Preparation method for improving micro-area mechanical property of metal-based composite material

Abstract

The invention discloses a preparation method for improving the micro-area mechanical property of a metal-based composite material, and belongs to the technical field of metal alloy composites.The preparation method comprises the steps that two-dimensional or three-dimensional fiber woven bodies are prepared and placed in a clamp after being stacked, and PyC, Si C, BN and other interfaces are deposited on the surfaces of fiber sheet layers through a chemical vapor deposition method. Soaking the pretreated fiber sheet in nickel nitrate solutions with different concentrations, drying, and putting into a CVD (Chemical Vapor Deposition) furnace, so that the silicon carbide nanowire is grown on the fiber surface, and a multi-layer interface is deposited; and then, an extrusion casting method is adopted for combining the fiber prefabricated body and metal alloy, and the metal-based composite material which is excellent in performance and uniform in structure is prepared through specific process steps. The method is combined with a preparation method of a ceramic-based composite material, so that the mechanical property of the material is greatly improved.

Description

Technical Field

[0001] The present invention relates to the technical field of metal alloy composite materials, in particular to a preparation method for improving the micro-region mechanical properties of metal matrix composite materials. Background Art

[0002] Metal-based composite materials have better performance and are more widely used, with many applications in aerospace, automotive, electronics and other fields. Light weight, high strength, good thermal conductivity, and good corrosion resistance are some of the more notable features of metal-based composite materials. However, existing methods for preparing metal-based composite materials have limitations. These methods may make it difficult to achieve a completely uniform microstructure, resulting in insufficient performance stability, affecting the reliability and service life of the final product. Therefore, it is particularly necessary to find a preparation method that improves the performance and organization of composite materials. With the advancement of science and technology, the use of nanoparticle reinforcement, interface engineering technology and other means can effectively improve the strength and toughness of aluminum-based composite materials, while reducing stress concentration and reducing the difference in thermal expansion coefficient, thereby significantly improving their comprehensive physical properties.

[0003] Existing fibers possess a range of unique properties, including high-temperature resistance, friction resistance, thermal conductivity, corrosion resistance, high elastic modulus, low thermal expansion coefficient, excellent stability, and excellent fatigue resistance. Combining the advantages of fibers and metal alloys to develop fiber-reinforced metal matrix composites is a current research hotspot. Exploring the preparation of fiber-reinforced metal matrix composites will yield composites with even better performance.

[0004] CVD technology deposits solid substances on the surface of the fiber body through gas-phase chemical reactions, thereby preparing the required nanomaterials. In the process of preparing silicon carbide nanowires (SiCNWs), it is usually necessary to decompose a gaseous precursor containing silicon and carbon elements (such as trichloromethylsilane, etc.) at high temperature, and grow silicon carbide nanowires on the substrate under the action of a catalyst. CVD technology can produce SiCNWs with small diameter, long length and high crystallinity. These nanowires have excellent mechanical properties. SiCNWs have broad application prospects in electronic devices, optoelectronic devices, sensors, composite materials and other fields, and CVD technology provides reliable technical support for their preparation.

[0005] Currently, common methods for preparing silicon carbide nanowire-reinforced metal matrix composites include melt infiltration and powder metallurgy. In melt infiltration, the fibers are easily damaged during the molten state impregnation process, affecting their overall performance and uniformity. In powder metallurgy, the reinforcement is mixed with metal powder and then subjected to high temperature and high pressure to form a dense microstructure. However, the introduction of a large number of metal particles can lead to internal voids during sintering, compromising the material's integrity and mechanical properties.

[0006] Therefore, providing a preparation method that can improve the micro-region mechanical properties of metal matrix composite materials is a problem that needs to be solved at present. Summary of the Invention

[0007] The purpose of the present invention is to provide a preparation method for improving the micro-region mechanical properties of metal matrix composite materials, so as to solve the problems of low integrity and mechanical properties of metal alloy composite materials prepared by existing methods.

[0008] To achieve the above object, the present invention provides a preparation method for improving the micro-region mechanical properties of metal matrix composite materials, comprising the following steps:

[0009] Step 1: Selecting fiber substrates and metal alloy substrates: 1) Selecting continuous reinforcing fibers, cutting them into fiber braids of a certain specification, stacking them, and then placing the assembly into a dedicated positioning fixture and adjusting the fixture to secure it; 2) Selecting different metal alloys;

[0010] Step 2: Debinding of continuous fiber sheets: The fiber sheets are placed in a CVD tube furnace, and argon gas is introduced at a flow rate of 10-500 ml / min, and the temperature is kept at 600-1200°C for 1-3 hours to remove the binder;

[0011] Step 3: Depositing an interface layer. In a chemical vapor deposition process, the fiber sheet is placed in a CVD tube furnace, and the CVD tube furnace is programmed to heat the fiber sheet to 500-1500°C at a rate of 5-100°C / min. During the heating process, the furnace is first evacuated to a vacuum using a vacuum pump, and then an inert gas is introduced as a protective gas. The process of depositing the interface layer is as follows: when the reaction system reaches a predetermined process temperature, a constant temperature control program is started to maintain the thermal field of the equipment, reaction gas is introduced, and the pressure control element is adjusted to maintain the pressure in the equipment. The reaction gas deposits an interface layer on the surface of the fiber sheet. The interface layer includes one or more of PyC, SiC, BN, etc.

