Electric arc additive manufacturing Al-Mg-Si alloy process and post-treatment performance strengthening method

Abstract

The invention provides an electric arc additive manufacturing Al-Mg-Si alloy process and a post-treatment performance strengthening method, and belongs to the technical field of metal material additive manufacturing. According to the method, firstly, an Al-Mg-Si alloy component is deposited layer by layer through an electric arc additive manufacturing technology, and a nearly-formed part with a rapid solidification structure is obtained; then heat treatment is conducted on the sedimentary-state component, specifically, annealing treatment is conducted firstly, and residual stress generated in the material adding process is eliminated; then solution treatment is conducted, so that a coarse second phase and a non-equilibrium eutectic structure formed in the additive manufacturing process are fully dissolved, and a supersaturated solid solution is obtained; and then artificial aging treatment is carried out, and uniform and dispersed precipitation of a strengthening phase in an aluminum matrix is promoted. By means of the method, the problems that due to the fact that the electric arc additive manufacturing Al-Mg-Si alloy is high in solidification cooling rate and complex in thermal cycle, the structure is uneven, and the mechanical property is insufficient are effectively solved, the transverse tensile strength of the Al-Mg-Si alloy is improved by 41%, the microhardness of the Al-Mg-Si alloy is improved by 77%, and precise regulation and control over the microstructure of the additive manufacturing Al-Mg-Si alloy are achieved, and the mechanical property of the Al-Mg-Si alloy is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of additive manufacturing technology for metallic materials, specifically to a method for synergistic control of the microstructure and mechanical properties of Al-Mg-Si alloy components manufactured by cold metal transfer (CMT) arc additive manufacturing. Background Technology

[0002] Aluminum alloys, due to their excellent specific strength and corrosion resistance, play a crucial role in aerospace, transportation, and other fields. The Al-Mg-Si series, belonging to the 6-series aluminum alloys, is a heat-treatable aluminum alloy with magnesium and silicon as its main alloying elements. It boasts excellent weldability and formability, and is commonly used in the manufacture of aircraft parts, ship fittings, and various hardware components. With the development of industries such as aerospace, automotive, and shipbuilding, there are higher requirements for the performance and production speed of aluminum alloy parts. However, traditional processes can no longer meet the current development concepts of low-carbon, environmentally friendly, and efficient production. Therefore, applying additive manufacturing technology to the manufacture of aluminum alloy parts can significantly shorten the manufacturing cycle and greatly increase production speed while ensuring part performance and adhering to energy-saving and environmental protection principles, thus better meeting the development needs of the industry.

[0003] For aluminum alloys, strength, plasticity, and microhardness are crucial mechanical properties; however, these properties often exhibit a restrictive relationship. Therefore, improving the strength and hardness of aluminum alloy arc additive manufacturing components while maintaining their plasticity is a key focus of research in this field. The large local thermal gradients during additive manufacturing introduce macroscopic residual stresses reaching up to the material's yield strength, severely threatening the dimensional accuracy, deformation resistance, and fatigue life of the components. The complex thermal cycling process of layer-by-layer deposition induces severe microstructural inhomogeneities within the material, manifested as coarse grains and microscopic segregation of alloying elements. This not only directly leads to anisotropic mechanical properties in the components but also results in overall performance, such as strength and toughness, that is often difficult to match with traditional forgings. Furthermore, the process easily introduces internal defects such as porosity and lack of fusion, accumulating significant residual stresses. The former becomes the source of fatigue crack initiation and corrosion propagation, while the latter significantly increases the risk of component deformation and cracking.

