JPS63274734A - Low activation aluminum alloy having high electrical resistance - Google Patents

Abstract

PURPOSE:To provide the titled Al alloy by adding specific ratios of Si, Li, Mg, Cu, etc., to an Al matrix. CONSTITUTION:The compsn. of the alloy is regulated, by weight, one or two kinds among 1.0-8.0% Li, 0.5-50% Si, 0.1-5.0% Mg, 0.01-6.0% Cu and the balance consisting substantially of Al. One or more kinds among 0.05-0.20% Ti, 0.05-0.35% V, 0.05-0.3% W, 0.05-0.3% Zr and 0.001-0.02% Be are additionally incorporated into the alloy at need. In this compsn., the elements such as Si, Li, Mg, etc., are low activation elements, and at the same time, they improve the material characteristics such as electrical resistance, mechanical properties, etc. Said Al alloy is suitable as the material for structure under the environment of radioactive pollution to which a large magnetic field is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Technical Field The present invention relates to an aluminum alloy that has high electrical resistance and low activation properties.

(b) Background of the technology Aluminum alloy is a metal material in the second largest demand after steel, and because it is lightweight and has excellent thermal conductivity, corrosion resistance, electrical conductivity, and workability, it is used in aircraft, automobiles, electric wires, etc. It is used in a wide variety of fields, from daily necessities to beer cans. Recently, it has also been attracting attention as an ultra-high vacuum vessel because it allows better control of impurities during the manufacturing process than steel materials.

Furthermore, from the viewpoint of low activation material, it is also used as a material for accelerators in the field of high energy physics.

Although mechanical properties such as strength and hardness are considered to be considerably inferior to steel materials, some types of aluminum alloys have high strength comparable to steel materials, and are BACKGROUND OF THE INVENTION Through recent new alloy manufacturing methods such as strengthening methods and powder metallurgy methods, alloys have been developed that have significantly improved conventional alloy properties, such as high strength and high heat resistance alloys. These aluminum alloys are considered to be materials that can sufficiently perform normal functions.

Recently, due to the excellent low activation property of aluminum alloys, the use of aluminum alloys in radioactively contaminated environments such as fusion reactor materials is being considered.

In particular, magnetic field confinement type tokamak type plasma equipment is promising as a plasma device involving nuclear fusion, but because of its complicated structure, it is thought that maintenance work will be nearly impossible if the reactor is completely shielded. Therefore, in a plasma device involving a nuclear fusion reaction, materials with low activation or low residual radioactivity are required.

Low activation elements include Li, Be, C, Mg, and A.
R, Si.

v, t'b, etc. exist, but when considered as a structural material,
Considering the amount used, it seems that aluminum alloy, which has the most established industrial basis, is suitable.

However, when aluminum alloys are used as materials for devices such as tokamaks that are subject to large electromagnetic fields, the electrical resistance of the alloys becomes a very serious problem.

Metallic materials in strong magnetic fields generate induced currents that increase in proportion to the conductivity of the material. This induced current is subjected to a force according to Fleming's left-hand rule in an external magnetic field, so a large force acts on the material.

Therefore, to reduce this force, it is necessary to increase the electrical resistance of the material and reduce the induced current.

For these reasons, a material with an electrical resistance value of 20% below the IACS value and a tensile strength of 30 kg/1II112 or more is required.

(C) Disclosure of the Invention The present invention provides an aluminum alloy for use in a radioactively contaminated environment where a large magnetic field acts.
It is a low activation element in the aluminum base, and at the same time has electrical resistance,
This aluminum alloy has been developed to have high electrical resistance and low activation by adding elements such as Si, Li, and Mg that improve material properties such as mechanical properties.

In the present invention, among the alloying elements added, the low activation elements and Si, Si, Li, Mg, V, and W Kaalt! In addition, these elements have the effect of reducing electrical resistance, making the structure finer, and improving mechanical properties.

In addition to low activation, the Si element has properties such as lowering the thermal expansion of the alloy and improving heat resistance. The amount added is from 0.5 to 50% depending on the properties required for the alloy. 0.5%
If it is less than 50%, the sufficient effect cannot be exhibited, and if it is more than 50%, it becomes difficult to manufacture the alloy, and in particular, the workability becomes extremely poor. Moreover, the strength also decreases.

Li is an excellent element with low activation property, but at the same time it has high strength and
It is an essential element to increase electrical resistance. In order to fully exhibit its effect, it is necessary to add 0.5% or more. If it is less than this, the requirements for strength and electrical resistance cannot be fully satisfied. Further, addition of more than 8% causes problems in alloy production, such as oxidation of the alloy and a significant decrease in plastic workability due to a decrease in toughness.

Furthermore, since the powder and chips of the Aj2-Li alloy containing 8% or more of Li are very active, the risk of ignition powder explosion etc. is extremely high. Therefore, the upper limit of the amount of Li added is set to 8%. The content is preferably 6% or less, which significantly improves alloy properties and material yield.

In addition, Co and copper are effective elements for increasing the strength and electrical resistance of the alloy, and the amount of Cu added is 0.01 to 6.0%.
, Mg is 0.1 to 5.0%. It goes without saying that if the amount added is less than this, the effect of improving properties will be small, and if it is more than this, the mechanical properties will deteriorate, which will cause problems in material production. These elements exhibit greater effects when added at the same time in appropriate proportions.

