Friction stir additive manufacturing device and method capable of dynamically regulating and controlling gradient components

Abstract

The invention discloses a friction stir additive manufacturing device and method capable of dynamically regulating and controlling gradient components. The friction stir additive manufacturing device comprises a static shaft shoulder, a stirring probe, a feeding system and a heating control system. The feeding system comprises a first wire feeding mechanism, a second wire feeding mechanism and a wire feeding speed adjusting module, and the wire feeding speed of the first wire feeding mechanism and the wire feeding speed of the second wire feeding mechanism can be independently adjusted. Stable positive pressure is established in the stirring cabin by continuous positive thrust provided by the wire feeding system; meanwhile, local negative pressure is formed at the throat outlet through viscous pumping of the probe; the heating element plasticizes and flows the material. The'push-up and suction-down 'pressure field overcomes the flow resistance brought by the pin, and ensures that the material smoothly passes through the annular gap, is captured by the probe and is downwards conveyed to a deposition area. The plastic material is forced to repeatedly undergo a'segmentation-displacement-recombination 'mixing process in the flowing process through a streamline pin in the cabin.

Description

Technical Field

[0001] This invention relates to the field of solid-phase additive manufacturing technology, specifically to a stirring friction additive manufacturing apparatus and method with dynamically adjustable gradient composition, and in particular to an active mixing stirring friction deposition apparatus and method that can achieve online uniform mixing and composition gradient control of two materials. Background Technology

[0002] Friction stir deposition (FSD) is an advanced manufacturing process based on solid-state deformation. This technology uses a high-speed rotating stirring head to generate heat through friction with the metal raw material (bars, wires, or particles), causing the material to undergo intense plastic deformation in a thermoplastic state below its melting point, thus achieving layer-by-layer deposition. Due to its low processing temperature, it effectively avoids defects commonly found in melting-type additive manufacturing, such as hot cracking, porosity, and elemental segregation, making it particularly suitable for forming lightweight metals such as high-strength aluminum alloys and magnesium alloys.

[0003] With increasingly stringent performance requirements for components in fields such as aerospace and rail transportation, composite materials with compositional and functional gradients have become a research frontier. For example, aluminum / silicon carbide graded functional materials have been widely used in key components such as automotive engine pistons and aircraft landing gear. However, existing AFSD (Alternating Functional Composite) technology faces significant bottlenecks in achieving material gradient composites.

[0004] Currently, solutions for multi-material friction deposition mainly focus on the following areas: (1) Sequential deposition with dual stirring heads: As shown in patent CN119457399A, a rod feeding head and a wire filling head that are spatially separated are used for sequential processing. This method can only achieve macroscopic stacking or layered composite of materials, and cannot achieve uniform gradient mixing at the microscopic scale. In addition, the equipment is complex and bulky.

[0005] (2) Multi-channel alternating feeding: Composition changes are achieved by alternating feeding of different rods laterally. However, the material mixing in this scheme depends entirely on the later shearing of the stirring needle in the deposition zone. The plastic bodies of different materials only have simple physical contact in the early stage of convergence, resulting in poor mixing uniformity, low efficiency, and difficulty in achieving a smooth gradient interface.

[0006] (3) Prefabricated composite rods: The reinforcing phase material is filled into hollow rods, and the composite material is prepared by consuming the rods. Although this method is simple and easy to implement, the gradient composition is fixed once it is prefabricated and cannot be dynamically controlled during the deposition process, resulting in poor flexibility.

[0007] (4) Simple confluence feeding: Multiple feeding channels are opened on a single stirring head to allow different filaments to converge near the deposition point. In this method, the material does not undergo sufficient shearing and folding, resulting in problems such as uneven composition and weak interfacial bonding in the deposition layer, which seriously affects the performance of the component.

