Al-Mg-Ta composite powder-based aluminum alloy laser additive repair method

Abstract

The present application relates to the technical fields of laser additive repair, in particular to an aluminum alloy laser additive repair method based on Al-Mg-Ta composite powder, comprising the following steps: preparing Al-Mg-Ta powder by using pre-alloyed powder preparation method; vacuum drying the prepared Al-Mg-Ta powder after sieving; polishing the damaged area of the aluminum alloy substrate before repair; repairing the aluminum alloy substrate by using laser directed energy deposition technology; and performing aging heat treatment on the damaged area of the aluminum alloy substrate. The aluminum alloy laser additive repair method based on Al-Mg-Ta composite powder uses Al-Mg-Ta powder as the repair material, repairs the aluminum alloy substrate by using laser directed energy deposition technology, generates in-situ Al3Ta phase with dispersed distribution during the laser additive manufacturing process, the existence of such particles influences the solidification behavior, promotes grain refinement to a certain extent, and helps to inhibit the epitaxial growth of columnar crystals, thereby promoting the transformation of the structure to equiaxed grains and improving the mechanical properties of the material.

Description

Technical Field

[0001] This invention relates to the field of laser additive repair technology, and in particular to a laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder. Background Technology

[0002] 6-series aluminum alloys, such as 6061, are widely used in the rail transportation field due to their high specific strength, good corrosion resistance, and machinability. However, during long-term service, these components inevitably suffer from wear, fatigue loads, and impacts, easily leading to damage such as cracks and wear pits in localized areas. Traditional repair methods to address these issues mainly include machining repair, welding repair, thermal spraying, and electroplating. While these methods can restore the dimensions or surface properties of parts to some extent, they generally suffer from insufficient interfacial bonding strength, large heat-affected zones, high residual stress, and difficulties in matching the microstructure and properties of the repaired area, making it difficult to meet the service requirements of high-performance structural components.

[0003] In recent years, laser additive manufacturing technology, especially laser directional energy deposition technology, has been gradually applied to the remanufacturing and repair of metal components due to its advantages such as concentrated heat input, high forming accuracy and the ability to achieve metallurgical bonding.

[0004] Currently, for laser additive repair of aluminum alloys, commonly used powder materials are mostly Al-Si alloys (such as AlSi10Mg and AlSi12). These materials have advantages in forming stability due to their good fluidity and low hot cracking sensitivity; however, their strengthening mechanism mainly relies on eutectic structure and lacks effective precipitation strengthening ability, resulting in the strength and hardness of the repaired area generally being lower than that of the matrix material, making it difficult to meet the requirements of high-strength service. Furthermore, existing technologies mostly focus on process parameter control, while the targeted design of the repair material system and its synergistic effect with the additive manufacturing process are relatively insufficient. Summary of the Invention

[0005] The purpose of this invention is to address the shortcomings of existing technologies by proposing a laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder.

[0006] To achieve the above objectives, the present invention adopts the following technical solution, comprising the following steps:

[0007] S1. Al-Mg-Ta powder was prepared using a pre-alloyed powder preparation method;

[0008] S2. The prepared Al–Mg–Ta powder is sieved and then vacuum dried;

[0009] S3. Grind the damaged area of ​​the aluminum alloy substrate before repair;

[0010] S4. Laser-guided energy deposition technology is used to repair the aluminum alloy substrate, and the diffusely distributed Al3Ta phase is generated in situ during the laser additive manufacturing process.

[0011] S5. The damaged area of ​​the aluminum alloy matrix is ​​subjected to aging heat treatment, and fine dispersed strengthening phase β is precipitated in the Al-Mg-Ta alloy after heat treatment;

[0012] This invention has found that Ta can effectively promote the formation of the dispersion strengthening phase (Al3Ta phase) and play a heterogeneous nucleation role within this range, while avoiding the formation of coarse intermetallic compounds; Mg and Si are used to balance strengthening effect and solidification stability; Cu and Fe are controlled within this reasonable range to avoid the formation of undesirable phases.

