Miniature friction stirring head and preparation method thereof

Abstract

The invention belongs to the technical field of micro friction stir welding tools, and particularly relates to a micro friction stir head and a preparation method thereof. The stirring head is made of a nano MXene reinforced TC4-based composite material and comprises a stirring head shaft body, a movable shaft shoulder and a stirring needle, the movable shaft shoulder is connected with the stirring head shaft body, the stirring needle is arranged in the center of the end face of the movable shaft shoulder, a plurality of spiral grooves are symmetrically distributed in the end face of the movable shaft shoulder with respect to the center, and the spiral grooves form a planar spiral structure. The micro stirring head is of a double-layer flow guide structure with a main groove and an auxiliary groove, and has high abrasion resistance, adhesion resistance and high-temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of micro friction stir welding tools, and particularly relates to micro friction stir heads and their preparation methods. Background Technology

[0002] Friction stir welding (FSW), as a solid-state joining technology, has achieved large-scale application in the joining of medium and heavy plates in aerospace, rail transportation, and other fields due to its advantages such as high weld quality and low stress. However, with the increasing demand for lightweight, miniaturized, and precision components in current industries, especially in 3C product manufacturing (LCD TV frames, laptop shells, mobile phone bezels), medical devices, and precision manufacturing, the size of conventional FSW tools has revealed significant compatibility defects: on the one hand, existing micro-stirring heads have insufficient high-temperature wear resistance during operation, and are prone to weld metal adhesion, resulting in low welding efficiency and short service life; on the other hand, the plastic zone of ultra-thin plates has a higher surface area and volume ratio, and the heat loss rate in the welding area is faster, requiring increased stirring head speed to compensate for heat input. However, the heat resistance of existing micro-stirring heads is limited, and high-temperature friction at high speeds can easily lead to softening, deformation, or even breakage of the tool itself, making it difficult to balance heat input requirements and tool durability.

[0003] Existing stirring heads fall into two categories. One type uses tungsten carbide as the matrix, nickel as the binder, and MXene (0.08%-0.14%) as an auxiliary modifier. The process involves ball milling and hydrothermal reaction, emphasizing high hardness and wear resistance of the cutting tools, but it cannot achieve microstructure design. The other type uses tungsten carbide-reinforced tungsten-rhenium matrix (70%-94% tungsten), requiring high-temperature sintering at 2200-2350℃, resulting in high density and large rotational inertia after miniaturization. However, existing micro-friction stirring heads suffer from the following problems: (1) At present, there are few preparations of micro-friction stirring heads. At the same time, existing micro-stirring heads have problems such as insufficient high-temperature wear resistance and easy adhesion of weld metal during operation, resulting in low welding efficiency and short service life. (2) In traditional nanoparticle-reinforced TC4-based composite materials, the particles are prone to agglomeration and have weak interfacial bonding with the matrix, making it impossible to balance wear resistance and toughness. Furthermore, the microstructures are easily deformed during processing. (3) Conventional reinforcing materials (such as SiC and WC) are prone to undergoing interfacial reactions at high temperatures during micro-stir friction welding to generate brittle phases, which can lead to sudden breakage of the stirring head. (4) The existing micro-stirring head has a single groove structure on the shoulder end face of the moving shaft, which has a single path and weak plastic metal flow, resulting in uneven welding, small heat dissipation area, and severe flash. Summary of the Invention

[0004] To overcome the shortcomings of the prior art, this invention provides a micro-friction stirring head and its preparation method. The micro-stirring head of this invention has a double-layer flow guiding structure of "main channel + secondary channel," exhibiting high wear resistance, anti-adhesion properties, and high-temperature stability.

[0005] To achieve one of the above objectives, the present invention adopts the following technical solution: The micro-friction stirring head is made of TC4-based composite material reinforced with nano-MXene. The stirring head consists of a stirring head shaft, a moving shoulder, and a stirring pin. The stirring head shaft is connected to the moving shoulder. The stirring pin is located at the center of the end face of the moving shoulder. The end face of the moving shoulder is symmetrically arranged with several spiral grooves, which form a planar spiral structure.

