Laser welding method of TC4 titanium alloy and carbon fiber reinforced composite material

Abstract

The application discloses a laser welding method of TC4 titanium alloy and carbon fiber reinforced composite material, and relates to the field of laser welding of dissimilar materials. The application first performs surface modification on the carbon fiber by using hydrogen peroxide, deepens the surface oxidation depth through microwave radiation, peels off the graphene oxide on the surface through ultrasonic treatment, and then performs impact treatment through plasma beam treatment to increase and expand the grooves and pores on the surface of the carbon fiber, so that the active groups and the concave-convex structure on the surface of the modified carbon fiber are filled and solidified by the resin; secondly, a layer of nano nickel is first deposited on the micro-textured surface of the titanium alloy to reduce the penetration and corrosion of the modified carbon nanotube on the titanium alloy, and then the carbon nanotube after acid treatment is deposited on the surface layer of the nano nickel through electrophoretic deposition technology to improve the interface wetting and spreading capacity and reduce the residual stress after welding. The application combines the TC4 titanium alloy, the nano nickel deposition layer, the modified carbon nanotube deposition layer and the modified carbon fiber composite material layer, and is connected through laser welding to realize the effect of high-strength connection.

Description

Technical Field

[0001] This invention relates to the field of laser welding of dissimilar materials, specifically a laser welding method for TC4 titanium alloy and carbon fiber reinforced composite materials. Background Technology

[0002] Carbon fiber reinforced polymer (CFRP) is a novel lightweight material with high specific strength, high modulus, and low linear expansion coefficient. It is already being used in key national sectors such as aerospace and military products, and is gradually becoming a mainstream application in civilian fields such as building repair, Formula 1 racing, racing boats, and sporting goods. CFRP exhibits significant weight reduction in automotive structural components, while also demonstrating good impact resistance and energy absorption capabilities. However, CFRP suffers from high production costs, complex manufacturing processes, and low fracture toughness. Currently, the preferred approach is to combine it with metallic materials to form composite structures, effectively leveraging the respective advantages of both materials.

[0003] Titanium alloy is a high-strength, low-density, corrosion-resistant, and high-temperature-resistant high-quality alloy. It has begun to be widely used in various special environments, such as aerospace, military aircraft, and large ships. It is an important material for manufacturing aero engines, rockets, and high-speed aircraft.

[0004] Laser welding is a precision welding method characterized by low heat source, high precision, high welding speed, and high energy density. Laser welding of titanium alloys and carbon fiber reinforced polymer (CFRP) achieves a connection by locally melting and solidifying the titanium alloy and CFRP through laser heat conduction. However, the significant differences in thermophysical properties between titanium alloys and CFRP result in substantial residual stress near the weld joint, reducing the connection strength. Surface treatment of the titanium alloy is a primary measure to improve the connection strength of the titanium alloy-CFRP joint. Surface treatment methods for titanium alloy plates can be categorized into three types: mechanical treatments such as sandblasting and shot peening; chemical treatments such as anodizing of the titanium alloy surface; and adding a bonding interface layer such as plasma spraying. While all these methods can improve the connection strength between titanium alloys and CFRP, they all have limitations. They cannot resolve the significant residual stress and poor interfacial wetting and spreading caused by the differences in thermophysical properties between titanium alloys and CFRP, and the processes are complex and cumbersome. Therefore, a highly efficient, rapid, and stable method is needed to reduce the residual stress in titanium alloy-CFRP welding. Based on this, this invention proposes a novel laser welding method for TC4 titanium alloy and carbon fiber reinforced polymer (CFRP) composites. Summary of the Invention

[0005] The purpose of this invention is to provide a laser welding method for TC4 titanium alloy and carbon fiber reinforced composite materials to solve the problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the present invention provides the following technical solution: a laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material, comprising the following preparation steps:

[0007] (1) T700 carbon fiber bundles with 24K warp and weft yarns were immersed in hydrogen peroxide for modification. The mixture was sealed and placed in a vacuum drying oven and reacted at 80-120℃ for 10 min. After the reaction, the mixture was cooled to room temperature, filtered to obtain solid, and washed with deionized water 3 times to remove residue, thus obtaining oxidized carbon fiber. The oxidized carbon fiber was then immersed in distilled water and subjected to microwave radiation. The microwave radiation conditions were set to 2.45 GHz, 600 W, and 60-200 s. After the treatment, the mixture was cooled to room temperature and then sonicated at 40-60 kHz for 30-60 min. After the sonication, the solid was washed with deionized water 3 times and then dried in a drying oven at 50℃ for 6 h. Finally, the dried carbon fiber was subjected to plasma treatment with a power of 100-140 W and a time of 10-60 s, using H2O as the plasma. After the treatment, the modified carbon fiber was obtained.

[0008] (2) Mix 3-4 parts of dimethylformamide, 2-4 parts of ethyl acetate, 4-5 parts of polyamide, and 0.1-0.5 parts of surfactant, and stir at 60 rpm for 10 min to prepare a sizing solution; apply the sizing solution evenly to the surface of the modified carbon fiber, and dry it after coating at 120℃ for 1 min; repeat the above operation after the first sizing to perform a second sizing until the volume ratio of the outer resin to the inner carbon fiber is 1:1-1.2, and then cure at 120℃ for 5 h. After curing, the carbon fiber composite material is obtained.

[0009] (3) Using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, rows of strip-shaped microtextures were prepared on the surface of a TC4 titanium alloy plate. Each microtexture was spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate was used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The decontaminated titanium alloy plate was then electroless nickel plated at a rate of 1-3dm / L of plating solution. 2 The nickel-plated titanium alloy plate was prepared by mixing the proportions and plating time of 1 hour. Finally, the carbon nanotube layer on the nickel layer surface was obtained by electrophoretic deposition in a carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 minutes. The deposited titanium alloy plate was then joined together with carbon fiber composite material and laser welded to obtain a titanium alloy and carbon fiber reinforced composite material.

[0010] Furthermore, the concentration of hydrogen peroxide in step (1) is 1-3%.

[0011] Furthermore, in step (1), the solid-liquid ratio of the carbon fiber bundle plain weave to hydrogen peroxide is 1:3.

[0012] Furthermore, in step (1), the solid-liquid ratio of the oxidized carbon fiber and distilled water is 1:3.

[0013] Furthermore, the plasma treatment in step (1) is pulsed plasma treatment.

[0014] Furthermore, the surfactant in step (2) is Tween 60.

[0015] Furthermore, in step (2), the sizing speed is 1 m / min.

[0016] Furthermore, the composition of the plating solution in step (3) is as follows: 2.5-3.0% NiSO4·6H2O, 3-3.4% NaH2PO2·H2O, 1.3-1.7% NaAC·3H2O, 2.6-3.0% C3H6O3, 0.01% Pb2+, with the remainder being deionized water, and the temperature is 90℃.

[0017] Furthermore, the carbon nanotube suspension preparation method in step (3) is as follows: the carbon nanotubes are acid-treated by acidifying them with a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80°C for 2 hours; the mixture is washed with deionized water until neutral, then vacuum filtered with a microporous membrane with a pore size of 0.45 μm, and then freeze-dried at -40°C for 2 hours to obtain carboxylic acid functionalized carbon nanotubes; finally, a suspension of 1 mg / mL is prepared by dispersing the carbon nanotubes in ethanol, and 0.01-0.15 times the mass of Mg(NO3)2·6H2O is added to improve the conductivity of the suspension.

[0018] Furthermore, the laser welding parameters in step (3) are 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 m spot diameter.

[0019] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0020] This invention combines TC4 titanium alloy, a nano-nickel deposition layer, a modified carbon nanotube deposition layer, and a modified carbon fiber composite material layer, and connects them by laser welding to achieve a high-strength connection.

