Preparation method of high-strength and high-conductivity Cu-Y2O3-Ag composite material

Abstract

A preparation method of a high-strength and high-conductivity Cu-Y2O3-Ag composite material, which relates to the field of preparation of high-strength and high-conductivity copper alloys. First, a copper-yttrium precursor powder is prepared from a metal yttrium salt and electrolytic copper powder, and then the copper-yttrium precursor powder and Cu-Ag alloy powder are prepared through a mechanical alloying process and reduction combined with field-assisted sintering. In the present invention, the addition of Ag and Y2O3 realizes the high strength and high conductivity of copper alloys through the combined action of the solid solution strengthening mechanism and the dispersion strengthening mechanism. The present invention uses mechanical alloying technology to achieve the uniform distribution of Y2O3 and Ag atoms in the copper matrix at the atomic level. After Ag atoms enter the copper lattice, a small amount of Ag atoms can improve the conductivity of the material with less Y2O3, and at the same time greatly increase the strength of the copper alloy, achieving the effect of solid solution strengthening.

Description

Technical Field

[0001] The invention relates to the field of preparation of high-strength and high-conductivity copper alloys, and in particular to a method for preparing a high-strength and high-conductivity Cu-Y2O3-Ag composite material. Background Art

[0002] Copper has excellent electrical and thermal conductivity and is widely used in resistance welding electrodes, rocket or jet aircraft, generator rotor wires, self-cooling thermal conductive materials for electric vacuum devices, and other fields. However, the poor mechanical properties of pure copper, especially high temperature performance, limit its application in the above fields. At present, the common methods to enhance the mechanical properties of copper alloys are solid solution strengthening and second phase dispersion strengthening. Solid solution strengthening is to introduce solute atoms into the copper matrix to cause lattice distortion to increase the strength; dispersion strengthening is to introduce uniform and fine second phase particles to hinder the movement of grain boundaries and dislocations to achieve the purpose of increasing strength. The above two methods often come at the cost of losing their electrical conductivity. Therefore, an important challenge in the development of high-performance copper alloys is whether it is possible to maintain their electrical conductivity as much as possible while greatly improving the mechanical properties.

[0003] Y2O3 dispersion-strengthened copper alloy is a metal-based composite material that combines thermal conductivity and strength. As a fluorite-like second phase, Y2O3 can form a coherent or semi-coherent interface with a higher interface strength with the copper matrix. At the same time, it has a higher formation enthalpy and can remain stable at high temperatures, thereby more effectively pinning the grain boundaries and improving the high-temperature strength of the material. However, the introduction of the second phase inevitably causes the copper lattice to scatter electrons, resulting in a decrease in the conductivity of the material. The extremely small solid solubility of Y2O3 in copper causes yttrium to be segregated at the grain boundaries in the form of intermetallic compounds. The Y2O3 content is limited, and the strength of the Y2O3 dispersion-strengthened copper alloy reaches an upper limit.

[0004] The effect of trace Ag dissolved in copper alloy on electrical conductivity is not significant, and Ag distributed in the copper matrix can also improve the strength and hardness of copper, producing a strong solid solution strengthening effect. Generally speaking, when alloying elements are added to copper, the solute atoms dissolve into the lattice, which will cause lattice distortion. The scattering effect of this distorted lattice on moving electrons is also correspondingly aggravated. Therefore, the effect of solid solution strengthening on the electrical conductivity and strength of copper is contradictory. Ag is different from other elements that can be dissolved in copper. When the silver content is low, the electrical conductivity and thermal conductivity of copper hardly decrease, and the effect on plasticity is also minimal. It can significantly improve the recrystallization temperature, high temperature creep strength and high temperature thermal low cycle fatigue resistance of copper. The use of the second relative strength enhancement effect of Y2O3 and the high conductivity characteristics of Ag dissolved in copper alloys can become the key to the preparation of high-strength and high-conductivity copper alloys. Summary of the invention

