Low-density moderate-strength corrosion-resistant Al-Zn-Mg-Cu alloy and preparation method thereof

Abstract

The invention discloses a low-density moderate-strength corrosion-resistant Al-Zn-Mg-Cu alloy and a preparation method thereof, belongs to the field of non-ferrous metal preparation, and particularly relates to the low-density moderate-strength corrosion-resistant Al-Zn-Mg-Cu alloy and the preparation method thereof. The invention aims to provide the Al-Zn-Mg-Cu alloy for the marine equipment, which has the characteristics of low density, moderate strength, corrosion resistance and the like. The aluminum alloy comprises the following components in percentage by mass: 4.0-6.0% of Zn, 1.1-2.4% of Mg, 1.5-2.0% of Mn, 0.1-0.3% of Zr, 0.03-0.1% of Ti, less than or equal to 0.5% of Cu, less than or equal to 0.5% of Fe, less than or equal to 0.5% of Si and the balance of Al. Wherein 2.5 < = Zn / Mg < = 3.5. The preparation method comprises the steps of smelting and casting, homogenizing treatment, hot extrusion, solid solution quenching treatment and aging treatment. The invention is applicable to the field of marine equipment.

Description

Technical Field

[0001] The invention belongs to the field of nonferrous metal preparation, and particularly relates to a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy and a preparation method thereof. Background Art

[0002] With the continuous development of industry, the service environment of materials and equipment in the field of national defense and military industry has become more and more complex and harsh, especially in the field of marine equipment, which has put forward higher requirements for lightweight characteristics. In addition, in the marine atmosphere, there are a lot of Cl- and water vapor, and the temperature near the ocean is relatively high, so the material is prone to corrosion and failure, so there are also more stringent requirements for the corrosion resistance of the material.

[0003] In existing marine equipment, more than 90% of the structural frame materials are steel, mainly because of its high strength and corrosion resistance. The aluminum alloys used in the rest are mainly 5-series aluminum alloys, mainly due to their excellent corrosion resistance. However, the mechanical properties of 5-series aluminum alloys are limited by the alloy composition and it is difficult to break through 350MPa, so aluminum alloys are still subject to many restrictions in the manufacturing of marine equipment.

[0004] 7 series aluminum alloys are favored in aerospace, military industry, infrastructure and other fields due to their light weight and high strength. As structural parts, the design concept of 7 series aluminum alloys is dominated by high strength. For existing 7 series aluminum alloys, due to the large potential difference between the grain boundary η-MgZn2 phase and the aluminum matrix, and the continuous distribution of the η phase at the grain boundary, the corrosion resistance of the alloy is poor. At present, the anti-corrosion measures for aluminum alloys are mainly to apply anti-corrosion coatings or anodic protection on the surface of the alloy, but these methods are costly and limited by the service environment. Therefore, how to significantly improve the corrosion resistance of 7 series aluminum alloys while saving production costs, reducing alloy density, and minimizing the reduction of alloy strength is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to provide an Al-Zn-Mg-Cu alloy for marine equipment with low density, medium strength, corrosion resistance and other characteristics, and further to provide a low density, medium strength and corrosion resistant Al-Zn-Mg-Cu alloy and a preparation method thereof.

[0006] The invention discloses a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy, which is composed of 4.0-6.0% Zn, 1.1-2.4% Mg, 1.5-2.0% Mn, 0.1-0.3% Zr, 0.03-0.1% Ti, ≤0.5% Cu, ≤0.5% Fe, ≤0.5% Si and the balance Al in terms of mass percentage; wherein 2.5≤Zn / Mg≤3.5.

[0007] The invention discloses a preparation method of a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy, which comprises smelting and casting, homogenization treatment, hot extrusion, solution quenching treatment and aging treatment.

[0008] The beneficial effects of the present invention are:

[0009] The low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy provided by the present invention has a synergistic effect between the constituent elements and ensures 2.5≤Zn / Mg≤3.5. A lower Zn content can reduce the alloy density; the medium-strength characteristics of the alloy are ensured by the synergistic strengthening of the T phase and the η phase; at the same time, the potential difference between the grain boundary T phase and the matrix is ​​small, and the width of the precipitation-free zone can be further reduced by heat treatment, thereby effectively improving the corrosion resistance of the alloy.

