A near-net-shape preparation method of high-density aluminum matrix composite by pressureless infiltration

Abstract

The present application relates to a kind of high volume fraction aluminum matrix composite pressureless infiltration near net shape preparation method, belong to metal matrix composite technical field, the present application is according to the demand of composite material service component, design and prepare the special shape ceramic preform of specific outer shape structure, and then realize the near net shape preparation of high volume fraction aluminum matrix composite by pressureless infiltration.While guaranteeing the performance of composite material, obtain aluminum matrix composite near net shape component, subsequent only needs to be a small amount of processing to surface layer can obtain the final required component.The present application method can effectively reduce the loss of raw material and processing tool, reduce the processing cost of composite material, significantly improve processing efficiency and material utilization, realize the goal of cost reduction and efficiency improvement.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal matrix composites, and particularly relates to a near-net-shape preparation method of high-volume-fraction aluminum matrix composite. BACKGROUND

[0002] High-volume-fraction aluminum matrix composites with a ceramic powder volume fraction higher than 50% have the advantages of low density, high strength, high modulus, low thermal expansion coefficient and high thermal conductivity, and are typical structural and functional integrated materials, and are widely used in the fields of aerospace, precision instruments, electronic packaging and the like.

[0003] At present, the relatively mature preparation method of the composite material parts is to obtain a high-volume-fraction aluminum matrix composite entity blank with a simple geometric shape, and then to obtain a complex structure precision service component according to the lightweight design requirement by using a variety of fine processing methods with a long cycle. Due to the outstanding application requirements of small batch and multiple varieties, it is not easy to use the standardized processing mode.

[0004] Due to the high content of hard ceramic powder, the high-volume-fraction aluminum matrix composite has great processing difficulty, and needs to select an expensive special diamond milling cutter. During the processing, the diamond milling cutter will frequently collide with the hard powder, and the cutter wears out very quickly. In order to ensure the material precision and surface quality, the milling cutter needs to be replaced in time, and the material milling rate cannot be fast. Furthermore, the milled material cannot be recycled during the processing, and the material waste is serious. The material utilization rate of some thin-walled box-shaped parts is even less than 10%. Therefore, the actual processing of the high-volume-fraction aluminum matrix composite precision component has the problems of long cycle, high cost and low material utilization rate, which greatly limits the application of the high-volume-fraction aluminum matrix composite in the fields of aerospace, precision instruments and the like, and especially hinders its popularization and application in the civil field. Therefore, it is urgent to develop a near-net-shape preparation method suitable for the high-volume-fraction aluminum matrix composite, to realize the near-net-shape preparation of the complex structure high-volume-fraction composite material, and to strive to achieve the goal of little processing of the component fitting surface and no processing of the non-fitting surface.

[0005] The main preparation methods of high-volume aluminum matrix composites include powder metallurgy and liquid infiltration. Among them, the powder metallurgy combined with hot pressing sintering or hot isostatic pressing process can prepare high-volume aluminum matrix composites with uniform distribution of reinforcing phase. Due to the high content of hard powder, actual service parts cannot be obtained by forging, extrusion, rolling and other processing methods. The size of the prepared composite blank must be larger than the size of the precision component, which brings the problem that the large-size composite blank requires higher equipment size and pressure. Overall, this process has many limitations. The pressure infiltration method also has similar limiting factors. Compared with the above methods, the pressureless infiltration process does not require external pressure. By means of capillary force between ceramic powders, the spontaneous infiltration of molten aluminum can be achieved, and high-volume aluminum matrix composites with high density and good interface bonding can be obtained. The preparation process is simple and does not require expensive equipment, which is most suitable for near-net-shape preparation of complex parts.

