Method and device for solid phase regeneration of metal scrap into ultrafine grain material by inertial friction drive

Abstract

The present application belongs to the technical field of metal recycling and solid-phase additive manufacturing, and particularly relates to a method and device for inertial friction driven solid-phase recycling of metal waste to form superfine-grained material, in which, after forming a raw material layer on a forming base plate, low-frequency vibration is first applied to the forming base plate, and then, with the assistance of a pulse magnetic field, a friction tool head of an inertial friction device is used to perform rotary friction shearing and axial extrusion on the raw material layer, so that the raw material is plastically deformed and solid-phase formed, and is stacked layer by layer to a target thickness to obtain recycled superfine-grained material; the present application takes metal powder, particles, scraps and other multi-form metal waste as raw material, and is based on solid-phase metallurgical combination, and through pulse magnetic field assisted solid-phase recycling organization regulation and control, forced cooling heat control and interlayer stable feeding, realizes short-process, high-efficiency and high-value-added recycling manufacturing of metal waste.

Description

Technical Field

[0001] This invention relates to the field of metal recycling and solid-phase additive manufacturing technology, and in particular to a method and apparatus for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction. Background Technology

[0002] Traditional metallurgical processes such as casting, forging, rolling, and machining generate large amounts of cutting debris, grinding particles, and offcuts, encompassing various metal materials including aluminum alloys, steel, and copper alloys. These metal scraps typically retain high metal purity and recyclability, making them important secondary resources for achieving resource recycling and reducing the consumption of primary mineral resources. With the continuous growth in demand for high-performance metal materials, how to directly regenerate low-value-added metal scrap into high-performance structural materials has become a core research direction in the field of metal recycling.

[0003] Currently, the recycling of metal waste mainly employs methods such as remelting and recasting, traditional powder metallurgy sintering, and fused deposition modeling (FDM). Both remelting and FDM rely on solid-liquid-solid phase transformation processes, which generally suffer from high energy consumption, element loss, compositional segregation, coarse microstructure, hot cracking, and porosity, making it difficult to balance material performance and economic efficiency. While traditional powder metallurgy is a solid-state forming method, it typically requires a long sintering cycle, resulting in limited interparticle bonding efficiency and defects such as residual porosity, localized incomplete densification, and insufficient metallurgical bonding, hindering the achievement of short-process, high-performance recycling of metal waste.

[0004] Ultrafine-grained metallic materials (average grain size 0.1 μm ~ 1 μm) have become the ideal target microstructure for the high-value solid-phase recycling of waste materials due to their excellent comprehensive mechanical properties such as high strength and good ductility and toughness. However, existing continuous friction-driven or continuous stirring friction technologies continuously input energy during the forming process, which easily leads to significant heat accumulation in the forming zone. This continuous heat accumulation will cause abnormal grain growth after dynamic recrystallization, destroying the fine-grain strengthening effect and making it difficult to stably obtain high-performance ultrafine-grained microstructures. In addition, existing solid-phase processes are usually designed for regular-shaped raw materials such as continuous wires, rods, or plates, and are severely unsuitable for loose waste materials with multiple forms, such as powders, particles, and debris. On the one hand, when multi-form waste materials are laid up, coarse and fine particles and irregular debris are mixed and piled up, which easily forms large pores and uneven layup, resulting in fluctuations in subsequent solid-phase forming loads and unstable density of recycled components. On the other hand, there are a large number of oxide films and interface defects at the interface of loose debris particles, resulting in low metallurgical bonding efficiency between particles, making it difficult for the recycled material to meet the requirements of high-performance ultrafine-grained materials.

[0005] Therefore, it is necessary to develop a solid-phase regeneration method and device for multi-form metal scrap, which can not only avoid melting metallurgical defects, but also solve the core problems of uneven loose debris layering and low metallurgical bonding efficiency at the particle interface, while suppressing grain coarsening caused by continuous frictional heat accumulation, so as to realize high-value solid-phase regeneration of metal scrap into high-performance ultrafine-grained materials. Summary of the Invention

[0006] Based on the above considerations, this invention provides a method and apparatus for solid-phase regeneration of ultrafine-grained materials from metal scrap driven by inertial friction. Using multi-morphological metal scrap as raw material, solid-phase metallurgical bonding as the foundation, flywheel inertial pulsed energy release as the main forming method, vibration-assisted layer homogenization as a material laying guarantee measure, and pulsed magnetic field-assisted solid-phase regeneration microstructure control as a synergistic means, combined with forced cooling, interlayer temperature control, and an anti-adhesion tool retraction mechanism, this invention achieves layer-by-layer densification and solidification of the metal scrap raw material at temperatures below the liquidus line, ultimately obtaining a uniform and stable ultrafine-grained regenerated material. This invention solves the current problems of: ① uneven multi-morphological metal scrap layering, numerous large pores, and low forming rate; ② difficulty in fully breaking down the oxide film at the interface of loose scrap particles, low interface metallurgical bonding efficiency, and numerous internal defects in the regenerated material; ③ abnormal growth of dynamically recrystallized grains due to heat accumulation during solid-phase forming, making it difficult to stably prepare ultrafine-grained high-performance materials. This invention achieves short-process, high-efficiency, and high-value-added regeneration manufacturing of metal scrap, and is particularly suitable for the preparation of ultrafine-grained metal materials.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a solid-phase regeneration method for ultrafine-grained metal waste materials driven by inertial friction, comprising the following steps: S1. After the pre-treated raw material to be recycled is laid in layers on the forming substrate to form a raw material layer, low-frequency vibration is applied to the forming substrate to cause the raw material layer particles to rearrange and fill. S2. Under the assistance of a pulsed magnetic field, the friction tool head of the inertial friction device is used to perform rotational friction shearing and axial extrusion on the raw material layer, causing the raw material to undergo plastic deformation and solid-phase forming. S3. After forming, turn off the pulse magnetic field and retract the tool to control the temperature of the friction tool head and the forming area; S4. Repeat steps S1 to S3, and deposit layer by layer to the target thickness to obtain a regenerated ultrafine crystalline material, wherein the average grain size in the regenerated ultrafine crystalline material is 0.1 μm to 1 μm.

