CN116815006A - Method for preparing in-situ synthesized nanoparticle-reinforced aluminum matrix composites by centrifugal reaction - Google Patents

Abstract

The invention relates to the technical field of aluminum-based composite materials, and in particular to the preparation of nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction and its preparation method, which includes: S1. Melting the first AlSi12 eutectic alloy crucible, raising the temperature to 600±10°C, and maintaining the temperature. Adjust the rotation speed of the crucible until the eutectic alloy liquid surface forms a "U" shape and closely adheres to the inner wall of the crucible to obtain material 1; S2. Add mixed salt to material 1. After the mixed salt is completely melted, continue to add the second AlSi12 total into the crucible. crystal alloy, keep the crucible temperature no higher than 650°C, after reacting for 10 to 20 minutes, slowly reduce the rotation speed to 0, remove the slag after the liquid level is stable, and perform desalination treatment to obtain material 2; S3. Raise the temperature of material 2 to 760 to 760°C. 780°C, add intermediate metal, control the temperature to 700~720°C, add elements that are prone to burnout for melt refining treatment, and pour to obtain nanoparticle-reinforced aluminum-based composite materials, which solves the problem of small reaction interface and long reaction duration in traditional processes , high heat release and other problems that make it difficult to control the reaction process.

Description

Method for preparing in-situ synthesized nanoparticle-reinforced aluminum matrix composites by centrifugal reaction

Technical field

The present invention relates to the technical field of aluminum-based composite materials, and in particular to the preparation of nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction and a preparation method thereof.

Background technique

Nanoparticle-reinforced aluminum-based composite materials have excellent comprehensive mechanical properties and have broad application space in aerospace, weapons, ships, electronics, automobiles and other fields. The preparation of nanoparticle-reinforced aluminum matrix composites by the fluoride salt method has the advantages of simple process and low cost, and is considered to be the most potential method for in-situ synthesis of nanoparticle-reinforced aluminum matrix composites for engineering applications. The fluoride salt method is a thermite reaction of liquid titanium aluminum with titanium salt (or zirconium salt) and boron salt, and finally forms TiB ₂ (or ZrB ₂ ) nanoparticles. On the one hand, the thermite reaction is an exothermic reaction, the reaction process is violent, the reaction products are numerous and miscellaneous, and the size range is wide, making it difficult to control. At present, the method of appropriately lowering the reaction temperature is mainly used to control it. On the other hand, the content of Ti element and B element in titanium salt and boron salt is low, with their mass fractions being 19.9% and 8.6% respectively. Even if the yield of Ti element and B element during the reaction is 100%, 7kg of mixed salt is required for every 1kg of TiB ₂ synthesized. When preparing a 5wt.% TiB ₂ /Al composite material, the weight of the mixed salt accounts for 36.8% of the weight of the alloy, that is, the molten salt accounts for one-third of the crucible volume. A large amount of molten salt continues to react violently at the interface between the alloy liquid and the molten salt through convection, causing the melt at the reaction interface to continue to heat up and the reaction products to grow rapidly. In addition, a large amount of residual molten salt enters the melt, causing particle agglomeration and difficulty in melt purification. Many problems. In order to obtain reinforced particles with high size concentration and good dispersion, domestic and foreign technicians generally choose a lower reaction temperature and implement strong stirring (including electromagnetic stirring and mechanical stirring).

Chinese Patent 202011306962.1 discloses a method for preparing in-situ nanoparticle-reinforced aluminum-based composite materials at low temperature. The reaction temperature is 660-670°C. High-speed mechanical stirring is applied to the surface of the melt to form a vortex, and the mixed salt is added to the vortex on the surface of the melt. React for 15 minutes. This technology suppresses particle agglomeration and improves particle dispersion and size by applying rapid mechanical stirring at the reaction interface. While adding salt to the surface vortex, a large amount of air will be introduced into the melt, resulting in a large amount of residual molten salt inside the melt. , oxides and gases, leading to an increase in melt viscosity and making it difficult to purify the melt. The research by Liu Zhengcai et al. (Research status of TiB ₂ particle-reinforced aluminum matrix composites by mixed salt method [J]. Thermal Processing Technology, 2021, 12(50) pp: 17-21) shows that low-speed stirring cannot effectively break clusters, and high-speed stirring cannot effectively break the clusters. Stirring will increase hydrogen absorption and oxidation, and will introduce surface impurities, thereby reducing the mechanical properties of the composite material.

