Method for preparing TiB2 particle reinforced aluminum-based composite material through low-temperature sintering

Abstract

The invention discloses a method for preparing a TiB2 particle reinforced aluminum-based composite material through low-temperature sintering, and relates to the technical field of preparation of high-strength and high-toughness aluminum-based composite materials. A low-temperature sintering mode is adopted, titanium powder and boron powder are used as sources of TiB2, and energy released by reaction of titanium and polytetrafluoroethylene is utilized in the smelting process to initiate a titanium-boron solid-phase reaction, so that fine TiB2 particles generated at low temperature are uniformly distributed in an alloy matrix, the dispersion enhancement effect is achieved, and the obdurability of the alloy material is improved. Compared with direct addition of the TiB2 powder, the preparation method has the advantages that the titanium-boron solid-phase reaction is initiated through energy released by reaction of titanium and polytetrafluoroethylene, the aluminum melt is in an overheating state, the fluidity of the aluminum melt is improved, the prepared TiB2 particles can be more uniformly dispersed and distributed in an alloy matrix, and the mechanical property of the aluminum alloy material is improved. The material can be widely applied to the fields of light-weight and high-toughness materials for new energy automobiles, aerospace and the like.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of high-strength and high-toughness aluminum-based composite materials, and in particular to a method for preparing TiB2 particle-reinforced aluminum-based composite materials by low-temperature sintering. Background Art

[0002] Aluminum-based composite materials are widely used in aerospace, automotive, and electronics fields due to their excellent mechanical properties, lightweight, and good corrosion resistance. As various fields develop towards lightweight, modern, and high-speed development, especially the development requirement of "replacing steel with aluminum", the demand for high-performance, lightweight, and high-strength aluminum alloys is becoming increasingly strong. However, the performance of existing single aluminum alloys can no longer fully meet application requirements. For example, the tensile strength of 7075 aluminum alloy at 300°C is only 10% of its room temperature strength, which has become a key shortcoming restricting the structural design and safe service under high-power and high-temperature service conditions. The development of high-performance aluminum alloy materials is urgently needed.

[0003] To further enhance the performance of aluminum-based composites, researchers have discovered that adding reinforcing phases is a common approach. TiB2, a reinforcing phase with high hardness, a high melting point, and excellent thermal conductivity, has garnered widespread attention in recent years. TiB2 particles possess excellent wear resistance and oxidation resistance, and their uniform distribution within the aluminum matrix can significantly improve the material's strength and hardness. Furthermore, the addition of TiB2 particles can improve the composite's high-temperature performance and deformation resistance, making TiB2 / aluminum-based composites more widely applicable under high-temperature or high-load conditions.

[0004] Powder metallurgy has gained attention for its ability to effectively control particle distribution and composition, improving material density, and is one of the primary methods for preparing high-performance aluminum-based composites. Although the reinforcing phase exhibits good wettability and interfacial compatibility with aluminum and its alloys, subsequent high-temperature sintering can easily lead to grain coarsening of the aluminum matrix and interfacial reactions (formation of the Al3Ti brittle phase), reducing the material's toughness. Furthermore, there are reports of directly adding TiB2 powder to the aluminum alloy matrix to prepare TiB2-reinforced aluminum alloy composites. However, during the preparation process, the density of TiB2 powder is greater than that of the aluminum alloy melt, and directly adding TiB2 powder will precipitate beneath the bulk, resulting in uneven distribution of the dispersed phase. In contrast, introducing TiB2 particles through in-situ reaction offers advantages such as improved dispersibility and high interfacial bonding. While widely used, these methods often require high-temperature sintering. This high-temperature treatment can lead to thermal damage to the aluminum matrix, interparticle reactions, and embrittlement, thus compromising the overall performance of the composite. Therefore, research and development of low-temperature sintering methods has become an important direction for improving the mechanical properties of TiB2 / aluminum-based composites and minimizing thermal damage during sintering. Summary of the Invention

[0005] To address the above problems, the present invention proposes a method for preparing TiB2 particle-reinforced aluminum-based composite materials. By adopting a low-temperature sintering method, fine TiB2 particles are generated at low temperature and evenly distributed in the alloy matrix, thereby greatly improving the mechanical properties of the material.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is:

[0007] A method for preparing TiB2 particle-reinforced aluminum-based composite materials by low-temperature sintering uses titanium powder and boron powder as sources of TiB2. During the aluminum alloy smelting process, the energy released by the reaction between titanium and polytetrafluoroethylene (PTFE) is used to trigger a titanium-boron solid-phase reaction, generating fine TiB2 particles uniformly distributed in the alloy matrix at low temperature, thereby achieving a dispersion enhancement effect and improving the strength and toughness of the aluminum alloy material.