[0021] First, hydrogen peroxide is used to modify the surface of carbon fibers. After the hydrogen peroxide decomposes, hydroxyl radicals and oxygen radicals react with the carbon fibers to oxidize them, and then the fibers are peeled off and etched to prepare carbon fibers with graphene oxide on the surface. Then, microwave radiation is used to further deepen the surface oxidation of the carbon fibers and peel off the poorly attached graphene oxide. Then, by controlling the conditions of ultrasonic treatment, the outermost graphene oxide is partially peeled off. After plasma beam treatment, the large and closely packed graphite crystals in the carbon fiber skin are further broken, increasing and expanding the grooves and pores on the carbon fiber surface. This allows the active groups and uneven structures on the modified carbon fiber surface to complement each other after the resin is filled and cured, resulting in higher bonding strength and thus improving the strength of the carbon fiber composite material.

[0022] Secondly, a layer of nano-nickel is first chemically deposited onto the surface of the titanium alloy microtexture, and then acid-treated carbon nanotubes are deposited on the surface of the nano-nickel using electrophoretic deposition. The carboxyl atoms at the edges of the modified carbon nanotubes are replaced by nickel, forming a dipole moment, which improves the interfacial wetting and spreading ability and reduces the residual stress after welding the titanium alloy and carbon fiber composite. The nano-nickel reacts and combines with titanium metal at high temperature to form an alloy at the contact surface, which reduces the penetration and corrosion of the titanium alloy by the modified carbon nanotubes, improves the interlayer toughness of the composite material, and forms a multifunctional intercalated self-supporting structure. Finally, the treated titanium alloy and carbon fiber reinforced composite are welded together by laser, and a microtexture is prepared on the surface of the titanium alloy to increase the mechanical interlocking force between the titanium alloy and the carbon fiber composite and improve the connection strength. Detailed Implementation

[0023] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0024] To more clearly illustrate the method provided by the present invention, the following embodiments are provided in detail. The following embodiments describe a method for testing various properties of a TC4 titanium alloy and carbon fiber reinforced composite material:

[0025] Connection strength: Select size 50×30×4mm 3 The embodiments and comparative examples were tested for stress using a universal testing machine. Each embodiment and comparative example was tested three times, and the average value of the results was taken as the connection strength of the sample.

[0026] Example 1; (1) T700 carbon fiber bundle plain weave with warp and weft yarns both being 24K was immersed in 1% hydrogen peroxide for modification, and the solid-liquid ratio of carbon fiber bundle plain weave to hydrogen peroxide was 1:3; the above mixture was sealed and placed in a vacuum drying oven and reacted at 80°C for 10 min; after the reaction was completed, it was cooled to room temperature, the mixture was filtered to obtain solid, and washed 3 times with deionized water to remove residue, thus obtaining oxidized carbon fiber; the oxidized carbon fiber was then immersed in distilled water, and the oxidized carbon fiber was further processed. The solid-liquid ratio of fiber and distilled water was 1:3, and microwave irradiation was performed. The microwave irradiation conditions were set to 2.45 GHz, 600 W, and a treatment time of 60 s. After treatment, the fiber was cooled to room temperature and then sonicated at 40 kHz for 30 min. After sonication, the solid was washed three times with deionized water and then dried in a drying oven at 50 ℃ for 6 h. Finally, the dried carbon fiber was subjected to iso-pulse plasma treatment at a power of 100 W for 10 s using H2O as the plasma. Modified carbon fiber was obtained after the treatment.

[0027] (2) Mix 3 parts dimethylformamide, 2 parts ethyl acetate, 4 parts polyamide, and 0.1 parts Tween 60 and stir at 60 rpm for 10 min to prepare a sizing solution; apply the sizing solution evenly to the surface of the prepared modified carbon fiber at a sizing speed of 1 m / min. After the application is completed, dry the material at 120°C for 1 min. Repeat the above operation after the first sizing to perform a second sizing until the volume ratio of the outer resin to the inner carbon fiber is 1:1. Then cure at 120°C for 5 h. After curing, the carbon fiber composite material is obtained.

