A method for improving ultra-precision cutting performance of particle-reinforced metal matrix composites

Abstract

The present invention discloses a method for improving the ultra-precision cutting performance of particle-reinforced metal-based composite materials, belonging to the field of ultra-precision machining technology. The method of the present invention is specifically as follows: a dense and homogeneous metal film layer is coated on the ultra-precision machining surface of the particle-reinforced metal-based composite material; at the interface between the metal film layer and the particle-reinforced metal-based composite material, the metal atoms in the metal film layer are re-bonded with the metal atoms in the composite material and the brittle particle atoms; the coating method is specifically as follows: an electron beam is used to bombard the metal material to evaporate the metal material to obtain metal particles; the vaporized metal material encounters the ultra-precision machining surface of the particle-reinforced metal-based composite material, and gathers on the ultra-precision machining surface of the particle-reinforced metal-based composite material to form the metal film layer; the particle-reinforced metal-based composite material treated by the method of the present invention can significantly improve its ultra-precision plastic cutting performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of ultra-precision machining, and more specifically, relates to a method for improving the ultra-precision cutting performance of a particle-reinforced metal-based composite material. Background Art

[0002] Metal-matrix composites (MMCs) are increasingly being used in precision optics, aerospace, defense, and other fields due to their high strength-to-weight ratio, high stiffness, low thermal expansion coefficient, and corrosion and wear resistance. MMCs are typically composed of a heterogeneous mixture of lightweight metals such as aluminum, titanium, chromium, nickel, and copper, reinforced with metal or non-metallic particles, whiskers, or fibers. Particle-reinforced MMCs have become highly competitive composite materials due to their low cost, ease of fabrication, and isotropic properties.

[0003] In recent years, typical particle-reinforced metal matrix composites (PMMCs), such as silicon-aluminum alloys and aluminum-based silicon carbide (Al-SiC), have become the materials of choice for optical systems. The quality and high shape accuracy of their functional surfaces are closely linked to optical performance. Traditional grinding and polishing methods are characterized by long processing cycles and high costs, and they struggle to produce complex curved functional microstructures. Ultraprecision diamond turning technology, with its advantages of high machining freedom, high precision, and minimal subsurface damage, has proven to be an effective method for nanoscale surface machining and the preparation of microstructured functional surfaces. Plasticity-zone cutting is a key technology for achieving high-precision and low-damage surfaces. However, the silicon and silicon carbide particles in PRMs are hard and brittle, making them typically difficult to machine. The critical depth of cut (DOC) for the brittle-ductile transition (BDT) in ultraprecision diamond cutting of these materials is only 40 to 100 nm. This low material removal during plasticity-zone cutting places extremely high demands on machine tool rigidity and precision, and can easily lead to severe brittle fracture. Improving the critical DOC for the BDT of difficult-to-machine PRMMCs, improving machining efficiency, mitigating tool wear, and increasing total cutting distance, has been a major research challenge in ultraprecision machining. Furthermore, for particle-reinforced metal matrix composites such as silicon-aluminum alloys and aluminum-based silicon carbide, where the metal matrix has good plasticity, significant cutting differences can occur between brittle silicon particles, brittle silicon carbide particles, and soft aluminum metal. This can easily lead to machining defects such as particle spalling during ultra-precision diamond cutting. Therefore, this analysis shows that exploring innovative new process methods is of great significance for improving the cutting performance of particle-reinforced metal matrix composites.

[0004] Currently, pre-coating processes have shown some improvement in machining performance, but are still in the initial stages of exploration. Attempted coating materials include marking inks, wax coatings, and epoxy resin coatings. These coatings interact with the workpiece surface, altering its surface energy and affecting the micro-cutting process. These film-like materials exhibit low fracture strain and easily separate from the substrate during ultra-precision cutting, resulting in extremely unstable machining and reduced machining accuracy. Furthermore, these film-like materials exhibit poor adhesion to particle-reinforced metal matrix composites (PRMCs), and the coating process for composite substrates is unclear, making it impossible to guarantee uniform coating thickness. Currently, the mechanism by which coatings influence the brittle-ductile transition of PRMMCs has not been explored. Summary of the Invention

[0005] In response to the above-mentioned defects or improvement needs of the prior art, the present invention provides a method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composite materials, the purpose of which is to coat a dense and homogeneous metal film layer on the surface to be processed of the particle-reinforced metal matrix composite material, based on the strong bonding between the composite material atoms and the metal film atoms, thereby significantly improving the ultra-precision plastic cutting performance of the particle-reinforced metal matrix composite material.