[0006] Preferably, the spiral groove extends from the root of the stirring needle to the edge of the moving shaft shoulder, and the groove body of the spiral groove is a double-layer flow guiding structure composed of a main groove and a secondary groove, with the secondary groove being opened inside the main groove.

[0007] Preferably, the main groove has a rectangular cross-section without a top edge, the secondary groove has an arc-shaped cross-section, and the secondary groove is located at the bottom edge of the main groove rectangle.

[0008] Preferably, the TC4-based composite material comprises, by mass percentage: 88%-95% TC4 powder, 4%-10% MXene nanorolls, and 1%-2% Y2O3 nanoparticles.

[0009] Preferably, the length of the spiral groove is 4.3-4.9 mm; the width of the main groove is 0.3-0.6 mm and the height is 0.1-0.2 mm; the width of the secondary groove is 0.15-0.3 mm and the height is 0.05-0.1 mm; and the number of spiral grooves is 3-5.

[0010] Preferably, the particle size of the TC4 powder is 5-8 μm. The stirring head is a moving-shoulder stirring head.

[0011] To achieve the second objective mentioned above, the present invention provides a method for preparing a micro-friction stirring head, comprising the following steps: S1. Add Ti3AlC2 powder to the mixed solution and etch it by stirring in a constant temperature water bath for 10-12 hours to obtain a multilayer MXene dispersion; then add polyvinylpyrrolidone at a mass of 7%-39% of the mass of the Ti3AlC2 powder to the MXene dispersion, stir at 45-55℃ for 2-3 hours, and freeze-dry under vacuum to obtain MXene nanorolls. S2. Weigh the raw materials, add the weighed TC4 powder to ethylene glycol, disperse it by ultrasonication to form a uniform suspension, then add MXene nanofibers and Y2O3 nanoparticles, stir at 30-35℃ for 3-6 hours to obtain TC4-based composite material. S3. Using graphite material, a powder forming mold corresponding to the shape of the stirring head is machined by CNC. The TC4-based composite material obtained in step S2 is packaged into the mold and pressurized. After depressurization, the mold is removed to obtain the forming blank. S4. Clean the cleaned and shaped blank obtained in step S3 and apply aluminum foil to the core area. Use a fiber-coupled nanosecond laser to scan each spiral groove individually along the root of the stirring needle towards the edge of the moving shaft shoulder to obtain a micro-stirring friction stirring head.

[0012] Preferably, in step S1, the solid-liquid mass ratio of Ti3AlC2 powder to the mixed solution is 1:1.5; the mixed solution is prepared by 5g LiF and 100ml of 35% hydrochloric acid; the temperature of the constant temperature water tank is 25-35℃; the temperature of the vacuum freezing is -30 to -50℃. In step S2, the mass ratio of TC4 powder to ethylene glycol is 1:(1.5-3), and the ultrasonic dispersion time is 10-15 min.

[0013] Preferably, in step S3, when dispensing TC4-based composite material, each time a thickness of 0.2-0.5 mm is dispensed, and then a pressure of 1-3 MPa is applied for 10-15 seconds until the container is full. Then, the mold filled with TC4-based composite material is placed into a static press, first raised to 150 MPa at a rate of 5-10 MPa / s and held for 5-10 minutes; then raised to 250 MPa at a rate of 3-5 MPa / s and held for 10-15 minutes.

[0014] Preferably, in step S4, anhydrous ethanol is used to clean the molding blank, and the coating thickness of the aluminum foil is 0.08-0.12 mm; The scanning method of the spiral groove is as follows: scan the groove wall and bottom of the main groove and the groove wall and bottom of the secondary groove along the spiral direction of the spiral groove, wherein the spiral direction is from the center to the edge of the shoulder end face of the moving shaft; The energy density of the fiber-coupled nanosecond laser is 9 J / cm². 2 The scanning speed is 0.1 mm / s; the angle between the scanning line of the fiber-coupled nanosecond laser and the axis of the stirring needle is 30°.