[0010] According to the technical solution provided by the present invention, low-density, medium-strength, corrosion-resistant Al-Zn-Mg-Cu alloy extrusions for marine equipment can be manufactured. DETAILED DESCRIPTION

[0011] Specific implementation method 1: In this implementation method, a low-density, medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0-6.0% Zn, 1.1-2.4% Mg, 1.5-2.0% Mn, 0.1-0.3% Zr, 0.03-0.1% Ti, ≤0.5% Cu, ≤0.5% Fe, ≤0.5% Si and the balance is Al, wherein 2.5≤Zn / Mg≤3.5.

[0012] In the Al-Zn-Mg-Cu alloy composition design of the present invention, Zn and Mg elements are used to generate the necessary strengthening phases η and T-Mg 32 (Al, Zn) 49Strengthening phase, the Zn / Mg mass ratio needs to be within the range of 2.5 to 3.5; too high Zn content will increase the alloy density, and will also precipitate in the matrix as impurities, reducing the alloy plasticity, so the upper limit of Zn content is set to 6.0wt%; too high Mg content will form Al3Mg2 phase with the matrix along the grain boundary, reducing the corrosion resistance of the alloy, so the upper limit of Mg content is set to 2.4wt%. When 7 series aluminum alloy contains Mg, adding Cu element can promote precipitation hardening reaction to improve the thermal stability of T phase and make the distribution of T phase more dispersed; too high Cu element will form brittle Al2Cu phase, affecting the mechanical properties and corrosion resistance of the alloy, so the Cu content does not exceed 0.5wt%. The addition of Mn element can increase the recrystallization temperature of the alloy, and the generated dispersed Al6Mn phase can significantly hinder dislocation migration; too high Mn content will affect the quenching sensitivity of the alloy, so the Mn content does not exceed 2.0wt%. The addition of Zr element can form Al3Zr compound to play a role of dispersion strengthening, and will not affect the content of η phase, T phase and Al6Mn phase; too high Zr element is prone to segregation, so the Zr element content does not exceed 0.3wt%. Therefore, within the required scope of the present invention, the positive effects of Zn, Mg, Cu, Mn and Zr elements on strength and corrosion resistance are synergistically exerted, and the low density, medium strength and corrosion resistance of Al-Zn-Mg-Cu alloy are achieved.

[0013] Specific embodiment 2: This embodiment is different from the specific embodiment 1 in that the low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0% Zn, 1.2% Mg, 1.5% Mn, 0.1% Zr, 0.03% Ti, 0.2% Cu, 0.2% Fe, 0.3% Si and the balance is Al by mass percentage. The rest is the same as the specific embodiment 1.

[0014] Specific embodiment 3: This embodiment is different from the specific embodiment 1 in that the low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0% Zn, 1.6% Mg, 1.8% Mn, 0.2% Zr, 0.05% Ti, 0.3% Cu, 0.5% Fe, 0.5% Si and the balance is Al by mass percentage. The rest is the same as the specific embodiment 1.

[0015] Specific implementation method 4: In this implementation method, a method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy includes smelting and casting, homogenization treatment, hot extrusion, solution quenching treatment, and aging treatment.

[0016] Specific embodiment 5: This embodiment is different from specific embodiment 4 in that the homogenization process is: keep the temperature at 400-420°C for 6-12h, then raise the temperature to 430-460°C, keep the temperature at 430-460°C for 18-30h, cool to 170-190°C with the furnace after the heat preservation process, and then air cool to room temperature to obtain a homogenized ingot. The rest is the same as specific embodiment 4.

[0017] The setting of the two-stage homogenization treatment temperature and holding time in this embodiment takes into account the different diffusion rates of elements such as Zn, Mg, and Cu in the alloy, and will not cause the melting of the low-melting-point second phase to cause overburning. It can fully eliminate the eutectic structure, make the second phase fully dissolved, and the atoms diffuse evenly, thereby achieving the purpose of organizational homogenization, which is beneficial to the smooth extrusion of the ingot.

[0018] Specific embodiment 6: This embodiment is different from the specific embodiment 5 in that the hot extrusion process is: the obtained homogenized ingot is kept at 420-450°C for 2-4 hours, and then extruded to obtain an extruded material; the extrusion rate is 0.3-0.5 m / min, and the extrusion ratio is 20-60. The rest is the same as the specific embodiment 5.