[0004] The main technical solution adopted in this invention is to manufacture Al-Mg-Si alloys using CMT (Selective Catalytic Modulation) arc additive manufacturing process and then perform heat treatment on them. By introducing an annealing step before solution treatment, the brittle eutectic phases continuously distributed at the grain boundaries are pre-spheroidized and coarsened, making them easier to dissolve in the subsequent solution process, thus solving the problem of insufficient control over the microstructure in traditional processes. Compared with the method of relying solely on hot isostatic pressing for post-treatment, this heat treatment scheme, while eliminating internal defects, focuses more on comprehensively controlling strength and plasticity through precipitation strengthening and grain boundary optimization, achieving a better match between the two. In addition, compared with laser selective melting technology, CMT combined with this heat treatment scheme is more suitable for low-cost and high-efficiency manufacturing of large components while maintaining similar strength levels.

[0005] The electric arc additive manufacturing process and subsequent synergistic heat treatment system established in this invention have a wide process window, strong parameter controllability, and high process stability. They provide a complete technical solution for additive manufacturing Al-Mg-Si alloy components with uniform structure, excellent performance, and low residual stress. This has important practical value and broad prospects for promoting the engineering application of this technology in large load-bearing structures such as aerospace and rail transportation, which require high performance and high consistency. Summary of the Invention

[0006] The purpose of this invention is to provide an arc additive manufacturing process for Al-Mg-Si alloys and a method for post-treatment to enhance their properties. This invention overcomes the technical bottlenecks commonly found in existing CMT arc additive manufacturing of Al-Mg-Si alloy components, such as inhomogeneous microstructure, significant anisotropy of mechanical properties, and difficulty in synergistically improving overall performance. By combining the arc additive manufacturing process of Al-Mg-Si alloy welding wire with a post-heat treatment regime, this invention provides a composite manufacturing method that can effectively control the microstructure of components, simultaneously improve strength and plasticity, and ensure performance stability. This method first forms the component using a CMT process, followed by a composite heat treatment process including annealing, solution treatment, and multi-stage aging, ultimately obtaining a high-performance aluminum alloy component with a uniform microstructure, high dislocation density, and nanoscale strengthening phases.

[0007] To achieve the above objectives, the present invention provides the following solution: This invention provides a process for arc additive manufacturing of Al-Mg-Si alloys and a method for post-treatment to enhance their properties. The method is characterized by using an arc additive manufacturing process to produce the Al-Mg-Si alloy, followed by annealing, solution treatment, and aging to regulate its microstructure and properties. The process includes the following steps: Step 1: Start the CMT additive manufacturing system; after pre-soldering grinding and preheating of the 6061 experimental substrate, use a fixture to fix the experimental substrate on the platform; Step 2: Aluminum alloy is deposited layer by layer on the substrate using Al-Mg-Si alloy welding wire in a cyclic manner to form an additive component; the CMT arc additive manufacturing process parameters are adjusted, and the above additive manufacturing process is repeated. 99.99% high-purity Ar is used as the protective gas in the additive manufacturing process. Step 3: The Al-Mg-Si alloy component obtained by additive manufacturing is subjected to heat treatment, which includes annealing, solution treatment and artificial aging treatment in sequence.

[0008] Preferably, the additive manufacturing system consists of a welding machine, a protective gas cylinder, a CNC computer port, an experimental platform, and a main power supply.

[0009] Preferably, the Al-Mg-Si alloy welding wire has a diameter of 1.2 mm and its main chemical composition is: Cu-0.01wt%, Si-0.85wt%, Mn-0.003wt%, Mg-0.62wt%, Zn-0.003wt%, Cr-0.005wt%, Fe-0.23wt%, Al-Bal.wt%.

[0010] Preferably, the arc additive manufacturing process parameters are: welding current 95 A ~ 135 A, welding speed 300 mm / min ~ 500 mm / min, gas flow rate 10 L / min ~ 20 L / min, and interlayer dwell time 3 min ~ 7 min.

[0011] Preferably, the welding wire extension during the additive manufacturing process is 10 mm, the CNC terminal controls the welding torch travel path in a reciprocating manner, and the welding torch is raised by about 3 mm after each layer is deposited.

[0012] Preferably, the annealing temperature is 150℃~270℃, held for 1 h~2 h, and then furnace cooled to room temperature.