[0012] Step 4: Soaking in nickel nitrate solution: First, prepare a nickel nitrate / ethanol precursor system, use nickel nitrate hexahydrate crystals to prepare solutions of different concentrations between 0.001-1.8 mol / L by precise weighing, select a fiber sheet prepared by chemical vapor deposition as a substrate, and deposit one or more layers of a composite structure of a PyC interface, a SiC interface, and a BN interface on the fiber sheet. Soak in the prepared solutions of different concentrations for 8-24 hours, take out, and dry them in a drying oven to obtain a catalyst-loaded fiber sheet;

[0013] Step 5, growing nanowires and multilayer interfaces: placing the fiber sheet preform loaded with the catalyst into a CVD tube furnace, heating it to 500-1500°C under an inert gas atmosphere, introducing H2, reducing the catalyst to metallic Ni under the H2 atmosphere, using CH3SiCl3 as a precursor raw material, and H2 as a diluent gas and carrier gas to obtain a fiber sheet preform with SiCNWs; then placing the fiber sheet preform with SiCNWs into a CVD tube furnace, heating it to 500-1500°C under an inert gas atmosphere, introducing H2, and reducing the catalyst to metallic Ni under the H2 atmosphere. After heating to 500-1500°C under atmosphere, H2 is first introduced as dilution gas, followed by H2 as carrier gas. The pipeline is then cleaned with H2, and CH4 is introduced to coat the SiCNWs surface with a layer of PyC interface. After maintaining this for 10-60 minutes, both H2 channels are opened, with the H2 flow rate for dilution at 20-100 ml / min and the H2 flow rate for carrier gas at 40-200 ml / min, so that the PyC interface is coated with a layer of SiC interface.

[0014] Step 6: Extrusion casting of metal-based composite materials: First, place the metal alloy on top of the fiber sheet preform. In an argon atmosphere, set the temperature to 700-900°C and keep it warm for a period of time to allow the metal alloy to fully melt. Then, apply a pressure of 10-200MPa. When the pressure ends, the preform solidifies and hardens, and the desired composite material is obtained.

[0015] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal matrix composite materials, in step 1, the continuous reinforcing fibers are selected from a continuous high-performance fiber system, specifically including carbon fibers, alumina fibers, ceramic-based fibers, metal whiskers, glass fibers, aramid fibers, and biomass-derived fibers; each fiber reinforcement has the following characteristic parameters:

[0016] Morphological parameters: diameter distribution 5-200 μm (CV value ≤ 5%);

[0017] Physical properties: Apparent density ρ = 1.4 ~ 3.9 g·cm -3 (ASTM D792 standard);

[0018] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal-based composite materials, in step 1, the metal alloy includes: aluminum alloy, magnesium alloy, titanium alloy, copper alloy, and nickel alloy.

[0019] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal-based composite materials, in step 2, the glue content of various fiber sheets is calculated to be 1-3% by the mass difference before and after degumming, and the glue weight is removed first when calculating the weight gain of subsequent fiber sheet samples.

[0020] Preferably, in the above-mentioned preparation method for improving the mechanical properties of metal matrix composite materials in micro-regions, in step 3, the processes of depositing the interfaces of PyC, SiC, and BN are as follows:

[0021] Deposition of PyC interface: When the reaction system reaches the predetermined process temperature, start the constant temperature control program to maintain the thermal field of the CVD tube furnace for 1-6 hours, introduce CH4 gas at a flow rate of 50-200 ml / min, adjust the vacuum valve to maintain the furnace pressure at 0-20 kPa, and the CH4 is pyrolyzed at high temperature to deposit a layer of PyC interface on the surface of the fiber layer;

[0022] Deposition of SiC interface: When the reaction system reaches the predetermined process temperature, start the constant temperature control program to maintain the thermal field of the CVD tube furnace for 1-10 hours, and introduce H2 into two pipelines for dilution and carrier gas respectively. The furnace pressure is maintained at 0-20KPa. The H2 used as dilution gas is directly introduced into the tube furnace, and the H2 used as carrier gas passes through the tank containing MTS and then enters the CVD tube furnace. The flow rate of hydrogen for dilution and carrier gas is controlled at 1:1-5. The gas passes through the CVD tube furnace and deposits a layer of SiC interface on the sample surface at high temperature.

[0023] Deposition of BN interface: When the reaction system reaches the predetermined process temperature, the constant temperature control program is started to maintain the thermal field of the CVD tube furnace for 1-5 hours, and the BCl3 and NH3 dual gas supply systems are opened simultaneously. The volume flow ratio of the two precursor gases is adjusted to 1:1-5 through the mass flow controller. Under the action of carrier gas transportation, the mixed gas undergoes a vapor deposition reaction in the pyrolysis reaction zone, and finally forms a BN interface layer with controllable thickness on the surface of the fiber sheet. Its crystal morphology is positively correlated with the reaction kinetic conditions.

