Metal / multi-gradient thermoplastic composite friction stir additive system and method

Abstract

The application discloses a metal / multi-gradient thermoplastic composite material friction stir additive system and method, which comprises a powder feeding system, a friction stir additive system and a cooling system; the friction stir additive system (3) comprises an eddy current heating device (31), a rod forming chamber (32), a rod forming channel (33) and a stirring head (34); plastic deformation occurs under the friction stir extrusion of the stirring head (34); the material is deposited on a base plate under the stirring and top forging action of the stirring head protrusion (35); and the stirring head moves according to a set moving path, so that a deposition layer is formed on the base plate. The obtained integrated forming piece has the following advantages: the metal material layer and the thermoplastic composite material layer are connected closely, the interface between the thermoplastic composite material layers is connected closely, the mechanical properties are good, the reinforcing phase in the thermoplastic composite material layer is uniformly distributed, and the surface layer performance of the multi-gradient thermoplastic composite material of the forming piece is more excellent than that of a single thermoplastic composite material surface layer.

Description

Technical Field

[0001] This invention belongs to the field of friction stir additive manufacturing technology, specifically relating to a multi-material gradient friction stir additive manufacturing system and method for metal / multi-gradient thermoplastic composite materials. Background Technology

[0002] Friction stir deposition (AFSD) is an emerging solid-state additive manufacturing technology. This technology utilizes frictional heat and plastic deformation generated by a stirring head to soften the material, allowing it to be deposited layer by layer according to a computer-defined deposition path. Since the material does not melt during the additive manufacturing process, there are no melting defects such as porosity or hot cracks, thus overcoming the inherent defects of cladding additive manufacturing. Furthermore, it boasts high additive manufacturing efficiency, making it suitable for the additive manufacturing of large-sized parts. Simultaneously, the additive manufacturing process has low environmental requirements, theoretically allowing it to be carried out in a vacuum or underwater. In terms of environmental friendliness, it does not produce polluting gases, making it green and environmentally friendly. Currently, friction stir additive manufacturing technology has been applied in the fields of metal material additive manufacturing and composite material additive manufacturing.

[0003] Thermoplastic composites possess advantages such as good fatigue resistance, high specific strength, low density, corrosion resistance, and high temperature resistance, while metallic materials have mature processing technology and good thermal conductivity and high specific stiffness. Based on the superior properties of both materials, lightweight composite components made of thermoplastic composites and metallic materials are widely used in the aerospace field, provided that performance requirements are met. Currently, traditional thermoplastic composite / metal composite components are formed by mechanically joining, gluing, or welding the respective components after they have been molded. However, thermoplastic composite / metal composite components formed through traditional processes are not only inefficient in forming, costly in processing, and complex and limited in their processes, but also suffer from difficulties in joining and low strength at the joint surfaces due to the significant differences in physical and chemical properties between the metal and the thermoplastic composite. Therefore, there are limitations to manufacturing thermoplastic composite / metal composite components through joining processes.

[0004] Thermoplastic composites can also be used to achieve functionally graded material printing (fJTs) (fJTs refer to materials whose components change continuously or quasi-continuously from one end to the other). However, currently, the preparation of fJTs is often based on cladding additive manufacturing technology. For example, patent CN108480630B proposes a device and method for preparing gradient materials based on selective laser melting technology, in which different concentrations of pre-prepared materials are laid in each layer, followed by selective laser melting deposition. However, there are few reports on the preparation of gradient thermoplastic composites based on solid-state additive manufacturing technology. Furthermore, the preparation of gradient thermoplastic materials based on cladding additive manufacturing technology generally uses multiple nozzles, requiring the pre-preparation of materials of different concentrations and their filling into multiple nozzles. During the manufacturing process, multiple nozzles need to cooperate with each other and frequently switch, or complex placement devices need to be assembled. The preparation of gradient materials based on this process is complex and inefficient.