[0013] Preferably, the solution treatment temperature is 450℃~570℃, the holding time is 1 h, and the product is cooled to room temperature by water after removal from the furnace.

[0014] Preferably, the aging temperature is 120℃~200℃, the holding time is 4 h~12 h, and the furnace is cooled to room temperature.

[0015] Preferably, the Al-Mg-Si alloy component with excellent comprehensive mechanical properties is manufactured by arc additive manufacturing and post-processing.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a comprehensive process combining arc additive manufacturing and subsequent specific heat treatment for forming Al-Mg-Si alloy components. Through the synergistic control of the two processes, this method achieves a transverse tensile strength of 248.45 MPa and a longitudinal tensile strength of 226.49 MPa, representing increases of 41% and 42% respectively, while maintaining the component's plasticity. The microhardness is 78.94 HV, an improvement of 77%. After heat treatment, a fine and uniform microstructure is obtained, achieving a synergistic improvement in strength, toughness, and performance stability, comprehensively improving the component's service capability and reliability. This method effectively improves the overall mechanical property matching of the component, thus providing a key guarantee for its reliability and long-term safety during service.

[0017] This invention provides a complete process solution from additive manufacturing to subsequent heat treatment. The process parameters are clear and controllable, with good repeatability, providing a reliable technical guarantee for the industrial production of large Al-Mg-Si alloy components using additive manufacturing. The process route is reasonable, and the equipment requirements are moderate. While ensuring the performance of the components, it also takes into account production costs and efficiency, and has good technical and economic benefits and industrialization promotion value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the additive manufacturing process in an arc additive manufacturing process for Al-Mg-Si alloys and a post-treatment method for strengthening its properties, provided by this invention; Figure 2 A schematic diagram of the tensile specimen dimensions in an arc additive manufacturing process for Al-Mg-Si alloys and a post-treatment method for strengthening properties provided by the present invention. Figure 3 This invention provides a heat treatment scheme diagram for an electric arc additive manufacturing process of Al-Mg-Si alloys and a post-treatment method for strengthening its properties. Figure 4 The inverse pole figures of typical samples in the process of electric arc additive manufacturing of Al-Mg-Si alloy and the method of post-treatment to strengthen its properties provided by the present invention are shown in the figure. (a) and (b) are the equiaxed crystal region and columnar crystal region of the alloy before heat treatment, and (c) and (d) are the equiaxed crystal region and columnar crystal region of the alloy after heat treatment. Figure 5Comparison of stress-strain curves of tensile specimens before and after heat treatment in the electric arc additive manufacturing process of Al-Mg-Si alloy and the method for post-treatment to enhance its properties provided by the present invention. Figure 6 The image shows a comparison of microhardness before and after heat treatment in the process of electric arc additive manufacturing of Al-Mg-Si alloy and the method of post-treatment to enhance its properties, which is provided by the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 are within the scope of protection of the present invention.

[0021] The purpose of this invention is to provide an arc additive manufacturing process for Al-Mg-Si alloys and a method for post-treatment to enhance their properties. This invention overcomes the technical bottlenecks commonly found in existing CMT arc additive manufacturing of Al-Mg-Si alloy components, such as inhomogeneous microstructure, significant anisotropy of mechanical properties, and difficulty in synergistically improving overall performance. By combining Al-Mg-Si alloy wire with a post-heat treatment process, this invention provides a composite manufacturing method that can effectively control the microstructure of the component, simultaneously improve strength and plasticity, and ensure performance stability. The method first forms the component using a CMT process, followed by a composite heat treatment process including annealing, solution treatment, and multi-stage aging, ultimately obtaining a high-performance aluminum alloy component with a uniform microstructure, high dislocation density, and nanoscale strengthening phases.

