A method for preparing a layered gradient structure aluminum alloy material

Abstract

The present invention relates to a method for preparing a layered gradient structure aluminum alloy material, comprising the following steps: (1) subjecting spherical pure aluminum powder and spherical aluminum alloy powder to agitated ball milling to obtain flaky pure aluminum powder and flaky aluminum alloy powder; (2) uniformly dispersing the two flaky powders in an ethanol solution at different volume fractions to obtain a plurality of mixed powder dispersions; (3) periodically adding the obtained mixed powder dispersions to a suction filtration device in a certain order, filtering and drying to obtain a filter cake containing periodically stacked flaky powders; and (4) sequentially hot pressing, rolling, and heat treating the filter cake to obtain a layered gradient structure aluminum alloy material. This method can achieve fine control of the gradient structure scale and is easy to adjust, providing a simple, universal, cost-effective, and finely controllable preparation method for the production of gradient structure aluminum alloys.

Description

Technical Field

[0001] The present invention belongs to the technical field of aluminum alloy material preparation, and in particular relates to a method for preparing a layered gradient structure aluminum alloy material. Background Art

[0002] Aluminum alloys are a classic lightweight metal structural material, boasting advantages such as high specific strength, excellent processability, and low cost. They are widely used in military and civilian applications such as aerospace, defense, transportation, and electronics. Developing high-quality aluminum alloys with enhanced comprehensive mechanical properties to meet the needs of more complex operating environments has long been a global goal. Typically, aluminum alloy design strives for uniform component distribution to achieve consistent performance across all parts of the material. However, in some specialized environments, different performance requirements often arise in different parts of the material. For example, brake components, which play a vital role in transportation, require high surface wear and high-temperature resistance, while their cores must also possess sufficient toughness and thermal conductivity. Gradient-structured aluminum alloys offer an effective solution to these challenges. By employing methods that continuously control gradient variations in internal composition and structure, they achieve overall optimization, meeting the specific service requirements of each component. Furthermore, the differentiated stress-strain distributions between gradient layers during overall deformation in gradient aluminum alloys generate a unique synergistic deformation mechanism, significantly enhancing the material's overall mechanical properties.

[0003] At present, gradient aluminum alloys have been developed to a certain extent, but there is still a lack of finely controlled large-scale preparation methods for production and design. Conventional plastic deformation treatment can effectively construct a gradient surface, but the depth is limited and restricted by the shape of the material; although physical, chemical, and electrochemical deposition methods can achieve fine control of the gradient structure, the preparation process is expensive and the finished product size is small; and traditional powder metallurgy, centrifugal casting and other methods can achieve large-scale preparation, but it is difficult to finely control the thickness of the gradient layer, making it difficult to exert certain unique properties at the microscopic scale. The patent document with announcement number CN114411072A discloses a gradient structure aluminum alloy material and its preparation method, which is obtained by cutting the aluminum alloy ingot into rods and then subjecting them to torsion deformation treatment. The size and shape of the processed material are limited, and the core is less affected by the plastic deformation treatment, and the hardness increase is less than 15hv. The patent document with announcement number CN114438435A discloses a gradient aluminum Alumina metal ceramic thermal barrier coating. The plasma spraying preparation process used is expensive, has a low spraying rate, and has high requirements on the quality of the spraying material. Patent documents with announcement numbers CN103160715A and CN113953513A respectively disclose a centrifugal casting method for preparing a gradient aluminum alloy cylinder liner and a powder metallurgy preparation method for a nano-silicon carbide / 2014 aluminum alloy gradient composite material. The gradient materials prepared in the two patents do not show a continuous and fine gradient structure. It can be seen that it is of great significance to develop a simple, universal, cost-effective, finely controllable preparation method for producing gradient structure aluminum alloys. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for preparing a layered gradient structure aluminum alloy material in response to the problems existing in the prior art.

