Oxide dispersion strengthened copper alloy plate and preparation method thereof

Abstract

The invention relates to an oxide dispersion strengthened copper alloy plate and a preparation method thereof, and belongs to the technical field of metal composite materials. The preparation method of the oxide dispersion strengthened copper alloy plate comprises the steps that alloy powder is subjected to internal oxidation to obtain powder containing a dispersion strengthening phase, the powder is reduced and then loaded into a stainless steel sheath to be subjected to hot rolling forming, and finally a pressed blank is sintered at a certain temperature to obtain the oxide dispersion strengthened copper alloy plate. And after sintering, removing the sheath to obtain the oxide dispersion strengthened copper alloy plate. According to the method, the dispersion strengthened copper plate can be directly obtained through the powder wrapping rolling forming technology, the problems that dispersion strengthened copper is poor in machining performance and prone to cracking in the deformation process are solved, the cost can be reduced, the preparation efficiency can be improved, and possibility is provided for large-scale preparation of the dispersion strengthened copper plate.

Description

Technical Field

[0001] The invention belongs to the technical field of metal composite materials, and in particular relates to an oxide dispersion strengthened copper alloy plate and a preparation method thereof. Background Art

[0002] Oxide dispersion strengthened copper alloy is one of the high-strength and high-conductivity copper alloy materials with the best comprehensive performance. Oxide particles as dispersion strengthened phases usually have good thermal and chemical stability, and will not dissolve or react chemically even at high temperatures close to the melting point of the copper matrix. Therefore, oxide particles can still play a dispersion strengthening role at high temperatures, so that this type of material still has high strength, hardness, electrical and thermal conductivity at high temperatures, and is widely used in many important occasions.

[0003] The preparation method of oxide dispersion strengthened copper alloy comprises internal oxidation method, powder metallurgy method, mechanical alloying, spray deposition method and chemical precipitation method etc., wherein internal oxidation method is the optimal method of current large-scale production Al2O3 dispersion strengthened copper alloy material, but aluminum oxide can suppress the sintering of copper powder to a great extent, the initial diffusion energy of matrix increases, makes the volume diffusion of copper difficult to start, the vacancy flow at the neck between particles is hindered, and the growth of sintering neck is slowed down.Therefore common sintering process is very difficult to achieve full densification, full metallurgy combination.In order to promote the metallurgy combination of powder particles, sintered blank must be hot extruded, with the oxide film on the powder particle surface that breaks up, but the product size and shape obtained in this way are also greatly restricted, and it is difficult to obtain large-sized dispersion strengthened copper sheet, which seriously limits the application of dispersion strengthened copper.

[0004] Therefore, developing a process suitable for preparing large quantities of oxide dispersion strengthened copper sheets with good performance is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to overcome the problem in the prior art that nano-oxide dispersion-strengthened copper is difficult to prepare into large-sized plates, and to provide an oxide dispersion-strengthened copper alloy plate and a preparation method thereof.

[0006] The present invention is achieved through the following technical solutions:

[0007] In a first aspect, the present invention provides a method for preparing an oxide dispersion strengthened copper alloy plate, comprising the following steps:

[0008] (1) uniformly mixing alloy powder and Cu2O powder, and performing internal oxidation treatment to obtain internally oxidized powder; the alloy powder comprises at least one of Cu-Al alloy powder and Cu-Y alloy powder;

[0009] (2) subjecting the internally oxidized powder obtained in step (1) to reduction treatment, and then placing it in a stainless steel package and sealing it;

[0010] (3) hot rolling the sealed package in step (2) to obtain a plate-shaped pressed blank, and sintering to obtain the oxide dispersion strengthened copper alloy sheet; the deformation amount per pass during the hot rolling is ≤15%.

