Additive-equal fusion manufacturing method based on heat engine alternate circulation

Abstract

The invention discloses an additive-equal fusion manufacturing method based on heat engine alternate circulation, belongs to the technical field of advanced additive manufacturing, can be used for large parts, aims to improve the manufacturing efficiency, optimize the material structure and eliminate the manufacturing defects, and is suitable for various metal materials. Firstly, five layers are deposited for FSP, the deposition height is 10 mm, then FSP is carried out once every four layers are deposited, and four cycles are carried out in total; the rotating speed of the FSP is 750 rpm, the advancing speed is 50 mm / min, the pressing depth is 1 mm, and the distance between longitudinal and transverse stirring needles is 7 mm; 17 layers, namely 5 + 4 + 4 + 4 layers, are deposited on the component.

Description

Technical Field

[0001] This invention belongs to the field of advanced additive manufacturing technology, specifically an arc additive and friction stir processing technology that can be used for metal 3D printing of large components. It aims to improve manufacturing efficiency, optimize material structure, and eliminate manufacturing defects. It is applicable to a variety of metal materials, such as aluminum, titanium, and magnesium alloys. Background Art

[0002] Arc additive + friction stir processing technology, as an important part of advanced manufacturing technology, has become an important direction for future development.

[0003] Wire Arc Additive Manufacturing (WAAM) technology, with its layer-by-layer manufacturing method, shows great potential for the fabrication of complex structural parts. However, problems such as porosity, cracks, and coarse microstructures during WAAM have limited its widespread application.

[0004] Friction stir processing (FSP) is an effective material modification technology capable of grain refinement, microstructure optimization, and defect elimination. Therefore, combining FSP with additive manufacturing (AM) to form an additive manufacturing method holds significant research value and practical significance. Furthermore, high-strength and tough aluminum alloys, a primary raw material in the aerospace industry, necessitate the design and research of periodic three-dimensional configurations based on these alloys. Summary of the Invention

[0005] The purpose of the present invention is to provide a fusion manufacturing method based on stir friction and additive manufacturing. In the face of problems such as coarse grains, high porosity and grain boundary segregation in the material microstructure during additive manufacturing, stir friction (equivalent material processing) method is used to solve these problems, thereby achieving the effects of fine grain strengthening and dispersion strengthening.

[0006] A fusion manufacturing method based on friction stir and additive manufacturing, including an additive process and a friction stir treatment process. Figure 1As shown in the figure, the deposition interval between each layer of the WAAM component is 30s. This is to provide sufficient heat dissipation time and reduce the temperature within each layer. A total of 17 layers (5+4+4+4) are deposited in the component. For the WA-FSP component, five layers are first deposited for FSP. The deposition height is 10mm. This is to prevent the stirring needle from contacting the substrate during the stirring process and avoid the influence of the substrate material on the experiment. After that, FSP is performed once every four layers are deposited, for a total of four cycles. The FSP rotation speed is 750rpm, the travel speed is 50mm / min, the pressing depth is 1mm, and the vertical and horizontal stirring needle distance is 7mm. Finally, a 2319Al-Cu WA-FSP component with a size of 100mm×100mm×30mm was obtained using the WAAM+interlayer FSP process.

[0007] Compared with the prior art, the present invention has the following beneficial effects:

[0008] 1. The 2319Al-Cu additive components obtained by the method of the present invention eliminate the defects caused by the additive process. Compared with the additive components, the method of the invention greatly eliminates the pores (such as Figure 4 ), micro cracks and other micro defects, and achieved grain refinement ( Figure 5 ) effect.

[0009] 2. The method of the present invention was used to conduct experiments, and a periodic microstructure was obtained, which was composed of three areas: the weld core zone, the superposition area of the thermo-mechanically affected zone, and the remelting zone. Due to the periodic structure formed by these three areas, the mechanical properties of the additive components in the X, Y, and Z directions are effectively improved (compared with additive components). The superposition area of the thermo-mechanically affected zone is a special area obtained by the method of the present invention. This area is obtained by setting a specific distance between adjacent welds of the same layer during the friction stir processing, and it appears in the middle of two adjacent friction stir welds. The mechanical properties of the additive fusion component in the Y direction are higher than those in the X direction, which is mainly due to the existence of the superposition area of the thermo-mechanically affected zone. Due to the existence of this area, the mechanical properties of the additive component in the Y direction are higher than those in the X direction. This discovery can provide a new solution for the reliable manufacturing of complex aerospace three-dimensional components.