[0028] (3) Using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, rows of strip-shaped microtextures were prepared on the surface of a TC4 titanium alloy plate. Each microtexture was spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate was used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The decontaminated titanium alloy plate was then electroless nickel plated at a rate of 1 dm / L of plating solution. 2The plating solution was prepared with the following composition: 2.5% NiSO4·6H2O, 3% NaH2PO2·H2O, 1.3% NaAC·3H2O, 2.6% C3H6O3, 0.01% Pb2+, and the remainder being deionized water. The temperature was 90℃, and the plating time was 1 hour, resulting in a nickel-titanium alloy plate. Carbon nanotubes were then acid-treated by using a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80℃ for 2 hours. The mixture was washed with deionized water until neutral, then vacuum filtered through a 0.45μm microporous membrane, and finally freeze-dried at -40℃ for 2 hours to obtain carboxylic acid-functionalized carbon nanotubes. Finally, the carbon nanotubes were further processed... Carbon nanotubes were dispersed in ethanol to prepare a 1 mg / mL suspension. Simultaneously, 0.01 times the mass of Mg(NO3)2·6H2O was added to improve the conductivity of the suspension, thus preparing a carbon nanotube suspension. Finally, a carbon nanotube layer on the nickel layer surface was obtained by electrophoretic deposition in the carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 min. The deposited titanium alloy plate was then joined with a carbon fiber composite material and laser-welded using parameters of 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 μm spot diameter to obtain a titanium alloy and carbon fiber reinforced composite material.

[0029] Example 2; (1) T700 carbon fiber bundle plain weave with warp and weft yarns both being 24K was immersed in 2% hydrogen peroxide for modification, and the solid-liquid ratio of carbon fiber bundle plain weave to hydrogen peroxide was 1:3; the above mixture was sealed and placed in a vacuum drying oven and reacted at 100°C for 10 min; after the reaction was completed, it was cooled to room temperature, the mixture was filtered to obtain solid, and washed 3 times with deionized water to remove residue, thus obtaining oxidized carbon fiber; the oxidized carbon fiber was then immersed in distilled water, and the oxidized carbon fiber was further processed. The solid-liquid ratio of fiber and distilled water was 1:3, and microwave irradiation was performed. The microwave irradiation conditions were set to 2.45 GHz, 600 W, and a treatment time of 130 s. After treatment, the fiber was cooled to room temperature and then sonicated at 50 kHz for 45 min. After sonication, the solid was washed three times with deionized water and then dried in a drying oven at 50 ℃ for 6 h. Finally, the dried carbon fiber was subjected to isopulse plasma treatment at a power of 120 W for 35 s using H2O as the plasma. Modified carbon fiber was obtained after the treatment.

[0030] (2) Mix 3.5 parts dimethylformamide, 3 parts ethyl acetate, 4.5 parts polyamide, and 0.3 parts Tween 60, and stir at 60 rpm for 10 min to prepare a sizing solution; apply the sizing solution evenly to the surface of the modified carbon fiber at a sizing speed of 1 m / min, and dry it after application at 120℃ for 1 min; repeat the above operation after the first sizing to perform a second sizing until the volume ratio of the outer resin to the inner carbon fiber is 1:1.1, and then cure at 120℃ for 5 h. After curing, the carbon fiber composite material is obtained.

[0031] (3) Using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, rows of strip-shaped microtextures were prepared on the surface of a TC4 titanium alloy plate. Each microtexture was spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate was used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The decontaminated titanium alloy plate was then electroless nickel plated at a rate of 2dm / L of plating solution. 2 The plating solution was prepared with the following composition: 2.75% NiSO4·6H2O, 3.2% NaH2PO2·H2O, 1.5% NaAC·3H2O, 2.8% C3H6O3, 0.01% Pb2+, and the remainder being deionized water. The temperature was 90℃, and the plating time was 1 hour, resulting in a nickel-titanium alloy plate. The carbon nanotubes were then acidified using a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80℃ for 2 hours. After washing the mixture with deionized water until neutral, it was vacuum filtered through a microporous membrane with a pore size of 0.45 μm, and then freeze-dried at -40℃ for 2 hours to obtain carboxylic acid-functionalized carbon nanotubes. Finally... A 1 mg / mL suspension of carbon nanotubes was prepared by dispersing carbon nanotubes in ethanol, and 0.08 times the mass of Mg(NO3)2·6H2O was added to improve the conductivity of the suspension. Finally, a carbon nanotube layer on the nickel surface was obtained by electrophoretic deposition in the carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 min. The deposited titanium alloy plate was then joined with a carbon fiber composite material and laser-welded using parameters of 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 μm spot diameter to obtain a titanium alloy and carbon fiber reinforced composite material.