[0005] The present invention provides a method for preparing a high-strength and high-conductivity Cu-Y2O3-Ag composite material, and realizes the preparation of a high-strength and high-conductivity copper alloy material by adding Ag and Y2O3.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing a high-strength and high-conductivity Cu-Y2O3-Ag composite material, comprising the following steps:

[0008] Step 1: Prepare copper-yttrium precursor powder:

[0009] Dissolve yttrium nitrate in deionized water, drop excessive ammonia water into the above solution. As the ammonia water is added, precipitates in the solution start to form; then add electrolytic copper powder, fully stir and heat to evaporate the solution, dry and grind to obtain copper-yttrium precursor powder;

[0010] Step 2: Mechanical alloying:

[0011] Put the copper-yttrium precursor powder and Cu-Ag alloy powder into a ball milling tank, complete the assembly under the argon atmosphere in a glove box, and then place the ball milling tank on a planetary ball mill for ball milling;

[0012] Step 3: Hydrogen thermal reduction:

[0013] Put the ball-milled powder in a firing boat and reduce it under the hydrogen atmosphere in a high-temperature tube furnace to obtain Cu-Y2O3-Ag composite powder;

[0014] Step 4: Field-assisted sintering:

[0015] Weigh a certain amount of Cu-Y2O3-Ag composite powder, grind it and put it into a graphite mold, pre-press it under a certain pressure. After the mold is placed in the sintering furnace cavity, pump the pressure in the furnace cavity to vacuum and maintain the vacuum state, set the sintering program to sinter and form the sample;

[0016] Step 5: Hot rolling deformation:

[0017] Hot roll the sintered composite material at a certain temperature; for different passes, reasonably allocate the pass deformation amount according to the total deformation amount, and finally prepare the Cu-Y2O3-Ag composite material.

[0018] As the preferred technical solution proposed by the present invention, in the preparation method:

[0019] In Step 1, the weight ratio between yttrium nitrate and electrolytic copper powder is 1:10-20, the particle size of the electrolytic copper powder is 1-3 um, and the temperature for heating and evaporating the solution is 100-120 °C.

[0020] In Step 2, the weight ratio between the copper-yttrium precursor powder and the Cu-Ag alloy powder is 0.4-0.6∶0.4-0.6, and the proportion of Ag in the Cu-Ag alloy powder is 0.05-0.2%.

[0021] In Step 2, the ball milling speed is 400-500 rpm, the ball-to-powder ratio is 7-10:1, and the ball milling time is 24-32 h.

[0022] In Step 3, reduction is carried out at 450-550 °C for 1-5 h under a hydrogen atmosphere in a high-temperature tube furnace.

[0023] The steps of field-assisted sintering in Step 4 are as follows: Weigh the composite powder, grind it, and load it into a graphite mold. Perform pre-pressing under a pressure of 10 MPa. After the mold is placed in the sintering furnace chamber, evacuate the pressure in the furnace chamber to vacuum and maintain the vacuum state. Set the sintering program to sinter and form the sample; the sintering program is: The sample is heated from room temperature to 600 °C at a heating rate of 100 °C / min, held for 6 min, then heated to 800 °C at a heating rate of 100 °C / min, held for 5 min, and then cooled with the furnace; in the heating stage from 600 °C to 800 °C, the pressure increases from 50 MPa to 100 MPa.

[0024] In Step 5, the hot rolling temperature is 400-600 °C. The total deformation is 30%, and rolling is carried out in 3 passes, with a deformation of 10% in each pass.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. Adding the rare earth element yttrium oxide Y2O3, the third component, to the Cu matrix plays a role in dispersion strengthening. However, the introduction of the second phase inevitably causes the scattering of electrons by the copper lattice, resulting in a decrease in the electrical conductivity of the alloy while increasing the strength, that is, the electrical conductivity of dispersion-strengthened copper decreases with the increase in the content of the reinforcing phase Y2O3. Therefore, the present invention improves the electrical conductivity by introducing Ag. After Ag atoms enter the copper lattice, a small amount of Ag atoms can improve the electrical conductivity of the material with less Y2O3, and at the same time greatly increase the strength of the copper alloy, achieving the effect of solid solution strengthening.

