An aluminum matrix composite material welding method based on friction stir additive manufacturing assisted by weld position

Abstract

The application is a kind of aluminum matrix composite welding method based on friction stir additive in weld position. The steps are as follows: preparing aluminum alloy rod for additive, adding aluminum alloy to the weld position of aluminum matrix composite through the processing mode of friction stir additive, making aluminum alloy add to the required thickness with the reciprocating motion of hollow shaft. The aluminum alloy parts of two workpieces are tightly attached without gap, and are clamped with welding fixture. The aluminum alloy layer in the weld position is welded by using fusion welding method to form aluminum alloy high-strength joint. The application adopts the combined process of friction stir additive and fusion welding, which can avoid the problems of aluminum matrix composite when using single fusion welding, the joint performance is basically not affected by the structure and performance of aluminum matrix composite itself, and can be applied to the connection between most types of aluminum matrix composites, which can greatly improve the application prospect value of aluminum matrix composite connection structure in industrial field.

Description

Technical Field

[0001] This invention relates to the field of aluminum-based composite material joining technology, and more specifically, to a welding method for aluminum-based composite materials based on friction stir additive manufacturing at the weld location. Background Technology

[0002] Aluminum-based composites possess many excellent properties, such as high specific strength, high specific modulus, high wear resistance, and high temperature resistance. Furthermore, their simple manufacturing process, low cost, and ease of large-scale industrial production have made them a current hot topic in the development and research of this type of material. As a novel structural material, reliable welding and joining are crucial prerequisites for its engineering applications. Therefore, while researching and developing aluminum-based composites, scholars both domestically and internationally have also conducted extensive research on the joining issues of this material. However, joining methods such as fusion welding, brazing, diffusion welding, and traditional friction welding have certain shortcomings. Therefore, friction stir welding (FSW) is currently commonly used for joining aluminum-based composites. Friction stir welding heats the metal on the workpiece surface to a ductile state by applying rotational and frictional forces to the joint area, then mixes them to form a uniform bond. This technology has many advantages, such as not requiring external filler materials, not needing to melt metal, and low energy consumption.

[0003] However, for aluminum-based composites, the matrix is ​​typically an aluminum-based material with good plasticity and toughness, thus its weldability is generally good. The reinforcing phase, on the other hand, is often composed of non-metallic or metallic compound particles with high strength, high modulus, high melting point, low density, and low coefficient of linear expansion; these reinforcing phases generally have poor weldability. When joining these materials, in addition to addressing the bonding of the metallic matrix, the bonding of the metal with non-metals or metallic compounds also needs to be addressed. In this case, the weldability of the aluminum-based material is not the primary issue; the key is to achieve a good connection between the reinforcing phase and the matrix. Even friction stir welding cannot completely solve all the problems that arise during the welding process between aluminum-based composites.

[0004] Currently, existing friction stir welding methods for joining aluminum-based composite materials have many shortcomings:

[0005] (1) Due to the presence of reinforcing phases, aluminum matrix composites have poor formability, making it more difficult to determine the process parameters for friction stir welding of aluminum matrix composites than for ordinary aluminum alloys. For unreinforced aluminum alloys, even at welding speeds as high as 2000 mm / min, a certain range of applicable friction stir welding parameters and good weld quality can be obtained. However, to obtain high-quality welded joints between aluminum matrix composites, a lower welding speed must be used, making it difficult to improve processing efficiency. In addition, as the volume (or mass) fraction of the reinforcing phase increases, its optimal welding area narrows. This means that in aluminum matrix composites containing a high volume fraction of reinforcing phases, more careful selection of appropriate welding parameters is required to ensure weld quality.

[0006] (2) When the coefficients of linear expansion of the reinforcing phase and the matrix differ significantly, large internal stresses will be generated during the heating and cooling process of welding, leading to interface separation. Therefore, the use of fusion welding will result in a decrease in the mechanical properties of the joint.

[0007] (3) From the perspective of chemical compatibility, the aluminum matrix and the reinforcing phase in aluminum matrix composites are often thermodynamically unstable over a wide temperature range. During the joining process, when a certain temperature is reached, the two may react. For example, in the fusion welding process of aluminum matrix composites reinforced with carbon-based reinforcing phase, Al4C3 brittle phase will be generated at the joint, which will lead to a decrease in joint strength.

