JPH05263177A - Manufacture of nb3al intermetallic compound base alloy having a15 type crystalline structure - Google Patents

Abstract

PURPOSE:To manufacture an Nb3Al intermetallic compound base alloy having an A15 type crystalline structure by uniformly mixing Nb metallic simple powder and Nb-Al alloy powder in a specified ratio, subjecting it to cold compacting and executing sintering by heat treatment. CONSTITUTION:Al metallic simple powder (having 20 to 50mum average grain diameter) and Nb-Al alloy powder (having 0.5 to 30mum average grain diameter) are uniformly subjected to mechanical mixing in such a manner that the content of Nb is regulated to 83 to 96wt.% and that of Al to 4 to 17wt.%. This mixed powder is compacted in a temp. range in which the Nb metallic simple body powder and Nb-Al alloy powder do not come into reaction with each other in such a manner that its relative density is regulated to about >=90%. This green compact is held to a temp. lower than the solid phase temp. in the alloy phase for 1 to 100hr in vacuum and is cooled. In this way, the objective uniform Nb3Al intermetallic compound base alloy with high density excellent in high temp. strength and mechanical properties and having an arbitrary shape can be obtd.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is based on Nb ₃ and Al as main components so that it is difficult to synthesize a compound having a uniform composition and a high density by a usual melt solidification method or powder sintering method.
N having an A15 type crystal structure with Al 2 as a main constituent phase
It relates to a method for producing a b ₃ Al intermetallic compound-based alloy.

[0002]

2. Description of the Related Art Generally, the higher the melting point of a metal-based material, the higher the high-temperature strength and the higher its operating temperature. Among metal-based materials, high melting point intermetallic compound-based alloys have attracted attention as next-generation ultra-high temperature heat resistant materials because of their high temperature strength, high heat resistance, and relatively low specific gravity due to their high melting point of nearly 2000 ° C. There is.

However, these compounds are extremely brittle at 800 ° C. or lower, which is the greatest obstacle to practical use. A1 of Nb-Al-based intermetallic compound-based alloy
The type 5 crystal structure has a possibility of imparting ductility, which is the greatest problem of intermetallic compound-based alloys, due to its high symmetry.

Conventionally, in the method for producing an intermetallic compound-based alloy, a metal element is blended so as to have a desired stoichiometric composition with reference to an alloy phase diagram, and this is melted by heating and then solidified by cooling. It has been produced by a melt solidification method or a powder sintering method in which different metal simple substance powders are mixed so as to have a predetermined composition, compression-molded and sintered.

Japanese Unexamined Patent Publication (Kokai) No. 62-86131 discloses a method for producing a powder sintered alloy by mixing two or more kinds of elemental metal elements having a large difference in melting point, compression molding and sintering.

[0006]

The problems of the prior art will be described in detail below by taking the Nb ₃ Al intermetallic compound base alloy as an example.

In the melting and solidification method of Nb ₃ Al intermetallic compound-based alloy, the melting point of Al is 660 ° C. and the melting point of Nb is 25.
Since 20 ° C. and about 1900 ° C. are different, when both are melted at the same time, Al having a low melting point reaches the boiling point and Al evaporates, so that an intermetallic compound-based alloy having a desired stoichiometric composition cannot be obtained. difficult. Even if a molten alloy having a desired stoichiometric composition is obtained, a compound other than the intended composition is precipitated and segregated during the solidification process, resulting in a uniform N content.
There has been a problem that a b ₃ Al intermetallic compound based alloy cannot be obtained.

On the other hand, in the conventional powder sintering method by mixing plain powders, Al having a low melting point is melted during the sintering process, and the Nb powder having a high melting point is washed away to form voids. ,
A uniform and high-density sintered body cannot be obtained. In addition, even if it does not flow out, Al is Nb due to the Kagendal effect.
There was a problem that the particles were diffused into the particles and voids were generated in the portions where Al was present.

