Diamond particle reinforced aluminum-based composite material and preparation method thereof

Abstract

The embodiment of the invention provides a diamond particle reinforced aluminum-based composite material and a preparation method thereof. The preparation method specifically comprises the following steps: S1, adding silicon into an aluminum melt, mixing to obtain a first melt, then adding magnesium into the first melt, mixing to obtain a second melt, and carrying out spray deposition on the obtained second melt to obtain a first front blank; s2, diamond particles and high-pressure gas are mixed to form a solid-gas two-phase flow, meanwhile, the first front blank is atomized into liquid drops, the liquid drops capture the diamond particles in the solid-gas two-phase flow to form solid-liquid particles, and the solid-liquid particles are deposited and solidified to form a second front blank; and S3, the second front blank body is placed in a vacuum environment, the second front blank body is heated, then die forging is conducted, pressure maintaining is conducted in the die forging process, and the diamond particle reinforced aluminum matrix composite is obtained. According to the diamond particle reinforced aluminum-based composite material provided by the embodiment of the invention, generation of brittle phases is reduced, high thermal conductivity and low thermal expansion coefficient are achieved, and the strength and toughness are improved.

Description

Technical Field

[0001] The present invention relates to the preparation of aluminum matrix composites, and particularly to a diamond particle reinforced aluminum matrix composite and a preparation method thereof. Background Art

[0002] With the rapid development of China's industry, especially with the continuous improvement of the requirements for material properties in the fields of aerospace, automotive, electronics, etc., traditional metal materials have been difficult to meet the needs of lightweight, high strength, high wear resistance and good thermal stability. Aluminum matrix composites have gradually become ideal materials for these fields due to their excellent specific strength, specific modulus, low thermal expansion coefficient and good thermal conductivity.

[0003] In order to make aluminum matrix composites meet different requirements, reinforcing phases are usually added to aluminum matrix composites to improve their properties. Commonly used reinforcing phases include silicon carbide (SiC), boron nitride (BN), carbon fiber, carbon nanotube (CNT), etc. These reinforcing phases significantly improve the mechanical properties and thermophysical properties of the composites through their synergistic effect with the aluminum matrix. For example, diamond, due to its unique crystal structure, has extremely high intrinsic thermal conductivity (up to 2000 W / m·K at most) and extremely low thermal expansion coefficient (about 1.0×10 -6 K -1 ), and becomes an ideal reinforcing phase for aluminum matrix composites that have attracted much attention in the fields of aerospace and electronic packaging. In addition to excellent thermal conductivity, diamond also has the characteristics of high strength and low density, showing significant advantages in improving the thermal conductivity and mechanical properties of aluminum matrix composites.

[0004] However, when diamond particles are added to aluminum matrix composites, due to the insufficient interfacial bonding between the aluminum matrix and diamond particles, interfacial reactions may occur, generating brittle Al3C4 phase. The presence of this brittle phase will not only increase the interfacial thermal resistance, but also lead to a decrease in the mechanical properties of the composites. Summary of the Invention

[0005] In order to improve the defects and deficiencies existing in the prior art, the embodiments of the present invention provide a diamond particle reinforced aluminum matrix composite that can reduce the generation of brittle phases and a preparation method thereof.

[0006] The first aspect of the embodiments of the present invention provides a preparation method of a diamond particle reinforced aluminum matrix composite, including the following steps:

[0007] S1: Add silicon to the aluminum melt and mix to obtain a first melt, then add magnesium to the first melt, mix to obtain a second melt, and perform spray deposition on the obtained second melt to obtain a first preform;

[0008] S2: Mix diamond particles with high-pressure gas to form a solid-gas two-phase flow. At the same time, atomize the first preform into droplets, and enable the droplets to capture the diamond particles in the solid-gas two-phase flow to form solid-liquid particles. The solid-liquid particles deposit and solidify to form a second preform;

[0009] S3: Place the second preform in a vacuum environment, heat the second preform, and then perform die forging. Maintain the pressure during the die forging process to obtain the diamond particle-reinforced aluminum matrix composite.

[0010] In some embodiments, in step S1, add magnesium to the first melt and keep it at a second temperature, and the second temperature is 690°C to 700°C.

[0011] In some embodiments, in step S2, after heating the first preform to a third temperature, atomize the first preform into droplets, and the third temperature is 680°C to 700°C.

[0012] In some embodiments, in step S2, the solid-liquid particles deposit on a substrate plate. During the deposition process, the substrate plate descends, and the descending speed of the substrate plate is 5 mm / s to 8 mm / s.

[0013] In some embodiments, in step S2, the solid-liquid particles deposit on a substrate plate. The first preform is atomized into droplets at the nozzle, and the distance between the nozzle and the surface of the substrate plate facing the nozzle is 150 mm to 300 mm.

[0014] In some embodiments, in step S3, after placing the second preform in a vacuum environment, heat the second preform to a fourth temperature, and the fourth temperature is 500°C to 550°C.

