JP3062743B2 - Hydrogen-containing titanium-aluminum alloy powder, method for producing the same alloy powder, sintered titanium-aluminum alloy, and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method of subjecting a massive titanium sponge (titanium) to a hydrogen absorption treatment, and directly performing mechanical absorption (including mechanical alloying) from the massive titanium sponge containing the hydrogen. Aluminum (herein, “system” as used herein means a component system whose main component is titanium-aluminum and which allows the inclusion of other components without losing the properties of the main component. The term “system” used in the above has the same meaning.) It forms an alloy, a hydrogen-containing titanium-aluminum alloy powder and a method for producing the alloy powder, and a titanium-aluminum alloy sintered body and The present invention relates to a method for manufacturing a sintered body.

[0002]

2. Description of the Related Art In recent years, intermetallic compounds such as titanium-aluminum, nickel-aluminum, iron-aluminum, and iron-cobalt have attracted attention as heat-resistant materials. In ordinary alloys, heterogeneous atoms occupy each lattice position of the crystal irregularly, but the intermetallic compound has a specific deformation behavior because the position occupied by each constituent atom is specified and an ordered structure is formed. . For example, an increase in deformation temperature up to a certain temperature range shows a strengthening phenomenon that appears to be abnormal, such as an increase in strength, which is one of the factors that attracts attention as a heat-resistant high-strength material.

[0003] Among the above intermetallic compounds, TiAl
Titanium-aluminum intermetallic compounds such as titanium and Ti3Al are low in specific gravity, light in weight, and excellent in heat-resistant specific strength, and therefore attract attention as structural materials for engine parts and the like exposed to high temperatures such as aircraft and automobiles. ing. As a method for producing a titanium-aluminum alloy, a so-called smelting method of melting and casting raw materials is generally considered.
At the time of solidification, titanium having a higher specific gravity than aluminum causes component segregation (gravity segregation) due to gravity, and the crystal grains are also 10%.
There is a disadvantage that the desired good material cannot be obtained by coarsening to 0 μm or more. Furthermore, since this melting method requires an expensive melting apparatus such as a vacuum arc melting furnace, it is not easy to produce a titanium-aluminum-based intermetallic compound having desired characteristics.

It is said that powder metallurgy is effective as an alternative to such a melting method. In producing the titanium-aluminum intermetallic compound by this powder metallurgy method, in order to obtain fine and uniform equiaxed crystals and to improve the mechanical properties, a hard ball was put with titanium powder and aluminum powder. In a container (mill), it is necessary to repeat the mixing, crushing, and pressing of the powder to form an alloy (by mechanical milling), so-called mechanical alloying.

Conventionally, when titanium-aluminum intermetallic compound powder is produced by mechanical alloying, an inert atmosphere such as argon or the like is used to prevent oxidation of the raw material titanium powder, aluminum powder, and intermetallic compound powder. Ball milling has been performed under reduced pressure. However, in the case of using this method, the generation rate of the intermetallic compound powder is low even after long-time milling, and most of the powder adheres to the inner wall of the mill or the surface of the milling ball and remains unreacted. . As described above, the mechanical alloying method is effective in producing a homogeneous and fine intermetallic compound powder, but such poor yield is a fatal drawback from the viewpoint of economy. As a method of preventing such adhesion to the inner wall of the mill, there are attempts to mill in a nitrogen or ammonia atmosphere or to add an organic solvent such as heptane. This method can increase the synthesis yield to nearly 100%. However, such an additive is not a preferable method because carbides and nitrides are formed and have a significant effect on the structure and mechanical properties of the sintered body of the titanium-aluminum intermetallic compound powder. From the above, at present, the mechanical alloying method of titanium-aluminum has not reached a fundamental solution.

