RU2451766C1 - Method for biaxial textured substrate production from binary alloy on basis of nickel for epitaxial application of buffer and high-temperature superconductive layers for ribbon superconductors to substrate - Google Patents

Abstract

FIELD: metallurgy.

SUBSTANCE: invention relates to metallurgy, more particularly, to methods of biaxially textured substrates production. A method for biaxial textured substrate production from binary alloy on basis of nickel for epitaxial application of buffer and high-temperature superconductive layers for ribbon superconductors to the substrate is disclosed. The method includes melting, forging, cold rolling to deformation ratio of ≥97% and recrystallisation annealing at the temperature of ≥1000°C. The following alloy is used as binary alloy on basis of nickel: rhenium ≤7 % atm, the rest is nickel.

EFFECT: high degree of texturisation and strength as well as high chemical stability is obtained.

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Description

The invention relates to metallurgy, in particular to methods for producing biaxially textured substrates. The biaxially textured substrate serves as the basis for the epitaxial deposition of buffer and high-temperature superconducting (HTSC) layers on it in order to obtain high critical current values in the finished tape superconducting composite. The finished multilayer tape can be used to transfer electricity with the least loss, create strong magnetic fields in helium-free HTSC solenoids, to design energy-efficient products with improved mass and size characteristics for the electric power industry and other sectors of the economy.

The problem of obtaining metal substrate tapes with a high degree of perfection of the cubic texture {100} <001> arose in the late 90s in connection with the advent of the technology for producing second-generation high-temperature superconductors (HTSCs) based on the epitaxial deposition of ceramic HTSCs through buffer layers on textured metal substrate [Coyal A., Norton DP, Budai JD, Phavantham N., et al. High Critical Current Density Superconductors Tapes by Epitaxial Deposition of Ba ₂ Cu ₃ O _x Thick Films on Biaxially Textured Metals // Appl. Phys. Lett. 1996. V.69, No. 16. P.1795-1797].

The main characteristic of such tape multilayer high-temperature superconductors is the critical current value, which largely depends on the sharpness of the crystallographic texture in the superconductor material, inherited from the cubic texture of the metal substrate. Another factor affecting the critical current value is the magnetic state of the substrate material. The lower the magnetic permeability of the substrate, the greater the critical current. In addition, for the production of long tapes in industry, it is necessary to have sufficiently high strength properties of the supporting metal tape.

The biaxial (cubic) texture is formed during the recrystallization of some face-centered cubic metals subjected to a high degree of cold rolling.

The cubic texture after recrystallization annealing is obtained only in those metals and alloys with a face-centered cubic lattice (FCC) that have sufficiently high values of the stacking fault energy (EDU). The magnitude of the EMF determines the type of multicomponent deformation texture. The deformation textures of fcc metals are divided into 3 types [Vishnyakov Y.D., Babareko A.A., Vladimirov S.A., Egiz I.V. Theory of texture formation in metals and alloys. M .: Science. 1979. 343 p.]. It is believed that in materials with low EDU, such as α-brass, only the component {110} <112> (B) is developed. In materials with high EDI, such as Al, the components S {123} <634> and C {112} <111> prevail in the deformation texture. In materials with average EDF values, for example, in copper, all components — C, S, and B — are present. In materials with a strain type texture of copper (this refers to materials with medium and high EDF), a cubic texture {100} <001 is formed after primary recrystallization >, and in materials with a deformation texture such as brass, i.e. With low EDU, a cubic texture does not form.

The substrate can be textured using deformation processes, such as deformation using rolling and recrystallization annealing of the substrate. An example of such a process is the process of biaxial texturing of a substrate using rolling (RABiTS process, from the English. "Rolling-assisted biaxially textured substrate"). In this case, large amounts of metal can be economically processed by deformation processing and annealing and can obtain a high degree of texturing [RF patent 2408956].

Known methods for the manufacture of biaxially textured substrates, which use various metals and alloys.

So, it is proposed to obtain biaxially textured substrates of pure metals: Ni, Cu, Pd, Pt, Ag and alloys of any of the above metals [US patent No. 6180570].

However, not all of these metals and alloys provide, after processing, the cubic texture needed to create HTSC conductors. For example, it is known that in silver when rolling at room temperature it is impossible to obtain a cubic texture [Wasserman G., Greene I. Textures of metallic materials. M .: Metallurgy, 1969. 655 p.].

A known method of manufacturing a biaxially textured substrate of a nickel-based alloy, including smelting, forging, cold rolling and recrystallization annealing, in which an alloy with the following alloying elements was used as a nickel-based alloy: ≤15 at.% Of elements of the VB group or ≤20 at .% elements of the VIB group, or ≤10 at.% Sn, or ≤10 at.% Al, or ≤50 at.% Cu, or ≤25 at.% Zn, or ≤12 at.% Ti [US patent No. 5964966 ].

As follows from the description of the patent, the chemical composition of this alloy creates scattering of cubic peaks at half height ≤30 ° and, therefore, does not allow to obtain a sharp cubic texture, characterized by a percentage of cubic grains of at least 90%. This is also confirmed by the pole figure shown in the patent for an alloy of nickel with 20% chromium.

