CN104232961A - High-strength high-hardness Cu-Cr composite material as well as preparation method and application thereof - Google Patents

Abstract

The invention belongs to the technical field of metal matrix composite material preparation, and discloses a high-strength and high-hardness Cu-Cr composite material, a preparation method and application thereof. The preparation method comprises the following steps: Cu powder and Cr powder are used as raw materials, one of the raw materials is placed in a high-energy planetary ball mill for pre-ball milling, and another raw material and a grinding aid are added for mixed ball milling, and the powder after ball milling is After the body is dried, it is sintered and densified in a spark plasma sintering furnace to obtain a high-strength and high-hardness Cu-Cr composite material. In the present invention, the high-strength and high-hardness Cu-Cr composite material with high powder extraction rate is obtained with a relatively low addition amount of reinforcing phase (Cr content can be as low as 8at.%), and its mechanical properties are excellent, the hardness reaches 250-330Hv, and the compressive yield strength It can reach 900-1000MPa, while maintaining good plasticity, and the compressibility can reach 8-25%. It has broad application prospects in the field of structures.

Description

A kind of high-strength and high-hardness Cu-Cr composite material and its preparation method and application

technical field

The invention belongs to the technical field of metal matrix composite material preparation, and in particular relates to a high-strength and high-hardness Cu-Cr composite material and a preparation method and application thereof.

Background technique

Compared with corresponding metal matrix materials, metal matrix composites have higher mechanical properties while maintaining certain plasticity, so they can be widely used as structural materials in friction and wear, plastic forming processing and other structural fields. In recent years, researchers have carried out a lot of research on adding strengthening phases to prepare metal matrix composites to improve the mechanical properties of metal materials. Among them, the added reinforcement phases include simple materials, carbides, oxides, borides, and mixtures of different types of reinforcement phases. The preparation methods used include powder metallurgy, squeeze casting, rapid solidification, arc melting, and liquid metal infiltration. and laser processing.

In order to obtain higher mechanical properties, some measures are usually taken when preparing metal matrix composites, such as adding a nanoscale reinforcing phase (size less than 100nm), and adding a higher content of reinforcing phase (volume fraction greater than 10%) (ChaS.I., KimK.T., ArshadS.N., MoC.B., HongS.H., Advanced Materials, 2005, 17(11), 1377-1381.) (DaoushW.M., LimB.K ., MoC.B., NamD.H., HongS.H., Materials Science and Engineering: A, 2009, 513-514, 247-253.). The nano-reinforced phase has high strengthening efficiency, but its preparation cost is high, which is not conducive to large-scale industrial production. Adding a higher content of reinforcing phase will not only increase the production cost, but also deteriorate the plasticity and other physical properties of the material. Therefore, choosing economical and practical raw materials, adding a small amount of reinforcement, and using a simple and efficient method to prepare metal matrix composites with excellent mechanical properties, large-scale production and effective application in real life are the problems that the present invention aims to solve. .

Contents of the invention

In order to overcome the shortcomings and deficiencies of the above-mentioned prior art, the primary purpose of the present invention is to provide a method for preparing a high-strength and high-hardness Cu-Cr composite material, which is easy to implement and suitable for industrial scale production.

Another object of the present invention is to provide the high-strength and high-hardness Cu-Cr composite material prepared by the above method. The resulting Cu-Cr composites exhibit excellent mechanical properties while maintaining high plasticity.

Another object of the present invention is to provide the application of the above-mentioned high-strength and high-hardness Cu-Cr composite material in the structural field.

The object of the present invention is achieved through the following solutions:

A method for preparing a high-strength and high-hardness Cu-Cr composite material, comprising the following steps: Cu powder and Cr powder are used as raw materials, one of the raw materials is placed in a high-energy planetary ball mill for pre-milling treatment, and then another raw material and The grinding aid is mixed and ball-milled, and after the ball-milling, the powder is dried and then sintered and densified in a discharge plasma sintering furnace to obtain a high-strength and high-hardness Cu-Cr composite material.

