A method for preparing in-situ two-phase nanoparticle reinforced aluminum matrix composite

Abstract

The present application relates to aluminum matrix composite, and relates to a preparation method of an in-situ dual-phase nanoparticle reinforced aluminum matrix composite. The present application adopts a melt direct reaction method, uses H3BO3 and K2ZrF6 as reactants, uses inert gas to add the reaction salt powder into the melt through a graphite pipeline, increases the contact area of the reaction salt and the aluminum melt, promotes the stirring of the melt, and accelerates the reaction; an electromagnetic field is applied in the melt reaction stage; the introduction of the electromagnetic field can effectively solve the clustering problem of the particles, and can improve the wettability of the particles and the matrix, and improve the yield of the particles; an ultrasonic field is applied before the melt casting; in the process of ultrasonic control, cavitation bubbles are generated in the aluminum liquid due to cavitation effect, and can emit very high instantaneous temperature and pressure; the instantaneous high temperature and high pressure can scatter the agglomerated particles, and improve the particle distribution; a pressure field is applied in the melt solidification stage, which can improve the density of the material, reduce the internal defects of the material, and improve the comprehensive performance of the material.

Description

Technical Field

[0001] This invention relates to the field of aluminum-based composite materials, and to a method for preparing an in-situ biphase nanoparticle-reinforced aluminum-based composite material. The resulting composite material exhibits high strength, high toughness, and excellent high-temperature performance. Background Technology

[0002] Particle-reinforced aluminum matrix composites are high-performance structural materials, and with the continuous development of science and technology, people have put forward higher requirements for their comprehensive performance. The in-situ method for preparing particle-reinforced aluminum matrix composites involves adding a solid powder reactive salt containing reinforcing phase particle-forming elements to molten aluminum alloy at a certain temperature, followed by stirring to ensure a complete reaction, thereby generating reinforcing particles within the aluminum melt. Compared with the external addition method, the in-situ endogenous particles are relatively small, reaching the nanometer scale, with clean and uncontaminated surfaces, good wettability with the matrix, high bonding strength, and good thermal stability. They also possess high specific strength, specific modulus, low coefficient of thermal expansion, and good wear resistance, showing great application potential in fields such as rail transportation and energy-saving vehicles.

[0003] Current research focuses primarily on single-phase nanoparticles and biphase micron-nano hybrid particles. However, some properties of single-phase particles cannot meet the growing industrial performance requirements. Biphase nanoparticle-reinforced aluminum matrix composites exhibit better physical and chemical properties than single-phase nanoparticle-reinforced aluminum matrix composites. Common reinforcing particles used in in-situ particle-reinforced aluminum matrix composites include ZrB2, Al2O3, TiB2, and SiC. Among these, ZrB2 and Al2O3 are characterized by low coefficients of thermal expansion, high melting points, high hardness, and high elastic modulus. In this invention, to achieve the composite strengthening effect and nanoscale effect of multiphase nanoparticles, both ZrB2 and Al2O3 nanoparticles are simultaneously introduced into the aluminum alloy matrix. The biphase nanoparticles, acting as effective reinforcing phases, have a tight interface with the aluminum matrix, primarily playing a role in grain boundary strengthening and Orowan strengthening, effectively improving the material's performance.

[0004] The research on in-situ biphase nanoparticle-reinforced aluminum matrix composites is still immature, mainly including the following: (1) There are few reaction systems, and the reaction temperature of the system is high, with a lot of slag, making the process difficult to control, and the morphology of the reinforcing phase synthesized by the reaction is difficult to control. (2) The nanoparticles are small in size, have a large specific surface area, are easy to agglomerate, and are unevenly distributed in the matrix. (3) The yield of in-situ synthesized biphase nanoparticles is low.

