CN113414548A - Preparation method of large-size high-strength high-conductivity CuCr alloy with ultrafine crystal structure - Google Patents

Abstract

The preparation method of the large-size high-strength high-conductivity CuCr alloy with the ultrafine crystal structure comprises the following steps: firstly, carrying out heat treatment on a Cu-0.4Cr alloy, and then carrying out water quenching; step (2) processing the CuCr alloy treated in the step (1) by adopting a Bc path of an ECAP-Conform technology; step (3) cutting the sample obtained in the step (2) into a plurality of groups of plates with the same length and width by using a wire cut electric discharge machine; and (4) rolling the plate obtained in the step (3) on a cold and hot double-roller mill at ultralow temperature with preset deformation.

Description

Preparation method of large-size high-strength high-conductivity CuCr alloy with ultrafine crystal structure

Technical Field

The invention relates to a preparation technology of ultra-fine grain high-strength high-conductivity CuCr alloy.

Background

The Cu-Cr alloy has excellent comprehensive physical property and mechanical property, and has great application value in the fields of lead frames of integrated circuits, various electrodes, electric contacts and the like. However, with the rapid development of the national economic industry, more severe requirements are put forward on the comprehensive properties of the Cu-Cr alloy in the high and new technology fields, and most typically, in the application of the lead frame of the very large scale integrated circuit and the contact line wire of the high speed electrified railway, the Cu-Cr alloy is required to have higher strength and good plasticity in addition to ensuring the original good physical properties of the Cu-Cr alloy, for example, in order to ensure that the Cu-Cr alloy has sufficient durability and reliability in working, the strength of the Cu-Cr alloy is required to reach 600 MPa, the hardness is greater than 130 HV, the electrical conductivity is not lower than 80% IACS, and the Cu-Cr alloy is required to have good thermal conductivity, but in the industrial production, the strength and the plasticity of the Cu-Cr alloy are difficult to simultaneously reach higher standards. Therefore, how to improve the strength of the Cu-Cr alloy as much as possible on the premise of ensuring the high conductivity of the Cu-Cr alloy so as to obtain the Cu-Cr alloy with excellent comprehensive performance is a research hotspot of the high-performance Cu-Cr alloy at present.

The preparation method adopted by the Cu-Cr alloy is mainly large plastic deformation (SPD), and the common deformation method comprises the following steps: high pressure torsional deformation, multidirectional forging, reciprocating extrusion, cumulative pack rolling, repeated bending and straightening and equal channel angular Extrusion (ECAP). At present, in all the preparation technologies of the Cu-Cr alloy with the nano structure, from the aspects of the intensity of shear deformation, the complexity of the process, the application range of the material and the refining effect of crystal grains, the ECAP is one of the most effective preparation processes of the ultrafine grain Cu-Cr alloy material, and has the greatest development potential of large-scale industrial production. The continuous nature of the ECAP-Conform process, in turn, makes it possible to process UFG metal materials of large size. The existing data show that ECAP-Conform can effectively refine grains and improve the tensile strength of metal. But the deformation process increases the strength of the metal material in a manner that sacrifices ductility. On the other hand, such severe deformation usually results in a significant decrease in conductivity. Therefore, it is necessary to obtain a high-strength and high-conductivity Cu — Cr alloy having an ultra-fine grain size by a subsequent processing process such as rolling.

Disclosure of Invention

The invention aims to provide a preparation method of a large-size high-strength high-conductivity CuCr alloy with an ultrafine crystal structure.

The invention relates to a preparation method of a large-size high-strength high-conductivity CuCr alloy with an ultrafine crystal structure, which comprises the following steps:

firstly, carrying out heat treatment on a Cu-0.4Cr alloy, and then carrying out water quenching;

step (2) processing the CuCr alloy treated in the step (1) by adopting a Bc path of an ECAP-Conform technology;

step (3) cutting the sample obtained in the step (2) into a plurality of groups of plates with the same length and width by using a wire cut electric discharge machine;

and (4) rolling the plate obtained in the step (3) on a cold and hot double-roller mill at ultralow temperature with preset deformation.

