Small-angle grain boundary oxide film based on surface of surface layer Al-containing alloy part and preparation method and application thereof

Abstract

The application discloses a small-angle grain boundary oxidation film based on a surface of a surface layer Al-containing alloy piece and a preparation method and application thereof, and belongs to the technical field of material surface modification and coating preparation. The preferential orientation nucleation of aluminum oxide and the oxidation film thickening treatment are used to make the crystal grains in the obtained oxidation film have specific preferential orientation, the grain boundaries between the crystal grains are mainly small-angle grain boundaries, the internal diffusion of oxygen atoms is greatly slowed down, and therefore the high-temperature oxidation resistance of the surface layer Al-containing alloy piece is improved. The application solves the technical problem that the surface layer Al-containing alloy piece is oxidized too fast at high temperature and fails in advance.

Description

Technical Field

[0001] This invention belongs to the field of material surface modification and coating preparation technology, specifically relating to a small-angle grain boundary oxide film on the surface of Al-containing alloy parts, its preparation method and application. Background Technology

[0002] Metals face severe oxidation problems during high-temperature service, which can lead to catastrophic consequences. However, Al-containing alloys can form an α-Al₂O₃ oxide film at high temperatures, which can effectively hinder the internal diffusion of oxygen atoms, thereby improving the high-temperature oxidation resistance of the metal matrix.

[0003] Since grain boundaries are the main channels for oxygen atom diffusion in α-Al2O3 oxide films, the current method to improve the high-temperature oxidation resistance of Al-containing alloys is to increase the grain size of aluminum oxide in the oxide film through low oxygen partial pressure pretreatment, thereby reducing the number of grain boundaries. However, this method has limited effect on improving oxidation resistance, and excessively large oxide film grain size can also lead to oxide film cracking, causing the oxide film to lose its oxidation resistance.

[0004] The prior art patent CN112281107A discloses a protective oxide film with a double-layer structure, wherein the outer layer is a continuous and dense chromium oxide film with a thickness of 3.8-6.0μm, and the inner layer is a discontinuous aluminum oxide inner oxide. However, the oxide film thickness is uneven and the grain size distribution is uneven, which significantly affects the oxidation resistance of Al-containing alloy parts at high temperatures. Summary of the Invention

[0005] In order to overcome the shortcomings of the prior art, the present invention aims to provide a small-angle grain boundary oxide film on the surface of Al-containing alloy parts, its preparation method and application, which solves the technical problem that Al-containing alloy parts oxidize too quickly at high temperature and fail prematurely.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention discloses a small-angle grain boundary oxide film on the surface of an Al-containing alloy part. The oxide film is formed by heat-treating the Al-containing alloy part under certain oxygen partial pressure conditions, resulting in a dense oxide film with small-angle grain boundaries and no through pores on the surface of the Al-containing alloy part.

[0008] Preferably, the small-angle grain boundary oxide film is formed by grains growing along a specific crystal direction, with the proportion of grains deviating from this direction by 0° to 15° not less than 60%, the grain boundary angle of the oxide film not exceeding 15°, and the proportion of small-angle grain boundaries not less than 60%; the thickness of the oxide film is 100 to 2000 nm, and the grain size of the oxide film is 200 to 2000 nm.

[0009] Preferably, the oxide film is prepared by heat treatment of the surface Al-containing alloy part under an oxygen partial pressure atmosphere dominated by argon.

[0010] This invention also discloses a method for preparing the above-mentioned small-angle grain boundary oxide film, comprising the following steps:

[0011] 1) Perform pre-oxidation treatment on the Al-containing alloy parts after pretreatment to preferentially nucleate the crystal orientation until the oxide film completely covers the surface of the alloy parts;

[0012] 2) The Al-containing alloy parts with pre-oxidation treatment are subjected to oxide film thickening treatment to obtain a small-angle grain boundary oxide film with a certain thickness.

[0013] Preferably, the pretreatment described in step 1) is a fresh surface exposure treatment, which refers to the removal of the original oxide film, impurities, etc. on the material surface. Specific methods include, but are not limited to, mechanical polishing, acid washing, alkaline washing, etc. on the surface.

[0014] Preferably, in step 1), the pre-oxidation treatment is as follows: the Al-containing alloy part is placed in an atmosphere furnace, the furnace pressure is evacuated to 1Pa-5Pa, high-purity argon gas with an oxygen content of 0.001ppm-0.02ppm is filled, and the temperature is maintained at 900℃-1200℃ for 1h-100h, with a heating and cooling rate of 1-20℃ / h.

