CN115921876A - Preparation method of uniform composite powder of double-scale silicon carbide and aluminum powder - Google Patents

Abstract

The preparation method of the uniform composite powder of dual-scale silicon carbide and aluminum powder of the present invention is a powder mixing method in which nano-SiCp and micro-SiCp dual-scale silicon carbide with a total volume content of no more than 50% are uniformly dispersed in aluminum powder, and nano-SiCp is used The adsorption effect makes it into a slurry with aluminum powder and mixes it with ball milling. Using the hardness difference and activity of the two to make nano-SiCp and aluminum powder form a mechanical bond during the high-energy ball milling process of aluminum powder, and then add pre-mixed micron SiCp or micron The mixed powder of SiCp and aluminum powder is mechanically mixed to achieve the uniform mixing of dual-scale SiCp and aluminum powder. The preparation method of the composite powder of the present invention does not add a binder and can uniformly mix the dual-scale SiCp and aluminum powder, and there will be no secondary agglomeration or delamination during the subsequent use of the composite powder, and the preparation method of the composite powder is simple Effective, safe and environmentally friendly.

Description

Preparation method of uniform composite powder of double-scale silicon carbide and aluminum powder

technical field

The invention belongs to the technical field of forming metal matrix composite materials, and in particular relates to a method for preparing a uniform composite powder of double-scale silicon carbide and aluminum powder.

Background technique

Silicon carbide SiCp reinforced aluminum matrix composites are widely used in aerospace, electronic packaging, automobiles, military and other fields due to their high specific strength, high specific modulus, high temperature resistance, excellent wear resistance, low thermal expansion coefficient, and good dimensional stability. have a broad vision of application. Powder metallurgy is the most widely used and most competitive material forming method for the preparation of silicon carbide reinforced aluminum matrix composites. In order to improve the toughness and modulus of aluminum matrix composites, nanoscale and microscale SiCp are usually selected to reinforce the aluminum matrix. However, when dual-scale SiCp and aluminum powder are mixed, nanoscale SiCp itself is easy to agglomerate and difficult to disperse. How to make nano-SiCp, micro-SiCp, and aluminum powder uniformly disperse is the key to the preparation of aluminum matrix composites with excellent comprehensive properties. At present, powder metallurgy powder mixing methods generally include ordinary dry mixing, ball milling and wet mixing. When the three mixing methods mix dual-scale SiCp and aluminum powder composite powder, ordinary dry mixing and wet mixing are prone to a large number of agglomeration and delamination. , and in order to prevent the stratification of the components caused by the difference in specific gravity between the mixed materials, the mixed powder is generally processed by adding a binder during ball milling, and the powder pre-pressing treatment is performed after the powder mixing is completed. It is generally required that the pre-compact density is 70% to 80% of the composite material density, which is conducive to the escape of volatile gases such as binders in the degassing stage, but is very unfavorable to the density of the composite material after sintering. This is also the case when mixing powders. Adverse effects caused by adding various binders.

The binders used in the powder metallurgy method include copolymers of ethylene and propylene as monomers, epoxy resins that are liquid at room temperature, and at least one curing agent that uses amino and carboxyl functional groups (based on toluene and acetone) as a solvent). These binders have high boiling points and are easy to remain. When the composite powder is heated to the solid-liquid two-phase region in the subsequent powder metallurgy sintering process, the product is prone to bubbles and cracks, which seriously affects the product yield and physical properties of the product, and volatilizes when heated. The gas seriously pollutes the environment. The patent "Preparation Process of High Volume Fraction Silicon Carbide Particle Reinforced Aluminum Matrix Composite Material" (publication number: CN112267039B, publication date: 2022-02-01) discloses the preparation of high volume fraction silicon carbide aluminum matrix composite material by powder metallurgy , use self-made binder to granulate composite material powder, self-made adhesive is organic matter, which will cause low density of material.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder, which has the characteristics of simple process, safety and environmental protection, and high uniformity of powder mixing.