Chinese patents 202011571152.9, 202011571153.3, and 202011571141.0 propose systems and methods for preparing in-situ self-generated aluminum-based composites using pulsed magnetic fields, with a reaction temperature of 700 to 760°C and simultaneous vacuuming; Chinese patent 200510029902.9 discloses in-situ particle-reinforced high-temperature-resistant aluminum-based composites According to the preparation method of the material, the reaction temperature is 680 to 800°C. After the reaction is completed, alloy elements are added, and the mixture is evacuated and left to stand. This method fails to deal with the residual salt in the melt in time after the reaction is completed. The addition of alloying elements will cause the viscosity of the melt to further increase, making the melt purification process more difficult. The reaction temperature is higher and does not involve the impact of the increase in reaction temperature on the reaction process. In order to avoid the problem of difficulty in melt purification due to the introduction of residual molten salt into the melt by the fluorine salt method, Chinese Patent 202111585762.9 proposes a method for preparing controllable TiB ₂ in-situ reinforced aluminum-based composite materials, using boron alloy and aluminum-titanium alloy or pure Titanium is used as raw material, reacts at 800~850℃, and uses argon gas to refine and degas. It can be seen that the existing technology does not involve residual molten salt purification technology, nor does it involve technology to increase the reaction interface through centrifugal force to thereby regulate the reaction rate, particle size and dispersion.

At present, the existing technology adopts the method of temperature reaction in terms of reaction temperature control. The present invention found that when the melting amount ranges from hundreds of kilograms to several tons, the melt temperature during the reaction rises by approximately 80 to 100°C. A substantial increase in melt temperature leads to an increase in reaction speed, while the convection or diffusion speed (constant mechanical stirring or equal-power acoustic-magnetic coupling field) remains unchanged, which will inevitably cause the enhanced particle size to grow or aggregate, eventually leading to the enhanced particle size range span Large and unevenly dispersed. During the reaction process, molten salt inevitably enters the interior of the melt, causing the viscosity of the melt to increase. The disclosed technical solutions usually use traditional methods to purify the melt before pouring. In fact, alloying will cause the melt viscosity to further increase, making the melt purification process more difficult. Further improving the controllability of the reaction process and obtaining nano-reinforced particles with consistent size, morphology, and uniform dispersion as well as pure melts are problems that researchers and technicians in this field are committed to solving.

Contents of the invention

In view of the deficiencies in the prior art, the present invention provides a preparation method for in-situ synthesis of nanoparticle-reinforced aluminum-based composite materials that reacts stably at extremely low temperatures.

A first aspect of the present invention provides a method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction. The preparation method includes the following steps:

S1. Melt the first AlSi12 eutectic alloy crucible, raise the temperature to 600±10°C, keep it warm, and adjust the crucible speed until the eutectic alloy liquid level forms a "U" shape and adheres to the inner wall of the crucible to obtain material 1;

S2. Add mixed salt to material 1. After the mixed salt is completely melted, continue to add the second AlSi12 eutectic alloy to the crucible. Keep the temperature of the crucible no higher than 650°C. After reacting for 10 to 20 minutes, slowly reduce the rotation speed to 0, and the liquid After the surface is stabilized, the slag is removed and desalted to obtain material 2;

S3. Raise the temperature of material 2 to 760-780°C, add intermediate metal, control the temperature to 700-720°C, add easily burnt elements for melt refining treatment, and pour to obtain nanoparticle-reinforced aluminum-based composite materials.

