Method for ultrafast laser welding of ceramic reinforced aluminum-based composite material in vacuum environment

Abstract

The invention discloses a method for ultrafast laser welding of a ceramic reinforced aluminum-based composite material in a vacuum environment, and aims to solve the problems that high-precision welding and micro-area welding are difficult to realize by a traditional connection method of the existing ceramic reinforced aluminum-based composite material, the strength of a joint is limited by an ultrafast laser welding method, the thickness of a weldable workpiece is limited and the like. The ultrafast laser welding method in the vacuum environment comprises the steps that firstly, a to-be-connected face is ground and polished; secondly, the to-be-welded parts are assembled in a butt joint mode and placed in a vacuum cabin; 3, vacuumizing the vacuum chamber; and fourthly, ultrafast laser is aligned with the weld joint, the laser pulse width is controlled to be 200 fs to 10 ps, the laser power is 10 W to 120 W, the welding speed is 0.03 mm / s to 5 mm / s, and ultrafast laser welding is conducted. The obtained connector is almost free of welding deformation, the bending strength reaches 80% of that of base metal, high-precision welding and micro-area welding are achieved, meanwhile, the welding penetration depth can be effectively increased through the vacuum environment, and the thickness size range of weldable workpieces is enlarged.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of metal matrix composite connection, and particularly relates to a method for ultrafast laser welding of ceramic reinforced aluminum matrix composite in a vacuum environment. BACKGROUND

[0002] The ceramic reinforced aluminum matrix composite is a kind of composite material prepared by adding ceramic such as SiC, B4C or TiC as a reinforcing phase to an aluminum alloy as a matrix. Compared with single aluminum alloy, the ceramic reinforced aluminum matrix composite has higher specific strength, specific stiffness, higher thermal conductivity, better wear resistance, corrosion resistance and thermal stability, and has incomparable comprehensive performance of single metal or ceramic material, and shows broad application prospects in many fields such as aerospace, automobile and electronic devices. However, for the ceramic reinforced aluminum matrix composite with high content of reinforcing phase, its mechanical processing is difficult, and the one-piece forming process is often difficult to manufacture a complex structural member that can be directly put into application. Therefore, in actual engineering, it is usually necessary to connect the simply shaped basic parts into an integral member through a welding process. In addition, welding is also an indispensable process link in the subsequent maintenance and repair process. As can be seen, the development of a reliable welding technology is of key significance to promote the engineering application of the ceramic reinforced aluminum matrix composite.

[0003] The commonly used welding methods for ceramic reinforced aluminum matrix composites include traditional fusion welding, brazing and friction stir welding. Traditional fusion welding has a large heat input, and brittle phases are often generated in the weld, which affects the mechanical properties of the joint. In 2000, A. Urena et al. (A. Urena, M. D. Escalera, L. Gil. Influence of interface reactions on fracture mechanisms in TIG arc-welded aluminium matrix composites [J]. Composites Science and Technology, 2000, 60(4): 613-22.) used TIG welding to weld SiC reinforced aluminum matrix composites. It was found that the SiC reinforcement would react with the aluminum matrix to form large-sized Al4C3 brittle phase during welding, which seriously damaged the joint strength. With the increase of SiC reinforcement content, the joint strength gradually decreased, and the tensile strength of the welded joint of aluminum matrix composite with 20% SiC volume fraction was only 137 MPa, which was less than 45% of the strength of the base material. At the same time, the size of the traditional fusion welding weld and heat affected zone is large, and the welding deformation is large, which cannot meet the requirements of high-precision welding and micro-welding. Brazing can well avoid the reaction between the reinforcement and the matrix, but the limitations of the filler metal often make the brazing seam become the weak link of the joint, and the obtained joint strength is low. Guojing Xu team (G. Xu, X. Ma, W. Du, P. Zhao, Y. Xia, Z. Li, et al. Ultrasonic-assisted soldering of SiC p / Al metal matrix composites using Sn-Ag-Cu-Al solder at low temperatures. Composites Part A2025;197:109056.) used ultrasonic-assisted welding to realize the welding of 55vol% SiC pThe welding of / Al composite material, under the action of ultrasonic waves, the oxide film of Al matrix is destroyed, and the filler metal and Al matrix and SiC reinforcing phase form good metallurgical bonding, but the optimal joint shear strength is only 51.6MPa. Qiao Qi et al. (Q. Qiao, Y. Su, Q. Ouyang, D. Zhang, X. Song, L. Guo. Microstructural characterization and mechanical properties of 120-mm ultra-thick SiCp / Al composite plates joined by double-sided friction stir welding. Metallurgical and Materials Transactions A, 2019; 50: 3589-602.) realized the welding of 16vol%SiCp / 2014Al by friction stir welding, and obtained a joint with strength comparable to the base material. However, due to the high hardness of the SiC ceramic reinforcing phase, the stir pin is severely worn during welding, limiting the service life of the stir pin, so it is difficult to realize long continuous welds, and it also restricts its application in the welding of composite materials with higher volume fraction of reinforcing phase.