The technical solution of the present invention is a method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder, which is specifically implemented according to the following steps:

Step 1. Weigh the following components by volume percentage: 10% to 50% of dual-scale SiCp, and the balance is aluminum powder; wherein, dual-scale SiCp includes nano-SiCp and micro-SiCp, and the volume of nano-SiCp accounts for 10% of the volume of dual-scale SiCp 1% to 50%, the balance is micron SiCp;

Step 2, adding the nano-SiCp of step 1 into ethanol for ultrasonic dispersion, adding aluminum powder while stirring, and stirring again to obtain slurry A; the volume of added aluminum powder is 50% to 100% of the total aluminum powder in step 1;

Step 3, adding the slurry A obtained in step 2 into a ball mill tank for vacuum ball milling to obtain dry mixed powder B;

Step 4, pretreating the surface of the micron SiCp in step 1 to obtain the pretreated micron SiCp;

Step 5, uniform dispersion of micron SiC: pour the remaining aluminum powder and the pretreated micron SiCp in step 4 into a mixer and mix to obtain mixed powder C;

Step 6. Composite powder vacuum ball milling process: Add the mixed powder C to the ball mill tank in step 3, and carry out a second vacuum ball mill together with the dry mixed powder B. After the tank body cools down to room temperature, sieve out the balls to get The composite powder in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder is a uniform composite powder of dual-scale silicon carbide and aluminum powder.

The present invention is also characterized in that:

In step 1, the nano-SiCp particle size is 50nm-200nm, the micro-SiCp particle size is 30μm-100μm, the aluminum powder particle size is 30μm-80μm, the aluminum powder is pure aluminum powder or aluminum alloy powder, and the volume ratio of aluminum powder to nano-SiCp Not less than 2:1.

In step 2, the time for ultrasonic dispersion is 15 minutes to 20 minutes; the time for re-stirring is 3 minutes to 5 minutes.

In step 2, the volume of ethanol is the sum of the volume of the nano-SiCp and the volume of the added aluminum powder.

In step 3, the ball-to-material ratio of the ball mill is 3:1, the ball milling time is 40 minutes to 60 minutes, the vacuum ball mill tank rotates while turning up and down, and the speed of the ball mill is 200 rpm to 400 rpm.

Every 15 to 20 minutes of ball milling, stop the machine for cooling, and exhaust the ball mill tank during the shutdown process, and re-evacuate the ball mill.

In step 4, the micron SiCp surface pretreatment is specifically: adding the micron SiCp in step 1 to an ethanol solution with a volume fraction of 20% HF acid for ultrasonic vibration, pouring off the supernatant, and obtaining the roughened micron SiCp; Acetone is used to clean the residual HF acid in the roughened micron SiCp; the cleaned micron SiCp is filtered and dried to obtain the pretreated micron SiCp.

The ultrasonic oscillation time is 15min~20min; the volume ratio of micron SiCp and 20% HF acid ethanol solution is 1:1~3; the drying temperature is ≤60℃.

In step 5, the mixing time is 20 minutes to 30 minutes.

In step 6, the rotational speed of the ball mill for the second vacuum ball milling is 30 rpm to 100 rpm, and the milling time is 20 min to 40 min.

The beneficial effects of the present invention are:

(1) The preparation method of the uniform composite powder of dual-scale silicon carbide and aluminum powder of the present invention, the prepared composite powder is suitable for powder metallurgy, after the cold pressing process of the subsequent powder metallurgy, after the aluminum alloy powder cold compacted blank is pre-pressed The density can be increased to more than 90% of the composite material density, the degassing stage of the sintering process is greatly reduced, the process is simple, the environmental pollution is small, and the low-cost preparation of high-density and high-performance SiCp/Al-based composite materials Provide uniform, low-cost composite powder foundation;

(2) The preparation method of the homogeneous composite powder of double-scale silicon carbide and aluminum powder of the present invention can also mix double-scale SiCp and aluminum matrix powder evenly without adding a binder in the powder mixing process, and is suitable for nano-SiCp not exceeding the total A homogeneous dispersion system of nano-SiCp, micro-SiCp and aluminum powder with a SiCp content of 50%.

(3) The homogeneous composite powder preparation method of dual-scale silicon carbide and aluminum powder of the present invention, after adding nano-SiCp ultrasonic vibration in ethanol, agglomeration size is less, is easy to be adsorbed on the surface of aluminum powder, the semi-dry state nano-SiCp of formation and The aluminum powder mixed slurry can prevent the precipitation and delamination of nano-SiCp; the slurry is not dried or sieved before ball milling, which well maintains the uniform mixing effect of nano-SiCp and aluminum powder before ball milling;