In some embodiments, the crucible rotation speed is adjusted to 3000-4000 r/min as described in S1.

During the research process, the applicant found that the crucible rotation speed was too low, the liquid level was not concave enough, or it was difficult to form a "U"-shaped liquid level, which was not conducive to establishing a sufficient reaction interface, resulting in low reaction efficiency. If the rotation speed is too high, the high-density reinforced particles will agglomerate under the obstruction of the crucible side wall under the action of centrifugal force, and increase energy consumption and equipment manufacturing costs. The definition of the "U" shape in the present invention is that during the rotation of the crucible, the liquid level close to the inner wall of the crucible is higher than the liquid level at the bottom of the crucible, which can be considered to form a "U" shape.

Further, the vertical distance from the highest point to the lowest point of the "U"-shaped liquid level is 2/3-3/4 of the crucible height.

In some embodiments, the mixed salt is a baked mixture of potassium fluotitanate and potassium fluoborate.

Further, the molar ratio of Ti atoms and B atoms in the potassium fluotitanate and potassium fluoborate is 1:2.

In some embodiments, the addition amount of the second AlSi12 eutectic alloy is 5-10 wt% of the addition amount of the mixed salt.

The addition amount of the second AlSi12 eutectic alloy is too low to achieve the expected cooling effect, and the addition amount is too high, causing the melt temperature to be lower than the liquidus line, which is not conducive to the dispersion of micro-nano reinforced particles in the melt.

The order of addition of the second AlSi12 eutectic alloy plays a key role. The melting speed of AlSi12 added to the melt is much higher than that of the mixed salt. When added before or together with the mixed salt, the melt temperature first decreases rapidly, and then during the reaction Under the influence of heat, it rises rapidly, failing to control the significant increase in melt temperature during the reaction process, and thereby failing to achieve the purpose of enhancing particle size control.

In some embodiments, the outline dimensions of the second AlSi12 eutectic alloy are less than 30×30×30 mm.

Second, if the outline size of the AlSi12 eutectic alloy is too large, it will cause a large local temperature drop, and it will take a long time to reach the equilibrium temperature through heat conduction, which is not conducive to controlling the uniformity of the melt temperature. If the contour size is too small, a large amount of oxide film will be introduced into the melt.

In some embodiments, the temperature of the desalination treatment is controlled at 600-630°C, the pressure is no more than 500 Pa, and the time is 15-30 minutes.

In some embodiments, the melt refining process is specifically: using an argon rotary blowing method to perform the melt refining process, with a rotation speed of 300 to 600 r/min, an argon pressure of 1 to 2 MPa, and a refining time of 15 to 25 minutes.

Further, the intermediate metal can be selected from types commonly used in the art, including but not limited to pure aluminum ingots.

Furthermore, the easy-to-burn elements can be selected from types commonly used in the art, including but not limited to pure magnesium.

The reaction temperature in the prior art is generally 750 to 900 degrees, and the lowest temperature in reports has been 660 to 670 degrees. The present invention starts from adding mixed salt (600±10°C) until the reaction is completed and the slagging operation is completed. In this stage, the temperature of the melt during the reaction process is significantly lower than that of the prior art. The applicant found that the reaction temperature has the most significant impact on the size of the reinforced particles. The higher the reaction temperature, the larger the size of the generated reinforced particles. When the reaction temperature is greater than 1000°C, a large number of reinforced particles with sizes in the micron range are generated. When the reaction temperature is between 700 and 900°C, the size distribution range of the generated reinforced particles is wide, and both nano-sized and micron-sized particles exist. The reaction temperature is lower than 650°C, and the generated reinforced particles are almost all in the nanometer range. Adopting a higher reaction temperature is beneficial to subsequent melt purification processing, because the residual salts or alkali metals in the melt volatilize under the action of high temperature, reducing the difficulty of subsequent purification. When the reaction temperature is low, residual salts or alkali metals in the melt are difficult to volatilize, which makes subsequent melt purification difficult. The present invention uses vacuum desalination treatment after the reaction is completed to promote and accelerate the volatilization of residual salts or alkali metals in the melt by establishing a vacuum above the liquid level, thereby reducing the difficulty of subsequent melt purification, thereby solving the problem of low-temperature reactions caused by Melt purification is difficult.

