The Al-Mg-Zn-Mn alloy part according to claim 10, characterized in that, The Al-Mg-Zn-Mn alloy parts have a tensile strength ≥450MPa, a yield strength ≥380MPa, and an elongation ≥12%. The self-corrosion potential of the Al-Mg-Zn-Mn alloy parts in a 3.5wt% NaCl aqueous solution at 25℃ is -1.43 to -1.24V, and the self-corrosion current density is -6.9 to -5.5A / cm. 2 .

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