[0015] In some embodiments, in step S3, during the die forging process, the pressure applied to the second preform is 5 MPa to 10 MPa.

[0016] In some embodiments, in step S4, the time for maintaining the pressure on the second preform is 10 min to 20 min.

[0017] The second aspect of the present invention also provides a diamond particle-reinforced aluminum matrix composite, which is prepared by using the preparation method described in any one of the above. The density of the diamond particle-reinforced aluminum matrix material is greater than or equal to 99.0%, the thermal conductivity is 370 W / m·K to 450 W / m·K, and the thermal expansion coefficient is 5.5×10 -6 ·K -1 ~13.0×10 -6 ·K -1 .

[0018] In some embodiments, the proportion of diamond particles is 1 vol% to 50 vol%.

[0019] The beneficial effects of the embodiments of the present invention at least include:

[0020] The method for preparing a diamond particle-reinforced aluminum matrix composite provided by the embodiments of the present invention includes adding silicon to an aluminum melt in step S1 and mixing to obtain a first melt, then adding magnesium and mixing to obtain a second melt. By spray-depositing the second melt, the obtained first preform has good chemical composition uniformity and metallurgical quality superiority. By performing spray forming in step S2, diamond particles are uniformly distributed in the obtained second preform, and through rapid solidification, the probability of interface reaction is effectively reduced, avoiding the diffusion reaction of aluminum atoms and carbon atoms due to high temperature to form brittle phases, thereby avoiding the increase of interface thermal resistance and the decline of mechanical properties. Through step S3, the second preform is hot forged to further eliminate the pore defects of the second preform, enhance the interfacial bonding between the aluminum matrix and diamond particles, and significantly improve the density and mechanical properties of the composite material. The diamond particle-reinforced aluminum matrix composite material obtained through the above steps has uniformly dispersed diamond reinforcement particles, uniform microstructure composition of the diamond particle-reinforced aluminum matrix composite material, high density and good interfacial bonding at the same time, significantly enhancing the flexural performance and thermophysical properties of the diamond particle-reinforced composite material, thereby endowing the diamond particle-reinforced aluminum matrix composite material with high thermal conductivity and low coefficient of thermal expansion, and at the same time improving its strength and toughness. Description of the Drawings

[0021] The following will describe in detail the specific embodiments of the present invention with reference to the drawings.

[0022] Figure 1 It is a schematic diagram of the steps of the method for preparing a diamond particle-reinforced aluminum matrix composite material in an embodiment of the present invention. Specific Embodiments

[0023] To make the above objects, features, and advantages of the present invention more obvious and understandable, the specific embodiments of the present invention will be described in detail below with reference to the drawings.

[0024] To enable those of ordinary skill in the art to better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0025] It should be noted that the terms "first", "second", etc. in the description, claims and the above-mentioned drawings of the present invention are used to distinguish similar objects and do not necessarily have to be used to describe a specific order or sequence. It should be understood that such terms can be interchanged under appropriate circumstances so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0026] It should also be noted that the division of multiple embodiments in the present invention is only for the convenience of description and should not constitute a special limitation. The features in various embodiments can be combined with each other and cross-referred to each other without contradiction.

[0027] Due to its unique crystal structure, diamond has extremely high intrinsic thermal conductivity (up to 2000 W / m·K) and extremely low coefficient of thermal expansion (about 1.0×10 -6 K -1 ), making it an ideal reinforcing material that has attracted much attention in the fields of aerospace and electronic packaging. In addition to its excellent thermal conductivity, diamond also has the characteristics of high strength and low density, showing significant advantages in improving the thermal conductivity and mechanical properties of aluminum matrix composites. However, in the process of preparing diamond-reinforced aluminum matrix composites, due to the insufficient interfacial bonding between the aluminum matrix and diamond particles, interfacial reactions may occur, generating brittle Al3C4 phase. The existence of this brittle phase will not only increase the interfacial thermal resistance but also lead to a decrease in the mechanical properties of the composite material.

[0028] Based on the above problems, the embodiments of the present invention provide a method for preparing a diamond particle-reinforced aluminum matrix composite, see Figure 1 , which includes the following steps:

[0029] S1: Add silicon to the aluminum melt and mix to obtain a first melt, then add magnesium to the first melt, mix to obtain a second melt, and perform spray deposition on the obtained second melt to obtain a first preform;

[0030] The second melt is atomized into droplets under the action of high-pressure gas by spray deposition, and the droplets are deposited to obtain the first preform. In this way, the first preform obtained by spray deposition can have better chemical composition uniformity and metallurgical quality superiority. In some specific embodiments, silicon is added by adding an aluminum-silicon master alloy to the aluminum melt. The aluminum-silicon master alloy refers to an intermediate material in which aluminum and silicon are melted and alloyed in a certain proportion. Compared with directly adding pure silicon, doping with silicon by adding an aluminum-silicon master alloy can significantly improve the process efficiency and the stability of material properties.

