DE2320107B2 - Superconducting alloy - Google Patents

Description

that with a smaller amount than 2 atomic percent nuclei sufficient increasing effect on the critical Current density is obtainable, which results from the refinement of the crystallites, while it results from increasing the amount of yttrium above 15 atomic percent worsens the deformability of the material. A deformability of the material is possible despite an increase in the amount of yttrium if the melt cools down rapidly will. Therefore, the amount of yttrium was set in the range of 2 to 15 atomic percent, in which to the critical current density is high, as shown in FIG. 2 and 3 show.

Additional studies showed that the addition of zirconium to the invention Niobium-titanium-yttrium alloy has the effect of further increasing the critical current density. The one to be added The amount of zirconium must be in the range from 1 to 15 atomic percent, since it is a lower addition than 1 atomic percent is practically ineffective, while the addition of a larger amount of zirconium than ao 15 atomic percent leads to a deterioration in the deformability of the material. It is appropriate these results as evidence of the effect of adding yttrium to the known niobium-titanium-zirconium-based alloy and not to be understood as a new discovery of the effects of zirconium. To the effect of the yttrium on ternary alloys consisting essentially of niobium and titanium with the addition of a To determine a third element other than zirconium, a series of tests was carried out in which one Yttrium added to these alloys, and it was found that the addition of yttrium to these alloys with hafnium, vanadium, tantalum, aluminum or molybdenum as the third element, it has a grain-refining effect brings, but has no effect to increase the critical current density.

It has been found that the superconducting alloys of the present invention have a stable high critical current density and excellent deformability are preferred those selected from 20 to If it is a niobium-titanium-yttrium alloy, there is 50 atomic percent niobium, 2 to 6 atomic percent yttrium, the remainder titanium is, and that they additionally contain 2 to 6 atomic percent zirconium, if it is the niobium-titanium-zirconium-yttrium alloy goes.

The invention is to be explained in more detail by means of examples.

In the examples, the samples were sampled by melting niobium, titanium and yttrium or niobium, titanium, yttrium and zirconium in certain amounts with a total weight of 100 g in an argon atmosphere in an electric arc furnace using a non-consumable electrode to form a button , further by cutting a ^{square piece measuring about 6 mm 2} from the button sample, by solution annealing this piece at 1000 ° C for one hour, coating the piece with copper, cold forming the coated piece at room temperature until the superconducting core alloy becomes a wire with 0, 16 mm diameter was deformed, and subsequent aging heat treatment of the wire of 100 hours at 35O ⁰ C. The critical current density of each sample was ^{measured in liquid helium at 4.2 °} K by placing the sample in an external magnetic field in such a position that the direction of current conduction was at right angles to the magnetic field. In the following examples, all percentages of the alloy compositions are atomic percentages.

example 1

The critical current densities of an alloy with 35% niobium and 65% titanium and an alloy with 35% niobium, 62.5% titanium and 2.5% yttrium in outer Magnetic fields of 10 kOe or 70 kOe are given in the following table 1: It was found that the yttrium-containing alloy has an extremely high critical current density, especially in the area has strong magnetic fields.

Table 1

sample

35% Nb; 65% Ti ..
35% Nb; 62.5% Ti;
2.5% Y

Critical current density (A / cm «)

lOkOe 7OkOe

3.5 · 10 ⁸ 4.0 · 10 ⁵

4.0 · 10 * 6.2 · 10 «

It was further found that titanium alloys with a fixed amount of 25% niobium in partial Replacement of the titanium by a changing amount of up to 10% yttrium extremely high critical current densities in the range of weak magnetic fields, as Table 2 shows: A titanium alloy with 15 atomic percent yttrium was unsuitable for deformation.

Table 2

sample

25% Nb; 75% Ti

25% Nb; 72.5% Ti;

2.5% Y

25% Nb; 70% TiV5% Y "
25% Nb; 65% Ti; 10% Y
25% Nb; 60% Ti; 15% Y

Critical current density (A / cm ¹ )

lOkOe I 7OkOe

4.4 · 10 ⁶

6.7 x 10 ⁵ 7.4 x 10 ^B 7.2 x 10 ^B

4.9 · 10 *

5.8 x 5.5 x 5.0

10 * 10 * 10 *

not deformable

Example 2

The critical current densities of an alloy with 35% niobium, 62.5% titanium and 2.5% zirconium and an alloy with 25% niobium, 60% titanium, 2.5% zirconium and 2.5% yttrium were exposed to external magnetic fields of 10KOe and 7OkOe measured, and the results are given in Table 3: The Alloy with yttrium content showed an extremely high critical current density, especially in the high range magnetic fields.