[0015] More preferably, in step 1), the pre-oxidation treatment is as follows: the surface Al-containing alloy part is placed in an atmosphere furnace, the furnace pressure is evacuated to 1 Pa, high-purity argon gas with an oxygen content of 0.005 ppm is filled, and the temperature is maintained at 1200℃ for 100 h, with a heating and cooling rate of 1℃ / h.

[0016] The purpose of this step is to adjust the oxygen partial pressure to be higher than the critical oxygen partial pressure for alumina nucleation but lower than the critical oxygen partial pressure for the second most effusive nucleation direction of alumina. This high-temperature treatment process facilitates the reaction of Al elements on the alloy surface with oxygen to form alumina (Al₂O₃) nuclei. Because the oxygen content in the atmosphere is extremely low, this process is controllable and helps to form alumina nuclei with specific crystal orientations. The critical oxygen partial pressure for alumina nucleation refers to the lowest oxygen partial pressure required for alumina nucleation at the current heat treatment temperature; the second most effusive nucleation direction of alumina refers to the crystal orientation along which alumina nucleates, requiring energy second only to that required along the most effusive nucleation direction; the critical oxygen partial pressure for the second most effusive nucleation direction of alumina refers to the oxygen partial pressure corresponding to the energy required for alumina nucleation along that crystal orientation at the current heat treatment temperature.

[0017] Preferably, in step 2), the oxide film thickening treatment is as follows: the gas pressure in the furnace is evacuated back to 1Pa-5Pa, filled with high-purity argon gas with an oxygen content of 20ppm-150ppm, and kept at 900℃-1200℃ for 1h-100h, with a heating and cooling rate of 1-20℃ / h.

[0018] More preferably, in step 2), the oxide film thickening treatment is as follows: the gas pressure in the furnace is evacuated back to 1 Pa, filled with high-purity argon gas with an oxygen content of 20 ppm, and kept at 1200℃ for 10 h, with a heating and cooling rate of 1℃ / h.

[0019] The purpose of this step is to adjust the oxygen partial pressure to above the critical oxygen partial pressure for alumina nucleation. This high-temperature treatment allows the alumina layer to continue growing on the alloy surface, forming a thicker oxide film. Compared to the pre-oxidation treatment in step 1), this step involves a higher oxygen content, the aim of which is to accelerate the growth of the alumina layer and make it thicker.

[0020] The present invention also discloses the application of the above-mentioned small-angle grain boundary oxide film in Al-containing alloy parts.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention discloses a small-angle grain boundary oxide film on the surface of an Al-containing alloy component. The oxide film exhibits small-angle grain boundaries and is dense with no through-pores. The innovation of this invention lies in heat-treating the Al-containing alloy component under certain oxygen partial pressure conditions, causing the oxide film formed on the surface of the Al-containing alloy component to exhibit small-angle grain boundaries and dense with no through-pores. This significantly slows down the internal diffusion of oxygen atoms, thereby improving the high-temperature oxidation resistance of the Al-containing alloy component.

[0023] Furthermore, the grains of the small-angle grain boundary oxide film grow along a specific crystal orientation, with at least 60% of the grains deviating from this orientation by 0° to 15°. This dense structure, devoid of through-holes, enhances the protective performance of the oxide film and facilitates the formation of a highly ordered structure. This results in a specific preferred orientation of the grains in the obtained oxide film, making small-angle grain boundaries the dominant feature between grains. The grain boundary angle of the small-angle grain boundary oxide film does not exceed 15°, and the proportion of small-angle grain boundaries is at least 60%, making the oxide film more dense and reducing porosity and defects. The grain size of the small-angle grain boundary oxide film is 200–2000 nm, and the thickness is 100–2000 nm. These parameters ensure that the thickness of the oxide film is sufficient to provide effective protection, while also ensuring a moderate grain size, which is conducive to forming a uniform and dense oxide film structure.

[0024] This invention also discloses a method for preparing a small-angle grain boundary oxide film on the surface of an Al-containing alloy part. First, a pre-oxidation treatment is performed on the pretreated Al-containing alloy part to promote preferred nucleation, which helps to form an initial oxide film with alumina nuclei of specific crystal orientations on the alloy surface. Second, an oxide film thickening treatment is performed to accelerate the growth of the alumina layer under higher oxygen partial pressure, thereby increasing its thickness while maintaining the characteristic of grain growth along a specific crystal orientation. This improves the coverage and protection of the oxide film, effectively isolating the alloy substrate from the external environment, and thus improving the high-temperature oxidation resistance of the alloy part. The two-step oxidation process ensures the uniformity and density of the oxide film.