[0004] The patent entitled "A method for ultrafast laser welding of ceramic reinforced aluminum matrix composite" (application number: CN202511049967.3) discloses a method suitable for high-precision welding and micro-area welding of ceramic reinforced aluminum matrix composite. However, aluminum is very active in chemical properties and is easily oxidized in atmospheric conditions, resulting in uneven weld structure and adversely affecting the mechanical properties of the joint. The joint strength obtained is still limited. In addition, the workpiece thickness size that can be welded by this method under atmospheric conditions is small. SUMMARY

[0005] The purpose of the present application is to solve the problems of existing ceramic reinforced aluminum matrix composite traditional connection methods, such as difficulty in realizing high-precision welding and micro-area welding, limited joint strength of ultrafast laser welding method, and limited weldable workpiece thickness size, and to provide a method for ultrafast laser welding of ceramic reinforced aluminum matrix composite in a vacuum environment.

[0006] The method for ultrafast laser welding of ceramic reinforced aluminum matrix composite in a vacuum environment according to the present application is realized according to the following steps:

[0007] Step one, polish and polish the surface to be connected of the ceramic reinforced aluminum matrix composite, and obtain the workpiece to be welded after ultrasonic cleaning;

[0008] Step two, butt joint assembly of the to-be-welded parts is carried out, clamping is carried out by using a clamp, and then the assembled to-be-welded parts are placed in a vacuum chamber;

[0009] Step three, vacuum treatment is carried out on the vacuum chamber;

[0010] Step four, the superfast laser is aligned to the weld of the assembled to-be-welded parts, the pulse width of the laser is controlled to be 200 fs-10 ps, the laser power is controlled to be 10-120 W, the number of sub-pulses of a pulse train is controlled to be 1-4, and the welding speed is controlled to be 0.03-5 mm / s, superfast laser welding is carried out, and thus the connection of the ceramic reinforced aluminum matrix composite material is completed.

[0011] The ceramic reinforced aluminum matrix composite material is welded by using the superfast laser in the vacuum environment, on the one hand, the pulse width of the superfast laser is extremely short, so that the heat damage and heat influence caused by the superfast laser to the material are very small, the joint obtained has almost no welding deformation, and high-precision welding and micro-area welding can be realized. On the other hand, the vacuum environment can inhibit the oxidation of aluminum and improve the uniformity of the weld structure, which is beneficial to improving the mechanical properties of the joint. At the same time, the vacuum environment can also effectively increase the welding penetration, so that the thickness size range of the weldable workpiece is increased. This is because the superfast laser and the ceramic reinforced aluminum matrix composite material interact to produce a large amount of plasma and metal vapor. The plasma and metal vapor can absorb laser energy, have scattering and refraction effects on the laser, so that the laser energy density reaching the material is greatly attenuated. The vacuum condition is beneficial to the expansion and diffusion of the plasma and metal vapor, so that the plasma and metal vapor above the molten pool are more dilute, the “negative lens” effect of the laser is weakened, so that the utilization rate of the laser is improved, and the welding penetration is increased. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The low-magnification backscattered electron photograph of the 1mm-thick 45vol% SiC reinforced aluminum matrix composite material welding joint obtained by using the laser with a wavelength of 1030 nm, a frequency of 1 MHz and a pulse width of 300 fs under the conditions of a vacuum degree of 100 Pa, a laser power of 30 W and a welding speed of 0.15 mm / s in the embodiment one;

