Method for improving mechanical properties and corrosion resistance of an erbium-containing Al-Mg alloy

Abstract

The application discloses a method for improving mechanical properties and corrosion resistance of an erbium-containing Al-Mg alloy, and belongs to the technical field of non-ferrous metals. The chemical composition of the alloy (wt. %) is as follows: Mg 5.2-6.2 %, Zn 0.3-0.8 %, Mn 0.5-0.7 %, Er 0.04-0.3 %, Zr 0.05-0.15 %, Fe < 0.3 %, Si < 0.2 %, and the rest is Al. The method comprises the following steps: preparing an erbium-containing Al-Mg alloy plate by adopting a semi-solid forming technology, then performing a 12 % cold rolling + 3 % cold drawing pre-deformation process, then performing a 165 DEG C / 72h stabilization annealing process on the basis, and finally performing an anodic oxidation treatment, so that a high-performance erbium-containing Al-Mg alloy is obtained. The application can effectively control the problem between the strength and corrosion resistance of the erbium-containing Al-Mg alloy, and obtain a high-quality erbium-containing Al-Mg alloy with both strength and corrosion resistance.

Description

Technical Field

[0001] This invention belongs to the field of non-ferrous metals technology, specifically relating to a method for improving the mechanical properties and corrosion resistance of novel erbium-containing Al-Mg alloys. Background Technology

[0002] Aluminum-magnesium alloys are widely used in structural components in building construction, automobile manufacturing, aerospace and shipbuilding due to their low density, excellent corrosion resistance, good machinability and weldability, and high specific strength. Their application in structural components is particularly prominent in corrosive marine environments. Al-Mg alloys have moderate strength. Since the main alloying element Mg cannot be dispersed and precipitated, they are non-heat-treatable aluminum alloys. The main strengthening methods are solid solution strengthening and deformation strengthening of Mg. The addition of magnesium significantly enhances the overall strengthening effect of the alloy. The addition of magnesium is beneficial to the strengthening of Al-Mg alloys for two main reasons: (1) The addition of magnesium effectively reduces the steady-state grain size and increases the dislocation density and dislocation storage capacity; (2) Magnesium atoms tend to agglomerate to the grain boundaries during plastic deformation, thereby reducing the migration rate of the grain boundaries and increasing the defect density of the grain boundaries. Meanwhile, some reports indicate that adding small amounts of rare earth elements (such as Sc, Zr, Er, etc.) to Al alloys can generate nano-sized second-phase particles in the Al matrix, which are coherent and dispersed with the Al matrix, significantly improving the mechanical properties of the aluminum alloy. Since 5xxx aluminum alloys are widely used in corrosive environments such as marine environments, resistance to intergranular corrosion (IGC) is crucial in addition to their mechanical properties. When the magnesium content in Al-Mg alloys exceeds 3.5 wt.%, magnesium atoms preferentially diffuse from α-Al, forming the β-Al3Mg2 phase along grain boundaries, severely reducing the corrosion resistance of the Al-Mg alloy. The formation of IGC in 5xxx aluminum alloys is related to the continuity of the β phase at grain boundaries. The alloying element zinc has a certain influence on the mechanical properties, intergranular corrosion behavior and microstructure of Al-Mg alloys. In Al-Mg alloys, the stable Al-Mg-Zn ternary phase precipitates uniformly inside the grains and can heterogeneously nucleate at the boundaries of dislocations and Al-Mn phases, inhibiting the segregation of Mg atoms to the grain boundaries. This leads to the discontinuous precipitation of the T phase at the grain boundaries, which significantly reduces the corrosion susceptibility of Al-Mg-Zn alloys and improves the strength of the alloys.