[0011] The present invention provides a method for preparing a nano-oxide dispersion-strengthened copper alloy sheet by combining internal oxidation with powder sheath rolling technology. First, the alloy powder is internally oxidized to obtain a powder containing a nano-oxide dispersion-strengthened phase. After reducing the excess oxide, the powder is put into a stainless steel sheath for hot rolling to directly obtain a dispersion-strengthened copper sheet. Finally, the pressed blank is sintered, and the sheath is removed after sintering to obtain a nano-oxide dispersion-strengthened copper alloy sheet with good comprehensive performance. The preparation method of the present invention directly obtains a dispersion-strengthened copper sheet while ensuring the generation of a nano-oxide dispersion-strengthened phase, avoids the problem of poor processing performance of dispersion-strengthened copper and easy cracking during deformation, can reduce costs, improve preparation efficiency, and provide the possibility for large-scale preparation of dispersion-strengthened copper sheets.

[0012] The present invention adopts a preparation method combining internal oxidation and powder coating rolling technology. After internal oxidation, powder containing nano-oxide dispersion phase is obtained. In order to solve the problem that powder molding is difficult after internal oxidation and it is difficult to obtain large-size samples, a powder coating rolling method is used to directly realize powder molding to obtain a dispersion-strengthened copper plate. The size of the plate can be adjusted according to the size of the coating. The prepared nano-oxide dispersion-strengthened copper plate has the advantages of good mechanical properties, adjustable size, low preparation cost, etc.

[0013] The sheath used in the present invention is a stainless steel sheath, which has good plasticity at high temperatures and can prevent the sheath from breaking during hot rolling. In addition to playing a sealing role, the strength of the stainless steel sheath under high temperature conditions is higher than the dispersion-strengthened copper powder strength inside it, so the lateral flow of the powder inside the sheath during hot rolling can be limited, thereby ensuring that the internal powder gradually densifies during multiple hot rolling processes, so that the powder can be compacted, and finally a dense sheet is obtained. Currently commonly used sheaths such as copper or iron sheaths, whose main function is to prevent the powder compact from oxidizing during hot extrusion, that is, the role of sealing, are common means of hot extrusion processes, and ultimately cannot directly obtain a sheet. And hot extrusion molding can only obtain cylindrical bars, and for sheets, hot extrusion molding cannot ensure the uniform flow of materials during extrusion, and the final alloy structure performance will be affected, therefore, it is not suitable to use hot extrusion to obtain a sheet. In addition, when using an iron sheath, it is easy to break due to poor plasticity, and at the same time, the copper or iron sheath has a very low strength at high temperatures, which cannot play a role in limiting the lateral flow of powder, and the free flow of powder during hot rolling will result in a low density and poor performance of the sample finally obtained.

[0014] Preferably, in step (1), the particle size of the alloy powder is ≤50 μm.

[0015] Preferably, in step (1), the particle size of the Cu2O powder is ≤50 μm.

[0016] Preferably, in step (1), the mass fraction of Al element or Y element in the alloy powder is less than 1%.

[0017] Preferably, in step (1), the alloy powder is obtained by melting alloy mother ingots in a vacuum induction furnace and atomizing and powdering.

[0018] Preferably, in step (1), the amount of Cu2O powder added satisfies: 1.0≤oxygen source coefficient (k)≤1.6. More preferably, the amount of Cu2O powder added satisfies: 1.2≤oxygen source coefficient (k)≤1.6; further, the amount of Cu2O powder added satisfies: 1.2≤oxygen source coefficient (k)≤1.4.

[0019] The expression of the oxygen source coefficient k is as follows: k = (mCu2O) / (m′Cu2O), where: mCu2O is the actual mass of Cu2O added to the mixed powder; m′Cu2O is the mass of Cu2O calculated according to the amount of Al or Y in the alloy powder according to the following chemical equation (assuming that the reaction is complete and there is no excess oxygen): 3Cu2O+2A1→6Cu+A12O3 or 3Cu2O+2Y→6Cu+Y2O3.

[0020] Preferably, in step (1), the internal oxidation treatment is carried out in an inert atmosphere, the temperature of the internal oxidation treatment is 800°C-1000°C, and the time is not less than 1 hour; the inert atmosphere includes at least one of nitrogen and argon.

