CN101635185B - A kind of preparation method of non/low magnetic cubic texture Ni-W alloy substrate - Google Patents

Abstract

The invention belong to the field of metal base bands with high-temperature super conduction coating conductor textures. The method comprises the following steps: obtaining initial billet ingots by a powder metallurgy method, wherein the W element of initial billet is not uniformly distributed; processing the initial ingots by cold rolling and optimized high-temperature thermal treatment to obtain the metal base band by the diffusion of the W element from an core layer to an outer layer, wherein the obtained metal base band has high strength non/low magnetism and high cubic texture content and the W content of the obtained metal base band is 7-9.3at percent The method is simple and feasible, and the prepared Ni-W alloy base band has favorable surface quality and sharp cubic texture and can be directly used for extensionally growing transitional layers and superconductive layers; and meanwhile, the Ni-W alloy base band has no (low) magnetism in a liquid nitrogen temperature zone and high mechanical strength, and can meet and further improve the requirement of the YBCO coating conductor performance.

Description

A kind of preparation method of non/low magnetic cubic texture Ni-W alloy substrate

technical field

The invention relates to a method for preparing a nonmagnetic (or low magnetic) cubic textured nickel-tungsten (Ni-W) alloy baseband, and belongs to the technical field of high-temperature superconducting coating conductor textured metal basebands.

Background technique

Since the discovery of the second-generation high-temperature superconducting coated conductor, it has attracted widespread attention due to its excellent performance. In practical research, it is an effective idea to epitaxially grow it on a polycrystalline ductile metal substrate. The preparation of textured metal substrates is one of the keys to obtain high-performance coated conductors.

At present, the materials used in coated conductor textured metal substrates are mainly pure Ni and Ni alloys. Worldwide, Ni-5at.%W (Ni5W) alloy metal substrates at the level of 100 meters have been commercially produced by several companies. However, due to the high Curie transition temperature of the Ni5W alloy, it still has ferromagnetism when applied at 77K (the working temperature range of the coated conductor), which will increase the AC loss during the transmission of alternating current and reduce the performance of the coated conductor, and Ni5W The mechanical strength of the metal substrate needs to be further improved. This greatly limits the practical application of coated conductors. The increase of W content will greatly improve the mechanical strength of the NiW alloy base band and reduce the Curie transition temperature of the base band. When the W content is 9.3% at.%, the Curie temperature is reduced to below 77K, making the coated conductor in its application. AC loss is eliminated when used at the highest temperature (77K). However, with the increase of W content, the stacking fault energy of the alloy gradually decreases, making the formation of cubic texture very difficult.

Contents of the invention

The purpose of the present invention is to provide a kind of preparation high strength, non-magnetic (low magnetic), the surface has high {001}<100> cubic texture, can be used for the NiW alloy substrate of follow-up epitaxial growth oxide process layer and superconducting layer Methods.

In the present invention, the initial ingot with uneven distribution of W element is obtained by adopting the powder metallurgy method, and after cold rolling and optimized high-temperature heat treatment, the W element diffuses from the core layer to the outer layer to obtain a high-strength surface W content of 7-9.3 at.%. , a metal substrate with no (low) magnetic properties and high cubic texture content, specifically comprising the following steps:

1) In a protective atmosphere, mix Ni powder with a purity of 99.9% and W powder with a purity of 99.9% according to the fact that W atoms account for 9% to 12% of the total number of Ni atoms and W atoms, and ball mill for 2 to 4 hours to obtain high W alloy powder; in a protective atmosphere, mix Ni powder with a purity of 99.9 and W powder with a purity of 99.9 according to the fact that W atoms account for 5% to 7% of the total number of Ni atoms and W atoms, and ball mill for 2 to 4 hours to obtain low W alloy powder; put high W alloy powder and low W alloy powder into the mold for pressing in the order of low W alloy powder-high W alloy powder-low W alloy powder, low W alloy powder-high W alloy powder-low W alloy The volume ratio of the powder is 1:1~3:1, and then the initial ingot is prepared by spark plasma sintering, the sintering temperature is 800-1000°C, and the sintering time is 3-8min;

2) Cold-rolling the initial billet, the deformation of each pass is less than 5%, and the total deformation is greater than 99%, and finally a cold-rolled base strip with a thickness of 50 μm to 100 μm is obtained;

3) The cold-rolled base strip is subjected to graded heat treatment in a protective atmosphere. First, a low-temperature nucleation heat treatment is performed between 650°C and 750°C for 30 minutes to preferentially form cubic nuclei, and then it is raised to 1100°C to 1200°C for 30 minutes. ~60 minutes of cubic grain growth heat treatment, the temperature is raised to 1300 ℃ ~ 1450 ℃ for 60 minutes ~ 240 minutes of solute diffusion treatment, so that W atoms can be fully diffused, and the W atomic percentage of the outer layer is 7 ~ 9.3 at. % Ni-W alloy, N-Wi alloy substrate with high strength, no (low) magnetism and sharp cubic texture.

