Preparation method for improving strength of AZ80 magnesium alloy manufactured through electric arc additive

Abstract

The invention discloses a preparation method for improving the strength of an AZ80 magnesium alloy manufactured through electric arc additive manufacturing. The method comprises the steps that firstly, a magnesium alloy substrate is installed in additive manufacturing equipment for preheating treatment; secondly, an AZ80 magnesium alloy welding wire is loaded, the distance between the AZ80 magnesium alloy welding wire and a welding gun head is adjusted, and an argon protection system is started synchronously; 3, setting process parameters; fourthly, electric arc additive manufacturing is completed through fused deposition forming of an AZ80 magnesium alloy welding wire, and an AZ80 magnesium alloy component is obtained; fifthly, the AZ80 magnesium alloy component is subjected to high-temperature short-time solution treatment and rapidly cooled to the room temperature; and sixthly, aging treatment is conducted on the AZ80 magnesium alloy component subjected to solution treatment. According to the method, twin crystals and a fine dispersed second phase are introduced into an AZ80 magnesium alloy matrix by adopting a graded heat treatment process, so that the magnesium alloy has relatively high strength, the process period is relatively short, the energy consumption is relatively low, and the method is suitable for the field of electric arc additive manufacturing of magnesium alloys.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal additive manufacturing, and particularly relates to a preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing. Background Art

[0002] As a lightweight structural material with great potential in the 21st century, magnesium alloy has attracted much attention in the field of lightweighting of high-end equipment such as aerospace and rail transit due to its low density (1.74 g / cm³, only 1 / 4 of that of steel) and excellent comprehensive properties. However, traditional casting and powder metallurgy processes have problems such as uneven microstructure, high porosity, poor formability of complex components, and low material utilization rate (less than 30%), which seriously restrict their applications. In recent years, cold metal transfer arc additive manufacturing (CMT-WAAM) technology, due to its low heat input and high forming efficiency, provides a new solution for the preparation of complex magnesium alloy components. Among many magnesium alloys, AZ80 magnesium alloy has relatively high strength and good plastic processing ability, and is a relatively mature commercial magnesium alloy. However, the AZ80 magnesium alloy prepared by CMT-WAAM technology faces problems such as uneven tissue distribution and low strength, resulting in its inability to meet the requirements of equipment manufacturing applications. Therefore, there is an urgent need for a preparation method to improve the strength of AZ80 magnesium alloy by arc additive manufacturing, which is crucial for enhancing the performance of additive manufactured magnesium alloys. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing in view of the above-mentioned deficiencies of the prior art. This method introduces twins and finely dispersed second phases into the AZ80 magnesium alloy matrix by adopting a hierarchical heat treatment process, and improves the strength of the AZ80 magnesium alloy by arc additive manufacturing on the premise of ensuring the uniformity of the microstructure, thus solving the problem of low strength of the AZ80 magnesium alloy by arc additive manufacturing.

[0004] To solve the above technical problem, the technical solution adopted by the present invention is: a preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing, characterized in that the method comprises the following steps: Step 1. Pretreatment: Install the magnesium alloy substrate that has been removed of oxide scale and is clean in the additive manufacturing equipment, take the upper surface of the magnesium alloy substrate as the processing reference plane, then adjust the vertical distance between the welding torch tip and the magnesium alloy substrate, and perform preheating treatment on the magnesium alloy substrate by using a heating device; Step 2. Adjust the equipment posture: Load the AZ80 magnesium alloy wire into the wire feeding system, and the end penetrates into the wire guiding tube of the welding torch to ensure smooth wire feeding. Adjust the position of the welding torch so that the welding torch tip keeps a distance from the end of the AZ80 magnesium alloy wire, and the welding torch tip is perpendicular to the surface of the magnesium alloy substrate. Synchronously turn on the argon protection system and control the argon flow rate; Step 3. Set process parameters: Adjusting the process parameters includes wire feeding speed, welding speed, arc voltage, weld width and weld height of the molten pool; Step 4. Arc additive manufacturing: Activate the wire feeding system and establish an arc heat source system, drive the welding torch to perform the deposition forming of AZ80 magnesium alloy wire along the preset digital path. After completing the first layer of metal deposition on the surface of the magnesium alloy substrate preheated in Step 1, continuously implement the sequential deposition process. Through the path-layer thickness coupling control strategy, realize the three-dimensional entity stacked layer by layer according to the digital model, complete the arc additive manufacturing, and obtain a near-net-shaped AZ80 magnesium alloy component; Step 5. Solution treatment: Perform high-temperature short-time solution treatment on the AZ80 magnesium alloy component obtained in Step 4, and quickly cool it to room temperature to reduce the content of large second phases and homogenize the microstructure; Step 6. Aging treatment: Perform aging treatment on the AZ80 magnesium alloy component after solution treatment in Step 4 to generate twins and fine, dispersed and uniform second phases in the matrix.