[0006] To achieve the above objectives, the present invention provides a method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composites, the method specifically comprising:

[0007] A dense and homogeneous metal film layer is coated on the ultra-precision processed surface of the particle-reinforced metal matrix composite material. At the bonding surface between the metal film layer and the particle-reinforced metal matrix composite material, the metal atoms in the metal film layer are re-bonded with the particle atoms and metal atoms in the brittle particle-reinforced metal matrix composite material.

[0008] Furthermore, under the action of temperature increase or the combined action of temperature increase and pressure reduction, the metal is evaporated and gasified to obtain metal particles; the metal particles are attached to the particle-reinforced metal matrix composite material under the action of a magnetic field, a pressure difference, or the combined action of a magnetic field and a pressure difference to form a metal film layer.

[0009] Furthermore, the metal material is bombarded with an electron beam, and the kinetic energy of the electrons is converted into heat energy, causing the metal material to evaporate and vaporize to obtain metal particles. The metal particles encounter the surface of the particle-reinforced metal matrix composite material and gather on the surface to form the metal film layer.

[0010] Furthermore, under vacuum conditions, the filament is energized to generate an electron beam, which bombards a metal target in a container under the action of a magnetic field. An external cooling device is connected to the container for cooling. After the electrons bombard the metal target, kinetic energy is converted into thermal energy, causing the metal target to heat up and evaporate to obtain metal particles. The floating metal particles come into contact with the particle-reinforced metal matrix composite material above the metal target and then gather on the surface of the particle-reinforced metal matrix composite material to form the metal film layer.

[0011] Furthermore, the types of the particle-reinforced metal matrix composite material include silicon-aluminum alloy and aluminum-based silicon carbide.

[0012] Furthermore, the types of the metal film layer include aluminum, titanium, chromium, nickel and copper.

[0013] Furthermore, the particle-reinforced metal matrix composite material is a silicon-aluminum alloy; and the metal film layer is an aluminum film layer.

[0014] Furthermore, the thickness of the metal film layer is 100 nm to 200 nm; and the purity of the metal film layer is greater than 99%.

[0015] According to another aspect of the present invention, the present invention provides a particle-reinforced metal matrix composite material with improved ultra-precision cutting performance, characterized in that the particle-reinforced metal matrix composite material is prepared by a method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composite materials disclosed in the present invention.

[0016] In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:

[0017] (1) In the method of the present invention, after a layer of metal film with good ductility is coated on the surface of the particle-reinforced metal matrix composite material, on the one hand, because the metal atoms and the particles-reinforced metal matrix composite material atoms will re-bond, the metal film layer will play a tightening role on the micro cracks on the surface of the particle-reinforced metal matrix composite material, similar to a bandage; on the other hand, the gravity of the metal film layer itself will generate pressure on the surface of the particle-reinforced metal matrix composite material, inhibiting the expansion of micro cracks, and the metal film layer induces a high hydrostatic pressure-like effect on the surface of the particle-reinforced metal matrix composite material; at the same time, there is an influence zone of material deformation in the cutting process of the tool, and the influence zone of the metal film layer near the upper surface of the particle-reinforced metal matrix composite material hinders the expansion of cracks due to the impedance of the film layer;

[0018] (2) In the method of the present invention, a dense and uniform metal film layer is coated on the ultra-precision machined surface of the particle reinforced metal matrix composite material. After the tool cuts through the surface metal film layer, it evenly transitions to the cutting of the particle reinforced metal matrix composite material. During the cutting process, the particle reinforced metal matrix composite material pushes the metal film layer forward. The metal film layer has a resistance to the particle reinforced metal matrix composite material. This pressure of resisting deformation makes the cutting force more stable. In this case, the pressure caused by chip formation will cause the metal film layer above the particle reinforced metal matrix composite material to accumulate and produce some cracks. On the other hand, the metal film provides resistance to the normal flow of the particle reinforced metal matrix composite material. In addition, considering the difference in friction coefficients between the chip-tool and the chip-metal film, stress and microcracks will be generated in the chip area. Subsequently, as the tool further advances, the chip is broken, and the metal film on it has the ductility of the metal and curls. In addition, due to the presence of the metal film, the crushing impact and ejection of the chip during cutting are controlled to a certain extent. In this case, the particle reinforced metal matrix composite material debris will be further refined due to the extrusion of the metal film and the tool surface, and a part of it will adhere to the metal film.

