A286 iron-based alloy plate with composite gradient structure and preparation method of A286 iron-based alloy plate

Abstract

The invention relates to the field of iron-based alloy material processing and manufacturing, and provides a composite gradient structure A286 iron-based alloy plate and a preparation method thereof.The surface of a solid solution state A286 alloy material is subjected to strengthening treatment through an ultrasonic rolling technology, and a nanocrystalline gradient structure surface layer structure is obtained; and through an aging heat treatment process, the composite gradient structure A286 alloy material with the grain size and the gamma'nano precipitated phase having gradient distribution characteristics is obtained. The composite gradient structure A286 iron-based alloy obtained in the invention has the remarkable characteristics of high strength and high toughness.

Description

Technical Field

[0001] The present invention relates to the field of processing and manufacturing of iron-based alloy materials, and particularly relates to a composite gradient structure A286 iron-based alloy plate and a preparation method thereof. Background Art

[0002] As a typical Fe-Ni-Cr series austenitic precipitation strengthening alloy, A286 iron-based alloy is widely used in key components such as aeroengine turbine disks, compressor disks, and fasteners due to its excellent creep resistance, high-temperature oxidation resistance, and good processing performance.

[0003] The precipitated phase is the most critical strengthening phase in A286 alloy, which significantly affects the mechanical behavior of the alloy. Therefore, by customizing the chemical composition, for example, the publication number CN117737557A discloses a smelting process for large-sized ingots of a low-aluminum and high-titanium iron-based A286 alloy, and the publication number CN116970860A discloses a high-quality A286 superalloy and a new heat treatment method for improving the hardness of A286 superalloy, etc., to control the size, shape, volume fraction, and distribution of the γ' phase Ni3(Al,Ti), and achieve a significant increase in strength.

[0004] In recent years, to meet the requirements of high thrust-to-weight ratio of aeroengines, higher requirements have been put forward for the mechanical properties of engine structural materials. By introducing ultrafine grains and dislocations into the material through cold deformation processes such as cold rolling, cold drawing, and dynamic plastic deformation, the nucleation and size distribution of precipitated phases can be regulated in subsequent aging heat treatment. Although the method of combining cold deformation with aging heat treatment can increase the tensile strength of A286 alloy to more than 1000 MPa, the elongation at break is significantly reduced, generally lower than 15%. This inverse relationship between strength and toughness seriously restricts its application reliability under harsh working conditions. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a high-strength and high-toughness composite gradient structure A286 iron-based alloy plate and a preparation method thereof. By combining ultrasonic rolling and aging heat treatment, a composite gradient structure A286 iron-based alloy plate with gradient distribution characteristics of grain size and γ' nano-precipitated phase is obtained. This plate has the remarkable characteristics of high strength and high toughness.

[0006] To achieve the above object, the technical solution of the present invention is as follows.

[0007] The first aspect of the present invention provides a preparation method for a high-strength and high-toughness composite gradient structure A286 iron-based alloy plate, including the following steps: S1. Process the A286 alloy that has undergone solution heat treatment into a plate; S2. Perform ultrasonic rolling on the sheet in S1 to introduce a gradient nanocrystalline surface layer structure with gradually increasing grain size from the sheet surface to the core in the sheet surface, and obtain the sheet after ultrasonic rolling treatment; S3. Perform aging heat treatment on the sheet after ultrasonic rolling treatment in S2 to prevent coarsening of the nanocrystalline gradient structure and promote precipitation of γ' phase, and obtain the composite gradient structure A286 iron-based alloy sheet.

[0008] Through ultrasonic rolling treatment in the present invention, a gradient nanocrystalline surface layer structure can be formed on the sheet surface, thereby forming a gradient structure surface strengthening layer on the sheet surface. After aging heat treatment, γ' phase fully precipitates and grows, and precipitation of harmful phase η phase is prevented. Furthermore, it is ensured that the gradient nanocrystalline surface layer structure on the sheet surface will not coarsen significantly, thereby effectively preventing reduction of mechanical properties. The composite gradient structure A286 iron-based alloy sheet prepared by the method in the present invention has the characteristics that the grain size, the size and volume fraction of γ' phase all show gradient distribution. Through the mutual cooperation among the above steps in the present invention, the obtained A286 iron-based alloy material has the characteristics of high strength and toughness.

[0009] In the present invention, the parameters of the ultrasonic rolling are: static pressure is 300N - 500N, feed rate is 1000mm / min - 2000mm / min, vibration frequency is 18kHz - 20kHz, amplitude is 16μm - 30μm, and the number of treatment times is 10 - 30 times. Preferably, the static pressure is 400N, the feed rate is 1500mm / min, the processing frequency is 18kHz, and the amplitude is 16μm.