[0008] Therefore, existing technologies have shortcomings and need to be improved. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a stirring friction additive manufacturing apparatus and method with dynamically adjustable gradient composition.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: An active mixing agitation triboelectric deposition apparatus for gradient material fabrication includes a stationary shoulder, a stirring probe, a feeding system, and a heating control system. The stationary shoulder is a hollow cylinder, with its lower part connected to an annular premixing chamber; the annular premixing chamber surrounds the stirring probe. The annular premixing chamber comprises, from top to bottom, a mixing section, a funnel transition section, and a throat straight section. Static mixing elements are installed on the inner wall of the mixing section. The funnel transition section smoothly transitions the cylindrical cavity to the throat straight section, and an annular gap is provided at the intersection of the funnel transition section and the throat straight section. The throat straight section is a cylindrical section of equal diameter. The mixing section, funnel transition section, and throat straight section are coaxially arranged, and their common axis coincides with the rotation axis of the stirring probe. The entire mixing chamber surrounds the stirring probe axially, forming a closed, continuous, and axisymmetric annular flow channel. The stirring probe passes through the central through hole of the stationary shoulder, and its top working section is located directly below the outlet of the annular premixing mixing chamber; the top working section of the stirring probe is located directly below the annular gap; the top working section of the stirring probe is machined with a double-ended shallow thread. The feeding system includes a first wire feeding mechanism, a second wire feeding mechanism, and a wire feeding speed adjustment module. The first and second wire feeding mechanisms are respectively connected to two feeding channels. The wire feeding speeds of the first and second wire feeding mechanisms can be adjusted independently. The wire feeding speed adjustment module is used to adjust the wire feeding speed ratio of the first and second wire feeding mechanisms in real time, so that the composition of the deposited layer changes linearly, stepwise, or curvilinearly along the deposition path or layer height. Linear change: the wire feeding speed ratio increases or decreases linearly with the travel distance; Stepwise change: the wire feeding speed ratio changes abruptly at a specific position; Curvilinear change: the wire feeding speed ratio changes according to a preset curve function.

[0011] The heating control system includes an active heating module and a temperature sensor integrated into the outer wall of the annular premixing chamber.

[0012] The device described above has two symmetrical feed channels on the side wall of the mixing section of the annular premixing chamber, used to introduce the first and second metal wires, respectively. Each feed channel is a straight hole with a diameter of 3.2 mm, arranged tangentially to the side wall of the mixing section. Its inlet is located on the outer surface of the side wall of the mixing section, and its outlet is tangential to the inner wall of the mixing section (301). The feed direction is consistent with the rotation direction of the stirring probe (2).

[0013] The described device uses streamlined wing pins fixed to the inner wall of the mixing section as static mixing elements. Their geometric characteristics are: chord length 7.0 mm, maximum thickness 2.2 mm (located approximately 2.3 mm from the leading edge), smooth transition at the leading edge (radius 0.5 mm), sharp trailing edge (angle 15°), and radial length extending 8 mm from the bulkhead. The pins consist of two layers, with four pins in each layer, evenly distributed circumferentially, and staggered at 45° intervals between layers.

[0014] The static mixing element of the device is a streamlined wing pin with the following geometric characteristics: chord length 5-10mm, maximum thickness 1.5-3.0mm, smooth transition at the leading edge, and sharp trailing edge; the streamlined wing pins are arranged in 2-3 layers on the inner wall of the mixing section, with adjacent layers staggered by 30-60° in the circumferential direction.

[0015] In the aforementioned device, the inner diameter of the straight section of the throat is 0.4-1.0 mm larger than the diameter of the stirring probe.

[0016] In the aforementioned device, the width of the annular gap is 0.2-0.5 mm.

[0017] The aforementioned device features a working section of the stirring probe equipped with a double-ended shallow thread or axial ridge to enhance the pumping effect on plastic materials. The double-ended shallow thread refers to a thread structure with two thread starts and a shallow thread depth (0.3 mm). "Double-ended" means that two parallel helical lines rotate around the axis of rotation, providing greater pumping thrust within a limited axial length; "shallow" means that the ratio of the thread depth (0.3 mm) to the stirring probe diameter (10 mm) is 0.03, significantly smaller than that of standard threads (typically 0.1-0.2), to avoid stress concentration and material retention at the thread root.

[0018] The device has a feed channel with a diameter of 2.5-4.0 mm and an inclination angle of 30-60° to the horizontal plane, and its outlet cuts into the side wall of the upper mixing section of the annular premixing chamber.

[0019] The active heating module of the device is selected from induction coils or resistance heaters and is used to heat the inner wall of the annular premixing mixing chamber to 300-550°C.