[0008] Preferably, in step S1, the raw material includes one or more of metal powder, metal particles, and metal scrap; the metal powder has a particle size of 45~150 μm, the metal particles have a particle size of 150~1000 μm, and the metal scrap has a size of 1~5 mm.

[0009] Preferably, in step S1, low-frequency vibration is applied by a vibration leveling device, with a vibration frequency of 20~200 Hz, an amplitude of 0.1~3.0 mm, a vibration direction of vertical, and a vibration time of 5~60 s.

[0010] Preferably, in step S2, the parameters of the inertial friction device are: spindle speed 500~3500 r / min, system moment of inertia 0.5~3.0 kg·m², axial load 5~30 kN, single-layer solid phase forming thickness 0.5~3.0 mm, single-layer raw material layer action time 5~40 s, and controlled energy input density 0.5~2.0 J / mm². 2 .

[0011] Preferably, in step S2, the direction of the pulsed magnetic field is along the horizontal direction of the raw material layer, the magnetic field strength is 0.5~5.0T, the pulse frequency is 1~50 Hz, and the pulse width is 1~50 ms.

[0012] Preferably, in step S2, during the solid-state forming process, the forming substrate is cooled, and the temperature of the cooling medium is 0-5°C; the peak temperature of the forming zone is controlled below the liquidus line of the material.

[0013] Preferably, in step S3, during the tool retraction process, the axial load of the inertial friction device is reduced to 0-30% of the forming load, and it exits at a low speed of 50-500 r / min or in the reverse rotation state.

[0014] Preferably, in step S3, during the tool retraction process, the end face of the friction tool head and the forming area are simultaneously cooled by short-term jetting to control the temperature of the end face of the friction tool head to 200-350°C and the surface temperature of the forming area to ≤250°C.

[0015] Preferably, in step S4, during the layer-by-layer stacking process, the forming substrate and the friction tool head are controlled to feed relative to each other in the vertical direction, and the interlayer feed amount is 0.5~3.0 mm.

[0016] The second aspect of the present invention provides an inertial friction driven solid-phase regeneration device for ultrafine crystalline materials of metal waste. The device includes a forming chamber, a liftable platform installed at the bottom of the forming chamber, a forming substrate fixed on the liftable platform, a vibration leveling device connected to the forming substrate, an inertial friction device, a pulse magnetic field coil, a forced cooling device, a graded feeding device, and a control system. The inertial friction device is installed above the forming chamber and includes a flywheel assembly, a spindle assembly and a friction tool head connected in sequence. The friction tool head extends into the forming chamber and is located above the forming substrate. The pulsed magnetic field coils are mounted on both sides of the forming cavity via brackets; The forced cooling device includes a cooling channel disposed below the forming substrate and / or a gas nozzle facing the forming area, for cooling and temperature control of the forming area, the friction tool head and the forming substrate; The graded feeding device includes 2 to 5 sets of feeding units. Each set of feeding units is independently equipped with a hopper and a feeding pipe connected to the hopper. The outlets of each feeding pipe are arranged side by side along the material spreading direction. The control system is electrically connected to the inertial friction device, the graded feeding device, the vibration leveling device, the pulse magnetic field auxiliary device, the forced cooling device, and the feed clamping device, respectively.

[0017] Compared with the prior art, the present invention has the following beneficial technical effects: (1) This invention directly uses waste metal powder, granules and scrap as raw materials, highlighting the characteristics of short-process high-value recycling manufacturing of waste metal, without having to reprocess the waste into blanks or wires, thus greatly shortening the recycling manufacturing process.

[0018] (2) The present invention adopts a solid-state metallurgical route, with the peak temperature throughout the process being lower than the liquidus temperature of the raw material metal, thus avoiding defects such as segregation, hot cracks, porosity, element burn-off and coarse solidification structure caused by traditional melting metallurgy.

[0019] (3) The independent vibration leveling device set up in this invention drives the rearrangement and filling of particles and debris of different sizes through controlled low-frequency vibration excitation, effectively eliminating large pores in multi-form waste layering, improving layer uniformity and initial packing density, and solving the problems of uneven laying and low forming rate of loose metal debris in the prior art. This vibration leveling method does not depend on the magnetism of the raw material and is equally applicable to ferromagnetic, paramagnetic and non-magnetic conductive metal waste, completely avoiding the fundamental defect of insufficient applicability of magnetic field leveling method to non-ferromagnetic metals (such as aluminum alloys).

[0020] (4) This invention uses flywheel inertial energy storage and one-time energy release to achieve pulsed friction forming. Compared with continuous friction drive process, it can reduce the effect of continuous heat source from the energy input method. The forming heat input has a clear upper limit (maximum releaseable energy E=1 / 2Jω). 2 This significantly suppresses heat accumulation in the forming zone, which is more conducive to the stable preparation of ultrafine-grained regenerated materials; this is a fundamental advantage that existing continuous friction-driven processes cannot achieve.