[0005] Currently, research on the preparation of in-situ biphase particle-reinforced aluminum matrix composites has made some progress. This is mainly achieved by using single external fields such as electromagnetic stirring and ultrasonic vibration to assist the melt reaction, thereby improving the properties of composites prepared by the direct melt reaction method. However, when only a magnetic field is applied, the skin effect in the molten metal is difficult to overcome, and the intensity of the magnetic field within the metal decays exponentially. Therefore, the effective depth of the magnetic field's influence on the melt is limited, and the electromagnetic stirring effect is mainly concentrated at the melt edge, with little effect in the melt center. When only an ultrasonic field is applied, cavitation bubbles mainly exist near the amplitude transformer under the sole action of the ultrasonic field, while ultrasonic vibration mainly acts around the ultrasonic generator, thus limiting the control effect of a single external field. Since the effect of a single external field is limited, researchers have proposed using multi-field regulation to improve the performance of composite materials. For example, Chinese Patent 201811286813.6, "A Method for Preparing In-situ Binary Nanoparticle Reinforced Aluminum-Based Composite Materials," uses Na₂B₄O₇ and K₂ZrF₆ as reactants, combining electromagnetic stirring and ultrasonic vibration techniques to prepare binary (ZrB₂+Al₂O₃) nanoparticle-reinforced aluminum-based composite materials. The strength of the prepared material is significantly improved, but there is a large amount of reaction slag and severe aluminum melt loss. This invention uses a direct melt reaction method, with H₃BO₃ and K₂ZrF₆ as reactants. An inert gas is used to blow the reaction salt into the aluminum melt through a graphite pipe. Based on the acoustic-magnetic coupling field, a pressure field is introduced, proposing a novel method for preparing in-situ biphase nanoparticle-reinforced aluminum-based composite materials. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing in-situ biphase nanoparticle-reinforced aluminum matrix composites. This method produces less reaction slag, which is easily removed, and the gas generated during the reaction can self-stir the melt, accelerating the reaction process. Furthermore, based on the direct melt reaction method, an inert gas is used to blow the reaction salt powder into the melt through a graphite pipe, and a three-field control technology (electromagnetic / ultrasonic / pressure field) is combined to promote particle formation, solve the particle agglomeration problem, refine the grain size, and obtain a biphase nanoparticle-reinforced aluminum matrix composite with excellent comprehensive performance.

[0007] This invention employs a direct melt reaction method, using H3BO3 and K2ZrF6 as reactants. An inert gas is used to introduce the reactive salt powder into the melt through a graphite pipe, increasing the contact area between the reactive salt and the molten aluminum, promoting melt stirring, and accelerating the reaction. An electromagnetic field is applied during the melt reaction stage; the introduction of the electromagnetic field effectively solves the particle agglomeration problem and improves the wettability between the particles and the matrix, increasing particle yield. An ultrasonic field is applied before melt casting; during ultrasonic control, cavitation bubbles generated in the molten aluminum due to the cavitation effect produce very high instantaneous temperatures and pressures. This instantaneous high temperature and high pressure can break up agglomerated particles and improve particle distribution. A pressure field is applied during the melt solidification stage, which can increase the material's density, reduce internal defects, and improve the material's overall performance.

[0008] The specific preparation method of the present invention is as follows:

[0009] (1) Dry the H3BO3 and K2ZrF6 reaction salt in an oven to remove the water of crystallization, weigh according to the required amount, grind and mix evenly.

[0010] (2) The base aluminum alloy is melted in a graphite crucible and heated to 850°C. Argon gas is used to add the reaction salt into the melt through a graphite pipe. After the reaction salt is added, an electromagnetic field is applied for regulation. The reaction is carried out for 30-40 minutes. The temperature is then lowered to 720-750°C. The slag is removed, the mixture is refined and degassed. Al-Si alloy and pure Mg are then added to regulate the alloy composition. The temperature of the composite material melt is then adjusted to 700-720°C and an ultrasonic field is applied for 1-5 minutes. The temperature is then adjusted to 650-700°C. The melt is poured into a preheated mold and an external pressure field is applied during the solidification process to obtain an in-situ dual-phase particle-reinforced aluminum matrix composite material.

[0011] (3) The obtained material is subjected to T6 heat treatment, specifically: solution treatment at 545℃ for 2 hours, quenching, aging at 180℃ for 3 hours, and then furnace cooling to room temperature.

