A SiC / aluminum matrix composite off-focus laser filling welding method based on energy redistribution

Abstract

The application belongs to the technical field of welding, and particularly relates to a SiC / aluminum-based composite material off-focus laser filler welding method based on energy redistribution. The SiC / aluminum-based composite material comprises silicon carbide particle reinforcements and an aluminum matrix, the volume fraction of the silicon carbide particle reinforcements is 5% to 30%, and the rest is the aluminum matrix; the SiC / aluminum-based composite material plate base metals are butt-jointed, and under the argon atmosphere, a welding filler material is used to perform off-focus laser filler welding on the SiC / aluminum-based composite material plate base metals under the action of laser. The method comprises adjusting and controlling parameters such as the off-focus distance of the laser working spot, the laser power, the laser scanning rate and the like, adjusting and controlling the proportion of the welding filler and the base metal absorbing laser energy, reducing the laser energy absorbed by the base metal in the welding process, realizing laser energy redistribution of the filler and the base metal, hindering chemical reactions between SiC and the aluminum matrix in the welding process, thereby eliminating brittle phases such as Al4C3, AlSiC and the like in the welded joint, and realizing high-strength welding of the SiC / Al composite material.

Description

Technical Field

[0001] This invention belongs to the field of welding technology, and in particular relates to a laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution defocusing. Background Technology

[0002] Aluminum-based composites use aluminum alloys as the matrix, with reinforcements added to improve the material's properties. Different shapes and types of reinforcements can be added according to the specific application requirements, giving aluminum-based composites a broad range of applications. SiC, with its high hardness and good wear resistance, is a commonly used reinforcement in aluminum-based composites. However, during the welding process of SiC / aluminum-based composites, a chemical reaction easily occurs between the matrix Al alloy and the SiC reinforcement, forming brittle phases such as Al4C3 and AlSiC. This reduces the weld quality of the joint and prevents the achievement of high-strength connections in SiC / aluminum-based composites.

[0003] Currently, there are many welding methods for SiC-reinforced aluminum matrix composites, with laser welding and friction stir welding being the most widely used. Laser welding offers advantages such as high welding speed and precision. However, due to the different melting points of aluminum (around 660℃) and SiC (around 2700℃) under laser irradiation—aluminum matrix has a low absorption rate, while SiC has a relatively high absorption rate—laser-welded composites are prone to producing a large number of brittle phases, resulting in poor joint performance. Friction stir welding, being a solid-state welding method, has a lower welding temperature compared to laser welding, significantly reducing the interaction between the aluminum matrix and the reinforcing phase. However, this method has specific requirements for the workpiece shape and structure, limiting its applicability to simpler structures.

[0004] Currently, many scholars have conducted extensive research on the problem of brittle phases easily generated during the fusion welding process of SiC-reinforced aluminum matrix composites. These studies mainly focus on controlling factors such as laser frequency and silicon content in the molten pool to reduce intermetallic compounds during laser welding. However, none of these methods have fundamentally eliminated the brittle phases in the weld joint. Therefore, it is necessary to conduct in-depth research on SiC-reinforced aluminum matrix composites to eliminate brittle phases in the weld joint and achieve high-strength welding of SiC-reinforced aluminum matrix composites. This invention is supported by the National Natural Science Foundation of China (51965022). Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a defocused laser filler welding method for SiC / aluminum matrix composites based on energy redistribution. This method solves the problem of brittle phases easily generated during the fusion welding of SiC-reinforced aluminum matrix composites in existing technologies. By adjusting the ratio of laser energy absorbed by the welding filler and the base material, the laser energy absorbed by the base material during welding is reduced, hindering the chemical reaction between SiC and the aluminum matrix during welding. This eliminates brittle phases such as Al4C3 and AlSiC in the weld joint, thereby achieving high-strength welding of SiC / Al composite materials.

