In-situ stick-making-friction stir continuous additive manufacturing apparatus based on multi-stage thermal plasticization of rotational friction

Abstract

The application provides a kind of in-situ stick-making-friction stirring continuous additive manufacturing equipment based on rotary friction multistage thermoplastic, including extrusion container and needleless friction stirring device, with metal powder and / or metal scrap, particle as raw material, pre-pressed into pre-pressed blank by pre-pressing and sent into extrusion container, axial pressure is applied to extrude, while the bottom is stirred by needleless friction stirring device, pre-pressed blank is plasticized under the action of axial pressure and rotation, thermoplastic fluid flows to the center mold of needleless friction stirring device and extrudes stick, and the stick is plastically deformed under the action of friction stirring additive manufacturing to be deposited into shape. Thus, heat is generated by the composite friction of the needleless stirring tool, the stick is extruded and plastically deformed in-situ, and the stick is deposited by friction stirring, realizing continuous thermoplasticization of particle pre-pressed blank, extrusion of stick and friction stirring deposition of additive thin-walled structure, seamless connection of full-process continuous strong plastic deformation, solving the problem of stability of fine stick stirring additive forming and control of thin-walled size precision.

Description

Technical Field

[0001] This invention relates to the field of solid-phase additive manufacturing technology, and more specifically to an in-situ rod-stirring friction continuous additive manufacturing apparatus based on multi-stage thermoplasticization of rotational friction. Background Technology

[0002] Developing integrated, large-scale, and functionally integrated core structures, and innovating equipment design concepts, are important ways to meet the performance requirements of large and complex components. However, structural innovation, while enabling lightweighting and high performance, also presents new challenges to manufacturing. The limitations of traditional manufacturing become more apparent. For example, ultra-large integrated fuselage structures, integral frame beam structures, engine exhaust nozzles, and cabins cannot be integrally formed, exacerbating the conflict between design and manufacturing. Furthermore, the widespread use of high-strength aluminum alloys such as the 2000 series, 7000 series, and aluminum-lithium alloys further increases manufacturing difficulty. Current manufacturing methods such as "casting + machining + welding or riveting" or "forging + machining + welding or riveting" restrict structural efficiency. At the same time, casting, welding, and metallurgical defects, numerous processes, complex techniques, mold dependence, and material utilization all create numerous bottlenecks in structural realization. Therefore, it is urgent to focus on model-innovative structural development and develop new high-efficiency, high-performance, high-quality, and low-cost manufacturing technologies for high-strength aluminum alloys.

[0003] Additive manufacturing, with its advantages of layer-by-layer design and manufacturing, has been widely applied in engineering. There are many types of metal additive manufacturing. Selective laser melting (SLM), laser melting deposition (LDM), and wireless arc welding (WAAM) have significant advantages in manufacturing complex and precision structures and integrated structures. However, their laser additive melting and solidification processes result in large energy accumulation during cyclic deposition, leading to coarse metallurgical structures and significant differences in strengthening phases and microstructure compared to traditional manufacturing methods. This is especially true for wrought aluminum alloys, which exhibit significant porosity and thermal cracking, and their mechanical properties are difficult to meet service requirements, thus limiting their application in load-bearing structural engineering.

[0004] Currently, friction stir solid-state additive manufacturing, based on the principle of friction stir welding / processing (FSW / P), eliminates the need for melting. Deposition is achieved through strong plastic deformation via friction stir, resulting in a significant grain refinement effect and suppressing defects such as porosity. This provides a new approach for additive manufacturing of aluminum alloy structural components. The raw materials for friction stir solid-state additive manufacturing include rods, wires, and powder particles. However, regardless of the material form, when depositing thin-walled structures (wall thickness ≤ 20 mm), the required wall thickness is difficult to achieve through deposition due to limitations in the deposition width. For example, in bar-feed systems, the bar acts as the main source of frictional heat, directly rubbing against the substrate. After thermoplasticization, it is deposited under the constraint of the shoulder. Therefore, the shoulder of the stirring head is not suitable for the deposition width. To accommodate the size of the stirring head shoulder, only filament-feed or powder-feed systems can be used. However, filaments need to be sheared and crushed into metal particles by a spiral conveyor structure and then continuously conveyed downwards. The spiral conveyor structure continuously compacts and thermoplasticizes the metal particles, ultimately depositing the thermoplastic material onto the substrate. The large size of the spiral rod results in a large shoulder size, making it impossible to fabricate thin-walled complex structures. With powder-feed systems, direct feeding is hindered by the loose nature of the powder raw material, leading to easy splashing and insufficient plasticization. This results in a poor surface quality, insufficient densification, and weak interfacial bonding in the deposited layer. If a rotating screw tool is used to apply frictional extrusion to the metal powder to fully plasticize it, the large size of the spiral rod again results in a large shoulder size, making it impossible to fabricate thin-walled complex structures. Summary of the Invention

[0005] The purpose of this invention is to address the problem that existing friction stir additive manufacturing methods are difficult to use for fabricating thin-walled complex structural parts. This invention provides a coaxial friction stir continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotating particles. Through a continuous process of rotational friction plasticization, in-situ extrusion rod forming, and synchronous stirring deposition, this invention overcomes the limitations of friction stir additive manufacturing for thin-walled parts.