[0003] This invention employs a novel aluminum-magnesium alloy, incorporating Er and Zr elements to achieve precipitation strengthening compared to traditional Al-Mg alloys. The alloy is then subjected to a degree of pre-deformation, which increases the dislocation density within the alloy, significantly contributing to the dislocation strengthening mechanism and thus improving its mechanical properties. A stabilization annealing process following pre-deformation promotes the replacement of the continuously precipitated β phase at grain boundaries by the Al-Mg-Zn phase, thereby enhancing the alloy's corrosion resistance. Finally, an anodizing process removes the surface oxide film and impurities, further improving the alloy's corrosion resistance. This results in a dual improvement in the strength and corrosion resistance of the novel erbium-containing Al-Mg alloy, significantly extending the material's service life. Summary of the Invention

[0004] The main objective of this invention is to address the contradiction between strength and corrosion resistance in novel erbium-containing Al-Mg alloys by providing a treatment method that combines pre-deformation, stabilization annealing, and anodizing, thereby expanding its application range in actual production processes.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] Step 1: Preparation of Al-Mg alloy plates

[0007] The chemical composition (wt.%) of the aluminum alloy used in this invention is as follows: Mg: 5.2-6.2%, Zn: 0.3-0.8%, Mn: 0.5-0.7%, Er: 0.04-0.3%, Zr: 0.05-0.15%, Fe < 0.3%, Si < 0.2%, with the remainder being Al. The aluminum-magnesium alloy sheet is prepared using a semi-solid forming technology. The first step involves melting the mixture at 600℃-700℃; the second step involves rapidly cooling the alloy to a semi-solid state at 480-580℃; the third step... The semi-solid aluminum-magnesium alloy was stirred using a spiral stirrer at a speed of 300–500 rpm for 10–30 minutes. The alloy underwent a two-stage homogenization annealing process at (415–425)℃ for 360 min followed by (515–525)℃ for 1000 min. The alloy was then heated to 500℃ and held for 16 hours before extrusion. The extrusion pressure was 103 mN, the extrusion speed was 0.6 mm / s, and the extrusion ratio was 26.57, ultimately yielding a novel erbium-containing aluminum-magnesium alloy hot-extruded sheet.

[0008] Step 2: Preparation of pre-deformed samples

[0009] The pre-deformation method is a combination of cold rolling and cold drawing; the erbium-containing aluminum-magnesium alloy hot extruded sheet first undergoes 10% to 15% cold rolling deformation, then undergoes aging treatment at 150℃ for 1 hour to relieve internal stress and improve plasticity, and finally undergoes 1% to 5% cold drawing deformation.

[0010] Step 3: Heat Treatment Process

[0011] Annealing treatment was carried out on the pre-deformed sample at a temperature of 150-180℃ for 0-120h (not 0).

[0012] Step 4: Anodizing treatment

[0013] The heat-treated alloy is then subjected to pickling and electropolishing. The electrolyte is 15-20% sulfuric acid, and the current density is 1-3 A / dm³. 2 The temperature is maintained between 0 and 20°C.

[0014] In a preferred embodiment of the method described in this invention, Er: 0.05%, Zr: 0.1%, Zn: 0.5%.

[0015] In a preferred embodiment of the method described in this invention, the semi-solid molding temperature is 520°C.

[0016] As a preferred embodiment of the method described in this invention, the stirring method adopts mechanical stirring, the stirring speed is 400 rpm, and the stirring time is 20 minutes.

[0017] As a preferred embodiment of the method described in this invention, the two-stage homogenization process involves a first stage of holding at 415℃~425℃ for 360 min and a second stage of holding at 515℃~525℃ for 1000 min; more preferably, it involves holding at 420℃ / 360 min + 520℃×1000 min.

[0018] In a preferred embodiment of the method described in this invention, the cold rolling deformation is 12% and the cold drawing deformation is 3%.

[0019] As a preferred embodiment of the method described in this invention, the stabilization annealing process is 165℃ / 72h.

[0020] In a preferred embodiment of the method described in this invention, the electrolyte is 18% sulfuric acid, and the current density is 2 A / dm³. 2 The temperature is maintained at 10℃.