[0020] A gradient material stirring friction deposition method using any one of the apparatuses described herein includes the following steps: S1: Load the first metal wire and the second metal wire into two independent wire feeding mechanisms respectively; start the stirring spindle to make the stirring probe rotate; turn on the active heating module to preheat the annular premixing stirring chamber to the set temperature; S2: Control the stirring probe to descend so that the stirring needle penetrates the substrate; start the wire feeding mechanism to feed the metal wire into the annular premixing stirring chamber at the set initial wire feeding speed ratio. S3: During the movement of the stirring probe along the preset path, the wire feeding speed ratio of the two wire feeding mechanisms is adjusted in real time by the wire feeding speed adjustment module, so that the composition of the deposition layer changes linearly, stepwise, or curvilinearly along the deposition path or layer height; linear change: the wire feeding speed ratio increases or decreases linearly with the travel distance; stepwise change: the wire feeding speed ratio changes abruptly at a specific position; curvilinear change: the wire feeding speed ratio changes according to a preset curve function. S4: After completing one layer of deposition, raise the stirring probe by one layer height and repeat steps S2-S3 to deposit the next layer; S5: After all deposition is complete, stop wire feeding, turn off the active heating module, raise the stirring probe and keep it rotating to empty the remaining material in the annular premixing chamber.

[0021] In the method described in step S1, the set temperature is 50-150°C lower than the lower solidus temperature of the first and second metal wires.

[0022] In the method described in step S4, during multi-layer deposition, the gradient direction of each layer is selected from one of the following: unidirectional, anti-directional, or cross-directional.

[0023] In the method described, the first metal wire and the second metal wire are selected from any two identical or different materials selected from aluminum alloy, magnesium alloy, copper alloy, titanium alloy, aluminum-based composite material, and magnesium-based composite material.

[0024] A gradient composite material component prepared by any of the methods described herein, wherein the component has a continuously varying composition distribution along a specified direction, the composition variation curve matches a preset gradient program, and the maximum deviation is less than ±3 vol.

[0025] The gradient composite material component has a microstructure in which different materials are evenly distributed without obvious agglomeration or segregation, and a mechanically interlocking structure is formed at the interface.

[0026] The continuous positive thrust provided by the wire feeding mechanism establishes a stable positive pressure within the mixing chamber; simultaneously, the viscous pumping of the probe creates a localized negative pressure at the throat outlet; and heating elements further plasticize and flow the material. This "push-pull" pressure field overcomes the flow resistance introduced by the pins, ensuring the material smoothly passes through the 0.3mm annular gap, is captured by the probe, and transported downwards to the deposition zone. Through the streamlined pins within the chamber, the plastic material is forced to repeatedly undergo a "splitting-displacement-reorganization" mixing process during flow. This design transforms the mixing function from "passive dependence in the later stages" to "active intervention in the early stages," achieving precise control over the material mixing process.

[0027] Compared with the prior art, the present invention has the following significant advantages: 1. Achieved true in-situ premixing By employing a design that combines an annular premixing chamber with a streamlined wing pin array, the uniform mixing process of the two materials is pre-emptively and proactively initiated, overcoming the limitation of traditional AFSD systems that rely solely on final mixing. The pins force the material flow to repeatedly divide, fold, and recombine in three-dimensional space, achieving uniform mixing at the microscale. This results in a mixing uniformity that is over 80% higher than that of traditional dual-channel feeding systems.

[0028] 2. Gradient components are precisely controllable. The combination of independent dual-wire servo feeding and a wire feed speed adjustment module enables precise programming of composition along the deposition path or layer height. The minimum gradient resolution can reach 0.1 mm, and the composition control accuracy is better than ±2 vol%, enabling the preparation of gradient composite materials with a continuous transition from 0% to 100%.

[0029] 3. High process stability The active heating module ensures a uniform and stable temperature field within the mixing chamber, resolving the issue of uneven plasticization caused by reliance on residual friction heat. The shallow thread design at the tip of the stirring probe, combined with the annular precision clearance, creates a stable "viscous pumping" effect, ensuring smooth material transport from the mixing chamber to the deposition zone and avoiding blockages and flow dead zones.