[0006] Obviously, as reported in the document "Cui Yan et al., Influence of SiC particle shaping on the mechanical properties of high-volume aluminum matrix composites and finite element simulation, Journal of Materials, 2019", the powder natural accumulation and pressureless infiltration method is not suitable for pressureless infiltration near-net-shape preparation. Similarly, the document "Cui Yan et al., Near-net-shape preparation of high-volume SiCp / Al composites by pressureless infiltration, 2000 New Progress in Materials Science and Engineering (Part 2) - 2000 China Materials Symposium Proceedings, 2000" reports that the hot casting method is used to prepare a preform with complex structure, and a coating is sprayed on the preform. Near-net-shape aluminum matrix composites are prepared by pressureless infiltration. In the face of the typical characteristics of small batch, multi-species and diversification of aluminum matrix composites, this method needs to use different structures of special molds to obtain the required shape structure of the preform, and the process flexibility is not enough. Patent CN202310562248.6 realizes the near-net-shape preparation of aluminum matrix composite components based on powder metallurgy and hot isostatic pressing process. This method needs to use special molds to obtain composite materials with different shapes, and has high dependence on large special equipment and molds. Therefore, it is urgent to develop a low-cost near-net-shape preparation method for high-volume aluminum matrix composites suitable for pressureless infiltration process from the perspective of engineering, to realize the near-net-shape preparation of high-volume aluminum matrix composites with flexible and variable shape structures. SUMMARY

[0007] To solve the above technical problems, the present application provides a pressureless infiltration near-net-shape preparation method for high-volume aluminum matrix composites. The present application can prepare aluminum matrix composite near-net-shape components while ensuring the mechanical properties of aluminum matrix composites, reduce raw material consumption, and reduce the preparation and processing cycle and cost of aluminum matrix composites.

[0008] To achieve the above purpose, the present application provides the following technical solutions:

[0009] The application discloses a high-density aluminum matrix composite material near-net-shape preparation method by pressureless infiltration, which comprises the following steps: a. mixing ceramic powder and a binder, and performing die forming to prepare a ceramic preform green body; b. drying the ceramic preform green body; c. fixing the ceramic preform green body after the drying treatment on a machine tool, and processing a special-shaped ceramic preform blank with a required shape structure by using a general steel milling cutter; d. performing degumming treatment on the special-shaped ceramic preform blank with the required shape structure, and performing high-temperature sintering treatment to obtain a special-shaped ceramic preform; e. placing the special-shaped ceramic preform in a graphite crucible containing aluminum alloy, placing the special-shaped ceramic preform above or below the aluminum alloy, placing the graphite crucible in an electric resistance furnace, heating to 850-1000 DEG C under nitrogen atmosphere protection, and keeping the temperature for 2-4 hours to complete the pressureless infiltration process, taking out the sample from the graphite crucible, and air cooling to obtain the high-density aluminum matrix composite material near net shape.

[0010] Further, the high-density aluminum matrix composite material near-net-shape preparation method by pressureless infiltration comprises the following steps:

[0011] a. mixing ceramic powder and a binder, and performing die forming to prepare a ceramic preform green body;

[0012] b. drying the ceramic preform green body;

[0013] c. fixing the ceramic preform green body after the drying treatment on a machine tool, and processing a special-shaped ceramic preform blank with a required shape structure by using a general steel milling cutter;

[0014] d. performing degumming treatment on the special-shaped ceramic preform blank with the required shape structure, and performing high-temperature sintering treatment to obtain a special-shaped ceramic preform;

[0015] e. placing the special-shaped ceramic preform in a graphite crucible containing aluminum alloy, placing the special-shaped ceramic preform above or below the aluminum alloy, placing the graphite crucible in an electric resistance furnace, heating to 850-1000 DEG C under nitrogen atmosphere protection, and keeping the temperature for 2-4 hours to complete the pressureless infiltration process, taking out the sample from the graphite crucible, and air cooling to obtain the high-density aluminum matrix composite material near net shape.

[0016] In the application, ceramic powder is prepared into a cubic structure ceramic preform green body by die forming, the mold used in the process is a general mold in the field (for example, a ceramic block forming mold commonly used in the field), the special-shaped ceramic preform blank with a required shape structure is processed by simple mechanical processing after drying the ceramic preform green body, the excess ceramic powder material removed in the processing process can be recycled (namely, the excess ceramic powder material removed in the processing process in step c can be returned to step a), so that the raw material consumption is reduced, meanwhile, the special-shaped ceramic preform with a specific shape structure is prepared by die forming, simple mechanical processing and high-temperature sintering, and a mold with a complex structure is not needed, so that the time and cost for preparing the mold with a complex structure are reduced.

[0017] Further, in step a, the ceramic powder is one of silicon carbide (SiC) powder, aluminum oxide (Al2O3) powder, titanium carbide (TiC) powder, titanium diboride powder (TiB2) and diamond powder, and the particle size of the ceramic powder is 20-300 μm.