In some embodiments, the size of the nanoparticles in the nanoparticle-reinforced aluminum-based composite material is 80 to 90 nm.

In some embodiments, the nanoparticle reinforced aluminum matrix composite has an elongation of not less than 6%.

In the present invention, the relationship between the centrifugal force experienced by the nanoparticles and their own volume and rotational speed is as follows:

Among them, F is the centrifugal force experienced by the nanoparticles; ρ is the density of the nanoparticles; V is the volume of the nanoparticles; v is the linear velocity of the nanoparticles; r is the distance from the nanoparticles to the center of rotation.

The density of the reaction product TiB ₂ (or ZrB ₂ ) particles is greater than that of the aluminum melt, and they quickly break away from the reaction interface under the action of centrifugal force, and subsequent growth is inhibited. By adjusting the rotation speed of the crucible, the centrifugal force exerted on the nanoparticles is changed, and the volume of the nanoparticles separated from the reaction interface is controlled, thereby controlling the size of the nanoparticles. At the same time, centrifugal force helps improve the dispersion of nanoparticles.

The present invention performs vacuum desalting treatment after the reaction is completed, and the free K ⁺ , H ⁺ , and F ^- ions in the melt can quickly escape from the melt, thereby achieving the purpose of removing the residual molten salt in the melt and simultaneously degassing and removing the salt. The role of slag. First remove the residual molten salt, and then raise the temperature of the melt for alloying, which can not only reduce the difficulty of melt purification, but also avoid further reaction of the residual molten salt after raising the temperature, causing the reinforced particles to continue to grow, which is conducive to obtaining uniform and fine sizes. Nano-reinforced particles and pure alloy melt.

A second aspect of the present invention provides a nanoparticle-reinforced aluminum-based composite material obtained by the preparation method.

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

In the present invention, a motor installed at the bottom of the crucible drives the crucible to rotate to generate centrifugal force. Under the action of the centrifugal force, the alloy liquid clings to the crucible wall to form a "U-shaped" liquid surface. After the mixed salt is melted, it spreads on the "U" liquid surface, significantly increasing the size of the alloy. The contact area between the liquid and the molten salt improves the reaction efficiency, facilitates the diffusion of reaction products, and improves the dispersion of particles. In addition, the large reaction interface increases the heat dissipation area, which is conducive to the conduction of heat released by the reaction and further improves the stability of the reaction process. It solves the problems in traditional processes such as small reaction interface, long reaction duration, large heat release, etc. that make the reaction process difficult to control.

Description of the drawings

Figure 1 is a schematic diagram of the equipment for preparing nanoparticle-reinforced aluminum-based composite materials according to the present invention, in which 1-crucible; 2-alloy melt; 3-molten salt; 4-motor transmission keyway.

Figure 2 shows the particle size, morphology and distribution diagram of the TiB ₂ (10wt.%)/ZL101A composite material prepared in Example 1.

Figure 3 shows the particle size, morphology and distribution diagram of the TiB ₂ (10wt.%)/ZL114A composite material prepared in Example 2.

Figure 4 shows the particle size, morphology and distribution of the TiB ₂ (10wt.%)/ZL101A composite material prepared in Comparative Example 1.

Figure 5 shows the particle size, morphology and distribution of the TiB ₂ (10wt.%)/ZL114A composite material prepared in Comparative Example 2.