[0030] 4. Eliminate dead zones in the flow. The funnel transition section adopts a large-curvature continuous curved surface design (contraction angle of approximately 74°), avoiding corner stagnation that is prone to occur in traditional conical funnels; the circumferentially symmetrical design of the annular outlet ensures circumferential uniformity of material discharge; and the low-resistance design of the streamlined pins facilitates smooth material flow. CFD simulations show that the flow dead zone volume of this design is less than 2% of the total cavity volume. Attached Figure Description

[0031] Figure 1 This is a schematic cross-sectional view of the overall main structure of the device of the present invention; Figure 2A schematic diagram of the staggered arrangement of pins on the inner wall of the mixing chamber; Figure 3 This is a cross-sectional view of the premixing tank; Figure 4 Schematic diagram of material flow being divided by pins 1-Stationary shoulder, 101-Feed channel A, 102-Feed channel B, 103-Heating element mounting slot; 2-Stirring probe; 3-Premixing mixing chamber, 301-Mixing section, 302-Functional transition section, 303-Throat straight section, 304-Annular precision gap; 4-Streamlined wing pin; 5-Substrate; 6-Deposited layer. Detailed Implementation

[0032] refer to Figure 1-4 A friction stir additive manufacturing apparatus with dynamically adjustable gradient composition includes a stationary shoulder, a stirring probe, a feeding system, and a heating control system.

[0033] The stationary shoulder is a hollow cylinder, with an annular premixing chamber connected to its lower part; the annular premixing chamber surrounds the stirring probe. The outer diameter of the stationary shoulder is 80 mm, and the total height is 45-50 mm.

[0034] The annular premixing chamber has an inner diameter of 46 mm and a total height of 25 mm.

[0035] The annular premixing chamber comprises, from top to bottom: Mixing section: 15mm high, with static mixing elements installed on the inner wall of the mixing section; Funnel transition section: 7mm in height, used to smoothly transition the cylindrical cavity to the straight throat section. An annular gap is provided at the intersection of the funnel transition section and the straight throat section. Straight section of the throat: 3mm in height, is a cylindrical section of equal diameter, with an inner diameter of 10.6mm.

[0036] The mixing section, funnel transition section, and throat straight section are coaxially arranged, with their common axis coinciding with the rotation axis of the stirring probe. The entire stirring chamber surrounds the stirring probe axially, forming a closed, continuous, axisymmetric annular flow channel.

[0037] The static mixing element is a streamlined wing pin fixed to the inner wall of the mixing section. Its geometric characteristics are: chord length 7.0 mm, maximum thickness 2.2 mm (located at approximately 2.3 mm from the leading edge), smooth transition at the leading edge (radius 0.5 mm), sharp trailing edge (angle 15°), and radial length extending 8 mm from the bulkhead. The pins consist of two layers, with four pins in each layer, evenly distributed along the circumference, and staggered by 45° between layers in the circumferential direction.

[0038] The continuous positive thrust provided by the wire feeding mechanism establishes a stable positive pressure within the mixing chamber; simultaneously, the viscous pumping of the probe creates a localized negative pressure at the throat outlet; and heating elements further plasticize and flow the material. This "push-pull" pressure field overcomes the flow resistance introduced by the pins, ensuring the material smoothly passes through the 0.3mm annular gap, is captured by the probe, and transported downwards to the deposition zone. Through the streamlined pins within the chamber, the plastic material is forced to repeatedly undergo a "splitting-displacement-reorganization" mixing process during flow. This design transforms the mixing function from "passive dependence in the later stages" to "active intervention in the early stages," achieving precise control over the material mixing process.

[0039] The annular premixing chamber has two symmetrically arranged feed channels on the sidewall of the mixing section, used to introduce the first and second metal wires, respectively. Each feed channel is a straight hole with a diameter of 3.2 mm, arranged tangentially to the sidewall of the mixing section. Its inlet is located on the outer surface of the sidewall of the mixing section, and its outlet is tangential to the inner wall of the mixing section 301. The feed direction is consistent with the rotation direction of the stirring probe 2.

[0040] The stationary shoulder also integrates a heating element mounting slot. This mounting slot is located on the outer wall of the mixing chamber and is used to install induction coils or resistance heaters.