[0018] The binder is polyvinyl alcohol aqueous solution with a concentration of 5-10 wt%, and the adding amount of the binder is 5-10% of the mass of the ceramic powder.

[0019] Further, in step a, the compression molding is performed by using a hydraulic press, the pressing pressure is 50-150 MPa, the loading rate is 3 MPa / s, and the pressure maintaining time is 1-4 min.

[0020] Further, in step b, the drying treatment is to place the green body of the ceramic preform in a blast drying oven, and the temperature is maintained at 80-160 ℃ for 5-10 h, and the temperature rising rate is 3-5 ℃ / min.

[0021] Further, in step c, the rotating speed of the milling cutter is 1500-2500 r / min, and the advancing rate is 1-3 mm / s.

[0022] Further, in step d, the degumming treatment is to place the ceramic preform with the required shape structure in a box-type resistance furnace, and the temperature is maintained at 400-600 ℃ for 1-3 h.

[0023] The high-temperature sintering treatment is to raise the temperature of the box-type resistance furnace to 900-1300 ℃ after the degumming treatment, and the temperature is maintained for 2-5 h.

[0024] In the above temperature rising process, the temperature rising rate is 4-8 ℃ / min.

[0025] Further, in step e, the aluminum alloy is Al-Mg-Si alloy, the mass fraction of Mg is 3-12%, and the mass fraction of Si is 9-18%.

[0026] Further, in step e, nitrogen is introduced for 30 min before temperature rising to drive away the air in the furnace, and the preparation process is performed in a nitrogen protection atmosphere.

[0027] Further, in step e, the temperature rising rate is 10-15 ℃ / min.

[0028] Further, the volume fraction of the high-volume-fraction aluminum matrix composite material prepared by the method is 50-65%, and there are many gaps between the powders, which can ensure the full penetration of the aluminum liquid.

[0029] According to the requirements of the composite service components, the special-shaped ceramic preform of specific shape structure is designed and prepared, and then the near-net shape preparation of high volume fraction aluminum matrix composite is realized through pressureless infiltration. While ensuring the performance of the composite material, the near-net shape component of the aluminum matrix composite is obtained, and only a small amount of processing is needed for the surface layer to obtain the final required component. The method can effectively reduce the loss of raw materials and processing tools, reduce the processing cost of the composite material, significantly improve the processing efficiency and material utilization, and achieve the goal of reducing cost and increasing benefit.

[0030] Compared with the prior art, the present application has the following advantages and technical effects:

[0031] 1. The special-shaped ceramic preform of specific shape structure is prepared by the method of mold pressing, simple mechanical processing and high temperature sintering. First, without designing a mold for processing a complex structure, a general mold is used to press a ceramic preform green body of simple shape. Second, the simple shape ceramic preform green body after drying treatment has a certain strength, and the powder is not easy to fall off, so it can be fixed on the machine tool, and the excess ceramic powder can be easily removed by using a general steel milling cutter, and the preform can maintain the required shape structure during the processing process. The special-shaped preform can be obtained by simple mechanical processing.

[0032] 2. The special-shaped ceramic preform is prepared by using a common mechanical processing method, and the excess ceramic powder removed during the processing process can be recycled, which can reduce the consumption of raw materials.

[0033] 3. The special-shaped preform is subjected to degreasing treatment and high temperature sintering treatment, which can ensure that it does not collapse and collapse during pressureless infiltration. At the same time, the volume fraction of the special-shaped preform is 50-65%, and there are more gaps between the powders, which can ensure that the aluminum liquid penetrates fully.

[0034] 4. The near-net shape product of high volume fraction aluminum matrix composite is prepared by using the pressureless infiltration method, the ceramic powder in the material is uniformly distributed, and the bending strength of the obtained near-net shape sample of high volume fraction aluminum matrix composite can reach more than 320MPa.

[0035] 5. According to the requirements of the composite service components, the special-shaped ceramic preform of specific shape structure is designed and prepared, and then the near-net shape preparation of high volume fraction aluminum matrix composite is realized through pressureless infiltration. While ensuring the performance of the composite material, the near-net shape component of the aluminum matrix composite is obtained, and only a small amount of processing is needed for the surface layer to obtain the final required component. The method can effectively reduce the loss of raw materials and processing tools, reduce the processing cost of the composite material, significantly improve the processing efficiency and material utilization, and achieve the goal of reducing cost and increasing benefit. BRIEF DESCRIPTION OF DRAWINGS

[0036] The accompanying drawings, which constitute a part of this specification, are included to provide a further understanding of the present application, and are incorporated in and constitute a part of this specification. The illustrations, together with their description, serve to explain the application.