[0010] In the present invention, the parameters of the aging heat treatment are: keep warm at 680°C - 720°C for 2h - 8h. Preferably, the aging heat treatment temperature is 700°C and keep warm for 8h. The precipitation temperature of γ' phase in A286 alloy is 650°C, and η phase precipitates at 720°C. Therefore, at 700°C, it is more conducive to full precipitation of γ' phase and prevention of precipitation of η phase.

[0011] In the present invention, the temperature of the solution heat treatment is 950°C - 980°C, keep warm for 1h - 2h and then water-cool. Preferably, the solution heat treatment temperature is 980°C and keep warm for 1h. The γ' phase alloying elements in A286 alloy dissolve at 830°C, and η phase dissolves at 940°C. The main purpose of the solution heat treatment is to dissolve γ' phase alloying elements into the matrix without precipitation of other phases, and prepare good conditions for the subsequent aging heat treatment.

[0012] In the present invention, the thickness of the sheet is 1mm - 3mm.

[0013] In the present invention, in the aging heat treatment, after keeping warm, air-cool to room temperature.

[0014] In the present invention, during the solution heat treatment, the temperature is raised to 950°C - 980°C at a heating rate of 5°C / min - 10°C / min.

[0015] In the present invention, during the aging heat treatment, the temperature is raised to 680°C - 720°C at a heating rate of 5°C / min - 10°C / min.

[0016] The second aspect of the present invention provides a composite gradient structure A286 iron-based alloy sheet prepared by using the method provided in the first aspect of the present invention.

[0017] Compared with the prior art, the present invention has the following beneficial effects: In the present invention, through ultrasonic rolling treatment, a gradient nanocrystalline surface layer structure with a gradient distribution characteristic of grain size from the surface to the core is formed on the surface layer of the sheet. Then, through aging heat treatment, the γ' phase precipitates sufficiently and the precipitation of the η phase is prevented. The volume fraction of the γ' phase also shows a gradient distribution characteristic from the surface to the core, and the nanocrystalline gradient structure does not coarsen significantly, thereby effectively preventing the reduction of mechanical properties. Through the mutual cooperation among the above various steps, a composite gradient structure A286 iron-based alloy sheet with gradient distribution characteristics of both grain size and γ' nano-precipitation phase is obtained. The A286 iron-based alloy sheet obtained by the present invention has an excellent strength and toughness match. The ultrasonic rolling treatment significantly reduces the surface roughness value of the original cutting surface of the sheet, improves the surface hardness, and introduces residual compressive stress, effectively improving the surface integrity of the material and enhancing the fatigue resistance of the material. This method has a simple process, strong repeatability, and can be extended to other precipitation-strengthened alloy materials of the same type. Description of the Drawings

[0018] Figure 1 It is a microstructural photograph of the A286 alloy material after solution heat treatment in Example 1.

[0019] Figure 2 It is a cross-sectional microstructural photograph of the composite gradient structure A286 iron-based alloy sheet prepared in Example 1; where A is the cross-sectional microstructural photograph, B is the enlarged view of area 1 in A, and C is the enlarged view of area 2 in A.

[0020] Figure 3 It is a cross-sectional microstructural photograph of the A286 iron-based alloy sheet prepared in Comparative Example 1; where A is the cross-sectional microstructural photograph, B is the enlarged view of area 1 in A, and C is the enlarged view of area 2 in A. Detailed Embodiments

[0021] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0022] In the experimental methods described in the embodiments of the present invention, unless otherwise specified, they are all conventional methods. The materials, reagents, etc. used, unless otherwise specified, can all be obtained from commercial channels.

[0023] The present invention introduces a gradient nanocrystalline surface layer structure on the surface of A286 alloy material through ultrasonic rolling, and the grain size gradually increases from the surface to the core. Through aging heat treatment, γ' phase precipitates inside the material. Due to the high density of grain boundaries and dislocations on the surface layer, the nucleation sites and nucleation driving force of the γ' phase are increased, so that the volume fraction of the γ' phase also shows a gradient distribution characteristic from the surface to the core, forming a composite gradient structure with gradient distributions of both grain size and γ' phase. The cooperation between the above processes introduces fine grain strengthening, dislocation strengthening, and precipitation strengthening mechanisms inside the material, significantly improving the strength. At the same time, due to the heterogeneous deformation-induced hardening effect caused by the deformation incompatibility between the strong surface layer and the soft core region, the toughness is improved. The present invention enables the γ' phase to precipitate sufficiently while retaining the gradient nanocrystalline structure through aging heat treatment.