[0005] Based on the above problems, there is an urgent need to propose a new system and process to improve the traditional manufacturing process of mixed thermoplastic composite and metal parts, so as to realize the integrated molding of metal / multi-gradient thermoplastic composite materials and the simultaneous integrated molding of proportioned materials and single printhead printing. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a system and process method for integrated friction stir additive manufacturing of metal / multi-gradient thermoplastic composites. This method achieves integrated manufacturing of thermoplastic composites / metal substrates through synchronous powder feeding friction stir additive manufacturing, enabling multi-gradient printing of thermoplastic composites. The resulting integrated molded part exhibits tight interfacial bonding between the metal material layer and the thermoplastic composite layer, as well as between thermoplastic composite layers, resulting in excellent mechanical properties. The reinforcing phase is uniformly distributed within the thermoplastic composite layer, and the surface properties of the multi-gradient thermoplastic composite layer are superior to those of a single thermoplastic composite surface layer.

[0007] A first aspect of the present invention provides a metal / multi-gradient thermoplastic composite friction stir additive manufacturing system. To achieve the objective of the invention, the technical solution is as follows: A friction stir additive manufacturing system for metal / multi-gradient thermoplastic composite materials, characterized in that it includes a powder feeding system, an additive manufacturing device, and a cooling system; the additive manufacturing device 3 includes an eddy current heating device 31, a rod forming chamber 32, a rod forming channel 33, and a stirring head 34; the stirring head 34 has a hollow structure, the internal cavity of which is the rod forming channel 33, the upper part of the rod forming channel 33 is connected to the lower part of the rod forming chamber 32, and the upper part of the rod forming chamber 32 is connected to the extrusion piston channel 36; the powder is fed through the powder feeding system. The powder is fed into the rod forming chamber 32 via the inlet channel 30. The eddy current heating device 31 surrounds the outside of the spherical rod forming chamber 32 and heats the powder fed into the rod forming chamber 32. The extrusion piston 1 extrudes the powder in the rod forming chamber 32 into the rod forming channel 33 inside the stirring head 34. Under the stirring and friction extrusion of the stirring head 34, plastic deformation occurs. Under the stirring and upsetting action of the stirring head protrusion 35, the material is plastically softened and deposited on the substrate. The stirring head moves according to the set moving path to form a deposition layer on the substrate.It also includes a laser 4, which is clamped in front of the stirring head 34 and can heat the substrate in front of the stirring path at a temperature of 200-600℃. The cooling system includes a substrate 5, a processing cylinder 7, a lifting platform 6, an input valve 9, an output valve 8, and a drainage base 11. The lifting platform 6 is disposed in the processing cylinder 7, the drainage base 11 is disposed on the lifting platform 6, and the substrate 5 is disposed on the drainage base 11. Coolant flows into the processing cylinder 7 through the input valve 9. After the coolant in the processing cylinder 7 reaches a certain height, it flows into the drainage channels at the bottom and sides of the drainage base 11. The coolant then flows to the top of the guide base 11 and out through the groove. The flow rate is controlled by input / output solenoid valves to achieve cooling and temperature control of the substrate 5 and the already formed stirring layer on the substrate. The powder feeding system includes a powder feeding device and a powder mixing device 2. The powder mixing device 2 includes a rotating device 20, a rotating rod 21, a first powder inlet 22, a second powder inlet 23, a guide plate 24, a rolling bearing 25, a blade ring 26, a powder mixing inner chamber 27, a powder mixing outer chamber 28, and a powder output channel 29. The first powder inlet... 22. A second powder inlet 23 is located at the top of a cylindrical container. The interior of this cylindrical container is divided into two interconnected chambers: an upper mixing chamber 27 and a lower mixing chamber 28. A perforated guide plate 24 is installed at the top of the mixing chamber 27. A rolling bearing 25 is installed between the outer surface of the guide plate 24 and the inner wall of the mixing chamber 27. The center of the guide plate 24 is fixed to a rotating rod 21. Inside the mixing chamber 27, below the guide plate 24, a blade ring 26 is coaxially fixed to the rotating rod 21. In the lower part of chamber 27, inside the powder mixing outer chamber 28, a blade ring 26 is also installed, coaxially fixed to the rotating rod 21 with the guide plate 24. Driven by the rotating device 20, the rotating rod 21, the guide plate 24, and the two blade rings 26 rotate synchronously. The powder is fed into the first powder inlet 22 and the second powder inlet 23 by the powder feeder, and falls into the powder mixing inner chamber 27 by its own gravity through the perforation of the guide plate 24. Under the action of the rotating blade ring 26, it is mixed evenly and falls into the output channel 29 of the powder mixing outer chamber 28, and then output to the additive manufacturing device through the conduit 10.

