Ultrafine grain aluminum magnesium alloy and preparation method and application thereof

Abstract

The invention relates to an ultra-fine grain aluminum magnesium alloy and a preparation method and application thereof, the ultra-fine grain aluminum magnesium alloy provided by the invention comprises the following chemical components: 4.0-6.0 wt% of Mg element, and the balance of Al and inevitable impurities; the grain size of the aluminum magnesium alloy ranges from 100 nm to 1000 nm. And an Mg element grain boundary segregation network is arranged at the grain boundary of the aluminum-magnesium alloy. According to the ultra-fine grain aluminum-magnesium alloy provided by the invention, while the strength of the aluminum alloy is guaranteed, through low-temperature aging treatment, a grain boundary structure is precisely regulated and controlled, segregation of Mg elements in a grain boundary area is induced, a stable three-dimensional discontinuous grain boundary segregation network is constructed, and the grain boundary segregation network can effectively reduce grain boundary energy and inhibit grain growth; and therefore, the structure thermal stability of the ultra-fine grain aluminum alloy is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of aluminum alloy processing technology, specifically to an ultrafine-grained aluminum-magnesium alloy, its preparation method, and its applications. Background Technology

[0002] Aluminum alloys, as typical lightweight metallic structural materials, are widely used in aerospace, automotive manufacturing, and electronic communications due to their excellent specific strength, corrosion resistance, machinability, and good joining properties. With the rapid development of high-end manufacturing, higher requirements are being placed on aluminum alloys in terms of strength, lightweighting, and thermal stability. Developing new high-performance aluminum alloy materials has become a key issue in materials science. In recent years, ultrafine-grained materials (grain size 100-1000 nm) have attracted widespread attention due to their significantly superior strength, hardness, and fatigue performance compared to traditional coarse-grained materials, and have gradually become an important research direction in the field of metallic structural materials. Intense plastic deformation, due to its excellent grain refinement ability, has become the core method for preparing bulk ultrafine-grained metallic materials.

[0003] While vigorous plastic deformation processes can effectively improve material strength, the large number of high-density defects introduced (such as dislocations, vacancies, and grain boundaries) significantly reduce the material's thermal stability. Studies have shown that ultrafine-grained metals, even at temperatures below half their melting point (0.5T), exhibit reduced thermal stability. m While aluminum and its alloys can maintain a relatively stable microstructure at high temperatures, their ultrafine-grained structures are prone to grain coarsening and microstructural instability at lower temperatures (≥200℃), leading to rapid performance degradation and severely limiting the stability and reliability of their engineering applications. Therefore, improving the microstructural stability of ultrafine-grained aluminum alloys at high temperatures and suppressing grain growth and defect evolution are key technical challenges that urgently need to be overcome in this field, and are also the core problem that this invention focuses on solving. Summary of the Invention

[0004] This invention provides an ultrafine-grained aluminum-magnesium alloy, its preparation method, and its application, to solve the problem of poor microstructure stability of existing ultrafine-grained aluminum alloys under high-temperature conditions.

[0005] In a first aspect, the present invention provides an ultrafine-grained aluminum-magnesium alloy, wherein the chemical composition of the aluminum-magnesium alloy is: Mg element content is 4.0-6.0 wt%, and the remainder is Al and unavoidable impurities; The grain size of the aluminum-magnesium alloy is 100-1000 nm; The aluminum-magnesium alloy has a Mg element grain boundary segregation network at the grain boundaries.

[0006] Secondly, the present invention provides a method for preparing the above-mentioned ultrafine-grained aluminum-magnesium alloy, comprising the following steps: obtaining a cast aluminum-magnesium alloy with a Mg element mass percentage of 4.0-6.0 wt%, and subjecting the obtained cast aluminum-magnesium alloy to solution treatment, severe plastic deformation treatment and aging treatment to obtain the ultrafine-grained aluminum-magnesium alloy.

[0007] In one optional embodiment, the solution treatment temperature is 400-450°C.

[0008] In one optional embodiment, the solution treatment time is 18-24 h.

