CN101892407A - A method for preparing aluminum-based in-situ composite materials by low-temperature catalysis - Google Patents

Abstract

The invention provides a method for preparing an aluminum-based composite material through low-temperature catalysis, which belongs to the technical field of material preparation. The method is to add a catalyst to the reaction salt for preparing composite materials, which can complete the in-situ reaction between the reaction salt and the aluminum melt under the condition of lower than the conventional synthesis temperature, and can accelerate the reaction rate, shorten the reaction time, and ensure that the composite material The microstructure characteristics of the same, including particle type, size and distribution, are suitable for the preparation of aluminum matrix composites on an industrial scale.

Description

A method for preparing aluminum-based in-situ composite materials by low-temperature catalysis

technical field

The invention relates to the technical field of preparation of metal-based composite materials, and aims at realizing the low-temperature catalytic preparation of aluminum-based composite materials by adding a catalyst to a reaction mixed salt.

Background technique

Aluminum matrix composites combine the advantages of aluminum matrix and reinforcing phase, and have excellent properties such as high specific strength, specific stiffness, and high wear resistance, and are an important part of new material research and development. From the perspective of particle introduction methods, there are two types: external and endogenous. Endogenous particles have the advantages of clean interface and small particle size. Correspondingly, many in-situ endogenous methods have been derived. Among them, the melt direct reaction method is to add the reaction salt powder containing granular elements to the aluminum/aluminum alloy melt at the synthesis temperature to make it fully react, and to prepare endogenous particles in the melt, which can be directly cast with complex shapes. of castings. Therefore, it has the advantages of simple process, low cost, short cycle, and easy industrial production, and is unanimously considered by industry insiders as a new technology that has the potential to realize industrial application.

According to the existing literature reports, in the field of metal matrix composites research, the research hotspots mainly focus on the following aspects:

1. Research and develop new composite systems, such as Al-O, Al-Ti-C, Al-Ti/Zr-B, Al-Ti/Zr, etc. At present, the main reinforcement phase particles include intermetallic compounds, oxides, nitrides, carbides and borides, etc.;

2. Optimize the preparation process according to the characteristics of the system, generally including: reaction temperature, reaction time, type of reactant and appropriate addition amount, etc.;

3. Optimizing the reaction conditions through various methods, including using external physical fields, such as ultrasonic fields, electromagnetic fields or acousto-magnetic coupling fields.

However, from the perspective of industrial-scale application prospects, in order to promote the industrial preparation of composite materials, it is necessary to overcome and solve the following key "bottleneck" problems:

1. The molten aluminum is required to have a higher temperature. The reaction salt needs a higher reaction temperature to react with the aluminum liquid and form a thermodynamically stable strengthening phase. Judging from the current literature reports, it is generally required that the molten aluminum is overheated at 100-150°C, that is, the initial melt temperature is required to be at 800-1000°C. Because aluminum will inhale and generate inclusions at high temperatures, and the inhalation will increase with the increase of temperature, and the quality of molten aluminum will deteriorate seriously. At the same time, under the condition of high superheat, the driving force for particle growth is strong, and some particles are easy to grow into large-sized inclusion phases. Therefore, if aluminum-based composite materials can be prepared at lower temperatures, it will promote the industrial application of composite materials;

2. Long response time is required. To complete the in-situ reaction between the solid reaction salt and the aluminum liquid, it takes a long time to realize the contact, mass transfer and reaction between the solid phase and the liquid phase. The time range is generally 25-50min, the preparation cycle is long, and the aluminum liquid stays for a long time at high temperature, which increases the suction and burning loss. If composite materials can be prepared in a short period of time, it will promote the industrial application of composite materials.