[0021] Compared with the prior art, the beneficial effects of the present invention are:

[0022] (1) The present invention significantly increases the dislocation density inside the alloy through pre-deformation, and at the same time, the dislocations interact with the dispersed matter, hindering the movement of dislocations during plastic deformation, thus significantly strengthening the alloy.

[0023] (2) By performing a suitable stabilization annealing process, the present invention can promote the Al-Mg-Zn phase to replace the β phase that was originally continuously precipitated at the grain boundary, thereby greatly improving the corrosion resistance of the alloy.

[0024] (3) This invention further improves the corrosion resistance of the alloy by performing anodizing treatment on the basis of stabilizing annealing. This enables the new erbium-containing Al-Mg alloy to have excellent mechanical properties while ensuring long-term corrosion resistance. Attached Figure Description

[0025] Figure 1 These are hardness variation graphs for Embodiments 1, 2, 3, and 4 of the present invention;

[0026] Figure 2 These are corrosion depth diagrams for Embodiments 1, 2, 3, and 4 of the present invention. Detailed Implementation

[0027] The present invention will be further described in detail below with reference to implementation examples, but the present invention is not limited to the following embodiments.

[0028] Example 1:

[0029] The pre-deformation, stabilization annealing, and anodizing of the novel erbium-containing aluminum-magnesium alloy includes the following steps:

[0030] Step 1: Preparation of Al-Mg alloy plates

[0031] The chemical composition (wt.%) of the aluminum alloy used in this invention is: Mg: 5.5%, Zn: 0.5%, Mn: 0.6%, Er: 0.05%, Zr: 0.1%, with the remainder being Al. Step 1: Melt the mixture at 650℃. Step 2: Rapidly cool the alloy to a semi-solid state at 520℃. Step 3: Stir the semi-solid aluminum-magnesium alloy using a spiral stirrer at a speed of 400 rpm for 20 minutes. Step 4: Heat the resulting alloy at a heating rate of 50℃ / hour from room temperature to 420℃, hold for 360 minutes, continue heating to 520℃, hold for 1000 minutes, and then cool to room temperature in the furnace. Step 5: After heating the alloy to 500℃ and holding for 16 hours, extrusion begins at a pressure of 103 mN, a speed of 0.6 mm / s, and an extrusion ratio of 26.57, ultimately obtaining a novel erbium-containing aluminum-magnesium alloy hot-extruded sheet.

[0032] Step 2: Preparation of pre-deformed samples

[0033] The pre-deformation method combines cold rolling and cold drawing. The alloy first undergoes 12% cold rolling deformation, followed by aging treatment at 150℃ for 1 hour to relieve internal stress and improve plasticity, and finally 3% cold drawing deformation.

[0034] Step 3: Heat Treatment Process

[0035] Annealing was performed on the pre-deformed sample at 165℃ for 72 hours.

[0036] Step 4: Anodizing treatment

[0037] The alloy treated above was then subjected to pickling and electropolishing. The electrolyte was 18% sulfuric acid, and the current density was 2 A / dm³. 2 The temperature is maintained at 10℃.

[0038] Example 2 (Comparative Example):

[0039] Step 1: Preparation of Al-Mg alloy plates

[0040] The chemical composition (wt.%) of the aluminum alloy used in this invention is: Mg: 5.5%, Zn: 0.5%, Mn: 0.6%, Er: 0.05%, Zr: 0.1%, with the remainder being Al. Step 1: Melt the mixture at 650℃. Step 2: Rapidly cool the alloy to a semi-solid state at 520℃. Step 3: Stir the semi-solid aluminum-magnesium alloy using a spiral stirrer at a speed of 400 rpm for 20 minutes. Step 4: Heat the obtained alloy from room temperature to 420℃ at a heating rate of 50℃ / hour, hold for 360 minutes, continue heating to 520℃, hold for 1000 minutes, and then cool to room temperature in the furnace. Step 5: After heating the alloy to 500℃ and holding for 16 hours, extrusion begins at a pressure of 103 mN, a speed of 0.6 mm / s, and an extrusion ratio of 26.57, ultimately obtaining a novel erbium-containing aluminum-magnesium alloy hot-extruded sheet.