[0032] Example 3; (1) T700 carbon fiber bundle plain weave with both warp and weft yarns of 24K was immersed in 3% hydrogen peroxide for modification, and the solid-liquid ratio of carbon fiber bundle plain weave to hydrogen peroxide was 1:3; the above mixture was sealed and placed in a vacuum drying oven and reacted at 120°C for 10 min; after the reaction was completed, it was cooled to room temperature, the mixture was filtered to obtain solid, and washed 3 times with deionized water to remove residue, thus obtaining oxidized carbon fiber; the oxidized carbon fiber was then immersed in distilled water, and the oxidized carbon fiber was further processed. The solid-liquid ratio of fiber and distilled water was 1:3, and microwave irradiation was performed. The microwave irradiation conditions were set to 2.45 GHz, 600 W, and a treatment time of 200 s. After treatment, the fiber was cooled to room temperature and then sonicated at 60 kHz for 60 min. After sonication, the solid was washed three times with deionized water and then dried in a drying oven at 50 ℃ for 6 h. Finally, the dried carbon fiber was subjected to iso-pulse plasma treatment at a power of 140 W for 60 s using H2O as the plasma. Modified carbon fiber was obtained after the treatment.

[0033] (2) Mix 4 parts dimethylformamide, 4 parts ethyl acetate, 5 parts polyamide, and 0.5 parts Tween 60 and stir at 60 rpm for 10 min to prepare a sizing solution; apply the sizing solution evenly to the surface of the modified carbon fiber at a sizing speed of 1 m / min. After the application is completed, dry the material at 120°C for 1 min. Repeat the above operation after the first sizing to perform a second sizing until the volume ratio of the outer resin to the inner carbon fiber is 1:1.2. Then cure at 120°C for 5 h. After curing, the carbon fiber composite material is obtained.

[0034] (3) Using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, rows of strip-shaped microtextures were prepared on the surface of a TC4 titanium alloy plate. Each microtexture was spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate was used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The decontaminated titanium alloy plate was then electroless nickel plated at a rate of 3dm / L of plating solution. 2The plating solution was prepared with the following composition: 3.0% NiSO4·6H2O, 3.4% NaH2PO2·H2O, 1.7% NaAC·3H2O, 3.0% C3H6O3, 0.01% Pb2+, and the remainder being deionized water. The temperature was 90℃, and the plating time was 1 hour, resulting in a nickel-titanium alloy plate. Carbon nanotubes were then acidified using a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80℃ for 2 hours. The mixture was washed with deionized water until neutral, then vacuum filtered through a 0.45μm microporous membrane, and finally freeze-dried at -40℃ for 2 hours to obtain carboxylic acid-functionalized carbon nanotubes. Finally, the mixture was... A 1 mg / mL suspension of carbon nanotubes was prepared by dispersing carbon nanotubes in ethanol, and 0.15 times the mass of Mg(NO3)2·6H2O was added to improve the conductivity of the suspension. Finally, a carbon nanotube layer on the nickel layer surface was obtained by electrophoretic deposition of the carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 min. The deposited titanium alloy plate was then joined with a carbon fiber composite material and laser-welded using parameters of 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 μm spot diameter to obtain a titanium alloy and carbon fiber reinforced composite material.