(4) The preparation method of the homogeneous composite powder of dual-scale silicon carbide and aluminum powder of the present invention, nano-SiCp disperses effect well in micron aluminum powder, and bonding strength is higher, adopts ethanol to disperse nano-SiCp earlier, utilizes nano-SiCp bigger Chemical activity and surface energy have an adsorption effect with aluminum powder; and then use high-energy ball milling to increase the surface activity of aluminum powder, making stronger adsorption between ball-milled nano-SiCp and aluminum powder, thus uniformly distributing and utilizing nano-SiCp and Al during the ball milling process The powder has poor hardness and size, and under the activation of high-energy ball milling, it produces a stable mutual coating/wrapping effect, forming a good mechanical bond, and there will be no secondary agglomeration or delamination in the subsequent use of composite powder. ;

(5) The preparation method of the homogeneous composite powder of dual-scale silicon carbide and aluminum powder of the present invention, nano-SiCp is more evenly dispersed in the micro-SiCp and micron-aluminum powder system, and the nano-scale SiCp is first evenly dispersed in the micron-scale aluminum powder Form a slurry, and then vacuum ball milling to solidify nano-SiCp, then add micro-SiCp or micro-SiCp and aluminum powder for mixing to eliminate the uneven mixing caused by stratification and agglomeration in the ordinary dry ball milling process of nano- and micro-SiCp, for It provides an effective way to improve the microstructure homogeneity of dual-scale SiCp reinforced aluminum matrix composites.

Description of drawings

Fig. 1 is the process flow sheet of the uniform composite powder preparation method of dual-scale silicon carbide and aluminum powder of the present invention;

Fig. 2 is a schematic diagram of the mechanical combination of aluminum powder and nano-SiCp in the preparation method of the uniform composite powder of dual-scale silicon carbide and aluminum powder.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

The preparation method of the uniform composite powder of dual-scale silicon carbide and aluminum powder of the present invention uniformly disperses nano-SiCp into micro-SiCp and aluminum powder. The process flow is shown in Figure 1, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: 10% to 50% of dual-scale SiCp, and the balance is aluminum powder; wherein, dual-scale SiCp includes nano-SiCp with a particle size of 50nm to 200nm and a particle size of 30 μm to 100μm micro-SiCp, nano-SiCp volume accounts for 1% to 50% of the double-scale SiCp volume, and the balance is micro-SiCp; the volume ratio of aluminum powder to nano-SiCp is not less than 2:1; the aluminum powder has a particle size of 30μm-80μm Pure aluminum powder or aluminum alloy powder.

Usually micro-SiCp can improve the modulus and strength of the matrix, but at the expense of the plasticity of the matrix, and the increase in the high-temperature strength of the matrix is not significant. Compared with micro-SiCp, nano-SiCp can significantly improve the strength of the matrix while maintaining good plasticity, and the high-temperature performance of the matrix is also significantly improved by nano-SiCp. Although nano-SiCp-reinforced Al-matrix composites have high strength, toughness and high-temperature performance, it is difficult to prepare nano-SiCp-reinforced Al-matrix composites with a high volume fraction, which limits the improvement of the modulus of nano-SiCp-reinforced Al-matrix composites. Therefore, the volume of nano-SiCp accounts for 1% to 50% of the volume of dual-scale SiCp, and the content of micro-SiCp in aluminum matrix composites reinforced by micro-nano dual-scale SiCp is greater than that of nano-SiCp, which is beneficial to improve the wear resistance and elastic modulus of composite materials. while maintaining overall performance.

The volume content of dual-scale SiCpSiCp in the composite powder is 10% to 50%. It is a SiCp-reinforced aluminum-based composite material with high specific strength, high specific modulus, high temperature resistance, and excellent wear resistance. The SiCp content is not less than 10%. , the SiCp content in the composite material with higher modulus and dimensional stability is higher than 50%, and the melt infiltration method is more advantageous.

Choose pure aluminum powder or aluminum alloy powder with a particle size of 30 μm to 80 μm for the aluminum powder, which can avoid the difficulty of mixing evenly if the size is too small, and at the same time avoid the excessive size of the sheet after ball milling, which will affect the cold-pressed density of the composite powder; The size of aluminum powder and micron SiCp is kept at the same level, and it is easy to mix with micron SiCp evenly and mechanically. It is not difficult to sieve the 30-80 μm aluminum powder in the powder making process, and it is easy to control and reduce the dispersion of the particle size distribution of the aluminum powder at this size. The price/performance ratio of the commercially available aluminum powder is relatively high.