[0008] The friction stir additive manufacturing system has coolant inflow channels on the bottom and sides of the flow base 11, and a groove is provided on the side of the flow base 11 that contacts the substrate; the lifting platform 6 controls the up and down movement of the substrate 5 to realize the additive manufacturing of materials by friction stir layer by layer.

[0009] The stirring friction additive system described herein has a heating temperature range of 0-400℃ for the eddy current heating device.

[0010] The method according to any of the described friction stir additive manufacturing systems includes the following steps: Step 1: Clamp the flow base onto the processing cylinder, fix the printing substrate on the base with a clamp, and use the lifting platform to bring the substrate to the printing position. The stirring head of the additive manufacturing system spindle contacts the substrate. Coolant is fed into the processing cylinder through the input valve. After the coolant in the processing cylinder reaches the lower end of the substrate through the flow base, the height of the coolant in the processing cylinder is maintained by the solenoid valve. The coolant flows out through the output valve. Step 2: The metal powder is fed into the powder feeding port of the outer mixing chamber by the powder feeder, falls into the inner mixing chamber by its own gravity, and is guided into the bottom output channel of the outer chamber through the inner chamber guide plate. The metal powder is then output to the upper chamber of the rod forming chamber through the conduit. Step 3: The eddy current heating device heats the metal powder for friction stir additive manufacturing: Under the pressure of the extrusion piston, a rod is formed in the lower chamber of the rod forming chamber. Under further extrusion, the rod reaches the position of the stirring head and the stirring shaft shoulder cavity. Under the action of stirring friction, axial forging force and extrusion force, plastic deformation occurs. The plastically softened material is deposited on the substrate by the stirring head. The stirring head forms a dense deposition layer on the substrate according to a certain moving path. Step 4: After completing one deposition layer, reset the stirring head and repeat steps 2 and 3. The metal rod is stirred and rubbed to deposit a metal layer of a certain height and thickness. After the metal substrate layer is printed, proceed to step 5. Step 5: Change the printing material and clear the printing residue. The first powder feeder feeds short fiber particles through the first powder input port, and the second powder feeder feeds thermoplastic resin powder through the second powder input port. Adjust the powder feeding rate to achieve the material ratio 1. Start the rotating device. The guide plate, blade ring and rotating rod rotate synchronously to mix the short fiber particles and thermoplastic resin powder evenly. Step 6: Activate the laser in front of the stirring head in the friction stir additive manufacturing process. The laser preheats the metal substrate in the direction of the stirring head's movement. Repeat the friction stir additive manufacturing process in Step 3 to form a short fiber thermoplastic composite material deposition layer with ratio 1. Step 7: Turn off the laser, repeat steps 5 and 6, adjust the ratio 1 in step 5 to ratio 2, and form a short fiber thermoplastic composite material deposition layer of ratio 2 on the thermoplastic composite material stirring layer of ratio 1; finally complete the friction stir additive manufacturing of multi-gradient thermoplastic composite material.

[0011] Preferably, the cooling system in step one is used to cool the formed stirring layer to prevent the formed deposition layer from plastically softening and collapsing when the next deposition layer is formed.

[0012] Preferred: In step two, different powder feeding rates of the powder feeder can achieve different ratios of the two materials.

[0013] Preferably, in step five, the rotating rod blades and the guide plate mix the short fiber particles and thermoplastic resin powder evenly.

[0014] Preferred option: In step six, the laser is used to preheat the metal substrate, so that the metal substrate can also achieve plastic softening during the friction stir thermoplastic composite material process.

[0015] The beneficial effects of this invention are as follows: 1. By employing friction stir additive manufacturing technology and laser-assisted heating, the metal substrate material can also achieve plastic softening while the friction stir thermoplastic composite material is being manufactured. Then, through stirring and friction bonding by the stirring head, the integrated molding of thermoplastic composite / metal material combination parts is achieved, which improves the molding quality and mechanical properties of the combination parts and solves the problems of complex traditional manufacturing processes, unreliable connections, and low efficiency.