The invention has the beneficial effects that: 1. the preparation process is continuous, the cost is low, the process flow is simple, and the yield is high;

2. after the alloy is rolled at the ultralow temperature, crystal grains of the alloy become fine and uniform, and the strength is greatly improved. When the rolling deformation was 90%, the average size of the crystal grains was reduced to 1 μm or less, the microhardness was 156 HV, the electric conductivity was 68% IACS, the tensile strength was 572.4 MPa, and the elongation was 11.19%.

Drawings

FIG. 1 is a schematic diagram of the processing of CuCr alloy prepared by the present invention, FIG. 2 is a TEM image of CuCr alloy obtained in example 3 of the present invention, and FIG. 3 is a tensile strength curve diagram of CuCr alloy prepared by the present invention.

Detailed Description

The invention relates to a preparation method of a large-size high-strength high-conductivity CuCr alloy with an ultrafine crystal structure, which comprises the following steps as shown in figure 1:

firstly, carrying out heat treatment on a Cu-0.4Cr alloy, and then carrying out water quenching;

step (2) processing the CuCr alloy treated in the step (1) by adopting a Bc path of an ECAP-Conform technology;

step (3) cutting the sample obtained in the step (2) into a plurality of groups of plates with the same length and width by using a wire cut electric discharge machine;

and (4) rolling the plate obtained in the step (3) on a cold and hot double-roller mill at ultralow temperature with preset deformation.

In the preparation method, the heat treatment process in the step (1) is carried out for 1 h at 1000 ℃.

In the preparation method, the ECAP-format Bc path in step (2) is that a sample is placed into one of two channels with the same cross section and intersecting into an L-shaped die, the sample is pressed downwards under the action of pressure P, the sample is extruded out from the other channel port, the sample is rotated 90 degrees clockwise or anticlockwise in the same direction between each pass, and the sample needs to be processed at 200 ℃ for 4 passes.

In the above production method, the cutting direction in the step (3) is an ECAP-Conform processing direction.

According to the preparation method, the ultralow temperature rolling temperature in the step (4) is liquid nitrogen temperature, namely-196 ℃, and the deformation amounts are 50%, 70% and 90%;

soaking in liquid nitrogen for about 20 min before the first pass of rolling, and soaking in liquid nitrogen for 5 min before each subsequent pass of rolling, wherein the reduction amount of each pass is 10% of the initial thickness until the deformation amounts are 50%, 70% and 90%;

in the rolling process, the rolled piece is immediately soaked in liquid nitrogen after each pass of rolling is finished, and the rolling process of each pass is guaranteed to be finished within 10 s.

The following are specific examples of the present invention, and the technical solutions of the present invention will be further described with reference to the examples, but the present invention is not limited to the examples.

Example 1:

the alloy used in this example was a Cu-0.4Cr alloy. The method comprises the following specific steps:

(1) firstly, the Cu-0.4Cr alloy is subjected to heat preservation for 1 h at 1000 ℃, and then water quenching is carried out;

(2) placing the sample treated in the step (1) into one of 2 channels with the same cross section, intersecting into an L-shaped die, extruding downwards under the action of pressure P, extruding the sample out of the other channel port, rotating 90 degrees in the same direction (clockwise or anticlockwise) between each pass, wherein the process is called an ECAP-Conform Bc path, processing 4 passes at 200 ℃, and the sample is a bar with a square cross section (15 mm multiplied by 15 mm) before and after processing;

(3) cutting the sample obtained in the step (2) into a plurality of groups of plates with the same length and width by using a wire cut electrical discharge machine, wherein the length direction is the ECAP-Conform processing direction;

(4) and (4) carrying out ultralow-temperature rolling on the plate obtained in the step (3) with deformation of 50% on a cold and hot double-roller mill, soaking in liquid nitrogen (-196 ℃) for about 20 min before rolling, soaking in liquid nitrogen for 5 min before each subsequent rolling, wherein the pressing amount of each pass is 10% of the initial thickness until the deformation is 50%. In the low-temperature rolling process, the rolled piece is immediately soaked in liquid nitrogen after each pass of rolling is finished, and the rolling process of each pass is guaranteed to be finished within 10 s.

