High-strength aluminum alloy material and preparation method thereof

Abstract

The invention provides a high-strength aluminum alloy material and a preparation method thereof.The method comprises the steps that after raw materials are smelted, Ar gas rotary blowing refining is carried out for 20 minutes at the temperature of 700 + / -5 DEG C, and then semi-continuous casting is carried out at the temperature of 690 + / -5 DEG C; the cast ingot is subjected to two-stage homogenization treatment, heat preservation is conducted for 12 hours at the first stage of 460 + / -5 DEG C, and heat preservation is conducted for 8 hours at the second stage of 480 + / -5 DEG C; the cast ingot obtained after homogenization treatment is heated to 420 + / -5 DEG C, heat preservation is conducted for 4 hours, rough rolling and finish rolling are conducted, and the total deformation reaches 85%; the hot-rolled plate is subjected to heat preservation at 475 + / -2 DEG C for 40 minutes and then subjected to water quenching, the water temperature is 20 + / -2 DEG C, and the transfer time is smaller than or equal to 15 seconds; performing a two-stage aging process, keeping the first stage at 120 + / -2 DEG C for 8 hours, and keeping the second stage at 160 + / -2 DEG C for 12 hours; and carrying out mechanical polishing, anodic oxidation and sealing treatment on the aged plate. The aluminum alloy material manufactured by the method has higher strength, better protection performance and better process stability.

Description

TECHNICAL FIELD

[0001] The present application relates to a high-strength aluminum alloy material and a preparation method thereof. BACKGROUND

[0002] With the increasing demand for light weight and high protection performance of modern military equipment, aluminum alloy materials are widely used in armored vehicles and other military equipment due to their excellent specific strength and good processing performance. In particular, 7-series aluminum alloys have become a key research direction for armored protection materials due to their high strength potential.

[0003] Currently, the commonly used light aluminum alloy armored materials in China mainly include 5083 / H131, 5059 / H131, 7A52, 7B52, etc. The tensile strength of these materials is generally lower than 650 MPa, which is difficult to meet the demand for higher protection level in modern warfare. In practical application, in order to meet the protection requirements, the thickness of the material often needs to be increased, which not only increases the weight of the equipment, but also affects the overall mobility. More importantly, 7-series aluminum alloys have obvious process instability problems in the production process, mainly manifested as large fluctuations in the mechanical properties of the products, and the tensile strength is often lower than 410 MPa, resulting in a yield of less than 50%. This instability is mainly due to inaccurate alloy composition control, fluctuation of heat treatment process parameters, etc., especially the deviation of the content of key elements such as Zn and Mg will significantly affect the aging strengthening effect of the material. In addition, the microstructure control of the aluminum alloy material in the prior art is not ideal, which is difficult to ensure high strength while considering good toughness and forming performance, and it is difficult to effectively promote the deformation or deflection of the bullet head when resisting high-speed bullet impact.

[0004] Therefore, in view of the problems of insufficient strength, poor process stability, and limited protection performance of existing aluminum alloy armored materials, it is urgent to develop a new type of aluminum alloy material with higher strength, better protection performance, and better process stability. SUMMARY

[0005] The purpose of the present application is to solve the problems of the prior art, and to provide a high-strength aluminum alloy material with higher strength, better protection performance, and better process stability. The purpose of the present application is achieved as follows:

[0006] In one aspect, the present application provides a high-strength aluminum alloy material, comprising Zn: 5.0-7.0%, Mg: 1.2-2.0%, Cu: 0.1-0.3%, Fe: 0.2-0.5%, Si: 0.2-0.8%, Ti: 0.01-0.05%, B: 0.001-0.005%, and the balance being Al; the high-strength aluminum alloy material has a tensile strength of ≥650 MPa, a yield strength of ≥550 MPa, and an elongation of ≥10%.

[0007] Further, the weight percentage ratio of Zn to Mg is 3.5-4.2.

[0008] Further, the microstructure of the material comprises: an α-Al matrix with an average grain size ≤50μm; a nanoscale η' strengthening phase with a size of 5-15nm and a volume fraction ≥30%; and a second phase particle with a size of 0.1-2μm and a spacing of 1-5μm.

[0009] Further, the material has a work of fracture ≥42J and an electrochemical corrosion rate <0.1mm / year.