[0021] (5) The present invention introduces pulsed magnetic field-assisted technology into the solid-state regeneration and consolidation process of converting loose metal debris (discontinuous body) into dense continuous metal block. The essential difference between this invention and the existing magnetic field-assisted metal processing technology (which are all for continuous sheet / workpiece) is that the pulsed magnetic field of the present invention acts on the loose metal debris particles in the solid-state regeneration and consolidation process through the magnetoplastic effect, and the effects are as follows: ① promote the breaking of oxide film and atomic diffusion at the particle interface, and eliminate interface metallurgical bonding defects; ② promote dynamic recrystallization and uniform nucleation, and ensure the uniformity of the structure; ③ inhibit abnormal grain growth, stably obtain uniform ultrafine grain structure, and achieve high performance matching of high strength and high plasticity of regenerated materials.

[0022] (6) The present invention uses the coordinated linkage of liquid cooling channel, gas nozzle and tool head temperature control unit to precisely manage the heat input of single layer forming and interlayer heat circulation through temperature window mechanism, which can effectively suppress grain coarsening after dynamic recrystallization and ensure the uniformity of structure and the layer-by-layer repeatability of ultrafine grain structure.

[0023] (7) After the single-layer forming is completed, the present invention adopts unloaded tool retraction, low-speed rotation tool retraction or reverse rotation tool retraction, and cooperates with anti-adhesion auxiliary mechanism, which can effectively reduce the adhesion tendency between the friction tool head and the forming layer and improve the reliability of multi-layer continuous forming.

[0024] (8) This invention differs from the existing continuous friction additive manufacturing process that relies on feeding the center of the rod. It adopts a structure with a vertical spindle, a horizontal substrate, upper graded bulk feeding and vertical interlayer feeding. It makes full use of the gravity-driven natural laying characteristics of bulk particles and debris materials. It does not require intermediate forming into a compact and can directly achieve stable layer-by-layer stacking in the original form of waste, which greatly shortens the recycling process.

[0025] (9) The present invention can be compatible with the preparation of single materials, composite materials and gradient materials, thus broadening the application scope of high-value-added recycling of metal waste. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of the solid-phase regeneration manufacturing device for ultrafine-grained metal waste driven by inertial friction provided by the present invention.

[0027] Figure 2 This is a process flow diagram of the solid-phase regeneration method for ultrafine-grained metal waste materials driven by inertial friction provided by the present invention.

[0028] Figure 3 This is the macroscopic morphology of the cross-section of the sample prepared in Example 1 of the present invention.

[0029] Figure 4 This is the central electron backscattering diffraction pattern of the sample prepared in Example 1 of this invention.

[0030] Figure 5 This is the tensile curve of the sample prepared in Example 1 of the present invention.

[0031] Figure 6 The microstructure of the sample prepared in Comparative Example 1 of this invention is shown in (a) a secondary electron scanning electron microscope image and (b) an electron backscatter diffraction pattern.

[0032] Figure label: 1—Flywheel assembly; 2—Spindle assembly; 3—Friction tool head; 4—Forming chamber; 5—Hopper; 6—Feeding channel; 7—Forming substrate; 8—Cooling channel; 9—Liftable platform; 10—Vibration leveling device; 11—Pulse magnetic field coil; 12—Gas nozzle; 13—Control system; 14—Vibration transmission structure; 15—Anti-adhesion auxiliary mechanism. Detailed Implementation

[0033] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0035] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0036] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," "axis," "longitudinal," and "transverse," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. In addition, the terms "first," "second," and "third," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0037] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0038] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0039] The present invention proposes an inertial friction-driven solid-phase regeneration method for ultrafine-grained metal waste materials. First, raw materials such as metal powder, granules, and debris are laid on the surface of a forming substrate 7. Graded feeding improves the combination and stacking structure of coarse and fine particles. Then, a controlled low-frequency vibration excitation is applied through a vibration leveling device, driving the rearrangement and filling of particles and debris of different sizes, eliminating large pores in the layup. By inputting two parameters, rotational speed and inertia, into the inertial friction device, rotational kinetic energy is pre-stored by the flywheel assembly 1 and released instantaneously after engagement with the spindle assembly 2. This allows the friction tool head 3 to apply high rotational friction shearing and axial extrusion force to the raw material layer in a short time. Simultaneously, a pulsed magnetic field is applied during the forming process. Through the magnetoplastic effect, it promotes the breaking of the oxide film at the particle interface, atomic diffusion, and dynamic recrystallization, while inhibiting abnormal grain growth. Under the action of thermo-mechanical-magnetic coupling, severe plastic deformation occurs inside the raw material layer, the oxide film on the raw material surface is broken, the actual contact area between particles increases, interfacial atomic diffusion accelerates, and further dynamic recrystallization and solid-phase metallurgical bonding occur. Because this invention uses a limited release of inertial energy rather than a continuous driving method, the heat input in the forming zone has a self-suppressing characteristic; combined with forced cooling and interlayer temperature control, it can effectively suppress heat accumulation and abnormal coarsening of recrystallized grains, thereby achieving high-density, low-defect, and ultra-fine-grained solid-phase regeneration of metal waste.