[0027] 2. The present invention realizes the high strength and high conductivity of the copper alloy by jointly implementing the solid solution strengthening mechanism and the dispersion strengthening mechanism through adding Ag and Y2O3. The preparation process uses mechanical alloying technology to achieve the uniform distribution of Y2O3 and Ag atoms in the copper matrix at the atomic level, and successfully prepares a high-strength and high-conductivity Cu-Y2O3-Ag composite material. Description of the Drawings

[0028] Figure 1 It is the metallographic structure diagram of the Cu-1wt% Y2O3-0.06wt% Ag composite material prepared in Example 1.

[0029] Figure 2 Scanning electron micrograph of the tensile fracture surface of the Cu-1 wt% Y2O3-0.08 wt% Ag composite prepared in Example 2.

[0030] Figure 3 Engineering stress-strain curve of the Cu-1 wt% Y2O3-0.12 wt% Ag composite prepared in Example 3. Detailed implementation manners

[0031] The following elaborates on the preferred embodiments and comparative examples of the present invention in detail, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0032] The embodiments of the present invention mainly compare the properties of two materials, Cu-Y2O3 and Cu-Y2O3-Ag, and at the same time explore the influence of the mass fraction of Ag on the properties of the composite material.

[0033] Example 1

[0034] A method for preparing a high-strength and high-conductivity Cu-Y2O3-Ag composite material, the steps are as follows:

[0035] Step 1: Prepare copper-yttrium precursor powder:

[0036] Dissolve 3.392 g of yttrium nitrate in 400 mL of deionized water, and drop excessive ammonia water into the above solution. As the ammonia water is added, precipitates in the solution start to form. Then add 49 g of electrolytic copper powder with a particle size of 1-3 μm, and stir well with a glass rod. Place the mixed solution on a magnetic stirrer and stir at a temperature of 120 °C and a rotation speed of 130 rpm until the solution is completely evaporated. Dry the obtained precursor powder in an oven at 150 °C for 8 h to completely remove the ammonia water in the precursor. Finally, grind it with a mortar to obtain copper-yttrium precursor powder.

[0037] Step 2: Mechanical alloying:

[0038] Put 50 g of copper-yttrium precursor powder and 50 g of Cu-Ag alloy powder with an Ag content of 0.06 wt% into a ball milling tank. Complete the assembly under an argon atmosphere in a glove box. Place the ball milling tank on a planetary ball mill for ball milling. The ball milling speed is 500 rpm, the ball-to-powder ratio is 7:1, and the ball milling time is 32 h.

[0039] Step 3: Hydrogen thermal reduction:

[0040] Put the ball-milled powder in a boat and reduce it at 500 °C for 2 h in a hydrogen atmosphere in a high-temperature tube furnace. The cooling method is furnace cooling, and finally Cu-1wt% Y2O3-0.06wt% Ag composite powder is obtained.

[0041] Step 4: Field-assisted sintering:

[0042] Weigh 14 g of the Cu-1wt% Y2O3-0.06wt% Ag composite powder obtained in Step 3, grind it and load it into a graphite mold, and pre-press it under a pressure of 10 MPa. After the mold is placed in the sintering furnace cavity, the pressure in the furnace cavity is pumped to vacuum and maintained in a vacuum state. Set the sintering program to sinter and form the sample.

[0043] The sintering program is as follows: The sample is heated from room temperature to 600 °C at a heating rate of 100 °C / min, held for 6 min, then heated to 800 °C at a heating rate of 100 °C / min, held for 5 min, and then furnace-cooled. During the heating stage from 600 °C to 800 °C, the pressure increases from 50 MPa to 100 MPa.

[0044] Step 5: Hot rolling deformation:

[0045] Hot roll the sintered composite material at 400 °C. The total deformation is 30%, and it is rolled in 3 passes, with a deformation of 10% in each pass. Finally, a Cu-1wt% Y2O3-0.06wt% Ag composite material is obtained.