[0008] Therefore, in order to address the above shortcomings, there is an urgent need to provide a method for joining aluminum-based composite materials that can ensure the strength of the connection between aluminum-based composite materials and be applicable in practical engineering welding. Summary of the Invention

[0009] The technical problem solved by this invention is to provide a welding method for aluminum-based composite materials based on friction stir additive manufacturing at the weld position.

[0010] The technical solution to achieve the objective of this invention is as follows:

[0011] Aluminum alloy friction stir additive manufacturing is performed at the weld seam of the aluminum-based composite material to be welded; subsequently, the aluminum alloy additive area is subjected to fusion welding to complete the connection of the aluminum-based composite material.

[0012] Furthermore, the method specifically includes:

[0013] Step 1: Additive Material Preparation: Aluminum alloy rods for additive manufacturing are prepared using traditional processing methods such as casting and extrusion molding. The prepared additive materials are then polished, cleaned, and dried in a vacuum.

[0014] Step 2: Assembly: Place the additive material obtained in Step 1 into the hollow shaft of the AFSD equipment to complete the fit between the aluminum alloy rod and the hollow shaft. Use welding fixtures to vertically clamp the base material, ensuring that the weld side of the aluminum-based composite material is in close contact with the lower end of the aluminum alloy rod.

[0015] Step 3: Friction Stir Additive Manufacturing: The aluminum alloy rod is rotated with the hollow shaft by clamping or fitting, and an axial force is applied to the rod, causing intense friction between the rod and the aluminum-based composite material on the working plane. At the same time, the hollow shaft is driven to move laterally, and the aluminum alloy material spreads laterally under the extrusion of the hollow shaft shoulder to form the initial deposition layer. Finally, with the reciprocating motion of the hollow shaft, subsequent deposition layers are added upwards to the required thickness.

[0016] Step 4: After the additive manufacturing is complete, wait for the workpiece to cool down and then remove the additively manufactured workpiece.

[0017] Step 5: Assemble the workpieces: Connect the two cooled additive workpieces from Step 4, ensuring the aluminum alloy parts of the two workpieces fit together tightly without gaps, and tighten them using welding fixtures.

[0018] Step 6: Spot welding: Use a suitable heat source to perform center spot welding.

[0019] Step 7: Fusion welding: Use fusion welding methods such as electron beam welding, laser welding, and arc welding to weld the center, adjust the process parameters, and control the weld fusion ratio to form a high-strength aluminum alloy joint.

[0020] Step 8: After welding is completed, wait for the workpiece to cool down, then remove the welded workpiece.

[0021] Furthermore, the aluminum-based composite materials include: graphene-reinforced aluminum-based composite materials, silicon carbide-reinforced aluminum-based composite materials, carbon nanotube-reinforced aluminum-based composite materials, and carbon fiber-reinforced aluminum-based composite materials, etc.

[0022] Furthermore, the aluminum alloy additive layer does not chemically react with the reinforcing phase in the aluminum-based composite material.

[0023] Furthermore, in step two, the diameter of the aluminum alloy rod is 1-20 mm and the length is 100-300 mm, with the specific diameter depending on the thickness of the aluminum-based composite material to be welded.

[0024] Furthermore, the specific parameters for the friction stir additive manufacturing process in step three are: hollow shaft rotation speed 200–600 r / min. -1 Lateral movement speed 60–230 mm / min -1 Additive material feed rate: 20–120 mm / min -1 .

[0025] Furthermore, during the friction stir additive manufacturing process in step three, the temperature did not reach the material's melting point, but was approximately 50% to 90% of the melting point.

[0026] Compared with the prior art, the present invention has the following significant advantages:

[0027] (1) The joining process method of this application involves adding an aluminum alloy layer by performing friction stir additive manufacturing (AFSD) at the weld of the aluminum-based composite material. Compared with the traditional friction stir welding method, the additive material added by friction stir additive manufacturing is not constrained in the radial direction and can move freely between the shoulder surface and the additive layer.

[0028] (2) The joining process method of this application adds aluminum alloy through friction stir additive manufacturing. The additive material is mainly subjected to the stirring action of the axial surface stirring protrusions, rather than the stirring action of the stirring pins as in friction stir welding. Compared with friction stir welding, the stirring action generated by friction stir additive manufacturing is weaker, and the reinforcing phase in the aluminum matrix composite material hardly flows into the aluminum alloy layer. Therefore, when performing fusion welding between aluminum alloys, high-temperature welding methods such as fusion welding can be used without worrying about the decrease in joint mechanical properties due to the reaction of the reinforcing phase.