3. The literature search shows that the invention patents related to this technology include: National Invention Patent 200810134310.4, which proposes to reduce the synthesis temperature of metal matrix composite materials through the multi-component flux combination method, which is to mix one or more low-melting point substances into the In the mixed salt, the reaction salt is melted at the in-situ reaction temperature to be in a liquid state, the efficiency of the liquid-liquid phase reaction is higher than that of the solid-liquid phase reaction, and the temperature of the liquid-liquid phase reaction is also lower than that of the same reaction salt in the solid-liquid phase. The temperature at which the reaction occurs in the phase state can reduce the in-situ reaction temperature. Its shortcomings are: the added fluorine salt fluxing components will further increase the harm of fluorine salt to the human body and the environment, and the added fluoride salt will partially react with the reaction salt, resulting in partial reaction salt failure and affecting the particle yield; Both, for some high melting point reaction salts, such as some carbonates, the added flux cannot make it change from solid to liquid under the reaction temperature conditions, and the effect of reducing the reaction temperature is not obvious. The present invention is different from it in that: graphite or spinel catalysts are added to the mixed salt, which will not pollute the environment. At the same time, there are no restrictions on the type of reaction salt and the height of the melting point. The mechanism and basis for reducing the synthesis temperature after adding the catalyst are Catalytic theory, that is: effectively reduce the activation energy of reactant molecules, improve reaction efficiency, and shorten synthesis time.

In summary, the present invention applies the catalytic technology commonly used in the field of chemistry to the field of metal material preparation to realize the low-temperature catalytic preparation of metal matrix composites, making the in-situ synthesis process have the characteristics of short time and high efficiency, and meeting the requirements of modern industrial The requirements of "energy saving and high efficiency" help to promote the industrial preparation process of high-performance metal matrix composites.

Contents of the invention

The content of the present invention is to provide various types of catalysts. A certain type and a certain amount of catalysts are mixed into the reaction salt to ensure that the two are evenly mixed, which can reduce the reaction temperature, increase the reaction rate, and shorten the reaction time. A new method for low-cost and high-efficiency preparation of high-performance metal matrix composites

The purpose of the present invention is achieved through the following technical solutions:

The first step: the preparation of raw materials.

Prepare the reaction salt, control its preheating temperature at 200-250°C, particle size at 200 mesh, and calculate the proportion according to the reaction equation, and add a catalyst to the prepared reaction salt. The catalyst is: carbon nanotubes, artificial graphite , Al-Mg spinel or natural graphite, the ratio of the catalyst addition to the total amount of reaction salt is: 1-5wt.%,; after fully grinding and mixing, mixed salt powder is obtained, and it is set aside; aluminum or aluminum alloy ingots are placed in an aluminum melting furnace Medium melting, the temperature is 40-80°C lower than the conventional synthesis temperature.

The second step: Synthesis of composite materials.

Add the preheated mixed salt powder into the high-temperature melt with a bell jar, and stir fully to ensure that the powder is fully in contact with the melt. After a certain reaction time, the in-situ reaction is completed, and a small amount of scum on the surface is removed at this time. After refining, it is poured and cooled with the mold.

The addition amount of above-mentioned catalyst is adjusted because of catalyst effect and reaction system difference. When the catalytic effect is good or the original synthesis temperature of the reaction system (the synthesis temperature when no catalyst is added) is low, the lower limit is taken as the amount, such as 1-2wt.%; when the catalytic effect is poor or the original synthesis temperature of the reaction system is high, the upper limit is taken; such as 4- 5wt.%; the catalytic effect is good, but the original synthesis temperature is high, or the catalytic effect is poor, but the original synthesis temperature is low, take an intermediate value, such as 3wt.%. The above-mentioned catalysts are ranked according to the use effect: carbon nanotubes, artificial graphite, aluminum-magnesium spinel, and natural graphite.

Compared with the prior art, the present invention has the following advantages and effects:

1. Particle-reinforced aluminum-based composite materials can be prepared at relatively low temperatures. The temperature required for smelting and synthesis is low, and the overheating of aluminum is small, which is suitable for industrial preparation;

2. The catalyst can increase the reaction rate, shorten the reaction time, help to improve production efficiency, and is suitable for industrial preparation;

3. The amount of catalyst used is small, the cost is low, and it is suitable for industrial preparation;

4. After using the catalyst, the composite material can be prepared at low temperature in a short time, and the structure characteristics of the material will not be affected. It has high cost performance and is of great value to the industrial promotion and application of metal matrix composite materials.