[0019] (3) In the method of the present invention, due to the special properties of the composite of soft metal and hard particles, the particle-reinforced metal matrix composite material has significant cutting differences in ultra-precision machining. During tool cutting, the soft metal has good plastic fluidity, while the brittle particles first produce cracks and machining defects at the interface with the soft metal. The metal film layer provides tension for the combination of the brittle particles and the soft metal, which significantly inhibits the propagation of interface cracks during machining. Therefore, after the particle-reinforced metal matrix composite material is plated with a metal film layer, the critical cutting depth, machining accuracy and cutting performance of the material are significantly improved under ultra-precision machining conditions.

[0020] (4) In the method of the present invention, the particle-reinforced metal matrix composite material is preferably a silicon-aluminum alloy, and the metal film layer is preferably an aluminum film. The aluminum matrix in the silicon-aluminum alloy and the plated aluminum film are the same element and have a strong bonding force. The silicon in the silicon-aluminum alloy and the plated aluminum film both have a face-centered cubic crystal structure and have the same atomic arrangement rules, and are easy to combine.

[0021] (5) Compared with other coating methods, in the method of the present invention, the electron beam can accurately bombard the metal target through the magnetic field, generating a large amount of heat at a precise position, making the metal target evaporate easily and quickly, thereby achieving efficient coating on the substrate material; and the energy of the electron beam is directly brought to the surface of the target by the bombarded electrons, reducing the heat radiation and energy loss in the process, and can prepare a metal film layer with good uniformity;

[0022] (6) In the method of the present invention, the container for placing the metal target is connected to an external cooling device, which avoids evaporation and gasification of the container during the coating process and also avoids physical and chemical reactions between the container and the metal target at high temperatures, thereby effectively improving the purity of the metal film layer;

[0023] (7) In the method of the present invention, the metal particles float and contact the particle-reinforced metal matrix composite material above the metal target to form the metal film layer. This process does not require the support of a magnetic field and will not produce uncertain interference effects on the bombarded metal particles; it is conducive to the formation of a uniform and dense metal film layer;

[0024] (8) In the method of the present invention, considering that the critical cutting depth of brittle-ductile transition in ultra-precision diamond cutting of typical difficult-to-machine particle-reinforced metal matrix composites is only 40nm to 100nm, and the actual cutting depth of ultra-precision machining is at the micron level (1 micron to 10 microns), therefore, in order to achieve the best ultra-precision cutting performance of the particle-reinforced metal matrix composites, the thickness of the metal film layer is controlled between 100nm and 200nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the overall flow chart of an embodiment of the present invention;

[0026] Figure 2 Schematic diagram of the principle of metallization film layer in an embodiment of the present invention;

[0027] Figure 3 is a schematic diagram of the interaction between the metal film layer, the particle-reinforced metal matrix composite material and the diamond tool in an embodiment of the present invention;

[0028] Figure 4 Schematic diagram of the principle of the metal film layer improving the ultra-precision cutting performance of the particle-reinforced metal matrix composite material in the method of the present invention;

[0029] Figure 5 is a schematic diagram of the process of ultra-precision diamond variable depth cutting of metal-coated particle-reinforced metal matrix composite materials; Figure 5(a) is a schematic diagram of the first stage of variable depth cutting; Figure 5(b) is a schematic diagram of the second stage of variable depth cutting; Figure 5(c) is a schematic diagram of the third stage of variable depth cutting; and Figure 5(d) is a schematic diagram of the fourth stage of variable depth cutting. DETAILED DESCRIPTION

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to illustrate the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0031] In order to reflect the technical advantages of the method of the present invention, a comparative experiment method is now used for demonstration:

[0032] like Figure 1 As shown, the left part is the ultra-precision machining process of non-coated particle reinforced metal matrix composite materials, and the right part is the ultra-precision machining process of particle reinforced metal matrix composite materials after coating with metal film layer; among them, particle reinforced metal matrix composite materials are made of silicon aluminum alloy and aluminum-based silicon carbide, and the coating metals are made of aluminum, titanium, chromium, nickel and copper; the coating method adopts electron beam evaporation coating; ultra-precision machining adopts variable cutting depth to explore the effect of plasticity improvement, the cutting depth varies from 0 to 2 microns, and the cutting speed is 200mm / min.