[0037] Figure 1 A photograph of a green body of a simple cubic preform prepared for Example 1.

[0038] Figure 2 A photograph of a shaped SiC preform prepared for Example 1.

[0039] Figure 3 A photograph of a near net shape high volume fraction SiC / Al composite prepared for Example 1.

[0040] Figure 4 A microstructure of a near net shape high volume fraction SiC / Al composite prepared for Example 1.

[0041] Figure 5 A fracture surface of a near net shape high volume fraction SiC / Al composite prepared for Example 1.

[0042] Figure 6 A photograph of a near net shape high volume fraction SiC / Al composite prepared for Example 4.

[0043] Figure 7 Stress-strain curves for near net shape high volume fraction SiC / Al composites prepared for Examples 1, 2, and 6.

[0044] Figure 8 A photograph of a simple cubic SiC / Al composite prepared for Comparative Example 1. DETAILED DESCRIPTION

[0045] Various illustrative embodiments of the present application are now described in detail. The description made herein is not intended to limit the application beyond the realm of the appended claims. Rather, the present description is meant to provide certain aspects, features, and embodiments of the present application.

[0046] It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. In addition, where a range of values is provided, it is understood that each intervening value, to the upper and lower limit of the ranges is also specifically disclosed. Each smaller range between any stated value or intervening value in the stated range and any other stated or intervening value in that stated range is encompassed. The upper and lower limits of these smaller ranges can independently be included or excluded in the range, and are also encompassed within the application, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included.

[0047] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as those of ordinary skill in the art to which the application relates. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present application, preferred methods and materials are described. All documents mentioned herein are incorporated by reference to disclose and describe in full the methods and / or materials which are described therein. In case of conflict between the content of the specification and that of any document incorporated herein by reference, the content of the specification prevails.

[0048] Many modifications and variations of the present application described in the specification are possible without departing from the scope or spirit of the application. Other implementations of the application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. The specification and examples are illustrative only.

[0049] As used herein, the terms "comprise", "comprising", "include", "including", "have" and "having" and the like are open-ended terms that are intended to mean including, but not limited to.

[0050] The raw materials used in the embodiments of the present application are all commercially available.

[0051] In the embodiments of the present application, the bending mechanical property test of the composite material is performed according to the YB / T5349-2014 standard.

[0052] The technical solutions of the present application are further described below through examples.

[0053] Example 1

[0054] The raw materials for preparing the near-net-shape high-aluminum-based composite material in this embodiment are 150g of SiC powder with an average particle size of 80μm and 200g of aluminum alloy (Al-8Mg-12Si), and the specific steps are as follows:

[0055] a. Mix the SiC powder with a polyvinyl alcohol solution with a concentration of 9wt% thoroughly, and the addition amount of the polyvinyl alcohol solution accounts for 6% of the mass of the SiC powder. Put the mixed powder into a mold and press form using a hydraulic press, with a pressure of 110MPa, a loading rate of 3MPa / s, a pressure maintaining time of 4min, and a demolding to obtain a simple cubic-shaped preform green body (see the actual object graph of the simple cubic-shaped preform green body in Figure 1 );

[0056] b. Place the simple geometric shape preform green body prepared in step a in a blast drying oven, with a heating rate of 5℃ / min, and keep the temperature at 120℃ for 8h;

[0057] c, fixing the simple geometric shape green body after drying treatment in step b on a machine tool, and processing the green body into a special-shaped ceramic preform body with a required outer shape structure by using a common metal milling cutter, the rotating speed of the milling cutter being controlled at 2000 r / min, and the advancing speed being controlled at 2 mm / s;

[0058] d, placing the special-shaped ceramic preform body processed in step c into a box-type resistance furnace, heating at a heating rate of 5 ℃ / min to 450 ℃ and keeping for 2.5 hours for degumming treatment, and then heating at a heating rate of 6 ℃ / min to 1150 ℃ and keeping for 4.5 hours for high-temperature sintering treatment, to obtain a special-shaped SiC preform body, a physical map of the special-shaped SiC preform body being shown in Figure 2 ;