In the raw materials, the content of Cr is 8-10 atomic percent of the total amount, preferably 8 at.%. In the present invention, it is only necessary to add as low as 8 at.% Cr as a reinforcing phase to obtain a composite material with high strength and high hardness and excellent mechanical properties, and because the content of the added reinforcing phase is low, the good toughness of the composite material can be maintained, so that The obtained composite materials can be more widely used in many fields.

Described grinding aid is preferably dehydrated alcohol. The amount of the grinding aid used is 70-90% of the mass of the raw material.

Preferably, when Cu powder is selected for pre-ball milling treatment, a grinding aid is added for ball milling together. It is preferable to add a grinding aid with a mass of 70-90% of Cu powder, more preferably 80 wt%, and after pre-ball milling, dry to remove the grinding aid before subsequent treatment.

The time for the pre-milling treatment is preferably 15-25 hours.

The mixing and ball milling treatment time is preferably 90-110 hours.

Preferably, the diameters of the balls used in the ball milling in the above preparation method are 15, 10 and 6mm respectively, the corresponding mass ratio is 1:3:1, the ball-to-material ratio is 10:1, and the speed of the ball mill is 226rpm. The used ball mill jars and balls are preferably made of stainless steel. The process parameters of the pre-ball milling treatment and the mixed ball milling treatment in the present invention are the same as above.

Preferably, the process conditions of the sintering densification treatment are sintering pressure of 30-40 MPa, sintering temperature of 650-800° C., and holding time of 6-10 minutes.

In the process of the above-mentioned preparation method of the present invention, the drying is preferably carried out in a vacuum oven at a temperature of 50-60° C. for 20-30 hours.

Preferably, the powder after the pre-ball milling treatment can be dried first and then put into the ball mill for subsequent treatment with other materials.

In order to better realize the present invention, the purity of the used raw materials Cu powder and Cr powder is not less than 99%, and the particle size of the powder is not more than 75 μm.

In order to better realize the present invention, the ball milling process is preferably carried out under an inert gas atmosphere, more preferably under an argon atmosphere.

Specifically, the preparation method of the high-strength and high-hardness Cu-Cr composite material of the present invention comprises the following steps:

Method 1: Weigh Cu powder (purity ≥ 99%, powder particle size ≤ 75 μm) and absolute ethanol grinding aid, place it in a high-energy planetary ball mill, pre-ball-mill it for 15-25 hours under the protection of an argon atmosphere, and dry it with Cr Powder (purity ≥ 99%, powder particle size ≤ 75 μm) and anhydrous ethanol grinding aid are mixed, added to a high-energy planetary ball mill, and mixed and ball-milled for 90-110 hours under the protection of an argon atmosphere to obtain a composite powder. After drying, the The sintering and densification treatment is carried out in a spark plasma sintering furnace to obtain a high-strength and high-hardness Cu-Cr composite material.

Among them, the materials of the ball mill jar and the balls are all stainless steel, the diameters of the balls used are 15, 10 and 6mm respectively, the corresponding mass ratio is 1:3:1, the ball-to-material ratio is 10:1, the speed of the ball mill is 226rpm, absolute ethanol The mass is 70-90% of the mass of the powder, and the atomic percentage of Cr powder in the mixed powder is 8%. The drying is all dried in a vacuum drying oven at a temperature of 50-60°C for 20-30h, and the sintering pressure is 30 ～40MPa, the sintering temperature is 650～800℃, and the holding time is 6～10min.

Method 2: Weigh Cr powder (purity ≥ 99%, powder particle size ≤ 75 μm) and place it in a high-energy planetary ball mill, pre-ball-mill it for 15-25 hours under the protection of an argon atmosphere, and then mix the pre-milled Cr powder with Cu powder ( Purity ≥ 99%, powder particle size ≤ 75μm) and anhydrous ethanol grinding aid are mixed, put into a high-energy planetary ball mill, mixed and ball milled for 90-110 hours under the protection of argon atmosphere, and the composite powder is obtained. The sintering and densification treatment is carried out in the sintering furnace to obtain a high-strength and high-hardness Cu-Cr composite material.