Step 2. Add the nano-SiCp in step 1 into ethanol and ultrasonically disperse for 15-20 minutes, add aluminum powder while stirring, and stir again for 3-5 minutes to obtain slurry A; control slurry A so that it is not too wet, that is, after mixing There is no excess ethanol in the slurry. If there is excess ethanol, filter paper can be used to absorb the excess to fix the nano-SiCp in the ball mill slurry.

The volume of ethanol is the sum of the volume of the nano-SiCp and the volume of the added aluminum powder.

The volume of the added aluminum powder is 50% to 100% of the total aluminum powder in step 1, and the remaining aluminum powder is used for later use. Try to add most of the aluminum powder in step 2, which is beneficial to disperse and combine the nano-SiCp with the aluminum powder.

After adding nano-SiCp to ethanol and ultrasonically vibrating, the agglomeration size is small, and it is easy to adsorb on the surface of aluminum powder. The mixed slurry of nano-SiCp and aluminum powder in a semi-dry state can prevent the precipitation and delamination of nano-SiCp; the use of nano-SiCp and aluminum powder The difference in hardness and the increased activity of aluminum powder during high-energy ball milling make nano-SiCp and aluminum powder form a stable mechanical bond.

Slurry A is not dried or sieved before ball milling, which well maintains the uniform mixing effect of nano-SiCp and aluminum powder before ball milling.

In step 2, using the weak acidity of nano-SiCp in ethanol and the weak alkalinity of aluminum powder to form a slight reaction, it is adsorbed around the aluminum powder particles without precipitation and stratification; using ethanol as a temporary medium in the ball milling process, ball milling The ethanol will volatilize during the process to prevent the cold welding effect of the aluminum powder high-energy ball milling process, so as to achieve the mechanical combination of nano-SiCp and the added aluminum powder without serious cold welding of the aluminum powder. The mechanical combination of aluminum powder and nano-SiCp is shown in Figure 2;

Step 3. Add the slurry A obtained in step 2 into a vacuum ball milling tank for vacuum ball milling. The vacuum ball milling tank rotates while turning up and down. The ball-to-material ratio is 3:1, and the ball milling time is 40-60 minutes to obtain dry mixed powder B. .

During the ball milling process, the ball mill should be stopped every 15-20 minutes to cool down to prevent the temperature of the ball mill tank from being too high; during the shutdown process, the spherical tank should be exhausted and vacuumized again, in order to delay the volatilization of ethanol as a temporary ball mill medium.

During the ball milling process, the speed of the ball mill is 200rpm-400rpm, which can provide suitable kinetic energy for mechanically combining nano-SiCp with aluminum powder and properly deforming the aluminum powder. Increased process density.

Step 4, carry out surface pretreatment to the micron SiCp of step 1, be specifically: the micron SiCp in step 1 is joined in the ethanol solution that volume fraction is 20% HF acid, the volume of the ethanol solution of micron SiCp and 20% HF acid Ratio of 1:1~3, ultrasonic vibration for 15min~20min, remove the oxide film and metal particles that may exist on the surface of micron SiCp, and increase surface activity; pour off the supernatant to obtain roughened micron SiCp; then use acetone to Clean the residual HF acid in the treated micro-SiCp; filter and dry at a temperature not higher than 60°C to obtain the pre-treated micro-SiCp.

Step 5, evenly dispersing the micron SiCp: pour the remaining aluminum powder and the pretreated micron SiCp in step 4 into the mixer and mix for 20-30 min to obtain the mixed powder C;

The aluminum powder in step 5 is used for the deployment ratio, and the addition ratio is determined according to the needs of the SiCp content in the final composite powder, but not more than the amount of aluminum powder added in step 2. If the volume of the remaining aluminum powder is greater than 0%, Pour the pretreated micron SiCp and the remaining aluminum powder into the mixer and mix for 20-30 minutes to obtain the mixed powder C; if the volume of the aluminum powder added in step 2 is 100% of the total aluminum powder, the volume of the remaining aluminum powder is 0% , then only the pretreated micron SiCp is mixed separately in a mixer for 20 minutes to 30 minutes to obtain mixed powder C.

Step 6. Composite powder vacuum ball milling process: Add the mixed powder C to the ball mill tank in step 3, and perform a second vacuum ball mill together with the dry mixed powder B, and mechanically mix the semi-dry ball grinding material and the micron SiCp mixed powder, It can achieve a better homogeneous powder mixing effect. The ball mill speed is 30rpm-100rpm, and the ball milling time is 20min-40min. After the tank cools down to room temperature, sieve out the balls to get nano-SiCp and micro-SiCp uniformly dispersed in aluminum powder The composite powder is a uniform composite powder of dual-scale silicon carbide and aluminum powder.