[0041] Step 2: Preparation of pre-deformed samples

[0042] Example 2: Remain in its original state without any pre-deformation process;

[0043] Step 3: Heat Treatment Process

[0044] Example 2 remains in its original state and is not subjected to stabilization annealing process.

[0045] Step 4: Anodizing treatment

[0046] Example 2 was kept in its original state and no anodizing treatment was performed.

[0047] Example 3 (Comparative Example):

[0048] Step 1: Preparation of Al-Mg alloy plates

[0049] The chemical composition (wt.%) of the aluminum alloy used in this invention is: Mg: 5.5%, Zn: 0.5%, Mn: 0.6%, Er: 0.05%, Zr: 0.1%, with the remainder being Al. Step 1: Melt the mixture at 650℃. Step 2: Rapidly cool the alloy to a semi-solid state at 520℃. Step 3: Stir the semi-solid aluminum-magnesium alloy using a spiral stirrer at a speed of 400 rpm for 20 minutes. Step 4: Heat the resulting alloy at a heating rate of 50℃ / hour from room temperature to 420℃, hold for 360 minutes, continue heating to 520℃, hold for 1000 minutes, and then cool to room temperature in the furnace. Step 5: After heating the alloy to 500℃ and holding for 16 hours, extrusion begins at a pressure of 103 mN, a speed of 0.6 mm / s, and an extrusion ratio of 26.57, ultimately obtaining a novel erbium-containing aluminum-magnesium alloy hot-extruded sheet.

[0050] Step 2: Preparation of pre-deformed samples

[0051] The pre-deformation method combines cold rolling and cold drawing. The alloy first undergoes 12% cold rolling deformation, followed by aging treatment at 150℃ for 1 hour to relieve internal stress and improve plasticity, and finally 3% cold drawing deformation.

[0052] Step 3: Heat Treatment Process

[0053] Example 3 retains the pre-deformed state and does not undergo stabilization annealing process.

[0054] Step 4: Anodizing treatment

[0055] Example 3 retains the pre-deformed state and does not undergo anodizing treatment.

[0056] Example 4 (Comparative Example):

[0057] The chemical composition (wt.%) of the aluminum alloy used in this invention is: Mg: 5.5%, Zn: 0.5%, Mn: 0.6%, Er: 0.05%, Zr: 0.1%, with the remainder being Al. Step 1: Melt the mixture at 650℃. Step 2: Rapidly cool the alloy to a semi-solid state at 520℃. Step 3: Stir the semi-solid aluminum-magnesium alloy using a spiral stirrer at a speed of 400 rpm for 20 minutes. Step 4: Heat the resulting alloy at a heating rate of 50℃ / hour from room temperature to 420℃, hold for 360 minutes, continue heating to 520℃, hold for 1000 minutes, and then cool to room temperature in the furnace. Step 5: After heating the alloy to 500℃ and holding for 16 hours, extrusion begins at a pressure of 103 mN, a speed of 0.6 mm / s, and an extrusion ratio of 26.57, ultimately obtaining a novel erbium-containing aluminum-magnesium alloy hot-extruded sheet.

[0058] Step 2: Preparation of pre-deformed samples

[0059] The pre-deformation method combines cold rolling and cold drawing. The alloy first undergoes 12% cold rolling deformation, followed by aging treatment at 150℃ for 1 hour to relieve internal stress and improve plasticity, and finally 3% cold drawing deformation.

[0060] Step 3: Heat Treatment Process

[0061] Annealing was performed on the pre-deformed sample at 165℃ for 72 hours.