Description of drawings

Figure 1K ₂ TiF ₆ -KBF ₄ component prepared composite material scanning electron microscope, the particle phase in the figure is TiB ₂

Figure 2 SEM image of the composite material prepared by K ₂ TiF ₆ -KBF ₄ components after doping carbon nanotubes, the particle phase in the figure is TiB ₂

Figure 3K ₂ ZrF ₆ -KBF ₄ component prepared composite material scanning electron microscope, the particle phase in the figure is ZrB ₂

Fig. 4 SEM images of composite materials prepared by K ₂ ZrF ₆ -KBF ₄ components after doping artificial graphite, the particle phase in the figure is ZrB ₂

Fig.5 SEM image of the composite material prepared by K ₂ ZrF ₆ -KBF ₄ components after doping spinel, the particle phase in the figure is ZrB ₂

Fig.6 SEM image of composite material prepared by Zr(CO ₃ ) ₂ components, the particle phase in the figure is Al ₂ O ₃

Fig. 7 SEM image of composite material prepared by Zr(CO ₃ ) ₂ components after doping natural graphite, the particle phase in the figure is Al ₂ O ₃

Detailed ways

The present invention will be further elaborated below in conjunction with embodiment. The examples are only used to illustrate the present invention and not to limit the present invention in any way.

Example 1: Low-temperature catalytic preparation of carbon nanotubes of _TiB2 particle-reinforced aluminum matrix composites

Using potassium fluorotitanate K ₂ TiF ₆ and potassium fluoroborate KBF ₄ as reaction salts, TiB ₂ particle reinforced aluminum matrix composites were prepared by mixed salt reaction method. Use a bell jar to add the preheated mixed salt powder into the high-temperature melt in batches, and stir thoroughly to ensure that the powder is fully in contact with the melt. When no catalyst is added, the optimized synthesis temperature is 870-900°C, and the suitable reaction time is 25-30min. The structure of the prepared composite material is shown in Figure 1.

The carbon nanotubes with 1.2wt.% of the salt mass are mixed into the mixed salt. Then the in-situ reaction can be completed at 820-830°C, and the reaction time can be shortened to 10-15min. The structure of the prepared composite material is shown in Figure 2, which is not significantly different from that in Figure 1.

The results show that after doping a certain amount of catalyst in the mixed salt, the reaction temperature can be lowered by 40-80°C, and the reaction time can be shortened by 10-20 minutes without affecting the structure characteristics of the composite material.

Example 2 Low-temperature Catalytic Preparation of Artificial Graphite of _ZrB2 Particle Reinforced Aluminum Matrix Composite

Using potassium fluorozirconate K ₂ ZrF ₆ and potassium fluoroborate KBF ₄ as reaction salts, ZrB ₂ particle reinforced aluminum matrix composites were prepared by mixed salt reaction method. Use a bell jar to add the preheated mixed salt powder into the high-temperature melt in batches, and stir thoroughly to ensure that the powder is fully in contact with the melt. When no catalyst is added, the optimized synthesis temperature is 880-900°C, and the suitable reaction time is 20-25min. The structure of the prepared composite material is shown in Figure 3.

Add the artificial graphite powder of salt quality 2wt.% in mixed salt. Then the in-situ reaction can be completed at 830-840°C, and the reaction time can be shortened to 10 minutes. The structure of the prepared composite material is shown in Figure 4, which is not significantly different from that in Figure 3.

The results show that after doping a certain amount of catalyst in the mixed salt, the reaction temperature can be reduced by 40-70°C, and the reaction time can be shortened by 10-15 minutes without affecting the structure characteristics of the composite material.

Example 3 Cryolite Catalytic Preparation of _ZrB2 Particle Reinforced Aluminum Matrix Composites at Low Temperature

Using potassium fluorozirconate K ₂ ZrF ₆ and potassium fluoroborate KBF ₄ as reaction salts, ZrB ₂ particle reinforced aluminum matrix composites were prepared by mixed salt reaction method. Use a bell jar to add the preheated mixed salt powder into the high-temperature melt in batches, and stir thoroughly to ensure that the powder is fully in contact with the melt. When no catalyst is added, the optimized synthesis temperature is 880-900°C, and the suitable reaction time is 20-25min. The structure of the prepared composite material is shown in Figure 3.