[0024] The room temperature in the embodiments of the present invention refers to 25 °C. The A286 alloy material in the following embodiments, by mass fraction, includes the following components: Ni 24.0% - 27.0%, C 0.08% and below, Si 1.0% and below, Mn 1.0% and below, Cr 13.30% - 16.6%, Mo 2% and below, Ti 1.75% - 2.30%, Al 0.4% and below, P 0.03% and below, S 0.02% and below, V 0.25% - 0.33%, B 0.001%, and the balance is iron.

[0025] A preparation method of a composite gradient structure A286 iron-based alloy sheet, comprising the following steps: S1. Perform solution heat treatment on the A286 alloy material; the solution heat treatment is heated to 950 °C - 980 °C at a heating rate of 5 °C / min - 10 °C / min, the holding time is 1 h - 2 h, and the cooling method is water cooling; preferably, the solution heat treatment is heated to 980 °C at a heating rate of 5 °C / min - 10 °C / min, and the holding time is 1 h. The prepared solution-state A286 alloy material is wire-cut into sheets with a thickness of 1 mm - 3 mm, and then subjected to grinding and polishing treatments.

[0026] S2. Ultrasonic rolling process is carried out on the S1 sheet. The parameters of the ultrasonic rolling process are as follows: the static pressure is 300 N - 500 N, the feed rate of the machining center is 1000 mm / min - 2000 mm / min, preferably 1500 mm / min, the number of treatment times is 20 - 30 times, the ultrasonic amplitude is 16 μm - 30 μm, the ultrasonic frequency is 18 kHz - 20 kHz, and the working ball is a YG6 tungsten carbide ball with a diameter of 10 mm. The nanocrystalline gradient structure prepared with the above ultrasonic rolling process parameters has a surface roughness < 0.3 μm and a nanocrystalline gradient structure layer depth > 200 μm.

[0027] S3. The ultrasonically rolled sheet described in S2 is subjected to aging heat treatment. The aging heat treatment is heated to 680 °C - 720 °C at a heating rate of 5 °C / min - 10 °C / min, the holding time is 2 h - 8 h, and the composite gradient structure A286 iron-based alloy sheet is obtained after air cooling. Preferably, the aging heat treatment temperature is heated to 700 °C at a heating rate of 5 °C / min - 10 °C / min, and the holding time is 8 h. When the aging heat treatment temperature < 680 °C, it is difficult for the γ' phase to precipitate. When the aging heat treatment temperature > 720 °C, not only the harmful phase η will precipitate, but also the surface gradient nanocrystalline structure will be significantly coarsened, thereby reducing the mechanical properties.

[0028] The technical solution of the present invention will be further described below through examples.

[0029] Example 1 A preparation method of a composite gradient structure A286 iron-based alloy sheet, comprising the following steps: S1. Solution heat treatment is carried out on the A286 alloy material. It is heated to 980 °C at a heating rate of 5 °C / min, held for 1 h, and water-cooled to a temperature below 100 °C to obtain a solution-treated A286 alloy material. The structure is as Figure 1 shown. After solution heat treatment, the inside of the sheet is composed of uniform equiaxed grains. The solution-treated A286 alloy material is processed into a flat specimen with a thickness of 2 mm by wire cutting, and then polished to obtain the sheet.

[0030] S2. Ultrasonic rolling process is carried out on the sheet to obtain the ultrasonically rolled sheet. The working ball in the ultrasonic rolling process is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions of the ultrasonic rolling are: the static pressure is 400 N, the feed rate of the machining center is 1500 mm / min, the ultrasonic amplitude is 16 μm, the ultrasonic frequency is 18 kHz, and the number of treatment times is 20 times.

[0031] S3. Subject the sheet after ultrasonic rolling to aging heat treatment. Heat it up to 700 °C at a heating rate of 5 °C / min, hold for 8 h, and then air cool it, i.e., cool it in air to room temperature, to obtain a high-strength and tough composite gradient structure A286 iron-based alloy sheet, and observe its microstructure. The cross-sectional microstructure diagram of the composite gradient structure A286 iron-based alloy sheet is as shown in Figure 2 shown. As can be seen from Figure 2 A in it, the nanocrystalline gradient structure does not show obvious coarsening after aging heat treatment. As can be seen from Figure 2 B and C in it, the transmission electron microscopy images of the surface and the core show that γ' phase precipitates after aging heat treatment. Compared with the core, the γ' phase on the surface is smaller in size and higher in volume fraction, indicating that the γ' phase also exhibits a gradient distribution characteristic, forming a composite gradient structure A286 alloy with gradient distribution characteristics in both grain size and γ' phase.