[0015] The advantages of this invention are: (1) The micro stirring friction head of the present invention uses TC4-based composite material reinforced with nano-MXene and adds Y2O3 nanoparticles to improve interfacial compatibility. At the same time, the end face of the moving shaft shoulder of the micro stirring head adopts a double-layer flow guiding structure of "main groove + secondary groove" to improve the mixing uniformity of the material and has high wear resistance, anti-adhesion and high temperature stability.

[0016] (2) This invention utilizes a solution intercalation method to prepare a TC4-based composite material with "surface reinforcement" of sheet MXene nanorolls and Y2O3 nanoparticles, achieving a synergistic effect of wear resistance and toughness. Existing tungsten carbide-reinforced tungsten-rhenium matrix or titanium nitride (TiN), diamond-like carbon (DLC) coatings can cause Al, Mg, and other weld metals to easily adhere to the matrix surface, resulting in low welding efficiency and short service life. This invention utilizes the synergistic effect of sheet MXene nanorolls and Y2O3 nanoparticles to actively reduce wetting performance and achieve continuous and efficient welding. In addition, the "main groove + secondary groove" structure on the shoulder end face of the stirring head can provide dual flow guidance, accelerate weld metal flow, improve heat dissipation efficiency, reduce adhesion and defects, increase frictional contact area, and enhance heat input uniformity, thus meeting the high precision and high stability requirements of micro-welding.

[0017] (3) Application scenario of the invention: micro friction stir welding of the same or different metals in ultra-thin plates less than 1mm. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the present invention.

[0019] Figure 2 This is a schematic diagram of the structure of the present invention viewed from below.

[0020] Figure 3 This is a schematic diagram of the cross-sectional structure of the spiral groove of the present invention.

[0021] Figure 4 The figures show the performance test results of Embodiment 1 and Comparative Examples 1-3 of the present invention.

[0022] The meanings of the symbols marked in the figure are as follows: 1-Stirring head shaft body, 2-Moving shaft shoulder, 3-Stirring needle, 4-Helical groove, 5-Main groove, 6-Secondary groove. Detailed Implementation

[0023] The specific steps for preparing a micro friction stirrer head are as follows: Step 1: Prepare a mixed solution of 5g LiF + 100ml 35% hydrochloric acid. Mix Ti3AlC2 powder and the mixed solution at a solid-liquid mass ratio of 1:1.5. Add the weighed Ti3AlC2 powder to the weighed mixed solution and etch it by stirring in a constant temperature water bath at 25-35℃ for 10-12 hours to obtain a multilayer MXene dispersion. Then add polyvinylpyrrolidone (PVP) at a mass of 7%-39% of the above Ti3AlC2 powder to the dispersion, stir at 45-55℃ for 2-3 hours, and then freeze-dry under vacuum (-30~-50℃). Use PVP to induce MXene to curl into MXene nanorolls (diameter 100-200nm, length 500-800nm).

[0024] Step 2: Weigh out the following materials by mass percentage: 88%-95% TC4 powder (5-8 μm), 4%-10% MXene nanorolls, and 1%-2% Y2O3 (yttrium oxide) nanoparticles. Add the weighed TC4 powder to 1.5-3 times its mass of ethylene glycol and ultrasonically disperse for 10-15 min to form a uniform suspension. Then add MXene nanorolls and Y2O3 nanoparticles and stir at 30-35℃ for 3-6 h. This allows the reinforcing phases to bond with the hydroxyl groups on the surface of the TC4 powder through hydrogen bonds, resulting in each TC4 particle being uniformly coated with a layer of MXene and Y2O3. Finally, a TC4-based composite material is obtained. This method is called solution intercalation, which can completely replace the traditional ball milling method, resulting in more uniform material mixing.