[0005] The purpose of the present invention can be achieved through the following solutions:

[0006] The present invention provides a method for preparing a layered gradient structure aluminum alloy material, the preparation method comprising the following steps:

[0007] (1) Spherical pure aluminum powder and spherical aluminum alloy powder are subjected to stirring ball milling to obtain flake pure aluminum powder A and flake aluminum alloy powder B;

[0008] (2) flake pure aluminum powder A and flake aluminum alloy powder B were mixed in different proportions and uniformly dispersed in ethanol solution to obtain AB mixed powder dispersions with different volume ratios;

[0009] (3) adding the obtained AB mixed powder dispersions of different volume ratios into a suction filtration device periodically according to the volume fraction of A from high to low and then from low to high, and obtaining a filter cake with periodic stacking of flaky powders after suction filtration and drying;

[0010] Specifically, the periodic addition comprises the following steps: the AB mixed powder dispersions of different volume ratios are added to the filtration device in the order of "n#, ..., 5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#, 5#, ..., n#" (n is 2-11) according to the volume ratio of A in descending order; the dispersions are then added to the filtration device in the order of "n#, ..., 5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#, 5#, ..., n#, ..., 5#, 4#, ..., 4#, 5#, ..., n#" (the number of cycles is selected based on the alloy product requirements); after filtration and drying, a filter cake of periodically stacked flaky powders is obtained. There are no special requirements for the volume fraction distribution; it is sufficient to ensure proportional increase or decrease. Preferably, the two flaky powders are uniformly dispersed in ethanol solution according to volume fractions of 95-100 vol.% A + 5-0 vol.% B, "70-80 vol.% A + 20-30 vol.% B", "45-55 vol.% A + 55-45 vol.% B", "20-30 vol.% A + 70-80 vol.% B", and "5-0 vol.% A + 95-100 vol.% B" to obtain five mixed powder dispersions, recorded as "1#, 2#, 3#, 4#, 5#"; the obtained mixed powder dispersions are periodically added to a suction filtration device in the order of "5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#, 5#, 4#, 3#...4#, 5#", and after suction filtration and drying, a filter cake with periodic stacking of flaky powders is obtained. Preferably, the concentrations of the AB mixed powder dispersions of different volume ratios are the same.

[0011] (4) The filter cake is sequentially hot-pressed, rolled, and heat-treated to obtain a layered gradient structure aluminum alloy material.

[0012] In the step (1), the particle size d50 of the spherical pure aluminum powder and the spherical aluminum alloy powder is 10-15 μm.

[0013] In the step (1), the spherical aluminum alloy powder is 7055 or 2024 aluminum alloy powder.

[0014] In the step (1), the stirring ball mill has a rotation speed of 200-400 rpm, a ball milling time of 4-8 h, and a ball-to-material ratio of 20:1.

[0015] In the step (1), the stirring ball milling solvent is anhydrous ethanol, and the ratio of solvent volume (mL) to powder mass (g) is 1-5.

[0016] In the step (1), the stirring ball milling process control agent is titanate, and the mass ratio of the control agent to the powder mass is 0.01-0.05.

[0017] In step (1), the thickness of the flaky powder is 0.5-2 μm and the diameter of the flaky powder is 30-80 μm. If the flaky powder is not ground into flaky form, a fine and adjustable gradient structure cannot be obtained.

[0018] In the step (2), the concentration of the mixed powder dispersion is 0.01-0.2 g / mL.

[0019] In step (3), the suction filtration and drying time is 24-30 hours, and the mixture is dried at room temperature. The suction filtration process is maintained. Each time the mixed powder dispersion is added, the next batch of dispersion is added after the dispersant is filtered out. Without suction filtration, effective self-assembly and tile stacking of the two-dimensional sheet powder cannot be achieved.

[0020] In the step (4), the pressure direction of the hot pressing molding is the filtration direction of the filter cake, the pressure is 400-800 MPa, the hot pressing temperature is 400-500°C, the holding time is 30-60 min, and the argon atmosphere is used for protection.

[0021] In the step (4), the reduction in each rolling pass is 25%, the rolling holding temperature is 400-500° C., and the holding time in each rolling pass is 10 minutes.

[0022] In step (4), the heat treatment includes sequentially performing solution treatment and aging. The solution treatment temperature is 450-500°C and the solution treatment time is 1-3 hours; the aging treatment temperature is 120-180°C and the holding time is 2-20 hours.