[0041] The stirring probe is a long rod with a diameter of 10.0 mm, passing through the central through-hole of the stationary shoulder. The working section at the tip of the stirring probe is located directly below the annular gap.

[0042] The tip of the stirring probe has been specially modified: a shallow thread is machined on the 4mm long working section at the tip, with 2 thread starts, a pitch of 2mm, and a thread depth of 0.3mm.

[0043] The bottom working section of the stirring probe is equipped with a stirring pin, which is used to contact the substrate and generate frictional heat.

[0044] The feeding system includes a first wire feeding mechanism, a second wire feeding mechanism, and a wire feeding speed adjustment module, which are connected to two feeding channels respectively. The wire feeding mechanism is a precision wire feeder driven by a servo motor, and its wire feeding speed is independently adjustable, with an adjustment range of 0-5000 mm / min. The wire feeding speed adjustment module is used to adjust the wire feeding speed ratio of the first and second wire feeding mechanisms in real time, so that the composition of the deposited layer changes linearly, stepwise, or curvilinearly along the deposition path or layer height; linear change: the wire feeding speed ratio increases or decreases linearly with the travel distance; stepwise change: the wire feeding speed ratio changes abruptly at a specific position; curvilinear change: the wire feeding speed ratio changes according to a preset curve function.

[0045] The heating control system includes: Active heating module: It is an induction coil or resistance heater integrated on the outer wall of the mixing chamber, with a heating power of 1-3kW, which can heat the inner wall of the mixing chamber to 300-500℃; Temperature sensor: A thermocouple embedded in the wall of the mixing chamber, used to monitor the temperature inside the chamber in real time; Controller: Connects to the active heating module and temperature sensor to achieve closed-loop temperature control.

[0046] The present invention also provides a gradient material stirring friction deposition method using the above-described apparatus, comprising the following steps: Step S1: Equipment preparation and preheating. Load the first metal wire and the second metal wire into the first wire feeding mechanism and the second wire feeding mechanism respectively; start the stirring spindle to make the stirring probe rotate at a set speed; turn on the active heating module to preheat the stirring chamber to a set temperature, which is 50-150℃ lower than the solidus temperature of the first metal wire and the second metal wire.

[0047] Step S2: Initial Deposition. Control the descent of the stirring probe to penetrate the substrate to a predetermined depth; simultaneously activate the first wire feeding mechanism and / or the second wire feeding mechanism, and the wire feeding speed adjustment module feeds the metal wire into the mixing section of the annular premixing stirring chamber at a set initial wire feeding speed ratio; after the wire comes into contact with the high-temperature chamber wall and pins in the mixing section, it is rapidly plasticized and extruded from the annular gap outlet under the viscous pumping action of the rotating stirring probe, depositing on the substrate to form an initial deposition layer.

[0048] Step S3: Gradient Deposition. During the movement of the stirring probe along the preset path, the wire feeding speed ratio of the first and second wire feeding mechanisms is adjusted in real time via the wire feeding speed adjustment module. This module allows the composition of the deposited layer to change linearly, stepwise, or curvilinearly along the deposition path or layer height. Linear change: The wire feeding speed ratio increases or decreases linearly with the travel distance. Stepwise change: The wire feeding speed ratio changes abruptly at a specific location. Curvilinear change: The wire feeding speed ratio changes according to a preset curve function. Step S4: Multi-Layer Deposition. After completing one layer of deposition, the stirring probe is raised by one layer height, and steps S2-S3 are repeated to deposit the next layer. During multi-layer deposition, the gradient direction of each layer can be selected from one of the following: unidirectional, anti-unidirectional, or intersecting.

[0049] Step S5: End deposition. After all deposition is complete, stop wire feeding, turn off the active heating module, raise the stirring probe, keep it rotating for a period of time to empty the remaining material in the stirring chamber, and then stop rotating.

[0050] The present invention will be described in detail below with reference to specific embodiments.

[0051] Example 1: Preparation of Al-SiC Functionally Graded Composite Materials This embodiment uses the preparation of Al-SiC functionally graded composite materials as an example to illustrate the specific implementation process of the present invention.