[0008] As a preferred technical solution of the present invention, the preparation method specifically comprises the following steps:

[0009] Step 1: Dry the aluminum alloy sample and weigh titanium powder, boron powder and PTFE in a mass ratio of 2-2.5:1:0.1-0.5. The amount of the three added is 1-5% of the mass of the aluminum alloy;

[0010] Step 2: Heat the crucible to 400-500°C, preheat for 1-3 hours, then raise the temperature to 580-600°C, add the dry aluminum alloy and melt it;

[0011] Step 3: Add titanium powder and boron powder wrapped in aluminum foil to the melt, stir at 580°C for 10 minutes, and let it stand for 15-20 minutes.

[0012] Step 4: Press the PTFE wrapped in aluminum foil into the melt at 580°C, stir for 3-5 minutes, and let it stand until the reaction is complete;

[0013] Step 5: Add hexachloroethane powder, degas, stir, and let it stand and keep warm until the hexachloroethane reacts completely, then skim off the residue;

[0014] Step 6: Add the deslagging agent, remove the slag, stir, and let it stand and keep warm until the deslagging agent reacts completely, then remove the slag again to obtain the casting liquid;

[0015] Step 7: Pour the casting liquid into the mold for molding.

[0016] As a further preferred technical solution of the present invention, in the preparation method: the purity of the titanium powder used is greater than 99.5%, and the particle size is 45-50 μm; the purity of the amorphous boron powder used is greater than 99%, and the particle size is 0.5-2 μm; the purity of the PTFE powder used is greater than 99.5%, and the particle size is 0.5-2 μm; the aluminum alloy used is A356 aluminum alloy, and its components are: Si 6.5-7.5%, Mg 0.3%-0.4%, Ti 0.08%-0.2%, Sr 0-0.0015%, and Al balance.

[0017] As a further preferred technical solution of the present invention, in the preparation method, sodium silicate nonahydrate: zinc oxide are mixed in a weight ratio of 1:3-5, and then water 2.5 times the mass of the powder is added to make it into a water emulsion to prepare a release agent, which is evenly brushed on the crucible and mold surface.

[0018] The TiB2 particle reinforced aluminum-based composite material prepared by the present invention, wherein the mass fraction of the TiB2 particles in the aluminum-based composite material is preferably 0.5-2.0%, can significantly improve the mechanical properties of the aluminum alloy material.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] First, compared with the process of preparing TiB2 reinforced aluminum alloy composite materials by adding KBF4 and TiO2 composite salts, which requires heating to 1000-1050°C, the present invention adopts a low-temperature sintering method to prepare TiB2 particle reinforced aluminum-based composite materials, reducing thermal damage during the sintering process.

[0021] Secondly, compared to directly adding TiB2 powder, this method uses low-temperature sintering. The reaction between titanium powder and polytetrafluoroethylene releases a tremendous amount of heat, superheating the aluminum melt. This increases the fluidity of the melt, resulting in smaller TiB2 particles that are more evenly distributed in the alloy matrix, improving the mechanical properties of the aluminum alloy. This makes it suitable for a wide range of applications in new energy vehicles, aerospace, and other fields requiring lightweight, high-toughness materials.

[0022] Third, the present invention can improve the mechanical properties of A356 aluminum alloy while reducing the preparation temperature and simplifying the process flow of preparing TiB2 particle-reinforced aluminum-based composite materials. It can be obtained after low-temperature melting and mold casting, which can greatly improve production efficiency and increase production capacity, and is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 The following are comparison diagrams of engineering stress and strain of aluminum-based composite materials prepared in various embodiments.

[0024] Figure 2This is the SEM image of the tensile fracture of the TiB2 particle reinforced aluminum matrix composite material prepared in Example 1. DETAILED DESCRIPTION

[0025] The preferred embodiments and comparative examples of the present invention are described in detail below so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more precise definition of the protection scope of the present invention.

[0026] Example 1

[0027] This embodiment proposes a method for preparing TiB2 particle-reinforced aluminum-based composite materials by low-temperature sintering. A vacuum melting process is used to melt A356 aluminum alloy, and then titanium powder, boron powder and PTFE are added. The mixture is stirred and melted, degassed and slag-removed, and finally molded to prepare a TiB2 particle-reinforced aluminum-based composite material with a mass fraction of 1.5%.

[0028] The raw materials used are: 3.1g titanium powder (purity greater than 99.5%, particle size 45-50μm), 1.4g amorphous boron powder (purity greater than 99%, particle size 1μm), 0.5g PTFE powder (purity greater than 99.5%, particle size 1μm), 300g A356 aluminum alloy (including Si 6.5-7.5%, Mg 0.3%-0.4%, Ti 0.08%-0.2%, Sr 0-0.0015%, and Al balance). A356 aluminum alloy was purchased from Hebei Xinlizhong Nonferrous Metals Group Co., Ltd., and titanium powder, boron powder, and PTFE were purchased from DuPont of the United States.