[0040] like Figure 1As shown, the present invention provides an inertial friction-driven solid-phase regeneration device for ultrafine crystalline metal waste, comprising a forming chamber 4; a liftable platform 9 installed at the bottom of the forming chamber 4, the liftable platform 9 being used to support a forming substrate 7 and drive the forming substrate 7 to move up and down in the vertical direction; a vibration leveling device connected below the forming substrate 7, the vibration leveling device can adopt an existing conventional structure, the preferred structure including a vibration exciter 10, an elastic support member, and a vibration transmission structure 14, wherein the vibration exciter 10 is fixed to one end of the liftable platform 9, the vibration transmission structure 10 is connected to the bottom of the forming substrate 7 and is connected to the upper end of the liftable platform 9 through the elastic support member to isolate the influence of vibration on the feeding clamping device, and the vibration transmission structure 14 uniformly transmits the vibration generated by the vibration exciter 10 to the surface of the forming substrate to apply controlled low-frequency vibration to the raw material layer after the material is laid; a pulse magnetic field coil 11 is installed in the forming chamber 4 through a bracket, located above or to the side of the forming area; The inertial friction device is located above the forming chamber 4 and includes a flywheel assembly 1, a spindle assembly 2, and a friction tool head 3 connected in sequence. The friction tool head 3 extends into the forming chamber 4 and is axially aligned with the upper part of the forming substrate 7. In a preferred embodiment, the device may be provided with a positioning mechanism, which is connected to the spindle assembly 2 and is used to drive the spindle assembly 2 and the friction tool head 3 to position and move in the vertical direction. The forced cooling device includes a cooling channel 8 located below the forming substrate and a gas nozzle 12 facing the forming area, used to cool and control the temperature of the forming area, the friction tool head 3 and the forming substrate 7; the graded feeding device preferably includes 2 to 5 sets of feeding units, each set of feeding units is independently equipped with a hopper 5 and a feeding pipe 6 connected to the hopper, the outlets of each feeding pipe 6 are arranged side by side along the material laying direction, the outlets are aligned with the surface of the forming substrate 7, used to transport metal scrap to the forming area; the feeding speed of each feeding unit is independently adjustable.

[0041] In some embodiments of the present invention, the device further includes a friction tool head temperature detection element and an anti-adhesion auxiliary mechanism 15; the friction tool head temperature detection element is used to detect the end face temperature of the friction tool head or the forming area temperature; the anti-adhesion auxiliary mechanism 15 includes at least one of a gas blowing mechanism, a scraping mechanism, a brushing mechanism and a reverse rotation control module, used to assist the friction tool head in separating from the formed layer after the single-layer forming is completed, and to remove the adhering material on the end face of the friction tool head 3.

[0042] In some embodiments of the present invention, the friction tool head 3 is made of a material with high thermal hardness, wear resistance, and low chemical affinity, or an anti-adhesion wear-resistant coating is provided on the working end face of the friction tool head. More preferably, within the actual temperature range during the solid-state forming of the target recycled metal material (typically 50% to 80% of the liquidus temperature), the difference between the high-temperature hardness of the tool head material and the high-temperature hardness of the target recycled metal material is not less than 150 HV, to ensure that the tool head has sufficient wear resistance in the working state and to avoid wear products from mixing into the recycled material and forming contamination defects. The material of the friction tool head 3 is preferably one of silicon nitride ceramic, cemented carbide, dispersion-strengthened copper alloy, or hot work die steel, and the anti-adhesion wear-resistant coating is preferably one or more of CrAlN coating, AlTiN coating, TiAlN coating, or nitride ceramic coating.

[0043] like Figure 2 The flowchart shown illustrates a solid-phase regeneration method for ultrafine-grained metal waste materials driven by inertial friction, provided by this invention, comprising the following steps: S1. Graded feeding and spreading: The raw material to be recycled (metal waste) is degreased, impurities removed, screened and dried to make the oxygen content after pretreatment ≤0.3%, and then conveyed to the surface of the forming substrate 7 through the feeding pipe 6 of the graded feeding device to form the raw material layer to be formed. In some feasible embodiments, in step S1, the raw material includes one or more of metal powder, metal particles, and metal scrap, wherein the metal powder has a particle size of 45-150 μm, the metal particles have a particle size of 150-1000 μm, and the metal scrap has an equivalent characteristic size of 1-5 mm, wherein the metal scrap includes cutting debris, grinding debris, and other irregularly shaped waste; the present invention is more preferably to use particulate and scrap waste, and the powder-grade raw material can be used as an auxiliary component in combination with the particulate and scrap.

[0044] S2. Vibration-assisted layup homogenization: A low-frequency vibration excitation is applied to the forming substrate by a vibration leveling device. The vibration frequency applied by the vibration leveling device is preferably 20~200 Hz, for example, 20 Hz, 50 Hz, 80 Hz, 100 Hz, 150 Hz, or 200 Hz. The amplitude is preferably 0.1~3.0 mm, for example, 0.1 mm, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, or 3.0 mm. The vibration direction is vertical, horizontal, or a combination of both. The vibration duration is preferably 5~60 s after the material is laid, for example, 5 s, 10 s, 20 s, 30 s, 40 s, 50 s, or 60 s. Specifically, the vibration-assisted layup homogenization strategy involves applying controlled low-frequency vibrations to the forming substrate and / or forming chamber using vibration exciters such as electromagnetic vibrators, piezoelectric vibrators, or eccentric motors. This vibration, driven by inertial force, causes rearrangement and filling of particles and debris of different sizes within the raw material layer. This fills the gaps between coarse particles and debris with fine particles, eliminating large porosity in the layup, improving layup uniformity and initial packing density, and reducing load fluctuations during subsequent friction forming. The leveling mechanism is entirely based on particle rearrangement driven by vibration inertial force, independent of the magnetic properties of the raw material. It is equally applicable to ferromagnetic metals (steel, iron), paramagnetic metals (aluminum alloys, copper alloys, titanium alloys), and other conductive metal scraps, completely avoiding the fundamental limitation of magnetic field leveling methods in their applicability to non-ferromagnetic metals (such as aluminum alloys). Vibration parameters (frequency, amplitude, duration) are independently adjusted by the control system according to the raw material particle size distribution and layup thickness, achieving adaptive uniform layup for scraps with different material and particle size combinations.