[0022] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. Example 1

[0023] This embodiment provides a process for arc additive manufacturing of Al-Mg-Si alloys and a method for post-treatment to enhance their properties, including the following steps: Step 1: Start the CMT additive manufacturing system. The system consists of a welding machine, protective gas cylinder, CNC computer port, experimental platform, and main power supply. A CMT-TPS3200 welding machine manufactured by Fronius can be used. Connect the CMT welding torch to the computer and use CNC software to output digital pulse signals to control the stepper motor or servo motor of the experimental platform, thereby achieving path control of the CMT additive manufacturing process. Step 2: Mechanically grind and preheat the 10 mm thick 6061 experimental substrate to be soldered to ensure that the CMT additive manufacturing environment is free from pollution. At the same time, use a fixture to fix the experimental substrate on the welding platform to prevent the substrate from bending and deforming due to local heating. Then perform simulated welding to adjust the initial starting point of welding and ensure the feasibility of welding. Use 99.99% high-purity Ar as the shielding gas. Step 3: Using Al-Mg-Si alloy welding wire with a diameter of 1.2 mm (its chemical composition is: Cu-0.01wt%, Si-0.85wt%, Mn-0.003wt%, Mg-0.62wt%, Zn-0.003wt%, Cr-0.005wt%, Fe-0.23wt%, Al-Bal.wt%), a single-pass multilayer experiment of Al-Mg-Si based alloy was carried out on a 6061 substrate. The welding current was set to 115 A, the welding speed to 400 mm / min, the gas flow rate to 15 L / min, and the interlayer dwell time to 5 min. After repeated layer-by-layer deposition of aluminum alloy, an Al-Mg-Si alloy additive component was obtained. Step 4: Anneal the additively manufactured Al-Mg-Si alloy component at a temperature of 210℃ for 2 hours, followed by furnace cooling to room temperature. Step 5: Perform solution treatment on the Al-Mg-Si alloy components after annealing at a temperature of 510℃ for 1 hour, and then quickly water-cool them to room temperature after removing them from the furnace. Step Six: The Al-Mg-Si alloy components, after annealing and solution treatment, undergo aging treatment at 160℃ for 8 hours, followed by furnace cooling to room temperature. The heat treatment process is as follows: Figure 2 As shown; Step 7: Design a tensile specimen according to GB / T 228.1-2021 "Metallic materials, tensile testing—Part 1: Test at room temperature," with dimensions as follows. Figure 3 As shown. The additive part was cut using wire EDM, and its tensile properties were tested and recorded using an electronic universal testing machine, with the transverse tensile strength as the standard. Step 8: Cut the component into 10 mm × 10 mm × 6 mm specimens using wire EDM. Before starting the hardness test, heat-mount the hardness specimens, clean them with sandpaper, and then polish them to obtain a smooth surface. Perform the hardness test using a digital Vickers hardness tester, measuring 20 points. Then, use software to plot the hardness curve, analyze the hardness change trend, and take the average value as the final microhardness data, which is then recorded. Example 2

[0024] Step 1: Maintain the same process as Steps 1-3 of Example 1, and keep all additive manufacturing process parameters such as welding speed, welding current, gas flow rate, and interpass dwell time unchanged, and complete the manufacturing of the component under the same conditions; Step 2: Anneal the additively manufactured Al-Mg-Si alloy component at a temperature of 210℃ for 2 hours, followed by furnace cooling to room temperature. Step 3: Perform solution treatment on the Al-Mg-Si alloy components after annealing at a temperature of 510℃ for 1 hour, and then quickly water-cool them to room temperature after removing them from the furnace. Step 4: After annealing and solution treatment, the Al-Mg-Si alloy components are subjected to aging treatment at 160℃ for 10 hours, and then cooled to room temperature in the furnace. Step 5: Maintain the same tensile specimen standard as in Step 7 of Example 1, cut the additive part using wire cutting, and test the tensile properties and record the data using an electronic universal testing machine with the transverse tensile strength as the standard. Step Six: Using the same hardness sample standard as in Step Eight of Example 1, conduct a hardness test using a digital Vickers hardness tester with 20 measurement points. Then, use software to plot the hardness curve, analyze the hardness change trend, and take the average value as the final microhardness data and record it. Example 3