[0052] 1. Device Configuration Adopting such Figure 1 The active mixing agitation friction deposition apparatus shown has the following specific parameters: (1) Static shoulder 1: outer diameter 80mm, total height 48mm, material is H13 hot work die steel. Internally integrated premixing mixing chamber 3, mixing chamber inner diameter 46mm, total height 25mm (of which mixing section 301 is 15mm high, funnel transition section 302 is 7mm high, and throat straight section 303 is 3mm high). The inner wall of the mixing chamber and the surface of the pins are mirror polished.

[0053] (2) Streamlined wing pins: 4, chord length 7.0 mm, maximum thickness 2.2 mm, leading edge radius 0.5 mm, trailing edge angle 15°, extending 8 mm from the bulkhead. There are 2 layers, 4 pins per layer, staggered at 45° between layers (e.g., Figure 2 (As shown).

[0054] (3) Stirring probe 2: Diameter 10.0 mm, material is tungsten-based heavy alloy. The top 4 mm section is machined with double-ended shallow thread 201, pitch 2 mm, thread depth 0.3 mm. The straight section of the throat has an inner diameter of 10.6 mm, and a single-sided 0.3 mm annular precision gap 304 is set at the intersection of the funnel transition section and the straight section of the throat.

[0055] (4) Feeding channels: Two feeding channels (101, 102) with a diameter of 3.2 mm, inclined at a 45° angle to the horizontal plane, with the outlet cutting into the upper part of the mixing section of the mixing chamber. Figure 3 ).

[0056] (5) Heating system: The outer wall of the mixing chamber is integrated with a 2kW induction heating coil, equipped with a K-type thermocouple and a PID controller.

[0057] 2. Material Preparation First metal wire: pure aluminum wire (grade 1060), diameter 3.0mm; Second metal wire: aluminum-based composite wire, with a matrix of 1060 aluminum and containing 20 vol% SiC particles (particle size 5-10 μm) with a diameter of 3.0 mm; Substrate: 1060 aluminum alloy plate, size 200mm×100mm×10mm. Before use, the oxide layer is removed by sanding and the oil stains are cleaned with acetone.

[0058] 3. Process parameter settings Stirring probe speed: 800 rpm; Preheating temperature of the mixing chamber: 420℃; Deposition layer height: 1.5 mm / layer; Travel speed: 60 mm / min; Wire feeding speed range: 0-3000 mm / min; Gradient procedure: On a 100mm deposition path, the feed rate of the second metal wire (containing SiC) is linearly increased from 0 to 3000 mm / min, while the feed rate of the first metal wire (pure aluminum) is linearly decreased from 3000 mm / min to 0, i.e., the SiC volume fraction is linearly increased from 0% to 20%.

[0059] The aluminum-based composite filaments used in the examples can be prepared using one of the following methods: (1) Commercially available aluminum-based composite welding wire: such as Al-SiC welding wire (SiC content 5-15%) used for arc additive manufacturing, can be used directly as the second wire material; (2) Branch feeding method: The first wire feeding mechanism conveys pure aluminum wire, and the second feeding mechanism is a micro powder feeder that directly conveys SiC reinforced particles, realizing in-situ compounding and mixing in the premixing chamber.

[0060] The forced mixing chamber of the present invention has good powder dispersion ability and is particularly suitable for scheme (2), which can realize the preparation of gradient composite materials without relying on commercially available composite filaments.

[0061] 4. Operating Procedures Step 1: Preheat the equipment Start the stirring spindle and rotate the stirring probe at 800 rpm. Turn on the induction heating and preheat the stirring chamber to 420°C (at this temperature, the rheological stress of the material is greatly reduced, exhibiting typical viscoplastic fluid characteristics, and can undergo significant plastic flow under mechanical force), and keep it at this temperature for 5 minutes to ensure uniform temperature.

[0062] Step 2: Initial Deposition The stirring probe is lowered to penetrate the substrate by 0.3 mm. The first and second wire feeding mechanisms are activated, with initial wire feeding speeds set as follows: 3000 mm / min for the first wire and 0 mm / min for the second wire. The pure aluminum wire enters the stirring chamber through the feed channel 101, and rapidly plasticizes upon contact with the high-temperature chamber walls and pins. Under the viscous pumping action of the stirring probe, it is extruded from the annular gap and deposited on the substrate to form the initial deposition layer.