The uniformity of the composite powder is evaluated by the method of natural bulk equal volume average density. Three or more samples are randomly selected from the composite powder, and the bulk density of each sample is measured. The difference of the absolute value of the difference of the effective bulk density tends to 0, indicating that the mixing uniformity of the composite powder is higher.

The composite powder prepared by the invention can be added into a metal mold for cold compacting, and is prepared for cold compacting for the preparation of silicon carbide aluminum matrix composite materials by powder metallurgy.

The method for preparing the uniform composite powder of dual-scale silicon carbide and aluminum powder of the present invention uniformly disperses nano-SiCp and micro-SiCp dual-scale silicon carbide with a total volume content not exceeding 50% in the aluminum powder. Use the adsorption of nano-SiCp to make it into a slurry and mix it with aluminum powder, and then use the hardness difference and interfacial activity of the two to form a mechanical bond with the aluminum powder during the high-energy ball milling process to solidify the adsorption effect; then The cured nano-SiCp is mechanically mixed with the mixed powder of micro-SiCp and aluminum powder or micro-SiCp, and then the simple and effective uniform mixing of dual-scale SiCp and aluminum powder is achieved. The two-step mixing method solves the problem that the existing nano- and micron-scale SiCp and aluminum powder are not easy to mix uniformly, and solves the adverse effects of adding binders during ordinary powder mixing on the subsequent cold pressing and thermoforming processes.

The characteristics of the preparation method of the homogeneous composite powder of dual-scale silicon carbide and aluminum powder of the present invention are: firstly, ethanol is used to disperse nano-SiCp; SiCp is uniformly dispersed in the micron aluminum powder to form a slurry, and then the surface activity of the aluminum powder is increased by high-energy ball milling, so that a stronger adsorption effect occurs between the ball-milled nano-SiCp and the aluminum powder, so that it is evenly distributed during the ball-milling process and the use of nano-SiCp and aluminum powder Al powder has poor hardness and poor size. Under the activation of high-energy ball milling, it produces a stable mutual coating/wrapping effect, forming a good mechanical bond, and there will be no secondary agglomeration or separation in the subsequent use of the composite powder. Nano-SiCp has a good dispersion effect in micron aluminum powder, and the bonding strength is high; after curing nano-SiCp, add micron-sized SiCp or a mixture of nano-SiCp and aluminum powder for mixing, eliminating the need for nano- and micron-sized SiC in the ordinary dry ball milling process. The uneven mixing caused by delamination and agglomeration improves the microstructure uniformity of the dual-scale SiCp reinforced aluminum matrix composite; no binder is used in the preparation process, and the aluminum alloy powder is cold pressed in the subsequent powder metallurgy cold pressing process After pre-pressing, the density can be increased to more than 90% of the composite material density, the degassing stage of the sintering process is greatly reduced, the process is simple, and the environmental pollution is small. Low-cost preparation provides a uniform, low-cost composite powder base.

Example 1:

A method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder, the volume content of dual-scale SiCp is 10%, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: the volume of 50nm nano-SiCp: the volume of 50μm micro-SiCp: the volume ratio of 60μm aluminum powder is 1:1:18, the total volume of dual-scale SiCp accounts for the composite powder 10% of volume;

Step 2. Add 1 part of 50nm nano-SiCp to 10 parts of ethanol for ultrasonic dispersion for 15 minutes, then add 9 parts of aluminum powder and stir for 5 minutes to obtain slurry A1;

Step 3. Put the slurry A1 into a ball mill tank for vacuum ball milling, the ball-to-material ratio is 3:1, the ball mill speed is 300rpm, and the ball milling time is 40min to obtain dry mixed powder B1;

Step 4. Add 50 μm micro-SiCp into the ethanol solution with a volume fraction of 20% HF acid and ultrasonically shake for 15 minutes. The volume ratio of micro-SiCp and 20% HF acid ethanol solution is 1:2; pour off the supernatant, and use Acetone washed the micro-SiCp after the supernatant was discarded, filtered and dried at 60°C to obtain the micro-SiCp after micro-treatment;

Step 5. Pour the micron-treated SiCp and the remaining 9 parts of aluminum powder into the mixer and mix for 20 minutes to obtain the mixed powder C1;

Step 6. Weigh the mixed powder C1 and add it to the ball milling tank in step 3 to conduct a second vacuum ball mill together with the dry mixed powder B1. The speed of the ball mill is 50 rpm, and the milling time is 20 minutes. Sift out the grinding balls at room temperature to obtain a composite powder 1 in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder.