Closest to the claimed technical essence is a method of manufacturing a biaxially textured substrate of a binary alloy based on nickel for epitaxial deposition of buffer and high-temperature superconducting layers for tape superconductors on it, including smelting, forging, cold rolling to a degree of deformation of ≥97% and recrystallization annealing at temperature ≥1000 ° С. This alloy may contain nickel and tungsten (for example, from about one atomic percent of tungsten to about 20 atomic percent of tungsten, from about two atomic percent of tungsten to about 10 atomic percent of tungsten, from about three atomic percent of tungsten to about seven atomic percent of tungsten, about five atomic percent of tungsten). In addition, the binary alloy may contain relatively small amounts of impurities (for example, less than about 0.1 atomic percent impurities, less than about 0.01 atomic percent impurities, or less than about 0.005 atomic percent impurities). In some of these embodiments, the substrate contains more than two metals. The preferred substrate material is Ni with 5 wt.% W [RF patent No. 2408956].

A substrate made of Ni-5 at.% W alloy in this way provides a high degree of texturization, but no sharp cubic texture is formed in alloys with a high tungsten content (10 at.% And especially 20 at.%).

However, in addition to the high degree of texturing and strength of the binary nickel alloy tape, one of the important properties necessary for using a metal substrate in creating a multilayer tape with a superconductor is chemical resistance. The chemical resistance of an alloy with tungsten, although it is better in comparison with alloys with a number of other alloying elements, for example iron or chromium, is still not high enough.

In some embodiments, [RF patent No. 2408956] use the addition of a third element to a binary nickel alloy. The introduction of the third element is usually carried out to increase the chemical resistance of the nickel alloy substrate [Tuissi A., Villa E., Zamboni M., Evetts J.E., Tomov R.I. Biaxially Textured NiCrX (X = W and V) Tapes as Substrates for HTS Coated Conductor Applications // Physica C: Superconductivity and its Applications. 2002. V.372-376. Part 2. P.759-762].

However, the addition of the third element to the nickel alloy can lead to a decrease in thermal stability by the beginning of secondary recrystallization, for example, secondary recrystallization develops in the nickel alloy with 7.2 at.% Chromium and 3.6 at.% Tungsten during recrystallization annealing at a temperature of 1150 ° С. destroying the cubic texture [Rodionov D.P., Gervasyeva I.V., Khlebnikova Yu.V., Kazantsev V.A., Sazonova V.A. Creation of epitaxial substrates from Ni-Cr-W alloys with a sharp cubic texture and a Curie point below 77 K for superconducting compositions. FMM. 2009.V. 107. No. 2. S.198-206].

The basis of the invention is the task of increasing the chemical resistance of the biaxially textured substrate of a binary alloy based on Nickel while maintaining the degree of texturing and strength.

The problem is solved in that in the method of manufacturing a biaxially textured substrate of nickel-based binary alloy for epitaxial deposition of buffer and high-temperature superconducting layers on it for tape superconductors, including smelting, forging, cold rolling of the tape to a degree of deformation of ≥97% and recrystallization annealing of it at a temperature of ≥1000 ° C, according to the invention, an alloy of the following chemical composition, at.%: is used as a nickel-based binary alloy:

Rhenium - ≤1,

Nickel is the rest.

In nickel alloys with a rhenium content of more than 7 at.% After rolling and recrystallization, the necessary cubic texture does not form.

In pure nickel, after high degrees of cold rolling, a texture is formed that is suitable for forming an acute cubic texture in the tape after primary recrystallization, but low strength properties are not suitable for the production of long ribbons. Doping significantly increases the strength properties of pure nickel (figure 1), but, increasing the lattice parameter of the alloy (figure 2), reduces the energy of packing defects of pure metal, which, in turn, leads to a change in the type of texture of deformation.

Replacing tungsten with rhenium in a double nickel alloy leads to several advantages. In terms of resistance to the action of most chemicals, rhenium approaches platinum metals [http://specmetal.ru/svoistva-reniya]. It is known for its use (up to 10 wt.%) In high-temperature nickel alloys used for gas turbine blades of aircraft engines [E.N. Kablov. Physico-mechanical and technological features of the creation of heat-resistant alloys containing rhenium. Vestn. Mosk. University. Ser. 2. Chemistry. 2005.V. 46. Number 3. S.155-167]. An increase in the rhenium content in these alloys leads to an increase in both the characteristics of heat resistance and the durability of the products.

The melting temperature of rhenium (3180 ° C) is lower than the melting temperature of tungsten (3420 ° C). This gives energy savings in alloy smelting.

We have studied the process of changing the component composition of the deformation texture and the formation of a cubic orientation after primary recrystallization in a number of nickel-based binary alloys.