Further, if the Al powder is made finer in order to reduce the pores, the surface area of Al becomes larger and
However, there is a problem that it will be oxidized.

Further, as disclosed in JP-A-2-163329, two or more kinds of powder elements are mechanically mixed so as to have a target composition, and the mixed powder is used by an apparatus such as HIP. There is also a method of heat compression molding. However, in an apparatus such as HIP that performs heating and compression at the same time, there is a limitation in the shape of a compact to be compression-molded, and it has been difficult to produce a high-density intermetallic compound-based alloy having an arbitrary complicated shape. ..

As described above, when alloying metal elements having a large difference in melting point, it is currently very difficult to obtain a homogeneous and high-density intermetallic compound-based alloy having a target composition, a target strength and a target shape. is there.

The object of the present invention is to provide uniform and high-density Nb ₃ A having excellent strength at high temperature and mechanical properties and having an arbitrary shape.
It is to provide a method for producing an intermetallic compound based alloy.

[0013]

SUMMARY OF THE INVENTION An object of the present invention is to consist of a metal element having a large difference in melting point between Nb metal simple substance powder and Nb-Al alloy powder by a compression molding and powder sintering process. The object is to obtain a homogeneous and high-density Nb ₃ Al intermetallic compound-based alloy having excellent characteristics and an arbitrary shape. The purpose is to use Nb metal powder alone and Nb-Al.
The alloy powder is mechanically mixed, and the mixed powder is cold compression-molded by utilizing the ductility of the Nb metal simple substance powder to prepare a molded body, and the molded body is subjected to heat treatment in a vacuum. This is achieved by diffusing the Nb and Al in the powder and the alloy powder.

The present invention uses the following means to obtain high temperature strength,
It is intended to produce a uniform and high-density Nb ₃ Al intermetallic compound-based alloy having excellent mechanical properties and an arbitrary shape.

(1) Nb metal simple substance powder and Nb-Al alloy powder are mechanically mixed so as to have a predetermined composition. Here, the advantage of using the Nb-Al alloy powder will be described. Nb
-Al alloy powder in which Nb and Al are alloyed, that is, Al forms a compound with Nb, so that Al is in a very chemically stable state and is oxidized during mechanical mixing. Therefore, the mixed phase having extremely high homogeneity and high purity can be formed.

(2) The mixed phase powder is compression-molded to a relative density of 90% or more in a temperature range in which the Nb metal simple substance powder and the Nb-Al alloy powder do not react with each other to produce a molded body. . Here, the advantage of using the Nb metal simple substance powder and the advantage of using the powder in which the average particle size of the Nb metal simple substance powder is larger than the average particle size of the Nb-Al alloy powder will be described. Since the Nb metal simple substance powder has relatively ductility even at room temperature, during cold compression molding, the Nb metal simple substance powder having a large particle size is deformed by stress and acts so as to fill the spaces between the mixed powders. Thus, it is possible to form a compact having a high density. As described above, in order to carry out pressure molding at a low temperature, it is possible to produce a molded product having a complicated shape with a relatively high degree of freedom as compared with the case of heating and compressing with a device such as HIP.

(3) By holding the compact in a vacuum at a temperature lower than the solid phase temperature in the alloy phase for 1 to 100 hours, the Nb and Al elements in the mixed phase are caused to undergo a diffusion reaction, and then cooled in a furnace. By doing so, it is possible to obtain a uniform and high-density sintered body of Nb ₃ Al intermetallic compound-based alloy, which has excellent high-temperature strength and mechanical properties and has an arbitrary shape.

[0018]

Next, the function of the intermetallic compound base alloy having Nb ₃ Al as the main constituent phase according to the present invention will be described. Nb ₃ A
Two types of powder materials that form an intermetallic compound-based alloy,
That is, the Nb simple substance metal powder and the Nb-Al alloy powder are mixed by mechanically stirring without heating. Here, since Nb-Al powder in which Al is alloyed with Nb is used as the powder material, Al is in a chemically stable state, is extremely hard to oxidize even in air, and has extremely high uniformity. A highly pure mixed phase can be formed. Further, by using a powder having an average particle size of 20 to 50 μm and an Nb-Al alloy powder having an average particle size of 0.5 to 30 μm as the Nb metal simple substance powder, the obtained intermetallic compound-based alloy has a dense and fine structure. Will have.