[0025] Furthermore, by placing the Al-containing alloy parts in an atmosphere furnace, evacuating the furnace pressure to 1-5 Pa, filling it with high-purity argon gas with an oxygen content of 0.001-0.02 ppm, and holding at 900℃-1200℃ for 1-100 hours with a heating / cooling rate of 1-20℃ / h, a pre-oxidation treatment is performed. This adjusts the oxygen partial pressure to be higher than the critical oxygen partial pressure for alumina nucleation but lower than the critical oxygen partial pressure for the second most favorable nucleation orientation of alumina. Such oxygen partial pressure conditions help induce preferential nucleation of alumina grains in a specific direction, preventing nucleation in other orientations, thus achieving preferred orientation. This ensures that alumina grains can nucleate and grow according to the predetermined preferred orientation. The key to this step is the precise control of the oxygen partial pressure and heat treatment conditions, so that the grains in the obtained oxide film have a specific preferred orientation. This results in small-angle grain boundaries dominating the grain boundaries, greatly slowing down the internal diffusion of oxygen atoms and improving the high-temperature oxidation resistance of the Al-containing alloy parts.

[0026] Furthermore, by placing the Al-containing alloy parts in an atmosphere furnace, evacuating the furnace pressure to 1-5 Pa, filling it with high-purity argon gas with an oxygen content of 20-150 ppm, and holding it at 900℃-1200℃ for 1-100 h with a heating / cooling rate of 1-20℃ / h, an oxide film thickening treatment is performed. This adjusts the oxygen partial pressure to be higher than the critical oxygen partial pressure for alumina nucleation, promoting the continued growth and thickening of the alumina layer on the alloy surface. While the oxygen partial pressure is higher in this step, it still needs to be maintained above the critical oxygen partial pressure for alumina nucleation. The purpose of this step is to accelerate the growth rate of the alumina layer to obtain the required oxide film thickness, allowing the oxide film to better block the erosion of the Al-containing alloy parts by oxygen and other corrosive substances in the external environment, thereby significantly improving the high-temperature oxidation resistance of the alloy parts. In summary, the small-angle grain boundary oxide film prepared by the method of this application solves the technical problem of premature failure of Al-containing alloy parts due to excessive oxidation at high temperatures. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an Al-containing alloy component on the surface of the small-angle grain boundary oxide film of the present invention;

[0028] Figure 2 This is a diagram showing the surface EBSD characterization results of the small-angle grain boundary oxide film of the present invention;

[0029] Figure 3 This diagram shows the proportion of grain boundaries at different angles in the small-angle grain boundary oxide film of the present invention.

[0030] Figure 4 The image shows the fracture surface morphology of the oxide film on the surface of an Al-containing alloy part that has not undergone pre-oxidation treatment or oxide film thickening treatment.

[0031] Figure 5 This is a cross-sectional morphology of the oxide film on the surface of an Al-containing alloy part that has undergone pre-oxidation and oxide film thickening treatment. Detailed Implementation

[0032] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0033] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0034] The present invention will be further described in detail below with reference to embodiments:

[0035] Example 1

[0036] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0037] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0038] 2) Pre-oxidation treatment with preferred nucleation: The Al-containing alloy parts on the surface are placed in an atmosphere furnace, and the furnace pressure is evacuated to 1 Pa to remove air and other impurities, ensuring that subsequent processing is carried out in a pure environment. High-purity argon gas with an oxygen content of 0.005 ppm is used as the main atmosphere, with a very small amount of oxygen added to initiate and control the oxidation reaction on the alloy surface. The temperature is held at 1200℃ for 10 hours, with heating and cooling rates of 1℃ / h. This rate control ensures that the alloy parts will not develop thermal stress or cracks due to excessively rapid temperature changes during heating and cooling.

[0039] 3) Oxide film thickening treatment: The furnace pressure was evacuated to 1 Pa to ensure that subsequent treatments were carried out in a pure environment. High-purity argon gas with an oxygen content of 20 ppm was filled in, and the furnace was held at 1200℃ for 10 hours. The heating and cooling rates were both 1℃ / h to ensure the stability of the alloy parts during heating and cooling. A dense alumina oxide film with small-angle grain boundary characteristics was obtained, with a film thickness of 2000 nm. Figure 2 The characterization results of EBSD on the surface of this oxide film show that its grain size is approximately 600 nm, exhibiting significant phase preference. Figure 3 The percentage of grain boundaries at different angles shows that small-angle grain boundaries account for approximately 72%.