[0019] In the hot extrusion process of this embodiment, extrusion and friction will cause the temperature of the ingot to rise. In order to ensure that the temperature of the alloy ingot during the extrusion process is close to the temperature of the extrusion barrel and the extrusion die and to approximately achieve isothermal extrusion, the preheating temperature of the extrusion barrel and the extrusion die is slightly higher than the insulation temperature of the ingot.

[0020] Specific embodiment 7: This embodiment is different from specific embodiment 6 in that the extrusion barrel and the extrusion die are preheated in advance, the preheating temperature of the extrusion barrel and the extrusion die are both 430-460°C, and the insulation temperature of the homogenization treatment ingot is 5-10°C lower than the preheating temperature of the extrusion barrel. The rest is the same as specific embodiment 6.

[0021] Specific embodiment eight: This embodiment differs from specific embodiment four in that the solution quenching treatment is to place the extruded material in an air furnace at 470-480°C for 0.5-1.5h, followed by water quenching to obtain a solution quenched extruded material. The rest is the same as specific embodiment four.

[0022] Specific embodiment 9: This embodiment is different from specific embodiment 4 in that the aging treatment is to keep the extruded material after solution quenching at 110-130° C. for 20-28 hours. Other aspects are the same as specific embodiment 4.

[0023] The following examples are used to verify the beneficial effects of the present invention:

[0024] The compositions of the embodiments and comparative examples are shown in Table 1, wherein 1# to 6# are alloy embodiments of the present invention, and 7# to 8# are comparative examples.

[0025] Table 1 Alloy composition (mass percentage, wt%)

[0026]

[0027]

[0028] The following is a detailed description of the preparation methods of the examples and comparative examples. Due to the difference in composition, the examples have different process parameters in hot extrusion, solution quenching, and aging, but this does not mean a limitation on the alloy preparation method of the present invention. In fact, other implementation schemes within the process parameter range in the claims can be used.

[0029] Example 1

[0030] Melting and casting were carried out according to the composition of alloy No. 1 in Table 1; the ingot was kept at 400℃ for 6h, then kept at 430℃ for 18h, cooled to 180℃ with the furnace and then air-cooled to room temperature; the ingot was homogenized and kept at 420℃ for 2h, the preheating temperature of the extrusion barrel and the extrusion die was 430℃, the extrusion rate was 0.5m / min, and the extrusion ratio was 60; solution treatment was carried out at 470℃ for 0.5h, and water quenching was carried out; aging was carried out at 120℃ for 20h.

[0031] Example 2

[0032] The preparation method of this embodiment is exactly the same as that of embodiment 1, except that the alloy is melted and cast according to the composition of alloy 2# in Table 1.

[0033] Example 3

[0034] Melting and casting were carried out according to the composition of 3# alloy in Table 1; the ingot was kept at 410℃ for 8h, then kept at 450℃ for 24h, cooled to 180℃ with the furnace and then air-cooled to room temperature; the ingot was homogenized and kept at 430℃ for 3h, the preheating temperature of the extrusion barrel and the extrusion die was 440℃, the extrusion rate was 0.4m / min, and the extrusion ratio was 50; solution treatment was carried out at 470℃ for 1h, and water quenching was carried out; aging was carried out at 120℃ for 24h.

[0035] Example 4

[0036] The preparation method of this embodiment is exactly the same as that of embodiment 3, except that the alloy is melted and cast according to the composition of alloy 4# in Table 1.

[0037] Example 5

[0038] Melting and casting were carried out according to the composition of 3# alloy in Table 1; the ingot was kept at 420℃ for 9h, then kept at 450℃ for 28h, cooled to 180℃ with the furnace and then air-cooled to room temperature; the ingot was homogenized and kept at 450℃ for 3h, the preheating temperature of the extrusion barrel and the extrusion die was 460℃, the extrusion rate was 0.3m / min, and the extrusion ratio was 50; solution treatment was carried out at 470℃ for 1.5h, and water quenching was carried out; aging was carried out at 120℃ for 26h.

[0039] Example 6

[0040] The preparation method of this embodiment is exactly the same as that of embodiment 5, except that the alloy is melted and cast according to the composition of alloy 6# in Table 1.