[0006] According to a first aspect of the present invention, an in-situ rod-stirring friction continuous additive manufacturing apparatus based on multi-stage thermoplasticization of rotational friction is provided, comprising an extrusion container and a needleless friction stirring device; the needleless friction stirring device includes a needleless friction stirring head capable of being driven to rotate at high speed to perform additive processing through friction stirring.

[0007] The extrusion container has a through cavity for placing a pre-pressed billet; the pre-pressed billet refers to a billet block with a certain shape and thickness obtained by pre-pressing metal scraps, particles, or powder; the extrusion container is provided with an extrusion rod for applying axial pressure to the pre-pressed billet placed in the cavity of the extrusion container to cause it to plasticize and generate a thermoplastic fluid.

[0008] The needle-free friction stir machining head has a spindle connecting section and a shoulder; the side of the shoulder facing the substrate or deposited layer serves as the working end face; the end of the spindle connecting section away from the shoulder is connected to the lower end of the extrusion container via a rolling bearing, and the outer ring and inner ring of the rolling bearing are rigidly connected to the extrusion container and the friction stir machining head, respectively, so that the friction stir machining head can rotate freely around the axis and constrain the extrusion container and the friction stir machining head to remain relatively stationary;

[0009] The end of the main shaft connecting section away from the shoulder is defined as the connecting end. The end face of the connecting end forms a contact surface that directly engages with the lower end of the extrusion container. During the rotation of the needleless stirring friction device, the contact surface directly contacts and rubs against the pre-compressed billet contained in the extrusion container.

[0010] The needle-free friction stir processing head has a through hole running vertically through the inside. The through hole is located at the axial center of the friction stir processing head and is used to form the central mold for extruding rods.

[0011] In this process, the pre-pressed blank in the cavity is extruded by the extrusion rod. The needle-free friction stirring head is driven to rotate and apply rotational friction to the pre-pressed blank. Combined with the axial pressure P1 applied by the extrusion rod, the pre-pressed blank is plasticized by rotation under the action of rotation and axial pressure. Under the action of axial pressure, the thermoplastic fluid flows into the through hole to form an extruded bar, realizing in-situ extrusion bar making and obtaining thermoplasticized extruded metal bar.

[0012] The extruded metal rod extends to the shoulder of the needleless friction stir processing head under axial pressure, and performs continuous friction stir additive manufacturing through the working end face of the shoulder when the friction stir processing head is driven to rotate, so that the extruded metal rod is deposited layer by layer on the substrate until the component is formed, realizing synchronous friction stir additive manufacturing.

[0013] As an optional embodiment, the inner ring of the rolling bearing is coaxially arranged with the connecting end, and the outer circumference of the connecting end is sleeved and fixed to the inner circumferential surface of the inner ring; the outer ring of the rolling bearing is assembled to the inner wall of the extrusion container, the two are coaxially arranged and the outer circumferential surface of the outer ring is fitted and fixed to the inner wall of the extrusion container.

[0014] As an optional embodiment, the contact surface is provided with a friction part to increase the friction between the contact surface and the pre-pressed blank.

[0015] As an optional embodiment, the friction part includes a spiral groove.

[0016] As an optional embodiment, the diameter of the working end face of the needleless stirring friction device is equal to the wall thickness of the component to be formed.

[0017] As an optional embodiment, the diameter of the pre-pressed blank is less than or equal to the diameter of the contact surface.

[0018] As an optional embodiment, the axial pressure P1 is 20-100KN, and the rotation speed ω1 of the needleless friction stir machining head is 800-2000rpm.

[0019] As an optional embodiment, in the in-situ extrusion rod making and rotary friction stir additive manufacturing processes, the rotation direction of the needleless friction stir device used in the deposition process is consistent with the rotation direction of the needleless friction stir device used in the rod making process.

[0020] As an optional embodiment, in the in-situ extrusion rod forming and rotary stirring friction additive manufacturing process, the axial pressure P1 is equal to the deposition pressure P2, and the rotational speed ω1 of the stirring head is equal to the rotational speed ω2.

[0021] As an optional embodiment, the metal scraps, particles, or powder are made of aluminum alloy.

[0022] The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction, as described above, proposes an integrated continuous additive manufacturing process of "rotational friction in-situ extrusion into rods" and "synchronous rotational friction stirring additive deposition." A pre-pressed blank is formed by pre-pressing metal scraps, particles, etc. An axial downward pressure is applied by an extrusion container, synchronously driving a needleless friction stirring device to rotate. Through the rotational friction of the needleless friction stirring device (upper friction part) and the axial downward pressure applied by the extrusion container, the pre-pressed blank undergoes plasticization under the action of axial pressure and rotation (rotational friction heat generation). The thermoplastic fluid flows to the central mold of the needleless friction stirring device under axial pressure and is extruded into a rod, obtaining a thermoplasticized extruded metal rod. The axial pressure continues to extend to the shoulder at the bottom of the needleless friction stirring device, where plastic deformation occurs under the synchronous rotational friction stirring action of the needleless friction stirring device, causing deposition on a substrate. Therefore, the in-situ continuous additive manufacturing method for metal in-situ friction multi-stage thermoplasticization proposed in this invention achieves an integrated continuous processing technology of continuous thermoplasticization of granular pre-compressed preforms, extrusion rod making, and friction stir deposition additive thin-walled structures through needle-free stirring tool compound friction heating (rotation), in-situ extrusion strong plastic rod making (extrusion), and stirring friction deposition (stirring). This achieves seamless connection of continuous strong plastic deformation throughout the entire process and overcomes the problems of stability control and dimensional accuracy control of thin rod forming. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of the first exemplary in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction.