[0059] e, placing the special-shaped SiC preform body prepared in step d into a graphite crucible containing aluminum alloy, the special-shaped SiC preform body being placed above the aluminum alloy, placing the graphite crucible in a resistance furnace, and first introducing nitrogen for 30 min before heating to drive away air in the furnace, heating to 950 ℃ under the protection of a nitrogen atmosphere, and keeping for 3 hours to complete a pressureless infiltration process, taking out the sample from the crucible, and air cooling to obtain a near-net-shape high-volume-fraction SiC / Al composite material, a physical map of the near-net-shape high-volume-fraction SiC / Al composite material being shown in Figure 3 , a microstructure morphology being shown in Figure 4 , a fracture morphology being shown in Figure 5 , and a stress-strain curve being shown in Figure 7 It can be known that the near-net-shape component of the aluminum matrix composite material can be prepared while the mechanical properties of the aluminum matrix composite material are ensured.

[0060] The SiC / Al composite material special-shaped part prepared in the embodiment has a SiC volume fraction of 56%, a bending strength of 330 MPa, and an elastic modulus of 209 GPa.

[0061] Example 2

[0062] The raw materials for preparing the near-net-shape high-volume-fraction aluminum matrix composite material in the embodiment are 150 g of Al2O3 powder with an average particle size of 20 μm and 200 g of aluminum alloy (Al-8Mg-12Si), and the specific steps are as follows.

[0063] a, mixing the Al2O3 powder and a polyvinyl alcohol solution with a concentration of 10 wt% thoroughly, the polyvinyl alcohol solution being added in an amount of 5% of the mass of the Al2O3 powder, and placing the mixed powder into a mold (the mold being the same as in Example 1) to be press-formed by using a hydraulic press, the pressing intensity being 150 MPa, the loading rate being 3 MPa / s, the pressure keeping time being 5 min, and the green body being demolded to obtain a simple geometric shape green body;

[0064] b. The green body of the simple geometric shape prepared in step a is placed in a blast drying oven, and the temperature is raised at a rate of 3°C / min, and kept at 160°C for 5h;

[0065] c. The green body of the simple geometric shape prepared in step b is fixed on a machine tool, and a general steel milling cutter is used to process the desired profile structure of the ceramic preform body, the milling cutter rotating at a speed of 2500r / min, and the advancing rate is controlled at 3mm / s;

[0066] d. The profiled ceramic preform body processed in step c is placed in a box-type resistance furnace, and the temperature is raised at a rate of 8°C / min to 600°C for 1h for degumming treatment, and then the temperature is raised at a rate of 8°C / min to 1300°C for 3h for high-temperature sintering treatment to obtain a profiled Al2O3 preform;

[0067] e. The profiled Al2O3 preform prepared in step d is placed in a graphite crucible containing aluminum alloy, and the profiled Al2O3 preform is placed above the aluminum alloy. The graphite crucible is placed in a resistance furnace, and nitrogen is introduced for 30min before heating to drive out the air in the furnace. The temperature is raised to 1000°C under nitrogen atmosphere protection, and the sample is taken out of the crucible after 2h of heat preservation, and then air-cooled to obtain a near-net-shape high-volume-fraction Al2O3 / Al composite material.

[0068] The profiled Al2O3 / Al composite material prepared in this example has an Al2O3 volume fraction of 60%, a bending strength of 387MPa, and an elastic modulus of 158GPa. The stress-strain curve is shown in Figure 7 .

[0069] Example 3

[0070] The raw materials for preparing the near-net-shape high-volume-fraction aluminum-based composite material in this example are 150g of TiC powder with an average particle size of 100μm and 200g of aluminum alloy (Al-12Mg-16Si). The specific steps are as follows:

[0071] a. The TiC powder is mixed with a polyvinyl alcohol solution with a concentration of 8wt%, and the amount of polyvinyl alcohol solution added is 7% of the mass of TiC powder. The mixed powder is placed in a mold (the mold is the same as in Example 1), and is pressed using a hydraulic press at a pressure of 80MPa, a loading rate of 3MPa / s, and a pressure holding time of 1min to obtain a green body of a simple geometric shape;

[0072] b. The green body of the simple geometric shape prepared in step a is placed in a blast drying oven, and the temperature is raised at a rate of 5°C / min, and kept at 80°C for 10h;