[0040] The surface Al-containing alloy parts without pre-oxidation treatment and oxide film thickening treatment, and the surface Al-containing alloy parts of Example 1 with pre-oxidation treatment and oxide film thickening treatment were subjected to a high-temperature oxidation test at 1200°C for 100 hours. Figure 4 The image shows the fracture surface morphology of the oxide film on an Al-containing alloy part without pre-oxidation treatment or oxide film thickening treatment. Figure 5 This image shows the fracture surface morphology of the oxide film on an Al-containing alloy part that has undergone pre-oxidation and oxide film thickening treatment. Figure 4 and Figure 5 It can be seen that the oxide film thickness was significantly reduced by about 89 times after pre-oxidation treatment and oxide film thickening treatment, which significantly slowed down its oxidation rate. Moreover, the oxide film is a continuous alumina film, which further protects the surface Al-containing alloy substrate and improves the high-temperature oxidation resistance of the alloy.

[0041] Example 2

[0042] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0043] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0044] 2) Pre-oxidation treatment for preferred nucleation of crystal orientation: Place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 5 Pa, fill with high-purity argon gas with an oxygen content of 0.02 ppm, and hold at 1000℃ for 20 h with a heating and cooling rate of 10℃ / h.

[0045] 3) Oxide film thickening treatment: The gas pressure in the furnace was evacuated to 2 Pa and filled with high-purity argon gas with an oxygen content of 75 ppm. The furnace was held at 1000℃ for 10 h with a heating and cooling rate of 10℃ / h to obtain a dense alumina oxide film with small-angle grain boundary characteristics. The oxide film was 1000 nm thick, with a grain size of 800 nm and a small-angle grain boundary ratio of 69%. This oxide film slowed down the oxidation rate of the Al alloy parts on the surface by 70 times at 1000℃.

[0046] Example 3

[0047] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0048] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0049] 2) Pre-oxidation treatment for preferred nucleation of crystal orientation: Place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 5 Pa, fill with high-purity argon gas with an oxygen content of 0.001 ppm, and hold at 1150℃ for 15 h with a heating and cooling rate of 20℃ / h.

[0050] 3) Oxide film thickening treatment: The gas pressure in the furnace was evacuated to 5 Pa, and high-purity argon with an oxygen content of 150 ppm was filled. The furnace was held at 1150℃ for 5 h with a heating and cooling rate of 20℃ / h to obtain a dense alumina oxide film with small-angle grain boundary characteristics. The oxide film was 800 nm thick, with a grain size of 500 nm and a small-angle grain boundary ratio of 77%. This oxide film slowed down the oxidation rate of the Al alloy part on the surface by 74 times at 1150℃.

[0051] Example 4

[0052] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0053] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0054] 2) Pre-oxidation treatment for preferred nucleation of crystal orientation: Place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 2 Pa, fill with high-purity argon gas with an oxygen content of 0.003 ppm, and hold at 900℃ for 1 h, with heating and cooling rates of 10℃ / h.

[0055] 3) Oxide film thickening treatment: The gas pressure in the furnace was evacuated to 2 Pa and filled with high-purity argon gas with an oxygen content of 40 ppm. The furnace was held at 900℃ for 1 h with a heating and cooling rate of 10℃ / h. A dense alumina oxide film with small-angle grain boundary characteristics was obtained. The oxide film was 100 nm thick, with a grain size of 200 nm and a small-angle grain boundary ratio of 62%. This oxide film slowed down the oxidation rate of the Al alloy part on the surface by 39 times at 900℃.

[0056] Example 5

[0057] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0058] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0059] 2) Pre-oxidation treatment for preferred nucleation of crystal orientation: Place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 3 Pa, fill with high-purity argon gas with an oxygen content of 0.003 ppm, and hold at 900℃ for 50.5 h, with heating and cooling rates of 10℃ / h.

[0060] 3) Oxide film thickening treatment: The gas pressure in the furnace was evacuated to 3 Pa and filled with high-purity argon gas with an oxygen content of 80 ppm. The furnace was held at 1150℃ for 50.5 h with a heating and cooling rate of 10℃ / h. A dense alumina oxide film with small-angle grain boundary characteristics was obtained. The oxide film was 300 nm thick, with a grain size of 200 nm and a small-angle grain boundary ratio of 75%. This oxide film slowed down the oxidation rate of the Al alloy part on the surface by 55 times at 1150℃.

[0061] Example 6

[0062] The method for preparing a small-angle grain boundary oxide film using an Al-containing alloy surface as a substrate includes the following steps:

[0063] 1) Fresh surface exposure treatment of Al alloy parts: Use 200-2000 grit sandpaper to grind the Al alloy parts, then use 0.5μm diamond polishing agent to polish the Al alloy parts, and then clean the Al alloy parts with deionized water.