[0010] 3. The use of the enhanced-equal fusion process refines the grains in the stirred zone of the deposited layer, reduces the defect density, and makes the precipitated phase in the matrix randomly distributed in the stirred zone through the crushing and mixing action of the stirring tool, and increases the dislocation density in the superposition area of the thermo-mechanical influence ( Figure 6 ), thereby improving the overall performance of the material.

[0011] 4. Generally speaking, a crack starts from a point and slowly extends to all parts of the material. During the crack's expansion process, it will encounter various obstacles, such as different material orientations, different phases, and even tiny defects within the material. These obstacles will force the crack to change direction, or slow down or speed up the crack's expansion speed. Figure 7 As shown in (a), cracks initiate in pores and coarse second-phase particles during the Y-direction stretching of the additive component. Furthermore, because the grains in the additive component are surrounded by coarse second-phase particles distributed along grain boundaries, cracks propagate along grain boundaries with small misorientation, ultimately leading to overall material failure.

[0012] The schematic diagram of the joint surface of the components prepared by the additive manufacturing method is as follows: Figure 7 (b) Figure 7 (b) While a small amount of second-phase particles still exist in the superposition of the thermomechanically affected zones, they are no longer distributed continuously along the grain boundaries; at the same time, tiny second-phase particles are also dispersed within the grains. When the material is loaded, due to the dislocation network formed by the entanglement of numerous dislocation lines in the matrix and the dislocation pileups generated around the tiny second-phase particles, the combined effects of deformation strengthening and dispersion strengthening prevent crack propagation from smoothly extending along grain boundaries with smaller misorientations. Instead, the above obstacles cause crack deflection and consume the energy required for crack extension. Compared to the superposition of the thermomechanically affected zones, the coarse second-phase particles in the weld nugget zone are completely pulverized and dispersed within the crystal. Furthermore, due to the very small grain size in the weld nugget zone, the grain boundary area is significantly increased. Under the combined effects of dispersion strengthening and grain refinement, higher energy is required for crack initiation and propagation under load, and the crack propagation path is inevitably more tortuous, thereby improving the material's strength and toughness. Although the remelting zone belongs to the as-cast structure, the grains are distorted by stirring, and a large number of dislocations accumulate inside. At the same time, this area will undergo a certain degree of discontinuous dynamic recrystallization under the action of plastic deformation and heat accumulation, reducing the grain size. Therefore, the remelting zone of the additive-grade component is stronger than the general as-cast structure. More importantly, for the material as a whole, the differences in the microstructure and material properties of each partition of the additive-grade component will guide the crack to expand in a more tortuous manner after the material is loaded and cracked. The cyclical microstructure morphology will become a "speed bump" for crack propagation. Compared with traditional additive components, the crack needs to consume more energy to penetrate the entire material to cause it to completely fail, so the strength and toughness of the additive-grade component are simultaneously improved, and excellent mechanical properties are obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0014] Figure 1 (a) is a schematic diagram of additive manufacturing. Figure 1 (b) is a schematic diagram of friction stir;

[0015] Figure 2 Positioning details for friction stir processing;

[0016] Figure 3 (a) is the additive sample, Figure 3 (b) is an increase-equal sample;

[0017] Figure 4 (a) is the macroscopic morphology of the additive sample under electron microscope. Figure 4 (b) is the macroscopic morphology of the sample under electron microscope;

[0018] Figure 5 The IPF observation map of EBSD of each partition of the additive and additive-equal components and their average size;

[0019] Figure 6 KAM observation diagram of EBSD of each partition of the enhanced component and its average KAM value (dislocation density).

[0020] Figure 7 (a) is a schematic diagram of the fracture of the additive component in the Y direction. Figure 7 (b) is a schematic diagram of the three-region interface of the augmentation-equalization component. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0022] It should be noted that unless defined otherwise, all technical and scientific terms used in the present invention have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0023] For the convenience of description, if the words "up", "down", "left", "right", "front", "back", "clockwise", "counterclockwise", "horizontal", "longitudinal", "horizontal", "vertical", "top", "bottom", "length", "width" and "height" appear in the present invention, they only indicate that the direction and position relationship are consistent with the drawings themselves, and do not limit the structure. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or component referred to needs to have a specific orientation, be constructed and operate in a specific orientation. Therefore, they should not be understood as limiting the present invention.

[0024] The terms "connection", "installation" and "fixation" in the present invention should be understood in a broad sense. For example, "fixation" can be mechanical fixation, adhesive fixation, or integrated fixation. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature identified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0026] In order to make the present invention more specific and clear to be understood, the following will take a high-strength aluminum alloy block structure as an example to explain the working process of the present invention in detail:

[0027] (1) Step 1: Preprocessing

[0028] Before welding, the stirring pin and plate must be prepared. An aluminum chip cleaning tool is used to mechanically clean the stirring pin surface to prevent aluminum chips from affecting weld quality. Sandpaper is used to remove the oxide layer on the aluminum alloy plate to prevent it from affecting weld quality. The aluminum alloy surface is then cleaned with a solution of propanol and alcohol to remove oil and impurities. The additive material is 2319Al-Cu alloy welding wire.