Furthermore, each of the additive elements Ti, V, Zr, and W contributes to improving electrical resistance and making crystal grains finer, thereby making the properties required of the material more favorable. Since these additive elements have a small amount of solid solution with respect to U,
If it is too large, it will create intermetallic compounds and reduce plasticity, so it is necessary to add an appropriate amount.

Zr is known as an element that improves the heat resistance of alloys, and is effective in improving material properties.

Furthermore, Be, which is a low activation element, is added to prevent Mg from oxidizing, and the amount of Be added is 0.001 to 0.
．． 0.02% is appropriate.

The β-alloy with the above composition is made into an ingot by melting, adjusting the molten metal, and casting using the usual aluminum alloy manufacturing method, then subjected to homogenization heat treatment, and made into a raw material by hot and cold plastic working. The material is made to have the desired properties through solution treatment and aging treatment.

However, in the production of aluminum alloys containing more than 10% Si or more than 3% Li, coarse Si primary precipitates or Li-based compounds tend to precipitate during solidification of the molten metal, and these significantly reduces toughness.

Therefore, when producing an alloy containing such a large amount of Si or Li, it is necessary to make these coarse precipitates fine. An effective method for this purpose is to rapidly solidify the molten alloy.

The solidification rate must be 102°C/sec or higher, and at this time, the precipitates formed in the alloy are fined,
Even the coarsest Si primary crystal precipitates are 40 μm or less. Further, in order to rapidly cool the molten alloy, it is effective to pulverize it, and a method of manufacturing the alloy by the powder alloy method is also used.

The powder produced by the atomization method has a solidification rate of <42 mesh (350 μm) or less, and has a solidification rate of 102'
It has a cooling rate higher than C/sea.

The powders usually used are ones with a mesh size of 42 or less by gas atomization, or those whose precipitates are adjusted to 40 μm or less by mechanical alloying or ball milling, and these powders are packed directly into cans or molded by mechanical pressure. The material is heated to 250 to 550°C and then extruded into a raw material.

Preferably the powder or powder compact is heated to 10-'mm Hg
.

Vacuum degassing is performed under conditions of approximately 200°C to 500°C.

This allows moisture, gas, etc. adsorbed on the powder to be sufficiently removed. The obtained material is a material that has been given desired characteristics through various solution treatments and aging treatments.

Aluminum alloys manufactured using the methods described above have high electrical resistance and are low activation materials, and can be effectively used as materials in radioactively contaminated environments with large magnetic fields such as in nuclear fusion reactors. can be done.

EXAMPLE The aluminum alloys shown in Table 1 were manufactured by various methods. I/M is a manufacturing method using normal melting and casting, and is melted in an inert gas of Ar or TL.
After adjusting the composition to the composition shown in Table 1, an ingot was prepared, which was hot-rolled and cold-rolled, followed by solution treatment at about 500°C and aging at 150-200°C. P/M is a powder of 42 mesh or less that has been atomized in an inert atmosphere, packed in a can, degassed, heated to 400-450℃, hot extruded, and then subjected to solution treatment and aging treatment. Something.

In M/A, fine Si powder is added to Aβ-Li-Cu-Mg powder in an inert atmosphere, the mechanically alloyed powder is packed in a can, degassed, and then extruded using the same procedure as P/M. It is made of wood and subjected to heat treatment.

The electrical resistance and tensile strength of the material obtained by the above method are shown below. In addition, as an evaluation of the radioactivity of these alloys, D-
The residual radioactivity level was determined one month after the T reaction. As a guideline, when it is less than 10-2 mrem/hr (a level that has almost no effect on humans), it is marked with an ○, and when it is less than this, it is marked with an X.

As shown in Table 1, all the aluminum alloys according to the present invention have good radioactivity and a tensile strength of 35
kg/mn” or more, and the electrical conductivity is lAc5.
With a value of 19 or less in terms of %, it has good properties as a structural material in a radioactively contaminated environment where a large magnetic field is applied.

Claims (4)

[Claims] (1) 1.0 to 8.0% L as an alloying element by weight
i and 0.5 to 50% Si, and 0.1 to 5%.
An electrically resistive material characterized by high electrical resistance, containing one or two of 0% Mg and 0.01 to 6.0% Cu, and the remainder being substantially Al. Highly low activation aluminum alloy. (2) 1.0 to 8.0% L as an alloying element by weight
i and 0.5 to 50% Si, and 0.1 to 5%.
Contains one or two of 0% Mg and 0.01 to 6.0% Cu, and further contains 0.05 to 0.20% Ti, 0
．． 05-0.35% V, 0.05-0.3% W, 0
．． 05-0.3% Zr, 0.001-0.02% B
An aluminum alloy with high electrical resistance and low activation, characterized in that it contains one or more selected from the group e., and the remainder consists essentially of Al. (3) A low-activation aluminum alloy with high electrical resistance, characterized in that it is solidified at a cooling rate of 10^2°C/sec or more according to claim (1) or (2). (4) In claim (1) or (2), a quenched powder with a solidification rate of 10^2°C/sec or more, an atomized powder with a particle size of 40 mesh, or a precipitate with a particle size of 40 μm or less An aluminum alloy with high electrical resistance and low activation, which is obtained by hot plastic processing using powder prepared as raw material.