[0024] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal-based composite materials, in step three, the deposition of PyC and SiC interfaces is carried out at a temperature of 1000-1500°C, and the gas pressure in the furnace is controlled to be 0-20KPa; the deposition of BN interfaces is carried out at a temperature of 500-1300°C, and the gas pressure in the furnace is maintained in a vacuum state.

[0025] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal-based composite materials, in step four, the nickel nitrate is Ni(NO3)2·6H2O with a purity greater than 99.0%, the concentration of the ethanol solution is 95%, and the soaked fiber sheet is dried in a drying oven at a temperature of 30-180°C for 3-12 hours to achieve the attachment of catalyst particles to the surface.

[0026] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal-based composite materials, in step five, during the growth of nanowires, the flow ratio of MTS and H2 in the carrier gas is controlled to be 1:6-12; in the process of covering the surface of SiCNWs with a layer of PyC interface, the time for first introducing H2 for dilution is 30-60 minutes, the flow rate is 20-100 ml / min, the flow rate of H2 introduced as a carrier gas is 40-200 ml / min, the time for simultaneous introduction of the two routes is 1-2 hours, the time for cleaning the pipeline with H2 is 10-40 minutes, and the flow rate of CH4 introduced is 50-200 ml / min.

[0027] Preferably, in the above-mentioned preparation method for improving the micro-region mechanical properties of metal matrix composite materials, in step six, the pressure is set at about 85 MPa and the temperature is set at 850° C. during the extrusion casting process.

[0028] Therefore, the present invention adopts the above-mentioned preparation method for improving the micro-region mechanical properties of metal matrix composite materials to obtain the following beneficial effects:

[0029] 1) The present invention utilizes chemical vapor deposition technology to sequentially coat the fiber surface with multiple interfaces, including PyC, SiC, and BN. By adjusting factors such as pressure, gas, temperature, and time, the desired interface thickness is achieved on the material surface. This reduces interfacial reactions during the fusion of the fiber and metal alloy, preventing unnecessary damage and helping to improve the overall toughness and bending resistance of the material. The results achieved by this invention will facilitate the research, development, and application of this novel composite material.

[0030] 2) The present invention can control the growth density and diameter of SiCNWs on the fiber surface by controlling the concentration of the catalyst solution. By adjusting process parameters such as growth temperature, MTS / H2 concentration, and catalyst concentration, the controllable growth of SiCNWs on the fiber surface is achieved. The growth of nanowires on the material surface can further increase the density at the microscopic level, reduce the number of cracks and voids, and thus enhance the hardness and strength of the material in the micro-region.

[0031] 3) The silicon carbide nanowire-reinforced aluminum-based composite material of this invention is produced using an extrusion casting method. Vertical injection molding effectively reduces the formation of pores and significantly improves the material's density. Under high pressure, the alloy particles are squeezed into finer, denser shapes.

[0032] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a flow chart for preparing the silicon carbide nanowire reinforced aluminum-based composite material in Example 1 of the present invention;

[0034] Figure 2 This is a scanning electron microscope (SEM) morphology image of silicon carbide nanowires on a carbon fiber braid in Example 1 of the present invention;

[0035] Figure 3 This is a scanning electron microscope (SEM) morphology image of the silicon carbide nanowire reinforced aluminum matrix composite material in Example 1 of the present invention;

[0036] Figure 4 This is an energy dispersive spectrum (EDS) diagram of the silicon carbide nanowire reinforced aluminum matrix composite material in Example 1 of the present invention;

[0037] Figure 5 This is a scanning electron microscope (SEM) fracture image of the silicon carbide nanowire reinforced aluminum matrix composite material in Example 1 of the present invention;

[0038] Figure 6 XRD spectra of the silicon carbide nanowire reinforced aluminum-based composite materials in Example 1 and Comparative Example 2 of the present invention;

[0039] Figure 7 The three-point bending-stress-strain curves of the carbon fiber aluminum-based composite materials in Examples 1, 2, 3, and 4 of the present invention and Comparative Examples 1 and 2 are shown. DETAILED DESCRIPTION

[0040] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0041] The terms used in the embodiments of the present invention are for the purpose of describing specific embodiments only and are not intended to limit the present invention. The singular forms "a," "an," "the," and "the" used in the embodiments of the present invention and the appended claims are also intended to include plural forms, and unless the context clearly indicates otherwise, "a plurality" generally includes at least two.

[0042] It should also be noted that the terms "include," "comprises," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a product or device comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such product or device. In the absence of further limitations, an element defined by the phrase "comprises a..." does not exclude the presence of other identical elements in the product or device comprising the element.

[0043] The present invention provides a preparation method for improving the micro-region mechanical properties of metal matrix composite materials, such as Figure 1 As shown, the method includes:

[0044] Step 1: Providing fiber substrate and metal alloy substrate:

[0045] Specifically, continuous reinforcing fibers such as carbon fiber, alumina fiber, ceramic fiber, metal fiber, glass fiber, aramid fiber, and natural fiber are selected and cut into fiber braids of certain specifications. These are then stacked and the assembly is placed in a dedicated positioning fixture and fixed with a clamp.