[0025] Step 3: CNC machine graphite material as a powder forming mixing head mold. The mold is an integral moving shaft shoulder with needle mixing head shape. The diameter of the moving shaft shoulder 2 is 5-8 mm. The mixing needle 3 is conical (root diameter is 2.2-2.6 mm, end diameter is 1.8-2.2 mm, and the needle length is 60-70% of the plate thickness). The end face of the shaft shoulder has 3-5 spiral grooves 4 distributed symmetrically around the center. The 3-5 spiral grooves 4 form a planar spiral structure. The length of each spiral groove 4 is 4.3-4.9 mm. It extends from the root of the mixing needle 3 to the edge of the moving shaft shoulder 2. The groove body has a "main groove 5 + secondary groove 6" structure. The cross section of the main groove 5 is a rectangle without a top edge (width 0.3-0.6 mm, height 0.1-0.2 mm). The cross section of the secondary groove 6 is an arc groove, and the secondary groove 6 is opened at the bottom edge of the rectangle of the main groove 5 (width 0.15-0.3 mm, height 0.05-0.1 mm).

[0026] Step 4: Load the TC4-based composite material obtained in Step 2 into the mold processed in Step 3 in multiple batches, each batch being 0.2-0.5 mm thick. Then, apply a pressure of 1-3 MPa for 10-15 seconds until the mold is full. Place the mold filled with TC4-based composite material into a static press. First, increase the pressure to 150 MPa at a rate of 5-10 MPa / s and hold the pressure for 5-10 minutes. Then, increase the pressure to 250 MPa at a rate of 3-5 MPa / s and hold the pressure for 10-15 minutes. After the pressure is applied, slowly release the pressure and remove the mold to obtain the molded blank.

[0027] Step 5: Clean the molded blank obtained in Step 4 with anhydrous ethanol to remove surface graphite powder and debris. Apply a 0.08-0.12 mm thick layer of aluminum foil to the core areas such as the stirring head shaft body 1, moving shaft shoulder 2, and spiral groove 4 to eliminate laser scattering and energy deviation on the surface of the molded blank and improve the surface finish of the stirring pin 3; use a fiber-coupled nanosecond laser and set the energy density to 9 J / cm³.2 The scanning speed is 0.1 mm / s, and each spiral groove 4 is scanned individually. The scanning line of the fiber-coupled nanosecond laser is at an angle of 30° with the axis of the stirring needle 3. During the scanning, the walls and bottoms of the main groove 5 and the walls and bottoms of the secondary groove 6 are scanned along the spiral direction of the spiral groove 4. The spiral direction is from the center to the edge of the end face of the moving shaft shoulder 2. The wear resistance of the spiral groove is enhanced by the above scanning, and a finished micro stirring head is obtained.

[0028] Example 1

[0029] Step 1: Prepare a mixed solution of 5g LiF + 100ml 35% hydrochloric acid. Mix Ti3AlC2 powder and the mixed solution at a solid-liquid mass ratio of 1:1.5. Add 7.2g of Ti3AlC2 powder to the weighed mixed solution and etch it by stirring in a 30℃ constant temperature water bath for 11 hours to obtain a multilayer MXene dispersion. Then add 1.68g of polyvinylpyrrolidone (PVP) to the dispersion, stir at 50℃ for 2.5h, and freeze-dry under vacuum to obtain MXene nanorolls.

[0030] Step 2: Weigh 73.6g of TC4 powder, 5.6g of MXene nanorolls, and 0.8g of Y2O3 nanoparticles; add TC4 powder to 147.2g of ethylene glycol and disperse by ultrasonication for 12min to form a uniform suspension. Then add MXene nanorolls and Y2O3 nanoparticles and stir at 32℃ for 5h to obtain TC4-based composite material.