[0033] Comparison of the transverse morphologies of grooves produced by variable-depth cutting of metal-coated and uncoated PRMCs under a metallographic microscope and a white-light detector reveals distinct groove formation processes. In the uncoated PRMC, grooves form immediately upon contact of the diamond tool with the PRMC surface. As the depth of cut increases, the PRMC undergoes elastic and plastic deformation, beginning to undergo fine fragmentation. With increasing depth of cut, the PRMC enters a complete fragmentation phase, until the diamond tool leaves the PRMC surface, forming a complete groove. In contrast, in groove cutting of PRMCs coated with a 200nm metal film, the diamond tool tip contacts the metal film surface, plastically cutting the film. After a smooth surface is created, the PRMC begins to form a groove. The groove edge is a smooth band of metal film, indicating strong adhesion and close bonding between the metal film and the PRMC surface. The cushioning effect of the metal film significantly extends the plastic region of the coated PRMC, significantly increasing the critical depth of cut. Comparing the complete disintegration stage, the uncoated PRMMC exhibits dense, large-particle cleavage disintegration, while the coated PRMMC exhibits sparse, small-particle disintegration concentrated in the center of the groove. The difference in the groove formation process between the coated and uncoated PRMMCs reflects the influence of the coating on the cutting performance of the PRMMCs. This shows that coating the PRMMCs with a metal film can effectively improve their ultra-precision machining performance.

[0034] like Figure 2 As shown, electron beams are used to bombard the metal coating material. The electrons' kinetic energy is converted into heat, causing the coating material to vaporize and evaporate. In an ultra-high vacuum chamber, these vaporized materials encounter new interfaces and reassemble to form a new film layer. Electron beam evaporation can produce high-purity, high-precision thin films. This coating method allows for controlled film thickness and excellent uniformity. Furthermore, the entire electron beam evaporation process is performed within a vacuum chamber, ensuring that the film material is free of impurities and of high purity.

[0035] The following examples illustrate how to plate a metal film on a particle-reinforced metal matrix composite material. The particle-reinforced metal matrix composite material used in the example is a silicon-aluminum alloy with a size of Φ15mm×3mm. The silicon-aluminum alloy sheet is placed in an ultrasonic cleaner and cleaned with alcohol for 3 minutes. It is then repeatedly rinsed with distilled water and blown dry. First, the experimental instrument is placed in a vacuum state. The experimental temperature during the entire process is room temperature 25°C. The background vacuum during film deposition is less than 8.0×10 - 6 torr, the target material used is high-purity aluminum particles (99.98%); the electron gun acceleration voltage used in the electron beam evaporation coating system is 8kV, the electron beam current is about 80-90mA, the sputtering rate adjustment range is within 0.6nm / s, and the metal aluminum film thickness is set to 200nm.

[0036] Figure 3 This diagram illustrates the interaction between the metal film, particle-reinforced metal matrix composite (PRMC), and diamond tool. It demonstrates the interaction between the diamond tool tip and the PMC, and the combined deformation of the PMC and the metal film during ultra-precision diamond plastic cutting of a PMC coated with a metal film. Within the PMC's plastic domain, the metal film and the PMC combine to form a bond between the metal atoms and the PMC, effectively suppressing brittle fracture of the machined surface of the PMC by inhibiting the fracture of the formed chips. Within the PMC's plastic domain, the tool tip and dislocations generated by the PMC shift along the slip planes of the grains, causing plastic deformation of the material and enabling plastic domain machining.

[0037] Figure 4This is a schematic diagram of the principle of the method of the present invention. In ultra-precision machining, the original defects on the surface of the particle-reinforced metal matrix composite material often lead to crack initiation and expansion under the action of stress concentration, thereby causing severe brittle fracture. At the same time, due to the significant cutting differences between the metal and the brittle particles in the particle-reinforced metal matrix composite material, the brittle particles will first produce intergranular cracks along the interface. In this method, after a layer of ductile metal film is evaporated on the surface of the particle-reinforced metal matrix composite material, the film layer will play a tightening role on the original defects on the surface of the particle-reinforced metal matrix composite material, similar to a bandage, providing high hydrostatic pressure in the micro-cutting area and generating compressive stress on the sub-surface defects to prevent crack propagation. On the other hand, the gravity of the metal film layer itself will exert pressure on the surface of the particle-reinforced metal matrix composite material, inhibiting the expansion of microcracks. At the same time, the diamond tool will also be affected by the obstructive force of the film layer during the cutting process, making the cutting process more stable. In addition, under the action of the uniform tension of the metal film layer, the metal matrix and particles in the particle-reinforced metal matrix composite material are tightened, thereby increasing the interface strength, inhibiting intergranular cracks to a certain extent, and effectively reducing the processing defects of particle peeling.