[0010] In another aspect, the present application provides a method for preparing a high-strength aluminum alloy material, comprising: S100, melting raw materials, then performing Ar gas rotary spraying refining at 700±5℃ for 20 minutes, and then performing semi-continuous casting at 690±5℃;

[0011] S200, performing two-stage homogenization treatment on the cast ingot, the first stage being 460±5℃ for 12 hours and the second stage being 480±5℃ for 8 hours;

[0012] S300, heating the homogenization-treated cast ingot to 420±5℃ for 4 hours, and then performing rough rolling and finish rolling with a total deformation of 85%;

[0013] S400, heat-treating the hot-rolled plate at 475±2℃ for 40 minutes, and then water quenching at a water temperature of 20±2℃ with a transfer time ≤15 seconds;

[0014] S500, performing a two-stage aging process, the first stage being 120±2℃ for 8 hours and the second stage being 160±2℃ for 12 hours;

[0015] S600, performing mechanical polishing, anodic oxidation and sealing treatment on the aged plate.

[0016] Further, in the S100, the raw materials comprise aluminum ingots with a purity ≥99.9%, zinc ingots, magnesium ingots, copper plates, Al-Fe intermediate alloy, Al-Si intermediate alloy and Al-Ti-B intermediate alloy.

[0017] Further, in the S300, the rough rolling has a rough rolling temperature of 400±5℃ and a finish rolling temperature of 350±5℃ with a deformation of 75%; and the finish rolling has a rough rolling temperature of 350±5℃ and a finish rolling temperature of 300±5℃ with a deformation of 60%.

[0018] Further, in the S600, the anodic oxidation uses an electrolyte of 15% sulfuric acid solution with a current density of 1.5A / dm², a voltage of 18V and a time of 30 minutes; and the sealing treatment is boiling water sealing at a temperature of 98±2℃ for 30 minutes.

[0019] Compared with the prior art, the beneficial effects of the present application are: by controlling the content range and ratio of each alloying element, the alloy can form a high volume fraction of nanoscale η' strengthening phase after aging treatment, thereby significantly improving the tensile strength and yield strength of the material, so that the tensile strength reaches or exceeds 650 MPa and the yield strength reaches 550 MPa; by fine control of alloy composition and preparation process, especially homogenization treatment, hot rolling deformation, solid solution treatment and two-stage aging process, the α-Al matrix grains are effectively refined, and the size and spacing of the second phase particles are controlled, so that the material maintains high strength while the elongation is ≥10% and the work of injury is ≥42J, improving the toughness and impact resistance of the material; the present application effectively reduces the electrochemical corrosion rate of the material by optimizing the alloy composition and surface treatment process, improves the corrosion resistance of the material, and prolongs the service life of the equipment;

[0020] The preparation method provided by the present application effectively solves the problem of instability of the production process in the prior art by precisely controlling the parameters of each process link such as melting, casting, homogenization, hot rolling, solid solution and aging, especially Ar gas rotary blowing refining, two-stage homogenization treatment, two-stage aging process and strict temperature and time control, so that the yield of the prepared high-strength aluminum alloy material is ≥85%, the mechanical property fluctuation range is controlled within ±5%, and the stability and reliability of the product quality are ensured. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 A flowchart of a high-strength aluminum alloy preparation method. DETAILED DESCRIPTION

[0022] In order to deepen the understanding of the present application, the present application will be further described in combination with the embodiments and drawings, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0023] In one aspect, the embodiments of the present application propose a high-strength aluminum alloy material, which comprises Zn: 5.0-7.0%, Mg: 1.2-2.0%, Cu: 0.1-0.3%, Fe: 0.2-0.5%, Si: 0.2-0.8%, Ti: 0.01-0.05%, B: 0.001-0.005%, and the balance is Al; the high-strength aluminum alloy material has a mechanical property of tensile strength ≥ 650 MPa, yield strength ≥ 550 MPa, and elongation ≥ 10%.