[0016] 2. Different powder feeding rates are used in the powder feeder. The two powder materials are then uniformly mixed through the rotating blades and guide plates in the mixing chamber, achieving different proportions for the thermoplastic composite material. The powder is then extruded by the extrusion device to form rods, which helps improve the molding quality.

[0017] 3. Overcoming the limitations of existing additive manufacturing technologies that require multiple printheads or pre-configuration of different concentrations of printing materials to prepare multi-gradient composite materials, this technology allows for the simultaneous mixing of thermoplastic composite materials with different powder ratios and single-printhead additive manufacturing, giving it a certain advantage in the field of preparing multi-gradient thermoplastic composite materials.

[0018] 4. The use of emerging solid-phase additive manufacturing technology to prepare gradient materials has more advantages than the use of cladding additive manufacturing technology. It avoids the generation of melting defects such as hot cracks and pores, and is environmentally friendly. Attached Figure Description

[0019] Figure 1 A schematic diagram of the structure of the metal / multi-gradient thermoplastic composite friction stir additive manufacturing system device provided for embodiments of the present invention; Figure 2 This is a schematic diagram of the powder mixing device of the present invention; Figure 3 This is a schematic diagram of the structure of the drainage plate of the present invention; Figure 4 This is a schematic diagram of the structure of the friction stir additive manufacturing device of the present invention; Figure 5 This is a schematic diagram of the powder mixing chamber of the present invention; Figure 6 This is a schematic diagram of the drainage base of the present invention; 1-Extrusion piston, 2-Powder mixing device, 3-Additive manufacturing device, 4-Laser, 5-Substrate, 6-Lifting platform, 7-Processing cylinder, 8-Output valve, 9-Input valve, 10-Conduit, 11-Drainage base, 20-Rotating device, 21-Rotating rod, 22-First powder input port, 23-Second powder input port, 24-Drainage plate, 25-Rolling bearing, 26-Rotating blade ring, 27-Powder mixing inner chamber, 28-Powder mixing outer chamber, 29-Powder output channel, 210-Powder baffle plate, 211-Rolling bearing, 30-Powder input channel, 31-Edge heating device, 32-Bar forming chamber, 33-Bar forming channel, 34-Stirring head, 35-Stirring head protrusion, 36-Extrusion piston channel, 37-Hollow bar channel; Detailed Implementation

[0020] The present invention will be described in detail below with reference to specific embodiments. Example

[0021] like Figure 1-4 As shown, this embodiment provides a metal / multi-gradient thermoplastic composite friction stir additive manufacturing system, suitable for the integrated forming of multi-gradient thermoplastic composite materials / metal substrates. It includes a powder feeding system, an additive manufacturing apparatus, and a cooling system below the additive manufacturing apparatus.

[0022] The powder feeding system includes a powder feeding device and a powder mixing device 2. The powder mixing device 2 includes a rotating device 20, a rotating rod 21, a first powder inlet 22, a second powder inlet 23, a guide plate 24, a rolling bearing 25, a blade ring 26, a powder mixing inner chamber 27, a powder mixing outer chamber 28, and a powder output channel 29. Figure 2 As shown, in this embodiment, the first powder inlet 22 and the second powder inlet 23 are located at the top of a cylindrical container. The interior of this cylindrical container is divided into two interconnected chambers: an upper mixing chamber 27 and a lower mixing chamber 28. A perforated guide plate 24 is provided at the top of the mixing chamber 27. A rolling bearing 25 is provided between the outside of the guide plate 24 and the inner wall of the mixing chamber 27. The center of the guide plate 24 is fixed to a rotating rod 21. Inside the mixing chamber 27, below the guide plate 24, a blade ring 26 is coaxially fixed to the rotating rod 21 with the guide plate 24. 1. In the lower part of the powder mixing chamber 27 and inside the powder mixing outer chamber 28, a blade ring 26 is also provided, which is coaxially fixed on the rotating rod 21 with the guide plate 24. Under the drive of the rotating device 20, the rotating rod 21, the guide plate 24, and the two blade rings 26 rotate synchronously. The powder is fed into the two powder feeding ports 22 and 23 by the powder feeder, and falls into the powder mixing chamber 27 by its own gravity through the hollow of the guide plate 24. Under the action of the rotation of the blade ring 26, it is mixed evenly and falls into the output channel 29 of the powder mixing outer chamber 28, and then output to the powder input channel 30 of the additive manufacturing device 3 through the conduit 10.