[0024] Figure 2This is a schematic diagram of the structure of the second exemplary in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction.

[0025] Figure 3 This is a schematic diagram of the structure of the second exemplary in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction, which illustrates the thermoplastic deformation of materials in friction stirring additive manufacturing.

[0026] Figure 4 This is a detailed structural comparison diagram of the second exemplary in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction according to the present invention.

[0027] Figure 5 This is a schematic diagram of the in-situ rod-continuous friction stirring additive manufacturing process based on the second exemplary in-situ rod-stirring frictional additive manufacturing equipment according to the present invention.

[0028] Figure 6 This is a schematic diagram of the rotary rod thermoplasticization principle of the in-situ rod-stirring friction continuous additive manufacturing equipment based on the second exemplary rotary friction multi-stage thermoplasticization according to the present invention.

[0029] Figure 7a , 7b 7a and 7b are schematic diagrams of the rotary extrusion in-situ rod making and friction stir additive deposition processes of the in-situ rod making-friction stir continuous additive manufacturing equipment based on the second exemplary rotary friction multi-stage thermoplasticization according to the present invention, wherein 7a represents the rotary extrusion in-situ rod making process, 7b represents the friction stir additive deposition process, and 7c represents a schematic diagram of obtaining a molded part by layer processing.

[0030] Figure 8a , 8b 8c and 8d are schematic diagrams illustrating the changes in the internal structure of materials during rotary rod-stirring friction additive manufacturing using the second exemplary in-situ rod-stirring friction additive manufacturing equipment based on rotary friction multi-stage thermoplasticization according to the present invention, respectively showing the morphology of the original structure, the extruded structure, the rotary plasticized structure, and the deposited structure.

[0031] Figure 9 This is a schematic diagram of the structure of an exemplary aluminum alloy thin-walled sleeve printing component of the present invention.

[0032] Figure 10 This is a schematic diagram of a conventional coaxial rod feeding friction stir additive manufacturing equipment used in Comparative Example 1 of this invention.

[0033] Figure 11 This is a schematic diagram of the conventional wire feeding, stirring, and additive manufacturing equipment used in Comparative Example 2 of this invention. Detailed Implementation

[0034] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0035] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, in which numerous illustrative embodiments are shown. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described below in more detail, can be implemented in any of a number of ways.

[0036] This invention combines the synergistic effects of rotary stirring, shear extrusion, and friction stir deposition to establish a steady-state mechanism for the flow and solid-phase formation of thermoplastic metals. It forms an integrated short-process manufacturing process of "plasticization-rod making-deposition" from particles to thin-walled structures, breaking through the challenge of friction stir additive manufacturing of thin-walled structures below 20mm and even below 10mm, and providing a new approach for low-stress and high-efficiency additive manufacturing of complex thin-walled components of high-strength aluminum alloys.

[0037] In-situ rod-stirring continuous additive manufacturing equipment based on rotational friction multi-stage thermoplasticization

[0038] Combination Figure 1-5 As shown, the exemplary additive manufacturing apparatus of the present invention includes an extrusion container 100 and a needleless stirring friction device 200.

[0039] The extrusion container 100 typically has a cylindrical container body structure with a through cavity 110 for holding the pre-compressed billet 300. In one optional example, the extrusion container 100 is a hydraulic cylinder.

[0040] In some embodiments, the extrusion container 100 is further provided with an extrusion rod 120 for applying axial pressure to the pre-compressed blank 300 placed in the cavity of the extrusion container. It should be understood that the aforementioned pre-compressed blank 300 specifically refers to a pre-compressed blank obtained by pre-compressing raw materials such as metal scraps and granules using equipment such as a patting machine, for example, a disc-shaped blank.

[0041] Combination Figure 2-4 As shown, the needleless friction stir apparatus 200 includes a needleless friction stir processing head 210 that can be driven to rotate at high speed to perform additive manufacturing through friction stir.

[0042] The friction stir machining head 210 includes a spindle connecting section 211 and a shoulder 221.

[0043] The shoulder 221 facing the substrate 1000 or the deposited layer serves as the working end face 222.

[0044] The end of the main shaft connecting section 211 away from the shoulder 221 is connected to the lower end of the extrusion container 100 via a rolling bearing 500. The end of the main shaft connecting section 211 away from the shoulder 221 is defined as the connecting end. The end face of the connecting end forms a contact surface 212 that directly engages with the lower end of the extrusion container 100. During the operation of the needleless stirring friction device 200, the aforementioned contact surface 212 directly contacts the pre-pressed blank 300.

