阅读说明：本技术 一种Cu-Cr-Zr合金的制备方法 (Preparation method of Cu-Cr-Zr alloy ) 是由 刘吉梓 刘壮家 欧艺文 王经涛 于 2018-06-25 设计创作，主要内容包括：本发明涉及一种Cu-Cr-Zr合金的制备方法,该方法通过ECAP后进行低温变形以及随后的时效处理制得Cu-Cr-Zr合金。本发明制备的Cu-Cr-Zr合金抗拉强度为710～730MPa,导电率为75.2～80％IACS,硬度为225～234HV,断后延伸率为14～15％左右,且具有优良的加工成形能力。不仅可以代替电气化铁路电力牵引用的接触线,而且在城市轨道交通,工矿电气化运输和起重系统等领域也可以得到广泛应用。(The invention relates to a method for producing a Cu-Cr-Zr alloy by low-temperature deformation after ECAP and subsequent ageing. The Cu-Cr-Zr alloy prepared by the method has the tensile strength of 710-730 MPa, the electric conductivity of 75.2-80% IACS, the hardness of 225-234 HV, the elongation after fracture of about 14-15%, and excellent processing and forming capability. The method can not only replace the contact line for electric traction of the electrified railway, but also be widely applied to the fields of urban rail transit, industrial and mining electrified transportation, hoisting systems and the like.)

1. The preparation method of the Cu-Cr-Zr alloy is characterized by comprising the following specific preparation steps:

step 1 solution treatment

And (3) keeping the temperature of the forged square rod at 1000-1050 ℃ for 0.5-2 hours, and then carrying out water quenching at room temperature.

Step 2 equal channel angular extrusion

And putting the copper alloy bar subjected to the solution treatment into a die for 4-12 times of extrusion.

Step 3 Low temperature deformation

Before rolling, soaking the sample extruded at the equal channel angle in liquid nitrogen for 20-40min to ensure that the deformation temperature of the sample is between-150 ℃ and-100 ℃; after each pass is finished, putting the steel plate into liquid nitrogen, preserving heat for 10-20 minutes, and then performing the next pass, wherein the rolling deformation degree is about 80-85%, and the strain speed during rolling is controlled at 1 multiplied by 10^-3～1×10^-2s^-1Left and right.

Step 4 aging treatment

And (3) keeping the temperature of the sample after low-temperature deformation at the temperature of 420-520 ℃ for 0.5-8 hours, and then carrying out air quenching to optimize the precipitation of Cr particles and test the thermal stability of the UFG structure.

2. The method for preparing the Cu-Cr-Zr alloy according to claim 1, wherein the Cu-Cr-Zr alloy comprises the following components in percentage by mass:

Cr：0.3～1.0％

Zr：0.05～0.3％

si: 0.03-0.08%, and the balance of Cu and some inevitable impurity elements in the casting process.

3. The method of producing a Cu-Cr-Zr alloy according to claim 1, characterized in that the forged square bar is produced as follows:

the first step is as follows: melting and casting

Taking pure electrolytic copper, chromium and zirconium, taking alloy components according to the alloy component ratio, and heating the alloy components in a vacuum induction furnace to 1220-1270 ℃ for melting; removing impurities and degassing, standing for 20-40 minutes, and casting to obtain a cast ingot;

the second step is that: homogenization treatment

Heating the ingot to 920-;

the third step: conventional heat distortion

And (3) removing the surface of the ingot after homogenization treatment, putting the ingot into a vacuum heating furnace, heating to 850-900 ℃, and forging into a square rod after hot forging.

4. The method of claim 3, wherein the first step is carried out by mixing graphite powder with cryolite and covering the surface of the liquid.

5. The method of claim 3, wherein in the first step the purity of the pure electrolytic copper is 99.99%, the purity of chromium is 99.7% and the purity of zirconium is 99.7%.