[0023] The additive manufacturing apparatus 3 includes an eddy current heating device 31, a rod forming chamber 32, a rod forming channel 33, and a stirring head 34. Powder is output to the rod forming chamber 32 via a powder input channel 30. The eddy current heating device 31 surrounds the spherical rod forming chamber 32, heating the powder fed into it. The extrusion piston 1 extrudes the powder from the rod forming chamber 32 into the hollow rod channel 37 inside the stirring head 34. Under the stirring and frictional extrusion of the stirring head 34, plastic deformation occurs. Under the stirring and forging action of the stirring head protrusion 35, the material plastically softens and deposits on the substrate. The stirring head moves along a pre-set path, forming a deposition layer on the substrate. After printing the metal substrate, the laser 4 heats the metal substrate in front of the stirring head 34's path while printing multi-gradient thermoplastic materials.

[0024] The cooling system includes a base plate 5, a processing cylinder 7, a lifting platform 6, an input valve 9, an output valve 8, and a drainage base 11. Figure 1 As shown, the lifting platform 6 is installed in the processing cylinder 7, the flow-guiding base 11 is installed on the lifting platform 6, and the substrate 5 is installed on the flow-guiding base 11. Coolant flows into the processing cylinder 7 through the input valve 9. After the coolant in the processing cylinder 7 reaches a certain height, it flows into the flow-guiding channels at the bottom and sides of the flow-guiding base 11, then flows to the top of the flow-guiding base 11 and out through the grooves. The coolant then flows out from the output valve. The flow rate is controlled by the input and output solenoid valves to achieve the cooling and temperature control of the substrate 5 and the already formed stirring layer on the substrate. Figure 6 As shown, the coolant inflow channel is located on the bottom and side of the drainage base 11, and a groove is formed on the side of the drainage base 11 that contacts the substrate. The lifting platform 6 controls the up and down movement of the substrate 5 to achieve additive manufacturing by layer-by-layer accumulation of materials through stirring and friction. Example

[0025] This embodiment provides a process for friction stir additive manufacturing of metal / multi-gradient thermoplastic composite materials. Using the friction stir additive manufacturing system and apparatus provided in Embodiment 1, composite parts of short carbon fiber thermoplastic composite materials / aluminum alloy metal substrates with different gradients are printed.

[0026] The stirring head is made of tool steel, the stirring protrusion is 3mm long, and the hollow bar channel in the stirring head is 20mm in diameter.

[0027] Stirring head forward speed: 50~2000mm / min; Stirring head rotation speed: 500~2500r / mm; Powder feeder speed: 100-1000mm / min 3 / min; Extrusion piston downward pressure: 20-300KN; Stirring head forging force: 10~500KN; Stirring head pressing amount: 0.1~10mm.

[0028] Using cast A6061-T6 aluminum alloy as the substrate, with a substrate size of 1200mm*1200mm*100mm, and additive materials including A6061-T6 aluminum alloy powder (particle size: 40-160um), short carbon fiber particles (particle size: 80um-400um), and PEEK resin powder (particle size: 50um-150um), a test plate with a size of 800mm*800mm*8mm was printed, which is a combination of A6061-T6 aluminum alloy substrate and two or more thermoplastic composite materials with different gradients.

[0029] The specific composition of A6061-T6 aluminum alloy is shown in the table below:

[0030] Specifically, the friction stir additive manufacturing method provided in this embodiment includes the following steps: Step 1: Use 2000# sandpaper to polish the substrate to remove surface impurities and oxides. After polishing, wipe the surface with alcohol and clean it. Then, use a clamp to fix the substrate on the base, adjust the position of the substrate and the stirring head, and feed the water coolant into the processing cylinder.

[0031] Step 2: Set the stirring head rotation speed to 1500 r / min, the upsetting force to 300 KN, the forward speed to 500 mm / min, the stirring head pressing depth to 1.0 mm, and the extrusion piston downward pressure to 200 KN for forming processing.