[0025] Step 1: Maintain the same process as Steps 1-3 of Example 1, and keep all additive manufacturing process parameters such as welding speed, welding current, gas flow rate, and interpass dwell time unchanged, and complete the manufacturing of the component under the same conditions; Step 2: Anneal the Al-Mg-Si alloy components manufactured by arc additive manufacturing at a temperature of 210℃ for 2 hours, followed by furnace cooling to room temperature. Step 3: Perform solution treatment on the Al-Mg-Si alloy components after annealing at a temperature of 510℃ for 1 hour, and then quickly water-cool them to room temperature after removing them from the furnace. Step 4: After annealing and solution treatment, the Al-Mg-Si alloy components are subjected to aging treatment at 160℃ for 12 hours, and then cooled to room temperature in the furnace. Step 5: Maintain the same tensile specimen standard as in Step 7 of Example 1, cut the additive part using wire cutting, and test the tensile properties and record the data using an electronic universal testing machine with the transverse tensile strength as the standard. Step Six: Using the same hardness sample standard as in Step Eight of Example 1, conduct a hardness test using a digital Vickers hardness tester with 20 measurement points. Then, use software to plot the hardness curve, analyze the hardness change trend, and take the average value as the final microhardness data and record it.

[0026] Comparative Example 1 Step 1: Maintain the same process as Steps 1-3 of Example 1, and keep all additive manufacturing process parameters such as welding speed, welding current, gas flow rate, and interpass dwell time unchanged, and complete the manufacturing of the component under the same conditions; Step 2: The aluminum alloy component obtained in Step 1 is processed according to the tensile test specimen standard in Step 7 of Example 1. The tensile properties of the additive part are tested using an electronic universal testing machine, and the tensile strength is recorded. The aluminum alloy component obtained in Step 1 is processed according to the hardness test specimen standard in Step 8 of Example 1. A digital Vickers hardness tester is used to perform a hardness test, with 20 measurement points. The hardness curve is plotted using software, and the average value is taken as the final microhardness data and recorded. At this time, the transverse tensile strength is 178.05 MPa, and the microhardness is 44.72 HV. Step 3: Compare the tensile properties and microhardness test data from Step 2 with the tensile properties and microhardness data measured in Example 1. The results show that the transverse tensile strength increased by 29% from 178.05 MPa to 229.64 MPa after aging at 160℃ and holding for 8 hours. The microhardness increased by 73.4% from 44.72 HV to 77.56 HV after aging at 160℃ and holding for 8 hours. Step 4: Compare the tensile properties and microhardness test data from Step 2 with the tensile properties and microhardness data measured in Example 1. The results show that the tensile strength significantly increased from 178.05 MPa after welding to 248.45 MPa after aging at 160℃ and holding for 10 h, an increase of 41%. The microhardness increased from 44.72 HV to 78.94 HV after aging at 160℃ and holding for 10 h, an increase of 76.5%. Step 5: Compare the tensile properties and microhardness test data from Step 2 with the tensile properties and microhardness data measured in Example 1. The results show that the tensile strength increased by 33% from 178.05 MPa after welding to 236.68 MPa after aging at 160℃ and holding for 12 h. The microhardness increased by 77.7% from 44.72 HV to 79.49 HV after aging at 160℃ and holding for 8 h.