[0013] Figure 2 The high-magnification backscattered electron photograph and the energy spectrum area scan photograph of the top of the welding seam of the 1mm-thick 45vol% SiC reinforced aluminum matrix composite material welding joint obtained by using the laser with a wavelength of 1030 nm, a frequency of 1 MHz and a pulse width of 300 fs under the conditions of a vacuum degree of 100 Pa, a laser power of 30 W and a welding speed of 0.15 mm / s in the embodiment one;

[0014] Figure 3Figure 4 is a four-point bending fracture path optical microscope photograph of a butt joint of a 1 mm thick 45 vol% SiC reinforced aluminum matrix composite obtained in Example One using a laser with a wavelength of 1030 nm, a frequency of 1 MHz, and a pulse width of 300 fs at a vacuum degree of 100 Pa, a laser power of 30 W, and a welding speed of 0.15 mm / s;

[0015] Figure 4 Figure 5 is a backscattered electron photograph of a butt weld of a 1 mm thick 45 vol% SiC reinforced aluminum matrix composite obtained in Example Two using a laser with a wavelength of 1030 nm, a frequency of 1 MHz, and a pulse width of 300 fs at a vacuum degree of 100 Pa, a laser power of 28 W, and a welding speed of 0.05 mm / s;

[0016] Figure 5 Figure 6 is a cross-sectional backscattered electron photograph of a butt joint of a 1 mm thick 45 vol% SiC reinforced aluminum matrix composite obtained in Comparative Example One using a laser with a wavelength of 1030 nm, a frequency of 1 MHz, and a pulse width of 300 fs at atmospheric conditions, a laser power of 30 W, and a welding speed of 0.05 mm / s. DETAILED DESCRIPTION

[0017] Specific embodiment one: the method for ultrafast laser welding of ceramic reinforced aluminum matrix composites in a vacuum environment according to the following steps:

[0018] Step one: polish and polish the surfaces to be connected of the ceramic reinforced aluminum matrix composite, and obtain the welding parts after ultrasonic cleaning;

[0019] Step two: assemble the butt joint of the welding parts, clamp them using a clamp, and then place the assembled welding parts in a vacuum chamber;

[0020] Step three: vacuumize the vacuum chamber;

[0021] Step four: aim the ultrafast laser at the weld of the assembled welding parts, control the laser pulse width to be 200 fs~10 ps, the laser power to be 10~120 W, the number of sub-pulses in the pulse train to be 1~4, and the welding speed to be 0.03~5 mm / s, and perform ultrafast laser welding, thereby completing the connection of the ceramic reinforced aluminum matrix composite.

[0022] The present embodiment is provided with a light-transmitting mirror on the vacuum chamber to allow the ultrafast laser to pass through, and is provided with an air exhaust valve on the vacuum chamber to perform vacuumization treatment on the vacuum chamber by connecting a vacuum pump.

[0023] The present embodiment uses a pulse train laser mode, in which a single pulse can be divided into a series of sub-pulses.

[0024] The ultrafast laser welding in the vacuum environment of the embodiment can significantly improve the penetration, reduce the oxidation of the aluminum matrix, improve the uniformity of the weld structure, and be beneficial to improve the mechanical properties of the joint.

[0025] Specific embodiment two: the difference between this embodiment and specific embodiment one is that the thickness of the ceramic reinforced aluminum matrix composite in step one is 0.5-5 mm.