[0013] Preferably, the S1 method involves weighing and mixing the following elemental raw materials by mass percentage: Mg 0.8%–1.8%, Ta 1.0%–3.0%, Si 0.4%–1.2%, Cu 0.1%–0.6%, Fe 0.1%–0.5%, with the balance being metallic Al. The raw materials are then added to a vacuum melting furnace for melting. Argon gas is used as a protective atmosphere to atomize the molten alloy into powder, resulting in Al–Mg–Ta powder with a particle size distribution of 53–105 μm.

[0014] Preferably, the drying conditions for the Al–Mg–Ta powder in S2 are: vacuum drying temperature of 120°C and drying time of 2 hours.

[0015] Preferably, after sieving, the Al–Mg–Ta powder in S2 yields Al–Mg–Ta powder with a particle size distribution of 60–85 μm.

[0016] Preferably, the process of S3 is as follows: the substrate surface is polished with sandpaper to remove processing marks and surface oxide layer, and anhydrous ethanol is used for cleaning to remove surface oxide film and contaminants;

[0017] Preferably, during the S4 laser additive manufacturing process, the aluminum alloy matrix undergoes an in-situ reaction to generate a diffusely distributed Al3Ta phase;

[0018] Preferably, the process parameters for S4 are: laser power of 1000W, scanning speed of 420mm / min, laser spot diameter of 2mm, powder feeding rate of 15g / min, layer thickness of 0.5mm, overlap rate of 50%, powder feeding gas flow rate of 5L / min, and protective gas of argon.

[0019] Preferably, after S5 heat treatment, fine, dispersed strengthening phase β precipitates in the Al-Mg-Ta alloy;

[0020] Preferably, the specific process parameters for S5 are: heat preservation at 160°C for 30 hours, followed by air cooling to room temperature;

[0021] Preferably, after S5, the phase composition of the sample is analyzed using an Empyrean X-ray diffractometer (XRD); the microstructure of the sample is characterized using a Lecia DMi8 A inverted metallurgical microscope, a Zeiss-SUPRA 55 scanning electron microscope (SEM) and its equipped electron backscattered diffraction (EBSD) system; the mechanical properties of the sample are tested using an MTSE43.104 universal testing machine (tensile rate 0.5 mm / min) and an FM-100 microhardness tester (100 g load for 15 s), and both tensile and hardness tests are repeated 3 times to ensure the reliability of the results.

[0022] The present invention has the following beneficial effects:

[0023] Compared with existing technologies, this laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder introduces Ta particles into the Al-Mg alloy, and generates a diffusely distributed Al3Ta phase in situ during the laser additive manufacturing process. The presence of these particles affects the solidification behavior, promotes grain refinement to a certain extent, and helps to suppress the epitaxial growth of columnar crystals, thereby promoting the transformation of the microstructure to equiaxed crystals.

[0024] Compared with existing technologies, this laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder, after aging heat treatment, precipitates fine, dispersed strengthening phase "β" in the Al-Mg-Ta alloy, further improving the mechanical properties of the material.

[0025] Compared with existing technologies, this laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder has a wide range of applications, and can be used for the repair of 6-series aluminum alloys as well as other aluminum alloy structural components. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of an embodiment of the present invention;

[0027] Figure 2 The image shows the morphology and particle size distribution of Al-Mg-Ta powder according to an embodiment of the present invention.

[0028] Figure 3 The diagram shows the principle of laser additive repair and the SEM cross-sectional view of the Al-Mg-Ta powder repair sample according to an embodiment of the present invention.

[0029] Figure 4 These are SEM and TEM images of the repaired area of ​​the Al-Mg-Ta powder-repaired sample according to an embodiment of the present invention.