[0005] The present invention performs hierarchical heat treatment on the AZ80 magnesium alloy component manufactured by arc additive manufacturing, including two-stage coordination of high-temperature short-time solution treatment and short-time aging treatment. By precisely controlling the temperature field and time parameters of the solution treatment, effectively dissolve the coarse second-phase particles, eliminate the grain boundary segregation phenomenon existing in the original deposition state, and at the same time promote the uniform redistribution of the β-Mg 17 Al 12 phase, significantly improve the microstructure uniformity, and retain an appropriate amount of residual thermal stress in the matrix through the rapid cooling process to provide a driving force for subsequent twin nucleation. Then, in the aging treatment stage, dual regulation is realized through the thermal activation mechanism: first, release the lattice distortion energy remaining in the solution stage, reduce the dislocation density, and synchronously induce twin nucleation; second, trigger the precipitation of fine β-Mg 17 Al 12 strengthening phase. This twin-precipitation composite strengthening mechanism greatly improves the yield and tensile strength of the material.

[0006] Generally, arc additive manufacturing realizes the forming of workpieces by melting the wire and stacking the metal layer by layer. In the present invention, first, obtain the preset digital path by slicing and analyzing and scanning the target product alloy, and then according to the preset digital path, heat the metal wire by the welding torch to melt and deposit it on the substrate. After completing the first layer of metal deposition, that is, the single-layer solid sheet deposition, continue with the sequential deposition process, that is, the layer-by-layer metal wire melting-deposition process. By combining the control of each layer path and each layer thickness, make each single-layer solid sheet stack layer by layer to form a three-dimensional entity, and then obtain the alloy component.

[0007] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the vertical distance between the welding torch tip and the magnesium alloy substrate in step one is 3 mm to 8 mm.

[0008] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the temperature of the preheating treatment in step one is 100°C to 180°C.

[0009] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the distance between the welding torch tip and the end of the AZ80 magnesium alloy welding wire in step two is 5 mm to 10 mm.

[0010] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the argon flow rate in step two is 18 L / min to 25 L / min.

[0011] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the wire feeding speed in step three is 5000 mm / min to 9000 mm / min, the welding speed is 450 mm / min to 750 mm / min, the arc voltage is 8 V to 20 V, the weld width of the molten pool is 5 mm to 15 mm, and the weld height is 1.5 mm to 2.5 mm.

[0012] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the temperature of the high-temperature short-time solution treatment in step five is 470°C to 490°C, and the time is 1 h to 2 h.

[0013] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the rapid cooling rate in step five is 25°C / s to 50°C / s.

[0014] The above-mentioned preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing is characterized in that the temperature of the aging treatment in step six is 160°C to 180°C, and the time is 24 h to 32 h.

[0015] The present invention has the following advantages compared with the prior art: 1. By adopting a step-by-step heat treatment process including high-temperature short-time solution treatment and short-time aging treatment, the present invention reduces the content of large second phases and homogenizes the structure in the magnesium alloy matrix formed by arc additive manufacturing. At the same time, twins and fine, dispersed and uniform second phases are introduced, thereby improving the strength of the AZ80 magnesium alloy prepared by arc additive manufacturing.

[0016] 2. Compared with the traditional stepped heat treatment process, the grading heat treatment process after the arc additive manufacturing of the present invention has a shorter process cycle and lower energy consumption, and is suitable for popularization and application.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0018] Figure 1 It is the microstructure diagram of the as-deposited AZ80 magnesium alloy component obtained in Example 1 of the present invention.