[0045] In a specific example, the inner ring of the rolling bearing 500 is coaxially arranged with the connecting end, and the outer circumference of the connecting end is sleeved and fixed to the inner circumferential surface of the inner ring; the outer ring of the rolling bearing 500 is assembled to the inner wall of the extrusion container, and the two are coaxially arranged with the outer circumferential surface of the outer ring fitting and fixed to the inner wall of the extrusion container 100. In an optional embodiment, the lower end of the inner wall of the extrusion container 100 has an annular hole for accommodating and fixing the rolling bearing 500. Thus, a rigid connection is formed between the rolling bearing 500 and the extrusion container 100 and the friction stir processing head 210, respectively, allowing the friction stir processing head 210 to rotate freely around its axis, while constraining the extrusion container cavity and the friction stir processing head 210 to remain relatively stationary.

[0046] Combination Figure 4 As shown, in an optional example, the aforementioned contact surface 212 is provided with a friction part 213, such as a groove-shaped friction part, to increase the friction between the contact surface and the pre-pressed blank.

[0047] In one example, the aforementioned friction part 213 is a spiral groove.

[0048] Referring to the diagram, the needleless friction stir processing head 210 has a through hole 215 extending vertically. The through hole 215 is preferably located at the center of the friction stir processing head 210, serving as the central mold for extrusion rod forming. Thus, the pre-compressed blank 300 within the cavity 110 is extruded by the hydraulic rod 120, while the needleless friction stir processing head 210 enters the rotational friction stage, applying rotational friction to the pre-compressed blank 300. Combined with the axial pressure applied by the hydraulic rod 120 (e.g., P1 = 20-100 kN), the pre-compressed blank 300 is plasticized under the combined action of rotation and axial pressure. Under the axial pressure, thermoplastic fluid flows into the through hole 215, forming an extruded rod, thus achieving in-situ extrusion rod forming.

[0049] In an optional embodiment, the through hole 215 is preferably circular or square, and the size (side length or diameter) of the through hole 215 is preferably 1.6 mm to 5 mm, typically equivalent to the wall thickness of the 3D solid component to be processed. In this example, a square hole is used as an example for illustration.

[0050] In an optional example, multiple protrusions, such as teardrop-shaped protrusions 223, are provided on the working end face 222 of the shoulder 221 along the periphery of the aforementioned through hole 215. These protrusions are used to improve the frictional heat generation of the material, the mixing of the deposited material and the substrate during plastic deformation, and to improve the interfacial bonding strength. As a preferred embodiment, the multiple protrusions are evenly distributed around the edge of the through hole 215. For example, for the square hole in the illustrated example, a protrusion is provided on the outer side of each side.

[0051] In an optional example, the outer wall of the spindle connection section 211 is provided with a heat insulation device to ensure the temperature inside the through hole 215; in one specific example, the heat insulation device is a heat insulation sleeve fitted on the outer wall of the spindle connection section 211.

[0052] Combination Figure 2 , Figure 4 , Figure 5 In the example shown, a sleeve 250 can be provided on the outer wall of the shoulder for providing a rigid constraint ball structure 251 that can move up and down on the outer periphery of the shoulder. The rigid constraint ball structure 251 on each side can move up and down independently to prevent splashing during the deposition process and ensure the molding size.

[0053] In an optional example, the needleless friction stir apparatus 200 is further provided with a clamping mechanism (not shown) that clamps the spindle connecting section 211. At the same time, the end of the clamping mechanism away from the spindle connecting section is configured to receive the input of rotational driving force, for example, to form a drive connection with a motor drive mechanism, or to be connected to the end of the clamping mechanism away from the connecting section through the rotation axis of a machine tool, machining center or robot, thereby realizing the drive connection between the two, thereby driving the friction stir processing head 210 to rotate at high speed, performing in-situ extrusion-friction stir rod making and rotational friction stir additive processing using the extruded rod.

[0054] In an optional embodiment, the needleless stirring friction device 200 is particularly configured to be driven at high speed by a bypass shaft drive.

[0055] It is understood that the extrusion container 100 and the needleless friction stir machining head 210 are detachably connected, and can be adapted to connect needleless friction stir machining heads with different working end face sizes as needed, to meet the processing requirements of different sizes and 3D solid component parts.

[0056] In-situ continuous additive manufacturing method for metal based on multi-stage thermoplasticization of rotational friction

[0057] Combination Figure 2 , Figure 4 , Figure 5 as well as Figures 7a-7c As shown, the in-situ continuous additive manufacturing method for metal based on multi-stage thermoplasticization of rotational friction, using the aforementioned additive manufacturing equipment, includes the following steps:

[0058] Metal powder and / or metal scrap particles are pre-pressed into columnar pre-pressed blanks 300 using equipment such as a blister press;

[0059] Based on the wall thickness of the 3D solid component to be processed, select a suitable needleless friction stir machining head 210, and connect the needleless friction stir machining head 210 to the extrusion container 100 through a rolling bearing.