Then, the powder consisting of this mixed phase is subjected to cold pressure type treatment to obtain Nb metal simple substance powder and Nb-A.
l Alloy powders have a relative density of 90 at a temperature at which they do not react with each other.
Perform a cold pressure molding treatment so that the content becomes at least%. When the pressure molding process is performed here, the Nb metal simple substance powder in the mixed powder is deformed by the stress so as to fill the spaces between the particles in the powder, and the resulting molded body becomes more dense. As described above, since the pressure molding is performed at a low temperature, it is possible to easily manufacture a molded body having a relatively high degree of freedom and a complicated shape, as compared with the case of heating and compressing with an apparatus such as HIP.

Next, the obtained compact is heat-treated in an oxygen-free atmosphere at a temperature lower than the solidus temperature in the alloy phase to obtain a mixed powder of Nb simple metal powder and Nb-Al alloy powder. By diffusing Nb and Al of
Stoichiometric single phase or non-stoichiometric composition 2
An Nb ₃ Al intermetallic compound-based alloy having a phase or a coexisting structure of two or more phases is produced. Here, the oxygen-free atmosphere means a vacuum atmosphere in which oxidation is unlikely to occur or an inert gas atmosphere such as Ar gas. The intermetallic compound-based alloy thus obtained is a homogeneous, strong, and dense sintered body, and has an ultrafine structure, so that it is an Nb ₃ Al intermetallic compound-based alloy excellent in mechanical properties. ing.

Further, by subjecting the sintered body, which has completed each process, to a hot compression molding treatment such as HIP at a temperature higher than the sintering temperature, diffusion in the alloy phase sufficiently progresses, and a uniform structure is obtained. The densification is achieved, and the mechanical properties of the sintered body are further improved.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described below with reference to the flow chart of FIG.

Example 1 Average particle size 20 μm, Purity 9
Atomized powder of Nb metal alone of 9.9% or more and an ultrafine powder of Nb ₃ Al alloy having an average particle size of 2 μm and a purity of 99.5% or more are mixed to a desired composition and mechanically stirred. When the Nb metal simple substance powder and the ultrafine particle powder of the Nb ₂ Al alloy are uniformly mixed by sufficiently stirring, the mixed powder is sealed in a mold,
A cylinder having a diameter of 10 mm and a length of 25 mm was produced by compression molding under a pressure of about 800 MP so that the relative density was 93% or more. Then, the obtained molded body is vacuumed at about 1700 ° C.
It was heated and held for 15 hours and then cooled to room temperature in an electric furnace. Cavities were not formed in the composition, and the relative density of the molded body after the heat treatment was 99.8% or more. Further, it was possible to obtain an intermetallic compound-based alloy containing Nb ₃ Al as a main constituent phase, which had a fine and uniform structure and was excellent in high temperature strength and mechanical properties.

<Comparative Example> Nb and Al having an average particle size of 10 μm
In the photograph of the cross-sectional structure of the sample prepared from the simple substance powder under the same conditions as in Example 1, a large cavity was generated in the structure when prepared from the simple substance powders of Nb and Al, and the relative density was 8
As low as 5%, the desired characteristics were not obtained.