The uniformity of the composite powder is evaluated by the natural bulk equal volume average density method, and 3 samples are randomly selected from the composite powder 1, and the natural bulk density of the 3 samples is measured, and the natural bulk density and the equivalent bulk density are calculated. The absolute value of the density difference.

Example 2:

A method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder, the volume content of dual-scale SiCp is 30%, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: the volume ratio of 50nm nano-SiCp, 65μm micro-SiCp, and 60μm aluminum powder is 1:2:7;

Step 2. Add 1 part of nano-SiCp above to 5 parts of ethanol for ultrasonic dispersion for 15 minutes, add 4 parts of 60 μm aluminum powder and stir for 5 minutes to obtain slurry A2.

Step 3. Put the slurry A2 into a ball mill tank for vacuum ball milling, the ball-to-material ratio is 3:1, the ball mill speed is 300rpm, and the ball milling time is 40min to obtain dry mixed powder B2.

Step 4. Add 2 parts of 65 μm micro-SiCp to the ethanol solution with a volume fraction of 20% HF acid and ultrasonically shake for 15 minutes. The volume ratio of micro-SiCp and 20% HF acid ethanol solution is 1:3; Acetone was used to clean the roughened micro-SiCp; it was filtered and dried at 60°C.

Step 5. Pour the micron SiCp obtained in the previous step and the remaining 3 parts of aluminum powder into a mixer and mix for 20 minutes to obtain mixed powder C2.

Step 6. Add the mixed powder C2 to the ball mill tank in step 3 and perform a second vacuum ball mill together with the dry mixed powder B1. The speed of the ball mill is 50 rpm, and the milling time is 20 minutes. When the temperature of the tank reaches room temperature, the balls are sieved out to obtain a composite powder 2 in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder.

The uniformity of the composite powder is evaluated by the method of natural bulk equal volume average density, and 3 samples are randomly selected from the composite powder 2, and the natural bulk density of the 3 samples is measured, and the natural bulk density and the equivalent bulk density are calculated. The absolute value of the density difference.

Example 3:

A method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder, the volume content of dual-scale SiCp is 50%, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: 50nm nano-SiCp, 50μm micro-SiCp, 60μm aluminum powder, the volume ratio is 1:5:6;

Step 2. Add 1 part of 50nm nano-SiCp above to 4 parts of ethanol for ultrasonic dispersion for 15 minutes, add 3 parts of aluminum powder and stir for 5 minutes to obtain slurry A3.

Step 3. Put the slurry A3 into a ball mill tank for vacuum ball milling, the ball-to-material ratio is 3:1, the ball mill speed is 300rpm, and the ball milling time is 40min to obtain dry mixed powder B3.

Step 4. Add 50 μm micro-SiCp into the ethanol solution with a volume fraction of 20% HF acid and ultrasonically shake for 15 minutes. The volume ratio of micro-SiCp and 20% HF acid ethanol solution is 1:2; The roughened micron SiCp is cleaned; filtered and then dried at 60° C. to obtain the micron SiCp after microtreatment.

Step 5. Pour the micron SiCp after the micro-treatment in step 4 and the remaining 3 parts of aluminum powder into a mixer and mix for 30 minutes to obtain mixed powder C3.

Step 6. Add the mixed powder C3 into the ball mill tank in the same proportion as the mixed powder B3, and vacuum ball mill together with the dry mixed powder B3. The speed of the ball mill is 50 rpm, and the milling time is 40 minutes. Sift the balls out of the ball mill at room temperature to obtain a composite powder 3 in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder.

The uniformity of the composite powder is evaluated by the method of natural bulk equal volume average density, and 3 samples are randomly selected from the composite powder 3, and the natural bulk density of the 3 samples is measured, and the natural bulk density and the equivalent bulk density are calculated. The absolute value of the density difference.