Table 3

sample

35% Nb; 62.5% Ti;

2.5% Zr

35% Nb; 60% Ti;

2.5% Zr; 2.5% Y

Critical current density (A / cm ^a )

10 kOe 70 kOe

4.5 x 10 ^s 5.1 x 10 ⁶

7.1 · 10 ¹

8.2 · 10 ⁴

Titanium alloys with a fixed amount of 25 / niobium and a fixed amount of 2.5% zirconium, be

which the titanium was partially replaced by various amounts of less than 10% yttrium extremely high critical current densities, especially in the area of weak magnetic fields, such as Table 4 shows:

Table 4

sample

25 ° / Nb * 72 S ⁰ / Ti

2.5 ° / Zr
25% Nb; 70% Ti; "'

2.5% Zr; 2.5% Y
25% Nb; 67.5% Ti;

2.5% Zr; 5% Y ..
25% Nb; 62.5% Ti;

2.5% Zr; 10% Y.
25% Nb; 57.5% Ti;

2.5% Zr; 15% Y.

Critical current density
(A / cm)

lOkOe 7OkOe

8.5 x 10 ^s

9.3 · 10 ⁶

10.0 x 10 ^B

9.5 x 10 ^B

3.6 · 10 ⁴
5.2 · 10 *
4.8 · 10 ⁴
4.0 · 10 «

not deformable

The 15% yttrium alloy was not deformable. However, the ductility of this alloy can be regained, and the cold drawing of this alloy into a wire with 0.15 mm diameter becomes possible if the average grain size of the yttrium-rich second phase is reduced to below 5 μτα by utilizing the separation into two liquid phases. The deformability of the alloys was rated based on their hardness. The results were as follows:

Well-known alloys

35% Nb; 65% Ti HV 168 kp / mm ^a

35% Nb; 62.5% Ti; 2.5% Zr .. HV 180 kp / mm * Alloy according to the invention
35% Nb; 61% Ti; 4% Y HV130kp / mm ²

A sample of each is provided for hardness test alloy was produced in the following manner: The alloy material was homogeneously in an argon atmosphere by means of an unconsumable-arc at a temperature over 2700 ⁰ C melted and after the Haiten the melt with stirring in a two phase separation temperature range above 2400 ⁰ C in a water-cooled Mold 5 mm in diameter and 40 mm in length cast to form an ingot of the alloy. The alloy block was then subjected to a solution heat treatment at 1000 ^{° C. for 1 hour.}

From the overall overview of Tables 1 to 4 it can be seen that in order to increase the critical current density in the weak magnetic field range, it is necessary to reduce the proportion of niobium below about 30 atomic percent and to add about 2.5 atomic percent of yttrium, while it is necessary to increase the critical current density in the Strong magnetic field is required to increase the amount of niobium to about 30 atomic percent and add about 5 atomic percent yttrium. The experimental data relating to the aging treatment are shown in FIG. 1 shown. The Nb-Ti-based and Nb-Ti-Zr-based alloys have, when they are subjected to a heat treatment at 350 ^° C., «-phase precipitates formed in the / 3-phase matrix, which have the critical current density of the Increase alloys. The times required for aging treatment are:

Nb-Ti alloy several thousand

ίο hours,

Nb-Ti-Zr alloy 200 to 400 hours,

Alloy according to the invention 0 to 100 hours.

The so-called "two-phase separation" in this application means the melt at one temperature (2400 to 2700 ° C) at which the two-phase separation occurs, and then rapidly cool the melt. The multiphase structure obtained in this way has a high critical current density. As the F i g. 4 a

ao to 4c are obtained in the case of the Nb-Ti composition (Fig. 4 a) a / 3-phase Nb-Ti alloy, and a »-Ti phase is precipitated by aging treatment. In the case of the Nb-Ti-Y composition the melt separates into two liquid ones

as phases, d. H. a Y-rich Z ^ phase and an im Ljj phase consisting essentially of Nb-Ti (Fig. 4b), and one obtains a eutectic of the / S phase Nb-Ti and the Y-rich phase from "Ti +" Y (FIG. 4c) by cooling the two liquid phases

separated melt. Expressed as a formula:

(Nb - Ti - Y) -> β (Nb - Ti) + «(Ti - Y)

A further aging treatment of the / S-phase Nb-Ti leads to the precipitation of a «-Ti-phase, the the superconductivity of the alloy is further improved.

The cooling rate is common

5 to 7 ° C / second on average in the case of the water-cooled form, and a higher cooling rate leads to the formation of smaller crystallites and an increase in the critical ones Current density (Figures 5 and 6).

The alloys according to the invention have compared to the known alloys of Nb-Ti and Nb-Ti-Zr has the following advantages:

(1) The critical current density is high.

(2) The aging time is relatively short and enables a substantial reduction in the total processing time in the preparation of.

(3) A high critical current density can be obtained simply by creating a block by means of two-phase separation obtain.

(4) The critical current density can be determined by combining the known heat treatment and Increase deformation.