6. The method of claim 1, wherein in step 2, the path "a" is used, that is, the next pass is performed without rotating the angle after each extrusion; the 'C' path is rotated by 180 degrees after one pass of extrusion is finished each time; the Ba path is that the sample rotates 90 degrees clockwise and anticlockwise alternately before each extrusion; or "Bc" path, i.e. 90 ° clockwise rotation of the specimen before each compression; wherein, the inner angle of the mold90 degrees, an external angle of 30 degrees, and an extrusion rate limited within 1 mm/s.

7. The method of claim 1, wherein in step 3, the Cu-Cr-Zr alloy is further cold drawn at a liquid nitrogen temperature.

8. A Cu-Cr-Zr alloy produced based on the production method described in any one of claims 1 to 7.

Technical Field

The invention relates to a preparation method of a Cu-Cr-Zr alloy, belonging to the field of preparation and processing of metal materials.

Background

With the development of the electrified railway at higher and higher speeds, the suspension tension applied to the contact wire and the surface friction force between the contact wire and the pantograph are inevitably increased, so that the technical quality requirement on the contact wire is higher and higher. The ideal performance indexes of the contact line are as follows: tensile strength is more than 560MPa, conductivity is more than 80% IACS and processing formability is better. Several problems can be found in the literature in connection with the preparation of copper alloys: 1. the yield strength of the Cu alloy prepared by the traditional processing technologies of cold rolling, cold drawing and the like is about 500MPa, and the electric conductivity is over 75% IACS, so that the insufficient strength of the Cu alloy faces a severe challenge in the future of high-speed and heavy-duty trains. 2. With the improvement of characterization technology, it has been found that the nano-crystal and nano-twin crystal have significant improvement on material performance, and the adoption of Severe Plastic Deformation (SPD) can introduce the nano-structure, but the nano-structure is unstable at high temperature, which is a problem to be solved urgently. 3. The copper alloy prepared by pulse electrolytic deposition is only suitable for thin film materials, is difficult to form a large block, and has high cost and low efficiency; 4. copper alloys that are Dynamically Plastically Deformed (DPD) are limited by small sample size and high strain rate that are difficult to apply and practically produce. 5. The liquid nitrogen rolling is easy to form a shear band in the alloy, the deformation structure of the alloy is uneven, the rheological behavior of the material is influenced, fine cracks are easy to appear on the surface, and the apparent quality and the application of the alloy are influenced.

In recent years, research on aging strengthening copper alloys for contact lines is very hot, for example, in a Cu-Cr-Zr alloy, the content of alloy elements is usually below 2-3%, and the strength and the conductivity of the alloy are superior. While the cold deformation and aging process during this period is still in the search for optimization. Vinogrodov et al prepared 160nm ultra-fine grain Cu-Cr-Zr alloy by Equal Channel Angular Pressing (ECAP) with pure shear severe plastic deformation, and subsequent aging treatment gave a good match of 700MPa tensile strength and 77% IACS conductivity. At present, the problems of scientific research and technical engineering are still solved by finding a universal structural design method with high strength, high toughness, high strength and high conductivity and developing a preparation process suitable for practical engineering application.

Disclosure of Invention

The invention aims to provide a preparation method of a Cu-Cr-Zr alloy.

The technical scheme for realizing the purpose of the invention is as follows:

a preparation method of a Cu-Cr-Zr alloy comprises the following specific preparation steps:

step 1 solution treatment

And (3) keeping the temperature of the forged square rod at 1000-1050 ℃ for 0.5-2 hours, and then carrying out water quenching at room temperature.

Step 2 equal channel angular extrusion

And putting the copper alloy bar subjected to the solution treatment into a die for 4-12 times of extrusion.

Step 3 Low temperature deformation

Before rolling, soaking the sample extruded at the equal channel angle in liquid nitrogen for 20-40min to ensure that the deformation temperature of the sample is between-150 ℃ and-100 ℃; after each pass is finished, putting the steel plate into liquid nitrogen, preserving heat for 10-20 minutes, and then performing the next pass, wherein the rolling deformation degree is about 80-85%, and the strain speed during rolling is controlled at 1 multiplied by 10^-3～1×10^-2s^-1Left and right.