Example 4:

A method for preparing a homogeneous composite powder of dual-scale silicon carbide and aluminum powder, the volume content of dual-scale SiCp is 40%, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: 100nm nano-SiCp, 30μm micro-SiCp, 30μm aluminum powder, the volume ratio is 1:3:6;

Step 2. Add 1 part of nano-SiCp above to 4 parts of ethanol for ultrasonic dispersion for 20 minutes, add 3 parts of aluminum powder and stir for 4 minutes to obtain slurry A4.

Step 3. Put the slurry A4 into a ball mill tank for vacuum ball milling, the ball-to-material ratio is 3:1, the ball mill speed is 200rpm, and the ball milling time is 60min to obtain dry mixed powder B4.

Step 4. Add the micron SiCp in step 1 to an ethanol solution with a volume fraction of 20% HF acid and ultrasonically shake for 18 minutes. The volume ratio of the micron SiCp and 20% HF acid ethanol solution is 1:1; pour off the supernatant and use Acetone was used to wash the roughened micro-SiCp; after filtration, it was dried at 50° C. to obtain the micro-SiCp after micro-treatment.

Step 5. Pour the micron SiCp after the micro-treatment in step 4 and the remaining 3 parts of aluminum powder into a mixer and mix for 25 minutes to obtain mixed powder C4.

Step 6. Add the mixed powder C4 into the ball mill tank, and vacuum ball mill together with the dry mixed powder B4, the speed of the ball mill is 30rpm, and the milling time is 30min. Sift the balls out of the ball mill tank at room temperature to obtain a composite powder 4 in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder.

Example 5:

A method for preparing a homogeneous composite powder of dual-scale silicon carbide and aluminum powder, the volume content of dual-scale SiCp is 20%, and the specific steps are as follows:

Step 1. Weigh the following components by volume percentage: the volume ratio of 200nm nano-SiCp, 100μm micron-SiCp, and 80μm aluminum powder is 1:7:32;

Step 2. Add 1 part of nano-SiCp in step 1 to 21 parts of ethanol for ultrasonic dispersion for 15 minutes, add 20 parts of aluminum powder and stir for 3 minutes to obtain slurry A5.

Step 3. Put the slurry A5 into a ball mill tank for vacuum ball milling, the ball-to-material ratio is 3:1, the ball mill speed is 400rpm, and the ball milling time is 40min to obtain dry mixed powder B5.

Step 4. Add the micron SiCp in step 1 to the ethanol solution with a volume fraction of 20% HF acid and ultrasonically shake for 20 minutes. The volume ratio of the micron SiCp and 20% HF acid ethanol solution is 1:1; pour off the supernatant , wash the roughened micro-SiCp with acetone; filter and dry at 60° C. to obtain the micro-processed micro-SiCp.

Step 5. Pour the micron SiCp after the micro-treatment in step 4 and the remaining 12 parts of aluminum powder into a mixer and mix for 30 minutes to obtain mixed powder C5.

Step 6. Add the mixed powder C5 into the ball mill tank, and conduct a second vacuum ball mill together with the dry mixed powder B5. The speed of the ball mill is 100 rpm, and the milling time is 40 minutes. Sift the balls out of the ball mill tank at room temperature to obtain a composite powder 5 in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder.

For the composite powder samples obtained in Examples 1-3, the equivalent judgment of uniformity was carried out by using the natural loose packed equal volume average density method. Firstly, the packing model after uniform powder mixing is established. Assuming that the nano-SiCp in the composite powder only occupies the gap between the micro-SiCp and the micro-sized aluminum powder, the equivalent natural bulk density ρ of the mixed powder in the simplified model is three powders The weight of the body and the mixed volume of micron SiCp and aluminum powder, the calculation of the quotient is as follows:

In the formula: ρ is the equivalent natural bulk density in the system, x is the volume percentage of nano-SiCp added to the composite powder, y is the volume percentage of micro-SiCp added to the composite powder, and z is the volume percentage of aluminum powder added to the composite powder; Mx is the mass of nano-SiCp added, My is the mass of micro-SiCp added, Mz is the mass of aluminum powder added; C is the mixing volume coefficient related to the average particle size ratio of micro-SiCp and micron aluminum powder. Secondly, the equivalent natural bulk density ρ of the composite powder is calculated separately, and the absolute value of the difference between the natural bulk density ρ _i measured after the composite powder is mixed and the equivalent natural bulk density ρ is compared in pairs, as Formula (2), the result tends to 0, indicating that the mixing effect is more uniform.

|ρ _i -|-|ρ _in -|≈0(2)

In the results of Examples 1-3, the difference between the absolute value of the difference between the natural bulk density ρ _i and the equivalent natural bulk density ρ of the three samples in the three groups of composite powders basically tends to 0, and it can be known that the three groups of different volumes In the composite powder with SiCp content, the dual-scale SiCp is relatively uniformly distributed in the aluminum powder.