[0019] Figure 2 It is the tensile mechanical property diagram of the as-deposited AZ80 magnesium alloy component obtained in Example 1 of the present invention.

[0020] Figure 3 It is the microstructure diagram of the AZ80 magnesium alloy component after solution treatment and aging treatment in Example 1 of the present invention.

[0021] Figure 4 It is the microstructure diagram of the AZ80 magnesium alloy component after solution treatment and aging treatment in Example 2 of the present invention.

[0022] Figure 5 It is the tensile mechanical property diagram of the AZ80 magnesium alloy component after solution treatment and aging treatment in Example 2 of the present invention. Detailed Description of the Invention

[0023] Example 1 This example includes the following steps: Step 1. Pretreatment: Install the cleaned AZ80 magnesium alloy substrate without oxide scale in the additive manufacturing equipment, take the upper surface of the AZ80 magnesium alloy substrate as the processing reference plane, then adjust the vertical distance between the welding torch tip and the AZ80 magnesium alloy substrate to 5 mm, and use a heating device to perform preheating treatment on the AZ80 magnesium alloy substrate, and the preheating temperature is 150 °C; Step 2. Adjust the equipment posture: Load the AZ80 magnesium alloy welding wire into the wire feeding system, and the end penetrates into the wire guiding tube of the welding torch to ensure smooth wire feeding. Adjust the position of the welding torch so that the distance between the welding torch tip and the end of the AZ80 magnesium alloy welding wire is 8 mm, and the welding torch tip is perpendicular to the surface of the AZ80 magnesium alloy substrate. Synchronously turn on the argon protection system and control the argon flow rate to 22 L / min; Step 3. Set process parameters: Adjust the process parameters including the wire feeding speed of 7500 mm / min, the welding speed of 600 mm / min, the arc voltage of 10 V, the weld width of the molten pool of 8 mm, and the weld height of 1.8 mm; Step 4. Arc additive manufacturing: Activate the wire feeding system and establish an arc heat source system, drive the welding torch to perform the deposition forming of AZ80 magnesium alloy wire along the preset digital path. After completing the first metal deposition on the surface of the AZ80 magnesium alloy substrate preheated in Step 1, continuously implement the sequential deposition process. Through the path-layer thickness coupling control strategy, realize the three-dimensional entity stacked layer by layer according to the digital model, complete the arc additive manufacturing, and obtain a near-net-shaped AZ80 magnesium alloy component, namely the as-deposited AZ80 magnesium alloy component; Step 5. Solution treatment: Perform a high-temperature short-time solution treatment on the as-deposited AZ80 magnesium alloy component obtained in Step 4, with a temperature of 490 °C and a time of 1 h, and rapidly cool it to room temperature at a rate of 45 °C / s to reduce the content of large second phases and homogenize the microstructure; Step 6. Aging treatment: Perform aging treatment on the AZ80 magnesium alloy component after solution treatment in Step 4, with a temperature of 170 °C and a time of 28 h, to generate twins and fine, dispersed and uniform second phases in the matrix.

[0024] Figure 1 This is the microstructure diagram of the as-deposited AZ80 magnesium alloy component obtained in this embodiment. From Figure 1 it can be seen that the grain morphology of the as-deposited AZ80 magnesium alloy component is mainly equiaxed grains, and a large number of second phases are distributed in the matrix.

[0025] Figure 2 This is the tensile mechanical property diagram of the as-deposited AZ80 magnesium alloy component obtained in this embodiment. From Figure 2 it can be seen that the yield strength, tensile strength and elongation of the as-deposited AZ80 magnesium alloy component are 118 MPa, 247 MPa and 12.24% respectively.

[0026] Figure 3 This is the microstructure diagram of the AZ80 magnesium alloy component after solution and aging treatments in this embodiment. From Figure 3 it can be seen that a large number of twins are contained in the matrix of the AZ80 magnesium alloy component after the step-by-step heat treatment.