[0029] (3) The joining process of this application has a lower processing temperature compared to fusion welding. During the friction stir additive manufacturing process, the processing temperature is lower than the melting point of the material. Even if there is a difference in the coefficient of linear expansion between the reinforcing phase and the matrix, there will be no large internal stress that would cause the interface to separate. At the same time, due to the low processing temperature, the reinforcing phase in the aluminum matrix composite material will not react chemically with the matrix to generate a brittle phase, thereby ensuring the mechanical properties of the joint.

[0030] (4) The joining process method of this application transforms the joining between aluminum-based composite materials into the joining between aluminum-based composite materials and aluminum alloys, and between aluminum alloys. By combining friction stir additive manufacturing and fusion welding, a good connection between aluminum-based composite materials and aluminum alloys is achieved, avoiding the problems that occur in the joining process of aluminum-based composite materials when using friction stir welding alone, such as the aluminum-based composite material breaking or large changes in performance, which leads to a decrease in product yield and failure to meet technical requirements, thus reducing the risk of product scrap.

[0031] (5) The joining process method of this application, wherein the joining process between aluminum alloys is relatively mature, and the range of process parameters for obtaining high-quality aluminum alloy joints is relatively large. The joining process of this application is simple to operate, low in cost, and easy to realize industrial mass production, which can greatly enhance the application prospects and value of aluminum-based composite material joining structures in the industrial field.

[0032] (6) The connection process of this application is a combination of friction stir additive manufacturing and melting welding. The joint performance is basically unaffected by the structure and performance of the aluminum-based composite material itself, and can be applied to the connection between most types of aluminum-based composite materials. Attached Figure Description

[0033] Figure 1 This invention relates to a welding method for aluminum-based composite materials based on friction stir additive manufacturing assisted by friction stir at the weld seam. A schematic diagram of the principle is shown (taking particle-reinforced aluminum-based composite material as an example); Figure (a) is a schematic diagram of friction stir additive manufacturing at the weld seam of the particle-reinforced aluminum-based composite material, Figure (b) shows the state of the two workpieces after friction stir additive manufacturing, and Figure (c) shows the state after fusion welding. Detailed Implementation

[0034] The present invention will be further described below with reference to the accompanying drawings.

[0035] This invention provides a welding method for aluminum-based composite materials based on friction stir additive manufacturing at the weld location.

[0036] like Figure 1 As shown, a joining method for aluminum-based composite materials based on friction stir additive manufacturing at the weld location transforms the joining of aluminum-based composite materials into joining between aluminum-based composite materials and aluminum alloys, and between aluminum alloys. A good connection between aluminum-based composite materials and aluminum alloys is achieved through a combination of friction stir additive manufacturing and fusion welding processes.

[0037] A welding method for aluminum-based composite materials based on friction stir additive manufacturing at the weld location, the specific steps of which are as follows:

[0038] Step 1: Additive Material Preparation: Aluminum alloy rods for additive manufacturing are prepared using traditional processing methods such as casting and extrusion molding. The prepared additive materials are then polished, cleaned, and dried in a vacuum.

[0039] Step 2: Assembly: Place the additive material obtained in Step 1 into the hollow shaft of the AFSD equipment to complete the fit between the aluminum alloy rod and the hollow shaft. Use welding fixtures to vertically clamp the base material, ensuring that the weld side of the aluminum-based composite material is in close contact with the lower end of the aluminum alloy rod.

[0040] Step 3: Friction Stir Additive Manufacturing: The aluminum alloy rod is rotated with the hollow shaft by clamping or fitting, and an axial force is applied to the rod, causing intense friction between the rod and the aluminum-based composite material on the working plane. At the same time, the hollow shaft is driven to move laterally, and the aluminum alloy material spreads laterally under the extrusion of the hollow shaft shoulder to form the initial deposition layer. Finally, with the reciprocating motion of the hollow shaft, subsequent deposition layers are added upwards to the required thickness.

[0041] Step 4: After the additive manufacturing is completed, wait for the workpiece to cool down and then remove the additively manufactured workpiece.

[0042] Step 5: Assemble the workpieces: Connect the two additive workpieces that have been cooled in step 4, and fit the aluminum alloy parts of the two workpieces tightly together without leaving any gaps. Use welding fixtures to tighten them.

[0043] Step 6: Spot welding: Use a suitable heat source to perform spot welding at the center.

[0044] Step 7: Fusion welding: Electron beam welding, laser welding, arc welding and other fusion welding methods are used for center welding. The process parameters are adjusted and the weld fusion ratio is controlled to form a high-strength aluminum alloy joint.