[0073] c. The simple geometric shape green body after drying in step b is fixed on a machine tool, and a general steel milling cutter is used to process the desired profile structure of the ceramic preform blank, the milling cutter speed is controlled at 1500 r / min, and the travel rate is controlled at 1 mm / s;

[0074] d. The profiled ceramic preform blank processed in step c is placed in a box-type resistance furnace, and the temperature is raised to 550°C at a rate of 7°C / min for 1.5 hours for degumming treatment, and then the temperature is raised to 1000°C at a rate of 5°C / min for 2 hours for high-temperature sintering to obtain a profiled TiC preform;

[0075] e. The profiled TiC preform prepared by high-temperature sintering in step d is placed in a graphite crucible containing aluminum alloy, with the profiled TiC preform placed below the aluminum alloy. The graphite crucible is placed in a resistance furnace, nitrogen is introduced for 30 minutes before heating to drive out the air in the furnace, and the temperature is raised to 850°C under nitrogen atmosphere protection for 4 hours to complete the pressureless infiltration process. The sample is taken out of the crucible and air-cooled to obtain a near-net-shape high-volume-fraction TiC / Al composite material.

[0076] The TiC / Al composite material profiled part prepared in this example has a TiC volume fraction of 53%, a bending strength of 535 MPa, and an elastic modulus of 198 GPa.

[0077] Example 4

[0078] The raw materials for preparing the near-net-shape high-volume-fraction aluminum matrix composite material in this example are 100 g of SiC powder with an average particle size of 65 μm, 50 g of SiC powder with a particle size of 250 μm, and 200 g of aluminum alloy (Al-3Mg-14Si). The specific steps are as follows:

[0079] a. The SiC powder is thoroughly mixed with a polyvinyl alcohol solution with a concentration of 6 wt%, and the polyvinyl alcohol solution is added in an amount of 9% of the mass of the SiC powder, and then graphite powder is added. The mixed powder is placed in a mold (the mold is the same as in Example 1), and is pressed using a hydraulic press at a pressure of 100 MPa, a loading rate of 3 MPa / s, and a holding time of 3 min to obtain a simple geometric shape green body;

[0080] b. The simple geometric shape green body prepared in step a is placed in a forced air drying oven, and the temperature is raised at a rate of 4°C / min to 120°C and held for 8 hours;

[0081] c. The simple geometric shape green body after drying in step b is fixed on a machine tool, and a general steel milling cutter is used to process the desired profile structure of the ceramic preform blank, the milling cutter speed is controlled at 1500 r / min, and the travel rate is controlled at 1 mm / s;

[0082] d. Put the shaped ceramic preform body processed in step c into a box resistance furnace, and heat to 400°C at a heating rate of 4°C / min, and keep for 3 hours for degumming treatment, and then heat to 1200°C at a heating rate of 7°C / min, and keep for 4 hours for high-temperature sintering treatment to obtain a shaped SiC preform;

[0083] e. Put the shaped SiC preform prepared in step d into a graphite crucible containing aluminum alloy, and place the shaped SiC preform above the aluminum alloy, and place the graphite crucible in a resistance furnace, and first introduce nitrogen for 30 min before heating to drive away air in the furnace, and heat to 1000°C under nitrogen atmosphere protection, and keep for 2 hours to complete the pressureless infiltration process, and take out the sample from the crucible, and air cool to obtain a near-net-shape high-volume-fraction SiC / Al composite material.

[0084] The actual picture of the shaped SiC / Al composite material prepared in this embodiment is shown in Figure 6 , the SiC volume fraction is 63%, the bending strength of the part is 406 MPa, the elastic modulus is 230 GPa, and the stress-strain curve is shown in Figure 7 .

[0085] Example 5

[0086] The raw materials for preparing the near-net-shape high-volume-fraction aluminum matrix composite material in this embodiment are 100 g of TiB2 powder with an average particle size of 300 μm, 50 g of TiB2 powder with a particle size of 40 μm, and 200 g of aluminum alloy (Al-10Mg-9Si). The specific steps are as follows:

[0087] a. Mix the double-particle-size TiB2 powder with a polyvinyl alcohol solution with a concentration of 5 wt% thoroughly, and the addition amount of the polyvinyl alcohol solution accounts for 10% of the mass of the TiB2 powder. Put the mixed powder into a mold (the mold is the same as in Example 1), and press-form using a hydraulic press, the pressing intensity is 130 MPa, the loading rate is 3 MPa / s, the pressure maintaining time is 2 min, and the simple geometric shape preform green body is obtained after demolding;

