阅读说明：本技术 一种低温制备原位纳米颗粒增强铝基复合材料的方法 (Method for preparing in-situ nanoparticle reinforced aluminum matrix composite at low temperature ) 是由 陈飞 王彬彬 赵玉涛 张津荣 于 2020-11-20 设计创作，主要内容包括：本发明涉及铝基复合材料领域,特指一种低温制备原位纳米颗粒增强铝基复合材料的方法。本发明借助低温条件下660℃-670℃的放热化学反应实现复合材料的原位合成,解决了传统原位反应温度高,能耗高,基体合金元素烧损的难题；通过在原位反应最集中的位置,即铝熔体表面,施加高速机械搅拌以抑制颗粒团聚的形成并改善颗粒分散性和尺寸,可原位合成纳米级ZrB-2颗粒增强铝基复合材料,从而显著提高基体的力学性能。(The invention relates to the field of aluminum-based composite materials, in particular to a method for preparing an in-situ nanoparticle reinforced aluminum-based composite material at a low temperature. The invention realizes the in-situ synthesis of the composite material by means of the exothermic chemical reaction at 660-670 ℃ under the low temperature condition, and solves the problems of high temperature, high energy consumption and burning loss of matrix alloy elements in the traditional in-situ reaction; nanoscale ZrB can be synthesized in situ by applying high speed mechanical agitation to inhibit particle agglomeration and improve particle dispersion and size at the location where the in situ reaction is most concentrated, i.e., the surface of the aluminum melt 2 Particle reinforced aluminium base composite materialThereby obviously improving the mechanical property of the matrix.)

1. A method for preparing an in-situ nanoparticle reinforced aluminum matrix composite at low temperature is characterized by comprising the following specific steps:

1) two industrial-grade fluoride salts KBF₄And K₂ZrF₆Drying to remove the absorbed water vapor and crystal water, and smelting the aluminum alloy matrix in a resistance furnace or an induction furnace at low temperature;

2) according to the target composite materialZrB₂Determining and weighing two kinds of fluorine salt according to the particle content, and then uniformly mixing the fluorine salt;

3) when the temperature of the aluminum melt reaches 660-670 ℃, removing surface slag, starting to apply high-speed mechanical stirring on the upper surface of the aluminum melt to form surface layer vortex, and immediately mixing KBF₄And K₂ZrF₆Adding the mixed salt into the vortex on the surface layer of the aluminum melt;

4) and after the heat preservation and the stirring are finished, removing a liquid reaction byproduct on the upper layer of the aluminum melt, and heating, refining and casting to obtain the in-situ nano particle reinforced aluminum matrix composite.

2. The method for preparing in-situ nanoparticle reinforced aluminum matrix composite material at low temperature according to claim 1, wherein in the step (1), KBF is performed₄And K₂ZrF₆The drying temperature is 200 +/-10 ℃, the drying time is more than 2 hours, and the drying equipment is an air blast drying box; the low-temperature smelting temperature of the aluminum alloy matrix is controlled to be near the melting point of pure aluminum, namely 660-670 ℃.

3. The method for preparing in-situ nano-particle reinforced aluminum-based composite material at low temperature according to claim 1, wherein in the step (2), ZrB in the target composite material₂The mass fraction of the particles of the reinforcement is between 3 and 7 percent, and KBF₄And K₂ZrF₆According to the reaction scheme 6KBF₄+3K₂ZrF₆+10Al＝3ZrB₂+K₃AlF₆+9KAlF determined that the molar ratio of B to Zr was maintained at 2:1 and the fluoride salt was mixed by hand or using a blender.

4. The method for preparing the in-situ nanoparticle reinforced aluminum matrix composite at low temperature as claimed in claim 1, wherein in the step (3), the stirring intensity is 1000 rpm, and the stirring time is 15 minutes.

5. The method for preparing in-situ nano-particle reinforced aluminum-based composite material at low temperature according to claim 1Characterized in that in the step (3), the mixed salt is added into the vortex on the surface of the melt through the charging pipe, the temperature of the mixed salt is preheated to 150-₂And (3) granules.

6. The method for preparing the in-situ nanoparticle reinforced aluminum-based composite material at low temperature as claimed in claim 1, wherein in the step (4), the by-product on the surface of the aluminum melt is removed immediately after the stirring is finished, the melt is refined after the temperature is raised to 720 ℃, and the metal mold casting is carried out, so as to obtain the in-situ nanoparticle reinforced aluminum-based composite material.

Technical Field

The invention relates to the field of aluminum-based composite materials, in particular to a method for synthesizing nano ZrB in situ at low temperature by virtue of an exothermic reaction between mixed salt and low-temperature aluminum melt and a high-speed mechanical stirring technology₂The composite material synthesized by the method has excellent properties of high strength, high hardness, high plasticity and the like.