The mixed salt is mixed with 3wt.% aluminum-magnesium spinel of the salt mass. Then the in-situ reaction can be completed at 830°C, and the reaction time can be shortened to 10 minutes. The structure of the prepared composite material is shown in Figure 5, which is not significantly different from that in Figure 3.

The results show that after doping a certain amount of catalyst in the mixed salt, the reaction temperature can be reduced by 50-70°C, and the reaction time can be shortened by 10-15 minutes without affecting the structure characteristics of the composite material.

Example 4 Preparation of Al ₂ O ₃ Particle Reinforced Aluminum Matrix Composite with Natural Graphite at Low Temperature Catalysis

Al ₂ O ₃ particle reinforced aluminum matrix composites were prepared by melt direct reaction method with zirconium carbonate as reaction salt. When no catalyst is added, the optimized synthesis temperature is 850-870°C, and the suitable reaction time is 25-30min. The structure of the prepared composite material is shown in Figure 6.

Add 5wt.% natural graphite in the mixed salt as a catalyst. Then the in-situ reaction can be completed at 820-830°C, and the reaction time can be shortened to 10-15 minutes. The structure of the prepared composite material is shown in Figure 7, which is not significantly different from that in Figure 6.

Claims (5)

1. A method for preparing aluminum-based in-situ composite materials by low-temperature catalysis, characterized in that: a catalyst is added to the reaction salt, and the in-situ reaction between the reaction salt and the aluminum melt is completed below the conventional synthesis temperature condition, reaching The experimental purpose of preparing particle-reinforced aluminum-based composite materials. The catalyst is carbon nanotubes, artificial graphite, aluminum-magnesium spinel, and natural graphite. The proportion of the catalyst added to the total amount of reaction salts is: 1-5wt% . 2. The method for preparing aluminum-based in-situ composite materials by low-temperature catalysis according to claim 1, characterized in that: the catalysts are ranked in order according to the use effect: carbon nanotubes, artificial graphite, aluminum-magnesium spinel , Natural graphite. 3. A method for preparing aluminum-based in-situ composite materials by low-temperature catalysis according to claim 1, characterized in that: compared with the conventional synthesis temperature, the synthesis temperature is reduced by 40-80°C after adding the catalyst. 4. A kind of low-temperature catalytic method for preparing aluminum-based in-situ composite material according to claim 1, specifically: (1) Preparation of raw materials Prepare the reaction salt, control its preheating temperature at 200-250 ° C, particle size at 200 mesh, and calculate the proportion according to the reaction equation, and add a catalyst to the prepared reaction salt. The optional catalysts are: carbon nanotubes, artificial Graphite, Al-Mg spinel or natural graphite, the ratio of the catalyst addition to the total amount of reaction salts is: 1-5wt.%. After fully grinding and mixing, the mixed salt powder is obtained for use; the aluminum or aluminum alloy ingots are melted in an aluminum melting furnace, and the temperature is 40-80°C lower than the conventional synthesis temperature; (2) Synthetic composite materials Use a bell jar to add the preheated mixed salt powder into the high-temperature melt, stir well to ensure full contact between the powder and the melt, after completing the in-situ reaction, remove a small amount of scum on the surface, pour it after refining, and follow the mold cool down. 5. A method for preparing aluminum-based in-situ composite materials by low-temperature catalysis according to claim 1, characterized in that: the amount of the catalyst added is adjusted due to the catalyst effect and the reaction system, and the catalytic effect is good or the original synthesis temperature of the reaction system When the dosage is low, take the lower limit; when the catalytic effect is poor or the original synthesis temperature of the reaction system is high, take the upper limit; when the catalytic effect is good but the original synthesis temperature is high, or the catalytic effect is poor but the original synthesis temperature is low, take the middle value.

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