[0012] In step (1), the reaction salt is dried at 200-300℃ for 3-4 hours. At the same time, in order to avoid the formation of the Al3Zr brittle phase during the reaction, H3BO3 should be 100% by weight.

[0013] In step (2), the electromagnetic field excitation current is 200A, the frequency is 10-15Hz, the ultrasonic power is 1.5-2.0kW, the frequency is 20-25kHz, a pressure field is applied during solidification, the applied pressure is 20-50MPa, and the mold is preheated to 400-500℃ during casting.

[0014] The composition and mass percentage of the base aluminum alloy are as follows: Si 1.0~1.5%, Cu≤0.2%, Mg 0.25~0.6%, Mn≤0.2%, Cr≤0.1%, Zn≤0.2%, Fe≤0.2%, Ti≤0.15%, with the balance being Al.

[0015] The mass ratio of the K2ZrF6 and H3BO3 reaction salt is 11-13:10-12, and the reaction equation of H3BO3 and K2ZrF6 is as follows:

[0016] 3K2ZrF6+6H3BO3+10Al=3Al2O3+3ZrB2+6KF+4AlF3+9H2O

[0017] The in-situ biphase nanoparticles are ZrB2 particles and Al2O3 particles, wherein the ZrB2 particles are square particles with a size of 70-100 nm, and the Al2O3 particles are spherical particles with a size of 60-100 nm. The total volume fraction of the particles is 1 vol.% to 5 vol.%. Attached Figure Description

[0018] To more clearly illustrate the technical solution of the present invention, the corresponding steps will be described with reference to the accompanying drawings, and corresponding examples will be given to supplement the description of the microstructure and properties of the prepared materials.

[0019] Figure 1 This is a process diagram for preparing an embodiment of the present invention.

[0020] Figure 2 XRD pattern of the prepared in-situ dual-phase particle-reinforced aluminum matrix composite.

[0021] Figure 3 Scanning images of the prepared in-situ dual-phase particle-reinforced aluminum matrix composite. (a), (c) Microstructure morphology, (b) O atom aggregation, (d) B atom aggregation, (e) Zr atom aggregation.

[0022] Figure 4 This is a comparison of the room temperature tensile properties of the matrix and the prepared in-situ biphase particle-reinforced aluminum matrix composite. Detailed Implementation

[0023] The technical solutions of the present invention are not limited to the embodiments listed below. These embodiments are only for illustrating the present invention and are not intended to limit the scope of the present invention in any way. The embodiments of the present invention are described in detail below.

[0024] Example 1:

[0025] A nanoparticle-reinforced aluminum matrix composite material with a (ZrB2+Al2O3) particle volume fraction of 1 vol.% was prepared using a melt direct reaction method. K2ZrF6 and H3BO3 reaction salts were dried in an oven at 200℃ for 3 hours to remove water of crystallization. 1160.2 g of 6016 aluminum alloy was weighed, and 27.52 g of K2ZrF6 powder and 24.01 g of H3BO3 powder were weighed according to a mass ratio of K2ZrF6:H3BO3 = 11:10. These were thoroughly ground and mixed evenly. The matrix aluminum alloy was placed in a medium-frequency induction furnace and heated to 850℃. Argon gas was used to blow the reaction salts into the melt through a graphite pipe. After the reaction salts were added, an electromagnetic field was applied with an excitation current of 200 A and an electromagnetic frequency of 10 Hz for 30 minutes. The temperature was then lowered to 720℃, slag was removed, and the mixture was refined and degassed. Finally, 46.2 g of Al-Si alloy and pure Mg were added. 5.2g of alloy composition was adjusted; then the temperature of the composite melt was adjusted to 700℃, and an ultrasonic field was applied with an ultrasonic power of 1.5kW, a frequency of 25kHz, and an ultrasonic application time of 3min; the temperature was then adjusted to 650℃, and the melt was poured into a mold preheated to 500℃, with an external pressure field of 30MPa to obtain an in-situ dual-phase particle-reinforced aluminum matrix composite. The obtained composite was subjected to a T6 heat treatment process. The solution treatment regime was to heat the material from room temperature to 545℃ within 1 hour, hold it for 2 hours, and then quench it in a water bath at 20-30℃ with a quenching transfer time of less than 10s. The aging treatment regime was to heat the material from room temperature to 180℃ within 30 minutes, hold it for 3 hours, and then cool it to room temperature in the furnace.