Example 2 Average particle size 10 μm, Purity 9
An example of a case where atomization powder of Nb metal alone of 9.9% or more and ultrafine powder of NbAl ₃ alloy having an average particle diameter of 1 μm is used is shown. Al alloy powder from Nb ₂ Al alloy
The use of NbAl ₃ alloy powder having a large composition is an extremely effective method when considering the oxygen concentration of the compact. That is, the higher the Al composition of the Nb-Al alloy is, the more excellent it is in oxidation resistance, so that it is possible to lower the oxygen concentration in the Nb-Al alloy after molding. Further, by using NbAl ₃ alloy as an ultrafine powder, the reaction with the Nb metal simple substance atomized powder is promoted. A molded body was produced in the same manner as in Example 1 except for the sintering conditions. As a result, the relative density is also 99.9%
As a result, a sample of an intermetallic compound-based alloy containing Nb ₃ Al as a main constituent phase with high density and high uniformity could be prepared. The sintering was performed by holding at 1500 ° C. for 10 hours, then raising the temperature to 1700 ° C. and holding for 15 hours.

[0026]

According to the present invention, the high-temperature strength and mechanical properties are excellent by the process of mixing Nb metal simple substance powder having high ductility and Nb-Al alloy powder, compression molding, and sintering, and uniform in any shape. It is possible to obtain an intermetallic compound-based alloy having a high-density Nb ₃ Al as a main constituent phase.

[Brief description of drawings]

FIG. 1 is a flowchart of a method for producing an Nb ₃ Al intermetallic compound-based alloy according to the present invention.

[Explanation of symbols]

 HIP ... Hot isostatic pressing.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ken Yasuda 4026 Kuji Town, Hitachi City, Ibaraki Prefecture Hitachi Research Laboratory, Hiritsu Manufacturing Co., Ltd.

Claims (7)

[Claims] 1. A method for producing an Nb ₃ Al intermetallic compound-based alloy having Nb and Al as main components and having an A15 type crystal structure, wherein Nb is 83 to 96% by weight and Al is 4 to 17% by weight.
Nb metal simple substance powder and Nb so that the composition range of wt% is obtained.
-Al alloy powder is mixed to form a mixed powder in which each powder element is uniformly blended, the mixed powder is subjected to cold compression molding, and then sintered by heat treatment. A method for producing an Nb ₃ Al intermetallic compound-based alloy having the same. 2. The melt-pulverized powder, atomized powder or micro powder according to claim 1, wherein the Nb metal simple substance powder has an average particle diameter of 20 to 50 μm and the Nb-Al metal powder has an average particle diameter of 0.5 to 30 μm. Nb in alloying powder
Method for producing a Nb ₃ Al intermetallic compound-base alloy having an average particle size of the metal simple substance powder has an average particle size greater than A15 crystal structure of Nb-Al alloy powder. 3. The molten pulverized powder, atomized powder or microalloying powder of Nb-Al alloy powder according to claim 1 or 2, wherein the matrix of Nb-Al alloy powder is Nb ₂ Al, NbAl ₃ or a mixed phase thereof. And a method for producing an intermetallic compound-based alloy having an A15 type crystal structure. 4. The Nb metal simple substance powder and the Nb-Al alloy powder are alloyed with each other so that the mixed powder of the Nb metal simple substance powder and the Nb-Al alloy powder has a relative density of 90% or more. A method for producing an Nb ₃ Al intermetallic compound-based alloy having an A15 type crystal structure, which is cold uniaxially or isotropically compression molded under a stress capable of deforming Nb particles in a powder of Nb metal alone at a temperature not performed. 5. The Nb-metal simple substance powder and the Nb-metal single powder according to claim 1, wherein the mixed powder is subjected to a heat treatment at a temperature lower than a solidus temperature of an alloy phase existing in the mixed powder. A method for producing an Nb ₃ Al intermetallic compound-based alloy having an A15 type crystal structure in which an Al alloy powder is subjected to a diffusion reaction and finally a main constituent phase is Nb ₃ Al. 6. The method according to claim 1, 2, 3, 4 or 5.
Gas turbines, space-related equipment and transportation equipment using manufactured heat-resistant parts with complex shapes. 7. A superconducting material having a complicated shape, which is manufactured by the method according to any one of claims 1 to 5.