[0029] (2) Step 2: Clamping stage 1

[0030] The aluminum alloy sheet is placed on the welding platform and clamped with a fixture. This step ensures the stability and accuracy of the sheet during the additive manufacturing process.

[0031] (3) Step 3: Positioning Phase 1

[0032] Based on the structure of high-strength aluminum alloy block components, the motion path of the six-axis industrial robot was programmed, and the forward speed of the robot end was set to 10 mm / min; the welding gun used for WAAM was positioned above the substrate, with the end of the welding wire 7 mm away from the substrate.

[0033] (4) Step 4: Welding stage 1

[0034] Set the welding current of the welding machine to 74A; set the wire feeding speed of the automatic wire feeding system to 5m / min; the average size of the single layer deposition is 100mm*100mm*2mm, the first deposition is 5 layers, and the height of the 5 layers is 10mm (such as Figure 1a) The height of the additive material is greater than the length of the stirring needle in order to prevent the substrate from affecting the friction stir process during the subsequent friction stir processing.

[0035] (5) Step 5: Clamping stage 2

[0036] The aluminum alloy additive sample was removed from the additive platform, cooled for more than 30 minutes, placed on the friction stir welding platform, clamped with a fixture, and the stirring needle was connected to the main shaft of the friction stir welding machine using a clamping tool.

[0037] (6) Step 6: Positioning Phase 2

[0038] Before moving the friction stir welding machine for positioning, set the stirring needle inclination angle to 2°. The inclination angle of the stirring needle can effectively enhance the fluidity of the material. The good fluidity of the material can not only promote the uniform filling of the weld and reduce the generation of defects, but also significantly improve the mechanical properties of the weld joint and the reliability of the overall structure, thereby comprehensively optimizing the overall quality of the welding operation. After that, adjust the X-axis and Y-axis of the friction stir welding machine by using the hand wheel of the friction stir welding machine, and move the stirring needle to the (-9,9) coordinate (such as Figure 2 As shown). Then adjust the Z axis and slowly press down the main shaft until the bottom of the stirring needle is just 0.2mm away from the additive component (place a 0.2mm metal sheet between the stirring needle and the component surface. When there is a certain resistance when the metal sheet is pulled out, make sure the distance between the stirring needle and the component surface is 0.2mm). Define this as the starting point of the first friction stir processing. The pressing depth of the stirring needle during the processing is 1mm. The end point of the friction stir processing is 82mm along the X axis. The end point coordinate is (-91,9). (As shown Figure 2 )

[0039] Step 7: Soldering Stage 2

[0040] The spindle speed is 750 rpm, the welding speed is 50 mm / min, the stirring needle inclination is 2°, and the pressing depth is 7.2 mm. The friction stir welding machine is started to weld. The stirring direction is perpendicular to the horizontal direction of the material (such as Figure 2 ), Figure 2The red circular outline is the size of the friction stir weld core area. After the first welding is completed, the stirring needle position is returned to the starting position (-9,9), and then the stirring needle is moved 7mm along the Y axis to be the starting position of the second friction stir process. The starting coordinate is (-9, 16). The friction stir process is performed again, and the end point is still 82mm along the X axis, and the end point coordinate is (-91, 16). After the second welding is completed, the stirring needle position is returned to the second starting position (-9,16), and then the stirring needle is moved 7mm along the Y axis to be the starting position of the third friction stir process. The starting coordinate is (-9, 23). The friction stir process is performed again, and the end point is still 82mm along the X axis, and the end point coordinate is (-91, 23). The subsequent welding process is analogous to this, and a total of 11 friction stir processes are performed (such as Figure 2 ).

[0041] (7) Step 8-End: Repeat the steps from Step 2 to Step 7. The only difference is that in the arc additive stage of Step 2, the number of additive layers is changed from 5 to 4, and the height is 8 mm. During the stirring process, the longitudinal and transverse distances of the stirring needle are both 7 mm. The above-described Step 2-Step 7 process is one cycle, and a total of four cycles are performed to finally obtain an additive component (such as Figure 3 The total number of additive layers during the entire experiment is 5+4+4+4=17 layers.