[0062] Step 4: Anodizing treatment

[0063] Example 4 maintains the state after stabilization annealing and does not undergo anodizing treatment.

[0064] Table 1 shows the mechanical properties of Examples 1, 2, 3, and 4. Compared to Example 1, Example 2 maintained its original state after hot extrusion, with a tensile strength of 355.5 MPa, a yield strength of 168.5 MPa, and an elongation of 23%. Example 3 underwent only pre-deformation treatment, resulting in a tensile strength of 366 MPa, a yield strength of 267 MPa, and an elongation of 17.5%. Due to the increased deformation, the dislocation density inside the alloy in Example 3 increased significantly. As shown in Table 1, the yield strength of the alloy increased significantly, by 58% compared to the sample without pre-deformation, but the elongation also decreased. Example 4 combined pre-deformation with stabilizing annealing, resulting in a yield strength of 243 MPa, a tensile strength of 361 MPa, and an elongation of 21.5%. Compared to Example 3, the mechanical properties of Example 1 decreased slightly, but compared to Example 2, its mechanical properties were still significantly improved.

[0065] Table 2 shows the intergranular corrosion performance of Examples 1, 2, 3, and 4. The intergranular corrosion experiment was conducted according to ASTM G67 standard to quantitatively evaluate the intergranular corrosion phenomenon, using the nitric acid weight loss method as the primary analytical method. First, the dimensions of the samples were measured, and their surface area was calculated. Then, the samples were immersed in 200 mL of a pre-prepared 5% hot alkaline solution, maintaining the solution temperature at 80°C for one minute as a pretreatment. After pretreatment, the samples were rinsed with clean water. Subsequently, the samples were completely immersed in concentrated nitric acid (64–69 wt.%) at room temperature for 30 seconds. After rinsing again, the samples were allowed to air dry at room temperature, and their mass was measured using a balance. In a constant-temperature water bath, 120 mL of 64–69 wt.% concentrated nitric acid was prepared, and the water bath temperature was maintained at 30 ± 0.1°C. After standing under these conditions for 24 hours, the samples were removed and thoroughly rinsed with deionized water. After air drying to constant weight, the final mass was determined. Based on the mass difference of the sample before and after treatment, the intergranular corrosion weight loss per unit area was calculated, with units of mg / cm². 2 .

[0066] According to ASTM G67 standard, if the NAMLT value is less than or equal to 15 mg / cm³ 2 The alloy is then deemed resistant to IGC. When NAMLT is greater than or equal to 25 mg / cm³, the alloy is considered resistant. 2 At this point, the material can be considered sensitive to IGC. It can be seen that the weight loss value in Example 2 is 16.6 mg / cm³. 2 At this point, the alloy is in a sensitive state and has poor corrosion resistance. However, Example 3, which only underwent pre-deformation, showed a weight loss of 28.7 mg / cm³. 2 The weight loss increased significantly, and the corrosion resistance deteriorated. In contrast, the weight loss of Example 4, which underwent a combination of pre-deformation and stabilization annealing, was 11.6 mg / cm³. 2 At this point, the alloy is in a non-sensitive state and exhibits good corrosion resistance. In Example 1, after pre-deformation, stabilization annealing, and anodizing treatment, the weight loss value decreased significantly, reaching 3.3 mg / cm³. 2 It exhibits the best corrosion resistance.

[0067] To further compare IGC resistance, the cross-sections of the corroded samples were observed using an optical microscope. Table 2 shows the corrosion depth of different samples after intergranular etching. It can be seen that the corrosion depth corresponds to the weight loss value. Among them, Example 3 showed the worst corrosion resistance with a corrosion depth of 79.9 μm, while Example 1 showed the best corrosion resistance with a corrosion depth of 9.7 μm.

[0068] The above-described embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above-described embodiments. Any obvious improvements, substitutions or modifications that can be made by those skilled in the art without departing from the essence of the present invention shall fall within the protection scope of the present invention.