[0029] The preparation steps are as follows:

[0030] Step 1: Prepare the release agent by mixing sodium silicate nonahydrate and zinc oxide in a weight ratio of 1:4. Then add 2.5 times the weight of the powder in water to make it into a water emulsion. Evenly brush it on the surface of the crucible and mold.

[0031] Step 2: Dry the A356 aluminum alloy sample at 250°C.

[0032] Step 3: Heat the crucible to 450°C, preheat for 1.5 hours, then raise the temperature to 580°C, place the alloy sample in it and make it molten.

[0033] Step 3: Add titanium powder and boron powder (wrapped in aluminum foil) to the melt respectively, maintain the furnace temperature at 580°C and stir for 10 minutes, and let it stand and keep warm for 15 minutes.

[0034] Step 4: At a furnace temperature of 580°C, press the polytetrafluoroethylene wrapped in aluminum foil into the melt, stir for 3 minutes, and let it stand until the reaction is complete.

[0035] Step 5: Add 2g of hexachloroethane powder, degas, stir, and let it stand for 15 minutes until the hexachloroethane reacts completely, then skim off the residue.

[0036] Step 6: Add 2g of slag remover, stir, and let it stand for 15 minutes until the slag remover reacts completely, then remove the slag again to obtain the casting liquid.

[0037] Step 7: Pour the casting liquid into a mold and let it stand for 5 hours to finally prepare an aluminum-based composite material with a mass of 200 g. The mass fraction of TiB2 particles in the aluminum-based composite material is 1.5%.

[0038] Example 2

[0039] This example compares the performance of TiB2 powder-reinforced aluminum-based composite materials. The preparation steps are as follows:

[0040] Step 1: Prepare the release agent by mixing sodium silicate nonahydrate and zinc oxide in a weight ratio of 1:4. Then add 2.5 times the weight of the powder in water to make it into a water emulsion. Evenly brush it on the surface of the crucible and mold.

[0041] Step 2: Dry the A356 aluminum alloy sample at 250°C.

[0042] Step 3: Heat the crucible to 450°C, preheat for 1.5 hours, then raise the temperature to 750°C, put in 200g of A356 aluminum alloy sample and make it into a molten state.

[0043] Step 4: Weigh 4.5 g of TiB2 powder (Aladdin Reagent Shanghai Co., Ltd.) and add it to the melt.

[0044] Step 5: After the TiB2 powder is mixed, stir again and skim off the residue.

[0045] Step 6: Add 2g of hexachloroethane powder, degas, stir, and let it stand for 15 minutes until the hexachloroethane reacts completely, then skim off the residue.

[0046] Step 7: Add 2g of slag remover, stir, and let it stand for 15 minutes until the slag remover reacts completely, then remove the slag again to obtain the casting liquid.

[0047] Step 8: placing the casting liquid into a mold for molding, and letting it stand for 5 hours to finally prepare an aluminum-based composite material, wherein the mass fraction of TiB2 in the aluminum-based composite material is 1.5%.

[0048] Example 3

[0049] This experiment serves as a comparative example. Compared with the aluminum alloy with in-situ generation of TiB2, the aluminum alloy with in-situ generation of TiB2 was generated in a crucible resistance furnace using 99.8% industrial pure Al, 99.5% purity titanium powder and boron powder.

[0050] Step 1: Dry the weighed industrial pure aluminum at 250°C, then add it into a graphite crucible resistance furnace, heat and melt it, and raise the temperature to 800°C.

[0051] Step 2: Weigh titanium powder and boron powder according to a mass fraction ratio of Ti / B of approximately 2.2:1, and calculate the absorption rate as 90%.

[0052] Step 3: Immerse the powder wrapped in aluminum foil in aluminum melt, stir, and maintain the temperature at 900°C for 30 minutes. The amount of powder added is calculated based on the TiB2 content of 1.5%.

[0053] Step 4: After degassing and removing slag from the casting liquid, the TiB2 in-situ reinforced aluminum-based composite material is obtained by casting.

[0054] Example 4

[0055] This experiment serves as a comparative example to compare the in-situ generation of TiB2 in aluminum alloy. 99.8% industrial pure Al, 98% pure KBF4 and TiO2 composite salt, and 99% pure industrial cryolite (Na3AlF6) powder were used to in-situ generate TiB2 in a crucible resistance furnace.