Detailed ways

The technical solutions in the embodiments of the present invention will be described clearly and completely below. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

Example 1

This embodiment provides a method for preparing TiB ₂ (10wt.%)/ZL101A composite material. The preparation method includes the following steps:

S1. Add the first AlSi12 eutectic alloy (51.3kg) to the crucible to melt, raise the temperature to 600±10°C, keep it warm, and adjust the crucible speed to 4000r/min until the eutectic alloy liquid level forms a "U" shape close to the inner wall of the crucible. , the vertical distance from the highest point to the lowest point of the "U"-shaped liquid level is 2/3 of the height of the crucible, and material 1 is obtained;

S2. Add 70.8kg of mixed salt (potassium fluotitanate and potassium fluoborate, Ti and B molar ratio is 1:2) into material 1. After the mixed salt is completely melted, add 7kg of the second AlSi12 eutectic alloy to the crucible. (The outline dimensions are all less than 30×30×30mm, and the addition amount is 10% of the weight of the mixed salt). Keep the crucible temperature no higher than 650°C. After 15 minutes of reaction, slowly reduce the rotation speed to 0. After the liquid level is stable, remove the slag and control the temperature. At 620~650℃, the pressure is no more than 500Pa, and the time is 20 minutes. Perform desalination treatment to obtain material 2;

S3. Raise the temperature of material 2 to 770°C, add 32kg pure aluminum ingots and 2.5kg AlTi4 intermediate metal, control the temperature to 710°C, add 0.7kg pure magnesium, an easy-to-burn element, and use argon gas rotary blowing method for melt refining. Processing, melt refining treatment, rotation speed 500r/min, argon pressure 1MPa, refining time 20min, pouring, to obtain nanoparticle reinforced aluminum matrix composite material.

As shown in Figure 2, the TiB ₂ particle size of the TiB ₂ (10wt.%)/ZL101A aluminum matrix composite prepared in this example is concentrated in 80-90nm. After T6 heat treatment, the test method of GB/T 228.1-2010 is used , the tensile strength is 398MPa, the yield strength is 354MPa, and the elongation is 8%.

Example 2

This embodiment provides a method for preparing TiB ₂ (10wt.%)/ZL114A composite material. The preparation method includes the following steps:

S1. Add the first AlSi12 eutectic alloy (52.6kg) to the crucible to melt, raise the temperature to 600±10°C, keep it warm, and adjust the crucible speed to 3000r/min until the eutectic alloy liquid level forms a "U" shape close to the inner wall of the crucible. , the vertical distance from the highest point to the lowest point of the "U"-shaped liquid level is 3/4 of the height of the crucible, and material 1 is obtained;

S2. Add 70.8kg of mixed salt into material 1, in which the atomic ratio of Ti and B is 1:2. After the mixed salt is completely melted, continue to add 5.7kg of the second AlSi12 eutectic alloy into the crucible (the outline dimensions are all less than 30×30 ×30mm, the addition amount is 8% of the weight of the mixed salt), keep the crucible temperature no higher than 650℃, after 30 minutes of reaction, slowly reduce the rotation speed to 0, remove the slag after the liquid level is stable, control the temperature at 620~650℃, and the pressure should not be Greater than 500Pa, perform desalination treatment for 20 minutes to obtain material 2;

S3. Raise the temperature of material 2 to 770°C, add 35kg pure Al ingot and 2.5kg AlTi4 intermediate metal, control the temperature to 710°C, add 0.9kg pure magnesium, an easy-to-burn element, and use argon gas rotary blowing method for melt refining. Processing, melt refining treatment, rotation speed 600r/min, argon pressure 2MPa, refining time 25min, pouring, to obtain nanoparticle reinforced aluminum matrix composite material.

As shown in Figure 3, the TiB ₂ particle size of the TiB ₂ (10wt.%)/ZL114A aluminum matrix composite prepared in this example is concentrated in 80-90nm. After T6 heat treatment, the test method of GB/T 228.1-2010 is used , the tensile strength is 428MPa, the yield strength is 363MPa, and the elongation is 6%.