(5) The alloys are excellent in plastic deformability

It is thus possible according to the invention to noticeably reduce the critical current density of the niobium-titanium base alloys to improve.

For this purpose 4 sheets of drawings

Claims (6)

At present one sets ζ. B. niobium-titanium alloy patent claims: conditions for magnets that are supposed to generate strong magnetic fields, since these alloys have a maximum critical 1. Superconducting alloy, thereby enabling a field of 120 kOe, but this is marked with that they wrestled from 20 to 50 atoms 5 have the disadvantage that their critical current percent Niobium, 2 to 15 atomic percent yttrium, the remainder densities are relatively low. To increase the Kriti-Titan and manufacturing-related impurities see current density, it is known to be the material of a there is aging heat treatment over a longer period of time 2. Superconducting alloy according to claim 1, subject to permanent or oxygen in the material characterized in that they additionally introduce 1 to io, and these procedures were 15 atomic percent zirconium already contains practically applied however these are 3. Superconducting alloy according to claim 1 or methods not necessarily desirable because they 2, characterized in that they cause a reduction in production output from one Multiphase structure with a yttrium-rich phase and impair the deformability of the material, and a niobium-titanium matrix 15 In addition, there are superconducting niobium-titanium-zirconium 4. Superconducting alloy according to claim 1 or alloys known. 3, characterized in that it consists of 20 to The invention is based on the object of improving the 50 atomic percent niobium, 2 to 6 atomic percent yttri-critical current density properties of niobium-titanium, the remainder titanium and manufacturing-related Ver-based alloys,
impurities. ao According to the invention, this object is achieved by 5. Superconducting alloy according to claim 2 or solves that the superconducting alloy of 20 to 3, characterized in that it consists of 20 to 50 atomic percent niobium, 2 to 15 atomic percent yttrium, 50 atomic percent niobium, 2 to 6 atomic percent zir - remainder titanium. Besides it contains only unconium, 2 to 6 atomic percent yttrium, the remainder titanium mechanical impurities. and production-related impurities were the subject of the invention, with which this stands up, there would also be one such superconducting one 6. Superconducting alloy according to claim 3, the alloy additionally containing 1 to 15 atomic percent zirconia characterized that the yttrium-rich contains konhim. Phase has a fine-grain structure in which a The invention is explained in more detail with reference to the drawings Average grain size of less than 1 μm 3ο explained; it shows: is present. F i g. 1 is a diagram for explaining the relation hung between the aging period and the critical one Current density of an alloy according to the invention and two well-known alloys, 35 Fig. 2 is a diagram for explaining the relationship between the amount of yttrium and the critical one The invention relates to superconducting alloy current density of the alloy according to the invention,
wrestling on a niobium-titanium basis. F i g. 3 a diagram to explain the relationship Superconductivity is the phenomenon in which the elec- tion between the amount of yttrium and the critical resistance of a certain material becomes zero 40 current density of the alloy according to the invention when it is at extremely low temperatures.
is cooled. F i g. 4a, 4b, 4c equilibrium diagrams of the Substances with this property, i. superconducting systems Nb-Ti, Nb-Y and Ti-Y,
Substances are characterized by three factors, namely- F i g. 5 a diagram to explain the relationship Lich by the critical temperature Tc, the critical hung between the cooling rate and field Hc and the critical current Ic. Now the average grain size of the second phase of these three factors of a superconducting material will be invented. <i ben alloy and
considered, which for coils of superconducting magnets F <c. 'Diagram to explain the relationship etc. is used. hung zv t ··. the average grain size of the two The coil should at temperatures below the critical 50 th phase and the critical current density of the inven-tion temperature of the material from which it consists, the alloy according to the specification. work, and one generally applies liquid helium- According to the invention, a remarkable one can be found temperature (4.2 ⁰ K) as the operating temperature. Therefore, improvement of the critical current density despite the fact that the critical temperature of the material should be achieved by far, that the critical field should be higher than 4.2 ° K as possible. The maximum value of 55 binary niobium-titanium alloys is equivalent. Wei current that can flow in the coil is limited by the ter, the deformability of the material is limited by the critical current value, and the maximum yttrium content according to the invention does not affect the magnetic field that the coil can generate. According to the invention, the amount of became a critical field. It is therefore desirable that the material used for the individual components is determined in the following way: The material used is as high a critical amount as possible, taking into account the actual temperature : Electricity and a critical field that is as strong as possible is 20 atomic percent, a rapid drop in the critical field. Temperature and the critical field occurs, true At constant temperature, the critical one depends on an increase in the niobium content above 50 atomic percent Current of a superconducting material from the magnet 65 for the aging heat treatment takes a longer time table field, and the critical current density is raised as usual required before the desired one normally when determining the conductivity a critical current density is reached. The yttrium ming of the superconducting material used. was determined taking into account the fact