Wherein, the protective atmosphere is a mixed gas of Ar and H ₂ , and the volume fraction of H ₂ in the mixed gas is 4%.

The core technology of the present invention is to first use the characteristics that the NiW alloy with low W content in the outer layer is easy to form a cubic texture. During the heat treatment process, a sharp cubic texture is first formed, and then the solute is diffused through a high temperature or a long time high temperature heat treatment. The method diffuses the W atoms in the inner high-W layer to the outer low-W layer to increase the W content of the outer layer, reduce the overall magnetic properties of the baseband, and ensure the cubic texture content of the outer layer. Another core technology of the present invention is to control the volume ratio of the inner and outer alloy powders. The thickness of the outer alloy directly affects the diffusion efficiency of the inner W element and the subsequent solute diffusion heat treatment process. If the outer layer is too thick, solute diffusion to the outer layer requires a higher heat treatment temperature or longer time, which will cause thermal corrosion on the surface of the baseband, which is not conducive to the growth of the subsequent epitaxial transition layer; if the outer layer is too thin, the cubic texture of the outer layer will nucleate and grow The diffusion of W atoms in the inner layer will affect the formation of the cubic texture in the outer layer. Therefore, the ratio of the inner and outer layers of the initial billet and the solute diffusion heat treatment process should be taken into account at the same time.

The present invention has the following beneficial effects:

Compared with the existing technology of preparing Ni-W alloy base strip with high W content (>7 at.%) by warm rolling process, the Ni-W alloy base strip prepared by the method of the present invention has good surface quality and sharp cubic texture, which can The transition layer and the superconducting layer are grown epitaxially directly. At the same time, because this Ni-W alloy base strip has no (low) magnetism in the liquid nitrogen temperature zone and has high mechanical strength, it can meet the requirements of further improving the performance of YBCO coated conductors; at the same time, compared with warm rolling, cold rolling is adopted. The rolling method can simplify the rolling process and realize industrialization easily.

Description of drawings

Fig. 1, the cross-sectional backscatter diagram of the cold-rolled base strip in Example 1.

Figure 2, the (111) pole figure of the baseband in Embodiment 1.

Fig. 3, the cross-sectional backscatter diagram of the cold-rolled base strip in Examples 2 and 3.

Fig. 4, the (111) pole figure of the baseband in embodiment 2.

Fig. 5, the (111) pole figure of the baseband in embodiment 3.

The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

Detailed ways

Example 1

1) In a protective atmosphere (Ar-4%H ₂ ), Ni powder with a purity of 99.9 and W powder with a purity of 99.9 were ball-milled for 3 hours according to the atomic ratios of Ni and W of 95:5 and 91:9, respectively, to obtain High W alloy powder and low W alloy powder; put high W alloy powder and low W alloy powder into the mold in the order of low W-high W-low W for pressing, low W alloy powder-high W alloy powder-low W alloy The volume ratio of the powder is 1:3:1, and then the spark plasma sintering technology is used to sinter at 800°C for 5 minutes to obtain the initial billet;

2) cold-rolling the initial ingot, with a pass deformation of 5%, and a total deformation of 99%, to finally obtain a 75 μm thick cold-rolled base strip (see Figure 1);

3) The cold-rolled base strip is subjected to graded heat treatment in a protective atmosphere (Ar-4%H ₂ ), first at 650°C for 30 minutes, then at 1100°C for 30 minutes, and then at 1450°C for 60 minutes to obtain no/ Low magnetic cubic texture Ni-W alloy substrate.

The atomic percentage of W in the outer layer of the baseband is 7%, and its (111) surface pole figure is shown in Figure 2. The cubic texture content is 99%. Since the baseband has undergone diffusion treatment, the W content of the surface layer has increased from 5% to 7%. The overall magnetic performance of the baseband is greatly reduced, while ensuring a high cubic texture content.