[0045] S3. Pulsed magnetic field-assisted inertial friction-driven solid-state forming: Under the assistance of a pulsed magnetic field, the friction tool head 3 of the inertial friction device is used to perform rotational friction shearing and axial extrusion on the raw material layer, causing the raw material to undergo plastic deformation and solid-state forming. In some feasible implementations, in step S3, the inertial friction device includes a flywheel assembly 1, a spindle assembly 2, and a friction tool head 3. During the solid-state forming process of the raw material layer, the flywheel assembly 2 stores energy in advance and releases kinetic energy instantaneously during forming, driving the spindle assembly 2 and the friction tool head 3 to complete the frictional compaction and dense connection of a single layer of raw material. The energy stored in the flywheel can be expressed as E = 1 / 2 Jω², which determines the maximum energy that can be released during single-layer solid-state forming, with an energy input density E per unit forming area. A As a parameter for controlling the energy released by the flywheel, it controls the energy input density E. A The range is 0.5~6.0 J / mm. 2 Input density E A for: ; Where J is the system's moment of inertia, ω is the initial angular velocity of the principal axis, and A tool Let E be the area of ​​the friction tool head end face, and η be the energy conversion efficiency; η is taken as 0.3~0.6; however, the energy input density of the flywheel varies for different materials. Aluminum alloy has high thermal conductivity and low deformation resistance, and the target energy input density E is... A The range is 0.5–2.0 J / mm. 2 (J=0.8~1.2 kg·m) 2 (ω corresponds to 1200–1800 r / min); steel requires a higher energy input density of 2.0–6.0 J / mm². 2 (J=1.8~2.5 kg·m) 2ω corresponds to 2200~2800 r / min). Specifically, in the process of solid-state forming driven by inertial friction, if the spindle speed is too low or the moment of inertia is too small, insufficient frictional heat and shear deformation can easily lead to insufficient densification of the raw material layer and inadequate solid-state bonding. If the spindle speed is too high or the moment of inertia is too large, the temperature rise in the forming zone will be too rapid, which can easily cause heat accumulation, grain growth, increased tool head wear, and adhesion between the tool head and the raw material. Therefore, the preferred spindle speed is 500–3500 r / min, and the preferred system moment of inertia is 0.5–3.0 kg·m. 2 Axial load is used to provide particle compaction, increase contact area and drive plastic deformation. When the axial load is too low, it is difficult to close the pores inside the raw material layer. When the axial load is too high, it is easy to cause lateral extrusion of raw material, increased wear of tool head and increased risk of tool adhesion. Therefore, the axial load is preferably 5 to 30 kN. In some feasible implementations, the direction of the pulsed magnetic field in step S3 is along the horizontal direction of the raw material layer, used for microstructure control during the inertial friction-driven forming process. When the peak intensity of the pulsed magnetic field is too low, the magnetoplastic effect is insufficient to effectively promote dislocation pinning and dynamic recrystallization control. When the peak intensity is too high, equipment energy consumption increases significantly and generates additional induced heat effects on the forming zone. Therefore, the preferred magnetic field strength of the pulsed magnetic field is 0.5~5.0 T, the preferred pulse frequency is 1~50 Hz, and the preferred pulse width is 1~50 ms. For ferromagnetic metals (steel, iron-based alloys), the preferred peak intensity is 0.5~2.0 T; for paramagnetic metals (aluminum alloys, copper alloys), the preferred peak intensity is 2.0~5.0 T, the preferred pulse frequency is 1~50 Hz, and the preferred pulse width is 1~50 ms. The single-layer forming thickness and the action time affect the frictional heat transfer, plastic deformation depth, and interlayer bonding quality. When the single-layer thickness is too thin, the manufacturing efficiency is low. When the single-layer thickness is too thick, the shearing action is difficult to fully transfer to the lower part of the layer. Therefore, the preferred single-layer forming thickness is 0.5~3.0 T. The thickness can be mm, for example, 0.5 mm, 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, or 3.0 mm. The single-layer action time is preferably 5 to 40 seconds, for example, 5 seconds, 10 seconds, 20 seconds, 30 seconds, or 40 seconds. During the solid-state forming process, the forming substrate is cooled, and the cooling medium temperature is preferably 0 to 5°C. The peak temperature of the forming zone is controlled below the liquidus line of the material and dynamically adjusted in combination with the end face temperature of the tool head and the temperature of the forming zone to achieve the comprehensive goals of heat control, crystal control, and anti-adhesion.

[0046] Specifically, in the pulsed magnetic field-assisted solid-state forming process, this invention mainly utilizes the magnetoplastic effect on the solid-state regeneration process. By changing the spin state of the spin-electron pairs at the dislocation nucleus, it reduces the activation energy required for dislocations to overcome pinning obstacles (such as solute atoms, precipitated phases, and interfacial oxide films), promoting dislocation depinning and directional movement. Specifically, its effects on the solid-state regeneration of loose debris are as follows: ① It promotes dislocation depinning and directional movement at the particle interface, reduces the local deformation resistance at the particle interface, accelerates the breaking of the oxide film at the particle interface and atomic diffusion between particles, eliminates interfacial metallurgical bonding defects, and enables loose metal debris to form a dense, continuous block without internal interfacial defects in a short time; ② It promotes the dynamic recrystallization and uniform nucleation of metal debris during the intense plastic deformation process of inertial friction, ensuring the uniformity of the structure during solid-state regeneration and providing a stable metallurgical basis for the formation of ultrafine-grained structures; ③ It effectively inhibits abnormal grain growth during dynamic recrystallization, and, in conjunction with forced cooling, enables the regenerated metal material to obtain a uniform and stable ultrafine-grained structure, achieving a high-performance match of high strength and high plasticity in the regenerated material.