[0031] S2: Mix diamond particles with high-pressure gas to form a solid-gas two-phase flow. At the same time, atomize the first preform into droplets, and enable the droplets to capture diamond particles in the solid-gas two-phase flow to form solid-liquid particles. The solid-liquid particles are deposited and solidified to form the second preform;

[0032] In step S2, when the first preform is melted, its chemical composition uniformity and metallurgical quality superiority can be retained, so that the droplets formed by atomizing the first preform in step S2 have uniform chemical composition, and thus the chemical composition of the second preform is uniform; when diamond particles are mixed with high-pressure gas to form a solid-gas two-phase flow, the diamond particles are evenly distributed in the high-pressure gas, which helps the droplets to capture diamond particles and form solid-liquid particles, so that the diamond particles are evenly distributed in the droplets, and thus the diamond particles in the obtained solid-liquid particles are evenly distributed. Therefore, the second preform formed by depositing and solidifying the solid-liquid particles can achieve uniform distribution of diamond particles. Moreover, by forming droplets from the second preform, capturing diamond particles, and finally depositing to form the second preform, the temperature drops rapidly, enabling rapid solidification, which can effectively reduce the occurrence probability of interfacial reactions, avoid the diffusion reaction of aluminum atoms and carbon atoms due to high temperature to form brittle phases, and further avoid the increase of interfacial thermal resistance and the decrease of mechanical properties.

[0033] S3: Place the second preform in a vacuum environment, heat the second preform, and then perform die forging, and maintain pressure during the die forging process to obtain a diamond particle-reinforced aluminum matrix composite.

[0034] Applying a large external pressure to the second preform through the hot die forging process in step S3 can further eliminate the pore defects of the second preform, enhance the interfacial bonding between the aluminum matrix and the diamond particles, and significantly improve the density and mechanical properties of the composite material.

[0035] The preparation method of the diamond particle-reinforced aluminum matrix composite provided by the embodiment of the present invention is as follows: in step S1, silicon is added to the aluminum melt and mixed to obtain a first melt, and then magnesium is added and mixed to obtain a second melt. By spray depositing the second melt, the obtained first preform has better chemical composition uniformity and metallurgical quality superiority; in step S2, spray forming is carried out, so that diamond particles are evenly distributed in the obtained second preform, and through rapid solidification, the probability of interface reaction is effectively reduced, and the diffusion reaction of aluminum atoms and carbon atoms caused by high temperature to form brittle phases is avoided, thereby avoiding the increase of interface thermal resistance and the decline of mechanical properties; in step S3, the second preform is hot forged to further eliminate the pore defects of the second preform, enhance the interfacial bonding between the aluminum matrix and the diamond particles, and significantly improve the density and mechanical properties of the composite material. The diamond particle-reinforced aluminum matrix composite material obtained through the above steps has evenly dispersed diamond reinforcing particles, uniform microstructure composition of the diamond particle-reinforced aluminum matrix composite material, high density and good interfacial bonding at the same time, significantly enhancing the bending resistance and thermophysical properties of the diamond particle-reinforced composite material, thereby endowing the diamond particle-reinforced aluminum matrix composite material with high thermal conductivity and low coefficient of thermal expansion, and at the same time improving its strength and toughness.

[0036] In some specific embodiments, step S1 specifically includes:

[0037] Step S11: Heat aluminum to a first temperature to form an aluminum melt;

[0038] Step S12: Add an aluminum-silicon master alloy to the aluminum melt, keep it warm for a period of time and then stir to obtain a first melt;

[0039] Keeping it warm for a period of time enables the added aluminum-silicon master alloy to fully heat up, and then stirring is carried out to completely melt the aluminum-silicon master alloy into the aluminum melt, so that silicon elements are fully diffused and evenly distributed in the aluminum melt, which can avoid composition segregation. Stirring can also enhance melt convection and promote the homogenization of the microstructure of the alloy, which is beneficial to improving the performance of the subsequent composite material.

[0040] Step S13: Lower the temperature of the first melt to a second temperature, add magnesium to the first melt, then keep it warm, and stir after keeping it warm to obtain a second melt, and spray deposit the obtained second melt to obtain a first preform.

[0041] Lowering the temperature of the first melt helps to reduce the volatilization of magnesium, and thus makes the composition in the obtained composite material more accurate. Keeping it warm after adding magnesium can make magnesium fully heat up, and then stirring is carried out to fully mix magnesium with the first melt evenly.

[0042] In some embodiments, the first temperature is 720°C to 780°C. Within this temperature range, it can ensure that the aluminum is partially melted and can maintain an appropriate viscosity, which is conducive to the subsequent addition and diffusion of alloying elements (such as silicon); and it avoids the intense oxidation of the aluminum melt at higher temperatures, improving the purity of the aluminum melt. If the heating temperature is lower than 720°C, it is difficult to uniformly mix the silicon element, resulting in uneven distribution of alloy components. If the heating temperature is higher than 780°C, the viscosity of the aluminum melt decreases significantly, the oxidation rate increases, affecting the alloy purity, and at the same time increasing energy consumption and costs.