[0026] The embodiment can realize the welding of ceramic reinforced aluminum matrix composites with a thickness of more than 1 mm.

[0027] Specific embodiment three: the difference between this embodiment and specific embodiment one or two is that the ceramic reinforcing phase in the ceramic reinforced aluminum matrix composite in step one is SiC, B4C, TiC, AlN, Si3N4 or TiB2, and the volume fraction of the ceramic reinforcing phase is 10%-70%.

[0028] The embodiment can be applied to the welding of ceramic reinforced aluminum matrix composites with high reinforcing phase content (more than 40 vol%).

[0029] Specific embodiment four: the difference between this embodiment and one of specific embodiments one to three is that the polishing in step one is mechanical polishing of the connecting surface with 400#, 800#, 1500# and 2000# SiC sandpaper in sequence, and the polishing is performed using 0.05 μm SiO2 suspension.

[0030] Specific embodiment five: the difference between this embodiment and one of specific embodiments one to four is that the ultrasonic cleaning in step one is ultrasonic cleaning in anhydrous ethanol for 5-15 min.

[0031] Specific embodiment six: the difference between this embodiment and one of specific embodiments one to five is that the vacuum degree of the vacuum chamber is 10-1000 Pa in step three.

[0032] Specific embodiment seven: the difference between this embodiment and one of specific embodiments one to six is that the pulse width of the ultrafast laser in step four is 200 fs-800 fs.

[0033] Specific embodiment eight: the difference between this embodiment and one of specific embodiments one to seven is that the wavelength range of the ultrafast laser in step four is 800-1035 nm, the laser frequency is 1-2 MHz, and the number of sub-pulses in the pulse train is 1-3.

[0034] Specific embodiment nine: the difference between this embodiment and one of specific embodiments one to eight is that the laser power is controlled to be 10-120 W, the welding speed is 0.03-5 mm / s, the defocusing amount is -200-0 μm, the welding pass is 1-5, and the ultrafast laser welding is performed.

[0035] Specific implementation ten: the difference between this implementation and one of the specific implementations one to nine is that the welding path in step four is linear, zigzag, sinusoidal or circular.

[0036] Example one: the ultrafast laser welding method of the ceramic reinforced aluminum matrix composite material in this example is implemented according to the following steps:

[0037] I. Process 45vol% SiC reinforced aluminum matrix composite material into two 1mm thick welding pieces, polish the connecting surfaces of the welding pieces with 400#, 800#, 1500# and 2000# SiC sandpaper in turn, polish with 0.05μm SiO2 suspension after polishing, and then ultrasonic clean in anhydrous ethanol for 5min;

[0038] II. Assemble the welding pieces in a clamping jig, and then place the assembled welding pieces in a vacuum chamber;

[0039] III. Use a mechanical vacuum pump to pump the vacuum chamber, so that the vacuum degree in the vacuum chamber reaches 100Pa, close the ball valve connected between the mechanical vacuum pump and the vacuum chamber, and close the mechanical vacuum pump;

[0040] IV. Align the weld of the welding piece with the ultrafast laser, the laser wavelength is 1030nm, the pulse width is controlled to be 300fs, the laser frequency is 1MHz, the welding power is controlled to be 30W, the number of sub-pulses in the pulse train is 2, the welding speed is 0.15mm / s, the defocusing amount is 0μm, and the welding is performed once, and the welding path is linear, thereby completing the ultrafast laser welding of the ceramic reinforced aluminum matrix composite material in a vacuum environment.

[0041] The four-point bending strength test is performed on the 45vol% SiC reinforced aluminum matrix composite material joint and the 45vol% SiC reinforced aluminum matrix composite material base material obtained in this example, the average bending strength of the welded joint is about 535MPa, the average bending strength of the base material is about 620MPa, the bending strength of the joint reaches 85% of the strength of the base material, and the method of this example can obtain a SiC reinforced aluminum matrix composite material welded joint with high strength.