Among them, the materials of the ball mill jar and the balls are all stainless steel, the diameters of the balls used are 15, 10 and 6mm respectively, the corresponding mass ratio is 1:3:1, the ball-to-material ratio is 10:1, the speed of the ball mill is 226rpm, absolute ethanol The mass is 70-90% of the mass of the powder, and the atomic percentage of Cr powder in the mixed powder is 8%. The drying is all dried in a vacuum drying oven at a temperature of 50-60°C for 20-30h, and the sintering pressure is 30 ～40MPa, the sintering temperature is 650～800℃, and the holding time is 6～10min.

The high-strength and high-hardness Cu-Cr composite material prepared by the method of the present invention has high purity and excellent mechanical properties while maintaining high plasticity, and can be widely used as a structural material in friction and wear, plastic forming processing and other structural fields.

The preparation method of the invention can prepare a composite material with a fine dispersion distribution of the reinforcing phase and high purity, and the preparation method of the invention has high raw material utilization rate, simple process, convenient operation and large-scale industrial production.

Mechanism of the present invention is:

The present invention combines pure powder ball milling, mixed powder ball milling and discharge plasma sintering technologies. The inventive method uses low-cost raw materials and combines pure powder pre-ball milling, mixed powder ball milling and discharge plasma sintering technologies to achieve a lower reinforcing phase The addition amount (Cr content can be as low as 8at.%, 8.14vol.%) can obtain a high-strength and high-hardness Cu-Cr composite material with excellent mechanical properties and good plasticity.

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

1. In the preparation process of the method of the present invention, a large amount of absolute ethanol is added as a grinding aid, so that the mixed powder is in a wet grinding state, effectively slowing down the agglomeration and bonding of the powder during the ball milling process, and the degree of pollution to the powder is low , In addition, compared to dry grinding and only adding a small amount of grinding aids, wet grinding can also ensure a high powder extraction rate.

2. The present invention adopts the high-energy ball milling process to prepare the powder. This process makes the powder undergo repeated cold welding and crushing through the repeated collision and grinding action of the ball on the powder, so as to achieve the effects of refinement, uniform mixing and alloying . Use high-energy ball milling to pre-mill one of the raw material powders. The continuous impact of the balls on the powder will increase the density of defects such as dislocations in the powder, and promote the refinement of the grains, and the fine grain size can be obtained. The hardened powder, in the subsequent mixed ball milling, is beneficial to obtain the powder with smaller grain size, and at the same time realize the fine dispersion of the reinforcing phase in the matrix, and finally obtain better mechanical properties. The preparation of powder by high-energy ball milling does not require expensive equipment, the process is simple, the operation is simple, and there is no waste water, waste gas and waste residue during the preparation process, which meets the requirements of environmental protection and energy saving. In addition, due to the use of a well-sealed vacuum tank and the introduction of argon gas for atmosphere protection, it can effectively prevent the oxidation of the powder during the ball milling process, thereby ensuring the quality of the powder.

3. The present invention uses discharge plasma sintering technology to sinter and densify composite powders. This technology uses an electric field formed by an external pulsed strong current to clean the oxides and adsorbed gases on the surface of the powder particles, thereby purifying and activating the material. Under low pressure, high current is used to heat the powder for a short time to sinter and compact, and high-quality sintered body can be prepared at lower temperature and shorter time. The spark plasma sintering process is used for sintering, which is characterized by simple operation, low sintering temperature, fast heating rate, short sintering time, low energy consumption per piece, high density of sintered body and fine grains, which is a near net shape and green Preparation technology.

4. The present invention adopts relatively cheap raw materials to prepare metal matrix composites, which have excellent mechanical properties, with a hardness of 250-330Hv, a compressive yield strength of 900-1000MPa, good plasticity, and a compressibility of 8-25%. Composite materials have broad application prospects in the structural field.

Description of drawings

Fig. 1 is the microstructure of the Cu-Cr composite material obtained in Example 1 of the present invention.

Fig. 2 is the microstructure of the Cu-Cr composite material obtained in Example 2 of the present invention (including a partially enlarged view).