[0063] Step 3: Gradient deposition Start the table feed at a speed of 60 mm / min. Simultaneously activate the gradient control program: as the travel distance x increases from 0 to 100 mm, the second filament feed speed increases linearly by v2 = 30x (mm / min), while the first filament feed speed decreases linearly by v1 = 3000 - 30x (mm / min). The two materials are repeatedly sheared, divided, and mixed by streamlined pins within the mixing chamber, forming a plastic mixture with continuously increasing SiC content. This mixture is then extruded from the annular slit and deposited to form a gradient layer.

[0064] Step 4: Multi-layer deposition After completing the first layer deposition, raise the stirring probe by 1.5 mm and repeat steps 2-3 to deposit the second layer. A total of 10 layers are deposited, with the gradient direction of each layer being the same.

[0065] Step 5: End sedimentation After all deposition is complete, stop wire feeding, turn off induction heating, raise the stirring probe by 5 mm, keep it rotating for 30 seconds to empty the remaining material in the stirring chamber, and then stop rotating.

[0066] 5. Results The mixing chamber temperature of 420℃ puts the aluminum material in a thermoplastic state (approximately 0.72Tm), giving it good fluidity.

[0067] The flow and separation of materials within the stirred chamber involves two coupled motions driven by the rotation of the stirring probe within the stationary chamber: Circumferential motion: The viscous drag effect on the probe surface causes the material to rotate around the probe axis and flow in a circular direction.

[0068] Axial motion: The shallow threaded structure at the tip of the probe generates a continuous downward pumping effect on the material, causing the material to move slowly downward while rotating.

[0069] As the material moves downwards, it passes sequentially through two layers of staggered, streamlined wing pins, such as... Figure 4 As shown, in the first layer (4 pins): as the material flows through the first layer of 4 pins, the flow is split into two streams at each pin. After passing through the first layer of 4 pins, one stream of material is split into 2. 4 =16 strands. Interlayer transfer: The 16 strands of material, after being divided, continue to move downwards while rotating, entering the second layer of pin areas. Second layer (4 pins, offset from the first layer by 45°): As the 16 strands of material flow through the 4 pins in the second layer, each strand is again divided by each pin. After passing through the 4 pins in the second layer, the 16 strands of material are further divided into 16×2 4=256 streams. Ultimately, the originally single mixed material stream was divided into 256 micro-streams, which are arranged alternately at the microscale to achieve uniform mixing of the two materials. Subsequently, the uniformly mixed material enters the deposition zone from the annular gap outlet.

[0070] A 0.3 mm annular gap generates sufficient shear stress at 800 rpm, ensuring effective material pumping. The linear change in wire feed speed directly corresponds to a linear change in SiC content, resulting in high precision in composition control. Therefore, this embodiment successfully prepares Al-SiC functional graded composite materials with a continuously linear SiC content ranging from 0% to 20%, exhibiting uniform microstructure and good interfacial bonding.

[0071] 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. An active mixing and stirring triboelectric deposition apparatus for gradient material fabrication, characterized in that, Includes a stationary shoulder, stirring probe, feeding system, and heating control system; The stationary shoulder is a hollow cylinder, with its lower part connected to an annular premixing chamber; the annular premixing chamber surrounds the stirring probe. The annular premixing chamber comprises, from top to bottom, a mixing section, a funnel transition section, and a throat straight section. Static mixing elements are installed on the inner wall of the mixing section. The funnel transition section smoothly transitions the cylindrical cavity to the throat straight section, and an annular gap is provided at the intersection of the funnel transition section and the throat straight section. The throat straight section is a cylindrical section of equal diameter. The mixing section, funnel transition section, and throat straight section are coaxially arranged, and their common axis coincides with the rotation axis of the stirring probe. The entire mixing chamber surrounds the stirring probe axially, forming a closed, continuous, and axisymmetric annular flow channel. The stirring probe passes through the central through-hole of the stationary shoulder, and its top working section is located directly below the outlet of the annular premixing mixing chamber; the top working section of the stirring probe is located directly below the annular gap; the working section of the stirring probe is machined with a double-ended shallow thread. The feeding system includes a first wire feeding mechanism, a second wire feeding mechanism, and a wire feeding speed adjustment module. The first wire feeding mechanism and the second wire feeding mechanism are respectively connected to two feeding channels. The wire feeding speeds of the first wire feeding mechanism and the second wire feeding mechanism can be adjusted independently. The wire feeding speed adjustment module is used to adjust the wire feeding speed ratio of the first wire feeding mechanism and the second wire feeding mechanism in real time, so that the composition of the deposited layer can change linearly, stepwise, or curvilinearly along the deposition path or layer height; linear change: the wire feeding speed ratio increases or decreases linearly with the travel distance; stepwise change: the wire feeding speed ratio changes stepwise at a specific position. Curve variation: The wire feeding speed ratio varies according to a preset curve function; The heating control system includes an active heating module and a temperature sensor integrated into the outer wall of the annular premixing chamber.