[0046] The fiber reinforcement phase is selected from a continuous high-performance fiber system, specifically including carbon fiber, alumina fiber, ceramic-based fiber, metal whisker, glass fiber, aramid fiber and biomass-derived fiber. Each fiber reinforcement has the following characteristic parameters:

[0047] Morphological parameters: diameter distribution 5-200 μm (CV value ≤ 5%);

[0048] Physical properties: Apparent density ρ = 1.4 ~ 3.9 g·cm -3 (ASTM D792 standard);

[0049] Specifically, different metal alloys are selected;

[0050] The metal alloys include aluminum alloys, magnesium alloys, titanium alloys, copper alloys, nickel alloys, and the like.

[0051] Step 2: Continuous fiber sheet degumming:

[0052] Specifically, the fiber sheet is placed in a CVD tube furnace, argon gas is introduced at a flow rate of 10-500 ml / min, and the temperature is kept at 600-1200°C for 1-3 hours to remove the glue; the glue content of each type of fiber is calculated to be 1-3% based on the mass difference before and after degumming. The glue weight of subsequent samples is removed first when calculating the weight gain.

[0053] Step 3: Deposit the interface layer:

[0054] Specifically, in the chemical vapor deposition process, the fiber sheet is placed in a CVD furnace, and the tube furnace program is set to heat it to 500-1500°C at a rate of 5-100°C / min. During the heating process, the furnace pressure is first evacuated to a vacuum using a vacuum pump, and then an inert gas is introduced as a protective gas. The processes for depositing PyC, SiC, and BN interfaces are as follows:

[0055] Deposition of the PyC interface: When the reaction system reaches the predetermined process temperature, the thermostat is activated to maintain the thermal field of the tube furnace for 1-6 hours. CH4 gas is introduced at a flow rate of 50-200 ml / min, and the vacuum valve is adjusted to maintain the furnace pressure at 0-20 kPa. The CH4 is pyrolyzed at high temperature to deposit a PyC interface layer on the surface of the fiber layer.

[0056] Deposition of SiC interface: When the reaction system reaches the predetermined process temperature, start the constant temperature control program to maintain the hot field of the tube furnace for 1-10 hours. At this time, stop the introduction of CH4 and introduce H2 through two pipelines for dilution and carrier gas respectively. The furnace pressure is maintained at 0-20KPa. The H2 used as dilution gas is directly introduced into the tube furnace, and the H2 used as carrier gas passes through a tank containing MTS. The flow rate of hydrogen for dilution and carrier gas is controlled at 1:1-5. The gas passes through the tube furnace and deposits a layer of SiC interface on the surface of the fiber layer at high temperature.

[0057] Deposition of the BN interface: When the reaction system reaches the desired process temperature, a constant temperature control program is activated to maintain the thermal field in the tube furnace for 1-5 hours. The dual gas supply system for BCl3 and NH3 is simultaneously activated, and the volumetric flow ratio of the two precursor gases is controlled to a range of 1:1-5 using mass flow controllers. Under the action of carrier gas, the mixed gas undergoes a vapor deposition reaction within the pyrolysis reaction zone, ultimately forming a BN interface layer of controllable thickness on the fiber sheet surface. The crystal morphology of the layer is positively correlated with the reaction kinetics.

[0058] Specifically, the PyC and SiC interface deposition is performed at a temperature of 1000-1500°C, with the furnace pressure controlled at 0-20 kPa. The BN interface deposition is performed at a temperature of 500-1300°C, with the furnace pressure maintained at a vacuum state. Depositing the SiC interface on the fiber surface facilitates the growth of SiC nanowires on the fiber surface, as the lattice mismatch between the SiC interface and the nanowires is lower, promoting their growth.

[0059] Step 4: Soak in nickel nitrate solution:

[0060] Specifically, a nickel nitrate / ethanol precursor system was first prepared, using nickel nitrate hexahydrate crystals (Ni(NO3)2·6H2O) to prepare solutions of varying concentrations between 0.001 and 1.8 mol / L by precise weighing. A fiber sheet reinforcement prepared by chemical vapor deposition (a composite structure with one or more layers of pyrolytic carbon, silicon carbide, and boron nitride interfaces) was selected as the substrate and immersed in the prepared solutions of varying concentrations for 8-24 hours. The substrate was then removed and dried in a drying oven.

[0061] The nickel nitrate is Ni(NO₃)₂·6H₂O with a purity greater than 99.0%, and the ethanol solution concentration is 95%. The fiber sheets are then dried in a drying oven at 30-180°C for 3-12 hours to allow the catalyst particles to adhere to the surface. Controlling the concentration of the catalyst solution can control the density and diameter of SiCNWs grown on the fiber sheet surface. Low catalyst concentrations tend to produce thin, straight nanowires, while high catalyst concentrations produce thick, short nanowires accompanied by the growth of thin, straight nanowires.