[0031] Step 3: CNC machine graphite material to form a powder forming mixing head mold. The mold is an integral moving shaft shoulder with needle mixing head shape. The moving shaft shoulder 2 has a diameter of 6.4 mm, and the mixing needle 3 is conical (root diameter of 2.6 mm, end diameter of 2.2 mm, and needle length of 0.3 mm). The end face of the moving shaft shoulder 2 has 5 spiral grooves 4 symmetrically distributed around the center. Each spiral groove 4 is 4.6 mm long and extends from the root of the mixing needle 3 to the edge of the moving shaft shoulder 2 at an angle of 120°. The groove body has a "main groove 5 + secondary groove 6" structure. The cross-section of the main groove 5 is a rectangle without a top edge (width 0.5 mm, height 0.14 mm), and the cross-section of the secondary groove 6 is an arc-shaped groove. The secondary groove 6 is opened at the bottom edge of the rectangle of the main groove 5 (width 0.25 mm, height 0.07 mm).

[0032] Step 4: The TC4-based composite material obtained in Step 2 is repeatedly loaded into the mold processed in Step 3, with each loading being 0.3 mm thick. Then, a pressure of 2 MPa is applied for 12 seconds until the mold is full. The mold filled with the TC4-based composite material is then placed into a static press. The pressure is first increased to 150 MPa at a rate of 7 MPa / s and held for 8 minutes. Then, the pressure is increased to 250 MPa at a rate of 4 MPa / s and held for 12 minutes. After the pressure is applied, the pressure is slowly released and the mold is removed to obtain the molded blank.

[0033] Step 5: Clean the shaped blank obtained in Step 4 with anhydrous ethanol, then apply 0.1mm thick aluminum foil to the core areas such as the stirring head shaft body 1, moving shaft shoulder 2, and spiral groove 4. Use a fiber-coupled nanosecond laser and set the energy density to 9 J / cm². 2 The scanning speed is 0.1 mm / s, and each spiral groove 4 is scanned individually. The angle between the scanning line and the axis of the stirring needle 3 is 30°. During scanning, the walls and bottoms of the main groove 5 and the walls and bottoms of the secondary groove 6 are scanned along the spiral direction of the spiral groove 4. The spiral direction is from the center to the edge of the end face of the moving shaft shoulder 2. Finally, a finished product-grade micro stirring head is obtained, with the structure as shown in the figure. Figure 1-3 As shown.

[0034] Comparative Example 1

[0035] The preparation method of the second comparative stirring head is basically the same as that of Example 1, except that the raw materials of the second stirring head are 93% TC4 powder and 7% MXene nanofibers (without added Y2O3 nanoparticles) by mass percentage, and the total feed mass is still 80g, of which 74.4g is TC4 powder and 5.6g is MXene nanofibers.

[0036] Comparative Example 2

[0037] The preparation method of the comparative example stirring head three is basically the same as that of Example 1 in terms of the amount of raw materials input. The difference is that the shoulder end face of the stirring head three is provided with only 5 centrally symmetrically distributed single spiral grooves 4 (without secondary grooves 6), and the groove size is the same as the main groove 5 of Example 1 (width 0.5 mm, height 0.14 mm).

[0038] Comparative Example 3

[0039] The preparation method of the comparative example stirring head four is basically the same as that of Example 1 in terms of the amount of raw materials fed. The difference is that the preparation process of the stirring head four adopts traditional ball milling and conventional sintering, with a ball milling speed of 300 rpm / min and a time of 2 hours, and a sintering temperature of 1200℃ and a holding time of 2 hours.