[0030] Figure 5 This is an EBSD image of the repaired area of ​​the Al-Mg-Ta powder repair sample according to an embodiment of the present invention;

[0031] Figure 6 This is a TEM image of the repaired area of ​​the Al-Mg-Ta powder repair sample according to an embodiment of the present invention;

[0032] Figure 7 The image shows the microhardness distribution and stress-strain curve of the Al-Mg-Ta powder repair sample according to an embodiment of the present invention. Detailed Implementation

[0033] The present invention will be further explained and described below with reference to the accompanying drawings and embodiments.

[0034] Reference Figure 1 The present invention provides a laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder, comprising the following steps:

[0035] S1. Al-Mg-Ta powder was prepared using a pre-alloyed powder preparation method. The method was as follows: Each elemental metal was weighed according to the following proportions: Mg 0.8–1.8%, Ta 1.0–3.0%, Si 0.4–1.2%, Cu 0.1–0.6%, Fe 0.1–0.5%, with the remainder being Al. Specifically, the following proportions were selected: (Mg 1.16%, Ta 2.06%, Si 0.72%, Cu 0.33%, Fe 0.25%, remainder Al), (Mg 1.0%, Ta 1.5%, Si 0.6%, Cu 0.1%, Fe 0.1%, remainder Al), and (Mg 1.4%, Ta 2.5%, Si 0.9%, Cu 0.6%, Fe 0.5%, remainder Al). The resulting mixture was then added to a vacuum melting furnace for melting. Argon gas was used as a protective atmosphere to atomize the molten alloy into powder, resulting in Al-Mg-Ta powder with a particle size distribution of 53–105 μm.

[0036] S2. The prepared Al–Mg–Ta powder is sieved and then vacuum dried. The Al–Mg–Ta powder in S2 is obtained with a particle size distribution of 60–85 μm after sieving. The drying conditions of Al–Mg–Ta powder in S2 are: vacuum drying temperature of 120℃ and drying time of 2 hours.

[0037] S3. Before repair, the damaged area of ​​the aluminum alloy substrate is polished. The treatment of S3 is as follows: the substrate surface is polished with sandpaper to remove processing marks and surface oxide layer, and then anhydrous ethanol is used for cleaning to remove surface oxide film and contaminants.

[0038] S4. Laser-guided energy deposition (LAD) technology is used to repair the aluminum alloy substrate. During the laser additive manufacturing process, a diffusely distributed Al3Ta phase is generated in situ through reaction. The process parameters for S4 are: laser power of 1000W; scanning speed of 420mm / min; laser spot diameter of 2mm; powder feed rate of 15g / min; layer thickness of 0.5mm; overlap ratio of 50%; powder feed gas flow rate of 5L / min; and argon as the protective gas.

[0039] S5. The damaged area of ​​the aluminum alloy matrix is ​​subjected to aging heat treatment. After heat treatment, fine and dispersed strengthening phase β is precipitated in the Al-Mg-Ta alloy. The specific process parameters of S5 are: heat treatment at 160°C for 30 hours, followed by air cooling to room temperature.

[0040] After S5, the phase composition of the samples was analyzed using an Empyrean X-ray diffractometer (XRD). The microstructure of the samples was characterized using a Lecia DMi8 A inverted metallurgical microscope, a Zeiss-SUPRA 55 scanning electron microscope (SEM) and its equipped electron backscattered diffraction (EBSD) system. The mechanical properties of the samples were tested using an MTS E43.104 universal testing machine (tensile rate 0.5 mm / min) and an FM-100 microhardness tester (100 g load for 15 s). Both tensile and hardness tests were repeated three times to ensure the reliability of the results.

