A nitrogen-doped copper-chromium-zirconium alloy, its preparation method and application

Abstract

The present invention provides a nitrogen-doped copper-chromium alloy, a preparation method and an application thereof. By completing the smelting, casting and solidification of a copper-chromium-zirconium alloy in a high nitrogen pressure environment, the obtained nitrogen-doped copper-chromium-zirconium alloy has a supersaturated nitrogen content and a strong solid solution strengthening effect, which is beneficial to introducing a large number of deformation twin boundaries into the deformed microstructure during cold deformation at room temperature.

Description

Technical Field

[0001] The present invention belongs to the technical field of copper alloy preparation, and relates to a nitrogen-doped copper-chromium-zirconium alloy, a preparation method thereof and an application thereof. Background Art

[0002] As a kind of electrical material with excellent comprehensive properties, high-strength and high-conductivity copper-chromium-zirconium alloy is widely used in large-scale integrated circuit lead frames, electrical engineering switch conductive contacts, high-pulse magnetic field conductors, electrified railway contact wires, etc. To improve the strength and conductivity of this kind of alloy, methods such as multi-element alloying and precipitation strengthening are generally adopted, among which fine grain strengthening and precipitation strengthening are the main strengthening mechanisms. However, adding too many alloying elements will lead to a decrease in conductivity. The composite material method using in-situ self-generated strengthening phases or externally added reinforcing phases can effectively improve the strength and thermal stability of the alloy, but generally the conductivity is not high, and there is also the problem of high manufacturing cost.

[0003] Therefore, it is very necessary to provide a copper-chromium-zirconium alloy with good alloy strength and thermal stability and low cost. Summary of the Invention

[0004] The purpose of the present invention is to provide a nitrogen-doped copper-chromium alloy, a preparation method thereof and an application thereof. The feature is that the smelting, pouring and solidification of the copper-chromium-zirconium alloy are completed in a high nitrogen pressure environment, and the obtained nitrogen-doped copper-chromium-zirconium alloy has a supersaturated nitrogen content and a strong solid solution strengthening effect, which is beneficial to introducing a large number of deformation twin boundaries into the deformed structure during cold deformation at room temperature.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a nitrogen-doped copper-chromium-zirconium alloy, which includes the following chemical components by mass percentage: the content of chromium element is 0.5% - 2%, the content of zirconium element is 0.1% - 0.4%, the doping amount of nitrogen element is 5 ppm - 20 ppm, and the rest is copper.

[0007] The present invention also provides a preparation method of the above nitrogen-doped copper-chromium-zirconium alloy. The preparation method includes: taking raw materials of copper, chromium and zirconium for mixing to obtain a mixed material; after subjecting the mixed material to a vacuum treatment, filling it with nitrogen to positive pressure; then subjecting the mixed material to a melting treatment, and continuously melting the mixed material under the condition of continuously blowing nitrogen after the mixed material is completely melted to obtain a molten copper alloy liquid; placing the molten copper alloy liquid in a mold, and completing the pouring and cooling solidification treatment in a high-pressure nitrogen environment to obtain an alloy block; and taking out the alloy block after it cools to room temperature to obtain a cast nitrogen-doped copper-chromium-zirconium alloy ingot; performing a homogenization treatment on the cast nitrogen-doped copper-chromium-zirconium alloy ingot, and performing a water quenching treatment after heat preservation treatment to obtain the nitrogen-doped copper-chromium-zirconium alloy.

[0008] Further, the preparation method specifically includes the following steps: (1) Select bulk materials of high-purity pure copper, copper-chromium master alloy or chromium nitride, and high-purity pure zirconium, and put them into a graphite crucible according to the composition requirements in proportion to obtain a mixed material; (2) Place the graphite crucible containing the mixed material in a vacuum induction furnace, and evacuate to 1×10 -5 MPa, and then fill with high-purity nitrogen to a positive pressure of >0.2 MPa; (3) Melt the mixed material at a melting temperature of 1200 °C to 1600 °C until it is completely melted, and continuously blow high-purity nitrogen into the molten copper alloy from the bottom of the crucible, keep melting and continue melting for 0.5 to 1 hour to obtain a molten copper alloy liquid; (4) Quickly pour the molten copper alloy liquid into a cast iron mold placed in the melting furnace, and complete the pouring and cooling and solidification treatment in a high-pressure nitrogen environment to obtain an alloy block; and take it out after the alloy block cools to room temperature to obtain a as-cast nitrogen-doped copper-chromium-zirconium alloy ingot; (5) Place the as-cast nitrogen-doped copper-chromium-zirconium alloy ingot in a vacuum heat treatment furnace for homogenization treatment, with a holding temperature of 980 °C to 1000 °C, and perform water quenching after holding for 2 hours to obtain the nitrogen-doped copper-chromium-zirconium alloy.

[0009] Further, in step (1), the high-purity pure copper is a copper raw material with a purity reaching 99.99%; the high-purity pure zirconium is a zirconium raw material with a purity reaching 99.99%. In addition, it should be noted that in the mixed material, the input mass ratio of high-purity pure copper, copper-chromium master alloy or chromium nitride, and high-purity pure zirconium is obtained by calculation according to the alloy chemical composition.