[0060] The pre-pressed billet 300 is placed in the cavity 110 of the extrusion container 10, and the first end face of the pre-pressed billet 300 is brought into contact with the contact surface 212 of the needleless friction stir head. An axial pressure F is applied to the opposite second end face of the pre-pressed billet by the extrusion rod 120, and the needleless friction stir head 210 is driven to rotate. Under the action of rotation and axial pressure, the pre-pressed billet 300 undergoes plastic deformation through rotational friction to form a thermoplastic fluid. Under the action of axial pressure, the thermoplastic fluid enters the through hole 215 of the needleless friction stir head 210 to form a thermoplastic extruded metal bar, thus completing the in-situ extrusion bar forming.

[0061] The thermoplastic extruded metal bar extends downward along the through hole 215 under axial pressure and continues to be plasticized until it flows out from the through hole. At the same time, the needleless friction stir processing head 210 moves and stirs and processes according to a preset program, depositing layer by layer on the substrate until the component is formed, thus realizing synchronous friction stir additive manufacturing.

[0062] In an optional example, the axial pressure and the rotation speed of the needleless friction stir head 210 are set according to the temperature at which the pre-compressed blank undergoes thermoplasticization.

[0063] In one preferred example, the axial pressure P1 is 20 to 100 kN, and the rotational speed ω1 of the needleless friction stir head 210 is 800 to 2000 rpm.

[0064] In an optional embodiment, the size of the pre-pressed blank 300 is less than or equal to the size of the contact surface. In an example where both have circular cross-sectional shapes, the diameter of the disc-shaped pre-pressed blank 300 is less than or equal to the diameter of the contact surface 212. It is particularly preferred that the dimensions of both are designed to be matched and identical.

[0065] In an optional example, during the needleless friction stir in-situ rod making-additive manufacturing process, the rotation direction of the needleless friction stir head 210 used in the deposition process is the same as the rotation direction of the needleless friction stir head 210 used in the rod making process.

[0066] In an optional example, the processing parameters of the friction stir additive deposition process are determined based on the parameters of the 3D solid component to be processed, such as the rotational speed of the friction stir head, the feed rate, the deposition pressure, and the layer thickness of each pass.

[0067] In one preferred example, the process parameters for needleless friction stir additive manufacturing include: a rotational speed ω2 of 20 for the needleless friction stir head 20 of 800–2000 rpm, a feed rate V of 20–200 mm / min, a deposition pressure P2 of 20–100 KN, and a layer thickness of 1–5 mm.

[0068] Understandably, the rotational speed ω1 of the needle-free friction stir machining head 20 is equal to its rotational speed ω2, and both are set to the same speed value. The axial pressure P1 and the deposition pressure P2 are equal, and in fact, they are the same downward pressure value; ω1 and P1 in the early stage are plasticizing forces, and in the later stage they are converted into deposition forces, namely ω2 and P2.

[0069] In an optional example, the rotary friction in-situ extrusion rod-rotary stirring friction additive manufacturing apparatus and process proposed in this invention are applicable to metal materials that can be thermoplasticized and deformed, including aluminum alloys, such as 2-series (2014, 2024, 2219, etc.), 6-series (6061, 6063, etc.), and 7-series (7075, etc.) aluminum alloys.

[0070] Taking aluminum alloy as an example, the process of in-situ extrusion rod making-rotational friction stir additive manufacturing using the aforementioned additive manufacturing equipment includes two stages: pretreatment and integrated rotary-extrusion-friction stir additive manufacturing.

[0071] (1) Preprocessing

[0072] Raw material preparation: Polish the substrate and remove surface oil with alcohol to avoid affecting the additive manufacturing process;

[0073] Clamping: Fixing the substrate to the fixture baffle to ensure the accuracy of manufacturing complex shapes and dimensions;

[0074] Tool setting: First, start the machining system and adjust the additive manufacturing head to the required position;

[0075] The pressing stage involves pre-pressing metal powder, scrap, or a mixture of both into a cake-shaped blank (such as a cake-shaped block of a certain thickness and diameter) using a pressing machine, and then pressing it into the cavity of a hydraulic cylinder by a hydraulic rod.

[0076] (II) Integrated Rotation-Extrusion-Stirring Friction Additive Manufacturing

[0077] Combination Figure 4 , Figure 5 as well as Figure 7a, 7b As shown in 7c, it includes a rotary friction stage, an in-situ extrusion rod-making stage, and a synchronous stirring additive stage.

[0078] Rotational friction stage: The prepared cake blank is pressed into the hydraulic cylinder by the hydraulic rod, and enters the rotational friction stage. The rotational speed (ω1=200-2000rpm) and axial pressure (P1=20-100KN) of the stirring friction processing head 20 are set. Through the rotational friction of the stirring friction processing head 20 and the axial pressure of the hydraulic rod, the pre-pressed blank 300 undergoes plastic deformation through rotational friction under the action of rotation and axial pressure, forming a thermoplastic fluid.