[0006] For these reasons, it has been proposed to use titanium hydride powder instead of pure titanium powder. According to this, the synthesis yield can be increased to 95% or more, carbides and nitrides are not generated, and fine titanium hydride and α
-It can be a powder of a structure in which titanium is dispersed in aluminum. Further, since hydrogen is dissociated at about 500 ° C., a sintered body of a titanium-aluminum-based intermetallic compound can be easily obtained. Furthermore, there is an advantage that titanium hydride is inexpensive (20 to 30% cheaper) than pure titanium powder used in a conventional mechanical alloy. However, since the homogeneous fine pure titanium powder, which is a starting material suitable for use in the mechanical alloy described above, is too expensive, even if titanium hydride powder is used, it is 20 times less than the pure titanium powder. Just being 30% cheaper has to say that it is still not practical.

[0007]

SUMMARY OF THE INVENTION The present invention uses the above-mentioned hydrogen-containing titanium sponge,
Efficient mechanical milling or mechanical alloying with pure aluminum is possible, further improving the yield of titanium raw material and reducing the cost, and a method for producing the hydrogen-containing titanium-aluminum alloy powder and the alloy powder It is another object of the present invention to obtain a titanium-aluminum alloy sintered body and a method for producing the same.

[0008]

Means for Solving the Problems In order to solve the above-mentioned problems, as a result of research conducted by the present inventors, the use of pure titanium powder inferior in yield or conventional titanium hydride powder has been
Using hydrogen-containing sponge titanium obtained by devising hydrogenation conditions such as particle size adjustment and pressure and temperature, it has become possible to produce a titanium-aluminum alloy sintered body with further reduced cost. is there. As a result, it has been found that hydrogen-containing titanium-aluminum-based alloy powder and titanium-aluminum-based alloy (intermetallic compound) sintered body can be obtained with high reproducibility under stable production conditions.

[0009] Based on this finding, the present invention contains 1 hydrogen at a content of 3.5 mass% or more and a particle size of 1 to 20.
2 mm hydrogen-containing titanium-aluminum-based alloy powder 2 comprising 3.5 mass% or more of hydrogen-absorbed hydrogen and having a particle diameter of 1 to 20 mm. For producing hydrogen-containing titanium-aluminum alloy powder characterized by ball-milling aluminum powder, grains or pieces in an argon atmosphere. 3 Contains 3.5 mass% or more of hydrogen and has a particle size of 1 to 20.
mm sponge titanium and aluminum powder, granules or pieces
A titanium-aluminum-based alloy sintered body characterized in that a hydrogen-containing titanium-aluminum-based alloy powder consisting of the following is used as a raw material and the content of a gas component such as oxygen is 500 ppm or less. Sintering a hydrogen-containing titanium-aluminum alloy powder obtained by mechanical milling of titanium sponge with aluminum powder, grains or pieces, wherein the content of gas components such as oxygen is 500 ppm or less. And a method for producing a sintered alloy.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Titanium sponge having a size of 50 mm or less sieved is charged into a furnace (electric furnace or the like), and is placed in a hydrogen stream of 1 to 5 atm, preferably 1 to 2 atm, for 300 to 500 atm.
Heat to ° C for 1 minute to 1 hour. The particle size of the titanium sponge is more preferably 10 mm or less for hydrogen absorption treatment (containment), crushing (miniaturization) and uniform mixing. Here, the term "hydrogen absorption treatment (containment)" is used because it contains adsorbed hydrogen. In many cases, it is considered that hydrogenation is progressing, but this point is a peculiar phenomenon of hydrogen gas flow treatment of titanium sponge, and needs to be distinguished from titanium hydride powder. It is considered that the adsorbed hydrogen is further hydrogenated in the milling treatment with aluminum powder described later. The absorption capacity (inclusion) of hydrogen into titanium sponge is extremely high. This is considered to be due to the sponge structure increasing the contact area with the hydrogen gas. In conventional hydrogenation treatment of pure titanium powder,
In a manufacturing process for refining pure titanium, a large amount of oxygen is absorbed and an oxide film is formed on the surface of the pure titanium powder. This results in a reduction in the strength of the titanium-aluminum sintered product, but the present invention has a great advantage that such uptake of oxygen hardly occurs.