Fig. 3 is the microstructure of the sintered Cu-Cr composite material in the comparative example.

Fig. 4 is the X-ray diffraction pattern of the sample in Example 1 of the present invention.

Fig. 5 is the X-ray diffraction spectrum of the sample in Example 2 of the present invention.

6 is the room temperature compressive stress-strain curves of sintered Cu-Cr composite materials in Examples 1-4 of the present invention and comparative examples, wherein 1-4 correspond to Examples 1-4, and 5 is a comparative example.

Detailed ways

The present invention will be further described in detail below with reference to the examples and drawings, but the implementation of the present invention is not limited thereto.

Example 1

Step 1: Pre-milling Cu powder

Accurately weigh 500g of Cu powder (purity ≥ 99%, powder particle size ≤ 75μm), 400g of absolute ethanol, place in a 4L stainless steel ball mill jar, and add stainless steel grinding balls, the ball-to-material ratio is 10:1, and the diameters of the grinding balls are respectively 15, 10 and 6mm, the corresponding mass ratio is 1:3:1, after the ball mill tank is sealed, vacuumize first, then pass argon, and repeat the operation twice in a row, so that the ball milling process is in an argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then stop temporarily for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 20 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the Cu powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain dry pre-milling Cu powder.

Step 2: Mix and ball mill Cu powder and Cr powder

Accurately weigh 466.8g of pre-milled Cu powder, 33.2g of Cr powder (purity ≥ 99%, powder particle size ≤ 75μm), 400g of absolute ethanol, and place them in a 4L stainless steel ball mill jar, and add stainless steel grinding balls. The ball-to-material ratio is 10 :1, the diameters of the balls are 15, 10 and 6 mm respectively, and the corresponding mass ratio is 1:3:1. After the ball mill pot is sealed, first vacuumize, then pass through argon, and repeat the operation twice continuously, so that the ball mill process is at Argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then temporarily stop for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 100 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the mixed powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain a dry composite powder.

Step 3: Sintering composite powder

Accurately weigh 16.7g of the composite powder and place it in a graphite mold with an inner diameter of 20.4mm. A layer of graphite paper with a thickness of 0.2mm is placed between the powder and the inner wall of the mold to facilitate demoulding. Then put the mold on the graphite insulation ring, and put it in the spark plasma sintering furnace, and start sintering after evacuating for 30 minutes. Set the temperature to rise to 100°C within 3 minutes, then raise the temperature at a rate of 100°C/min to 700°C, then raise the temperature to 750°C within 3 minutes, and keep it at this temperature for 8 minutes, keep the pressure at 30MPa throughout the process, and keep it for 8 minutes Afterwards, the furnace was cooled to room temperature, and the sample was taken out to obtain a high-strength and high-hardness Cu-Cr composite material.

Example 2

Step 1: Pre-milling Cr powder

Accurately weigh 500 g of Cr powder (purity ≥ 99%, powder particle size ≤ 75 μm), place it in a 4L stainless steel ball mill jar, and add stainless steel grinding balls, the ball-to-material ratio is 10:1, and the diameters of the grinding balls are 15, 10 and 6 mm respectively , corresponding to a mass ratio of 1:3:1, after sealing the ball mill tank, first vacuumize, then pass through argon, and repeat the operation twice in a row, so that the ball milling process is in an argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then stop temporarily for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 20 hours. After finishing the ball milling, stop the machine to cool down the ball milling tank to obtain pre-milling Cr powder.

Step 2: Mix and ball mill Cu powder and Cr powder

Accurately weigh 466.8g of Cu powder (purity ≥ 99%, powder particle size ≤ 75μm), pre-ball mill Cr powder 33.2g, absolute ethanol 400g, place in a 4L stainless steel ball mill jar, and add stainless steel balls, the ball-to-material ratio is 10 :1, the diameters of the balls are 15, 10 and 6 mm respectively, and the corresponding mass ratio is 1:3:1. After the ball mill pot is sealed, first vacuumize, then pass through argon, and repeat the operation twice continuously, so that the ball mill process is at Argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then temporarily stop for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 100 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the mixed powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain a dry composite powder.