With increasing concentration of d - transition elements (Cr, Mn, V, Mo, W, Re, Nb) in substitutional solid solutions with nickel in the deformation texture, the volume fraction of components C and S decreased and the amount of component B increased (Fig. 3). When the concentration of the alloying element is more than a certain value, the smaller the larger its atomic radius, after the primary recrystallization, a cubic texture did not form. It was experimentally established that in this case, the sum of the volume fractions of components C and S became less than twice the number of components B (ΔV / V (S) + ΔV / V (C) = 2ΔV / V (B)), and the lattice parameter increased to values greater than 3.55 Å (FIG. 3).

For nickel alloys with rhenium (up to 7 at.%), The sum of the main deformation components C and S is more than twice the amount of component B (Table 1) and, after recrystallization annealing at a temperature of ≥1000 ° С, an acute cubic texture is formed in them (Fig. 4) .

Figure 1 shows the hardening of Nickel when alloyed with various metals.

Figure 2 shows the change in the lattice parameter of nickel-based alloys during alloying.

Figure 3 shows the change in the amount of the main components of the deformation texture when alloying nickel with chromium, molybdenum, tungsten and niobium.

Figure 4 shows the pole figure {111} after recrystallization of the tape Ni-4.1 at.% Re at 1100 ° C for 1 hour

Table 1 shows the volume fraction of the main texture components after cold rolling.

Table 2 shows the chemical composition, technological characteristics, mechanical and magnetic properties of the investigated alloys.

Figure 1 shows that the rate of hardening during alloying of pure nickel rhenium lies between such strong reinforcing elements as tungsten and molybdenum.

The method is as follows.

Alloys are melted in alundum crucibles in an argon atmosphere in a vacuum induction furnace. Nickel with a purity of 99.93% and rhenium with a purity of 99.94% are used. The ingots are forged at a temperature in the range of 1000-800 ° C into bars with a cross section of 10 × 10 mm, then forged at 650 ° C to a size of 7 × 7 mm. After grinding, 6 × 6 × 150 billets are obtained, which are annealed at 800 ° С for 1.5 hours. The average grain size in the workpieces should not exceed 40-50 microns. Cold rolling of billets is carried out on polished rolls to a tape with a thickness of 80-100 microns, the degree of cold deformation is 98-99%. Recrystallization annealing to obtain a biaxial texture is carried out for 1 hour in a vacuum oven (3 · 10 ^-5 mm Hg) at temperatures of 1000, 1050 and 1150 ° C.

Example 1

Alloy Ni - 4.1 at.% Re: an ingot weighing 500 g was melted in an argon atmosphere in a vacuum induction furnace, forged at 1000-800 ° С on a bar 10 × 10 mm, then at 600 ° С - on a bar 7.5 × 7, 5 mm. The billet obtained after forging was annealed at a temperature of 800 ° С for 1.5 h. The annealed rod was ground to a section of 6 × 6 mm. The initial grain size before cold rolling was 78 μm. The bar was rolled cold with a degree of deformation of 98%. The sum of the volume fractions of the components of the strain texture was: S + C = 34.0%, 2B = 18.4% (Table 1).

As can be seen from Table 1, the sum of the volume fractions of the components S and C is much higher than the doubled volume fraction of component B, which indicates the possibility of the formation of a sharp cubic texture after annealing to undergo primary recrystallization. The advantage of favorable deformation components over unfavorable in an alloy with 4.1 at.% Rhenium is greater than in an alloy with 4.8 at.% Tungsten. As a result, the scattering of the cubic texture after annealing in the alloy with rhenium is somewhat less than in the alloy with tungsten (Table 2, half-width of the {200} line, 5.7 and 6.3 °, respectively).

The cold-rolled tape was annealed in vacuum at a temperature of 1100 ° C for 1 h. The finished tape consisted mainly of cubic grains, the pole figure {111} is shown in figure 4.

The yield strength of a finished tape with 4.1 at.% Re is 146 MPa (see Table 2), slightly less than the value for an alloy with 4.8 at.% W, but is 5.8 times higher than the yield strength of a pure nickel tape.

The structural advantages of the alloy with 4.1 at.% Re compared to 4.8 at.% W are higher thermal stability to the onset of secondary recrystallization, since the appearance of secondary crystallized grains with a grain different from the cubic orientation spoils the substrate texture.

The Curie temperature in the alloy with 4.1 at.% Rhenium is 416 K, which is significantly lower than in pure nickel (628 K), but slightly higher than in the alloy with 4.8 at.% Tungsten (333 K).

However, it should be noted that the tungsten concentration of 4.8 at.% Is almost limiting in terms of the possibility of the formation of a cubic texture, while the amount of rhenium can be increased to 7 at.% Without the risk of deterioration of the cubic texture. In this case, the strength properties should significantly increase and the Curie temperature should decrease.

Claims (1)

A method of manufacturing a biaxially textured nickel-based binary alloy substrate for epitaxial deposition of a buffer and a high-temperature superconducting layer on it for tape superconductors, including smelting, forging, cold rolling to a degree of deformation of ≥97% and recrystallization annealing at a temperature of ≥1000 ° C, characterized in that as a binary alloy based on Nickel using an alloy of the following chemical composition, at.%:
Rhenium ≤7 Nickel rest

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