[0056] The specific method for preparing the in-situ generated TiB2 aluminum alloy in this example is as follows:

[0057] The chemical equation for the reaction between mixed salt and aluminum melt is:

[0058] 3TiO2+4A1=3Ti+2A12O3(1)

[0059] Ti+3Al=TiAl3(2)

[0060] 2KBF4+3Al=2KAlF4+AlB2(3)

[0061] The reaction of the generated Al3Ti and AlB2 in the melt is:

[0062] Al3Ti+AlB2=TiB2+4Al(4)

[0063] Step 1: Add weighed industrial pure aluminum into a graphite crucible resistance furnace, heat and melt, then quickly add cryolite Na3A1F6 powder covering agent, heat to 1000℃ under the covering agent, and weigh KBF4 and TiO2 composite salt according to the Ti / B atomic ratio of 1 / 2.

[0064] Step 2: After mixing evenly, place in an electric thermostat and dry at 250°C for 2 hours to remove moisture from the salts.

[0065] Step 3: Add the dried, aluminum foil-wrapped mixed salt mixture, stir rapidly and allow to stand until a vigorous reaction occurs within the melt. Maintain the temperature at 1000°C for 20 minutes. The amount of mixed salt added is calculated to produce a TiB2 content of 1.5%.

[0066] Step 4: After the melt temperature is lowered to 760°C, degas and remove slag.

[0067] Step 5: Casting to obtain TiB2 in-situ reinforced aluminum matrix composite material.

[0068] from Figure 1 It can be seen that the mechanical properties of the TiB2 particle reinforced aluminum-based composite material prepared by low-temperature casting are significantly improved compared with the sample with direct addition of TiB2 powder (Example 2) and the sample with high-temperature addition of Ti and B powder (Example 3). The elongation of the aluminum alloy material prepared by low-temperature casting is greatly improved, and the tensile strength is also improved to a certain extent compared with the sample prepared by the composite salt method (Example 4).

[0069] from Figure 2 It can be seen that the distribution of B element corresponds to that of Ti element. The TiB2 particles in the TiB2 particle reinforced aluminum matrix composite material prepared by low temperature casting are distributed more evenly in the aluminum matrix without obvious agglomeration, which plays a role of dispersion strengthening.

[0070] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A method for preparing TiB2 particle reinforced aluminum matrix composite material by low temperature sintering, characterized in that: Titanium powder and boron powder are used as the source of TiB2. During the aluminum alloy smelting process, the energy released by the reaction between titanium and polytetrafluoroethylene (PTFE) is used to trigger the titanium-boron solid phase reaction, generating fine TiB2 particles at low temperature and evenly distributed in the alloy matrix, which plays a role of dispersion enhancement and improves the strength and toughness of the aluminum alloy material.

2. The method according to claim 1, wherein The specific steps include: Step 1: Dry the aluminum alloy sample and weigh titanium powder, boron powder and PTFE in a mass ratio of 2-2.5:1:0.1-0.

5. The amount of the three added is 1-5% of the mass of the aluminum alloy; Step 2: Heat the crucible to 400-500°C, preheat for 1-3 hours, then raise the temperature to 580-600°C, add the dry aluminum alloy and melt it; Step 3: Add titanium powder and boron powder wrapped in aluminum foil to the melt, stir at 580°C for 10 minutes, and let it stand for 15-20 minutes. Step 4: Press the PTFE wrapped in aluminum foil into the melt at 580°C, stir for 3-5 minutes, and let it stand until the reaction is complete; Step 5: Add hexachloroethane powder, degas, stir, and let it stand and keep warm until the hexachloroethane reacts completely, then skim off the residue; Step 6: Add the deslagging agent, remove the slag, stir, and let it stand and keep warm until the deslagging agent reacts completely, then remove the slag again to obtain the casting liquid; Step 7: Pour the casting liquid into the mold for molding.

3. The method according to claim 2, wherein The purity of the titanium powder used is greater than 99.5%, and the particle size is 45-50 μm. The purity of the amorphous boron powder used is greater than 99%, and the particle size is 0.5-2 μm. The purity of the PTFE powder used is greater than 99.5%, and the particle size is 0.5-2 μm. The aluminum alloy used is A356 aluminum alloy, and its components are: Si 6.5-7.5%, Mg 0.3%-0.4%, Ti 0.08%-0.2%, Sr 0-0.0015%, and Al balance.

4. The method according to claim 2, wherein Mix sodium silicate nonahydrate and zinc oxide in a weight ratio of 1:3-5, then add 2.5 times the weight of the powder into water to make it into a water emulsion to prepare a release agent, and evenly brush it on the crucible and mold surface.

5. The TiB2 particle reinforced aluminum matrix composite material prepared by the method according to any one of claims 1 to 4, characterized in that: The mass fraction of TiB2 particles in the aluminum-based composite material is 0.5-2.0%.

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