[0024] It should be noted that Zn is the main strengthening element of the 7 series aluminum alloy, and the MgZn2 phase formed by Zn and Mg is the key to obtaining high strength of the material. When the content of Zn is less than 5.0%, it is difficult to form a sufficient amount of strengthening phase, resulting in insufficient strength; when it exceeds 7.0%, it is easy to form coarse η phase at the grain boundary, reducing the toughness and corrosion resistance of the material; Mg element cooperates with Zn to form a strengthening phase, and also improves the solid solution strengthening effect of the material; Mg content is used to balance the strength and toughness of the material, and when the content is less than 1.2%, it is difficult to form sufficient strengthening phase with Zn; when it exceeds 2.0%, the plasticity of the material will decrease significantly, and the processing performance will be poor; in particular, by controlling the weight percentage ratio of Zn to Mg in the range of 3.5-4.2, the best phase composition and distribution can be obtained; the addition of Cu can improve the corrosion resistance and strength of the material, and the Al2Cu phase formed by Cu and Al can play a supplementary strengthening role; Fe and Si are common impurity elements, which are controlled in a specific range in the application, so as to avoid the damage of excessive impurities to the performance, and also to form fine dispersed phase to improve the material organization; the trace addition of Ti and B mainly plays a role in refining the grain, and by forming Al3Ti and TiB2 particles, the grain growth during casting and heat treatment is effectively inhibited.

[0025] In the embodiment, the weight percentage ratio of Zn to Mg is 3.5-4.2; the microstructure of the material includes: α-Al matrix, the average grain size is ≤50μm; nanoscale η' strengthening phase, the size is 5-15nm, the volume fraction is ≥30%; second phase particles, the size is 0.1-2μm, the interval is 1-5μm; the material has a wound work ≥42J, and an electrochemical corrosion rate <0.1mm / year.

[0026] It should be noted that the fine grain of the α-Al matrix is used to realize better grain boundary strengthening effect; the nanoscale η' phase is used for high-density precipitation strengthening; the micron-sized second phase particles are used for crack deflection and prevention, improving the toughness of the material; this synergistic effect enables the material to maintain high strength while having excellent impact resistance; among them, the wound work is an index of bullet resistance, indicating the value of impact energy absorbed; the electrochemical corrosion rate is an index of corrosion resistance.

[0027] The plate made of the high-strength aluminum alloy material of the embodiment is tested, and the results are as follows:

[0028] The tensile strength is 672 MPa, the yield strength is 583 MPa with 0.2% offset, the elongation is 12% with 50 mm gauge length, the hardness is 185 HV with 5 kg load, the electrochemical corrosion rate is 0.08 mm / year under the standard of ASTM G59, and the salt spray test under the standard of GB / T 10125 is 2000 hours without red rust, and the impact energy under the standard of ASTM E23 is 45 J.

[0029] Please refer to Figure 1 In another aspect, the embodiments of the present application propose a preparation method of high-strength aluminum alloy material, comprising: S100, smelting raw materials, then performing Ar gas rotary spraying refining at 700±5°C for 20 minutes, and then performing semi-continuous casting at 690±5°C.

[0030] Exemplarily, S100 further comprises S110: using aluminum ingots with purity ≥99.9% as base material, and using zinc ingots with purity 99.95%, magnesium ingots with purity 99.9%, copper plates with purity 99.9%, Al-Fe intermediate alloy with Fe content 20 wt%, Al-Si intermediate alloy with Si content 15 wt%, and Al-Ti-B intermediate alloy with Ti content 5 wt% and B content 1 wt% as alloying raw materials, and the weighing precision of each raw material is controlled within ±0.05%;

[0031] S120: adding the aluminum ingots into an electric resistance furnace and heating to 750±10°C to completely melt the aluminum ingots, after the temperature of the aluminum liquid is stable, sequentially adding the Al-Fe and Al-Si intermediate alloys, and maintaining for 30 minutes to make the alloying elements fully diffuse, in this process, the surface of the melt is covered with special flux, and the composition of the special flux is 50% NaCl+30% KCl+20% Na3AlF6, to prevent oxidation and element burning loss;

[0032] S130: reducing the temperature of the melt to 710±5°C, sequentially adding the zinc ingots, magnesium ingots and copper plates, and stirring with a mechanical stirrer at a speed of 200 rpm for 15 minutes to ensure uniform distribution of the alloying elements, at this time, the composition of the melt is: Zn 6.2%, Mg 1.6%, Cu 0.2%, Fe 0.3%, Si 0.5%, Ti 0.03%, B 0.003%, and the balance is Al;

[0033] S140: performing Ar gas rotary spraying refining at 700±5°C, the Ar gas flow rate is 15 L / min, the rotary speed is 300 rpm, and the refining time is 20 minutes, this process can effectively remove hydrogen and inclusions in the melt, so that the hydrogen content is reduced to below 0.12 mL / 100 g Al;

[0034] S150: using semi-continuous casting, the casting temperature is controlled at 690±5℃, the cooling water flow is 3.5m³ / h, the casting speed is 80mm / min, the ingot with size of Φ200mm×2000mm is obtained, and electromagnetic stirring is used in the casting process, the frequency is 30Hz, and the current intensity is 150A to refine the grains.