The titanium sponge having a particle size of about 10 mm is about 1
It becomes hydrogen-containing in 0 minutes and becomes brittle enough to collapse with a finger. The pressure of the hydrogen stream is 1 to 5 atm, though it depends on the structure of the furnace. Atmospheric pressure can be sufficiently achieved at 1 atm. At a negative pressure, outside air may enter, and when the pressure exceeds 1 atm, there is a risk of hydrogen leaking out. Therefore, 1 atm or its vicinity (about 1 to 2 atm) is preferable. When hydrogen is contained, the heating temperature of the titanium sponge in the furnace is important. For example, even if the sponge titanium of 3 mm is kept at room temperature of 15 atm for 24 hours,
Hydrogen hardly occurs, and titanium sponge does not become brittle. Therefore, in order to efficiently obtain hydrogen-containing titanium sponge, it is necessary to perform the operation in the above-mentioned temperature range and pressure range, and further in the range of the particle size of titanium sponge.

The titanium sponge thus subjected to the hydrogen absorption treatment contains 3.5 mass% or more of hydrogen. Next, the hydrogen-absorbed titanium sponge and aluminum powder, particles or pieces are placed in a container (mill) and ball-milled using a rotary ball mill or a planetary ball mill.
Ball milling is performed in an atmosphere of an inert gas such as argon or helium or in a vacuum in order to prevent the invasion of the air and the oxidation of the powder due to the milling. When the above-mentioned aluminum pieces (cut pieces or the like) are used, the oxygen content is lower than when the same powder is used, and the oxygen content in the alloy mixed powder and the sintered body can be further reduced. About 10-2
As a result of milling for 00 hours, an alloy mixed powder in which aluminum and hydrogen were dissolved in α-titanium was obtained. Almost no adhesion of aluminum or titanium to the inner wall of the mill container and the balls was observed, and a mixed powder was uniformly obtained at a yield of almost 100%. The sponge titanium that has been subjected to the hydrogen absorption treatment is easily embrittled and is finely pulverized, and the crushed hydrogen-containing titanium powder does not adhere to the inner wall of the mill itself. Further, it is considered that the hydrogen-containing titanium powder obtained by crushing the sponge titanium has an action of shaving off aluminum and titanium alone even if they adhere to the container. The milling time can be appropriately changed depending on the particle size of aluminum, the particle size of titanium sponge, and the conditions of the hydrogen absorption treatment so that a sufficient alloy mixed powder can be obtained.

The oxygen content in the titanium sponge obtained as described above is 0.05% or less. Since the titanium-aluminum alloy powder produced from the titanium powder and the aluminum powder by the above-described conventional method contains 0.5% to 5% of oxygen, there is a remarkable oxygen reduction effect. In addition, since there is no need to add nitrogen gas or heptane, which has been conventionally used to prevent powder adhesion to the inner wall of the mill container, titanium-aluminum of excellent quality that does not form carbides and nitrides. A system alloy powder is obtained. The titanium-aluminum alloy powder thus obtained is sintered using a vacuum hot press or the like. Dehydrogenation is performed at a temperature of about 500 ° C., and the temperature is raised to about 800 ° C. to 1200 ° C. to sinter. Since the atmosphere during the sintering is kept in a reducing state, it is not oxidized, and an alloy having a fine structure of a titanium-aluminum intermetallic compound (Ti3Al, TiAl) can be obtained. The remaining hydrogen is less than 5 ppm.

As described above, since the raw material of the titanium-aluminum alloy powder starts from titanium sponge, the cost has been significantly increased up to 10 to 20 μm.
m, it is not necessary to refine the pure titanium to about m, and because of the feature that the hydrogen-containing sponge titanium itself is extremely easy to pulverize, the hydrogen-containing titanium powder is finely divided and mixed with the aluminum powder or the aluminum piece. The alloying process is also easy, and the overall cost can be significantly reduced. The titanium-aluminum-based intermetallic compound sintered body thus obtained can significantly reduce the content of gas components such as oxygen, and is free of carbides and nitrides, and has a high density of intermetallic compounds. With a uniform organization,
It is a material with high heat resistance specific strength and high toughness. As a result, a material suitable as a structural material for an engine component or the like that is exposed to a high temperature such as in an aircraft or an automobile can be obtained.