[0041] Comparative Example 1

[0042] Alloy 7# was melted and cast according to its composition in Table 1; the ingot was kept at 420℃ for 10h, then kept at 450℃ for 30h, cooled to 180℃ with the furnace and then air-cooled to room temperature; the ingot was homogenized and kept at 450℃ for 4h, the preheating temperature of the extrusion barrel and the extrusion die was 460℃, the extrusion rate was 0.3m / min, and the extrusion ratio was 30; solution treatment was performed at 480℃ for 1.5h, and water quenching was performed; aging was performed at 130℃ for 26h.

[0043] Comparative Example 2

[0044] Melting and casting were carried out according to the composition of 8# alloy in Table 1; the ingot was kept at 420℃ for 12h, then kept at 450℃ for 30h, cooled to 180℃ with the furnace and then air-cooled to room temperature; the ingot was homogenized and kept at 450℃ for 4h, the preheating temperature of the extrusion barrel and the extrusion die was 460℃, the extrusion rate was 0.3m / min, and the extrusion ratio was 20; solution treatment was carried out at 480℃ for 1.5h, and water quenching was carried out; aging was carried out at 130℃ for 28h.

[0045] Table 2 Performance results of materials prepared in Example 1-Example 6, Comparative Example 1-Comparative Example 2

[0046]

[0047] It can be seen from Table 2 that, compared with the comparative alloy, although the strength of the inventive alloy is reduced, the alloy density is greatly reduced and the intergranular corrosion resistance is greatly improved.

[0048] In summary, the technical solution of the present invention realizes the low-density and medium-strength corrosion-resistant properties of Al-Zn-Mg-Cu alloy by regulating the alloy composition and combining the homogenization process, hot extrusion process and heat treatment process, and is suitable for the field of marine equipment.

Claims

1. A low-density, medium-strength, corrosion-resistant Al-Zn-Mg-Cu alloy, characterized in that The low-density, medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0-6.0% Zn, 1.1-2.4% Mg, 1.5-2.0% Mn, 0.1-0.3% Zr, 0.03-0.1% Ti, ≤0.5% Cu, ≤0.5% Fe, ≤0.5% Si and the balance is Al, wherein 2.5≤Zn / Mg≤3.

5.

2. A low-density, medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that The low-density, medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0% Zn, 1.2% Mg, 1.5% Mn, 0.1% Zr, 0.03% Ti, 0.2% Cu, 0.2% Fe, 0.3% Si and the balance Al by mass percentage.

3. A low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 1, characterized in that The low-density, medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy is composed of 4.0% Zn, 1.6% Mg, 1.8% Mn, 0.2% Zr, 0.05% Ti, 0.3% Cu, 0.5% Fe, 0.5% Si and the balance Al by mass percentage.

4. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy as claimed in claim 1, characterized in that The preparation method of low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy includes smelting and casting, homogenization treatment, hot extrusion, solid solution quenching treatment and aging treatment.

5. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 4, characterized in that The homogenization process is as follows: keeping the temperature at 400-420°C for 6-12h, then raising the temperature to 430-460°C, keeping the temperature at 430-460°C for 18-30h, cooling with the furnace to 170-190°C after the insulation process, and then air cooling to room temperature to obtain a homogenized ingot.

6. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 5, characterized in that The hot extrusion process is: keeping the homogenized ingot at 420-450° C. for 2-4 hours, and then extruding to obtain an extruded material; the extrusion rate is 0.3-0.5 m / min, and the extrusion ratio is 20-60.

7. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 6, characterized in that The extrusion barrel and the extrusion die are preheated in advance, and the preheating temperature of the extrusion barrel and the extrusion die is 430-460°C. The insulation temperature of the homogenization treatment ingot is 5-10°C lower than the preheating temperature of the extrusion barrel.

8. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 6, characterized in that The solution quenching treatment is to place the extruded material in an air furnace at 470-480° C. for 0.5-1.5 hours, and then water quench to obtain the solution quenched extruded material.

9. The method for preparing a low-density medium-strength corrosion-resistant Al-Zn-Mg-Cu alloy according to claim 8, characterized in that The aging treatment is to keep the extruded material after solution quenching at 110-130° C. for 20-28 hours.

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