[0045] Step 8: After welding is completed, wait for the workpiece to cool down, then remove the welded workpiece.

[0046] In the second step of this invention, the diameter of the aluminum alloy rod is 1-20 mm and the length is 100-300 mm. The specific diameter depends on the thickness of the aluminum-based composite material to be welded.

[0047] The specific parameters for the friction stir additive manufacturing process in the third step of this invention are: hollow shaft rotation speed 200-600 r / min. -1 Lateral movement speed 60–230 mm / min -1 Additive material feed rate: 20–120 mm / min -1 .

[0048] In the third step of this invention, the temperature during the friction stir additive manufacturing process does not reach the melting point of the material, but is approximately 50% to 90% of the melting point.

[0049] The principle of this invention is that the reinforcing phase and the matrix react chemically at a certain temperature, making it difficult to directly process aluminum-based composite materials using high-temperature fusion welding. Furthermore, joining aluminum-based composite materials via friction stir welding also has certain limitations. Therefore, by adding an aluminum alloy layer to the weld seam of the aluminum-based composite material through friction stir additive manufacturing, the amount of reinforcing phase entering the aluminum alloy is reduced, thus not affecting subsequent high-temperature fusion welding of the additive-grown aluminum alloy. This ensures a good connection between the aluminum-based composite material and the aluminum alloy, avoiding the problems that occur during the joining process when using friction stir welding alone.

[0050] Example 1

[0051] For a thickness of 5mm containing 20% ​​SiC p Friction stir additive manufacturing (AFSD) tests were conducted on 6061 aluminum alloy particle-reinforced aluminum matrix composites. Aluminum alloy rods with a diameter of 4 mm and a length of 100 mm were prepared by extrusion before additive manufacturing. Wire cutting was used to separate SiC...p Particle-reinforced aluminum matrix composite material is cut into 50mm × 30mm × 5mm sheets. For example... Figure 1 As shown in Figure a, an aluminum alloy rod was added to the weld of an aluminum matrix composite material using friction stir additive manufacturing, achieving an aluminum alloy additive with a height of 3 mm. The process parameters used for friction stir additive manufacturing were: hollow shaft speed 300 r / min. -1 Lateral movement speed 120 mm·min -1 Additive material feed rate: 70 mm / min -1 Compared to the properties of the aluminum alloy before feeding, the grain size of the material after AFSD decreased from 200μm to (15±4)μm, and the hardness increased to 112±2.65HV.

[0052] After completing AFSD, the aluminum alloy parts of the two workpieces are tightly fitted together and clamped, then placed in a vacuum chamber for welding. Electron beam welding uses an accelerating voltage of 60kV, a focal point 3mm below the upper surface of the component, a welding speed of 400mm / min, an electron beam current of 7mA, an electron beam scanning frequency of 300Hz, a scanning amplitude of 3mm, and a circular wave scanning waveform. After welding, the components are cooled in the vacuum chamber for 5 minutes, then the vacuum chamber is opened, and the welded components are removed. Figure 1 As shown in c. The tensile mechanical property test of the component showed a strength of 252 MPa, which is 86% of that of the parent material, thus meeting the strength requirements.

[0053] Example 2

[0054] For a thickness of 5mm containing 20% ​​SiC p Friction stir additive manufacturing (AFSD) tests were conducted on particle-reinforced aluminum matrix composites made from 7075 aluminum alloy. Aluminum alloy rods with a diameter of 4 mm and a length of 100 mm were prepared by extrusion before additive manufacturing. Wire cutting was used to separate SiC... p Particle-reinforced aluminum matrix composite material is cut into 50mm × 30mm × 5mm sheets. For example... Figure 1 As shown in Figure a, an aluminum alloy rod was added to the weld of an aluminum matrix composite material using friction stir additive manufacturing, achieving an aluminum alloy additive with a height of approximately 3 mm. The process parameters used for friction stir additive manufacturing were: hollow shaft speed 225 r·min. -1 Lateral movement speed 50 mm·min -1 Additive material feed rate 50 mm / min -1 Compared to the properties of the aluminum alloy before feeding, the grain size of the material after AFSD decreased to (4±2)μm, and the hardness increased to 105±3HV.