[0043] In some embodiments, in step S12, the stirring time is 10 min to 20 min to ensure that the aluminum-silicon master alloy is completely incorporated into the pure aluminum melt, so that the silicon element is fully diffused and uniformly distributed in the melt, avoiding compositional segregation. At the same time, stirring enhances melt convection, promotes the homogenization of the alloy microstructure, and improves the properties of the subsequent composite material.

[0044] In some embodiments, in step S12, the holding time is 30 min. If the holding time is too short or the stirring is insufficient, the silicon element will not be completely dispersed in the aluminum melt, resulting in non-uniformity of the alloy structure, and hard spots or defects may occur; if the holding time is too long or the stirring is excessive, it may cause severe oxidation on the melt surface, reducing the alloy purity, and at the same time increasing energy consumption.

[0045] In some embodiments, in step S12, the rotation speed during stirring is 300 rpm to 400 rpm to enable the silicon element to be uniformly distributed.

[0046] Specifically, in step S12, during the holding period, the fluidity of the melt is regularly checked. It can be visually observed whether the melt surface is smooth and uniform, or the temperature fluctuation is monitored by the temperature control system to see if it remains stable. When inclusions (such as oxide particles or irregular impurity layers) are observed on the melt surface, slag removal can be carried out to remove the inclusions in the melt.

[0047] In some specific embodiments, in step S13, the second temperature is 690°C to 700°C. In this way, the high-temperature volatilization of the magnesium element can be reduced, and the composition accuracy of the obtained material can be improved; if the temperature is lower than 690°C, the viscosity of the aluminum melt increases, and the magnesium ingot is difficult to dissolve or disperse, resulting in non-uniform distribution of the magnesium element in the composite material. If the temperature is higher than 700°C, the magnesium element is easily volatilized, resulting in loss of magnesium content, and at the same time increasing the oxidation tendency.

[0048] In some specific embodiments, in step S13, the stirring time is 10 min to 20 min. If the stirring time is insufficient, the magnesium element cannot be evenly distributed, which may affect the microstructure and mechanical properties of the composite material. If the stirring time is too long, the volatilization rate of the magnesium element will increase, and at the same time, the oxidation degree of the aluminum alloy melt will be further aggravated, reducing the comprehensive performance. A stirring time of 20 min is sufficient to evenly disperse the magnesium element and avoid composition segregation.

[0049] In some specific embodiments, in step S13, keep warm for 20 min to ensure the full diffusion and uniform distribution of the magnesium element.

[0050] In some embodiments, in step S13, the rotation speed during stirring is 200 rpm to 300 rpm to enable the magnesium element to be evenly distributed.

[0051] In some specific embodiments, in step S13, the melt temperature is detected, and it is ensured that the melt temperature difference is less than ±5 °C to ensure temperature uniformity, which helps to reduce the oxidation of magnesium.

[0052] In some specific embodiments, step S2 specifically includes:

[0053] S21: Melt the first preform to the third temperature;

[0054] S22: Mix diamond particles with high-pressure gas to form a solid-gas two-phase flow, and at the same time atomize the first preform into droplets;

[0055] S23: Enable the droplets to capture diamond particles in the solid-gas two-phase flow to form solid-liquid particles, and the solid-liquid particles deposit and solidify to form the second preform.

[0056] In some embodiments, in step S21, the third temperature is 680 °C to 700 °C. A melting temperature lower than 700 °C helps to further optimize the dispersion and interfacial bonding of the diamond reinforcement particles by reducing interfacial reactions and particle agglomeration, and since the magnesium element is volatile, it can avoid magnesium content loss and avoid increasing the oxidation tendency; while making the melting temperature higher than 680 °C helps to avoid the viscosity of the first preform after melting from being too high, which is not conducive to the subsequent formation of droplets, and at the same time helps the dispersion of elements.

[0057] Specifically, after obtaining the first preform, remove the oxide layer and defects on its surface to help obtain a composite material with better performance subsequently.

[0058] In some specific embodiments, in step S22, the diamond particles are fully mixed with high-pressure anhydrous nitrogen gas in a negative pressure generator to form a solid-liquid two-phase flow. Specifically, the pressure of the high-pressure anhydrous nitrogen gas is 0.8 MPa to 1.0 MPa.

[0059] In some embodiments, diamond particles are transported into the negative pressure generator through a hopper, which helps to supply the diamond particles evenly, and further makes the diamond particles in the solid-liquid two-phase flow disperse evenly. Specifically, the speed of the speed control motor of the hopper is 10 rpm to 50 rpm. This can ensure that the particle supply rate matches the atomization rate and ensure uniform dispersion of the particles. If it is greater than 50 rpm, it will cause an excessive supply of diamond particles, resulting in particle agglomeration and reducing the distribution uniformity. If it is less than 10 rpm, it will cause an insufficient supply of diamond particles and a low particle content in the composite material.