[0006] The technical solution of this invention is:

[0007] A defocused laser filler welding method for SiC / aluminum matrix composites based on energy redistribution is disclosed. The SiC / aluminum matrix composite contains a certain volume fraction of silicon carbide particle reinforcement and aluminum matrix, with the volume fraction of silicon carbide particle reinforcement being 5% to 30% and the remainder being aluminum matrix. The SiC / aluminum matrix composite sheet base materials are butt-jointed, and under an argon atmosphere, the welding filler material is applied to the SiC / aluminum matrix composite sheet base materials under the action of a laser to perform defocused laser filler welding.

[0008] The aforementioned defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution has SiC particles with a particle size of 5–15 μm.

[0009] The aforementioned defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution involves grinding the selected SiC / aluminum-based composite material sheet to remove the oxide layer before performing defocused laser filler welding.

[0010] The aforementioned defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution implements defocused laser filler welding by adjusting the defocus distance of the laser working spot, laser power, laser scanning rate, and filler composition parameters.

[0011] The aforementioned laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution utilizes a method of controlling a single variable to adjust the laser working spot defocus distance, laser power, laser scanning rate, and filler composition parameters for welding.

[0012] The aforementioned defocused laser filler welding method for SiC / aluminum matrix composites based on energy redistribution has the following process parameters: the defocus distance of the laser working spot is -60mm to -5mm or 10mm to 90mm, the laser welding power is 500w to 3000w, the laser scanning rate is 3mm / s to 30mm / s, and SiC and aluminum matrix do not react in the welded joint, resulting in a composite material welded joint without Al4C3 or AlSiC brittle phases.

[0013] The aforementioned defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution involves a SiC / aluminum-based composite material base material with a thickness of 0.1mm to 4mm, a V-shaped groove with a groove angle of 15° to 90° at the welding location, and a welding shielding atmosphere of argon with a volume purity of ≥99.9%.

[0014] The aforementioned defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution involves grinding, cleaning, and drying the V-groove before laser welding. The cleaning agent is an ethanol solution with a concentration of 94–98 wt%.

[0015] The aforementioned laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution involves welding aluminum alloy or its composite material powder or wire during the SiC / aluminum-based composite material base material welding process. The filler is fed coaxially with powder or wire, and the coaxial feeding rate is 3-25 g / min.

[0016] The aforementioned laser filler welding method based on energy redistribution for SiC / aluminum composite materials using defocusing involves laser welding filler powder with a particle size of 150–300 mesh and laser welding filler wire with a diameter of 3–10 mm.

[0017] The design concept of this invention is:

[0018] During the welding process of metal matrix composites, the reinforcement and matrix are prone to adverse reactions, generating brittle phases and reducing the performance of the weld joint. The metal matrix composite material used in this invention is silicon carbide particle-reinforced aluminum matrix composite (SiC / aluminum matrix composite), wherein the volume fraction of SiC is 5% to 30%, and the welding filler is aluminum alloy and its composite powder or wire. By adjusting parameters such as the laser working spot defocus distance, laser power, and laser scanning rate, the ratio of laser energy absorbed by the welding filler and the base material is controlled, reducing the laser energy absorbed by the base material during the welding process, and hindering the chemical reaction between the reinforcement and the matrix during the welding process, thereby eliminating the brittle phase in the weld joint and achieving high-strength welding of composite materials.

[0019] This invention fully utilizes the Gaussian distribution of laser energy along the diameter of the laser spot, where the energy density is high at the center and significantly decreases as it deviates from the center. By applying different defocusing amounts during the welding process, the laser energy density acting on the base material can be controlled. The greater the defocusing amount, the larger the laser spot, and the lower the energy density absorbed by the base material. Therefore, controlling the defocusing amount can effectively achieve the redistribution of laser energy between the filler and the base material. Simultaneously, the energy in each region is also related to the laser power, scanning rate, and filler absorbance. The higher the laser power and the lower the scanning rate, the greater the energy absorbed in each region. Different filler compositions result in different laser absorption rates, thus further achieving the redistribution of energy acting on the filler and base material during the welding process, thereby obtaining the desired weld joint morphology.