[0009] In one alternative embodiment, the solution treatment further includes a step of water quenching the alloy to room temperature.

[0010] In one optional embodiment, the treatment method for the severe plastic deformation process includes any one of the following: high-pressure torsion method, equal diameter angular extrusion method, and multi-directional free forging method.

[0011] In one optional embodiment, during the severe plastic deformation treatment, the deformation temperature is not higher than 100°C, and the final grain size is refined to 100-1000 nm.

[0012] In one optional embodiment, the aging treatment temperature is 100-150°C.

[0013] In one optional implementation, the processing time for the aging process is 5-10 hours.

[0014] Secondly, the present invention also provides an application of the above-described ultrafine-grained aluminum-magnesium alloy or the aluminum-magnesium alloy prepared by the above-described preparation method in an environment with a temperature ≥200°C.

[0015] The technical solution of this invention has the following advantages: 1. The present invention provides an ultrafine-grained aluminum-magnesium alloy, wherein the chemical composition of the aluminum-magnesium alloy is: Mg element content is 4.0-6.0 wt%, the remainder is Al and unavoidable impurities; the grain size of the aluminum-magnesium alloy is 100-1000 nm; and the grain boundaries of the aluminum-magnesium alloy have Mg element grain boundary segregation networks.

[0016] The ultrafine-grained aluminum-magnesium alloy provided by this invention, while ensuring the strength of the aluminum alloy, precisely controls the grain boundary structure through low-temperature aging treatment, induces the segregation of Mg elements in the grain boundary region, and constructs a stable three-dimensional discontinuous grain boundary segregation network. The grain boundary segregation network can effectively reduce the grain boundary energy and inhibit grain growth, thereby significantly improving the microstructure and thermal stability of the ultrafine-grained aluminum alloy. Attached Figure Description

[0017] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is the EBSD image of the Al-Mg alloy after severe plastic deformation treatment in Example 1 of this invention; Figure 2 These are the EBSD (a), TEM (b), and TEM-EDS (c) images of the Al-Mg alloy after aging treatment in Example 1 of this invention. Figure 3 This is the EBSD image of the Al-Mg alloy prepared in Example 1 of this invention after annealing treatment; Figure 4 This is the EBSD image of the Al-Mg alloy prepared in Comparative Example 1 of this invention after annealing treatment. Figure 5 This is a statistical comparison chart of the grain size of Al-Mg alloys prepared in Example 1 and Comparative Example 1 after annealing treatment. Detailed Implementation The following embodiments are provided to better understand the present invention, but the following embodiments do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the scope of protection of the present invention.

[0019] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0020] Example 1 A method for preparing an ultrafine-grained aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Mg content is 6.0 wt%, the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Mg alloy was placed in a vacuum tube furnace and held at 450°C for 24 h to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0021] S2.2 Severe plastic deformation: The solution-treated Al-Mg alloy was processed by high-pressure torsion. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 150 nm, forming a relatively uniform ultrafine crystalline structure.

[0022] S2.3 Microstructure characterization: EBSD technology was used to analyze the microstructure of the deformed material. For example... Figure 1 As shown, from Figure 1 As can be seen, the grains are significantly refined and the structure is uniform, with a grain size of approximately 150 nm, which meets the requirements for an ultrafine grain structure.

[0023] S3: Timeliness Processing Low-temperature aging treatment induces the segregation of Mg at grain boundaries, constructing a stable grain boundary solute network structure, including: S3.1 Low-temperature aging treatment: The obtained ultrafine-grained Al-Mg alloy was placed in an oil bath at 150℃ and kept at that temperature for 10 h to promote the migration of Mg atoms to the grain boundaries, while avoiding the precipitation of the second phase and grain growth.