[0042] The backscattered electron photograph of the cross section of the 45vol% SiC reinforced aluminum matrix composite material butt joint obtained in this example under the condition of laser power 30W and welding speed 0.15mm / s is shown in Figure 1 The position most prone to oxidation during welding is the top of the weld, and the high-magnification backscattered electron photograph and energy spectrum area scan of the top of the weld are shown in Figure 2 The four-point bending fracture path optical microscope photograph of the joint is shown in Figure 3

[0043] From Figure 1 and​Figure 2 It can be seen that the weld structure obtained by using the method of the embodiment is relatively uniform, the oxidation phenomenon is obviously inhibited in the vacuum environment, there is no defect such as pore, incomplete fusion, incomplete penetration, and the connection quality is high. The weld width is about 50 μm, and almost no welding deformation is generated. From the Figure 3 It can be seen that the fracture position of the joint four-point bending strength test is in the weld or the base material, indicating that the weld strength is higher than the base material strength at some positions.

[0044] Embodiment Two: The method for ultrafast laser welding of the ceramic reinforced aluminum matrix composite material in the embodiment is implemented according to the following steps:

[0045] I. Two to-be-welded pieces of 45vol% SiC reinforced aluminum matrix composite material are processed into 1 mm thick, and the to-be-connected surfaces of the to-be-welded pieces are polished with 400#, 800#, 1500# and 2000# SiC sandpaper in sequence, and then polished with 0.05 μm SiO2 suspension, and then ultrasonically cleaned in anhydrous ethanol for 5 min;

[0046] II. The to-be-welded pieces are assembled in a butt joint manner by using a clamp, and then the assembled to-be-welded pieces are placed in a vacuum chamber;

[0047] III. The vacuum chamber is vacuumized by using a mechanical vacuum pump, so that the vacuum degree in the vacuum chamber reaches 100 Pa, a ball valve connected between the mechanical vacuum pump and the vacuum chamber is closed, and the mechanical vacuum pump is closed;

[0048] IV. The weld of the to-be-welded assembly is aligned by using an ultrafast laser, the wavelength of the laser is 1030 nm, the pulse width is 300 fs, the laser frequency is 1 MHz, the welding power is controlled to be 28 W, the number of sub-pulses of the pulse train is 2, the welding speed is 0.05 mm / s, the defocusing amount is 0 μm, the welding is performed once, and the welding path is linear, so that the ultrafast laser welding of the ceramic reinforced aluminum matrix composite material in the vacuum environment is completed.

[0049] The four-point bending strength test is performed on the 45vol% SiC reinforced aluminum matrix composite material joint obtained in the embodiment, the average bending strength of the welded joint is about 537 MPa, the bending strength of the joint reaches 85% of the strength of the base material, and the method of the embodiment can realize high-strength connection of the SiC reinforced aluminum matrix composite material.

[0050] The backscattered electron photograph of the cross section of the butt joint of the 45vol% SiC reinforced aluminum matrix composite material obtained in the embodiment under the condition of laser power 28 W and welding speed 0.05 mm / s is shown in Figure 4 .

[0051] From the Figure 4It can be seen that the welding seam obtained by using the method of the embodiment has no defects such as porosity, incomplete fusion and incomplete penetration, almost no welding deformation is generated, and the connection quality is high.