Step 3: Sintering composite powder

Accurately weigh 16.7g of the composite powder and place it in a graphite mold with an inner diameter of 20.4mm. A layer of graphite paper with a thickness of 0.2mm is placed between the powder and the inner wall of the mold to facilitate demoulding. Then put the mold on the graphite insulation ring, and put it in the spark plasma sintering furnace, and start sintering after evacuating for 30 minutes. Set the temperature to rise to 100°C within 3 minutes, then raise the temperature at a rate of 100°C/min to 700°C, then raise the temperature to 750°C within 3 minutes, and keep it at this temperature for 8 minutes, keeping the pressure at 30MPa throughout the process. After 8 minutes, the furnace was cooled to room temperature, and the sample was taken out to obtain a high-strength and high-hardness Cu-Cr composite material.

Example 3

Step 1: Pre-milling Cr powder

Accurately weigh 500 g of Cr powder (purity ≥ 99%, powder particle size ≤ 75 μm), place it in a 4L stainless steel ball mill jar, and add stainless steel grinding balls, the ball-to-material ratio is 10:1, and the diameters of the grinding balls are 15, 10 and 6 mm respectively , corresponding to a mass ratio of 1:3:1, after sealing the ball mill tank, first vacuumize, then pass through argon, and repeat the operation twice in a row, so that the ball milling process is in an argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then stop temporarily for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 20 hours. After finishing the ball milling, stop the machine to cool down the ball milling tank to obtain pre-milling Cr powder.

Step 2: Mix and ball mill Cu powder and Cr powder

Accurately weigh 466.8g of Cu powder (purity ≥ 99%, powder particle size ≤ 75μm), pre-ball mill Cr powder 33.2g, absolute ethanol 400g, place in a 4L stainless steel ball mill jar, and add stainless steel balls, the ball-to-material ratio is 10 :1, the diameters of the balls are 15, 10 and 6 mm respectively, and the corresponding mass ratio is 1:3:1. After the ball mill pot is sealed, first vacuumize, then pass through argon, and repeat the operation twice continuously, so that the ball mill process is at Argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then temporarily stop for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 100 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the mixed powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain a dry composite powder.

Step 3: Sintering composite powder

Accurately weigh 16.7g of the composite powder and place it in a graphite mold with an inner diameter of 20.4mm. A layer of graphite paper with a thickness of 0.2mm is placed between the powder and the inner wall of the mold to facilitate demoulding. Then put the mold on the graphite insulation ring, and put it in the spark plasma sintering furnace, and start sintering after evacuating for 30 minutes. Set the temperature to rise to 100°C within 3 minutes, then raise the temperature at a rate of 100°C/min to 600°C, then raise the temperature to 650°C within 3 minutes, and keep it at this temperature for 8 minutes, keeping the pressure at 30MPa throughout the process. After 8 minutes, the furnace was cooled to room temperature, and the sample was taken out to obtain a high-strength and high-hardness Cu-Cr composite material.

Example 4

Step 1: Pre-milling Cr powder

Accurately weigh 500 g of Cr powder (purity ≥ 99%, powder particle size ≤ 75 μm), place it in a 4L stainless steel ball mill jar, and add stainless steel grinding balls, the ball-to-material ratio is 10:1, and the diameters of the grinding balls are 15, 10 and 6 mm respectively , corresponding to a mass ratio of 1:3:1, after sealing the ball mill tank, first vacuumize, then pass through argon, and repeat the operation twice in a row, so that the ball milling process is in an argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then stop temporarily for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 20 hours. After finishing the ball milling, stop the machine to cool down the ball milling tank to obtain pre-milling Cr powder.