[0024] S3.2 Microstructure characterization: The microstructure of Al-Mg alloys after low-temperature aging was systematically analyzed using EBSD and TEM techniques, such as... Figure 2 As shown, Figure 2 In the image, 'a' shows the EBSD image of the Al-Mg alloy after low-temperature aging treatment. Figure 2 Image b is a TEM image of the Al-Mg alloy after low-temperature aging treatment. Figure 2 c is the TEM-EDS image of the Al-Mg alloy after low-temperature aging treatment. Figure 2 As can be seen from images a and b, the grain size remains within the ultrafine range, approximately 160 nm. No obvious second-phase precipitates were observed, and discontinuous Mg segregation bands formed at the grain boundaries. Figure 2 As can be seen from the data in Figure c, the peak concentration of the Mg segregation band is between 10-30 at%Mg, and the width is between 5-10 nm, which verifies the effectiveness of the low-temperature aging treatment.

[0025] S3.3 Annealing Test: The Al-Mg alloy, after low-temperature aging treatment, was annealed at 200℃ for 24 h. The grain size and morphology evolution were observed using EBSD technology. Figure 3 As shown, from Figure 3 As can be seen, its grain size is about 310 nm, which is still an ultrafine crystalline structure.

[0026] Example 2 A method for preparing an ultrafine-grained aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Mg content is 5.0 wt%, the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Mg alloy was placed in a vacuum tube furnace and held at 430°C for 18 h to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0027] S2.2 Severe plastic deformation: The solution-treated Al-Mg alloy was processed by constant diameter angular extrusion. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 500 nm, forming a relatively uniform ultrafine crystalline structure.

[0028] S2.3 Microstructure characterization: Microstructure analysis of the deformed material was performed using EBSD technology. The grains were significantly refined and the microstructure was uniform, meeting the requirements for an ultrafine-grained structure.

[0029] S3: Timeliness Processing Low-temperature aging treatment induces the segregation of Mg at grain boundaries, constructing a stable grain boundary solute network structure, including: S3.1 Low-temperature aging treatment: The obtained ultrafine-grained Al-Mg alloy was placed in an oil bath at 130℃ and kept at that temperature for 8 hours to promote the migration of Mg atoms to the grain boundaries, while avoiding the precipitation of the second phase and grain growth.

[0030] S3.2 Microstructure characterization: The microstructure of the Al-Mg alloy after low-temperature aging treatment was systematically analyzed using EBSD and TEM techniques. The results showed that the grain size was still in the ultrafine range, and discontinuous, thick Mg segregation bands were formed at the grain boundaries. No obvious second-phase precipitates were observed, which verified the effectiveness of the low-temperature aging treatment.

[0031] S3.3 Annealing Test: The Al-Mg alloy, after low-temperature aging treatment, was annealed at 200℃ for 24 h, and its grain size and morphology evolution were observed using EBSD technology. It still has an ultrafine grain structure.

[0032] Example 3 A method for preparing an ultrafine-grained aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Mg content is 4.0 wt%, the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Mg alloy was placed in a vacuum tube furnace and held at 400°C for 24 h to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0033] S2.2 Severe plastic deformation: The solution-treated Al-Mg alloy was processed by multi-directional free forging. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 800 nm, forming a relatively uniform ultrafine crystalline structure.

[0034] S2.3 Microstructure characterization: Microstructure analysis of the deformed material was performed using EBSD technology. The grains were significantly refined and the microstructure was uniform, meeting the requirements for an ultrafine-grained structure.

[0035] S3: Timeliness Processing Low-temperature aging treatment induces the segregation of Mg at grain boundaries, constructing a stable grain boundary solute network structure, including: S3.1 Low-temperature aging treatment: The obtained ultrafine-grained Al-Mg alloy was placed in an oil bath at 100℃ and kept at that temperature for 5 h to promote the migration of Mg atoms to the grain boundaries, while avoiding the precipitation of the second phase and grain growth.

[0036] S3.2 Microstructure characterization: The microstructure of the Al-Mg alloy after low-temperature aging treatment was systematically analyzed using EBSD and TEM techniques. The results showed that the grain size was still in the ultrafine range, and discontinuous, thick Mg segregation bands were formed at the grain boundaries. No obvious second-phase precipitates were observed, which verified the effectiveness of the low-temperature aging treatment.

[0037] S3.3 Annealing Test: The Al-Mg alloy, after low-temperature aging treatment, was annealed at 200℃ for 24 h, and its grain size and morphology evolution were observed using EBSD technology. It still has an ultrafine grain structure.