[0020] The advantages and beneficial effects of this invention include the following:

[0021] 1. This invention employs the matching of adjustable laser power and laser working spot defocus distance to fully utilize the Gaussian distribution of laser source energy, enabling the central filler to fully absorb laser energy, increasing the fluidity of the weld pool, enhancing the fusion of the weld joint, and improving welding quality.

[0022] 2. This invention controls the linear energy during welding by adjusting parameters such as laser power, welding speed, and laser spot defocus distance. By utilizing defocus welding, the peripheral laser energy density is rapidly reduced, lowering the temperature of the base material at the joint and altering the heat input of the base material. This keeps the temperature of the base material at the joint below the reaction temperature of SiC and Al, preventing chemical reactions between SiC and Al and eliminating brittle phases in the welded joint, thereby achieving high-strength welding of SiC / aluminum-based composite materials.

[0023] 3. The welding method of the present invention does not require complicated pre-welding preparation work. By controlling the process, the forming quality of the weld can be effectively improved, which can help the large-scale industrial application of aluminum-based composite materials. Attached Figure Description

[0024] Figure 1 Metallographic images of laser welding at different power levels of 1200W are shown. Among them, (a) shows the microstructure of the weld center, and (b) shows the microstructure of the weld interface (fusion zone).

[0025] Figure 2 The image shows the metallographic structure of the welded joint under laser power of 1200W and a laser spot defocus distance of 30mm.

[0026] Among them, (a) is a microstructure diagram of the weld joint, and (b) is a microstructure diagram of the weld interface (fusion zone).

[0027] Figure 3The image shows the XRD pattern of the welded joint in Example 2. In the figure, the horizontal axis 2θ represents the diffraction angle (°), and the vertical axis Intensity represents the relative intensity.

[0028] Figure 4 The image shows the microstructure of a joint with a laser working spot defocus distance of 30 mm at a laser power of 1200 W without beveling. (a) shows the microstructure at the center of the weld, and (b) shows the macroscopic morphology of the welded joint.

[0029] Figure 5 This is a schematic diagram of the laser welding process. In the diagram, 1 is the laser beam, 2 is the laser focus, 3 is the coaxial powder feeder, 4 is the laser spot, 5 is the base material, and h is the defocus distance of the laser working spot. Detailed Implementation

[0030] In its specific implementation, this invention provides a defocused laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution. By adjusting parameters such as welding speed (laser scanning rate), laser spot focal defocus distance, laser power, powder feeding rate, and V-groove, the oxide layer on the surface of the SiC / aluminum-based composite material sheet is removed by grinding, and a V-groove is opened at the welding location. Under an argon atmosphere, the filler material is fed coaxially by the laser to perform defocused filler welding on the SiC / aluminum-based composite material sheet under the action of the laser. The V-groove and the SiC / aluminum-based composite material sheet base material form a good weld joint without brittle phases.

[0031] Preferably, the SiC / aluminum-based composite material has a thickness of 0.1 mm to 4 mm, the opening angle of the V-groove is 15° to 90°, and the volume purity of the argon gas is ≥99.99%.

[0032] As a preferred method, SiC / aluminum-based composite materials are laser welded using a coaxial powder feeding method, with a powder feeding rate of 3 g / min to 25 g / min.

[0033] Preferably, the laser power for laser welding is 500W to 3000W, the laser working spot defocus distance is -60mm to -5mm or 10mm to 90mm, and the laser scanning rate is 3mm / s to 30mm / s.

[0034] Before laser welding, the V-groove of the present invention should be ground, cleaned and dried. The cleaning agent is preferably an ethanol solution, and the concentration of the ethanol solution is preferably 94-98 wt%, more preferably 95-97 wt%, and even more preferably 96 wt%.

[0035] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0036] Example 1

[0037] In this embodiment, the SiC / aluminum matrix composite material substrate is prepared from SiC particles with a volume fraction of 15% and an aluminum alloy matrix, and the substrate has a shape and size of 50×20×2mm. The particle size of the SiC particles is approximately 10μm, and the particle size of the laser-welded filler powder AlSi12 is approximately 150-300 mesh.