[0088] b. Put the simple geometric shape preform green body prepared in step a into a forced air drying oven, and heat at a rate of 4°C / min, and keep at 160°C for 5 h;

[0089] c. Fix the simple geometric shape preform green body after drying treatment in step b on a machine tool, and process into a shaped ceramic preform body with a required external structure using a general steel milling cutter, the milling cutter rotating speed is controlled at 1500 r / min, and the advancing rate is controlled at 1 mm / s;

[0090] d. Put the shaped ceramic preform blank processed in step c into a box-type resistance furnace, and heat to 500°C at a heating rate of 6°C / min, and keep for 2 hours for degumming treatment, and then heat to 1100°C at a heating rate of 6°C / min, and keep for 5 hours for high-temperature sintering treatment to obtain a shaped TiB2 preform;

[0091] e. Put the shaped TiB2 preform prepared in step d into a graphite crucible containing aluminum alloy, and place the shaped TiB2 preform below the aluminum alloy, and place the graphite crucible in a resistance furnace, and pass nitrogen gas for 30 minutes before heating to drive out the air in the furnace, and heat to 850°C under nitrogen atmosphere protection, and keep for 4 hours to complete the pressureless infiltration process, and take out the sample from the crucible, and air cool to obtain a near-net-shape high-volume-fraction TiB2 / Al composite material.

[0092] The TiB2 / Al composite material shaped part prepared in this example has a TiB2 volume fraction of 65%, a bending strength of 446 MPa, and an elastic modulus of 183 GPa.

[0093] Example 6

[0094] The raw materials for preparing the near-net-shape high-volume-fraction aluminum matrix composite material in this example are 150 g of diamond powder with an average particle size of 120 μm and 200 g of aluminum alloy (Al-9Mg-18Si), and the specific steps are as follows:

[0095] a. Mix the diamond powder with a polyvinyl alcohol solution with a concentration of 7 wt% to obtain a mixture, and the amount of the polyvinyl alcohol solution added is 8% of the mass of the diamond powder. Put the mixed powder into a mold (the mold is the same as in Example 1), and press-form using a hydraulic press at a pressure of 50 MPa, a loading rate of 3 MPa / s, and a pressure maintaining time of 3 min to obtain a simple geometric shape preform green body;

[0096] b. Put the simple geometric shape preform green body prepared in step a into a forced air drying oven, and heat at a rate of 5°C / min to 80°C and keep for 10 hours;

[0097] c. Fix the simple geometric shape preform green body after drying treatment in step b on a machine tool, and use a general steel milling cutter to process into a shaped ceramic preform blank with a required external structure, and control the milling cutter speed at 2500 r / min and the travel rate at 3 mm / s;

[0098] d. Put the shaped ceramic preform blank processed in step c into a box-type resistance furnace, and heat to 400°C at a heating rate of 4°C / min, and keep for 3 hours for degumming treatment, and then heat to 900°C at a heating rate of 4°C / min, and keep for 2 hours for high-temperature sintering treatment to obtain a shaped diamond preform;

[0099] e. The high-temperature sintered irregular diamond preform prepared in step d is placed in a graphite crucible containing aluminum alloy, with the irregular diamond preform placed above the aluminum alloy. The graphite crucible is placed in an electric resistance furnace. Nitrogen is introduced for 30 minutes before heating to drive out the air in the furnace. The temperature is raised to 950°C under a nitrogen atmosphere, and the process is held for 3 hours to complete the pressureless infiltration process. The sample is removed from the crucible and air-cooled to obtain a near-net-shape high-volume-fraction diamond reinforced aluminum matrix composite material.

[0100] The near-net-shape diamond reinforced aluminum matrix composite material irregular part is prepared in this example, with a diamond volume fraction of 50%. The bending strength of the part is 324 MPa, and the elastic modulus is 196 GPa. The stress-strain curve is shown in Figure 7 .

[0101] Comparative Example 1

[0102] The same raw materials and preparation process as in Example 1 are used, but the ceramic preform is not mechanically processed (i.e., step c is not performed). The aluminum matrix composite material prepared in this comparative example is a regular cubic shape (see the actual picture of the simple cubic SiC / Al composite material prepared in Comparative Example 1 Figure 8 ), with the same height and base area as the aluminum matrix composite material in Example 1.