[0079] In-situ extrusion rod forming stage: Under the action of axial pressure, thermoplastic fluid enters the through hole 215 of the needleless friction stir head 210 to extrude rods, forming thermoplastic extruded metal rods, completing the in-situ extrusion rod forming stage, and then enters the stirring additive manufacturing stage.

[0080] Synchronous stirring additive manufacturing stage: The thermoplastic extruded metal rod enters the bottom of the needleless friction stir head 210 under pressure and is deposited by rapid rotation. The process parameters of the friction stir deposition tool are set as follows: stirring head rotation speed (ω2=200-2000rpm), forward speed (V=20-200mm / min), and downward pressure (P2=20-100kN).

[0081] This invention has low requirements for the size of the raw materials; they can be powder or even powder waste. These materials can be pressed into blanks for use, achieving recycling and reuse, reducing raw material costs, and having a higher material utilization rate compared to other methods.

[0082] In other exemplary embodiments of the present invention, the in-situ extrusion rod-rotary stirring friction additive manufacturing apparatus and process proposed in this invention can be used in particular to prepare aluminum alloy thin-walled complex structural parts, such as rocket engine tail nozzles, cabin structures of aerospace components, frame beam structures, etc.

[0083] To facilitate better understanding, the present invention will be further described below with reference to specific examples, but the preparation process is not limited to this, and the content of the present invention is not limited to this.

[0084] Unless otherwise specified, the materials in the examples are prepared according to existing methods or purchased directly from the market.

[0085] The 3D solid component prepared in the following example is a sleeve with a wall thickness of 5mm, a cross-sectional diameter of 100mm, and a height of 40mm. Figure 9 As shown.

[0086] The rotary-extrusion-friction stirring integrated additive manufacturing equipment proposed in the embodiments of the present invention used in Examples 1-2 has a contact surface that is a disc with a diameter of 50 mm, a through hole in the friction stirring processing head that is a square hole with a size of 1.6 × 1.6 mm, and a shoulder diameter of 5 mm.

[0087] Example 1

[0088] (1) Polish the 2 series aluminum alloy substrate of the Al-Cu system (taking the aluminum alloy substrate with grade 2319 as an example), remove the surface oil stains with alcohol, and then fix the 2319 aluminum alloy substrate on the clamp baffle.

[0089] (2) Turn on the motor, adjust the working end face of the stirring head to a position 2mm away from the substrate, and press the Al-Mg-Si system 6 series aluminum alloy scrap material (taking 6061 metal scrap as an example) into a cake-shaped blank with a diameter of 50mm and a thickness of 20mm through the pressing machine.

[0090] (3) Set the process parameters: the axial pressure of the hydraulic rod is 40KN, the rotation speed of the needleless stirring friction processing head is 320rpm, the travel speed is 100mm / min, and the layer height is 2mm.

[0091] (4) Single-pass deposition is performed. Under the action of axial pressure, the prepared cake-shaped blank is pressed into the hydraulic cylinder. Under the combined action of the rotational friction of the needleless stirring friction head with a spiral groove end face, the cake-shaped blank is broken and plasticized. The thermoplastic fluid flows to the central through hole of the needleless stirring friction head under axial pressure and is extruded into an extruded square bar with a size of 1.6×1.6mm. The prepared extruded square bar undergoes plastic deformation under the action of rotational friction stirring of the needleless stirring friction head, causing it to be deposited on the substrate.

[0092] (5) Perform multi-pass deposition. For each layer deposited, the needleless stirring friction processing head rises 2mm. Print 20 layers. The printing path is reciprocating. Finally, a uniform aluminum alloy component is prepared.

[0093] Example 2

[0094] (1) Polish the 2 series aluminum alloy substrate of the Al-Cu system (taking the aluminum alloy substrate with grade 2319 as an example), remove the surface oil stains with alcohol, and then fix the 2319 aluminum alloy substrate on the clamp baffle.

[0095] (2) Turn on the motor, adjust the working end face of the stirring head to a position 2mm away from the substrate, and press the 2 series aluminum alloy scrap material of the Al-Cu system (taking 2319 metal scrap as an example) into a cake-shaped blank with a diameter of 50mm and a thickness of 20mm through the pressing machine.

[0096] (3) Set the process parameters: the axial pressure of the hydraulic rod is 45KN, the rotation speed of the needleless stirring tool is 350rpm, the travel speed of the stirring tool is 100mm / min, and the layer height is 2mm.

[0097] (4) Single-pass deposition is performed. Under the action of axial pressure, the prepared cake-shaped blank is pressed into the hydraulic cylinder. Under the combined action of the rotational friction of the needleless stirring friction head with a spiral groove end face, the cake-shaped blank is broken and plasticized. The thermoplastic fluid flows to the central through hole of the needleless stirring friction head under axial pressure and is extruded into an extruded square bar with a size of 1.6×1.6mm. The prepared extruded square bar undergoes plastic deformation under the action of rotational friction stirring of the needleless stirring friction head, causing it to be deposited on the substrate.

[0098] (5) Perform multi-pass deposition. For each layer deposited, the needleless stirring friction processing head rises 2mm. Print 20 layers. The printing path is reciprocating. Finally, a uniform aluminum alloy component is prepared.