[0047] S4. Anti-adhesion tool retraction; after single-layer solid-state forming, reduce the axial load of the friction tool head to 0-30% of the forming load, and keep the friction tool head at 50-500... The tool exits the forming zone at a low speed (r / min) or in the opposite direction, while simultaneously cooling or maintaining the temperature of the friction tool head end face and the forming zone. This keeps the temperature of the friction tool head end face and the forming zone within a preset temperature window to prevent the friction tool head from adhering to the raw material layer or the formed layer. Specifically, when the metal material to be recycled is aluminum alloy, the temperature of the friction tool head end face is controlled at 200–350℃ after tool retraction, and the surface temperature of the forming zone is not higher than 250℃. When the metal material to be recycled is steel, the temperature of the friction tool head end face is controlled at 450–550℃ after tool retraction, and the surface temperature of the forming zone is controlled at 500–650℃. When the metal material to be recycled is an aluminum alloy-steel composite gradient material, temperature windows are set according to the composition ratio of different material layers. Specifically, the peak temperature of the forming zone of the aluminum alloy enriched layer is controlled at 420–500℃, the peak temperature of the forming zone of the aluminum-steel transition layer is controlled at 500–650℃, and the peak temperature of the forming zone of the steel enriched layer is controlled at 750–880℃.

[0048] In some feasible methods, during the process of the friction tool head retracting from the forming zone, auxiliary mechanisms such as gas blowing, scraping, or brushing can be used to effectively avoid surface tearing and tool head adhesion during the retraction process.

[0049] S5. Layer-by-layer deposition forming; After completing the single-layer forming, control the forming substrate and the friction tool head to feed relative to each other in the vertical direction, and repeat steps S1 to S4. The interlayer feed amount is preferably 0.5~3.0 mm to obtain recycled ultrafine crystalline material. In some feasible methods, the layer-by-layer deposition process also includes forced cooling and temperature control. During the inertial friction-driven solid-state forming process and the anti-adhesion tool retraction process, the forming area, friction tool head and / or forming substrate are forcibly cooled to suppress heat accumulation, grain growth and friction tool head adhesion, thereby promoting the acquisition of a uniform and stable ultrafine grain structure. When the temperature of the forming area and friction tool head is higher than the preset upper limit, the temperature of the tool head and forming area is reduced through liquid cooling channels, gas nozzles and tool head temperature control unit. When the temperature is lower than the preset lower limit, the cooling intensity is reduced or short-term heat preservation is performed to avoid insufficient plastic flow and insufficient interlayer bonding due to the initial temperature being too low when forming the next layer.

[0050] The technical solution of the present invention will be explained below with reference to specific embodiments.

[0051] Example 1 This embodiment uses 6061 aluminum alloy cutting chips as the main raw material, with some fine particles prepared as filler. The length of the cutting chips is 1.0–3.0 mm, and the particle size of the fine particles is 100–300 μm. The chips and fine particles are mixed at a mass ratio of 1:1. The raw material is pretreated by first placing the aluminum alloy chips and fine particles in a cleaning container, adding industrial alcohol, and stirring for 10–20 minutes to remove oil stains. After cleaning, the mixture is filtered and allowed to drain naturally. Then, a sieving device is used to separate the raw material into three grades: 100–300 μm fine particles, 0.3–1.0 mm particles, and 1.0–3.0 mm chips. After sieving, the raw material is placed in a vacuum drying oven and dried at 120°C for 2 hours. After drying, it is sealed and stored for later use. After treatment, the oxygen content of the raw material is controlled at 0.2%.

[0052] S1. Graded feeding: 100-300 μm fine particles are loaded into the first feeding unit, 0.3-1.0 mm particles are loaded into the second feeding unit, and 1.0-3.0 mm debris is loaded into the third feeding unit. The mass feeding ratio of the three feeding units is set to 2:3:5. The first layer of material is laid. The three feeding units are turned on, and the raw material forms a 1.0 mm thick material layer on the surface of the aluminum alloy forming substrate with a size of 100 mm × 100 mm × 10 mm. S2. Turn on the vibration leveling device and apply a low-frequency vertical vibration of 80 Hz and 0.5 mm to the forming substrate for 15 seconds. The vibration inertial force drives the aluminum alloy chips and fine particles to rearrange and fill, eliminating large pores in the layup and making the layup more uniform. After the vibration leveling is completed, turn off the vibration leveling device. S3. Activate the pulsed magnetic field auxiliary device to apply a pulsed magnetic field with a peak intensity of 3.0 T and a pulse frequency of 10 Hz to the forming zone along the horizontal direction of the raw material layer. Simultaneously, start the motor to drive the flywheel to store energy to the set state, then lower the friction tool head to the surface of the raw material layer and contact the raw material. Subsequently, control the flywheel to engage with the spindle, apply a 6 kN axial load, and the friction tool head, driven by inertial release, plastically deforms and compacts the raw material layer through rotational friction shearing and axial extrusion. During the forming process, maintain liquid cooling and continuously apply the pulsed magnetic field assistance, causing plastic flow and dense connection in the raw material layer. The peak temperature of the forming zone is controlled below the liquidus line of 6061 aluminum alloy.