[0032] Step 3: The first powder feeder moves at 400mm... 3 The metal powder is fed into the first powder feeding port 1 at a powder feeding rate of / min, and then output to the rod forming chamber through the powder mixing chamber. The heating temperature of the eddy current heater is set to 250℃. The heated metal powder is extruded into a rod shape (diameter of 20mm) under the pressure of the extrusion piston.

[0033] Step 4: The rod is further extruded into the hollow position of the stirring head. Following the parameters described above, the stirring head travels in a zigzag path to perform stirring and friction, simultaneously extruding and rotating the softened rod material outwards to diffuse and deposit it. A 2mm deposition layer is printed on the substrate surface through stirring and friction. After printing one layer, the stirring head is reset, and the above process is repeated until the metal layer reaches a thickness of 4mm.

[0034] Step 5: After printing on the metal substrate, change the material, clear the remaining printing material, and change the stirring head speed to 1000 r / min and the forging force to 250 kN. The first powder feeder operates at a speed of 50 mm. 3 The short carbon fiber particles are fed into the first powder feeding port 22 at a speed of / min, and the second powder feeder feeds at a speed of 450mm. 3The PEEK resin powder is fed into the second powder feeding port 23 at a powder feeding rate of / min. After the short fiber particles and PEEK powder are mixed evenly in the powder mixing chamber, they are conveyed to the rod forming chamber.

[0035] Step 6: Start the laser, set the laser heating temperature to 200℃, and repeat step 4 to print a layer of 10% short carbon fiber thermoplastic composite material.

[0036] Step 7: After printing one layer, reset the mixing head and change the powder feeding rate of the first powder feeder to 100mm. 3 / min, the powder feeding rate of the second powder feeder is 400mm 3 The printing process is repeated at a speed of / min to print a layer of 20% short carbon fiber thermoplastic composite material. This yields the printed gradient material.

[0037] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A metal / multi-gradient thermoplastic composite friction stir additive manufacturing system, characterized in that, The system includes a powder feeding system, an additive manufacturing apparatus, and a cooling system. The additive manufacturing apparatus (3) includes an eddy current heating device (31), a rod forming chamber (32), a rod forming channel (33), and a stirring head (34). The stirring head (34) has a hollow structure, and its internal cavity is the rod forming channel (33). The upper part of the rod forming channel (33) is connected to the lower part of the rod forming chamber (32), and the upper part of the rod forming chamber (32) is connected to the extrusion piston channel (36). The powder is output to the rod forming chamber through the powder input channel (30). (32) The eddy current heating device (31) surrounds the outside of the spherical rod forming chamber (32) and heats the powder fed into the rod forming chamber (32). The extrusion piston (1) extrudes the powder in the rod forming chamber (32) into the rod forming channel (33) inside the stirring head (34). Under the stirring friction extrusion of the stirring head (34), plastic deformation occurs. Under the stirring and upsetting action of the stirring head protrusion (35), the material is plastically softened and deposited on the substrate. The stirring head moves according to the set moving path to form a deposition layer on the substrate.It also includes a laser (4), which is clamped in front of the stirring head (34) and can heat the substrate in front of the stirring path at a temperature of 200-600℃; the cooling system includes a substrate (5), a processing cylinder (7), a lifting platform (6), an input valve (9), an output valve (8), and a diversion base (11); the lifting platform (6) is set in the processing cylinder (7), the diversion base (11) is set on the lifting platform (6), the substrate (5) is set on the diversion base (11), the coolant flows into the processing cylinder (7) through the input valve (9), and after the coolant in the processing cylinder (7) reaches a certain height, it flows into the bottom and side of the diversion base (11). The channel flows to the top of the diversion base (11) and flows out through the groove. The coolant then flows out from the output valve. The flow rate is controlled by the input and output solenoid valves to achieve the cooling and temperature control of the substrate (5) and the already formed stirring layer on the substrate. The powder feeding system includes a powder feeding device and a powder mixing device (2). The powder mixing device (2) includes a rotating device (20), a rotating rod (21), a first powder input port (22), a second powder input port (23), a diversion plate (24), a rolling bearing (25), a blade ring (26), a powder mixing inner chamber (27), a powder mixing outer chamber (28), and a powder output channel (29). The first powder input port ( 22) The second powder inlet (23) is located at the top of a cylindrical container. The interior of the cylindrical container is divided into two interconnected chambers: the upper chamber is the powder mixing inner chamber (27), and the lower chamber is the powder mixing outer chamber (28). A perforated guide plate (24) is installed at the top of the powder mixing inner chamber (27). A rolling bearing (25) is installed between the outside of the guide plate (24) and the inner wall of the powder mixing inner chamber (27). The center of the guide plate (24) is fixed on the rotating rod (21). Inside the powder mixing inner chamber (27), below the guide plate (24), a blade ring (26) is coaxially fixed on the rotating rod (21) with the guide plate (24). In the lower part of 27), inside the powder mixing outer chamber (28), a blade ring (26) is also provided, which is coaxially fixed on the rotating rod (21) with the guide plate (24). Under the drive of the rotating device (20), the rotating rod (21), the guide plate (24), and the two blade rings (26) rotate synchronously. The powder is fed into the first powder inlet (22) and the second powder inlet (23) by the powder feeder, and falls into the powder mixing inner chamber (27) by its own gravity through the hollow of the guide plate (24). Under the action of the rotation of the blade ring (26), it is mixed evenly and falls into the output channel (29) of the powder mixing outer chamber (28), and then output to the additive manufacturing device through the conduit (10).