Step 2: Mix and ball mill Cu powder and Cr powder

Accurately weigh 466.8g of Cu powder (purity ≥ 99%, powder particle size ≤ 75μm), pre-ball mill Cr powder 33.2g, absolute ethanol 400g, place in a 4L stainless steel ball mill jar, and add stainless steel balls, the ball-to-material ratio is 10 :1, the diameters of the balls are 15, 10 and 6 mm respectively, and the corresponding mass ratio is 1:3:1. After the ball mill pot is sealed, first vacuumize, then pass through argon, and repeat the operation twice continuously, so that the ball mill process is at Argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then temporarily stop for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 100 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the mixed powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain a dry composite powder.

Step 3: Sintering composite powder

Accurately weigh 16.7g of the composite powder and place it in a graphite mold with an inner diameter of 20.4mm. A layer of graphite paper with a thickness of 0.2mm is placed between the powder and the inner wall of the mold to facilitate demoulding. Then put the mold on the graphite insulation ring, and put it in the spark plasma sintering furnace, and start sintering after evacuating for 30 minutes. Set the temperature to rise to 60°C within 3 minutes, then raise the temperature at a rate of 100°C/min to 760°C, then raise the temperature to 800°C within 3 minutes, and keep it at this temperature for 8 minutes, keeping the pressure at 40MPa throughout the process. After 8 minutes, the furnace was cooled to room temperature, and the sample was taken out to obtain a high-hardness Cu-Cr composite material.

comparative example

Step 1: Mix and ball mill Cu powder and Cr powder

Accurately weigh 466.8g of Cu powder (purity ≥ 99%, powder particle size ≤ 75 μm), 33.2 g of Cr powder (purity ≥ 99%, powder particle size ≤ 75 μm), 400 g of absolute ethanol, place in a 4L stainless steel ball mill jar, and add Stainless steel grinding balls, the ball-to-material ratio is 10:1, the diameters of the grinding balls are 15, 10 and 6mm respectively, and the corresponding mass ratio is 1:3:1. After the ball mill tank is sealed, vacuumize first, then argon, and continuously Repeat the operation twice to keep the ball milling process in an argon protective atmosphere. Set the rotational speed of the ball mill to 226rpm. In order to prevent the temperature from being too high during the ball milling process, set the ball mill to run forward for 30 minutes, then temporarily stop for 30 minutes, and then turn it in the reverse direction for 30 minutes. This is done alternately. Every 5 hours of ball milling, it is completely stopped for cooling until it is milled for 100 hours. After the ball milling is completed, stop the machine to cool the ball milling tank, take out the mixed powder, place it in a vacuum drying oven, vacuumize, set the temperature at 50°C, and keep it for 24 hours to obtain a dry composite powder.

Step 2: Sintering composite powder

Accurately weigh 16.7g of the composite powder and place it in a graphite mold with an inner diameter of 20.4mm. A layer of graphite paper with a thickness of 0.2mm is placed between the powder and the inner wall of the mold to facilitate demoulding. Then put the mold on the graphite insulation ring, and put it in the spark plasma sintering furnace, and start sintering after evacuating for 30 minutes. Set the temperature to rise to 100°C within 3 minutes, then raise the temperature at a rate of 100°C/min to 700°C, then raise the temperature to 750°C within 3 minutes, and keep at this temperature for 8 minutes, keeping the pressure at 30MPa throughout. After 8 minutes of heat preservation, the furnace was cooled to room temperature, and the sample was taken out to obtain a Cu-Cr composite material.

The morphology, phase and mechanical properties of the samples prepared in Examples 1 to 4 and Comparative Examples were tested and characterized as follows:

(1) Sample surface morphology: use a scanning electron microscope to observe the morphology of the sintered sample surface (see Figures 1 to 3), it can be seen that the Cr reinforcement phase in the Cu-Cr composite material prepared by the present invention is dispersed in the Cu matrix ; while the composite material of the comparative example has a large-sized Cr reinforcing phase in the Cu matrix, and the reinforcing phase is unevenly distributed.

(2) Sample phase analysis: The X-ray diffractometer was used to characterize the phase composition of the sample (see Figures 4 and 5), and no other miscellaneous peaks were found, so the prepared Cu-Cr composite material had a high purity.