[0026] The room temperature tensile test results of in-situ (ZrB2+Al2O3) nanoparticle-reinforced 6016 aluminum matrix composite showed that after T6 heat treatment, the ultimate tensile strength of the composite with a particle volume fraction of 1 vol.% reached 279 MPa and the elongation reached 10.4%, which were increased by 11.6% and 28.3% respectively compared with the matrix.

[0027] Example 2:

[0028] A nanoparticle-reinforced aluminum matrix composite material with a (ZrB2+Al2O3) particle volume fraction of 3 vol.% was prepared using a melt direct reaction method. K2ZrF6 and H3BO3 reaction salts were dried in an oven at 200℃ for 3 hours to remove water of crystallization. 1251.8 g of 6016 aluminum alloy was weighed, and 90.91 g of K2ZrF6 powder and 79.33 g of H3BO3 powder were weighed according to a mass ratio of K2ZrF6:H3BO3 = 11:10. These were thoroughly ground and mixed evenly. The matrix aluminum alloy was placed in a medium-frequency induction furnace and heated to 850℃. Argon gas was used to blow the reaction salts into the melt through a graphite pipe. After the reaction salts were added, an electromagnetic field was applied with an excitation current of 200 A and an electromagnetic frequency of 12 Hz for 30 minutes. The temperature was then lowered to 720℃, slag was removed, and the mixture was refined and degassed. Then, 37.55 g of Al-Si alloy and pure Mg were added. 5.12g of alloy composition was adjusted; then the temperature of the composite melt was adjusted to 700℃, and an ultrasonic field was applied with an ultrasonic power of 1.8kW, a frequency of 22kHz, and an ultrasonic application time of 3min; the temperature was then adjusted to 650℃, and the melt was poured into a mold preheated to 500℃, with an external pressure field of 30MPa to obtain an in-situ biphase nanoparticle-reinforced aluminum matrix composite. The obtained composite was subjected to a T6 heat treatment process. The solution treatment regime was to heat the material from room temperature to 545℃ within 1 hour, hold it for 2 hours, and then quench it in a water bath at 20-30℃ with a quenching transfer time of less than 10s. The aging treatment regime was to heat the material from room temperature to 180℃ within 30 minutes, hold it for 3 hours, and then cool it to room temperature in the furnace.

[0029] The room temperature tensile test results of in-situ (ZrB2+Al2O3) nanoparticle-reinforced 6016 aluminum matrix composite showed that after T6 heat treatment, the ultimate tensile strength of the composite with a particle volume fraction of 3 vol.% reached 308 MPa and the elongation reached 13.1%, which were 23.3% and 61.7% higher than those of the matrix, respectively.

[0030] Example 3:

[0031] A nanoparticle-reinforced aluminum matrix composite material with a (ZrB2+Al2O3) particle volume fraction of 5 vol.% was prepared using a melt direct reaction method. K2ZrF6 and H3BO3 reaction salts were dried in an oven at 200℃ for 3 hours to remove water of crystallization. 1082.3 g of 6016 aluminum alloy was weighed, and 133.76 g of K2ZrF6 powder and 116.72 g of H3BO3 powder were weighed according to a mass ratio of K2ZrF6:H3BO3 = 11:10. These were thoroughly ground and mixed evenly. The matrix aluminum alloy was placed in a medium-frequency induction furnace and heated to 850℃. Argon gas was used to blow the reaction salts into the melt through a graphite pipe. After the reaction salts were added, an electromagnetic field was applied with an excitation current of 200 A and an electromagnetic frequency of 15 Hz for 30 minutes. The temperature was then lowered to 720℃, slag was removed, and the mixture was refined and degassed. Then, 21.65 g of Al-Si alloy and pure Mg were added. 3.79g of alloy composition was adjusted; then the temperature of the composite melt was adjusted to 700℃, and an ultrasonic field was applied with an ultrasonic power of 2kW, a frequency of 20kHz, and an ultrasonic application time of 3min; the temperature was then adjusted to 650℃, and the melt was poured into a mold preheated to 500℃, with an external pressure field of 30MPa to obtain an in-situ dual-phase particle-reinforced aluminum matrix composite. The obtained composite was subjected to a T6 heat treatment process. The solution treatment regime was to heat the material from room temperature to 545℃ within 1 hour, hold it for 2 hours, and then quench it in a water bath at 20-30℃ with a quenching transfer time of less than 10s. The aging treatment regime was to heat the material from room temperature to 180℃ within 30 minutes, hold it for 3 hours, and then cool it to room temperature in the furnace.