[0041] The results show that the repaired part has good metallurgical bonding and can be clearly divided into two regions: the repair zone (RZ) and the substrate zone (SZ). The heat-affected zone (HAZ) is defect-free. Figure 3 (d)), the repaired area consists of fine equiaxed crystals ( Figure 5 (a)). Figure 4 (b) Numerous diffusely distributed nanoscale precipitates with a characteristic size of approximately 5 nm were observed. To further determine its phase structure, high-resolution transmission electron microscopy (TEM) analysis was performed, such as... Figure 4As shown in (c), the analysis results show that these nanoscale precipitates exhibit an overall disordered structure, containing typical "eye-like" β″ subunits. Figure 6 Al3Ta particles with a size of about 1µm were shown. In the high-resolution transmission electron microscopy image of the Al / Al3Ta interface observed along the

[111] Al3Ta zone axis, the interplanar spacing of Al3Ta was measured to be 0.297nm. Figure 7 The mechanical properties of the repaired part were shown. The average hardness of the repaired area was 126±2HV, and the width of the heat-affected zone was approximately 200µm. The part exhibited typical softening characteristics, with the most significant decrease in hardness in the central area, reaching approximately 30%. The yield strength of the repaired part was 252±9MPa, the tensile strength was 330±12MPa, and the elongation was 5.0±0.2%.

[0042] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A laser additive repair method for aluminum alloys based on Al-Mg-Ta composite powder, characterized in that, Includes the following steps: S1. Al-Mg-Ta powder was prepared using a pre-alloyed powder preparation method; S2. The prepared Al–Mg–Ta powder is sieved and then vacuum dried; S3. Grind the damaged area of ​​the aluminum alloy substrate before repair; S4. Repairing damaged areas of the aluminum alloy substrate using laser-directed energy deposition technology; S5. Perform aging heat treatment on the damaged areas of the aluminum alloy substrate.

2. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, The S1 method involves weighing and mixing the following elemental raw materials by mass percentage: Mg 0.8%–1.8%, Ta 1.0%–3.0%, Si 0.4%–1.2%, Cu 0.1%–0.6%, Fe 0.1%–0.5%, with the balance being metallic Al. The mixture is then added to a vacuum melting furnace for melting. Argon gas is used as a protective atmosphere to atomize the molten alloy into powder, resulting in Al–Mg–Ta powder with a particle size distribution of 53–105 μm.

3. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, The drying conditions for Al–Mg–Ta powder in S2 are: vacuum drying temperature of 120℃ and drying time of 2 hours.

4. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, After sieving, Al–Mg–Ta powder in S2 was obtained with a particle size distribution of 60–85 μm.

5. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, The S3 process involves: sanding the substrate surface with sandpaper to remove processing marks and surface oxide layer, and then cleaning with anhydrous ethanol to remove surface oxide film and contaminants.

6. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, During S4 laser additive manufacturing, an aluminum alloy matrix undergoes an in-situ reaction to generate a diffusely distributed Al3Ta phase.

7. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, The process parameters for S4 are as follows: laser power is 1000W, scanning speed is 420mm / min, laser spot diameter is 2mm, powder feeding rate is 15g / min, layer thickness is 0.5mm, overlap rate is 50%, powder feeding gas flow rate is 5L / min, and protective gas is argon.

8. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, After heat treatment with S5, fine, dispersed strengthening phase β precipitates in the Al-Mg-Ta alloy.

9. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, The specific process parameters for S5 are: heat preservation at 160°C for 30 hours, followed by air cooling to room temperature.

10. The method for laser additive repair of aluminum alloys based on Al-Mg-Ta composite powder according to claim 1, characterized in that, After S5, the phase composition of the samples was analyzed using an Empyrean X-ray diffractometer (XRD). The microstructure of the samples was characterized using a Lecia DMi8 A inverted metallurgical microscope, a Zeiss-SUPRA 55 scanning electron microscope (SEM) and its equipped electron backscattered diffraction (EBSD) system. The mechanical properties of the samples were tested using an MTS E43.104 universal testing machine (tensile rate 0.5 mm / min) and an FM-100 microhardness tester (100 g load for 15 s). Both tensile and hardness tests were repeated three times to ensure the reliability of the results.

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