[0060] In some embodiments, in step S22, high-pressure anhydrous nitrogen atomizes the first preform into droplets. Specifically, the pressure of the high-pressure anhydrous nitrogen is 0.8 MPa to 1.0 MPa, so as to be able to atomize the aluminum liquid into fine droplets, increase the contact area with the diamond particles, and improve the capture rate. If the pressure is less than 0.8 MPa, the atomization effect of the aluminum liquid is poor, the droplet size is large, and the capture efficiency of the diamond particles decreases. If the pressure is greater than 1 MPa, it may cause unstable spraying, and at the same time generate too many small droplets, reducing the spraying deposition efficiency.

[0061] In other embodiments, in step S22, it may also be high-pressure anhydrous argon that atomizes the first preform.

[0062] In some embodiments, in step S23, the solid-liquid particles are deposited on the substrate plate. Specifically, the rotation speed of the substrate plate is 60 rpm to 100 rpm. In this way, it helps the solid-liquid particles to evenly cover the entire substrate surface, avoiding local over-thick or over-thin deposition areas. It promotes the formation of fine tissues and helps to improve the comprehensive performance of the composite material. If the rotation speed is too high (i.e., greater than 100 rpm), it may cause too large a centrifugal force, uneven distribution of the solid-liquid particles, resulting in problems such as inconsistent thickness or material scattering. At the same time, it may cause the solid-liquid particles to cool too quickly, forming a high internal stress and increasing the crack tendency. If the rotation speed is too low (i.e., less than 60 rpm), it is easy to cause the deposited material to concentrate on a certain part, resulting in uneven thickness and affecting the overall performance of the ingot. At the same time, it causes insufficient cooling of the droplets, coarse material structure, and reduced performance of the composite material.

[0063] In some embodiments, in step S23, the first preform is atomized into droplets at the nozzle, and the distance between the nozzle and the surface of the substrate plate facing the nozzle is 150 mm to 300 mm. In this way, the droplet flight time can be short and the cooling rate can be low, so that the droplets remain semi-solid, which helps to promote the capture of diamond particles and helps the interfacial bonding between the diamond particles and aluminum after capturing the diamond particles. And it also helps to have a small temperature gradient in the deposited layer to reduce internal stress. At the same time, after the diamond-reinforced particles are combined with the droplets, they are quickly deposited on the substrate plate and rapidly solidify, which helps to inhibit the sedimentation of diamond particles and make the distribution of diamond particles uneven, and also helps to reduce oxidation.

[0064] Specifically, the angle of the nozzle is 5° to 25°. When the angle is small (i.e., when the angle is 5° to 15°), the atomized flow ejected from the nozzle is approximately perpendicular to the substrate, resulting in a high impact kinetic energy of the droplets, which helps to enhance the droplet spreading property and reduce the porosity of the composite material. When the angle is large (i.e., when the angle is 15° to 25°), the transverse momentum component of the droplets increases, which can expand the deposition coverage area. It can be understood that the appropriate nozzle angle can be selected according to the properties of the desired composite material.

[0065] Specifically, in step S23, during the deposition process, the substrate plate descends to allow sufficient time for the solid-liquid particles to cool and solidify. Further, the descending speed of the substrate plate is 5 mm / s to 8 mm / s to ensure sufficient time for the solid-liquid particles to cool and solidify, while forming a continuous and dense material structure. It also ensures uniform heat distribution of the solid-liquid particles during the spray deposition process, forming a uniform microstructure. If the descending speed is greater than 8 mm / s, it will lead to too fast deposition, insufficient cooling of the solid-liquid particles, problems such as poor fusion and increased porosity. It may cause uneven material accumulation during the deposition process, forming local stress concentration points. If the descending speed is less than 5 mm / s, the deposition time will be too long, which may cause the surface temperature of the substrate plate to be too high, resulting in coarsening of the material structure and affecting the performance of the second preform, thereby affecting the performance of the prepared composite material.

[0066] In some embodiments, in step S3, the second preform is placed in a vacuum mold for forging.

[0067] In some embodiments, in step S3, after placing the second preform in a vacuum environment, the second preform is heated to a fourth temperature, and the fourth temperature is 500°C to 550°C to ensure plastic deformation of the second preform during die forging, while avoiding agglomeration of diamond particles and interface damage, and promoting interface bonding and densification. If the die forging temperature is lower than 500°C, the deformation resistance of the second preform increases, which may lead to forging cracks or internal defects. If the die forging temperature is higher than 550°C, the second preform may be overly softened, resulting in agglomeration of diamond particles.

[0068] In some embodiments, in step S3, during the die forging process, the pressure applied to the second preform is 5 MPa to 10 MPa. When the die forging pressure is within the range of 5 MPa to 10 MPa, internal pores can be eliminated, and the density of the obtained composite material can be improved. It promotes the contact between the aluminum matrix and diamond particles and improves the interface bonding strength. If the die forging pressure is lower than 5 MPa, the pores cannot be fully eliminated, and the material density is insufficient. If the die forging pressure is higher than 10 MPa, it may cause uneven flow of the second preform, resulting in agglomeration of diamond particles.