[0040] The stirring head 1 prepared in Example 1 and the stirring heads 2 to 4 prepared in Comparative Examples 1-3 were subjected to performance tests under the same conditions. The test method was as follows: using the stirring head, a 0.5 mm thick 6061 aluminum alloy sheet was welded at a rotation speed of 200 rpm / min and a travel speed of 40 mm / min. The welding parameters were a rotation speed of 200 rpm / min and a travel speed of 40 mm / min. The core performance of the welded sheet was then tested, and the results are shown in Table 1 and... Figure 4 As shown: Table 1. Comparison of Core Performance Tests between the Example and Comparative Examples

[0041] From Table 1 and Figure 4 It can be seen that the aluminum alloy sheet prepared by the stirring head in Example 1 has a reinforcing phase agglomeration rate of only 2.3%, a high-temperature wear rate as low as 1.8 mg / h, a weld metal adhesion rate of 1.5%, and a flash height of 0.04 mm, exhibiting the best overall performance. Furthermore, the weld tensile strength reaches 225 MPa, and the elongation is 12.8%. The weld tensile strength and elongation of Example 1 are significantly higher than all comparative examples, fully demonstrating the synergistic advantages of the materials, structure, and process of this invention.

[0042] The aluminum alloy sheet prepared with the stirring head of Comparative Example 1 showed an increased reinforcing phase agglomeration rate of 11.7%, a high-temperature wear rate of 4.9 mg / h, a weld metal adhesion rate of 3.8%, and a flash height of 0.05 mm. Furthermore, the weld tensile strength was 178 MPa, and the elongation was 8.5%. Both the weld tensile strength and elongation of Comparative Example 1 were lower than those of Example 1, demonstrating the necessity of Y2O3 nanoparticles for improving the performance of the stirring head and the welding quality.

[0043] The aluminum alloy sheet prepared by the stirring head 3 in Comparative Example 2 showed an increased flash height of 0.18 mm, a weld metal adhesion rate of 5.2%, a reinforcing phase agglomeration rate of 2.4%, and a high-temperature wear rate of 2.1 mg / h. Furthermore, the weld tensile strength was 156 MPa, and the elongation was 6.3%. Both the weld tensile strength and elongation were significantly lower than in Example 1, highlighting the importance of the "main channel 5 + secondary channel 6" double-layer guiding structure in improving weld formation quality.

[0044] The aluminum alloy sheet prepared by stirring head four in Comparative Example 3, due to the use of traditional processes, suffered from severe MXene agglomeration, with a reinforcing phase agglomeration rate of 15.4%. Insufficient high-temperature stability led to a high-temperature wear rate of 6.7 mg / h, a weld metal adhesion rate of 8.6%, and a flash height of 0.07 mm. Furthermore, the weld tensile strength was 132 MPa, and the elongation was 4.7%. The weld tensile strength and elongation of this comparative example were the lowest among all schemes, fully demonstrating the innovation and superiority of the "solution intercalation + gradient hydrostatic pressing + laser strengthening" process of this invention.

[0045] The application scenarios of this invention are not limited to micro friction stir welding, but can also be extended to the development of products such as micro resistance welding electrode heads and micro friction stir repair tools, thereby providing other new solutions for material processing of micro electronic components and precision metal parts.

[0046] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A miniature friction stirring head, characterized in that: The stirring head is made of TC4-based composite material reinforced with nano-MXene. The stirring head consists of a stirring head shaft (1), a moving shoulder (2), and a stirring needle (3). The stirring head shaft (1) is connected to the moving shoulder (2). The stirring needle (3) is located at the center of the end face of the moving shoulder (2). The end face of the moving shoulder (2) is provided with several spiral grooves (4) arranged symmetrically around the center. The several spiral grooves (4) form a planar spiral structure.

2. The miniature friction stirring head according to claim 1, characterized in that: The spiral groove (4) extends from the root of the stirring needle (3) to the end face edge of the moving shaft shoulder (2). The groove body of the spiral groove (4) is a double-layer flow guiding structure composed of a main groove (5) and a secondary groove (6). The secondary groove (6) is opened in the main groove (5).