[0062] Step 5: Growth of nanowires and multilayer interfaces:

[0063] Specifically, a fiber sheet soaked in nickel nitrate solution is placed in a CVD furnace. After heating to 500-1500°C under an inert gas atmosphere, H2 is first introduced for 30-60 minutes as a dilution gas with a flow rate adjusted to 20-100 ml / min. Then, H2 is introduced as a carrier gas with a flow rate of 40-200 ml / min. After both channels are introduced simultaneously for 1-2 hours, the pipeline is cleaned with H2 for 10-40 minutes, and then CH4 is introduced at a flow rate of 50-200 ml / min to cover the surface of the nanowire with a layer of PyC interface. After maintaining this for 10-60 minutes, the two H2 channels are opened again, with the flow rate of H2 for dilution being 20-100 ml / min and the flow rate of H2 for carrier gas being 40-200 ml / min; thereby, a layer of SiC interface is covered on the outside of the PyC interface.

[0064] Specifically, the catalyst-loaded fiber sheet preform is placed in a horizontal quartz tube furnace (OTF-1200X) and heated to 500-1500°C under an inert gas atmosphere. H2 is then introduced to reduce the catalyst to metallic Ni in this atmosphere. CH3SiCl3 is used as the precursor, and H2 is used as the diluent and carrier gas. The MTS:H2 flow ratio is controlled at 1:6-12. Optimizing the process parameters yields uniformly distributed, finely shaped (20-100 nm in diameter, 20-30 μm in length), moderately dense, and excellently performing SiCNWs.

[0065] SiCNWs increase the hardness and elastic modulus of the micromatrix and improve the bonding strength between SiCNW and matrix (greater than 15-32GPa). The deposited PyC interface reduces the elastic modulus of the micro-region matrix but facilitates the extraction of silicon carbide nanowires in the micro-region. The synergistic effect of SiCNWs and PyC interface enhances the damage resistance and crack resistance of the composite material. Multi-level reinforced carbon fibers were prepared by chemical vapor infiltration (CVI) method, using CH3SiCl3 as the precursor raw material and H2 as the diluent gas and carrier gas. CH3SiCl3 was brought into the CVD furnace by bubbling method and repeated cycles were performed until the carbon fiber preform was fully densified.

[0066] Step 6: Extrusion casting of metal matrix composite materials:

[0067] Specifically, a metal alloy is placed on top of a fiber sheet preform. Under an argon atmosphere, the temperature is raised to 700-900°C. This temperature is maintained for a period of time to allow the metal alloy to fully melt. Subsequently, a pressure of 10-200 MPa is applied. Once the pressure ceases, the preform solidifies and hardens, resulting in the desired composite material. The squeeze casting process is performed at a pressure of approximately 85 MPa and a temperature of 850°C.

[0068] This method utilizes a continuous fiber and metal alloy extrusion casting method, followed by hot pressing under an argon atmosphere to tightly bond the fibers to the metal alloy, resulting in a continuous carbon fiber-reinforced metal matrix composite. This method significantly improves the three-point bending strength of the metal matrix composite. This method is simple, requires minimal equipment and operating environment, is energy-efficient, and offers low manufacturing costs. The resulting composite material exhibits uniform fiber distribution and controllable performance.

[0069] The silicon carbide nanowire-reinforced metal matrix composite material obtained by the present invention has a uniform fiber distribution, and the strength of the composite material after CVD interface reinforcement is greatly improved. However, the matrix between fiber bundles, within bundles, and between layers is at the micron scale, and is not reinforced and still has low stiffness. The unreinforced matrix acts as a weak area, with a portion of tens to hundreds of microns equivalent to a pure metal matrix. This portion requires a reinforcement mechanism at a finer scale to improve performance. By introducing SiC nanowires, new strengthening mechanisms are generated in the composite material at the nanoscale. These mechanisms may include the direct load-bearing effect of the nanowires, the improvement of the matrix material performance caused by nano effects (such as small size effects, surface effects, etc.), and the interaction between the nanowires and the matrix (such as interface friction, energy dissipation, etc.) that hinders crack propagation. In addition, this method is simple in process, has low requirements for equipment and operating environment, can save energy and cost, is highly feasible, and is conducive to industrialization.

[0070] The following is a more detailed description of the preparation method of the silicon carbide nanowire reinforced metal matrix composite material of the present invention using examples. The continuous carbon fiber in the following examples is 3k200g T700 strength carbon fiber imported from the United States, and the preparation method is as follows Figure 1 The process flow chart shown in the figure is shown. The morphology of the carbon fibers and the microscopic interface of the composite material are examined by scanning electron microscopy (SEM), the elemental composition of the composite material is determined by EDS, the phase composition of the composite material is determined by X-ray diffraction (XRD), the three-point bending strength of the composite material is determined by a universal testing machine, and the density of the composite material is determined by the Archimedes displacement method.