[0046] Figure 1 For Example 1, a metallographic structure diagram of the Cu-1wt% Y2O3-0.06wt% Ag composite material is prepared. By Figure 1 It can be observed that the grains of the composite material are nanocrystals. The mechanical alloying process brings good fine-grain strengthening effect and ensures the strength of the material.

[0047] Example 2

[0048] The preparation method is the same as that of Example 1, except that the proportion of Ag in the Cu-Ag alloy powder added in Step 2 is 0.08 wt%, and a Cu-1wt% Y2O3-0.08wt% Ag composite material is prepared.

[0049] Figure 2 For Example 2, a scanning diagram of the tensile fracture surface of the Cu-1wt% Y2O3-0.08wt% Ag composite material is prepared. From the figure, uniformly fine dimples can be observed, thus verifying the excellent elongation of the material.

[0050] Example 3

[0051] The preparation method is the same as that of Example 1, except that the proportion of Ag in the Cu-Ag alloy powder added in Step 2 is 0.12 wt%, and the Cu-1 wt% Y2O3-0.12 wt% Ag composite material is prepared.

[0052] Figure 3 is the engineering stress-strain curve of the Cu-1 wt% Y2O3-0.12 wt% Ag composite material prepared in Example 3. It can be seen that the tensile strength of the composite material has approached 400 MPa, meeting the strength requirements of high-strength and high-conductivity copper alloys.

[0053] Example 4

[0054] In this example, as a comparative example, no Cu-Ag alloy powder is added during mechanical alloying. The specific steps are as follows:

[0055] Step 1. Prepare copper-yttrium precursor powder:

[0056] Dissolve 10.177 g of yttrium nitrate in 400 mL of deionized water. Drop excessive ammonia water into the above solution. As the ammonia water is added, precipitates start to form in the solution. Then add 47 g of electrolytic copper powder with a particle size of 1-3 μm, and stir well with a glass rod. Place the mixed solution on a magnetic stirrer and stir at a temperature of 120 °C and a rotation speed of 130 rpm until the solution is completely evaporated. Dry the obtained precursor powder in an oven at 150 °C for 8 h to completely remove the ammonia water in the precursor. Finally, grind it with a mortar to obtain copper-yttrium precursor powder.

[0057] Step 2. Mechanical alloying:

[0058] Load 50 g of the copper-yttrium precursor powder into a ball milling tank. Complete the assembly under an argon atmosphere in a glove box. Place the ball milling tank on a planetary ball mill for ball milling. The ball milling speed is 500 rpm, the ball-to-powder ratio is 7:1, and the ball milling time is 32 h.

[0059] Step 3. Hydrogen thermal reduction:

[0060] Place the ball-milled powder in a firing boat and reduce it at 500 °C for 2 h under a hydrogen atmosphere in a high-temperature tube furnace. The cooling method is furnace cooling, and finally, Cu-3 wt% Y2O3 composite powder is obtained.

[0061] Step 4. Field-assisted sintering:

[0062] Weigh 14 g of the Cu-3 wt% Y2O3 composite powder obtained in Step 3, grind it, and load it into a graphite mold. Perform pre-pressing under a pressure of 10 MPa. After the mold is placed in the sintering furnace cavity, evacuate the pressure in the furnace cavity and maintain the vacuum state. Set the sintering program to sinter and form the sample.

[0063] The sintering process is as follows: The sample is heated from room temperature to 600 °C at a heating rate of 100 °C / min, held for 6 min, then heated to 800 °C at a heating rate of 100 °C / min, held for 5 min, and then cooled in the furnace. During the heating stage from 600 °C to 800 °C, the pressure increases from 50 MPa to 100 MPa.

[0064] Step Five, hot rolling deformation:

[0065] The sintered composite material is hot rolled at 400 °C. The total deformation is 30%, and it is rolled in 3 passes, with a deformation of 10% in each pass. Finally, the Cu-3wt% Y2O3 composite material is obtained.