FIG. 2 is a TEM image of the CuCr alloy obtained in example 3, and it can be seen that a large number of dislocations exist around the grain boundaries, i.e., the dislocation density of the alloy after rolling deformation is significantly increased, and ultrafine grains appear; FIG. 3 is a stress-strain curve of the alloy obtained by the present invention, and it can be seen that the strength of the alloy is significantly increased after rolling deformation, and the strength is gradually increased with the increase of the rolling deformation; table 1 shows the mechanical and electrical properties of the alloy, and it can be seen that the electrical conductivity is reduced after rolling, but the rolling deformation does not greatly affect the electrical conductivity, the hardness shows a rule consistent with the strength result, and the elongation of the alloy is maintained at about 9%.

Example 2:

this embodiment is different from example 1 in that the rolling deformation amount in step (4) is 70%, the rolling reduction amount per pass is 10% of the initial thickness, and the deformation amount is 70%, and the other steps are the same as example 1.

Example 3:

this embodiment is different from example 1 or 2 in that the rolling deformation amount in step (4) is 90%, the rolling reduction amount per pass is 10% of the initial thickness until the deformation amount becomes 90%, and the other steps are the same as example 1 or 2.

Table 1 shows the mechanical and electrical properties of the CuCr alloy prepared according to the present invention:

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Claims (5)

1. the preparation method of the large-size high-strength high-conductivity CuCr alloy with the ultrafine crystal structure is characterized by comprising the following steps:

firstly, carrying out heat treatment on a Cu-0.4Cr alloy, and then carrying out water quenching;

step (2) processing the CuCr alloy treated in the step (1) by adopting a Bc path of an ECAP-Conform technology;

step (3) cutting the sample obtained in the step (2) into a plurality of groups of plates with the same length and width by using a wire cut electric discharge machine;

and (4) rolling the plate obtained in the step (3) on a cold and hot double-roller mill at ultralow temperature with preset deformation.

2. The method for preparing ultra-fine grained high-strength high-conductivity CuCr alloy according to claim 1, wherein the heat treatment process in step (1) is performed at 1000 ℃ for 1 hour.

3. The method for preparing ultra-fine grain high-strength high-conductivity CuCr alloy according to claim 1, wherein the ECAP-Conform Bc path in step (2) is that a sample is placed into one of two channels with the same cross section, which are intersected into an L-shaped die, and is pressed downwards under the action of pressure P, and the sample is extruded out of the other channel opening, and is rotated 90 degrees clockwise or counterclockwise in the same direction between each pass, and the sample is processed at 200 ℃ for 4 passes.

4. The method for preparing ultra-fine grained high-strength high-conductivity CuCr alloy according to claim 1, wherein the cutting direction in the step (3) is ECAP-Conform processing direction.

5. The method for preparing the ultra-fine grained high-strength high-conductivity CuCr alloy according to claim 1, wherein the ultra-low temperature rolling temperature in the step (4) is liquid nitrogen temperature, namely-196 ℃, and the deformation is 50%, 70% or 90%;

soaking in liquid nitrogen for about 20 min before the first pass of rolling, and soaking in liquid nitrogen for 5 min before each subsequent pass of rolling, wherein the reduction amount of each pass is 10% of the initial thickness until the deformation amounts are 50%, 70% and 90%;

in the rolling process, the rolled piece is immediately soaked in liquid nitrogen after each pass of rolling is finished, and the rolling process of each pass is guaranteed to be finished within 10 s.

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