[0038] Laser welding was performed on the surface of a 2mm thick SiC / aluminum composite substrate using a coaxial powder feeding method at a laser power of 1200W. The SiC / aluminum composite substrate was ground to remove the oxide layer, cleaned with 96wt% alcohol to remove oil stains, and a V-groove was prepared. With other parameters kept constant, the laser working spot was focused on the substrate at a focal distance of 0. The welding speed was controlled at 18mm / s, the coaxial powder feeding speed at 12g / min, and the laser power at 1200W under an argon atmosphere with a volume purity of 99.99%. The coaxial powder feeding laser welding of the substrate was investigated to explore the solidification and formation of the weld pool and obtain a good weld joint.

[0039] like Figure 1 As shown in the figure, the weld joint morphology obtained under different power conditions in this embodiment is illustrated. It can be seen from the figure that, under these controlled conditions, a large number of needle-like phases are found distributed in the weld microstructure at the weld center. This is due to the reaction between the melting of SiC and the aluminum matrix to form brittle intermetallic compounds. Simultaneously, it can be observed that as the heat input of the laser increases, the needle-like structures in the weld microstructure also grow larger. The presence of a large number of needle-like structures leads to increased brittleness and decreased toughness of the weld joint, resulting in weld joint deterioration and a sharp decline in weld joint quality.

[0040] Example 2

[0041] In this embodiment, the SiC / aluminum matrix composite material substrate is prepared from SiC particles with a volume fraction of 15% and an aluminum alloy matrix, and the substrate has a shape and size of 50×20×2mm. The particle size of the SiC particles is approximately 10μm, and the particle size of the laser-welded filler powder AlSi12 is approximately 150-300 mesh.

[0042] Laser welding was performed on the surface of a 2mm thick SiC / aluminum composite substrate using a 1200W laser with coaxial powder feeding. The SiC / aluminum composite substrate was ground to remove the oxide layer, cleaned with 96wt% alcohol to remove oil, and a V-groove was prepared. With other parameters kept constant, the substrate was laser-welded with coaxial powder feeding at a laser working spot defocus distance of 30mm, a welding speed of 18mm / s, a coaxial powder feeding speed of 12g / min, and an argon atmosphere with a volume purity of 99.99%. The solidification and formation of the weld pool were investigated to obtain a good weld joint.

[0043] like Figure 2 As shown in the figure, the weld joint morphology obtained under different power conditions in this embodiment shows that no needle-like brittle phases are generated in the weld joint under this controlled condition, and no needle-like brittle phases are found at the weld interface, indicating that the interface has a good profile morphology. Figure 3 As shown, XRD analysis was performed on the weld of the welded joint. The analysis indicated that no Al4C3 brittle phase appeared in the weld, and this welding method can effectively suppress the formation of Al4C3 needle-like structures. Therefore, this method effectively controls the formation of brittle phases during laser welding of SiC / aluminum composites, enabling high-strength welding of SiC / aluminum composites.

[0044] Example 3

[0045] In this embodiment, the SiC / aluminum matrix composite material substrate is prepared from SiC particles with a volume fraction of 15% and an aluminum alloy matrix, and the substrate has a shape and size of 50×20×2mm. The particle size of the SiC particles is approximately 10μm, and the particle size of the laser-welded filler powder AlSi12 is approximately 150-300 mesh.

[0046] Laser welding was performed on a 2mm thick SiC / aluminum composite substrate using coaxial powder feeding at a laser working spot defocus distance of 30mm. Excluding the influence of other parameters, the SiC / aluminum composite substrate was ground to remove the oxide layer. A butt joint was used without beveling, and all other parameters were the same as in Case 2. Coaxial powder feeding laser welding was performed on the substrate under the same laser power of 1200W, welding speed of 18mm / s, coaxial powder feeding speed of 12g / min, and an argon atmosphere with a volume purity of 99.99%. The study investigated the solidification and formation of the weld pool and the achievement of a good weld joint.