Background

As a high-performance structural material, the aluminum-based composite material has high strength, low density, high wear resistance, low thermal expansion, excellent processing formability, good welding performance, higher fracture toughness, corrosion resistance and the like, so that the aluminum-based composite material is widely applied to the fields of aerospace, military traffic, ocean engineering and the like, and the research of the aluminum-based composite material becomes a research hotspot of the material industry. With the progress of scientific and technological research, the ultrahigh-temperature ceramic ZrB₂Appear in the field of vision as reinforcements for Aluminum Matrix Composites (AMCs), which have a high melting point (3250 ℃), high hardness (36GPa), high strength, high wear resistance, high chemical stability and excellent thermal conductivity, electrical conductivity, thermal shock resistance, therefore ZrB₂The particles are considered to be an ideal reinforcement for aluminum matrix composites. ZrB in aluminum matrix₂The size, shape, mass or volume fraction and spatial distribution of the ceramic particles determine the performance of the AMCs. Currently prepared ZrB₂There are many ways to enhance AMCs, mainly involving externally applying existing ZrB₂An additional method for realizing the composition of the ceramic particles and the molten aluminum by directly adding the ceramic particles into the molten aluminum and in-situ generating ZrB in the melt by utilizing the chemical reaction between an additional reactant and the aluminum melt₂In situ synthesis of particles. Compared with an external method, the aluminum matrix composite prepared by the in-situ synthesis method has the advantages of small particle size of the reinforcement, clean interface, good thermodynamic stability of the reinforcement, higher interface bonding strength and the like, and has simple process and low cost, so the method becomes one of the most potential methods for commercially producing the aluminum matrix composite.

The traditional in-situ reaction method for preparing the aluminum-based composite material needs to be carried out at high temperature (above 850 ℃), so that the problems of high energy consumption, burning loss of alloy elements such as Mg, Li, Cu, Sr and the like in matrix alloy, difficulty in controlling the reaction process, high difficulty in technological operation and the like are caused. In addition, the high-temperature reaction process is complicated, so that harmful intermediate products and metastable products are generated, and the reinforcement particles grow excessively, so that the reinforcing effect of the reinforcement particles on the aluminum matrix is weakened, and ZrB is severely restricted₂The industrialization of the particle reinforced aluminum matrix composite material develops, therefore,the low-temperature preparation of the aluminum-based in-situ composite material has important industrial application value.

Since the in-situ reaction process involves complex phase transition, in practical application, the reaction product is not composed of dispersed particles but is accompanied by a large amount of particle aggregation, and thus the obtained composite material is accompanied by a large amount of ZrB₂And (4) agglomeration of the particles. The particle agglomeration is different from physical atom cluster, but formed by ZrB in the reaction process₂Agglomerates (agglomerates) with the reaction residues, which are heterogeneous in morphology and generally between 10 and 200 μm in size. In the composite material, the particles are agglomerated to cut a matrix, so that stress concentration is caused, crack initiation is promoted, and the mechanical and machining performances of the composite material are greatly reduced.

Disclosure of Invention

Aiming at the technical problem, the invention provides a method for in-situ synthesis of nano-scale ZrB under low temperature₂A method for particle strengthening of aluminum matrix composites. The preparation method comprises the following steps:

1) two industrial-grade fluoride salts KBF₄And K₂ZrF₆Drying to remove the absorbed water vapor and crystal water, and smelting the aluminum alloy matrix in a resistance furnace or an induction furnace at low temperature;

2) according to ZrB in the target composite material₂Determining and weighing two kinds of fluorine salt, and then uniformly mixing the fluorine salt in a mortar or a mixer;

3) when the temperature of the aluminum melt reaches 660-670 ℃, removing surface slag, starting to apply high-speed mechanical stirring on the surface of the aluminum melt to form surface layer vortex, and immediately mixing KBF₄And K₂ZrF₆Adding the mixed salt into the vortex on the surface layer of the aluminum melt;

4) and after the heat preservation and the stirring are finished, removing a liquid reaction by-product on the upper layer of the aluminum melt, and heating, refining and casting.

In step (1), KBF₄And K₂ZrF₆The drying temperature is 200 +/-10 ℃, the drying time is more than 2 hours, and the drying equipment is an air blast drying box; the low-temperature melting temperature of the aluminum alloy matrix is controlled to be near the melting point of pure aluminum, namely 660-670 DEG C。

In the step (2), ZrB in the target composite material₂The mass fraction of the particles of the reinforcement is between 3 and 7 percent, and KBF₄And K₂ZrF₆According to the reaction scheme 6KBF₄+3K₂ZrF₆+10Al＝3ZrB₂+K₃AlF₆+9KAlF determined that the molar ratio of B to Zr was maintained at 2:1 and the fluoride salt was mixed by hand or using a blender.

In the step (3), the stirring intensity is 1000 rpm, and the stirring time is 15 minutes.

In the step (3), the mixed salt is added into the vortex on the surface of the melt through the charging pipe, the temperature of the mixed salt is preheated to 150 ℃ and 200 ℃, and the exothermic reaction between the mixed salt and the low-temperature aluminum melt is induced to form the nano ZrB₂And (3) granules.