[0010] Further, in step (2), the high-purity nitrogen is filled to a positive pressure range of 0.2 MPa to 1.0 MPa.

[0011] The present invention also provides the application of the above-mentioned nitrogen-doped copper-chromium-zirconium alloy in the field of electrical engineering materials.

[0012] Compared with the prior art, the technical solution provided by the present invention has at least the following advantages:

[0013] The present invention increases the nitrogen partial pressure to increase the solid solubility of nitrogen element in the copper alloy melt. At the same time, the alloy is smelted, poured, and solidified in a high-nitrogen environment, and then a nitrogen-doped copper-chromium-zirconium alloy with a supersaturated nitrogen content is obtained.

[0014] 1. Using cheap and abundant nitrogen element to replace expensive elements such as zirconium (Zr) and hafnium (Hf) for microalloying can significantly reduce the cost of copper alloy.

[0015] 2. In the nitrogen-doped copper-chromium-zirconium obtained by the high-pressure metallurgy method, the nitrogen content is much higher than the equilibrium nitrogen content, and it has a stronger solid solution strengthening effect.

[0016] 3. Nitrogen has a stronger effect of reducing stacking fault energy and is expected to obtain a high proportion of deformation twin boundaries in the deformed microstructure at room temperature. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] One or more embodiments are exemplarily illustrated by the pictures in the corresponding drawings. These exemplary illustrations do not constitute a limitation on the embodiments. Unless otherwise stated, the figures in the drawings do not constitute a scale limitation.

[0018] Figure 1 is the alloy material diagram of the nitrogen-doped copper-chromium-zirconium alloy obtained in the embodiment of the present invention;

[0019] Figure 2 is the metallographic structure diagram of the nitrogen-doped copper-chromium-zirconium alloy obtained in the embodiment of the invention;

[0020] Figure 3 is the metallographic structure diagram of the nitrogen-doped copper-chromium-zirconium alloy after aging treatment at 500 °C in the embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0021] The inventors have found that in recent years, high-strength and high-conductivity copper alloys obtained based on the twin boundary strengthening mechanism are considered the most effective technical approach. For example, electrodeposition is used to prepare pure copper with nano-twins, obtaining ultra-high strength and high electrical conductivity. However, such methods are limited by conditions and cannot be applied in production. Since copper alloys have medium stacking fault energy, it is difficult to obtain a high proportion of twin boundaries in the microstructure by conventional industrial deformation means. Although severe plastic deformation at ultra-low temperature and high strain rate can obtain a certain proportion of twin boundary microstructure, the harsh deformation conditions limit industrial applications. Alloying with noble metal elements zirconium (Zr) and hafnium (Hf) can reduce the stacking fault energy of copper alloys and increase the proportion of twin boundaries in the microstructure. However, to obtain a high proportion of twin boundaries, low temperature and high strain rate conditions are still required, making it difficult to achieve industrial applications. Nitrogen alloying can significantly reduce the stacking fault energy of copper alloys, which has been confirmed by theoretical calculations. It is expected to introduce deformation twin boundaries into copper alloys at room temperature through industrial methods using nitrogen alloying. However, due to the extremely low solubility of nitrogen in high-temperature copper liquid under normal pressure (≤2 ppm), it is impossible to obtain nitrogen-containing copper alloys by various smelting methods under general vacuum and normal pressure.

[0022] In view of the application requirements of nitrogen-containing copper-chromium alloys and the problems existing in the existing preparation methods, the present invention proposes to use high-pressure metallurgy methods to obtain nitrogen-doped copper alloys. Through reasonable matching of the contents of chromium and zirconium, the smelting, casting, and solidification of nitrogen-doped copper alloys are realized in a nitrogen environment at several times atmospheric pressure.

[0023] The present invention will be described in detail below in conjunction with the specific embodiments.

[0024] Example 1

[0025] This embodiment provides a nitrogen-doped copper-chromium-zirconium alloy and a preparation method thereof. The preparation method includes:

[0026] Smelt according to the following copper-chromium-zirconium alloy composition (mass percentage): 0.44% Cr, 0.1% Zr, and the rest is Cu. By calculating the alloy material ratio, determine the addition amounts of pure copper, copper-chromium master alloy, and pure zirconium in a 2-kg ingot. The melting is carried out using a special induction furnace for high-pressure metallurgy. Place various proportioned metal materials in a graphite crucible, evacuate to 1×10 -5 MPa, and then fill with high-purity nitrogen to a positive pressure of 0.8 MPa. Then heat the crucible to 1450 °C. After the alloy materials are completely melted, continuously blow high-purity nitrogen into the molten copper alloy from the bottom of the crucible, and keep melting under the above conditions for 1 hour. Pour the molten copper alloy liquid quickly into a cast iron mold placed in the melting furnace, and complete cooling and solidification in the melting furnace under nitrogen positive pressure. After the ingot cools to room temperature, open the furnace door and take out the ingot. Place the ingot in a vacuum heat treatment furnace for homogenization treatment. The holding temperature is 980 °C, and the holding time is 2 hours. Then take it out and quench in water to obtain the nitrogen-doped copper-chromium-zirconium alloy.