[0071] Example 1

[0072] S1. Prepare 12 4cm x 6.5cm plain-weave carbon fiber sheets. Stack them flatly in two groups of 6 sheets each. Place them in a graphite fixture with two layers, upper and lower, with a spacing of approximately 2mm between the layers. The upper carbon fiber layer weighs 2.9647g, and the lower layer weighs 2.7314g. The glue content calculated from the glue removal step gives the weight of the fibers after removing the glue: 2.9054g and 2.6768g, respectively.

[0073] S2. Place the graphite fixture and sample into a tube furnace. Use a vacuum pump to evacuate the furnace tube while introducing argon gas. Program the tube furnace to heat up to 1100°C at a rate of 10°C / min. This heating process removes the glue that bonds the carbon fibers.

[0074] S3. When the CVD furnace reaches the set temperature of 1100℃, keep it warm for 7 hours. During the first 3 hours, turn off the argon gas and introduce CH4 gas at a flow rate of 100ml / min. During the next 4 hours, turn off the CH4 gas cylinder and the access switch and introduce H2 from two pipelines that serve as dilution and carrier gas respectively. The flow rate of dilution hydrogen is adjusted to 70ml / min. The carrier hydrogen passes through the MTS tank and brings out the MTS by bubbling. The flow rate of carrier hydrogen is controlled to 150ml / min. During the entire insulation process, the air pressure in the furnace tube is maintained at 3kPa by adjusting the vacuum valve.

[0075] S4. After the holding cycle is complete, the tubular furnace begins to cool. Close the inlet and outlet valves of the CH3SiCl3 jar and allow hydrogen to flow through the pipeline for 10 minutes. Then, close the hydrogen cylinder and its inlet valves and introduce argon again until the furnace cools to room temperature. The sample is then removed. The resulting sample is free of glue and weighed to determine weight gains of 60.99% and 60.08%, respectively.

[0076] S5. Immerse the fiber sheet after the interface deposition in a nickel nitrate solution with a concentration of 0.005 mol / L, keep it in the solution for 12 hours, and then put it into a drying oven and dry it at 80° C. for 8 hours.

[0077] S6. After drying, the sample is placed in the CVD tube furnace again. After heating to 1100°C under argon atmosphere, H2 is first passed through for 30 minutes as a dilution gas with a flow rate of 100 ml / min. Then, H2 is passed through as a carrier gas with a flow rate of 20 ml / min. After the two channels are passed through at the same time for 1 hour, the pipeline is cleaned with H2 for 20 minutes, and then CH4 is passed through at a flow rate of 100 ml / min. After maintaining for 40 minutes, the two H2 channels are opened again. The flow rate of H2 for dilution is 70 ml / min, and the flow rate of H2 for carrier gas is 150 ml / min.

[0078] S7. 6061 aluminum alloy was placed on top of a carbon fiber preform with nanowires. Argon was used as a shielding gas in an oxygen-free environment. After the temperature reached 850°C, a pressure of 85 MPa was applied to squeeze the molten 6061 aluminum alloy into the carbon fiber preform, ultimately producing an aluminum-based composite reinforced with silicon carbide nanowires. The composite material, after cutting, had a height of 1.60 mm and a width of 5.86 mm, respectively.

[0079] Example 2

[0080] The preparation method of this silicon carbide nanowire-reinforced aluminum-based composite differs from that of Example 1 in that the upper carbon fiber layer weighs 2.9243 g, the lower carbon fiber layer weighs 3.0686 g, and the nickel nitrate solution concentration is 0.015 mol / L. After cutting, the composite material has a height of 1.67 mm and a width of 5.93 mm, respectively.

[0081] Example 3

[0082] The preparation method of this silicon carbide nanowire-reinforced aluminum-based composite differs from that of Example 1 in that the upper carbon fiber layer weighs 2.3189 g, the lower layer weighs 2.4159 g, and the nickel nitrate solution used for immersion has a concentration of 0.025 mol / L. After cutting, the composite material has a height of 1.40 mm and a width of 5.94 mm, respectively.

[0083] Example 4

[0084] The preparation method of this silicon carbide nanowire-reinforced aluminum-based composite differs from that of Example 1 in that the upper carbon fiber layer weighs 2.6667 g, the lower layer weighs 2.5682 g, and the nickel nitrate solution concentration is 0.035 mol / L. After cutting, the composite material has a height of 1.33 mm and a width of 5.95 mm, respectively.

[0085] Comparative Example 1

[0086] The preparation method of this silicon carbide nanowire-reinforced aluminum-based composite differs from that of Example 1 in that the upper carbon fiber layer weighs 3.2805 g, and the lower layer weighs 2.8355 g. The carbon fiber preforms are not subjected to interface deposition or immersion in a nickel nitrate solution. The height and width of the cut composite are 1.54 mm and 6.02 mm, respectively.

[0087] Comparative Example 2

[0088] The preparation method of this silicon carbide nanowire-reinforced aluminum-based composite differs from that of Example 1 in that the upper carbon fiber layer weighs 3.2805 g, while the lower layer weighs 2.8355 g; the carbon fiber preform is not immersed in a nickel nitrate solution. The height and width of the cut composite are 1.53 mm and 5.93 mm, respectively.