[0064] 2) Pre-oxidation treatment for preferred nucleation of crystal orientation: Place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 4 Pa, fill with high-purity argon gas with an oxygen content of 0.005 ppm, and hold at 900℃ for 100 h, with heating and cooling rates of 10℃ / h.

[0065] 3) Oxide film thickening treatment: The gas pressure in the furnace was evacuated to 4 Pa ​​and filled with high-purity argon gas with an oxygen content of 122.5 ppm. The furnace was held at 1150℃ for 100 h with a heating and cooling rate of 10℃ / h. A dense alumina oxide film with small-angle grain boundary characteristics was obtained. The oxide film was 100 nm thick, with a grain size of 500 nm and a small-angle grain boundary ratio of 80%. This oxide film slowed down the oxidation rate of the Al alloy part on the surface by 45 times at 1150℃.

[0066] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A small-angle grain boundary oxide film on the surface of an Al-containing alloy part, characterized in that, The oxide film is formed by heat treatment of Al-containing alloy parts under certain oxygen partial pressure conditions, resulting in a dense oxide film with small grain boundaries and no through pores on the surface of the Al-containing alloy parts. The certain oxygen partial pressure conditions include pre-oxidation treatment and oxide film thickening treatment. The pre-oxidation treatment involves placing the Al-containing alloy parts in an atmosphere furnace, evacuating the furnace pressure to 1 Pa-5 Pa, filling it with high-purity argon gas with an oxygen content of 0.001 ppm-0.02 ppm, and holding it at 900℃-1200℃ for 1 h-100 h with a heating and cooling rate of 1-20℃ / h. The oxide film thickening treatment involves evacuating the furnace pressure back to 1 Pa-5 Pa, filling it with high-purity argon gas with an oxygen content of 20 ppm-150 ppm, and holding it at 900℃-1200℃ for 1 h-100 h with a heating and cooling rate of 1-20℃ / h.

2. The small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to claim 1, characterized in that, Small-angle grain boundary oxide films are formed by grains growing along a specific crystal orientation, with grains deviating from this orientation by 0° to 15° accounting for no less than 60%, grain boundary angles of the oxide film not exceeding 15°, and small-angle grain boundaries accounting for no less than 60%; the thickness of the oxide film is 100 to 2000 nm, and the grain size of the oxide film is 200 to 2000 nm.

3. The small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to claim 1, characterized in that, The oxide film was prepared by heat treatment of the surface Al-containing alloy parts under an oxygen partial pressure atmosphere dominated by argon.

4. A method for preparing a small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to any one of claims 1 to 3, characterized in that, Includes the following steps: 1) Perform a pre-oxidation treatment on the Al-containing alloy parts after pretreatment to preferentially nucleate the crystal orientation until the oxide film completely covers the surface of the alloy parts; the pre-oxidation treatment is as follows: place the Al-containing alloy parts in an atmosphere furnace and evacuate the furnace pressure to 1 Pa. 5 Pa, oxygen content is 0.001 ppm 0.02ppm high-purity argon gas was kept at 900℃~1200℃ for 1h~100h, with a heating and cooling rate of 1~20℃ / h; 2) The Al-containing alloy parts with the above pre-oxidation treatment are subjected to an oxide film thickening treatment to obtain a small-angle grain boundary oxide film with a certain thickness; the oxide film thickening treatment is as follows: the gas pressure in the furnace is evacuated back to 1 Pa. 5Pa, oxygen content is 20ppm High-purity argon gas of 150 ppm is used to maintain the temperature at 900℃~1200℃ for 1h~100h, with a heating and cooling rate of 1~20℃ / h.

5. The method for preparing a small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to claim 4, characterized in that, In step 1), the pre-oxidation treatment is as follows: place the Al-containing alloy parts on the surface in an atmosphere furnace, evacuate the gas pressure in the furnace to 1 Pa, fill with high-purity argon gas with an oxygen content of 0.005 ppm, and hold at 1200℃ for 100 h, with a heating and cooling rate of 1℃ / h.

6. The method for preparing a small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to claim 4, characterized in that, In step 2), the oxide film thickening treatment is as follows: the gas pressure in the furnace is evacuated back to 1 Pa, filled with high-purity argon gas with an oxygen content of 20 ppm, and kept at 1200℃ for 10 h with a heating and cooling rate of 1℃ / h.

7. The method for preparing a small-angle grain boundary oxide film on the surface of an Al-containing alloy part according to claim 4, characterized in that, In step 1), the pretreatment includes: exposing the surface of the Al alloy part to fresh surface.

8. The application of the small-angle grain boundary oxide film according to any one of claims 1 to 3 in Al-containing alloy parts.

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