[0027] The nitrogen-doped copper-chromium-zirconium alloy after water quenching is as Figure 1 shown, and the metallographic structure of the nitrogen-doped copper-chromium-zirconium alloy is as Figure 2 shown. It can be seen therefrom that the copper-chromium-zirconium alloy obtained by high-pressure metallurgy has a dense structure, and no defects such as surface cracks and internal pores are found. This new copper alloy smelting method is completely feasible.

[0028] Through chemical composition analysis, the nitrogen content in the ingot is 8 ppm. To verify the effect of nitrogen doping on reducing the stacking fault energy, the obtained nitrogen-doped copper-chromium-zirconium alloy was cold-rolled at 90% at room temperature and aged at 500 °C. The obtained alloy metallographic structure is as Figure 3 shown. A large number of twin boundaries can be seen in the aged structure, which indicates that nitrogen doping does promote the formation of twin boundaries in the copper-chromium-zirconium structure. In contrast, it is difficult for general pure copper and copper alloys to obtain a large number of deformation twins by rolling at room temperature.

[0029] Those of ordinary skill in the art can understand that the above embodiments are specific embodiments for implementing the present application. In actual applications, various changes can be made in form and details without departing from the spirit and scope of the present application. Any person skilled in the art can make their respective changes and modifications without departing from the spirit and scope of the present application. Therefore, the protection scope of the present application should be subject to the scope defined by the claims.

Claims

1. A nitrogen-doped copper-chromium-zirconium alloy, characterized in that, The nitrogen-doped copper-chromium-zirconium alloy comprises the following chemical components by mass percentage: the chromium element content is 0.5% to 2%, the zirconium element content is 0.1% to 0.4%, the doping amount of nitrogen element is 5 ppm to 20 ppm, and the rest is copper; The preparation method of the nitrogen-doped copper-chromium-zirconium alloy comprises: taking raw materials of copper, chromium and zirconium for mixing to obtain a mixed material; after subjecting the mixed material to a vacuum treatment, filling it with nitrogen gas to a positive pressure; then subjecting the mixed material to a melting treatment, and continuously melting the mixed material under the condition of continuously blowing nitrogen gas after the mixed material is completely melted to obtain a molten copper alloy liquid; placing the molten copper alloy liquid in a mold, and completing pouring and cooling and solidification treatment in a high-pressure nitrogen environment to obtain an alloy block; and taking out the alloy block when it is cooled to room temperature to obtain a as-cast nitrogen-doped copper-chromium-zirconium alloy ingot; subjecting the as-cast nitrogen-doped copper-chromium-zirconium alloy ingot to a homogenization treatment, and performing water quenching treatment after heat preservation treatment to obtain the nitrogen-doped copper-chromium-zirconium alloy.

2. The preparation method of the nitrogen-doped copper-chromium-zirconium alloy according to claim 1, characterized in that, The preparation method specifically comprises the following steps: (1) Selecting high-purity pure copper, copper-chromium master alloy or chromium nitride, and high-purity pure zirconium ingots, putting them into a graphite crucible for mixing to obtain a mixed material; (2) Place the graphite crucible containing the mixture in a vacuum induction furnace and evacuate to 1×10 -5 MPa, and then fill with high-purity nitrogen to a positive pressure of >0.2 MPa; (3) Melting the mixed material at a melting temperature of 1200 °C to 1600 °C until it is completely melted, and continuously blowing high-purity nitrogen gas into the molten copper alloy from the bottom of the crucible, maintaining and continuously melting for 0.5 to 1 hour to obtain a molten copper alloy liquid; (4) Rapidly pouring the molten copper alloy liquid into a cast iron mold placed in a melting furnace, and completing pouring and cooling and solidification treatment in a high-pressure nitrogen environment to obtain an alloy block; and taking out the alloy block when it is cooled to room temperature to obtain a as-cast nitrogen-doped copper-chromium-zirconium alloy ingot; (5) Placing the as-cast nitrogen-doped copper-chromium-zirconium alloy ingot in a vacuum heat treatment furnace for homogenization treatment, with a heat preservation temperature of 980 °C to 1000 °C, performing water quenching after heat preservation for 2 hours to obtain the nitrogen-doped copper-chromium-zirconium alloy.

3. The preparation method of the nitrogen-doped copper-chromium-zirconium alloy according to claim 2, characterized in that, In step (1), the high-purity pure copper is a copper raw material with a purity reaching 99.99%; the high-purity pure zirconium is a zirconium raw material with a purity reaching 99.99%.

4. The preparation method of the nitrogen-doped copper-chromium-zirconium alloy according to claim 2, wherein, In step (2), the range of filling high-purity nitrogen gas to a positive pressure is greater than 0.2 MPa and less than or equal to 1.0 MPa.

5. Application of the nitrogen-doped copper-chromium-zirconium alloy according to claim 1 in the field of electrical engineering materials.

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