[0069] In some embodiments, in step S3, the holding pressure time for the second preform is 10 min to 20 min. In this way, internal stress release and sufficient densification can be ensured. If the holding pressure time is less than 10 minutes, the internal stress is not fully released, and the obtained composite material may have residual defects. If the holding pressure time is greater than 20 minutes, diamond particle agglomeration may occur, reducing the performance of the obtained composite material.

[0070] An embodiment of the present invention also provides a diamond particle-reinforced aluminum matrix composite material, which is prepared by the preparation method described in any one of the above. The density of the diamond particle-reinforced aluminum matrix material is greater than or equal to 99.0%, the thermal conductivity is 370 W / m·K to 450 W / m·K, and the thermal expansion coefficient is 5.5×10 -6 ·K -1 ~13.0×10 -6 ·K -1 。

[0071] In the diamond particle-reinforced aluminum matrix composite material, the proportion of diamond particles is 1 vol% to 50 vol%. Diamond particles can be added according to requirements. The higher the proportion of diamond particles, the higher the thermal conductivity and the lower the thermal expansion coefficient.

[0072] In some specific embodiments, the particle size of the diamond particles added in step S2 is 2 μm to 6 μm.

[0073] The following describes the preparation method provided by the embodiments of the present invention in combination with specific embodiments.

[0074] The main equipment used is the SF380 spray forming equipment and the 315T forging press.

[0075] SF380 spray forming equipment parameters:

[0076] The melt temperature range of the equipment is 680 - 850 °C, and the recommended temperature for the aluminum matrix composite material is 700 - 750 °C to ensure moderate melt viscosity and reduce the oxidation risk. The adjustable range of the spray pressure is 0.8 - 1.5 MPa, which is suitable for controlling the atomization effect and making the droplet size stable at 50 - 100 μm. The equipment is equipped with a double-ring nozzle, and the nozzle angle is adjustable (5° to 25°). Combining the substrate rotation speed (60 rpm to 100 rpm) with the sedimentation rate (5 mm / s to 8 mm / s), uniform particle capture and deposition are achieved. The equipment uses nitrogen or argon as the protective gas, and the gas flow range is 30 L / min to 50 L / min, effectively reducing oxidation and improving the atomization efficiency.

[0077] 315T forging press parameters:

[0078] The 315T forging press is suitable for die forging and densification treatment of aluminum matrix composites. The nominal pressure of the equipment is 315 tons (3150 kN), and the adjustable range is 50 - 315 tons, which is suitable for the pressurization requirements of billets with different densities. The slider stroke is 300 mm - 500 mm, and the workbench size is 1000 mm × 800 mm, which can meet the processing size requirements of common aluminum matrix composites. The die heating temperature range is 300°C to 600°C, and the recommended heating temperature for aluminum matrix composites is 500°C to 550°C. The heating rate is controlled at 10°C / min to 20°C / min, and the die temperature difference does not exceed ±5°C. The pressure holding time during forging is 10 minutes to 20 minutes, and the pressurization range is 5 MPa to 10 MPa. The equipment is also equipped with an automated hydraulic system, the hydraulic system pressure is 20 MPa to 25 MPa, and it supports real-time monitoring of the die temperature to improve operation accuracy and process stability.

[0079] Example 1

[0080] Step 1:

[0081] Start the electronic control system of the SF380 large-scale spray forming equipment, check the electronic control system, temperature control module and graphite crucible to ensure that the inner surface of the crucible is clean and pollution-free. Put 100 kg of pure aluminum ingots into the graphite crucible and set the resistance furnace temperature to 740°C. Heat until the aluminum ingots are partially melted to form an aluminum melt.

[0082] Step 2:

[0083] When the temperature in the crucible in Step 1 is stabilized at 740°C, cut 3 kg of aluminum-silicon master alloy (AlSi20) into small pieces and slowly add them to the bottom of the melt through the automatic feeding device of the SF380. Start the automatic stirring function, set the stirring time to 15 min and the rotation speed to 350 rpm. Then carry out heat preservation for 30 min and stir for 15 min to ensure that the aluminum-silicon master alloy is completely incorporated into the pure aluminum melt, so as to achieve the full diffusion and uniform distribution of silicon elements in the melt, and obtain the first melt. During heat preservation, regularly check the fluidity of the melt. It can be visually observed whether the surface of the melt is smooth and uniform, or the temperature fluctuation can be monitored by using the temperature control system to see if it remains stable. If inclusions (such as oxide particles or irregular impurity layers) appear on the surface of the melt, the on-line slag removal function can be started immediately.