[0047] like Figure 4As shown in the figure, the weld morphology and metallographic morphology at the weld joint interface obtained in this embodiment show that the weld joint penetration is shallow under this process, no brittle Al4C3 acicular phase is found in the weld center, the weld interface is distinct, and the weld joint quality is good.

[0048] like Figure 5 As shown, the structure of the laser welding process for the weld structure obtained by the present invention is as follows: the laser beam 1 is positioned above the base material 5 (SiC / aluminum-based composite material plate base material) and corresponds to the weld. A coaxial powder feeder 3 is provided above the weld. The weld is filled with powder through the coaxial powder feeder 3. The distance from the laser focus 2 to the base material 5 is the defocus distance h of the laser working spot. The laser spot 4 at the lower end of the laser beam 1 corresponds to the weld. Laser welding is performed at the defocus distance h of the laser working spot.

[0049] The results show that by adjusting parameters such as the laser working spot defocus distance, laser power, and laser scanning rate, this invention regulates the ratio of laser energy absorbed by the welding filler and the base material, reduces the laser energy absorbed by the base material during welding, realizes the redistribution of laser energy between the filler and the base material, and hinders the chemical reaction between SiC and the aluminum matrix during welding, thereby eliminating brittle phases such as Al4C3 and AlSiC in the weld joint and achieving high-strength welding of SiC / Al composite materials.

[0050] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution defocusing, characterized in that, The SiC / aluminum matrix composite material contains a certain volume fraction of silicon carbide particle reinforcement and aluminum matrix. The volume fraction of silicon carbide particle reinforcement is 5% to 30%, and the remaining part is aluminum matrix. The SiC / aluminum matrix composite material substrate is butt-jointed, and under an argon atmosphere, the welding filler material is laser-welded to the SiC / aluminum matrix composite material substrate using a defocusing laser filler method. The particle size of SiC particles is 5 to 15 μm. Utilizing the Gaussian distribution of laser energy along the beam diameter, with high energy density at the center and low energy density off-center, the ratio of laser energy absorbed by the filler and base material is controlled by adjusting the defocus distance, laser power, and laser scanning rate. This reduces the laser energy absorbed by the base material during welding, hindering the chemical reaction between the reinforcement and the matrix, thereby eliminating brittle phases in the weld joint and achieving high-strength welding of composite materials. The process parameters for defocus laser filler welding are: laser defocus distance of 30mm to 90mm, laser welding power of 500W to 1200W, and laser scanning rate of 3mm / s to 30mm / s. In this method, SiC does not react with the aluminum matrix in the weld joint, resulting in a composite material weld joint free of Al4C3 and AlSiC brittle phases. During the welding process of SiC / aluminum-based composite material plates, the welding filler is aluminum alloy or its composite material powder or wire. The filler is fed by coaxial powder or wire feeding, and the coaxial feeding rate is 3 to 25 g / min. The particle size of the laser welding filler powder is 150-300 mesh, and the diameter of the laser welding filler wire is 3-10 mm.

2. The laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution according to claim 1, characterized in that, Before performing defocused laser filler welding, the selected SiC / aluminum-based composite material plate is ground to remove the oxide layer.

3. The laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution according to claim 1, characterized in that, Laser filler welding using the defocusing method is implemented by adjusting the defocus distance of the laser working spot, laser power, laser scanning rate, and filler composition parameters.

4. The laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution according to claim 3, characterized in that, Welding was performed by adjusting the laser working spot defocus distance, laser power, laser scanning rate, and filler composition parameters using a method that controls a single variable.

5. The laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution according to claim 1, characterized in that, The SiC / aluminum-based composite material base material thickness is 0.1mm to 4mm, and a V-shaped groove is opened at the part to be welded with a groove angle of 15° to 90°. The volume purity of the argon protective atmosphere for welding is ≥99.9%.

6. The laser filler welding method for SiC / aluminum-based composite materials based on energy redistribution according to claim 5, characterized in that, Before laser welding, the V-groove is ground, cleaned and dried. The cleaning agent is an ethanol solution with a concentration of 94-98 wt%.

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