3. The miniature friction stirring head according to claim 2, characterized in that: The main groove (5) has a rectangular cross-section without a top edge, and the secondary groove (6) has an arc-shaped cross-section, with the secondary groove (6) located at the bottom edge of the main groove (5) rectangle.

4. The miniature friction stirring head according to claim 1, characterized in that, The TC4-based composite material comprises, by mass percentage: 88%-95% TC4 powder, 4%-10% MXene nanorolls, and 1%-2% Y2O3 nanoparticles.

5. The micro friction stirring head according to claim 2, characterized in that: The length of the spiral groove (4) is 4.3-4.9 mm; the width of the main groove (5) is 0.3-0.6 mm and the height is 0.1-0.2 mm; the width of the secondary groove (6) is 0.15-0.3 mm and the height is 0.05-0.1 mm; the number of spiral grooves (4) is 3-5.

6. The miniature friction stirring head according to claim 4, characterized in that: The particle size of the TC4 powder is 5-8 μm.

7. The method for preparing the micro-friction stirring head according to any one of claims 1-6, characterized in that, Includes the following steps: S1. Add Ti3AlC2 powder to the mixed solution and etch it by stirring in a constant temperature water bath for 10-12 hours to obtain a multilayer MXene dispersion; then add polyvinylpyrrolidone at a mass of 7%-39% of the mass of the Ti3AlC2 powder to the MXene dispersion, stir at 45-55℃ for 2-3 hours, and freeze-dry under vacuum to obtain MXene nanorolls. S2. Weigh the raw materials, add the weighed TC4 powder to ethylene glycol, disperse it by ultrasonication to form a uniform suspension, then add MXene nanofibers and Y2O3 nanoparticles, stir at 30-35℃ for 3-6 hours to obtain TC4-based composite material. S3. Using graphite material, a powder forming mold corresponding to the shape of the stirring head is machined by CNC. The TC4-based composite material obtained in step S2 is packaged into the mold and pressurized. After depressurization, the mold is removed to obtain the forming blank. S4. Clean the shaped blank obtained in step S3 and apply aluminum foil to the core area. Use a fiber-coupled nanosecond laser to scan each spiral groove (4) along the root of the stirring needle (3) towards the edge of the moving shaft shoulder (2) to obtain a micro stirring friction stirring head.

8. The method for preparing the micro-friction stirring head according to claim 7, characterized in that: In step S1, the solid-liquid mass ratio of Ti3AlC2 powder to the mixed solution is 1:1.5; the mixed solution is composed of 5g LiF and 100ml of 35% hydrochloric acid; the temperature of the constant temperature water tank is 25-35℃; the temperature of the vacuum freezing is -30 to -50℃. In step S2, the mass ratio of TC4 powder to ethylene glycol is 1:(1.5-3), and the ultrasonic dispersion time is 10-15 min.

9. The method for preparing the micro-friction stirring head according to claim 7, characterized in that: In step S3, when dispensing TC4-based composite material, each batch is 0.2-0.5 mm thick, and then lightly pressed with a pressure of 1-3 MPa for 10-15 seconds until it is full. Then, the mold filled with TC4-based composite material is placed into a static press, first raised to 150 MPa at a rate of 5-10 MPa / s and held for 5-10 minutes; then raised to 250 MPa at a rate of 3-5 MPa / s and held for 10-15 minutes.

10. The method for preparing the micro-friction stirring head according to claim 7, characterized in that: In step S4, the forming blank is cleaned with anhydrous ethanol, and the coating thickness of the aluminum foil is 0.08-0.12 mm. The scanning method of the spiral groove (4) is as follows: scan the groove wall and bottom of the main groove (5) and the groove wall and bottom of the secondary groove (6) along the spiral direction of the spiral groove (4); The energy density of the fiber-coupled nanosecond laser is 9 J / cm². 2 The scanning speed is 0.1 mm / s; the angle between the scanning line of the fiber-coupled nanosecond laser and the axis of the stirring needle (3) is 30°.

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