Example 2

1) In a protective atmosphere (Ar-4%H ₂ ), Ni powder with a purity of 99.9 and W powder with a purity of 99.9 were ball milled for 2 h according to the atomic ratio of Ni and W of 93:7 and 89:11, respectively, to obtain High W alloy powder and low W alloy powder; put high W alloy powder and low W alloy powder into the mold in the order of low W-high W-low W for pressing, low W alloy powder-high W alloy powder-low W alloy The volume ratio of the powder is 1:1:1, and then the spark plasma sintering technology is used to sinter at 800°C for 5 minutes to obtain the initial billet;

2) cold-rolling the initial ingot, with a pass deformation of 5%, and a total deformation of 99%, to finally obtain a 75 μm thick cold-rolled base strip (see Figure 3);

3) The cold-rolled base strip is subjected to graded heat treatment in a protective atmosphere (Ar-4%H ₂ ), first at 700°C for 30 minutes, then at 1200°C for 60 minutes, and then at 1400°C for 180 minutes to obtain no/ Low magnetic cubic texture Ni-W alloy substrate.

The W atomic percentage of the outer layer of the baseband is 8%, and its (111) surface pole figure is shown in Figure 4, and the cubic texture content is 99%. The W content of the surface layer is increased from 7% to 8.7% due to the diffusion treatment of the baseband. The overall magnetic performance of the baseband is greatly reduced, while ensuring a high cubic texture content.

Example 3

1) In a protective atmosphere (Ar-4% _H2 ), Ni powder with a purity of 99.9 and W powder with a purity of 99.9 were ball-milled for 4 hours according to the atomic ratio of Ni and W of 93:7 and 88:12, respectively, to obtain High W alloy powder and low W alloy powder; put high W alloy powder and low W alloy powder into the mold in the order of low W-high W-low W for pressing, low W alloy powder-high W alloy powder-low W alloy The volume ratio of the powder is 1:1:1, and then the spark plasma sintering technology is used to sinter at 800°C for 5 minutes to obtain the initial billet;

2) cold-rolling the initial ingot, with a pass deformation of 5%, and a total deformation of 99%, to finally obtain a 75 μm thick cold-rolled base strip (see Figure 3);

3) The cold-rolled base strip is subjected to graded heat treatment in a protective atmosphere (Ar-4%H ₂ ), first at 700°C for 30 minutes, then at 1200°C for 60 minutes, and then at 1400°C for 180 minutes to obtain no/ Low magnetic cubic texture Ni-W alloy substrate.

The W atomic percentage of the outer layer of the baseband is 9%, and its (111) surface pole figure is shown in Figure 5. It can be seen that a sharp cubic texture is formed on the surface, and the W content of the surface layer increases from 7% due to the diffusion treatment of the baseband. To 9%, the Curie transition temperature of the baseband is lowered to below 77K, which eliminates the AC loss of the coated conductor during the power transmission process, and at the same time ensures a high content of cubic texture, which is beneficial to the growth of the subsequent epitaxial film.

Claims (2)

1. the preparation method of a Ni-W alloy base band with non/low magnetic cubic texture is characterized in that, may further comprise the steps:

1) in protective atmosphere, be 99.9% Ni powder and purity after to be 99.9% W powder according to the W atom account for 9%～12% of Ni atom and W total atom number and mix with purity, ball milling 2～4h obtains high W alloy powder; In protective atmosphere, be 99.9 Ni powder and purity after to be 99.9 W powder according to the W atom account for 5%～7% of Ni atom and W total atom number and mix with purity, ball milling 2～4h obtains low W alloy powder; High W alloy powder and low W alloy powder packed into according to the order of low W alloy powder-Gao W alloy powder-low W alloy powder suppress in the mould, the volume ratio of low W alloy powder-Gao W alloy powder-low W alloy powder is 1: 1～3: 1, and after discharge plasma sintering prepares initial billet, sintering temperature is 800-1000 ℃, sintering time 3-8min;

2) initial billet is carried out cold rolling, pass deformation is less than 5%, and total deformation finally obtains the cold rolling base band that 50 μ m～100 μ m are thick greater than 99%;

3) cold rolling base band is carried out stepped thermal treatment in protective atmosphere; at first at 650 ℃～750 ℃ insulation 30min; after being warming up to 1100 ℃～1200 ℃ insulation 30min～60min then temperature is risen to 1300 ℃～1450 ℃ insulation 60min～240min, obtain Ni-W alloy base band with non/low magnetic cubic texture.

2. method according to claim 1 is characterized in that, described protective atmosphere is Ar and H ₂Mist, in the mist, H ₂Percent by volume be 4%.

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