[0042] Example 1

[0043] 2319Al-Cu alloy was used as the experimental material. The above additive + stir friction parameters were used to conduct the experiment. This example refined the stirring zone grains in the deposited layer ( Figure 5 ), reducing the porosity ( Figure 4 ) and defect density, the precipitated phase in the matrix is randomly distributed in the stirring zone through the crushing and mixing action of the stirring tool, and the dislocation density in the superposition area of thermomechanical influence is increased ( Figure 6 Compared with the samples prepared by arc additive method alone, the ultimate tensile strength of Al-Cu alloy prepared by the additive-equal fusion process increased from 248MPa to 362MPa, and the elongation increased from 12.7% to 26.2%.

Claims

1. A method for manufacturing by additive and isotropic fusion based on alternating cycles of heat and engine, characterized by: For WA-FSP components, five layers are first deposited for FSP with a deposition height of 10 mm. After that, FSP is performed every four layers, for a total of four cycles. The FSP rotation speed is 750 rpm, the travel speed is 50 mm / min, the pressing depth is 1 mm, and the vertical and horizontal stirring needle distances are 7 mm. A total of 17 layers are deposited on the component, i.e., 5+4+4+4 layers.

2. The method according to claim 1, characterized in that The manufacturing of aluminum alloy block structural parts is as follows: (1) Step 1: Preprocessing Before welding, the stirring needle and plate need to be processed; the surface of the stirring needle is mechanically cleaned using an aluminum chip cleaning tool; the oxide layer on the surface of the aluminum alloy plate is removed using sandpaper; and the aluminum alloy surface is then cleaned using propanol and alcohol solutions. The additive material is 2319Al-Cu alloy welding wire. (2) Step 2: Clamping stage 1 Place the aluminum alloy plate on the welding platform and clamp it with a fixture; (3) Step 3: Positioning Phase 1 Program the motion path of the six-axis industrial robot and set the robot's end-of-line speed to 10 mm / min. Position the WAAM welding gun above the substrate, with the wire end 7 mm away from the substrate. (4) Step 4: Welding stage 1 The welding current of the welding machine was set to 74A; the wire feeding speed of the automatic wire feeding system was set to 5m / min; the average size of a single layer deposition was 100mm*100mm*2mm, and 5 layers were deposited for the first time, with a height of 10mm. (5) Step 5: Clamping stage 2 The aluminum alloy additive sample was removed from the additive platform, cooled for more than 30 minutes, placed on the friction stir welding platform, clamped with a fixture, and the stirring needle was connected to the main shaft of the friction stir welding machine using a clamping tool; (6) Step 6: Positioning Phase 2 Before moving the FSW machine for positioning, set the pin inclination angle to 2°. Then, use the FSW machine handwheel to adjust the X and Y axes and move the pin to the (-9,9) coordinate. Then, adjust the Z axis and press down the spindle until the bottom of the pin is just 0.2 mm above the additive component. Place a 0.2mm metal sheet between the stirring needle and the component surface, and determine that the distance between the stirring needle and the component surface is 0.2mm. Define this as the starting point of the first friction stir processing. The pressing depth of the stirring needle during the processing is 1mm. The end point of the friction stir processing is 82mm along the X axis, and the end point coordinate is (-91,9); (7) Step 7: Welding stage 2 The spindle speed is 750 rpm, the welding speed is 50 mm / min, the stirring needle inclination angle is 2°, and the pressing depth is 7.2 mm. The friction stir welding machine is started for welding. The stirring direction is perpendicular to the horizontal direction of the additive. After the first welding is completed, the stirring needle position is returned to the starting position (-9, 9), and then the stirring needle is moved 7 mm along the Y axis to set it as the starting position of the second friction stir processing. The starting coordinate is (-9, 16). The friction stir processing is performed again, and the end point is still 82 mm along the X axis, and the end point coordinate is (-91, 16). After the second welding is completed, the stirring needle position is returned to the second starting position (-9, 16), and then the stirring needle is moved 7 mm along the Y axis to set it as the starting position of the third friction stir processing. The starting coordinate is (-9, 23). The friction stir processing is performed again, and the end point is still 82 mm along the X axis, and the end point coordinate is (-91, 23). The subsequent welding process is analogous to this, and a total of 11 friction stir processes are performed. (8) Step 8: Repeat the steps from Step 2 to Step 7. The only difference is that in the arc additive stage of Step 2, the number of additive layers is changed from 5 to 4, and the height is 8 mm. During the stirring process, the longitudinal and lateral distances of the stirring needle are both 7 mm. The process from Step 2 to Step 7 is one cycle, and a total of four cycles are performed to finally obtain an additive component. The total number of additive layers in the entire test process is 5 + 4 + 4 + 4 = 17 layers.

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