[0035] S200, the ingot is subjected to two-stage homogenization treatment, the first stage is 460±5℃ for 12 hours, and the second stage is 480±5℃ for 8 hours.

[0036] Exemplarily, the ingot is placed in a forced convection homogenization furnace and subjected to two-stage treatment, in the first stage, the temperature is kept at 460±5℃ for 12 hours, which mainly promotes the dissolution of low-melting-point eutectic phase and the preliminary diffusion of elements, the furnace atmosphere is nitrogen protection, and the oxygen content is controlled to be below 100ppm to prevent surface oxidation; in the second stage, the temperature is raised to 480±5℃ for 8 hours, this higher temperature stage can further promote the uniform distribution of Zn, Mg and other elements, and also make part of the residual insoluble phase dissolve, the temperature rising rate is 50℃ / h to ensure temperature uniformity; after the treatment, the ingot is air-cooled to room temperature at a rate of 20℃ / h, after the treatment, the macro-segregation index of the ingot is reduced from the initial 1.8 to below 0.3, and the micro-segregation degree is reduced by more than 85%.

[0037] S300, the ingot after homogenization treatment is heated to 420±5℃ for 4 hours, and then subjected to rough rolling and finish rolling, and the total deformation amount reaches 85%.

[0038] Exemplarily, S300 further comprises S310: heating the ingot after homogenization treatment to 420±5℃ and keeping for 4 hours, and during the heating process, stepwise heating is adopted: first rising to 300℃ at a rate of 100℃ / h, and then rising to 420℃ at a rate of 50℃ / h, so that the core-surface temperature difference is not more than 15℃;

[0039] S320: rough rolling is carried out on a four-high reversible hot rolling mill, the rolling temperature is 400±5℃, the final rolling temperature is 350±5℃, the pass reduction is 15-20%, and the total deformation amount reaches 75%, emulsion lubrication is used during rolling, the composition of the emulsion is 5% synthetic ester+95% water, the flow rate is 200L / min, and the rolling force is controlled to be 800-1000 tons;

[0040] S330: the plate after rough rolling is kept at 380±5℃ for 2 hours to eliminate work hardening and residual stress, and then air-cooled to below 300℃ after annealing;

[0041] S340: finish rolling on a six-roller finishing mill, with a rough rolling temperature of 350±5℃, a finish rolling temperature of 300±5℃, a pass reduction of 10-15%, a total deformation of 60%, a rolling speed of 1.5-2m / s, and a rolling force of 400-600 tons.

[0042] Finally, a plate with a thickness of 20mm is obtained, with a grain size of 35-45μm and second phase particles uniformly distributed with a spacing of 2-4μm.

[0043] S400: after hot rolling, the plate is held at 475±2℃ for 40 minutes, and then quenched in water at 20±2℃, with a transfer time of ≤15 seconds.

[0044] Exemplarily, after hot rolling, the plate is placed in a salt bath furnace for solid solution treatment, with a salt bath composition of 50% KNO3+50% NaNO3, and a PID controller is used to control the heating temperature to 475±2℃; the holding time is controlled to be 40 minutes, and in the specific implementation, the holding time is increased by 1 minute for each 1mm increase in the thickness of the plate; the time from removal from the furnace to quenching in water is ≤15 seconds; the quenching medium is deionized water at 20±2℃, with a flow rate of 3m / s; after this treatment, the dissolution rate of the soluble phase in the alloy reaches more than 98%, and the solid solution amounts of Zn, Mg and Cu in the supersaturated solid solution obtained after quenching are 4.8%, 1.3% and 0.18% respectively.

[0045] S500: a two-stage aging process is performed, with a first stage at 120±2℃ for 8 hours and a second stage at 160±2℃ for 12 hours; for precipitating a nanoscale strengthening phase in the matrix.