[0015]

Examples and comparative examples are described below based on examples and comparative examples. This embodiment is merely an example, and the present invention is not limited to this example. That is, the present invention is limited only by the claims, and includes various modifications other than the examples included in the present invention. The following examples are preferred and representative examples of the present invention.

Example 1 High-purity 7-mm sponge titanium (oxygen content: 0.05)
mass% or less, iron 10 ppm or less, Ti 95.9 ma
ss% or more) in an electric furnace and placed in a hydrogen atmosphere at 1 atm.
Heated to 00 ° C. This heating was performed for 10 minutes, and then taken out of the furnace. The hydrogen content reached almost 4 mass%. The sponge titanium subjected to this hydrogen absorption treatment was so brittle that it could be easily crushed with a finger. This hydrogen-absorbed high-purity sponge titanium and aluminum powder (purity 99.9%, particle diameter 150 μm or less) are blended in a molar ratio of 1: 1.
0mm, 350mm inside length stainless steel (SUS30
4) Fill into a steel cylindrical mill container and add 12.7 mm
41.1 Kg of the steel ball (ball) was sealed. Next, after the mill container was evacuated with a rotary pump, high-purity argon gas was introduced, and the rotation speed was 7.43 rad / sec (7.
The ball milling was performed at 1.0 rpm. 200
By ball milling for a long time, an alloy mixed powder having a structure in which titanium hydride and α-titanium were finely dispersed in aluminum was obtained. Almost no adhesion of aluminum or titanium to the inner wall of the mill container and the balls was observed, and a uniformly mixed alloy mixed powder was obtained with a yield of almost 100%. Almost no mixing of oxygen was observed during the ball milling.

The titanium-aluminum alloy powder thus obtained was heated to 1100 ° C. by pulse current sintering. During this time, pressure was applied at a pressure of 50 MPa. Dehydrogenate at a temperature around 500 ° C. Hydrogen remaining in the final sintered body is 5 ppm or less. As a result, the titanium-aluminum intermetallic compound (Ti3Al
, TiAl) having a fine and dense structure. Since the above steps are performed in a reducing atmosphere in which hydrogen is present, oxidation of titanium sponge, aluminum powder, a mixed alloy powder thereof, and a sintered body hardly occurs, and the oxygen content is 0.05% or less. In addition, during ball milling, titanium and aluminum do not adhere to the inner wall of the mill or the balls, so there is no need to introduce nitrogen or the like for facilitating peeling, and carbides or nitrides caused by this are eliminated. It is not formed in the sintered body.
For confirmation, a test using an X-ray diffraction pattern was performed, but no X-ray diffraction peak of carbide or nitride was observed. Therefore, not only the heat-resistant specific strength of the titanium-aluminum intermetallic compound is high, but also the toughness is improved and an excellent sintered body is obtained.

Example 2 High-purity titanium sponge having a particle size of 3 mm (oxygen content of 0.1 mm).
05 mass% or less, iron 0.08% or less, Ti 99.7
mass% or more) was placed in an electric furnace and heated to 400 ° C. in a hydrogen atmosphere at 1 atm. This heating was performed for 10 minutes, and then taken out of the furnace. The hydrogen content reached almost 4 mass%. Although the particle size of titanium sponge is smaller than that of 7 mm in Example 1, hydrogen absorption progresses due to this,
In just 10 minutes, the titanium sponge had become so brittle that it could be easily crushed with a finger. From this result, it is understood that the hydrogen absorption treatment on the titanium sponge can be performed relatively easily and stably. Also, the smaller the particle size of the titanium sponge, the larger the hydrogen absorption capacity, but it is not necessary to employ a titanium sponge with an excessively small particle size in production. Using this hydrogen-absorbing titanium sponge, a titanium-aluminum intermetallic compound (alloy) was produced by milling and sintering with aluminum powder and aluminum pieces using the same apparatus and conditions as in Example 1. The same result as in Example 1 was obtained.