[0052] The comparative example one: the ultrafast laser welding method of the ceramic reinforced aluminum matrix composite material in the embodiment is implemented according to the following steps:

[0053] I. 45vol% SiC reinforced aluminum matrix composite material is processed into two welding pieces with a thickness of 1mm, the surfaces to be connected of the welding pieces are polished in turn using 400#, 800#, 1500# and 2000# SiC sandpaper, and then polished using 0.05μm SiO2 suspension, and then ultrasonic cleaning in anhydrous ethanol for 5min;

[0054] II. The welding pieces are assembled in a butt joint manner using a clamp, and then the assembled welding pieces are placed in a vacuum chamber;

[0055] III. The door of the chamber is opened, and the vacuum chamber is in an atmospheric environment;

[0056] IV. The welding seam of the assembled welding pieces is aligned using an ultrafast laser, the wavelength of the laser is 1030nm, the pulse width is 300fs, the laser frequency is 1MHz, the welding power is controlled to be 28W, the number of sub-pulses in a pulse train is 2, the welding speed is 0.05mm / s, the defocusing amount is 0μm, the welding is performed once, and the welding path is linear, thereby completing the ultrafast laser welding of the ceramic reinforced aluminum matrix composite material.

[0057] The backscattered electron photograph of the cross section of the butt joint of the 45vol% SiC reinforced aluminum matrix composite material obtained under the condition of a laser power of 30W and a welding speed of 0.05mm / s in the embodiment is shown in Figure 5 .

[0058] In the comparative example one and the embodiment two, the welding parameters used in the comparative example one have a larger heat input, and the larger heat input is more conducive to obtaining a larger penetration depth, however, it can be seen from Figure 5 that the welding seam depth obtained by using the method of the comparative example is only about 0.6mm even under a larger heat input, and the complete penetration of the 1mm thick workpiece cannot be achieved, while the complete penetration of the 1mm thick workpiece is achieved under a smaller heat input in the embodiment one and the embodiment two, therefore, the vacuum condition can significantly improve the penetration depth of the ultrafast laser welding. At the same time, the welding seam obtained under the atmospheric environment is more seriously oxidized, and the welding seam structure is non-uniform, which will adversely affect the mechanical properties of the butt joint.

Claims

1. A method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment, characterized in that... The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites is implemented according to the following steps: Step 1: Grind and polish the surfaces of the ceramic-reinforced aluminum matrix composite material to be joined, and then ultrasonically clean them to obtain the parts to be welded; Step 2: Assemble the parts to be welded by butt joints, clamp them with a fixture, and then place the assembled parts to be welded in a vacuum chamber; Step 3: Evacuate the vacuum chamber; Step 4: Align the ultrafast laser with the weld seam of the assembled workpiece, control the laser pulse width to be 200 fs to 10 ps, ​​the laser power to be 10 to 120 W, the number of pulse train sub-pulses to be 1 to 4, and the welding speed to be 0.03 to 5 mm / s to perform ultrafast laser welding, thereby completing the connection of ceramic reinforced aluminum matrix composite material.

2. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step one, the thickness of the ceramic-reinforced aluminum matrix composite material is 0.5~5mm.

3. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step one, the ceramic reinforcing phase in the ceramic-reinforced aluminum matrix composite material is SiC, B4C, TiC, AlN, Si3N4 or TiB2, and the volume fraction of the ceramic reinforcing phase is 10%~70%.

4. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step one, the grinding is done by mechanically grinding the surfaces to be joined with SiC sandpaper of 400#, 800#, 1500#, and 2000# in sequence. Polishing is done by polishing with 0.05μm SiO2 suspension.

5. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step one, ultrasonic cleaning is performed in anhydrous ethanol for 5-15 minutes.

6. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step three, the vacuum chamber is evacuated to a vacuum level of 10~1000Pa.

7. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step four, the pulse width of the ultrafast laser is 200 fs to 800 fs.

8. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step four, the ultrafast laser has a wavelength range of 800~1035nm, a laser frequency of 1~2MHz, and a number of sub-pulses in the pulse train of 1~3.

9. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step four, the laser power is controlled at 10~120W, the welding speed at 0.03~5mm / s, the defocusing amount at -200~0μm, and the number of welding passes at 1~5 times to perform ultrafast laser welding.

10. The method for ultrafast laser welding of ceramic-reinforced aluminum matrix composites in a vacuum environment according to claim 1, characterized in that... In step four, the welding path can be linear, zigzag, sinusoidal, or circular.

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