[0103] Comparative Example 2

[0104] The method reported in the literature "Cui Yan et al., Influence of SiC particle shaping on the mechanical properties of high-volume-fraction aluminum matrix composites and finite element simulation, Journal of Materials, 2019" is used to prepare an aluminum matrix composite material by combining powder natural accumulation and pressureless infiltration. The composite material is a regular cubic shape, with the same height and base area as the composite material in Example 1.

[0105] Obviously, if the regular cubic composite materials prepared in Comparative Examples 1 and 2 are processed into the shape in Example 1, a specially designed diamond milling cutter is needed to gradually mill away 53% of the composite material, with a material utilization rate of about 47%. If more complex composite material components are needed, the material utilization rate will be further reduced. At the same time, the milled composite material cannot be reused, causing waste of raw materials and energy.

[0106] As can be seen from the comparison, the near-net-shape aluminum matrix composite materials obtained in Examples 1-6 have the advantages of not only reducing the consumption of raw materials, but also obtaining the final required composite material irregular components only by simple surface processing, with a material utilization rate of more than 90%.

[0107] The above merely provides the preferred embodiments of the present application, and the protection scope of the present application is not limited thereto, and any changes or substitutions within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for near-net-shape production of high bulk density aluminum matrix composites by pressureless infiltration, characterized in that The method comprises the following steps: a. mixing ceramic powder and a binder, and molding to obtain a green body of a ceramic preform; b. drying the green body of the ceramic preform; c. fixing the dried green body of the ceramic preform on a machine tool, and processing into a ceramic preform with a desired shape by using a general steel milling cutter; d. degreasing the ceramic preform with the desired shape, and sintering at high temperature to obtain a ceramic preform; e. placing the ceramic preform in a graphite crucible containing an aluminum alloy, and placing the ceramic preform above or below the aluminum alloy, and placing the graphite crucible in an electric resistance furnace, and heating to 850-1000℃ under nitrogen atmosphere protection, and keeping for 2-4 hours to complete the pressureless infiltration process, and taking out the sample from the graphite crucible, and air cooling to obtain a near-net-shape high aluminum matrix composite material; The near-net-shape high aluminum matrix composite material has a volume fraction of 50-65%; In step a, the ceramic powder is one of silicon carbide powder, aluminum oxide powder, titanium carbide powder, titanium diboride powder and diamond powder, and the particle size of the ceramic powder is 20-300μm; The binder is a polyvinyl alcohol aqueous solution with a concentration of 5-10wt%, and the additive amount of the binder is 5-10% of the mass of the ceramic powder; In step a, the molding is hydraulic pressing with a pressure of 50-150MPa, a loading rate of 3MPa / s and a pressure maintaining time of 1-4min; In step b, the drying treatment is placing the green body of the ceramic preform in a blast drying oven, keeping at 80-160℃ for 5-10h, and the heating rate is 3-5℃ / min.

2. The high volume fraction aluminum matrix composite near net shape production method by pressureless infiltration according to claim 1, wherein In step c, the milling cutter rotates at 1500-2500r / min, and the advancing rate is 1-3mm / s.

3. The high volume fraction aluminum matrix composite near net shape production method by pressureless infiltration according to claim 1, wherein In step d, the degreasing treatment is placing the ceramic preform with the desired shape in a box-type electric resistance furnace, and keeping at 400-600℃ for 1-3h; The high-temperature sintering treatment is heating the box-type electric resistance furnace to 900-1300℃ for 2-5h after the degreasing treatment, and the heating rate is 4-8℃ / min.

4. The high volume fraction aluminum matrix composite near net shape production method by pressureless infiltration according to claim 1, wherein In step e, the aluminum alloy is an Al-Mg-Si alloy, and the mass fraction of Mg is 3-12%, and the mass fraction of Si is 9-18%.

5. The high volume fraction aluminum matrix composite near net shape production method by pressureless infiltration according to claim 1, wherein In step e, nitrogen is introduced for 30min before heating, and the preparation process is carried out in a nitrogen atmosphere.

6. The high volume fraction aluminum matrix composite near net shape production method by pressureless infiltration according to claim 5, wherein In step e, the heating rate is 10-15℃ / min.

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