[0084] Step 3:

[0085] After the first melt is completely melted in Step 2, lower the temperature of the first melt to 690 - 700 °C, and use a temperature control probe to monitor the melt temperature to ensure that the temperature difference of the melt is less than ±5 °C to guarantee temperature uniformity. Cut 1.02 kg of pure magnesium ingots into small pieces, and then slowly add them to the bottom of the melt through the automatic feeding device of SF380 to prevent sudden temperature drop and magnesium oxidation. Start the automatic stirring function again, set the stirring time to 10 min, and the rotation speed to 250 rpm. Keep warm for 20 min to ensure the full diffusion and uniform distribution of magnesium elements. After adding the slag remover, turn on the slag removal function to ensure the purity of the melt. Subsequently, adjust the spraying parameters, set the spraying acceptance distance to 150 - 300 mm, the inclined nozzle angle to 10°, the substrate rotation speed to 70 rpm, and the sedimentation rate to 5 mm / s to ensure uniform material deposition. Then turn on the spraying function of SF380 and set the spraying pressure to 1.0 MPa. Atomize the molten aluminum liquid into fine droplets under the action of high-pressure nitrogen gas, capture the reinforcing particles and deposit them on the substrate plate to obtain the first preform. After cooling the first preform obtained after spraying to room temperature, perform turning processing to remove the surface oxide layer and defects to facilitate subsequent steps.

[0086] Step 4:

[0087] Place the first preform in a graphite crucible after Step 3, heat it to 700 °C using the resistance furnace of SF380, and monitor the temperature of each area of the melt through a temperature control probe to ensure temperature uniformity. Keep warm for 10 min, and then add a slag remover to clean the inclusions on the surface of the melt to ensure the purity of the melt and provide a high-quality melt for the spraying process.

[0088] Adjust the spraying parameters again: set the spraying acceptance distance to 200 mm, the inclined nozzle angle to 10°, the substrate rotation speed to 70 rpm, and the sedimentation rate to 5 mm / s. Then turn on the spraying function of SF380 and set the spraying pressure to 0.8 MPa. At the same time, put 106.2 kg of reinforcing particles (diamond) into the hopper, start the speed-regulating motor, set the feeding speed to 20 rpm, and the particles in the hopper are driven by the speed-regulating motor and sent into the negative pressure generator through the screw. High-pressure anhydrous nitrogen gas with a pressure of 0.8 MPa is fully mixed with the particles in the negative pressure generator to form a solid-gas two-phase flow. The solid-gas two-phase flow reaches the spraying port of the double-ring slit spray gun, and the molten aluminum liquid is atomized into fine droplets by the low-temperature and high-pressure nitrogen gas. The atomized droplets fully capture the particles to form solid-liquid particles and deposit on the substrate plate with a lower temperature. After solidification, the second preform is obtained.

[0089] Step 5:

[0090] The second preform prepared by spray forming after step S4 is machined into a round ingot with a size of Φ120mm×200mm. To prevent oxidation of the round ingot during heating, it is evenly wrapped with a 0.5-mm-thick aluminum skin. The joint is sealed with aluminum foil tape, and a small round opening with a diameter of about 5 mm is left at the upper end of the aluminum skin for vacuum pumping. Ensure that there is no residual oxygen inside the aluminum skin. Subsequently, the wrapped round ingot is placed into a forging die. The die and the round ingot are heated to 500°C together, and the temperature inside the die is monitored by a thermocouple. Pressurize to 10 MPa on a 315T forging press and hold the pressure for 10 min. After the pressure holding is completed, let the round ingot cool naturally or by air cooling to room temperature, and then demold. Remove the aluminum skin on the surface by mechanical turning or peeling to ensure the surface of the round ingot is clean. Flip the round ingot 180°, load it into the forging die again, and repeat the aforementioned heating, pressurizing, and pressure holding processes to eliminate the density difference in the up and down directions and further improve the compactness and mechanical properties of the round ingot. Finally, a forged aluminum matrix composite cylinder blank is obtained, which is the diamond-reinforced particle aluminum matrix composite. The porosity of the obtained diamond-reinforced particle aluminum matrix composite is 99.2%, the flexural strength is 322 MPa, the thermal conductivity is 405 W / m·K, and the thermal expansion coefficient is 6.2×10 -6 K -1 。

[0091] Example 2

[0092] In Example 2, the pressure of high-pressure anhydrous nitrogen is 0.9 MPa. The 0.9-MPa high-pressure anhydrous nitrogen is fully mixed with the particles through a negative pressure generator to form a solid-gas two-phase flow. The remaining experimental conditions are the same as those in Example 1. The porosity of the diamond particle-reinforced aluminum matrix composite obtained in Example 2 is 99.33%, the flexural strength is 331 MPa, the thermal conductivity is 412 W / m·K, and the thermal expansion coefficient is 6.1×10 -6 K -1 。

[0093] Example 3:

[0094] In Example 3, the pressure of high-pressure anhydrous nitrogen is 1.0 MPa. The 1.0-MPa high-pressure anhydrous nitrogen is fully mixed with the particles through a negative pressure generator to form a solid-gas two-phase flow. The remaining experimental conditions are the same as those in Example 1. The porosity of the diamond particle-reinforced aluminum matrix composite obtained in Example 3 is 99.02%, the flexural strength is 302 MPa, the thermal conductivity is 372 W / m·K, and the thermal expansion coefficient is 6.5×10 -6 K -1 。