[0027] Example 2 This embodiment includes the following steps: Step 1. Pretreatment: Install the cleaned AZ80 magnesium alloy substrate without oxide scale in the additive manufacturing equipment, take the upper surface of the AZ80 magnesium alloy substrate as the processing reference plane, then adjust the vertical distance between the welding torch tip and the AZ80 magnesium alloy substrate to 8 mm, and use a heating device to perform preheating treatment on the AZ80 magnesium alloy substrate, with the preheating temperature being 100 °C; Step 2. Adjust the equipment posture: Load the AZ80 magnesium alloy wire into the wire feeding system, and insert the end into the wire guiding tube of the welding torch to ensure smooth wire feeding. Adjust the position of the welding torch so that the distance between the tip of the welding torch and the end of the AZ80 magnesium alloy wire is 5 mm, and the tip of the welding torch is perpendicular to the surface of the AZ80 magnesium alloy substrate. Synchronously activate the argon protection system and control the argon flow rate to 18 L / min; Step 3. Set process parameters: Adjust the process parameters including the wire feeding speed of 5000 mm / min, the welding speed of 450 mm / min, the arc voltage of 8 V, the weld width of the molten pool of 5 mm, and the weld height of 1.5 mm; Step 4. Arc additive manufacturing: Activate the wire feeding system and establish an arc heat source system, drive the welding torch to perform the deposition forming of the AZ80 magnesium alloy wire along the preset digital path. After completing the first metal deposition on the surface of the AZ80 magnesium alloy substrate preheated in Step 1, continuously implement the layer-by-layer deposition process. Through the path-layer thickness coupling control strategy, realize the three-dimensional entity stacked layer by layer according to the digital model, complete the arc additive manufacturing, and obtain a near-net-shaped AZ80 magnesium alloy component; Step 5. Solution treatment: Perform a high-temperature short-time solution treatment on the AZ80 magnesium alloy component obtained in Step 4, with a temperature of 470 °C and a time of 2 h, and rapidly cool it to room temperature at a rate of 50 °C / s to reduce the content of large second phases and homogenize the microstructure; Step 6. Aging treatment: Perform aging treatment on the AZ80 magnesium alloy component that has undergone solution treatment in Step 4, with a temperature of 160 °C and a time of 32 h, to generate twins and fine, dispersed, and uniform second phases in the matrix.

[0028] Figure 4 is the microstructure diagram of the AZ80 magnesium alloy component after solution and aging treatments in this embodiment. From Figure 4 it can be seen that a large number of twins are contained in the matrix of the AZ80 magnesium alloy component after this step-by-step heat treatment.

[0029] Figure 5 is the tensile mechanical property diagram of the AZ80 magnesium alloy component after solution and aging treatments in this embodiment. Its yield strength and tensile strength are significantly improved compared with the as-deposited state, but the elongation is reduced.

[0030] Example 3 This embodiment includes the following steps: Step 1. Pretreatment: Install the cleaned AZ80 magnesium alloy substrate without oxide scale in the additive manufacturing equipment, take the upper surface of the AZ80 magnesium alloy substrate as the processing reference plane, then adjust the vertical distance between the tip of the welding torch and the AZ80 magnesium alloy substrate to 3 mm, and use a heating device to perform preheating treatment on the AZ80 magnesium alloy substrate, with a preheating temperature of 180 °C; Step 2. Adjust the equipment posture: Load the AZ80 magnesium alloy welding wire into the wire feeding system, and let the end pass through the wire guiding tube of the welding torch to ensure smooth wire feeding. Adjust the position of the welding torch so that the distance between the tip of the welding torch and the end of the AZ80 magnesium alloy welding wire is 10 mm, and the tip of the welding torch is perpendicular to the surface of the AZ80 magnesium alloy substrate. Synchronously activate the argon protection system and control the argon flow rate to be 25 L / min; Step 3. Set the process parameters: Adjust the process parameters including the wire feeding speed of 9000 mm / min, the welding speed of 750 mm / min, the arc voltage of 20 V, the weld width of the molten pool of 15 mm, and the weld height of 2.5 mm; Step 4. Arc additive manufacturing: Activate the wire feeding system and establish an arc heat source system, drive the welding torch to perform the deposition forming of the AZ80 magnesium alloy welding wire along the preset digital path. After completing the first-pass metal deposition on the surface of the AZ80 magnesium alloy substrate preheated in Step 1, continuously implement the layer-by-layer deposition process. Through the path-layer thickness coupling control strategy, realize the three-dimensional entity stacked layer by layer according to the digital model, complete the arc additive manufacturing, and obtain a near-net-shaped AZ80 magnesium alloy component; Step 5. Solution treatment: Perform a high-temperature short-time solution treatment on the AZ80 magnesium alloy component obtained in Step 4, with the temperature of 480 °C and the time of 1 h, and rapidly cool it to room temperature at a speed of 25 °C / s to reduce the content of large second phases and homogenize the microstructure; Step 6. Aging treatment: Perform an aging treatment on the AZ80 magnesium alloy component solution-treated in Step 4, with the temperature of 180 °C and the time of 24 h to generate twins and fine, dispersed and uniform second phases in the matrix.