[0038] Comparative Example 1 A method for preparing an aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Mg content is 1.0 wt%, the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Mg alloy was placed in a vacuum tube furnace and held at 450°C for 24 h to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0039] S2.2 Severe plastic deformation: The solution-treated Al-Mg alloy was processed by high-pressure torsion. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 200 nm, forming a relatively uniform ultrafine crystalline structure.

[0040] S2.3 Microstructure characterization: The microstructure of the deformed material was analyzed using EBSD technology. The results showed that the grains were significantly refined and the microstructure was uniform, meeting the requirements for an ultrafine-grained structure.

[0041] S3: Annealing test: The Al-Mg alloy, after undergoing severe plastic deformation, was annealed at 200℃ for 24 h. The grain size and morphology evolution were observed using EBSD technology. Figure 4 As shown, from Figure 4 As can be seen, its grain size is approximately 1167 nm, which is no longer an ultrafine crystalline structure.

[0042] Comparative Example 2 A method for preparing an aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Mg content is 10.0 wt%, the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Mg alloy was placed in a vacuum tube furnace and held at 450°C for 24 h to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0043] S2.2 Severe plastic deformation: The solution-treated Al-Mg alloy was processed by high-pressure torsion. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 150 nm, forming a relatively uniform ultrafine crystalline structure.

[0044] S2.3 Microstructure characterization: Microstructure analysis of the deformed material was performed using EBSD technology. The grains were significantly refined and the microstructure was uniform, meeting the requirements for an ultrafine-grained structure.

[0045] S3: Timeliness Processing Low-temperature aging treatment induces the segregation of Mg at grain boundaries, constructing a stable grain boundary solute network structure, including: S3.1 Low-temperature aging treatment: The obtained ultrafine-grained Al-Mg alloy was placed in an oil bath at 150℃ and kept at that temperature for 10 h to promote the migration of Mg atoms to the grain boundaries, while avoiding the precipitation of the second phase and grain growth.

[0046] S3.2 Microstructure characterization: The microstructure of Al-Mg alloy after low-temperature aging was systematically analyzed using EBSD and TEM techniques. The results showed that the grain size was still in the ultrafine grain range, but there was precipitation of a second phase at the grain boundaries and within the grains, which resulted in the absence of a thick Mg segregation zone at the grain boundaries.

[0047] S3.3 Annealing Test: The Al-Mg alloy that had undergone low-temperature aging treatment was annealed at 200℃ for 24 h, and its grain size and morphology evolution were observed using EBSD technology. It was no longer an ultrafine-grained structure.

[0048] Comparative Example 3 A method for preparing an aluminum alloy, comprising: S1: The chemical composition of the aluminum alloy is set as follows: Cu content is 4.0 wt%, and the remainder is Al and unavoidable impurities; S2: Preparation of ultrafine grain structure S2.1 Solution treatment: The aforementioned as-cast Al-Cu alloy was placed in a vacuum tube furnace and held at 525°C for 24 hours to promote the dissolution of the coarse second phase into the matrix, forming a supersaturated solid solution. Subsequently, it was rapidly quenched to room temperature using water cooling to prevent the re-precipitation of the precipitated phase, thus achieving effective solution treatment.

[0049] S2.2 Severe plastic deformation: The solution-treated Al-Cu alloy was processed by high-pressure torsion. Through repeated deformation at room temperature and high strain rate, the grain size was significantly refined to the ultrafine level, approximately 130 nm, forming a relatively uniform ultrafine crystalline structure.

[0050] S2.3 Microstructure characterization: Microstructure analysis of the deformed material was performed using EBSD technology. The grains were significantly refined and the microstructure was uniform, meeting the requirements for an ultrafine-grained structure.

[0051] S3: Timeliness Processing Low-temperature aging treatment induces Cu element segregation at grain boundaries, constructing a stable grain boundary solute network structure, including: S3.1 Low-temperature aging treatment: The obtained ultrafine-grained Al-Cu alloy is placed in an oil bath at 150℃ and kept at that temperature for 10 hours to promote the migration of Cu atoms to the grain boundaries, while avoiding the precipitation of the second phase and grain growth.