[0021] More preferably, in step (1), the internal oxidation treatment is carried out in an inert atmosphere, the temperature of the internal oxidation treatment is 850°C-950°C, and the time is not less than 3 hours. Optionally, the time of the internal oxidation treatment is 3 hours-9 hours.

[0022] Preferably, in step (2), the reduction treatment is performed using hydrogen, and the temperature of the reduction treatment is 400°C-800°C.

[0023] The present invention does not limit the time of reduction treatment, as long as the excess oxide can be reduced, and can be adjusted conventionally. Preferably, the time of reduction treatment is 3h-9h.

[0024] Preferably, in step (2), the sealing is performed by welding.

[0025] Preferably, in the step (2), the internally oxidized powder obtained in the step (1) is crushed before the hydrogen reduction treatment.

[0026] After internal oxidation, it is necessary to ensure that the Al or Y element in the alloy powder is completely oxidized to generate nano-level Al2O3 or Y2O3 dispersion phase, and then use hydrogen to completely reduce the excess oxide. At the same time, the powder after internal oxidation will be hardened, and the hardened powder needs to be broken before hydrogen reduction. When welding stainless steel sheaths, the welding quality must be ensured and no pores should appear, otherwise the powder inside the sheath will be severely oxidized during the hot rolling process.

[0027] Preferably, in step (3), the hot rolling temperature is 850°C-950°C.

[0028] Preferably, in step (3), the total deformation of the sheath after hot rolling is ≥ 60%.

[0029] Specifically, the hot rolling can be performed by placing the sealed package in a heat treatment furnace for insulation at a temperature of 850° C.-950° C., and then hot rolling the package, with a deformation amount of ≤15% per pass and a total deformation amount of ≥60% in the final rolling.

[0030] The present invention adopts a low deformation and multiple passes method for hot rolling. The hot rolling temperature is 850℃-950℃, which can ensure that the powder softens while the internal nano-oxide dispersed phase does not grow, which is beneficial to forming and does not reduce the alloy performance. The pass deformation needs to be as low as possible, not exceeding 15% at most, otherwise there is a risk of rupture of the sheath. The deformation is obtained by measuring the difference in sheath thickness before and after rolling, and dividing the difference by the thickness before rolling.

[0031] Preferably, in step (3), the sintering temperature is 800°C-1000°C, and the sintering time is 1h-5h.

[0032] Preferably, in step (3), the sintering temperature is 800°C-950°C, and the sintering time is 3h-5h.

[0033] Preferably, in the step (3), the sintering is performed in an inert atmosphere, and the inert atmosphere includes at least one of nitrogen and argon.

[0034] In a second aspect, the present invention provides an oxide dispersion strengthened copper alloy sheet material obtained by the method for preparing the oxide dispersion strengthened copper alloy sheet material.

[0035] The nano-oxide dispersion-strengthened copper alloy plate obtained by the preparation method of the present invention has high density and excellent mechanical properties.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) Preparation of oxide dispersion strengthened copper powder by internal oxidation method Due to the presence of a large amount of oxide on the surface, the bonding between the powders is poor, and it is difficult to achieve powder molding by conventional powder molding methods. The present invention adopts powder sheathing rolling molding. During the rolling process, the internal oxidation powder will deform and break, thereby deforming and breaking the oxide film on the powder surface to achieve redistribution, thereby achieving good metallurgical bonding between the powders, and obtaining a completely dense material with good performance.

[0038] (2) Although nano-oxide dispersion-strengthened copper has excellent mechanical properties and electrical conductivity, its processing performance is poor, especially dispersion-strengthened copper with a high aluminum content, which is prone to cracking during deformation processing, so it is difficult to prepare dispersion-strengthened copper sheets. The present invention uses a powder sheathing rolling process as a powder forming method to directly obtain nano-oxide dispersion-strengthened copper sheets without the need for subsequent deformation processing, which greatly improves the efficiency and success rate of preparing dispersion-strengthened copper sheets.