(Comparative Example) For comparison, pure titanium powder (purity: 99.7 mass) was used.
%) And pure aluminum powder (purity 99.9 mass%)
These are blended in a molar ratio of 1: 1 and the mixed powder is filled into a stainless steel (SUS304) steel cylindrical mill container having an inner diameter of 300 mm and an inner length of 350 mm,
Further, 41.1 kg of a steel ball (ball) of 12.7 mm was put therein and sealed. Next, after the mill container was evacuated with a rotary pump, high-purity argon gas was introduced, and the rotation speed was 7.4.
Ball milling was performed at 3 rad / sec (71.0 rpm). After the mechanical alloying, the mixed powder was taken out. However, the adhesion to the inner wall of the mill container was remarkable, and the yield of the mechanical alloying powder was almost 0%.

[0020]

According to the present invention, the hydrogen content obtained by devising the hydrogen absorption treatment conditions such as the particle size adjustment and the pressure and temperature, instead of the conventional use of pure titanium powder having poor yieldability or titanium hydride powder. The use of titanium sponge makes it possible to produce a titanium-aluminum-based alloy sintered body with further reduced costs. By setting the temperature conditions in a hydrogen gas stream, titanium sponge with a particle size of 7 mm can achieve hydrogen content in 1 hour and titanium sponge with a size of 3 mm can be achieved in about 10 minutes, and these become brittle enough to collapse with a finger.
And, since the hydrogen-containing sponge titanium itself is extremely easy to pulverize, the steps of finely pulverizing the hydrogen-containing titanium powder and mixing and alloying with the aluminum powder are also easy, and a large Cost can be reduced. In addition, the titanium-aluminum-based intermetallic compound sintered body obtained by sintering the hydrogen-containing sponge titanium and aluminum powder, titanium-aluminum-based alloy powder prepared from grains or pieces, significantly reduces the content of gas components such as oxygen. It is possible to obtain a material having a dense and uniform structure of an intermetallic compound, a high heat resistance specific strength, and a high toughness without the inclusion of carbides or nitrides, and obtaining these at low cost. It has the remarkable feature of being able to do it. As a result, there is a great merit that a material suitable for a structural material such as an engine component exposed to a high temperature such as an aircraft or an automobile can be obtained.

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁷ Identification code FI C22C14 / 00 C22C14 / 00Z (56) References JP-A-10-195504 (JP, A) JP-A-10-96003 ( JP, A) Materia, Vol. 34, no. 5, p p. 611-613 (1995) (58) Fields investigated (Int. Cl. ⁷ , DB name) B22F 9/04 B22F 1/00 C22C 1/04

Claims (4)

(57) [Claims] 1. A hydrogen-containing titanium-aluminum alloy powder comprising 3.5 mass% or more of hydrogen and comprising titanium sponge having a particle size of 1 to 20 mm and aluminum powder, particles or pieces. 2. The method according to claim 1, wherein the hydrogen having been subjected to the hydrogen absorption treatment is 3.5 mass
%. A method for producing hydrogen-containing titanium-aluminum alloy powder, comprising ball milling sponge titanium having a particle size of 1 to 20 mm and aluminum powder, particles or pieces containing at least 1% in an argon atmosphere or vacuum. 3. The method according to claim 1, wherein the hydrogen content is at least 3.5 mass%.
Sponge titanium and aluminum having a diameter of 1 to 20 mm
A hydrogen-containing titanium-aluminum alloy powder consisting of powder, particles or pieces is used as a raw material, and the content of a gas component such as oxygen is 50%.
A titanium-aluminum-based alloy sintered body characterized by being at most 0 ppm. 4. A method for sintering a hydrogen-containing titanium-aluminum alloy powder obtained by mechanical milling of titanium sponge containing 3.5 mass% or more of hydrogen and aluminum powder, grains or pieces, such as oxygen. A method for producing a titanium-aluminum alloy sintered body having a gas component content of 500 ppm or less.