[0053] S4. After the single-layer forming is completed, turn off the pulse magnetic field auxiliary device. The control system first reduces the axial load of the friction tool head to less than 10% of the forming load. Control the friction tool head to rotate at a low speed of 150 r / min to exit the forming area. During the tool retraction process, the gas nozzle is turned on simultaneously to spray and cool the end face of the friction tool head and the forming area for a short time. After the tool retraction is completed, the temperature of the end face of the friction tool head drops back to the preset temperature window (200~350℃), and the surface temperature of the forming area drops to below 250℃ to suppress heat accumulation and grain growth.

[0054] S5. Repeat steps S1-S4 for a total of 2 layers to form a 6061 aluminum alloy recycled material with a thickness of 2.0 mm.

[0055] The cross-section of the 6061 recycled aluminum alloy prepared in this embodiment showed no obvious macroscopic defects. Figure 3 Its microstructure is uniform, with an average grain size of 0.88 μm. Figure 4 The mechanical properties of the prepared 6061 recycled aluminum alloy were tested, and its stress-strain curve is shown in the figure. Figure 5 As shown, the tensile strength and elongation are 257 MPa and 25.4%, respectively, achieving an excellent balance between strength and plasticity.

[0056] Example 2 This embodiment uses a mixture of 45 steel grinding particles and steel powder as an example, selecting the particles and steel powder generated during the grinding process of 45 steel as raw materials. After impurity removal, sieving, and vacuum drying, the oxygen content of the raw materials is 0.28%.

[0057] S1. Graded feeding: 45-150 μm steel powder is loaded into the first feeding unit, and 150-800 μm steel particles are loaded into the second feeding unit. The mass feeding ratio is set to 3:2. The raw materials form a 0.8 mm thick raw material layer on the surface of a steel substrate with dimensions of 100 mm × 100 mm × 12 mm. S2. Turn on the vibration leveling device and apply vertical vibration with a frequency of 60 Hz and an amplitude of 1.0 mm to the forming substrate for 20 s to drive the steel powder and steel particles to rearrange and fill, eliminating large pores. S3. Turn on the pulsed magnetic field auxiliary device, apply a pulsed magnetic field with a peak intensity of 1.2 T to the forming zone, start the flywheel energy storage, and control the flywheel to engage with the main shaft after the set speed is reached. At the same time, apply an axial load of 22 kN to make the friction tool head perform inertial friction compaction on the ply material. The pulsed magnetic field is continuously applied during the forming process. S4. After the single-layer forming is completed, turn off the pulse magnetic field auxiliary device, control the system to reduce the axial load of the friction tool head to 15% of the forming load, and control the friction tool head to exit the forming area at a low speed of 200 r / min in reverse rotation. During the tool retraction process, the forced cooling device is started simultaneously to cool the forming area and the end face of the friction tool head to reduce the risk of tool retraction adhesion.

[0058] S5. Repeat the above steps to deposit 10 layers to finally obtain a recycled 45 steel sample.

[0059] The 45 steel prepared in this embodiment has a uniform microstructure with an average grain size of less than 1 μm, and a tensile strength and elongation of 670 MPa and 8%, respectively, achieving an excellent balance between strength and plasticity.

[0060] Example 3 In this embodiment, 6061 aluminum alloy fine particles (particle size 100-300 μm) and 45 steel particles (particle size 150-500 μm) were used. The two raw materials were degreased, sieved and vacuum dried respectively, and the oxygen content was controlled below 0.25%.

[0061] S1. Fine aluminum alloy particles are loaded into the first feeding unit, and steel particles are loaded into the second feeding unit. The feeding speed and start / stop sequence of the two feeding units are adjusted by the control system to form a raw material layer on the surface of the forming substrate with a gradually changing proportion of aluminum alloy to steel particles. The total number of stacked layers is 10, and the thickness of a single layer is 0.8 mm. Among them, the mass fraction of 6061 aluminum alloy particles in layers 1-3 is 100%; the mass fraction of 6061 aluminum alloy particles in layer 4 is 80%, and the mass fraction of 45 steel particles is 20%; the mass fraction of 6061 aluminum alloy particles in layer 5 is 60%, and the mass fraction of 45 steel particles is 40%; the mass fraction of 6061 aluminum alloy particles in layer 6 is 40%, and the mass fraction of 45 steel particles is 60%; the mass fraction of 6061 aluminum alloy particles in layer 7 is 20%, and the mass fraction of 45 steel particles is 80%; the mass fraction of 45 steel particles in layers 8-10 is 100%.

[0062] S2. Turn on the vibration leveling device. The vibration leveling parameters are: vibration frequency 70 Hz, amplitude 0.8 mm, vibration direction vertical, and vibration duration 15 s. S3. Activate the pulsed magnetic field auxiliary device to apply a pulsed magnetic field with a peak intensity of 2.0 T to the forming zone, with a pulse frequency of 20 Hz and a pulse width of 10 ms. Start the flywheel energy storage and control the flywheel to engage with the main shaft after reaching the set speed. At the same time, apply an axial load of 14 kN to make the friction tool head perform inertial friction compaction on the ply material. The pulsed magnetic field is continuously applied during the forming process. S4. After the single-layer forming is completed, turn off the pulse magnetic field auxiliary device, control the system to reduce the axial load of the friction tool head to 15% of the forming load, and control the friction tool head to exit the forming area at a low speed of 200 r / min in reverse rotation. During the tool retraction process, the forced cooling device is started simultaneously to cool the forming area and the end face of the friction tool head to reduce the risk of tool retraction adhesion.