[0038] Figures 5(a) to 5(d) This is a schematic diagram of the process of ultra-precision diamond variable cutting depth cutting of metal-coated particle reinforced metal matrix composite materials.

[0039] As shown in Figure 5(a), the diamond tool evenly transitions to cutting the particle-reinforced metal matrix composite after cutting through the metal film layer.

[0040] As shown in Figure 5(b), when the diamond tool cuts into the particle reinforced metal matrix composite, because the metal film layer and the particle reinforced metal matrix composite have a strong interface bonding force, when the cutting depth is shallow, the particle reinforced metal matrix composite chip pushes the film layer forward, and the metal film layer will resist the chip of the particle reinforced metal matrix composite. This pressure of resisting deformation will make the cutting force more stable. At this time, the metal film layer is strongly bonded to the particle reinforced metal matrix composite, and the metal film layer produces plastic accumulation. Considering the difference in chip-tool and chip-metal friction coefficients, stress and microcracks will be generated in the chip area. The microcracks are suppressed by the impedance of the metal film layer at the interface between the metal film layer and the particle reinforced metal matrix composite. At the same time, part of the energy of crack propagation is absorbed by the film layer. The generation and propagation of cracks occur more in the metal film layer, thereby suppressing the propagation of small cracks on the surface of the particle reinforced metal matrix composite. This is the simultaneous plastic flow of the metal film layer and the particle reinforced metal matrix composite, which can realize the plastic domain processing of the particle reinforced metal matrix composite.

[0041] As shown in Figure 5(c) and (d), as the depth of the diamond tool cutting the particle-reinforced metal matrix composite material continues to increase, the deformation of the particle-reinforced metal matrix composite material breaks through the impedance of the metal film layer, the metal film layer separates from the particle-reinforced metal matrix composite material, and the continuous chips break. At this time, the cracks on the processed surface expand, and the material enters the initial brittle cutting stage. The metal film layer on it still has good ductility and curls; however, due to the presence of the metal film layer, the crushing impact and ejection of the chips during cutting can be controlled to a certain extent; as the cutting depth increases further, the particle-reinforced metal matrix composite material debris will be further refined due to the extrusion of the metal film and the tool surface, and a large amount of it will adhere to the metal film layer; therefore, after being coated with the metal film layer, the plastic machinability of the particle-reinforced metal matrix composite material is significantly improved under ultra-precision diamond cutting conditions.

[0042] Those skilled in the art will readily understand that the above descriptions are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composite materials, characterized in that: The method specifically comprises: coating an ultra-precision machined surface of a particle-reinforced metal matrix composite material with a dense and homogeneous metal film layer; bombarding the metal material with an electron beam, converting the kinetic energy of the electrons into heat energy, causing the metal material to evaporate and vaporize to obtain metal particles; the metal particles encounter the surface of the particle-reinforced metal matrix composite material and aggregate on the surface to form the metal film layer; and at the interface between the metal film layer and the particle-reinforced metal matrix composite material, metal atoms in the metal film layer re-bond with brittle particle atoms and metal atoms in the particle-reinforced metal matrix composite material. The particle-reinforced metal matrix composite material is a silicon-aluminum alloy; the metal film layer is an aluminum film layer; the film layer tightens the original defects on the surface of the particle-reinforced metal matrix composite material, provides high hydrostatic pressure in the micro-cutting area, and generates compressive stress on sub-surface defects to prevent the expansion of cracks.

2. The method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composite materials according to claim 1, characterized in that: Under vacuum conditions, the filament is energized to generate an electron beam. Under the action of a magnetic field, the electron beam bombards a metal target in a container. An external cooling device is connected to the container for cooling. After the electrons bombard the metal target, kinetic energy is converted into thermal energy, causing the metal target to heat up and evaporate to obtain metal particles. The floating metal particles come into contact with the particle-reinforced metal matrix composite material above the metal target and then gather on the surface of the particle-reinforced metal matrix composite material to form the metal film layer.

3. The method for improving the ultra-precision cutting performance of particle-reinforced metal matrix composite materials according to claim 1, characterized in that: The thickness of the metal film layer is 100nm~200nm; the purity of the metal film layer is greater than 99%.

4. A particle-reinforced metal matrix composite material for improving ultra-precision cutting performance, characterized in that: The particle-reinforced metal matrix composite material is prepared by using a method for improving the ultra-precision cutting performance of a particle-reinforced metal matrix composite material disclosed in any one of claims 1 to 3.

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