[0055] After completing AFSD (Automatic Laser Sampling), the aluminum alloy parts of the two workpieces are tightly fitted together and clamped for laser welding. The laser welding parameters are: laser power 1150W, laser scanning speed 9mm / s. After welding, the parts are cooled for 10 minutes and then removed. Figure 1 As shown in Figure c, the tensile mechanical property test showed a strength of 225 MPa, reaching 82% of the strength of the base material, thus meeting the strength requirements.

[0056] Comparative Example 1

[0057] Direct laser welding was performed on 20% SiCp / 2024Al composite sheets with dimensions of 60mm × 30mm × 1.5mm. Under various experimental conditions, the laser welding parameters with the best joint mechanical properties were: laser power of 1150W, laser scanning speed of 9mm / s, and a maximum tensile strength of 76MPa, significantly lower than the base metal strength of 270MPa, reaching only 28% of the base metal strength. The highest yield strength was 28MPa, significantly lower than the base metal strength of 140MPa, also reaching 20% ​​of the base metal strength. The elongation after fracture, whether in the base metal or the welded joint, was no higher than 5%, indicating that direct high-temperature laser welding of SiCp / 2024Al composites would result in a significant decrease in material strength due to the presence of loose pores and brittle Al4C3 phase at the joint. Therefore, direct high-temperature fusion welding is not suitable for joining aluminum-based composite materials.

Claims

1. A welding method for aluminum-based composite materials based on friction stir additive manufacturing at the weld seam, characterized in that, The aluminum alloy layer is additively processed at the weld joint of the aluminum matrix composite material using friction stir additive manufacturing (AFSD). The aluminum alloy layer is then used as the weld joint in the aluminum matrix composite material to perform fusion welding on the aluminum alloy additive area to complete the connection of the aluminum matrix composite material. Step 1: Additive material preparation: Aluminum alloy rods for additive manufacturing are prepared using traditional processing methods such as casting and extrusion molding; the prepared additive materials are then polished, cleaned, and dried in a vacuum. Step 2: Assembly: Place the additive material from Step 1 into the hollow shaft of the AFSD equipment to complete the fit between the aluminum alloy rod and the hollow shaft; use a clamp to vertically clamp the base material and ensure that the weld side of the aluminum-based composite material is in close contact with the lower end of the aluminum alloy rod. Step 3: Friction Stir Additive Manufacturing: The aluminum alloy rod is rotated with the hollow shaft by clamping or fitting, and an axial force is applied to the rod, causing the rod to rub violently against the aluminum-based composite material on the working plane; at the same time, the hollow shaft is driven to move laterally, and the aluminum alloy material is laterally spread under the extrusion of the hollow shaft shoulder to form the initial deposition layer, and finally, with the reciprocating motion of the hollow shaft, subsequent deposition layers are added upward to the required thickness; Step 4: After the additive manufacturing process is complete, wait for the workpiece to cool down and then remove the additively manufactured workpiece. Step 5: Assemble the workpieces: Connect the two cooled additive workpieces from Step 4, ensuring the aluminum alloy parts of the two workpieces fit together tightly without gaps, and tighten them using welding fixtures. Step Six: Spot Welding: Using a suitable heat source, perform spot welding at the center. Step 7: Fusion Welding: Electron beam welding, laser welding, and arc welding are used for fusion welding to center the joints. Process parameters are adjusted and the weld fusion ratio is controlled to form a high-strength aluminum alloy joint. Step 8: After welding is completed, wait for the workpiece to cool down, then remove the welded workpiece.

2. The method according to claim 1, characterized in that, Aluminum-based composite materials include: graphene-reinforced aluminum-based composites, silicon carbide-reinforced aluminum-based composites, carbon nanotube-reinforced aluminum-based composites, and carbon fiber-reinforced aluminum-based composites.

3. The method according to claim 1, characterized in that, The aluminum alloy additive layer does not chemically react with the reinforcing phase in the aluminum matrix composite.

4. The method according to claim 1, characterized in that, In step two, the aluminum alloy rod has a diameter of 1 to 20 mm and a length of 100 to 300 mm. The specific diameter depends on the thickness of the aluminum-based composite material to be welded.

5. The method according to claim 1, characterized in that, The specific parameters for friction stir additive manufacturing in step three are: hollow shaft rotation speed 200 ~ 600 r·min -1 Lateral movement speed: 60 ~ 230 mm·min -1 Additive material feed rate: 20~120 mm·min -1 .

6. The method according to claim 1, characterized in that, In step three, the temperature during the friction stir additive manufacturing process does not reach the material's melting point, but is only 50% to 90% of the melting point.

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