[0039] (3) The preparation of large-sized nano-oxide dispersion-strengthened copper sheets is extremely difficult. However, the present invention adopts powder sheathing rolling forming technology to achieve the preparation of nano-oxide dispersion-strengthened copper sheets by designing sheaths of different sizes. In addition, this method is not limited by the size of hot extrusion or hot pressing equipment, and can achieve the preparation of large-sized nano-oxide dispersion-strengthened copper components.

[0040] (4) In the prior art, the method of combining internal oxidation and hot extrusion is only suitable for preparing dispersion-strengthened copper rods, and the preparation cost is high and the production efficiency is low, which seriously restricts the application of dispersion-strengthened copper. The present invention avoids the hot extrusion process, provides a new technical approach for the preparation of nano-oxide dispersion-strengthened copper, and is simple to operate and low in cost, which is conducive to the large-scale preparation of oxide dispersion-strengthened copper. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 This is an optical photograph of the oxide dispersion strengthened copper alloy plate obtained in Example 1;

[0042] Figure 2 This is a metallographic image of the oxide dispersion strengthened copper alloy plate obtained in Example 1;

[0043] Figure 3 This is an optical photograph of the plate-shaped compact after hot rolling in Example 2;

[0044] Figure 4 This is a SEM image of the oxide dispersion strengthened copper alloy plate obtained in Example 2;

[0045] Figure 5 This is an optical photograph of the plate-shaped compact after hot rolling in Comparative Example 1. DETAILED DESCRIPTION

[0046] To better illustrate the purpose, technical solutions and advantages of the present invention, the present invention will be further described below in conjunction with specific embodiments. It should be understood by those skilled in the art that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0047] Unless otherwise specified, the experimental methods used in the examples are all conventional methods; the materials, reagents, etc. used, unless otherwise specified, can be obtained from commercial channels.

[0048] Example 1

[0049] A method for preparing an oxide dispersion strengthened copper alloy plate comprises the following steps:

[0050] (1) alloy powder and Cu2O powder are mixed, the oxygen source coefficient is 1.2, and the mixture is placed in a drum ball mill for ball milling to make the mixture uniform. Subsequently, the mixed powder is placed in a quartz tube, and an internal oxidation process is carried out under argon protection, the internal oxidation temperature is 900°C, the time is 3h, and the internal oxidation powder is obtained; the alloy powder is Cu-0.76Al alloy powder (mass percentage), and the preparation method thereof is: using a 100kg vacuum induction furnace to melt the alloy ingot, and then using argon spray powdering to obtain the above-mentioned Al-containing copper-based alloy powder, and screening out the powder with a particle size of less than 50μm, that is, the alloy powder; the particle size of the Cu2O powder is ≤50μm;

[0051] (2) crushing the internally oxidized powder obtained in step (1), reducing the excess oxide from the crushed powder using hydrogen at a reduction temperature of 400° C. for 4 h, placing the reduced powder into a 70×50×30 mm stainless steel sheath, and then welding and sealing the sheath using argon arc welding;

[0052] (3) The sealed package in step (2) is kept at 900° C. for 30 min, and then hot rolling is started. The initial thickness of the package is 30 mm, the deformation of the pass is 10%, the final rolling thickness is 3 mm, and the total deformation of the package is 90%. After the hot rolling is completed, a plate-shaped compact of 290×60×3 mm is obtained. The hot-rolled plate-shaped compact is sintered at 900° C. for 3 h in an argon atmosphere, and then the package is removed to obtain the oxide dispersion strengthened copper alloy sheet.

[0053] The optical photograph of the obtained oxide dispersion strengthened copper alloy sheet is as follows: Figure 1 As shown, the metallographic diagram is as follows Figure 2 As shown, its density is 8.56g / cm 3 The density reaches 96%. The metallographic results also show that the interior is relatively dense and the powders are well bonded. The room temperature tensile strength of the oxide dispersion strengthened copper sheet of this embodiment is 560MPa and the electrical conductivity is 70IACS%.