[0032] The room temperature tensile test results of in-situ (ZrB2+Al2O3) nanoparticle-reinforced 6016 aluminum matrix composite showed that after T6 heat treatment, the ultimate tensile strength of the composite with a particle volume fraction of 5 vol.% reached 290 MPa and the elongation reached 9.5%, which were 16% and 17.2% higher than those of the matrix, respectively.

[0033] The above examples demonstrate that the ultimate tensile strength and elongation of (ZrB2+Al2O3) nanoparticle-reinforced 6016 aluminum matrix composites prepared by the melt direct reaction method are significantly improved compared to the matrix alloy.

Claims

1. A method for producing an in-situ two-phase nanoparticle reinforced aluminum matrix composite material, characterized by, The specific steps are as follows: (1) the H3BO3 and K2ZrF6 reaction salt are dried in an oven at 200-300℃ for 3-4 h to remove the crystal water, and are weighed according to the required amount, ground and mixed uniformly, and the mass ratio of the K2ZrF6 and H3BO3 reaction salt is 11-13:10-12; (2) the base aluminum alloy is placed in a graphite crucible and melted, and heated to 850℃, the reaction salt is added into the melt through a graphite pipeline using argon gas, after the reaction salt is added, an electromagnetic field is applied for control, and the reaction is carried out for 30-40 min, the temperature is lowered to 720-750℃, the slag is removed, and the gas is refined, then Al-Si alloy and pure Mg are added to control the alloy composition; then the temperature of the composite melt is adjusted to 700-720℃, an ultrasonic field is applied for 1-5 min; the temperature is adjusted to 650-700℃, the melt is poured into a preheated mold, an external pressure field is applied during solidification, and the applied pressure is 20-50 MPa, to obtain an in-situ dual-phase particle reinforced aluminum matrix composite, and the base aluminum alloy composition and mass percentage are as follows: Si 1.0-1.5%, Cu ≤0.2%, Mg 0.25-0.6%, Mn ≤0.2%, Cr ≤0.1%, Zn ≤0.2%, Fe ≤0.2%, Ti ≤0.15%, and the balance is Al; (3) the obtained in-situ dual-phase particle reinforced aluminum matrix composite is subjected to T6 heat treatment.

2. A method of making in-situ dual-phase nanoparticle reinforced aluminum matrix composite according to claim 1, wherein, In step (2), the electromagnetic field excitation current is 200 A, the frequency is 10-15 Hz, the ultrasonic power is 1.5-2.0 kW, and the frequency is 20-25 kHz, and the mold is preheated to 400-500℃ during casting.

3. A method of making in-situ dual-phase nanoparticle reinforced aluminum matrix composite according to claim 1, wherein, In step (3), the specific process of T6 heat treatment is as follows: solid solution at 545℃ for 2 h, quenching, and then aging at 180℃ for 3 h, and cooling to room temperature in the furnace.

4. The method for preparing an in-situ biphase nanoparticle-reinforced aluminum-based composite material as described in claim 1, characterized in that, The in-situ dual-phase nanoparticles are ZrB2 particles and Al2O3 particles, wherein the ZrB2 particles are square particles with a size of 70-100 nm, and the Al2O3 particles are circular particles with a size of 60-100 nm, and the total volume fraction of the particles is 1 vol.%-5 vol.%.

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