2. The apparatus according to claim 1, characterized in that, The annular premixing mixing chamber has two symmetrically opened feeding channels on the side wall of the mixing section, which are used to introduce the first metal wire and the second metal wire respectively; the feeding channels are straight holes with a diameter of 3.2 mm, which are arranged along the tangent direction of the side wall of the mixing section. Its inlet is located on the outer surface of the side wall of the mixing section, and its outlet is tangent to the inner wall of the mixing section (301); the feeding direction is consistent with the rotation direction of the stirring probe (2).

3. The apparatus according to claim 1, characterized in that, The static mixing element is a streamlined wing pin fixed to the inner wall of the mixing section. Its geometric characteristics are: chord length 5-10mm, maximum thickness 1.5-3.0mm, smooth transition at the leading edge, and sharp trailing edge. The streamlined wing pins are arranged in 2-3 layers on the inner wall of the mixing section, with adjacent layers staggered by 30-60° in the circumferential direction.

4. The apparatus according to claim 1, characterized in that, The inner diameter of the straight section of the throat is 0.4-1.0 mm larger than the diameter of the stirring probe.

5. The apparatus according to claim 1, characterized in that, The width of the annular gap is 0.2-0.5 mm.

6. The apparatus according to claim 1, characterized in that, The working section of the stirring probe is provided with a double-ended shallow thread or an axial protrusion to enhance the pumping effect on plastic materials; the double-ended shallow thread refers to a thread structure with two thread starts and a shallow thread depth, and "double-ended" means that two helical lines rotate in parallel around the axis of rotation.

7. The apparatus according to claim 1, characterized in that, The feed channel has a diameter of 2.5-4.0 mm and is inclined at an angle of 30-60° to the horizontal plane. Its outlet cuts into the side wall of the upper mixing section of the annular premixing chamber.

8. The apparatus according to claim 1, characterized in that, The active heating module is selected from induction coils or resistance heaters and is used to heat the inner wall of the annular premixing mixing chamber to 300-550°C.

9. A gradient material stirring triboelectric deposition method using the apparatus according to any one of claims 1-8, characterized in that, Includes the following steps: S1: Load the first metal wire and the second metal wire into two independent wire feeding mechanisms respectively; Start the stirring spindle to rotate the stirring probe; turn on the active heating module to preheat the annular premixing chamber to the set temperature; S2: Control the stirring probe to descend, so that the stirring needle penetrates the substrate; Start the wire feeding mechanism to feed the metal wire into the annular premixing chamber at the set initial wire feeding speed ratio; S3: During the movement of the stirring probe along the preset path, the wire feeding speed ratio of the two wire feeding mechanisms is adjusted in real time by the wire feeding speed adjustment module, so that the composition of the deposited layer changes linearly, stepwise, or curvilinearly along the deposition path or layer height; linear change: the wire feeding speed ratio increases or decreases linearly with the travel distance; stepwise change: the wire feeding speed ratio changes stepwise at a specific position. Curve variation: The wire feeding speed ratio varies according to a preset curve function; S4: After completing one layer of deposition, raise the stirring probe by one layer height and repeat steps S2-S3 to deposit the next layer; S5: After all deposition is complete, stop wire feeding, turn off the active heating module, raise the stirring probe and keep it rotating to empty the remaining material in the annular premixing chamber.

10. The method according to claim 9, characterized in that, The set temperature in step S1 is 50-150°C lower than the lower solidus temperature of the first and second metal wires.

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