Step 4 aging treatment

And (3) keeping the temperature of the sample after low-temperature deformation at the temperature of 420-520 ℃ for 0.5-8 hours, and then carrying out air quenching to optimize the precipitation of Cr particles and test the thermal stability of the UFG structure.

Further, the Cu-Cr-Zr alloy comprises the following components in percentage by mass:

Cr：0.3～1.0％

Zr：0.05～0.3％

si: 0.03-0.08%, and the balance of Cu and some inevitable impurity elements in the casting process.

Further, the preparation method of the forged square rod comprises the following steps:

the first step is as follows: melting and casting

Taking pure electrolytic copper, chromium and zirconium, taking alloy components according to the alloy component ratio, and heating the alloy components in a vacuum induction furnace to 1220-1270 ℃ for melting; removing impurities and degassing, standing for 20-40 minutes, and casting to obtain a cast ingot;

the second step is that: homogenization treatment

Heating the ingot to 920-;

the third step: conventional heat distortion

Removing the surface of the ingot after homogenization treatment, putting the ingot into a vacuum heating furnace, heating to 850-900 ℃, and forging into a square rod after hot forging;

further, in the first step, graphite powder and cryolite are mixed and covered on the liquid surface during smelting;

further, the purity of pure electrolytic copper was 99.99%, chromium 99.7% and zirconium 99.7%.

Further, in the step 2, the adopted path is a path "A", namely the next pass is directly carried out without rotating the angle after each extrusion; the 'C' path is rotated by 180 degrees after one pass of extrusion is finished each time; the Ba path is that the sample rotates 90 degrees clockwise and anticlockwise alternately before each extrusion; or "Bc" path, i.e. 90 ° clockwise rotation of the specimen before each compression; wherein, the inner angle of the mold90 degrees, an external angle of 30 degrees, and an extrusion rate limited within 1 mm/s.

Further, in step 3, cold drawing and cold drawing can be performed at the liquid nitrogen temperature.

Compared with the prior art, the invention has the remarkable advantages that: the Cu-Cr-Zr alloy of the invention is subjected to ECAP + LNR + aging treatment to obtain a microstructure which has high-density nanometer twin crystals in part of ultrafine crystals and precipitates phase pinning crystal boundaries. The specific performance parameters are as follows, 1, strength. The tensile strength can be greatly improved by utilizing twin crystal boundary strengthening, precipitation strengthening and ultrafine crystal boundary strengthening. 2. And (4) toughness. The Cu and the alloy thereof with the nanocrystalline structure not only have high strength, but also have good toughness. Due to the existence of the nanometer twin crystal boundary, the strength is greatly improved, and meanwhile, the toughness can be ensured not to be reduced. 3. And (4) conductivity. After ECAP + LNR + aging treatment, the strength of the Cu-Cr-Zr alloy is greatly improved, and the balance of the conductivity is ensured. 4. And (3) thermal stability. After ECAP + LNR + aging treatment, the Cu-Cr-Zr alloy has excellent thermal stability due to the special microstructure, and can still ensure the stability of other properties at high temperature. 5. And (4) processing and forming. The method can be used for large-size block materials, the processing cost is low, the efficiency is high, the surface quality of the obtained sample is good, the finished product has no crack, and the actual production is easy to realize.

Drawings

Figure 1 is the EDS elemental distribution plot of example 1.

Fig. 2 is an EBSD plot of grain size for the (a) original sample and the (b) sample after ECAP + LNR.

FIG. 3 is a TEM image of example 1.

FIG. 4 is a physical diagram of cold rolling with liquid nitrogen after ECAP8 passes.

FIG. 5 is a graph comparing tensile curves of Cu-Cr-Zr alloys.

Detailed Description

The invention is further described with reference to the following figures and examples