[0052] S3.2 Microstructure characterization: The microstructure of the Al-Mg alloy after low-temperature aging was systematically analyzed using EBSD and TEM techniques. The results showed that the grain size was still in the ultrafine grain range, but there was precipitation of a second phase at the grain boundaries and within the grains, which prevented the formation of a thick Cu segregation band at the grain boundaries.

[0053] S3.3 Annealing Test: The Al-Cu alloy, after low-temperature aging treatment, was annealed at 200℃ for 24 h. The grain size and morphology evolution were observed using EBSD technology, and it was no longer an ultrafine-grained structure.

[0054] Experimental Example The grain size and morphology evolution of the aluminum alloys prepared in Examples 1-3 and Comparative Examples 1-3 before and after annealing were observed using electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM). A greater change in grain size before and after annealing indicates poorer thermal stability. The comparative statistical results are shown in Table 1 and... Figure 5 As shown.

[0055] Table 1

[0056] As can be seen from the data in Table 1, although the Al-Mg alloy prepared in Comparative Example 1 met the requirements for ultrafine grain structure after severe plastic deformation treatment, the ultrafine grain structure was destroyed after annealing treatment for 24 hours, indicating that the alloy without low-temperature aging has poor high-temperature stability. The Al-Mg alloy prepared in Comparative Example 2 had excessive Mg doping, resulting in the precipitation of a second phase at the grain boundaries and within the grains, which prevented the formation of a thick Mg segregation band at the grain boundaries. After annealing treatment, the ultrafine grain structure was destroyed. In Comparative Example 3, Cu was used as the doping metal. Although the doping content was the same as in Example 3, a second phase was still precipitated at the grain boundaries and within the grains. After annealing treatment, the ultrafine grain structure was destroyed. This proves that the synergistic control strategy of "low-temperature aging treatment" and "quantitative doping of Mg" adopted in this invention can significantly improve the thermal stability of ultrafine grain materials.

[0057] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. An ultrafine-grained aluminum-magnesium alloy, characterized in that, The chemical composition of the aluminum-magnesium alloy is as follows: Mg content is 4.0-6.0 wt%, with the remainder being Al and unavoidable impurities; The grain size of the aluminum-magnesium alloy is 100-1000 nm; The aluminum-magnesium alloy has a Mg element grain boundary segregation network at the grain boundaries.

2. A method for preparing the ultrafine-grained aluminum-magnesium alloy as described in claim 1, characterized in that, Includes the following steps: As-cast aluminum-magnesium alloys were prepared with a Mg content of 4.0-6.0 wt%. The resulting as-cast aluminum-magnesium alloys were subjected to solution treatment, severe plastic deformation treatment, and aging treatment to obtain the ultrafine-grained aluminum-magnesium alloys.

3. The preparation method according to claim 2, characterized in that, The solution treatment temperature is 400-450℃.

4. The preparation method according to claim 3, characterized in that, The solution treatment time is 18-24 hours.

5. The preparation method according to any one of claims 2-4, characterized in that, The solution treatment also includes a step of water quenching the alloy to room temperature.

6. The preparation method according to claim 2, characterized in that, The treatment method for severe plastic deformation includes any one of the following: high-pressure torsion method, equal diameter angular extrusion method, and multi-directional free forging method.

7. The preparation method according to claim 6, characterized in that, During the severe plastic deformation treatment, the deformation temperature is not higher than 100℃, and the final grain size is refined to 100-1000 nm.

8. The preparation method according to claim 2, characterized in that, The aging treatment is carried out at a temperature of 100-150℃.

9. The preparation method according to claim 8, characterized in that, The processing time for the time-sensitive treatment is 5-10 hours.

10. The application of an ultrafine-grained aluminum-magnesium alloy as described in claim 1 or an aluminum-magnesium alloy prepared by any one of claims 2-9 in an environment with a temperature ≥200°C.

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