[0023] The technical principle of the present invention is: utilizing the fluid self-assembly characteristics of the two-dimensional flaky metal powder prepared by stirred ball milling during the liquid phase filtration process, the orderly stacking and paving of each component layer by layer is achieved in the filtration direction. Since the thickness of the powder single sheet is small and the paving is spontaneous and smooth, the thickness of the powder layer can be controlled within a very small range, thus achieving fine control of the gradient structure. At the same time, the contact area between the powders after flaking is increased, and the van der Waals force is significant. After filtration and drying, the filter cake can still maintain its original structure without being destroyed, and can be effectively transferred and subsequently densified and formed, providing a simple, universal, cost-effective, finely controllable preparation method for the production of gradient structure aluminum alloys.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Compared to traditional methods for preparing gradient-structured aluminum alloys, such as plastic deformation treatment and physical and chemical deposition, the preparation method used in the present invention is not limited by material size and is suitable for large-scale preparation. Furthermore, unlike traditional powder metallurgy and stirring casting methods, this method allows for precise control of the scale of the gradient structure and is easy to adjust. Compared with the prior art, the equipment used in the present invention is all conventional general-purpose equipment, with a reasonable process design, simple operation, and ease of application, significantly reducing experimental costs and test cycles. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0027] Figure 1 The morphologies of the 7055 aluminum alloy powders in Examples 1, 2, and 3 of the present invention are shown in FIG. (a) shows the original spherical 7055 aluminum alloy powder, and (b) and (c) show the flaky 7055 aluminum alloy powders after stirring and ball milling.

[0028] Figure 2 Schematic diagram of the assembly of the gradient structure of the filtration process in Examples 1, 2, and 3 of the present invention.

[0029] Figure 3 Figure 1 shows the cross-sectional BSE diagrams of the layered gradient structure aluminum alloy of the present invention. (a) shows the layered gradient structure aluminum alloy with 3 periods in Example 1, (b) shows the layered gradient structure aluminum alloy with 6 periods in Example 2, and (c) shows the layered gradient structure aluminum alloy with 12 periods in Example 3.

[0030] Figure 4 This is a local BSE image of the cross section of the layered gradient structure aluminum alloy in Example 2 of the present invention and the corresponding EDS line scan. DETAILED DESCRIPTION

[0031] The present invention will be described in detail below with reference to specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those skilled in the art, several variations and improvements can be made without departing from the scope of the present invention. These all fall within the scope of protection of the present invention.

[0032] The method for preparing a layered gradient structure aluminum alloy material according to the present invention comprises the following steps:

[0033] (1) Spherical pure aluminum powder and spherical aluminum alloy powder are subjected to stirring ball milling to obtain flake pure aluminum powder A and flake aluminum alloy powder B;

[0034] (2) The two flaky powders were uniformly dispersed in ethanol solution according to the volume fractions of "100 vol.% A", "75 vol.% A + 25 vol.% B", "50 vol.% A + 50 vol.% B", "25 vol.% A + 75 vol.% B", and "100 vol.% B", respectively, to obtain five mixed powder dispersions, which were recorded as "1#, 2#, 3#, 4#, and 5#";

[0035] (3) adding the obtained mixed powder dispersion to a suction filtration device in the order of "5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#, 5#, 4#, 3#... 4#, 5#" periodically, and obtaining a filter cake of periodically stacked flaky powder after suction filtration and drying;

[0036] (4) The filter cake is sequentially hot-pressed, rolled, and heat-treated to obtain a layered gradient structure aluminum alloy material.

[0037] Example 1

[0038] In this embodiment, a layered gradient structure aluminum alloy with a period number of 3 is prepared. The preparation method is as follows:

[0039] 200g of spherical 7055 aluminum alloy powder with a particle size of d50 = 10-15μm (such as Figure 1 (a) The flaky 7055 aluminum alloy powder was obtained by stirring ball milling at a ball milling speed of 350 rpm, a ball milling time of 4 h, a ball-to-material ratio of 20:1, and a ball milling solvent of 500 mL anhydrous ethanol and a ball milling control agent of 5 g titanate, respectively. Figure 1 As shown in (b) and (c), the powder thickness is 0.5-2μm and the flake diameter is 30-80μm. Similarly, at a stirring ball mill speed of 250rpm, the other parameters remain unchanged to obtain flaky pure aluminum powder. The flaky pure aluminum powder is denoted as A, and the flaky 7055 aluminum alloy powder is denoted as B. The two flaky powders are uniformly dispersed in ethanol solution according to the volume fractions of "100vol.%A", "75vol.%A+25vol.%B", "50vol.%A+50vol.%B", "25vol.%A+75vol.%B", and "100vol.%B", respectively, to obtain 5 mixed powder dispersions, denoted as "1#, 2#, 3#, 4#, 5#", and the dispersion concentration is 0.060g / mL. The obtained mixed powder dispersions are added to the filtration device in the order of "5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#" for 2 times. The assembly diagram is shown as follows. Figure 2As shown, the amount of each dispersion added each time is 200 mL, and after filtration and drying for 24 hours, a filter cake with periodic stacking of flaky powder is obtained. The filter cake is hot-pressed along its filtration direction, with a hot-pressing pressure of 500 MPa, a hot-pressing temperature of 450°C, a holding time of 60 minutes, and argon atmosphere protection. The hot-pressed block is then rolled, with a rolling reduction of 25% per pass, a rolling holding temperature of 450°C, and a return to the furnace holding time of 10 minutes. The material is then solution treated at 475°C for 3 hours, quenched, and aged at 120°C for 12 hours to obtain a layered gradient structure aluminum alloy with a period number of 3, as shown Figure 3 As shown in (a).

[0040] Example 2

[0041] In this embodiment, a layered gradient structure aluminum alloy with a period number of 6 is prepared. The preparation method is as follows:

[0042] 200g of spherical 7055 aluminum alloy powder with a particle size of d50 = 10-15μm (such as Figure 1 (a) The flaky 7055 aluminum alloy powder was obtained by stirring ball milling at a ball milling speed of 350 rpm, a ball milling time of 4 h, a ball-to-material ratio of 20:1, and a ball milling solvent of 500 mL anhydrous ethanol and a ball milling control agent of 5 g titanate, respectively. Figure 1 As shown in (b) and (c), the powder thickness is 0.5-2μm and the flake diameter is 30-80μm. Similarly, at a stirring ball mill speed of 250rpm, with other parameters unchanged, flaky pure aluminum powder was produced. The flaky pure aluminum powder was denoted as A, and the flaky 7055 aluminum alloy powder was denoted as B. The two flaky powders were uniformly dispersed in ethanol solution at volume fractions of "100vol.%A", "75vol.%A+25vol.%B", "50vol.%A+50vol.%B", "25vol.%A+75vol.%B", and "100vol.%B", respectively. Five mixed powder dispersions were obtained, denoted as "1#, 2#, 3#, 4#, 5#", and the dispersion concentration was 0.030g / mL. The obtained mixed powder dispersion is added into the filtration device 5 times in the order of "5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#", with each dispersion added in an amount of 200 mL each time. After filtration and drying for 24 hours, a filter cake with periodic stacking of flaky powder is obtained. The filter cake is hot pressed along its filtration direction, with a hot pressing pressure of 500 MPa, a hot pressing temperature of 450°C, a holding time of 60 minutes, and argon atmosphere protection. The hot pressed block is then rolled, with a rolling reduction of 25% per pass, a rolling holding temperature of 450°C, and a return to the furnace holding time of 10 minutes. The material is then solution treated at 475°C for 3 hours, quenched, and aged at 120°C for 12 hours to obtain a layered gradient structure aluminum alloy with a period number of 6, such as Figure 3(b) shown.

[0043] Example 3

[0044] In this embodiment, a layered gradient structure aluminum alloy with a period number of 12 is prepared. The preparation method is as follows:

[0045] 200g of spherical 7055 aluminum alloy powder with a particle size of d50 = 10-15μm (such as Figure 1 (a) The flaky 7055 aluminum alloy powder was obtained by stirring ball milling at a ball milling speed of 350 rpm, a ball milling time of 4 h, a ball-to-material ratio of 20:1, and a ball milling solvent of 500 mL anhydrous ethanol and a ball milling control agent of 5 g titanate, respectively. Figure 1 As shown in (b) and (c), the powder thickness is 0.5-2μm and the flake diameter is 30-80μm. Similarly, at a stirring ball mill speed of 250rpm, with other parameters unchanged, flaky pure aluminum powder was produced. The flaky pure aluminum powder was denoted as A, and the flaky 7055 aluminum alloy powder was denoted as B. The two flaky powders were uniformly dispersed in ethanol solution at volume fractions of "100vol.%A", "75vol.%A+25vol.%B", "50vol.%A+50vol.%B", "25vol.%A+75vol.%B", and "100vol.%B", respectively. Five mixed powder dispersions were obtained, denoted as "1#, 2#, 3#, 4#, 5#", and the dispersion concentration was 0.015g / mL. The obtained mixed powder dispersion was added into the filtration device 11 times in the order of "5#, 4#, 3#, 2#, 1#, 2#, 3#, 4#", with 200 mL of each dispersion added each time. After filtration and drying for 24 hours, a filter cake with periodic stacking of flaky powder was obtained. The filter cake was hot pressed along its filtration direction, with a hot pressing pressure of 500 MPa, a hot pressing temperature of 450°C, a holding time of 60 minutes, and argon atmosphere protection. The hot pressed block was then rolled, with a rolling reduction of 25% per pass, a rolling holding temperature of 450°C, and a return to the furnace holding time of 10 minutes. The material was then solution treated at 475°C for 3 hours, quenched, and aged at 120°C for 12 hours to obtain a layered gradient structure aluminum alloy with a period number of 12, such as Figure 3 As shown in (a).

[0046] EDS line scan analysis was performed on Example 2. Figure 4 As shown, it can be seen that the aluminum alloy components are distributed in a gradient periodic manner, the thickness of one periodic layer is about 180μm, and the thickness of a single homogeneous component layer is about 20μm, achieving fine control of the gradient structure scale.

[0047] Comparative Example 1

[0048] In this embodiment, a layered gradient structure aluminum alloy with a period number of 3 is prepared. The preparation method is basically the same as that in Example 1, with the only difference being that the aluminum and aluminum alloy powders are not ball-milled.

[0049] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art may make various variations or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a layered gradient structure aluminum alloy material, characterized in that: The preparation method comprises the following steps: (1) Spherical pure aluminum powder and spherical aluminum alloy powder are subjected to stirring ball milling to obtain flake pure aluminum powder A and flake aluminum alloy powder B; (2) After mixing flaky pure aluminum powder A and flaky aluminum alloy powder B in different volume ratios, the mixtures were uniformly dispersed in ethanol solutions to obtain AB mixed powder dispersions in different volume ratios; (3) The obtained AB mixed powder dispersions of different volume ratios are periodically added to a filtration device according to the volume fraction of the flaky pure aluminum powder A from high to low and then from low to high, and after filtration and drying, a filter cake with periodic stacking of flaky powders is obtained; (4) hot pressing, rolling, and heat treating the filter cake in sequence to obtain a layered gradient structure aluminum alloy material; In step (1), the stirring ball milling speed is 200-400 rpm, and the ball milling time is 4-8 h; the process control agent of the stirring ball milling is titanate, and the mass ratio of the control agent to the powder mass is 0.01-0.05; In step (4), the pressure direction of the hot pressing molding is the filtration direction of the filter cake, the pressure is 400-800 MPa, the hot pressing temperature is 400-500 ° C, the holding time is 30-60 min, and the argon atmosphere is protected; the reduction amount of each rolling pass is 25%, the rolling holding temperature is 400-500 ° C, and the reheat holding time between passes is 10 min.

2. The preparation method according to claim 1, characterized in that In step (1), the particle size d50 of the spherical pure aluminum powder and the spherical aluminum alloy powder is 10-15 μm.

3. The preparation method according to claim 1, characterized in that In step (2), the concentration of the mixed powder dispersion is 0.01-0.2 g / mL.

4. The preparation method according to claim 1, characterized in that In step (3), the filtration and drying time is 24-30 h, and the product is dried at room temperature.

5. The preparation method according to claim 1, characterized in that In step (4), the heat treatment includes sequentially performing solution treatment and aging; the solution treatment temperature is 450-500°C, and the solution treatment time is 1-3 hours; the aging temperature is 120-180°C, and the holding time is 2-20 hours.

Images