Claims (10)

1. The preparation method of the uniform composite powder of dual-scale silicon carbide and aluminum powder is implemented according to the following steps: Step 1. Weigh the following components by volume percentage: 10% to 50% of dual-scale SiCp, and the balance is aluminum powder; wherein, the dual-scale SiCp includes nano-SiCp and micro-SiCp, and the volume of nano-SiCp accounts for all 1% to 50% of the volume of the dual-scale SiCp, and the balance is the micron SiCp; Step 2, adding the nano-SiCp in step 1 into ethanol for ultrasonic dispersion, adding aluminum powder while stirring, and stirring again to obtain slurry A; the volume of the added aluminum powder is 50% to 100% of the total aluminum powder in step 1; Step 3, adding the slurry A obtained in step 2 into a ball mill tank for vacuum ball milling to obtain dry mixed powder B; Step 4, pretreating the surface of the micron SiCp in step 1 to obtain the pretreated micron SiCp; Step 5, uniform dispersion of micron SiC: pour the remaining aluminum powder and the pretreated micron SiCp in step 4 into a mixer and mix to obtain mixed powder C; Step 6. Composite powder vacuum ball milling process: Add the mixed powder C to the ball mill tank in step 3, and carry out a second vacuum ball mill together with the dry mixed powder B. After the tank cools down to room temperature, sieve out the balls That is, a composite powder in which nano-SiCp and micro-SiCp are uniformly dispersed in aluminum powder is obtained, that is, a uniform composite powder of dual-scale silicon carbide and aluminum powder. 2. The method for preparing a homogeneous composite powder of dual-scale silicon carbide and aluminum powder according to claim 1, characterized in that, in step 1, the particle size of the nano-SiCp is 50 nm to 200 nm, and the particle size of the micro-SiCp is 30 μm ~100 μm, the particle size of the aluminum powder is 30 μm-80 μm, the aluminum powder is pure aluminum powder or aluminum alloy powder, and the volume ratio of the aluminum powder to the nano-SiCp is not less than 2:1. 3. The method for preparing a homogeneous composite powder of dual-scale silicon carbide and aluminum powder according to claim 1, wherein in step 2, the ultrasonic dispersion time is 15 min to 20 min; the re-stirring time is 3 min to 5 min . 4. according to the preparation method of the homogeneous composite powder of double-scale silicon carbide and aluminum powder described in claim 1, it is characterized in that, in step 2, the volume of described ethanol is the volume of described nano-SiCp and described adding aluminum powder sum of volumes. 5. The method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder according to claim 1, characterized in that, in step 3, the ball-to-material ratio of the ball mill is 3:1, and the ball milling time is 40 minutes to 60 minutes; The vacuum ball mill tank rotates while turning up and down, and the speed of the ball mill is 200rpm-400rpm. 6. The method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder according to claim 5, characterized in that the ball mill is shut down for cooling every 15-20 minutes, and the ball mill tank is exhausted and vacuumized again during the shutdown process. 7. The method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder according to claim 1, characterized in that, in step 4, the micron SiCp surface pretreatment is specifically: adding the micron SiCp in step 1 to Ultrasonic oscillation in an ethanol solution with a volume fraction of 20% HF acid, discard the supernatant, and obtain the roughened micron SiCp; then use acetone to clean the residual HF acid in the roughened micron SiCp; The micron SiCp is filtered and dried to obtain the pretreated micron SiCp. 8. according to the method for preparing the homogeneous composite powder of double-scale silicon carbide and aluminum powder described in claim 7, it is characterized in that, described ultrasonic vibration time is 15min～20min; The ethanol of described micron SiCp and described 20%HF acid The volume ratio of the solution is 1:1-3; the drying temperature is ≤60°C. 9 . The method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder according to claim 1 , characterized in that, in the step 5, the mixing time is 20 minutes to 30 minutes. 10. The method for preparing a uniform composite powder of dual-scale silicon carbide and aluminum powder according to claim 1, characterized in that, in step 6, the ball mill speed of the secondary vacuum ball mill is 30 rpm to 100 rpm, and the milling time is 20 min to 100 rpm. 40min.

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