[0035] Comparative Example 1; The difference between Comparative Example 1 and Example 2 lies in the different step (1). Step (1) is changed to: immersing plain weave carbon fiber bundles of T700 with 24K warp and weft yarns in distilled water, with a solid-liquid ratio of carbon fiber to distilled water of 1:3, and subjecting them to microwave radiation; the microwave radiation conditions are set to 2.45 GHz, 600 W, and a treatment time of 130 s; after treatment, cooling to room temperature, and then sonicating at 50 kHz for 45 min; after sonication, the solid is taken and washed three times with deionized water, and then dried in a drying oven at 50 ℃ for 6 h; finally, the dried carbon fiber is subjected to iso-pulse plasma treatment with a power of 120 W and a time of 35 s, using H2O as the plasma, and modified carbon fiber is obtained after treatment; the remaining steps are the same as in Example 2.

[0036] Comparative Example 2; The difference between Comparative Example 2 and Example 2 lies in step (1). Step (1) is changed to: T700 carbon fiber bundle plain weave with warp and weft yarns of 24K is immersed in 2% hydrogen peroxide for modification, and the solid-liquid ratio of carbon fiber bundle plain weave to hydrogen peroxide is 1:3; the above mixture is sealed and placed in a vacuum drying oven and reacted at 100℃ for 10 min; after the reaction, it is cooled to room temperature, the mixture is filtered to obtain solid, and washed with deionized water 3 times to remove residue, thus obtaining oxidized carbon fiber; the oxidized carbon fiber is then immersed in distilled water, and the solid-liquid ratio of oxidized carbon fiber to distilled water is 1:3, and sonicated at 50kHz for 45 min; after sonication, the solid is taken and washed with deionized water 3 times, and then dried in a drying oven at 50℃ for 6 h; finally, the dried carbon fiber is subjected to iso-pulse plasma treatment with a power of 120W for 35s, and the plasma is H2O. After the treatment, modified carbon fiber is obtained; the remaining steps are the same as in Example 2.

[0037] Comparative Example 3; The difference between Comparative Example 3 and Example 2 lies in step (1). Step (1) is changed to: immersing plain weave carbon fiber bundles of T700 with 24K warp and weft yarns in 2% hydrogen peroxide for modification, with a solid-liquid ratio of 1:3 between the plain weave carbon fiber bundles and hydrogen peroxide; sealing the above mixture and placing it in a vacuum drying oven, reacting at 100°C for 10 minutes; after the reaction, cooling to room temperature, filtering the mixture to obtain the solid, and washing it three times with deionized water to remove residue, thus obtaining oxidized carbon fiber; then... The oxidized carbon fiber was immersed in distilled water with a solid-liquid ratio of 1:3 and subjected to microwave irradiation. The microwave irradiation conditions were set to 2.45 GHz, 600 W, and a treatment time of 130 s. After treatment, the carbon fiber was cooled to room temperature, and the solid was washed three times with deionized water and then dried in a drying oven at 50 ℃ for 6 h. Finally, the dried carbon fiber was subjected to iso-pulse plasma treatment with a power of 120 W and a time of 35 s using H2O as the plasma. After treatment, modified carbon fiber was obtained. The remaining steps were the same as in Example 2.

[0038] Comparative Example 4; The difference between Comparative Example 4 and Example 2 lies in step (1). Step (1) is changed to: T700 carbon fiber tow plain weave with warp and weft yarns of 24K is immersed in 2% hydrogen peroxide for modification, and the solid-liquid ratio of carbon fiber to hydrogen peroxide is 1:3; the above mixture is sealed and placed in a vacuum drying oven and reacted at 100°C for 10 min; after the reaction, it is cooled to room temperature, the mixture is filtered to obtain solid, and washed with deionized water 3 times to remove residue, thus obtaining oxidized carbon fiber; the oxidized carbon fiber is then immersed in distilled water, and the solid-liquid ratio of oxidized carbon fiber to distilled water is 1:3, and microwave radiation is performed; the microwave radiation conditions are set to 2.45 GHz, 600 W, and the treatment time is 130 s; after the treatment, it is cooled to room temperature and then sonicated at 50 kHz for 45 min; after the sonication, the solid is taken and washed with deionized water 3 times, and then dried in a drying oven at 50°C for 6 h, thus obtaining modified carbon fiber; the remaining steps are the same as in Example 2.