[0054] Example 2

[0055] A method for preparing an oxide dispersion strengthened copper alloy plate comprises the following steps:

[0056] (1) alloy powder and Cu2O powder are mixed, the oxygen source coefficient is 1.3, and the mixture is placed in a drum ball mill for ball milling to make the mixture uniform. Subsequently, the mixed powder is placed in a quartz tube, and an internal oxidation process is carried out under argon protection, the internal oxidation temperature is 850°C, the time is 3h, and the internal oxidation powder is obtained; the alloy powder is Cu-0.15Al alloy powder (mass percentage), and the preparation method thereof is: using a 50kg vacuum induction furnace to melt the alloy ingot, and then using argon spray powdering to obtain the above-mentioned Al-containing copper-based alloy powder, and screening out the powder with a particle size of less than 50μm, that is, the alloy powder; the particle size of the Cu2O powder is ≤50μm;

[0057] (2) crushing the internally oxidized powder obtained in step (1), reducing the excess oxide from the crushed powder using hydrogen at a reduction temperature of 400° C. for 8 h, placing the reduced powder into a 30 mm thick stainless steel sheath, and then welding the sheath to seal it using argon arc welding;

[0058] (3) The sealed package in step (2) is kept at 950° C. for 30 min, and then hot rolling is started. The initial thickness of the package is 30 mm, the deformation of the pass is 15%, the final rolling thickness is 7.5 mm, and the total deformation of the package is 75%. The hot-rolled plate-shaped pressed blank is sintered at 950° C. for 3 h in an argon atmosphere, and then the package is removed to obtain the oxide dispersion strengthened copper alloy sheet.

[0059] The optical photograph of the hot-rolled plate-shaped compact is shown in Figure 3 The SEM image of the obtained oxide dispersion strengthened copper alloy sheet is shown in Figure 4 As shown, from Figure 4 It can be seen that there are a large number of uniformly distributed dispersion strengthening phases in the alloy, with sizes concentrated around 12-17 nm. The room temperature tensile strength of the oxide dispersion strengthening copper sheet of this embodiment is 355 MPa, and the electrical conductivity is 82 IACS%.

[0060] Example 3

[0061] The preparation method of the oxide dispersion strengthened copper alloy plate in this embodiment is different from that in embodiment 1 in that in step (3), the temperature during hot rolling is 850° C., and the rest of the preparation method is the same as that in embodiment 1. The oxide dispersion strengthened copper alloy plate obtained in this embodiment has a density of 96.5%, a room temperature tensile strength of 580 MPa, and a conductivity of 69.8 IACS%.

[0062] Example 4

[0063] The difference between the preparation method of the oxide dispersion strengthened copper alloy plate in this embodiment and that in embodiment 1 is that in step (1), the oxygen source coefficient is 1.0, and the rest of the preparation method is the same as that in embodiment 1. The oxide dispersion strengthened copper alloy plate obtained in this embodiment has a density of 98%, a room temperature tensile strength of 503 MPa, and a conductivity of 71 IACS%.

[0064] Example 5

[0065] The preparation method of the oxide dispersion strengthened copper alloy plate in this embodiment is different from that in embodiment 1 in that in step (1), the oxygen source coefficient is 1.6, and the rest of the preparation method is the same as that in embodiment 1. The oxide dispersion strengthened copper alloy plate obtained in this embodiment has a density of 96%, a room temperature tensile strength of 582 MPa, and a conductivity of 69.4 IACS%.

[0066] Example 6

[0067] The difference between the preparation method of the oxide dispersion strengthened copper alloy plate in this embodiment and that in embodiment 1 is that in step (3), the temperature during hot rolling is 800° C., and the rest of the preparation method is the same as that in embodiment 1. The oxide dispersion strengthened copper alloy plate obtained in this embodiment has a density of 93%, a room temperature tensile strength of 506 MPa, and a conductivity of 63 IACS%.