[0032] Example 2 A preparation method of a composite gradient structure A286 iron-based alloy sheet includes the following steps: S1. Subject the A286 alloy material to solution heat treatment. Heat it up to 980 °C at a heating rate of 5 °C / min, hold for 1 h, and then water cool it to a temperature below 100 °C to obtain a solution-state A286 alloy material. Process the solution heat-treated A286 alloy material into a plate sample with a thickness of 2 mm by wire cutting, and perform grinding and polishing treatments to obtain a sheet.

[0033] S2. Perform ultrasonic rolling on the sheet to obtain a sheet after ultrasonic rolling treatment. The working ball in the ultrasonic rolling process is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions for ultrasonic rolling are: under a static pressure of 300 N, a feed speed of 1500 mm / min, an ultrasonic amplitude of 16 μm, and an ultrasonic frequency of 18 kHz, and the number of treatment times is 20 times.

[0034] S3. Subject the sheet after ultrasonic rolling strengthening treatment to aging heat treatment. Heat it up to 700 °C at a heating rate of 5 °C / min, hold for 8 h, and air cool it to room temperature to obtain a composite gradient structure A286 iron-based alloy sheet.

[0035] Example 3 A preparation method of a composite gradient structure A286 iron-based alloy sheet includes the following steps: S1. Subject the A286 alloy material to solution heat treatment. Heat it up to 980 °C at a heating rate of 10 °C / min, hold for 1 h, and then water cool it to a temperature below 100 °C to obtain a solution-state A286 alloy material. Process the solution heat-treated A286 alloy material into a plate sample with a thickness of 2 mm by wire cutting, and perform grinding and polishing treatments to obtain a sheet.

[0036] S2. Perform ultrasonic rolling on the sheet to obtain the sheet after ultrasonic rolling treatment. The working ball in the ultrasonic rolling process is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions for ultrasonic rolling are as follows: under static pressure of 500 N, feed rate of the machining center of 1500 mm / min, ultrasonic amplitude of 16 μm, and ultrasonic frequency of 18 kHz, the number of treatment times is 20 times.

[0037] S3. Perform aging heat treatment on the flat sample after ultrasonic rolling strengthening treatment. Heat it up to 700 °C at a heating rate of 10 °C / min, hold for 8 h, and air cool to room temperature to obtain the composite gradient structure A286 iron-based alloy sheet.

[0038] Example 4 A preparation method of a composite gradient structure A286 iron-based alloy sheet, comprising the following steps: S1. Perform solution heat treatment on the A286 alloy material. Heat it up to 980 °C at a heating rate of 10 °C / min, hold for 1 h, and water cool to a temperature below 100 °C to obtain the solution-state A286 alloy material. Process the A286 alloy material after solution heat treatment into a flat sample with a thickness of 2 mm by wire cutting, and perform grinding and polishing treatments to obtain the sheet.

[0039] S2. Perform ultrasonic rolling on the sheet to obtain the sheet after ultrasonic rolling treatment. The working ball in the ultrasonic rolling process is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions for ultrasonic rolling are as follows: under static pressure of 400 N, feed rate of the machining center of 1000 mm / min, ultrasonic amplitude of 16 μm, and ultrasonic frequency of 18 kHz, the number of treatment times is 20 times.

[0040] S3. Perform aging heat treatment on the sheet after ultrasonic rolling strengthening treatment. Heat it up to 700 °C at a heating rate of 10 °C / min, hold for 2 h, and air cool to room temperature to obtain the composite gradient structure A286 iron-based alloy sheet.

[0041] Example 5 A preparation method of a composite gradient structure A286 iron-based alloy sheet, comprising the following steps: S1. Perform solution heat treatment on the A286 alloy material. Heat it up to 980 °C at a heating rate of 5 °C / min, hold for 1 h, and water cool to a temperature below 100 °C to obtain the solution-state A286 alloy material. Process the A286 alloy material after solution heat treatment into a flat sample with a thickness of 2 mm by wire cutting, and perform grinding and polishing treatments to obtain the sheet.

[0042] S2. The sheet material is subjected to ultrasonic rolling processing to obtain the sheet material after ultrasonic rolling treatment. Among them, the working ball in the ultrasonic rolling processing is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions of ultrasonic rolling are as follows: under static pressure of 400 N, the feed speed of the machining center is 1500 mm / min, the ultrasonic amplitude is 16 μm, and the ultrasonic frequency is 18 kHz. The number of treatment times is 20 times.

[0043] S3. The flat specimen after ultrasonic rolling strengthening treatment is subjected to aging heat treatment. It is heated to 680 °C at a heating rate of 5 °C / min, held for 2 h, and air-cooled to room temperature to obtain a composite gradient structure A286 iron-based alloy sheet.