[0039] Comparative Example 5; The difference between Comparative Example 5 and Example 2 lies in step (3). Step (3) is changed to: using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, a row of strip-shaped microtextures are prepared on the surface of a TC4 titanium alloy plate. Each microtexture is spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate is used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The carbon nanotubes are acid-treated by acidifying them with a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80°C for 2 hours. The mixture is washed with deionized water until neutral and then vacuum filtered through a microporous membrane with a pore size of 0.45μm. Carboxylic acid-functionalized carbon nanotubes were obtained by freeze-drying at -40℃ for 2 hours. A 1 mg / mL suspension was prepared by dispersing the carbon nanotubes in ethanol, and 0.08 times the mass of Mg(NO3)2·6H2O was added to increase the conductivity of the suspension, thus preparing a carbon nanotube suspension. Finally, the carbon nanotube layer on the surface of the decontaminated titanium alloy plate was obtained by electrophoretic deposition in a carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 minutes. The deposited titanium alloy plate was then joined with a carbon fiber composite material and laser-welded using parameters of 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 μm spot diameter to obtain a titanium alloy and carbon fiber reinforced composite material. The remaining steps were the same as in Example 2.

[0040] Example of effect

[0041] Table 1 below shows the performance analysis results of a TC4 titanium alloy and carbon fiber reinforced composite material using Examples 1 to 3 and Comparative Examples 1 to 5 of the present invention.

[0042] Table 1

[0043] Connection strength / MPa Example 1 18.02 Example 2 18.02 Example 3 18.00 Comparative Example 1 15.33 Comparative Example 2 16.20 Comparative Example 3 16.38 Comparative Example 4 15.81 Comparative Example 5 14.62

[0044] A comparison of the wear resistance experimental data from the examples and comparative examples reveals that this invention utilizes hydrogen peroxide to modify the surface of excessively thick carbon fibers. The hydroxyl and oxygen free radicals resulting from the decomposition of hydrogen peroxide react with the carbon fibers in an oxidative reaction, followed by peeling and etching to prepare carbon fibers with graphene oxide on the surface. Microwave radiation further deepens the surface oxidation of the carbon fibers, simultaneously peeling off loosely attached graphene oxide. Then, by controlling the conditions of ultrasonic treatment, the outermost graphene oxide is partially peeled off. Plasma beam treatment further breaks down the large, tightly packed graphite crystals in the carbon fiber skin, increasing and expanding the grooves and pores on the carbon fiber surface. This allows the active groups and uneven structures on the modified carbon fiber surface to complement each other through physical interlocking and chemical bonding after subsequent resin filling and curing, achieving higher bonding strength and thus improving the strength of the carbon fiber composite material. Secondly, this invention first chemically deposits a layer of nano-nickel onto the surface of the titanium alloy microtexture, and then uses electrophoretic deposition to deposit acid-treated carbon nanotubes onto the surface of the nano-nickel. The carboxyl matrix molecules at the edges of the modified carbon nanotubes are replaced by nickel, forming a dipole moment, which improves the interfacial wetting and spreading ability and reduces the residual stress after welding the titanium alloy and carbon fiber composite. The nano-nickel reacts and combines with titanium metal at high temperature to form an alloy at the contact surface, which reduces the penetration and corrosion of the titanium alloy by the modified carbon nanotubes, improves the interlayer toughness of the composite material, and forms a multifunctional intercalated self-supporting structure. Finally, the treated titanium alloy and carbon fiber reinforced composite are welded together by laser, and a microtexture is prepared on the surface of the titanium alloy to increase the mechanical interlocking force between the titanium alloy and the carbon fiber composite, thereby improving the connection strength.

[0045] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No markings in the claims should be construed as limiting the scope of the claims.