[0089] The weight gain and performance of the carbon fiber preforms prepared in Examples 1 to 4 of the present invention and Comparative Examples 1 to 2 were compared and tested, and the main indicators are shown in Table 1.

[0090] Table 1 Index data of carbon fiber preforms of embodiment and comparative example

[0091]

[0092] As can be seen from Table 1, the weight gain percentage of the sample is between 55% and 65% for the PyC interface deposited for 3 hours and the SiC interface deposited for 4 hours. The difference in weight gain percentage may have a certain impact on the bending properties of the composite material, which can be ignored for now. The density of the composite material obtained by the density meter is 2.417 g / cm 3 In the three-point bending test, the maximum forces withstood by Comparative Examples 1 and 2 and Examples 1, 2, 3, and 4 were 39.67N, 48.35N, 48.19N, 74.52N, 58.76N, and 41.45N, respectively. The span set in the experiment was 40mm, and the width and height of the samples in the bending test were slightly different. The strength values ​​presented in Table 1 were calculated using the bending strength formula.

[0093] The flexural strength of the composites made from carbon fiber preforms soaked at different concentrations varied. At catalyst concentrations below 0.005 mol / L, SiC nanowires were sparsely distributed on the carbon fibers, and their diameters were very small. Increasing the nickel nitrate solution concentration to 0.015 mol / L significantly increased the density of the SiC nanowires, with the nanowires clinging to each other and their diameters increasing. However, when the catalyst concentration increased to 0.035 mol / L, the SiC nanowires became dense, with large and small SiC nanowires growing in a coordinated pattern. This may affect the density of the composite, leading to a decrease in its flexural properties.

[0094] Therefore, the present invention adopts the above-mentioned preparation method for improving the mechanical properties of metal-based composite materials in micro-regions. Through chemical vapor deposition technology, PyC, SiC, BN and other multi-level interfaces are successively coated on the fiber surface. By adjusting factors such as pressure, gas, temperature, and time, the thickness of the required interface is formed on the material surface, thereby reducing the interfacial reaction during the fusion process between the fiber and the metal alloy to prevent unnecessary damage, helping to improve the overall toughness and bending resistance of the material. The results achieved by the present invention will provide assistance for the research and development and application of this new composite material. By controlling the concentration of the catalyst solution, the growth density and diameter of SiCNWs on the fiber surface can be controlled; by adjusting process parameters such as growth temperature, MTS / H2 concentration, and catalyst concentration, the controllable growth of SiCNWs on the fiber surface is achieved. The growth of nanowires on the material surface can further increase the density at the microscopic level, reduce the number of cracks and voids, and thus enhance the hardness and strength of the material in the micro-region; silicon carbide nanowire-reinforced aluminum-based composites are prepared by extrusion casting. Vertical injection can effectively reduce the formation of pores and significantly improve the density of the material. Under high pressure conditions, the alloy particles are squeezed finer and denser.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A preparation method for improving the micro-region mechanical properties of metal matrix composite materials, characterized in that: The steps include: Step 1: Selecting a fiber substrate and a metal alloy substrate: 1) Selecting continuous reinforcing fibers, cutting them into fiber braids of a certain specification, stacking them, and then placing the assembly into a dedicated positioning fixture and adjusting the fixture to secure it; 2) Select different metal alloys; Step 2: Debinding of continuous fiber sheets: The fiber sheets are placed in a CVD tube furnace, and argon gas is introduced at a flow rate of 10-500 ml / min, and the temperature is kept at 600-1200°C for 1-3 hours to remove the binder; Step 3: Depositing an interface layer. In a chemical vapor deposition process, the fiber sheet is placed in a CVD tube furnace, and the CVD tube furnace is programmed to heat the fiber sheet to 500-1500°C at a rate of 5-100°C / min. During the heating process, the furnace is first evacuated to a vacuum using a vacuum pump, and then an inert gas is introduced as a protective gas. The process of depositing the interface layer is as follows: when the reaction system reaches a predetermined process temperature, a constant temperature control program is started to maintain the thermal field of the equipment, reaction gas is introduced, and the pressure control element is adjusted to maintain the pressure in the equipment. The reaction gas deposits an interface layer on the surface of the fiber sheet. The interface layer includes one or more of PyC, SiC, and BN. Step 4: Soaking in nickel nitrate solution: First, prepare a nickel nitrate / ethanol precursor system, use nickel nitrate hexahydrate crystals to prepare solutions of different concentrations between 0.001-1.8 mol / L by precise weighing, select a fiber sheet prepared by chemical vapor deposition as a substrate, and deposit one or more layers of a composite structure of a PyC interface, a SiC interface, and a BN interface on the fiber sheet. Soak in the prepared solutions of different concentrations for 8-24 hours, take out, and dry them in a drying oven to obtain a catalyst-loaded fiber sheet; Step 5, growing nanowires and multilayer interfaces: placing the fiber sheet preform loaded with the catalyst into a CVD tube furnace, heating it to 500-1500°C under an inert gas atmosphere, introducing H2, reducing the catalyst to metallic Ni under the H2 atmosphere, using CH3SiCl3 as a precursor raw material, and H2 as a diluent gas and carrier gas to obtain a fiber sheet preform with SiCNWs; then placing the fiber sheet preform with SiCNWs into a CVD tube furnace, heating it to 500-1500°C under an inert gas atmosphere, introducing H2, and reducing the catalyst to metallic Ni under the H2 atmosphere. After heating to 500-1500°C under atmosphere, H2 is first introduced as dilution gas, followed by H2 as carrier gas. The pipeline is then cleaned with H2, and CH4 is introduced to coat the SiCNWs surface with a layer of PyC interface. After maintaining this for 10-60 minutes, both H2 channels are opened, with the H2 flow rate for dilution at 20-100 ml / min and the H2 flow rate for carrier gas at 40-200 ml / min, so that the PyC interface is coated with a layer of SiC interface. Step 6: Extrusion casting of metal-based composite materials: First, place the metal alloy on top of the fiber sheet preform. In an argon atmosphere, set the temperature to 700-900°C and keep it warm for a period of time to allow the metal alloy to fully melt. Then, apply a pressure of 10-200MPa. When the pressure ends, the preform solidifies and hardens, and the desired composite material is obtained.