[0046] Exemplarily, a forced convection air circulation furnace is used, with a first stage aging temperature of 120±2℃, a time of 8 hours, and a heating rate of 100℃ / h; a second stage aging temperature of 160±2℃, a time of 12 hours, and a cooling method of furnace cooling to 100℃ followed by air cooling; through this two-stage aging, a high-density nanoscale η' phase, i.e. MgZn2, is formed in the matrix, with a size of 8-12nm and a volume fraction of 35%, and at the same time, the second phase particles have a size of 0.5-1.5μm and a spacing of 2-3μm, forming a multi-scale strengthening structure.

[0047] S600: mechanical polishing, anodic oxidation and sealing treatment are performed on the plate after aging treatment.

[0048] Exemplarily, S600 includes S610: wet grinding is performed using 800#, 1200# and 2000# water sandpaper in sequence, with a polishing pressure of 0.1-0.2MPa, and a final surface roughness Ra≤0.2μm.

[0049] S620: using 15% sulfuric acid solution for analysis pure level, current density: 1.5 A / dm2, voltage 18V, time 30 minutes, temperature 20±2℃, oxide film thickness 15-18μm;

[0050] S630: closed by boiling water sealing method, temperature 98±2℃, time 30 minutes, after sealing, the porosity of the oxide film is ≤2%.

[0051] Finally, it is pointed out that the above examples are only used to illustrate the technical solutions of the present application and are not limiting. Although the present application has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present application can be modified or replaced equivalently without departing from the purpose and scope of the technical solutions of the present application, which should be covered in the scope of the claims of the present application.

Claims

1. A high-strength aluminum alloy material, characterized in that, The alloy comprises Zn: 5.0-7.0%, Mg: 1.2-2.0%, Cu: 0.1-0.3%, Fe: 0.2-0.5%, Si: 0.2-0.8%, Ti: 0.01-0.05%, B: 0.001-0.005%, with the balance being Al; the high-strength aluminum alloy material has mechanical properties of tensile strength ≥650MPa, yield strength ≥550MPa, and elongation ≥10%.

2. The high-strength aluminum alloy material according to claim 1, characterized in that, The weight percentage ratio of Zn to Mg is 3.5-4.

2.

3. The high-strength aluminum alloy material according to claim 1, characterized in that, The microstructure of the material includes: an α-Al matrix with an average grain size ≤50μm; a nanoscale η' reinforcing phase with a size of 5-15nm and a volume fraction ≥30%; and second-phase particles with a size of 0.1-2μm and a spacing of 1-5μm.

4. The high-strength aluminum alloy material according to claim 1, characterized in that, The material has a wound energy ≥42J and an electrochemical corrosion rate <0.1mm / year.

5. A method for preparing a high-strength aluminum alloy material, characterized in that, include: S100. After the raw materials are melted, Ar gas is rotated and sprayed at 700±5℃ for 20 minutes for refining, and then semi-continuous casting is carried out at 690±5℃. S200. The ingot is subjected to a two-stage homogenization treatment: the first stage is held at 460±5℃ for 12 hours, and the second stage is held at 480±5℃ for 8 hours. S300: The homogenized ingot is heated to 420±5℃ and held for 4 hours, then rough and finish rolled, with a total deformation of 85%. S400: Hold the hot-rolled sheet at 475±2℃ for 40 minutes, then quench it in water at 20±2℃ for ≤15 seconds. S500, perform a two-stage aging process, the first stage is kept at 120±2℃ for 8 hours, and the second stage is kept at 160±2℃ for 12 hours; S600 involves mechanical polishing, anodizing, and sealing of the aged sheet material.

6. The method for preparing a high-strength aluminum alloy material according to claim 5, characterized in that, In S100, the raw materials include aluminum ingots, zinc ingots, magnesium ingots, copper plates, Al-Fe master alloys, Al-Si master alloys, and Al-Ti-B master alloys with a purity of ≥99.9%.

7. The method for preparing a high-strength aluminum alloy material according to claim 5, characterized in that, In the S300, the initial rolling temperature of the roughing mill is 400±5℃, the final rolling temperature is 350±5℃, and the deformation is 75%; the initial rolling temperature of the finishing mill is 350±5℃, the final rolling temperature is 300±5℃, and the deformation is 60%.

8. The method for preparing a high-strength aluminum alloy material according to claim 5, characterized in that, In the S600 process, the electrolyte for anodic oxidation is a 15% sulfuric acid solution, the current density is 1.5A / dm², the voltage is 18V, and the time is 30 minutes; the sealing treatment is boiling water sealing at a temperature of 98±2℃ for 30 minutes.

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