Claims

1. A laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material, characterized in that, The preparation steps include the following: (1) T700 carbon fiber bundles with 24K warp and weft yarns were immersed in hydrogen peroxide for modification. The mixture was sealed and placed in a vacuum drying oven and reacted at 80-120℃ for 10 min. After the reaction, the mixture was cooled to room temperature, filtered to obtain solid, and washed with deionized water 3 times to remove residue, thus obtaining oxidized carbon fiber. The oxidized carbon fiber was then immersed in distilled water and subjected to microwave radiation. The microwave radiation conditions were set to 2.45 GHz, 600 W, and 60-200 s. After the treatment, the mixture was cooled to room temperature and then sonicated at 40-60 kHz for 30-60 min. After the sonication, the solid was washed with deionized water 3 times and then dried in a drying oven at 50℃ for 6 h. Finally, the dried carbon fiber was subjected to plasma treatment with a power of 100-140 W and a time of 10-60 s, using H2O as the plasma. After the treatment, the modified carbon fiber was obtained. (2) Mix 3-4 parts of dimethylformamide, 2-4 parts of ethyl acetate, 4-5 parts of polyamide, and 0.1-0.5 parts of surfactant, and stir at 60 rpm for 10 min to prepare a sizing solution; apply the sizing solution evenly to the surface of the modified carbon fiber, and dry it after coating at 120℃ for 1 min; repeat the above operation after the first sizing to perform a second sizing until the volume ratio of the outer resin to the inner carbon fiber is 1:1-1.2, and then cure at 120℃ for 5 h. After curing, the carbon fiber composite material is obtained. (3) Using a 1030nm nanosecond pulsed fiber laser with a beam diameter of 30μm, a laser power of 70W, and a scanning speed of 700mm / s, rows of strip-shaped microtextures were prepared on the surface of a TC4 titanium alloy plate. Each microtexture was spaced 100μm apart, with a width of 100μm and a depth of 100μm. The titanium alloy plate was used as two electrodes and placed in acetone / ethanol (v / v = 1:1) to remove surface contaminants. The decontaminated titanium alloy plate was then electroless nickel plated at a rate of 1-3dm / L of plating solution. 2 The nickel-plated titanium alloy plate was prepared by mixing the proportions and plating time of 1 hour. Finally, the carbon nanotube layer on the nickel layer surface was obtained by electrophoretic deposition in a carbon nanotube suspension at a working distance of 15 mm between two electrodes and a working voltage of 50 V for 5 minutes. The deposited titanium alloy plate was then joined together with carbon fiber composite material and laser welded to obtain a titanium alloy and carbon fiber reinforced composite material.

2. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The concentration of hydrogen peroxide in step (1) is 1-3%.

3. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, In step (1), the solid-liquid ratio of the plain weave of the carbon fiber bundle to hydrogen peroxide is 1:

3.

4. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, In step (1), the solid-liquid ratio of the oxidized carbon fiber and distilled water is 1:

3.

5. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The plasma treatment method in step (1) is pulsed plasma treatment.

6. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The surfactant used in step (2) is Tween 60.

7. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The sizing speed in step (2) is 1 m / min.

8. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The composition of the plating solution in step (3) is as follows: 2.5-3.0% NiSO4·6H2O, 3-3.4% NaH2PO2·H2O, 1.3-1.7% NaAC·3H2O, 2.6-3.0% C3H6O3, 0.01% Pb2+, with the remainder being deionized water, and the temperature is 90℃.

9. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The method for preparing the carbon nanotube suspension in step (3) is as follows: the carbon nanotubes are acid-treated by acidifying them with a mixed solution of HNO3 / H2SO4 (v / v = 1:3) at 80°C for 2 hours; the mixture is washed with deionized water until neutral, then vacuum filtered through a microporous membrane with a pore size of 0.45 μm, and then freeze-dried at -40°C for 2 hours to obtain carboxylic acid functionalized carbon nanotubes; finally, a suspension of 1 mg / mL is prepared by dispersing the carbon nanotubes in ethanol, and 0.01-0.15 times the mass of Mg(NO3)2·6H2O is added to improve the conductivity of the suspension.

10. The laser welding method for TC4 titanium alloy and carbon fiber reinforced composite material according to claim 1, characterized in that, The laser welding parameters in step (3) are 0.6 kW laser power, 0.8 m / min scanning speed, and 0.95 m spot diameter.