2. The friction stir additive manufacturing system according to claim 1, characterized in that, The bottom and sides of the drainage base (11) have coolant inflow channels, and the side of the drainage base (11) that contacts the substrate has a groove; the lifting platform (6) controls the substrate (5) to move up and down, so as to realize the additive manufacturing of material stirring friction layer by layer.

3. The friction stir additive manufacturing system according to claim 1, characterized in that, The heating temperature range of the eddy current heating device is 0-400℃.

4. The method of the friction stir additive manufacturing system according to any one of claims 1-3, characterized in that, Includes the following steps: Step 1: Clamp the flow base onto the processing cylinder, fix the printing substrate on the base with a clamp, and use the lifting platform to bring the substrate to the printing position. The stirring head of the additive manufacturing system spindle contacts the substrate. Coolant is fed into the processing cylinder through the input valve. After the coolant in the processing cylinder reaches the lower end of the substrate through the flow base, the height of the coolant in the processing cylinder is maintained by the solenoid valve. The coolant flows out through the output valve. Step 2: The metal powder is fed into the powder feeding port of the outer mixing chamber by the powder feeder, falls into the inner mixing chamber by its own gravity, and is guided into the bottom output channel of the outer chamber through the inner chamber guide plate. The metal powder is then output to the upper chamber of the rod forming chamber through the conduit. Step 3: The eddy current heating device heats the metal powder for friction stir additive manufacturing: Under the pressure of the extrusion piston, a rod is formed in the lower chamber of the rod forming chamber. Under further extrusion, the rod reaches the position of the stirring head and the stirring shaft shoulder cavity. Under the action of stirring friction, axial forging force and extrusion force, plastic deformation occurs. The plastically softened material is deposited on the substrate by the stirring head. The stirring head forms a dense deposition layer on the substrate according to a certain moving path. Step 4: After completing one deposition layer, reset the stirring head and repeat steps 2 and 3. The metal rod is stirred and rubbed to deposit a metal layer of a certain height and thickness. After the metal substrate layer is printed, proceed to step 5. Step 5: Change the printing material and clear the printing residue. The first powder feeder feeds short fiber particles through the first powder input port, and the second powder feeder feeds thermoplastic resin powder through the second powder input port. Adjust the powder feeding rate to achieve the material ratio 1. Start the rotating device. The guide plate, blade ring and rotating rod rotate synchronously to mix the short fiber particles and thermoplastic resin powder evenly. Step 6: Activate the laser in front of the stirring head in the friction stir additive manufacturing process. The laser preheats the metal substrate in the direction of the stirring head's movement. Repeat the friction stir additive manufacturing process in Step 3 to form a short fiber thermoplastic composite material deposition layer with ratio 1. Step 7: Turn off the laser, repeat steps 5 and 6, adjust the ratio 1 in step 5 to ratio 2, and form a short fiber thermoplastic composite material deposition layer of ratio 2 on the thermoplastic composite material stirring layer of ratio 1; finally complete the friction stir additive manufacturing of multi-gradient thermoplastic composite material.

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