[0044] Comparative Example 1 A method for preparing an A286 iron-based alloy sheet includes the following steps: S1. The A286 alloy material is subjected to solution heat treatment. It is heated to 980 °C at a heating rate of 5 °C / min, held for 1 h, and water-cooled to a temperature below 100 °C to obtain a solution-state A286 alloy material. The A286 alloy material after solution heat treatment is processed into a flat specimen with a thickness of 2 mm by wire cutting, and then subjected to grinding and polishing treatment to obtain a sheet.

[0045] S2. The sheet material is subjected to ultrasonic rolling processing to obtain the sheet material after ultrasonic rolling treatment. Among them, the working ball in the ultrasonic rolling processing is a YG6 tungsten carbide ball with a diameter of 10 mm. The conditions of ultrasonic rolling are as follows: under static pressure of 400 N, the feed speed of the machining center is 1500 mm / min, the ultrasonic amplitude is 16 μm, and the ultrasonic frequency is 18 kHz. The number of treatment times is 20 times. The microstructure of the sheet material after ultrasonic rolling treatment is observed. The observation surface is the side surface of the rolled sheet. The metallographic diagram of the cross-section of the sheet material after ultrasonic rolling treatment is as Figure 3 shown. It can be seen from the figure that fine nanocrystals are generated on the surface of the A286 alloy sheet after rolling. As the depth from the surface increases, the grain size gradually increases, forming a nanocrystalline gradient structure with a gradient distribution of grain sizes. The thickness of the deformation layer is about 400 μm, indicating that a gradient structure of grain size distribution is formed.

[0046] The A286 iron-based alloy sheets obtained in Examples 1 to 5 and Comparative Example 1 are subjected to wire cutting to obtain "dog bone"-shaped tensile specimens, and room temperature tensile test performance tests are carried out. The performance test method is operated in accordance with GB / T 228.1-2010 "Metallic materials-Tensile testing-Part 1: Method of test at room temperature". The test results are shown in Table 1.

[0047] As can be seen from the data in Table 1, after ultrasonic rolling and aging heat treatment, the present invention can significantly increase the yield strength of A286 iron-based alloy plates to over 830 MPa and the tensile strength to over 1000 MPa, and the elongation after fracture remains above 17%, achieving excellent strength-ductility matching.

[0048] Table 1 Mechanical properties of different A286 iron-based alloy plates Note: The solution-treated state refers to the plate after solution heat treatment in S1 of Example 1.

[0049] The above are only several specific preferred embodiments of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in the present application should be covered by the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a composite gradient structure A286 iron-based alloy sheet, characterized in that: The following steps are involved: S1, processing the A286 alloy after solution heat treatment into plates; S2, subjecting the plate in S1 to ultrasonic rolling treatment, introducing a gradient nano-surface structure on the surface of the plate, in which the grain size gradually increases from the surface of the plate to the core, to obtain a plate after ultrasonic rolling treatment; S3, subjecting the plate subjected to the ultrasonic rolling treatment in S2 to an aging heat treatment to precipitate the γ' phase and prevent the precipitation of the η phase, thereby obtaining the composite gradient structure A286 iron-based alloy plate.

2. The preparation method according to claim 1, characterized in that: The parameters of the ultrasonic rolling are: static pressure of 300N~500N, feed speed of 1000mm / min~2000mm / min, vibration frequency of 18kHz~20kHz, amplitude of 16μm~30μm, and processing times of 10 times~30 times.

3. The preparation method according to claim 1, characterized in that: The parameters of the aging heat treatment are: temperature of 680°C to 720°C and holding time of 2h to 8h.

4. The preparation method according to claim 1, characterized in that: The temperature of the solution heat treatment is 950° C. to 980° C., and the treatment is carried out by water cooling after being kept at this temperature for 1 h to 2 h.

5. The preparation method according to claim 1, characterized in that: The thickness of the plate is 1 mm to 3 mm.

6. The preparation method according to claim 3, characterized in that: During the aging heat treatment, the material is air-cooled to room temperature after being kept warm.

7. The preparation method according to claim 4, characterized in that: In the solution heat treatment, the temperature is increased to 950° C. to 980° C. at a heating rate of 5° C. / min to 10° C. / min.

8. The preparation method according to claim 3, characterized in that: In the aging heat treatment, the temperature is increased to 680° C. to 720° C. at a heating rate of 5° C. / min to 10° C. / min.

9. A composite gradient structure A286 iron-based alloy plate prepared by the method described in any one of claims 1 to 8.

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