(3) Mechanical properties: Vickers hardness tester is used to characterize the hardness of the sample, the test force is 2.94N, the test result is the average value of the test values in 10 different areas, and the deviation of each test value does not exceed 5% of the average value; Use a compression testing machine to conduct a room temperature compression test on the sintered sample, and use the wire cutting method to obtain a sample with a size of Φ3×4.5mm, and the compressive strain rate is 1×10 ^-3 s ^-1 to obtain a room temperature compressive stress-strain curve (see Figure 6) . The mechanical properties of the tested samples are listed in Table 1. It can be seen from Table 1 that the high-strength and high-hardness Cu-Cr composite material prepared by the present invention has excellent mechanical properties while maintaining good plasticity; and under the same sintering conditions, the composite material prepared by the comparative example without pre-milling powder The mechanical properties are obviously worse than those of the composite material of the present invention.

(4) Powder yield: the powder after ball milling and drying is weighed on an electronic scale (pre-milling Cr powder is dry milling, without drying, after ball milling, it is taken out from the ball mill tank and weighed directly), the powder after ball milling The ratio of the mass to the mass of the powder added to the ball mill tank before ball milling is the powder yield of the powder. For example 1, the powder yield of pre-milled Cu powder is 96.1%, and the powder yield after mixing ball milling is 92.7%. %, for comparative examples, the powder yield after mixing and ball milling was 92.1%. It can be seen that adopting a higher content of absolute ethanol for ball milling can obtain a higher powder yield (for Cr powder pre-milling, because Cr itself has a higher hardness, compared with Cu, it is not easy to cause sticking balls and wall sticking, so no need Adding grinding aids for ball milling), it can be seen that under the conditions of this experiment, the utilization rate of raw materials is higher.

Table 1 Mechanical property parameters of Cu-Cr composites

sample Hardness (Hv) Compressive Yield Strength (MPa) Compression ratio(%) Example 1 303 934 twenty one Example 2 327 970 13.7 Example 3 257 926 8.7 Example 4 303 947 11.8 comparative example 246 757 34.1

The above-mentioned embodiment is a preferred embodiment of the present invention, but the embodiment of the present invention is not limited by the above-mentioned embodiment, and any other changes, modifications, substitutions, combinations, Simplifications should be equivalent replacement methods, and all are included in the protection scope of the present invention.

Claims (10)

1. A preparation method of high-strength and high-hardness Cu-Cr composite material is characterized in that comprising the following steps: Cu powder and Cr powder are used as raw materials, wherein a kind of raw material is placed in a high-energy planetary ball mill for pre-milling, and then added Another raw material and grinding aid are mixed and ball milled, and the powder is dried after ball milling and then sintered and densified in a spark plasma sintering furnace to obtain a high-strength and high-hardness Cu-Cr composite material. 2. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: in the raw material, the content of Cr is 8-10% of the total atomic percentage. 3. the preparation method of high-strength and high-hardness Cu-Cr composite material according to claim 1, is characterized in that: the diameter of used grinding ball is respectively 15,10 and 6mm in the described ball mill, and corresponding mass ratio is 1:3: 1. The ball-to-material ratio is 10:1, and the speed of the ball mill is 226rpm. 4. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: the grinding aid is absolute ethanol. 5. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: the amount of the grinding aid used is 70-90% of the mass of the raw material. 6. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: the time for the pre-ball milling treatment is 15-25 hours; the time for the mixed ball-milling treatment is 90-110 hours. 7. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: the process conditions of the sintering densification treatment are sintering pressure of 30-40MPa, sintering temperature of 650-800°C, The holding time is 6-10 minutes; the drying refers to drying in a vacuum oven at a temperature of 50-60° C. for 20-30 hours. 8. The method for preparing high-strength and high-hardness Cu-Cr composite material according to claim 1, characterized in that: when Cu powder is selected for the pre-milling treatment, a grinding aid is added for ball milling together. 9. A high-strength and high-hardness Cu-Cr composite material, characterized in that it is obtained according to the preparation method of the high-strength and high-hardness Cu-Cr composite material according to any one of claims 1-8. 10. The application of the high-strength and high-hardness Cu-Cr composite material according to claim 9 in the structural field.