[0027] Combination Figure 4 The inverse pole figure shows that after heat treatment, the grains in the equiaxed and columnar grain regions are significantly smaller, and the grain size difference is not significant. The fine and uniform microstructure, through the synergistic effect of fine grain strengthening and dispersion strengthening, greatly improves the strength of the component, avoids local stress concentration caused by compositional segregation or coarse grains, reduces the risk of crack initiation and propagation, and thus improves the toughness and plasticity of the component while increasing its strength. Figure 5 Stress-strain curves and Figure 6 The microhardness comparison charts confirm that the heat treatment process provided by this invention significantly, clearly, and reproducibly improves the mechanical properties of Al-Mg-Si alloy components manufactured by arc additive manufacturing. Experimental data clearly verify that, under the same additive manufacturing process parameters, simply implementing the aging heat treatment regime designed in this invention can increase the transverse tensile strength of the components by 29% to 41% and improve the microhardness by 77%. Furthermore, after heat treatment, the coarse microstructure is transformed into a uniform and fine microstructure. This result fully demonstrates that subsequent heat treatment is a key process step in fully releasing the performance potential of additively manufactured Al-Mg-Si alloys and overcoming their insufficient strength in the deposited state.

[0028] This invention has described the principles and implementation methods of the invention using preferred embodiments. The descriptions of these embodiments are merely for the purpose of helping to understand the method and core ideas of the invention; furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of the invention.

Claims

1. An electric arc additive manufacturing process for Al-Mg-Si alloys and a post-treatment method for strengthening their properties, characterized in that... An Al-Mg-Si alloy was manufactured using an electric arc additive manufacturing process, followed by annealing, solution treatment, and aging to regulate its microstructure and properties. The process includes the following steps: Step 1: Start the CMT additive manufacturing system; after pre-soldering grinding and preheating of the 6061 experimental substrate, use a fixture to fix the experimental substrate on the platform; Step 2: Aluminum alloy is deposited layer by layer on the substrate using Al-Mg-Si alloy welding wire in a cyclic manner to form an additive component; the CMT arc additive manufacturing process parameters are adjusted, and the above additive manufacturing process is repeated; 99.99% high-purity Ar is used as the shielding gas in the additive manufacturing process. Step 3: The Al-Mg-Si alloy component obtained by additive manufacturing is subjected to heat treatment. The heat treatment process includes annealing, solution treatment and artificial aging treatment in sequence. The Al-Mg-Si alloy welding wire has a diameter of 1.2 mm and its main chemical composition is: Cu-0.01wt%, Si-0.85wt%, Mn-0.003wt%, Mg-0.62wt%, Zn-0.003wt%, Cr-0.005wt%, Fe-0.23wt%, Al-Bal.wt%; The additive manufacturing process parameters are: welding current 95 A ~ 135 A, welding speed 300 mm / min ~ 500 mm / min, gas flow rate 10 L / min ~ 20 L / min, and interlayer dwell time 3 min ~ 7 min; The annealing process includes: heating the Al-Mg-Si alloy component to 150℃~270℃, holding it at that temperature for 1 h~2 h, and then furnace cooling it to room temperature; The solution treatment temperature is 450℃~570℃, the holding time is 1 hour, and after being taken out of the furnace, it is quickly water-cooled to room temperature; The artificial aging treatment temperature is 120℃~200℃, the holding time is 4 h~12 h, and it is cooled to room temperature with the furnace.

2. The method for arc additive manufacturing of Al-Mg-Si alloys and post-treatment to enhance its properties according to claim 1, characterized in that: The additive manufacturing system consists of a welding machine, a protective gas cylinder, a CNC computer port, an experimental platform, and a main power supply.

3. The method for arc additive manufacturing of Al-Mg-Si alloys and post-treatment for strengthening properties according to claim 1, characterized in that: In the additive manufacturing process, the wire extension is 10 mm, the CNC terminal controls the welding gun to travel in a reciprocating manner, and the welding gun is raised by about 3 mm after each layer is deposited.

4. The method for arc additive manufacturing of Al-Mg-Si alloys and post-treatment for strengthening properties according to claim 1, characterized in that, The Al-Mg-Si alloy component is manufactured by the method described in claims 1-3. The obtained Al-Mg-Si alloy component has a 41% increase in transverse tensile strength and a 77% increase in microhardness. It has a fine and uniform microstructure and excellent comprehensive mechanical properties.

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