[0063] S5. Repeat the above steps to deposit 10 layers, with a single layer feed thickness of 0.8 mm, and finally obtain the recycled composite material sample.

[0064] The recycled composite material prepared in this embodiment exhibits good shape and a gradient microstructure, achieving the goal of gradient material preparation. This embodiment demonstrates that the present invention can not only prepare recycled single-metal materials, but also achieve the mixed recycling of multiple materials.

[0065] Comparative Example 1 The comparative example is the same as the scheme of Example 1. The difference is that in step S3 of this comparative example, no pulsed magnetic field assistance and liquid cooling process are introduced. Only inertial friction driven solid-state forming is performed.

[0066] Compared to Example 1, the 6061 recycled aluminum alloy obtained in Comparative Example 1 retained a large number of impurities, such as Figure 6 As shown in (a), the uniformity of grain size distribution in the forming region is poor, and abnormal grain growth occurs in some areas, such as... Figure 6 As shown in (b), its tensile strength and elongation were 194 MPa and 18.8%, respectively, and its strength and plasticity were both lower than those of the sample obtained in Example 1.

[0067] The embodiments given above are preferred examples for implementing the present invention, and the present invention is not limited to the above embodiments. Any non-essential additions or substitutions made by those skilled in the art based on the technical features of the present invention are within the protection scope of the present invention.

Claims

1. A method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction, characterized in that, Includes the following steps: S1. After the pre-treated raw material to be recycled is laid in layers on the forming substrate to form a raw material layer, low-frequency vibration is applied to the forming substrate to cause the raw material layer particles to rearrange and fill. S2. Under the assistance of a pulsed magnetic field, the friction tool head of the inertial friction device is used to perform rotational friction shearing and axial extrusion on the raw material layer, causing the raw material to undergo plastic deformation and solid-phase forming. S3. After forming, turn off the pulse magnetic field and retract the tool to control the temperature of the friction tool head and the forming area; S4. Repeat steps S1 to S3, and deposit layer by layer to the target thickness to obtain a regenerated ultrafine crystalline material, wherein the average grain size in the regenerated ultrafine crystalline material is 0.1 μm to 1 μm.

2. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S1, the raw materials include one or more of metal powder, metal particles, and metal scrap; the metal powder has a particle size of 45~150 μm, the metal particles have a particle size of 150~1000 μm, and the metal scrap has a size of 1~5 mm.

3. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S1, low-frequency vibration is applied by a vibration leveling device. The vibration frequency is 20~200 Hz, the amplitude is 0.1~3.0 mm, the vibration direction is vertical, and the vibration time is 5~60 s.

4. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S2, the parameters of the inertial friction device are as follows: spindle speed 500~3500 r / min, system moment of inertia 0.5~3.0 kg·m², axial load 5~30 kN, single-layer solid phase forming thickness 0.5~3.0 mm, single-layer raw material layer action time 5~40 s, and controlled energy input density 0.5~2.0 J / mm². 2 .

5. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S2, the direction of the pulsed magnetic field is along the horizontal direction of the raw material layer, the magnetic field strength is 0.5~5.0 T, the pulse frequency is 1~50 Hz, and the pulse width is 1~50 ms.

6. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S2, during the solid-state forming process, the forming substrate is cooled, and the temperature of the cooling medium is 0 to 5°C; the peak temperature of the forming zone is controlled below the liquidus line of the material.

7. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S3, during the retraction process, the axial load of the inertial friction device is reduced to 0-30% of the forming load, and it exits at a low speed of 50-500 r / min or in the reverse rotation state.

8. The method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S3, during the tool retraction process, the end face of the friction tool head and the forming area are simultaneously cooled by short-term jetting to keep the temperature of the end face of the friction tool head and the surface temperature of the forming area within a preset temperature window that matches the metal material to be recycled.

9. A method for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction according to claim 1, characterized in that, In step S4, during the layer-by-layer stacking process, the forming substrate and the friction tool head are controlled to feed relative to each other in the vertical direction, and the interlayer feed amount is 0.5~3.0 mm.

10. A device for solid-phase regeneration of ultrafine-grained materials from metal waste driven by inertial friction, characterized in that, The device includes a forming chamber, a liftable platform installed at the bottom of the forming chamber, a forming substrate fixed on the liftable platform, a vibration leveling device connected to the forming substrate, an inertial friction device, a pulse magnetic field coil, a forced cooling device, a graded feeding device, and a control system. The inertial friction device is installed above the forming chamber and includes a flywheel assembly, a spindle assembly and a friction tool head connected in sequence. The friction tool head extends into the forming chamber and is located above the forming substrate. The pulsed magnetic field coils are mounted on both sides of the forming cavity via brackets; The forced cooling device includes a cooling channel disposed below the forming substrate and / or a gas nozzle facing the forming area, for cooling and temperature control of the forming area, the friction tool head and the forming substrate; The graded feeding device includes 2 to 5 sets of feeding units. Each set of feeding units is independently equipped with a hopper and a feeding pipe connected to the hopper. The outlets of each feeding pipe are arranged side by side along the material spreading direction. The control system is electrically connected to the inertial friction device, the graded feeding device, the vibration leveling device, the pulse magnetic field auxiliary device, the forced cooling device, and the feed clamping device, respectively.

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