[0068] Example 7

[0069] The difference between the preparation method of the oxide dispersion strengthened copper alloy plate in this embodiment and that in embodiment 1 is that in step (3), the temperature during hot rolling is 1000° C., and the rest of the preparation method is the same as that in embodiment 1. The oxide dispersion strengthened copper alloy plate obtained in this embodiment has a density of 97.5%, a room temperature tensile strength of 525 MPa, and a conductivity of 66.5 IACS%.

[0070] Comparative Example 1

[0071] The difference between the preparation method of the oxide dispersion strengthened copper alloy plate of this comparative example and that of Example 1 is that the pass deformation during hot rolling in step (3) is 20%, and the optical photograph of the plate-shaped pressed blank after hot rolling is as follows: Figure 5 As shown, it can be seen that the edges and corners of the sheath are broken due to excessive deformation, resulting in the final oxide dispersion strengthened copper alloy plate having a density of 92%, a room temperature tensile strength of 460 MPa, and a conductivity of 58 IACS%. The main reason is that the powder leakage is serious after the sheath is broken, and the powder inside the sheath is severely oxidized during hot rolling.

[0072] Comparative Example 2

[0073] The difference between the preparation method of the oxide dispersion strengthened copper alloy plate in this comparative example and that in Example 1 is that in step (2), a copper sheath is used to replace the stainless steel sheath, and the rest of the preparation method is the same as that in Example 1. Since the copper sheath has very low strength at high temperature and cannot restrain the flow of powder during hot rolling, the oxide dispersion strengthened copper alloy plate cannot be obtained in the end.

[0074] Comparative Example 3

[0075] The preparation method of the oxide dispersion strengthened copper alloy plate in this comparative example is different from that in Example 1 in that, in step (2), an iron sheath is used to replace the stainless steel sheath, and the rest of the preparation method is the same as that in Example 1. Since the strength of the iron sheath is relatively poor at high temperatures, the final oxide dispersion strengthened copper alloy plate has a density of 58%, a room temperature tensile strength of 387 MPa, and a conductivity of 49 IACS%.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing an oxide dispersion strengthened copper alloy sheet, characterized in that: The following steps are involved: (1) uniformly mixing alloy powder and Cu2O powder, and performing internal oxidation treatment to obtain internally oxidized powder; the alloy powder comprises at least one of Cu-Al alloy powder and Cu-Y alloy powder; (2) subjecting the internally oxidized powder obtained in step (1) to reduction treatment, and then placing it in a stainless steel package and sealing it; (3) hot rolling the sealed package in step (2) to obtain a plate-shaped pressed blank, and sintering to obtain the oxide dispersion strengthened copper alloy sheet; the deformation amount per pass during the hot rolling is ≤15%.

2. The method for preparing the oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (1), the particle size of the alloy powder is ≤50 μm; and / or the particle size of the Cu2O powder is ≤50 μm.

3. The method for preparing the oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (1), the mass fraction of the Al element or the Y element in the alloy powder is less than 1%.

4. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (1), the amount of Cu2O powder added satisfies: 1.0≤oxygen source coefficient≤1.

6.

5. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (1), the internal oxidation treatment is carried out in an inert atmosphere, the temperature of the internal oxidation treatment is 800° C.-1000° C., and the time is not less than 1 hour.

6. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (2), the reduction treatment is performed using hydrogen, and the temperature of the reduction treatment is 400°C-800°C.

7. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (3), the hot rolling temperature is 850°C-950°C.

8. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: In the step (3), the total deformation of the sheath after hot rolling is ≥ 60%.

9. The method for preparing an oxide dispersion strengthened copper alloy sheet according to claim 1, characterized in that: The sintering is carried out in an inert atmosphere, the sintering temperature is 800° C.-1000° C., and the sintering time is 1 h-5 h.

10. The oxide dispersion strengthened copper alloy sheet obtained by the method for preparing the oxide dispersion strengthened copper alloy sheet according to any one of claims 1 to 9.

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