[0099] Comparative Example 1

[0100] like Figure 10 As shown, a 5mm thin-walled component was manufactured using a conventional coaxial rod feeding friction stir additive manufacturing equipment. The diameter of the rod was 15mm and the shoulder was 30mm.

[0101] (1) Polish the 2 series aluminum alloy substrate of the Al-Cu system (taking the aluminum alloy substrate with grade 2319 as an example), remove the surface oil stains with alcohol, and then fix the 2319 aluminum alloy substrate on the clamp baffle.

[0102] (2) Grind the 15mm×15mm×400mm square 6061 bar with a file, load it into the coaxial rod feeding friction stir additive manufacturing equipment, turn on the motor, and adjust the stirring tool to a position 2mm away from the substrate.

[0103] (3) Set the process parameters as follows: the stirring tool rotation speed is 350 rpm, the downward pressure is 35 KN, the rod feeding speed is 6 mm / s, the forward speed is 100 mm / s, and the layer height is 2 mm. The stirring tool rises 2 mm for each layer printed, and 20 layers are printed. The printing path is reciprocating. Finally, a uniform aluminum alloy component is produced. The wall thickness of the produced aluminum alloy component is 30 mm, which cannot form a 5 mm thin-walled part in one step.

[0104] Comparative Example 2

[0105] like Figure 11 As shown, 6061 aluminum alloy wire with a diameter of 2.4 mm is used, the diameter of the movable shoulder at the probe root is 14 mm, the diameter of the shaft shoulder is 24 mm, and the length of the three stirring probes is 2 mm.

[0106] (1) Polish the 2-series aluminum alloy substrate of the Al-Cu system (taking the aluminum alloy substrate with grade 2319 as an example), remove the surface oil stains with alcohol, and then fix the 2319 aluminum alloy substrate on the clamp baffle.

[0107] (2) A commercially available 6061 aluminum alloy wire with a diameter of 2.4 mm is loaded into a wire-feeding friction stir additive manufacturing device, such as... Figure 11 Turn on the motor and insert the probe 0.8mm into the substrate;

[0108] (3) Set the process parameters: the rotation speed of the stirring tool is 1000 mm / min, the wire feeding speed is 600 mm / min, the stirring tool rises to 0.8 mm away from the previous layer for each layer printed, the layer height is 2 mm, print 20 layers, the printing path is reciprocating, and finally a uniform aluminum alloy component is prepared. The wall thickness of the prepared aluminum alloy component is 24 mm, which cannot form a 5 mm thin-walled part in one step.

[0109] Mechanical property testing

[0110] Tensile tests, hardness tests, and microstructure observations were performed on Examples 1 and 2, Comparative Examples 1 and 2, and the results are shown in the table below.

[0111]

[0112] Based on the comparison of the above test results, it is evident that using traditional coaxial bar and wire feeding methods to prepare 6061 aluminum alloy components via friction stirring in Examples 1 and 2 makes it difficult to produce the required thin-walled aluminum alloy components. Further hardness and tensile tests on the samples revealed that the components prepared by the traditional method exhibited lower hardness, tensile strength, and yield strength compared to those prepared using the method of this invention. This is because the 3D solid components prepared using the method of this invention, combined with… Figure 4 , Figure 6 as well as Figures 8a-8d As shown, through multi-stage thermoplastic deformation, its grains change from the original columnar grains (such as...) Figure 8a During the blanking and forming stage, the microstructure becomes smaller (e.g., ...). Figure 8b Then, through rotational plasticization using a needle-free stirring tool, the grains are further refined (e.g., Figure 8c Finally, through rotational deposition using a stirring tool, fine and uniform ultrafine equiaxed crystals (such as...) are obtained. Figure 8d Therefore, the manufactured 3D solid components have superior mechanical properties, and higher toughness and strength.

[0113] While traditional methods of coaxial rod and wire feeding for 3D solid components prepared by friction stir additive manufacturing avoid defects such as porosity and hot cracking by eliminating melting throughout the process, and transforming grains into fine equiaxed grains due to intense plastic deformation and dynamic recrystallization, thus improving the mechanical properties of the components, they cannot achieve the level of refinement required by the method of this invention. The toughness and strength of the obtained components are inferior to those of the process of this invention. These methods are only suitable for preparing large-sized structures and cannot prepare thin-walled parts. However, the in-situ extrusion rod-rotary friction stir additive manufacturing device and process proposed in this invention can realize the friction stir additive processing of thin-walled parts below 10mm, achieving the integrated preparation of high-toughness and high-strength metal 3D solid components.

[0114] Meanwhile, the method of this invention can significantly improve material utilization and reduce costs. For example, taking aluminum alloy component printing as an example, this invention can use metal scraps, metal particles, or a combination thereof as raw materials, and achieve integrated preparation through multi-stage thermoplastic in-situ extrusion rod forming and rotary friction stir additive manufacturing. In contrast, traditional coaxial rod and wire feeding methods for friction stir additive manufacturing use finished wire and rod materials, such as the 6061 square rod and 6061 wire mentioned in the previous embodiment. According to commercially available standards, 6061 square rod costs 35 yuan / kg, 6061 wire costs 50 yuan / kg, while 6061 aluminum alloy scrap only costs about 10 yuan / kg, resulting in lower component preparation costs. Furthermore, due to the scrap pressing pre-preform treatment, the material utilization rate is high, reaching up to 90%.