[0031] As described above, it is only a preferred embodiment of the present invention and does not impose any limitation on the present invention. Any simple modification, change, and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing, characterized in that, The method includes the following steps: Step 1. Pretreatment: Install the oxide-scale-removed and clean magnesium alloy substrate in the additive manufacturing equipment, with the upper surface of the magnesium alloy substrate as the processing reference plane. Then, adjust the vertical distance between the welding torch tip and the magnesium alloy substrate, and perform preheating treatment on the magnesium alloy substrate using a heating device; Step 2. Adjust the equipment posture: Load the AZ80 magnesium alloy wire into the wire feeding system, and let the end pass through the wire guiding tube of the welding torch to ensure smooth wire feeding. Adjust the position of the welding torch so that the welding torch tip is at a distance from the end of the AZ80 magnesium alloy wire, and the welding torch tip is perpendicular to the surface of the magnesium alloy substrate. Synchronously turn on the argon protection system and control the argon flow rate; Step 3. Set process parameters: Adjust the process parameters including wire feeding speed, welding speed, arc voltage, weld width and weld height of the molten pool; Step 4. Arc additive manufacturing: Activate the wire feeding system and establish an arc heat source system, drive the welding torch to perform the deposition forming of the AZ80 magnesium alloy wire along the preset digital path. After completing the first-pass metal deposition on the surface of the magnesium alloy substrate preheated in Step 1, continuously implement the layer-by-layer deposition process. Through the path-layer thickness coupling control strategy, realize the three-dimensional entity stacked layer by layer according to the digital model, complete the arc additive manufacturing, and obtain a near-net-shaped AZ80 magnesium alloy component; Step 5. Solution treatment: Perform high-temperature short-time solution treatment on the AZ80 magnesium alloy component obtained in Step 4, and quickly cool it to room temperature to reduce the content of large second phases and homogenize the microstructure; Step 6. Aging treatment: Perform aging treatment on the AZ80 magnesium alloy component that has undergone solution treatment in Step 4 to generate twins and fine, dispersed and uniform second phases in the matrix.

2. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The vertical distance between the welding torch tip and the magnesium alloy substrate in Step 1 is 3 mm to 8 mm.

3. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The temperature of the preheating treatment in Step 1 is 100 °C to 180 °C.

4. A preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The distance between the welding torch tip and the end of the AZ80 magnesium alloy wire in Step 2 is 5 mm to 10 mm.

5. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The argon flow rate in Step 2 is 18 L / min to 25 L / min.

6. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, wherein, The wire feeding speed in Step 3 is 5000 mm / min to 9000 mm / min, the welding speed is 450 mm / min to 750 mm / min, the arc voltage is 8 V to 20 V, the weld width of the molten pool is 5 mm to 15 mm, and the weld height is 1.5 mm to 2.5 mm.

7. A preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The temperature of the high-temperature short-time solution treatment in Step 5 is 470 °C to 490 °C, and the time is 1 h to 2 h.

8. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, characterized in that, The rapid cooling speed in Step 5 is 25 °C / s to 50 °C / s.

9. The preparation method for improving the strength of AZ80 magnesium alloy by arc additive manufacturing according to claim 1, wherein, The temperature of the aging treatment in Step 6 is 160 °C to 180 °C, and the time is 24 h to 32 h.

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