[0095] Example 4:

[0096] In Example 4, the pressure of high-pressure anhydrous nitrogen is 0.9 MPa. The 0.9 MPa high-pressure anhydrous nitrogen is fully mixed with particles through a negative pressure generator to form a solid-gas two-phase flow; after being pressurized to 10 MPa on a 315T forging press, the pressure holding time is 20 min. The remaining experimental conditions are the same as those in Example 1. The porosity of the diamond particle-reinforced aluminum matrix composite obtained in Example 4 is 99.72%, the flexural strength is 341 MPa, the thermal conductivity is 439 W / m·K, and the thermal expansion coefficient is 5.8×10 -6 K-1.

[0097] Example 5:

[0098] In Example 5, the pressure of high-pressure anhydrous nitrogen is 0.9 MPa. The 0.9 MPa high-pressure anhydrous nitrogen is fully mixed with particles through a negative pressure generator to form a solid-gas two-phase flow; after being pressurized to 5 MPa on a 315T forging press, the pressure holding time is 10 min. The remaining experimental conditions are the same as those in Example 1. The porosity of the diamond particle-reinforced aluminum matrix composite obtained in Example 5 is 99.03%, the flexural strength is 306 MPa, the thermal conductivity is 372 W / m·K, and the thermal expansion coefficient is 6.7×10 -6 K -1 .

[0099] Example 6

[0100] In Example 6, the pressure of high-pressure anhydrous nitrogen is 0.9 MPa. The 0.9 MPa high-pressure anhydrous nitrogen is fully mixed with particles through a negative pressure generator to form a solid-gas two-phase flow; after being pressurized to 5 MPa on a 315T forging press, the pressure holding time is 20 min. The porosity of the diamond particle-reinforced aluminum matrix composite obtained in Example 6 is 99.43%, the flexural strength is 339 MPa, the thermal conductivity is 418 W / m·K, and the thermal expansion coefficient is 6.0×10 -6 K -1 .

[0101] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to make equivalent embodiments with equivalent changes within the scope of the technical solution of the present invention. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A preparation method of a diamond particle-reinforced aluminum matrix composite material, characterized in that, It includes the following steps: S1: Silicon is added to the aluminum melt and mixed to obtain a first melt, then magnesium is added to the first melt, and after mixing, a second melt is obtained. The obtained second melt is subjected to spray deposition to obtain a first preform; S2: Diamond particles are mixed with high-pressure gas to form a solid-gas two-phase flow. At the same time, the first preform is atomized into droplets, and the droplets capture the diamond particles in the solid-gas two-phase flow to form solid-liquid particles. The solid-liquid particles are deposited and solidified to form a second preform; S3: The second preform is placed in a vacuum environment, the second preform is heated, and then die forging is carried out, and pressure is maintained during the die forging process to obtain the diamond particle-reinforced aluminum matrix composite material.

2. The preparation method according to claim 1, characterized in that, In the step S1, magnesium is added to the first melt and kept at a second temperature, and the second temperature is 690°C to 700°C.

3. The preparation method according to claim 1, characterized in that, In the step S2, after the first preform is heated to a third temperature, the first preform is atomized into droplets, and the third temperature is 680°C to 700°C.

4. The preparation method according to claim 1, characterized in that, In the step S2, the solid-liquid particles are deposited on the substrate plate. During the deposition process, the substrate plate descends, and the descending speed of the substrate plate is 5 mm / s to 8 mm / s.

5. The preparation method according to claim 1, wherein In the step S2, the solid-liquid particles are deposited on the substrate plate. The first preform is atomized at the nozzle to form the droplets, and the distance between the nozzle and the surface of the substrate plate facing the nozzle is 150 mm to 300 mm.

6. The preparation method according to claim 1, characterized in that, In the step S3, after the second preform is placed in a vacuum environment, the second preform is heated to a fourth temperature, and the fourth temperature is 500°C to 550°C.

7. The preparation method according to claim 1, wherein In the step S3, during the die forging process, the pressure applied to the second preform is 5 MPa to 10 MPa.

8. The preparation method according to claim 1, wherein, In the step S3, the pressure holding time for the second preform is 10 min to 20 min.

9. A diamond particle reinforced aluminum matrix composite material, characterized in that, Prepared by the preparation method according to any one of claims 1 to 8, the density of the diamond particle-reinforced aluminum matrix material is greater than or equal to 99.0%, the thermal conductivity is 370 W / m·K to 450 W / m·K, and the coefficient of thermal expansion is 5.5×10 -6 ·K -1 ~13.0×10 -6 ·K -1 .

10. The diamond particle-reinforced aluminum matrix composite material according to claim 9, wherein, The proportion of diamond particles is 1 vol% to 50 vol%.

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