[0069] Table 1 Mechanical properties of the alloy

[0070] alloy Tensile strength (MPa) Yield strength (MPa) Elongation (%) Hardness (HV) Example 1 363 248 20 115 Example 2 355.5 168.5 23 88 Example 3 366 267 17.5 118 Example 4 361 243 21.5 103

[0071] Table 2. Intergranular corrosion resistance of alloys

[0072] alloy <![CDATA[Weight loss (mg / cm 2 )]]> Corrosion depth (μm) Example 1 3.3 9.7 Example 2 16.6 25.3 Example 3 28.7 79.9 Example 4 11.6 15.2

Claims

1. A method for improving mechanical properties and corrosion resistance of an Al-Mg alloy containing erbium, characterized in that, The method comprises the following steps: (1) Preparation of Al-Mg alloy plate The chemical composition of the aluminum alloy (wt.%) is: Mg: 5.2-6.2%, Zn: 0.3-0.8%, Mn: 0.5-0.7%, Er: 0.04-0.3%, Zr: 0.05-0.15%, Fe < 0.3%, Si < 0.2%, and the balance is Al; the aluminum-magnesium alloy plate is prepared by using a semi-solid forming technology; first step: melting the mixture at 600-700°C; second step: rapidly cooling the alloy to a semi-solid state at 480-580°C; third step: stirring the aluminum-magnesium alloy in the semi-solid state using a helical stirrer, the stirring speed is 300-500 rpm, and the stirring time is 10-30 minutes; fourth step: performing two-stage homogenization annealing of the alloy at (415-425) °C x 360 min + (515-525) °C x 1000 min; fifth step: heating the alloy to 500°C for 16 hours and then starting extrusion, the extrusion pressure is 103 mN, the extrusion speed is 0.6 mm / s, and the extrusion ratio is 26.57, finally obtaining a new type of hot extruded plate of aluminum-magnesium alloy containing erbium; (2) Preparation of pre-deformed sample The pre-deformation method is a combination of cold rolling and cold drawing, first performing 10-15% cold rolling deformation, then performing aging treatment at 150°C / 1 hour, and finally performing 1-5% cold drawing deformation; (3) Heat treatment process Performing annealing treatment at a temperature of 150-180°C for a time of 0-120h and not 0 on the basis of the pre-deformed sample; (4) Anodizing treatment The heat treated alloy is subjected to pickling and electrolytic polishing treatment, the electrolyte being 15-20% sulfuric acid, the current density being 1-3 A / dm 2 and the temperature being maintained at 0-20°C.

2. The method according to claim 1, a method for improving the mechanical properties and corrosion resistance of a new type of Al-Mg alloy containing erbium, characterized in that, In the step (1), the mass percentage content of Er in the aluminum alloy is 0.05%, Zr: 0.1%, and Zn: 0.5%.

3. The method according to claim 1, a method for improving the mechanical properties and corrosion resistance of a new type of Al-Mg alloy containing erbium, characterized in that, In the step (1), the stirring speed is 400 rpm, and the stirring time is 20 minutes.

4. The method of claim 1, a method for improving mechanical properties and corrosion resistance of a new type of Al-Mg alloy containing erbium, characterized in that, In the step (1), the two-stage homogenization treatment process is 415-425°C for 360 min in the first stage and 515-525°C for 1000 min in the second stage.

5. The method of claim 1, wherein, In the step (1), the two-stage homogenization treatment process is 420°C / 360 min + 520 / ℃ x 1000 min.

6. The method of claim 1, wherein, The cold rolling deformation is 12%, and the cold drawing deformation is 3%.

7. The method of claim 1, wherein, The stabilization annealing process is 165°C / 72h.

8. The method of claim 1, wherein, The electrolyte was 18% sulfuric acid and the current density was 2 A / dm 2 The temperature was maintained at 10°C.

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