2. A preparation method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step 1, the continuous reinforcing fiber is selected from a continuous high-performance fiber system, specifically including carbon fiber, alumina fiber, ceramic-based fiber, metal whisker, glass fiber, aramid fiber and biomass-derived fiber.

3. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step 1, the metal alloy includes: aluminum alloy, magnesium alloy, titanium alloy, copper alloy, and nickel alloy.

4. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step 2, the glue content of each fiber sheet is calculated to be 1-3% based on the mass difference before and after glue removal. The glue weight is removed when calculating the weight gain of subsequent fiber sheet samples.

5. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step 3, the processes of depositing PyC, SiC, and BN interfaces are as follows: Deposition of PyC interface: When the reaction system reaches the predetermined process temperature, start the constant temperature control program to maintain the thermal field of the CVD tube furnace for 1-6 hours, introduce CH4 gas at a flow rate of 50-200 ml / min, adjust the vacuum valve to maintain the furnace pressure at 0-20 kPa, and the CH4 is pyrolyzed at high temperature to deposit a layer of PyC interface on the surface of the fiber layer; Deposition of SiC interface: When the reaction system reaches the predetermined process temperature, start the constant temperature control program to maintain the thermal field of the CVD tube furnace for 1-10 hours, and introduce H2 into two pipelines for dilution and carrier gas respectively. The furnace pressure is maintained at 0-20KPa. The H2 used as dilution gas is directly introduced into the tube furnace, and the H2 used as carrier gas passes through the tank containing MTS and then enters the CVD tube furnace. The flow rate of hydrogen for dilution and carrier gas is controlled at 1:1-5. The gas passes through the CVD tube furnace and deposits a layer of SiC interface on the sample surface at high temperature. Deposition of BN interface: When the reaction system reaches the predetermined process temperature, the constant temperature control program is started to maintain the thermal field of the CVD tube furnace for 1-5 hours, and the BCl3 and NH3 dual gas supply systems are opened simultaneously. The volume flow ratio of the two precursor gases is adjusted to 1:1-5 through the mass flow controller. Under the action of carrier gas transportation, the mixed gas undergoes a vapor deposition reaction in the pyrolysis reaction zone, and finally forms a BN interface layer with controllable thickness on the surface of the fiber sheet. Its crystal morphology is positively correlated with the reaction kinetic conditions.

6. A preparation method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 5, characterized in that: In step three, the deposition of PyC and SiC interfaces is carried out at a temperature of 1000-1500°C, and the pressure in the furnace is controlled at 0-20KPa; the deposition of BN interfaces is carried out at a temperature of 500-1300°C, and the pressure in the furnace is kept in a vacuum state.

7. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step 4, the nickel nitrate is Ni(NO3)2·6H2O with a purity greater than 99.0%, and the concentration of the ethanol solution is 95%. The soaked fiber sheet is dried in a drying oven at a temperature of 30-180°C for 3-12 hours to achieve the attachment of catalyst particles to the surface.

8. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step five, during the growth of nanowires, the flow ratio of MTS and H2 in the carrier gas is controlled to be 1:6-12; in the process of covering the surface of SiCNWs with a layer of PyC interface, the time for the first introduction of H2 for dilution is 30-60 minutes, the flow rate is 20-100 ml / min, the flow rate of H2 for carrier gas is 40-200 ml / min, the time for simultaneous introduction of the two is 1-2 hours, the time for cleaning the pipeline with H2 is 10-40 minutes, and the flow rate of CH4 is 50-200 ml / min.

9. The method for improving the micro-region mechanical properties of a metal matrix composite material according to claim 1, characterized in that: In step six, the pressure is set at about 85 MPa and the temperature is set at 850° C. during the squeeze casting process.

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