Comparative example 1

This comparative example provides a preparation method of TiB ₂ (10wt.%)/ZL101A composite material. The specific implementation method is the same as Example 1. The difference is that step S1. Melt the first AlSi12 eutectic alloy crucible and heat it to 600±10℃, heat preservation, and obtain material 1.

As shown in Figure 4, the TiB ₂ particle size of the prepared TiB ₂ (10wt.%)/ZL101A aluminum matrix composite material is concentrated in 80 to 90 nm. After T6 heat treatment, the tensile strength is 334MPa, the yield strength is 195MPa, and the elongation is 1.5%.

Comparative example 2

This comparative example provides a method for preparing TiB ₂ (10wt.%)/ZL114A composite material. The specific implementation method is the same as that of Example 2. The difference is that the second AlSi12 eutectic alloy is not added in step S2.

As shown in Figure 5, the TiB ₂ particle size of the prepared TiB ₂ (10wt.%)/ZL114A aluminum matrix composite material is concentrated at 300 nm, and the agglomeration tendency is serious. After T6 heat treatment, the tensile strength is 355MPa, the yield strength is 280MPa, and the elongation is 3.5%.

The above is the preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications It should also be regarded as the protection scope of the present invention.

Claims (10)

1. A method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction, characterized in that the preparation method includes the following steps: S1. Melt the first AlSi12 eutectic alloy crucible, raise the temperature to 600±10°C, keep it warm, and adjust the crucible speed until the eutectic alloy liquid level forms a "U" shape and adheres to the inner wall of the crucible to obtain material 1; S2. Add mixed salt to material 1. After the mixed salt is completely melted, continue to add the second AlSi12 eutectic alloy to the crucible. Keep the temperature of the crucible no higher than 650°C. After reacting for 10 to 20 minutes, slowly reduce the rotation speed to 0, and the liquid After the surface is stabilized, the slag is removed and desalted to obtain material 2; S3. Raise the temperature of material 2 to 760-780°C, add intermediate metal, control the temperature to 700-720°C, add easily burnt elements for melt refining treatment, and pour to obtain nanoparticle-reinforced aluminum-based composite materials. 2. The method for preparing nanoparticle-reinforced aluminum matrix composite materials by centrifugal reaction according to claim 1, characterized in that the crucible rotation speed is adjusted to 3000-4000 r/min as described in S1. 3. The method for preparing nanoparticle-reinforced aluminum matrix composite materials by centrifugal reaction according to claim 1, characterized in that the addition amount of the second AlSi12 eutectic alloy is 5-10 wt% of the addition amount of the mixed salt. 4. The method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction according to claim 1, wherein the mixed salt is a mixture of baked potassium fluotitanate and potassium fluoborate. 5. The method for preparing nanoparticle-reinforced aluminum matrix composite materials by centrifugal reaction according to claim 1, characterized in that the outline dimensions of the second AlSi12 eutectic alloy are all less than 30×30×30 mm. 6. The method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction according to claim 1, characterized in that the temperature of the desalination treatment is controlled at 600-630°C, the pressure is not greater than 500Pa, and the time is 15- 30 minutes. 7. The method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction according to claim 1, characterized in that the melt refining process is specifically: using an argon gas rotary blowing method to carry out the melt refining process, the rotation speed 300～600r/min, argon pressure 1～2MPa, refining time 15～25min. 8. The method for preparing nanoparticle-reinforced aluminum-based composite materials by centrifugal reaction according to claim 1, characterized in that the size of the nanoparticles in the nanoparticle-reinforced aluminum-based composite material is 80 to 90 nm. 9. The method for preparing nanoparticle-reinforced aluminum matrix composite materials by centrifugal reaction according to claim 1, characterized in that the elongation rate of the nanoparticle-reinforced aluminum matrix composite material is not less than 6%. 10. A nanoparticle reinforced aluminum matrix composite material obtained according to the preparation method according to any one of claims 1 to 9.