[0115] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. An in-situ rod-forming / friction stirring continuous additive manufacturing apparatus based on multi-stage thermoplasticization of rotary friction, characterized in that, It includes an extrusion container (100) and a needleless friction stir device (200); the needleless friction stir device (200) includes a needleless friction stir head (210) that can be driven to rotate at high speed to perform additive processing by friction stir. The extrusion container (100) has a through cavity (110) for placing a pre-pressed blank (300); the pre-pressed blank (300) refers to a blank block with a certain shape and thickness obtained by pre-pressing metal scraps, particles, and powder; the extrusion container (100) is also provided with an extrusion rod (120) for applying axial pressure to the pre-pressed blank (300) placed in the cavity of the extrusion container to cause it to plasticize and generate a thermoplastic fluid; The needle-free friction stir processing head (210) has a spindle connecting section (211) and a shoulder (221); the side of the shoulder (221) facing the substrate or the deposited layer serves as the working end face (222); the end of the spindle connecting section (211) away from the shoulder (221) is connected to the lower end of the extrusion container (100) through a rolling bearing (500), and the outer ring and inner ring of the rolling bearing are rigidly connected to the extrusion container and the friction stir processing head, respectively, so that the friction stir processing head (210) can rotate freely around the axis and constrain the extrusion container (100) and the friction stir processing head (210) to remain relatively stationary; The end of the main shaft connecting section (211) away from the shoulder (221) is defined as the connecting end. The end face of the connecting end forms a contact surface (212) that is directly engaged with the lower end of the extrusion container (100). During the rotation of the needleless stirring friction device (200), the contact surface (212) directly contacts and rubs against the pre-pressed blank (300) placed inside the extrusion container (100). The needle-free friction stir processing head (210) is provided with a through hole (215) that runs vertically through the head. The through hole (215) is located at the axial center of the friction stir processing head (210) and is used to form the central mold for extruding rods. In this process, the pre-pressed blank (300) in the cavity (110) is extruded by the extrusion rod (120). The needle-free friction stirring head (210) is driven to rotate and apply rotational friction to the pre-pressed blank (300). Combined with the axial pressure P1 applied by the extrusion rod (120), the pre-pressed blank (300) is rotated and plasticized under the action of rotation and axial pressure. Under the action of axial pressure, the thermoplastic fluid flows into the through hole (215) to form an extruded bar, realizing in-situ extrusion bar making and obtaining thermoplasticized extruded metal bar. The extruded metal rod extends to the shoulder (221) of the needleless friction stir processing head (210) under axial pressure, and performs continuous friction stir additive processing through the working end face (222) of the shoulder (221) when the friction stir processing head (210) is driven to rotate, so that the extruded metal rod is deposited layer by layer on the substrate until the component is formed, realizing synchronous friction stir additive manufacturing.

2. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction according to claim 1, characterized in that, The inner ring of the rolling bearing (500) is coaxially arranged with the connecting end, and the outer circumference of the connecting end is sleeved and fixed to the inner circumferential surface of the inner ring; the outer ring of the rolling bearing (500) is assembled on the inner wall of the extrusion container, the two are coaxially arranged and the outer circumferential surface of the outer ring is attached and fixed to the inner wall of the extrusion container (100).

3. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction as described in claim 1, characterized in that, The contact surface (212) is provided with a friction part (213) to increase the friction between the contact surface and the pre-pressed blank.

4. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction according to claim 1, characterized in that, The friction part (213) includes a spiral groove.

5. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction as described in claim 1, characterized in that, The diameter of the working end face of the needleless stirring friction device is equal to the wall thickness of the component to be formed.

6. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction according to claim 1, characterized in that, The diameter of the pre-pressed blank (300) is less than or equal to the diameter of the contact surface (212).

7. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction as described in claim 1, characterized in that, The axial pressure P1 is 20-100KN, and the rotation speed ω1 of the needleless friction stir head (210) is 800-2000rpm.

8. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotational friction as described in claim 1, characterized in that, In the in-situ extrusion rod making and rotary friction stirring additive manufacturing processes, the rotation direction of the needleless friction stirring device used in the deposition process is the same as the rotation direction of the needleless friction stirring device used in the rod making process.

9. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction according to claim 1, characterized in that, In the in-situ extrusion rod making and rotary stirring friction additive manufacturing process, the axial pressure P1 is equal to the deposition pressure P2, and the rotational speed ω1 of the stirring head is equal to the rotational speed ω2.

10. The in-situ rod-stirring friction continuous additive manufacturing equipment based on multi-stage thermoplasticization of rotary friction according to claim 1, characterized in that, The metal scraps, particles, and powders are aluminum alloy materials.

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