In the step (4), after stirring is finished, removing byproducts on the surface of the aluminum melt immediately, raising the temperature of the melt to 720 ℃, refining, and performing metal mold casting to obtain the in-situ nanoparticle reinforced aluminum-based composite material.

The invention has the advantages that: the in-situ synthesis of the composite material is realized by means of exothermic chemical reaction under the low temperature condition (660-670 ℃), and the problems of high temperature, high energy consumption and burning loss of matrix alloy elements in the traditional in-situ reaction are solved; nanoscale ZrB can be synthesized in situ by applying high speed mechanical agitation to inhibit particle agglomeration and improve particle dispersion and size at the location where the in situ reaction is most concentrated, i.e., the surface of the aluminum melt₂The particles reinforce the aluminum matrix composite, thereby obviously improving the mechanical property of the matrix. Due to the adoption of low-temperature and in-situ reaction, the whole synthesis process is simple and quick to operate, and has great significance for realizing industrialization. In addition, this experiment mechanical stirring device is simple, the operation of being convenient for, is fit for industrial production and uses. Therefore, it is of great practical value to apply high-speed mechanical agitation to inhibit the generation of particle clusters at the location where the in-situ reaction is most concentrated, i.e., the surface of the aluminum melt.

Drawings

FIG. 1 is ZrB₂The mass fraction of the particles is 0%, 3%, 5% and 7% of the microstructure of the aluminum matrix composite.

(a)ZrB₂The content of the particles is 0 percent; (b) ZrB₂The particle content was 3%; (c) ZrB₂The particle content is 5%; (d) ZrB₂The particle content was 7%.

FIG. 2 is ZrB₂The mass fractions of the particles are 0%, 3%, 5% and 7% of the microstructure of the aluminum matrix composite material at the tensile fracture.

(a)ZrB₂The content of the particles is 0 percent; (b) ZrB₂The particle content was 3%; (c) ZrB₂The particle content is 5%; (d) ZrB₂The particle content was 7%.

FIG. 3 is ZrB₂Stress-strain curves for aluminum matrix composites with particle mass fractions of 0%, 3%, 5% and 7%.

FIG. 4 is ZrB₂The aluminum matrix composite material with the mass fraction of the particles of 0 percent, 3 percent, 5 percent and 7 percent has tensile mechanical property.

FIG. 5 is ZrB₂The aluminum matrix composite material with the mass fraction of the particles of 0 percent, 3 percent, 5 percent and 7 percent.

Detailed Description

The invention is further described with reference to the following figures and specific embodiments.

Example 1

Preparation of ZrB₂The particle reinforced aluminum-based composite material is prepared by weighing 1.5kg of industrial pure aluminum, and stirring and grinding the KBF at 665 DEG C₄And K₂ZrF₆And adding the mixed salt into the aluminum melt for reaction, wherein the mechanical stirring strength is 1000 revolutions per minute, and the mechanical stirring time is 15 min.

Keeping the temperature, mechanically stirring for 15 minutes, heating and casting to obtain the in-situ self-generated nano-scale ZrB₂The aluminum matrix composite material with the mass fractions of particles of 0%, 3%, 5% and 7% and the microstructure at the tensile fracture are shown in fig. 1 and 2, respectively. ZrB₂The particles are uniformly distributed in the matrix without severe agglomeration of the particles. The fracture of the composite material has typical ductile fracture characteristics, a large number of dimples are uniformly distributed on the surface, and brittle fracture tissues do not appear. The method can prepare the aluminum matrix composite with strong and good plastic combinationA material.

Example 2

ZrB prepared by the method₂And (3) carrying out a tensile test on the aluminum-based composite material standard sample with the particle mass fractions of 0%, 3%, 5% and 7% on an electronic universal testing machine with the model number of DDL100, wherein the tensile rate is 3 mm/min. The stress-strain curve of the composite material is shown in fig. 3, and the mechanical properties are shown in fig. 4. Therefore, the Yield Strength (YS) and the tensile strength (UTS) of the composite material prepared by the method are obviously higher than those of the matrix, which indicates that the composite material prepared by the method has higher strength.

Example 3

ZrB is measured by adopting a durometer with model number of HV-30₂The hardness of the aluminum matrix composite was measured at 0%, 3%, 5% and 7% by mass of the particles, respectively, with a test force of 5kg and a duration of 15s, and the results are shown in fig. 5. Therefore, the hardness of the composite materials with different particle contents prepared by the method is obviously higher than that of the matrix, wherein the highest hardness reaches 165HV, which shows that the composite materials prepared by the method have higher hardness.

The embodiments can know that the in-situ synthesis of the composite material is realized by virtue of the exothermic chemical reaction under the low temperature condition (660-670 ℃), and the problems of high temperature, high energy consumption, burning loss of matrix alloy elements and the like of the traditional in-situ synthesis technology are solved. Second, ZrB formed at low temperature₂The particle size is small, the dispersion is uniform, and the comprehensive mechanical property of the matrix can be obviously improved. In addition, due to the adoption of low-temperature and in-situ reaction, the whole synthesis process is simple and quick to operate, and has great significance for realizing industrialization.