[0066] Table 1 Performance of composite materials prepared in each example

[0067]

[0068] Table 1 shows the conductivity and tensile strength of Cu composite materials prepared in different examples. As the Ag content increases, the lattice distortion becomes more serious, resulting in a decrease in conductivity. However, comparing the two materials of Cu-Y2O3 and Cu-Y2O3-Ag, the incorporation of Ag can reduce the content of Y2O3, thereby improving the conductivity of the material, and the contribution brought by solid solution strengthening becomes higher, and the strength increases. Considering the conductivity and tensile strength comprehensively, the Cu-1wt% Y2O3-0.08wt% Ag composite material prepared with an Ag content of 0.08%wt has the best comprehensive performance.

[0069] The above content is only an example and illustration of the concept of the present invention. Those skilled in the art of this technology can make various modifications or supplements to the described specific embodiments or use similar methods to replace them, as long as they do not deviate from the concept of the invention or exceed the scope defined by this claim book, they should all belong to the protection scope of the present invention.

Claims

1. A preparation method of a high-strength and high-conductivity Cu-Y2O3-Ag composite material, characterized in that, The steps are as follows: Step 1: Prepare the copper-yttrium precursor powder: Dissolve yttrium nitrate in deionized water, and drop excessive ammonia water into the above solution. As the ammonia water is added, precipitates start to form in the solution; then add electrolytic copper powder, fully stir and heat to evaporate the solution, dry and grind to obtain the copper-yttrium precursor powder; among them, the weight ratio between yttrium nitrate and electrolytic copper powder is 1∶10 - 20, and the temperature for heating and evaporating the solution is 100 - 120°C; Step 2: Mechanical alloying: Put the copper-yttrium precursor powder and Cu-Ag alloy powder into a ball milling jar together, complete the assembly under the argon atmosphere in a glove box, and then place the ball milling jar on a planetary ball mill for ball milling; among them, the weight ratio between the copper-yttrium precursor powder and Cu-Ag alloy powder is 0.4 - 0.6∶0.4 - 0.6, and the proportion of Ag in the Cu-Ag alloy powder is 0.05 - 0.2%; Step 3: Hydrogen thermal reduction: Put the ball-milled powder in a firing boat and reduce it at 450 - 550°C for 1 - 5 h under the hydrogen atmosphere in a high-temperature tube furnace to obtain the Cu-Y2O3-Ag composite powder; Step 4: Field-assisted sintering: Weigh a certain amount of Cu-Y2O3-Ag composite powder, grind it and put it into a graphite mold, pre-press it under a certain pressure. After the mold is placed in the sintering furnace cavity, pump the pressure in the furnace cavity to vacuum and maintain the vacuum state, set the sintering program to make the sample sinter and form; Step 5: Hot rolling deformation: Perform hot rolling on the sintered composite material at 400 - 600°C; for different passes, reasonably allocate the pass deformation amount according to the total deformation amount, and finally prepare the Cu-Y2O3-Ag composite material.

2. The preparation method according to claim 1, characterized in that, In Step 1, the particle size of the electrolytic copper powder is 1 - 3 um.

3. The preparation method according to claim 1, characterized in that, In Step 2, the ball milling speed is 400 - 500 rpm, the ball-to-powder ratio is 7 - 10∶1, and the ball milling time is 24 - 32 h.

4. The preparation method according to claim 1, characterized in that, The field-assisted sintering step in Step 4 is: Weigh the composite powder, grind it and put it into a graphite mold, pre-press it under a pressure of 10 MPa. After the mold is placed in the sintering furnace cavity, pump the pressure in the furnace cavity to vacuum and maintain the vacuum state, set the sintering program to make the sample sinter and form; the sintering program is: the sample is heated from room temperature to 600°C at a heating rate of 100°C / min, held for 6 min, then heated to 800°C at a heating rate of 100°C / min, held for 5 min, and then cooled with the furnace; in the heating stage from 600°C to 800°C, the pressure increases from 50 MPa to 100 MPa.

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