JPH05239571A - Production of ti-al intermetallic compound - Google Patents

Abstract

PURPOSE:To produce a Ti-Al intermetallic compound excellent in oxidation resistance at high temp. as well as in ductility at ordinary temp. by performing prescribed homogenizing treatment. CONSTITUTION:A Ti type material and an Al type material are mixed, deaerated, and subjected to vacuum sealing. The resulting sealed powder mixture is subjected to plastic deformation at a temp. not higher than the reaction synthesis temp. to undergo reaction sintering. Further, after the reaction synthesis, homogenizing heat treatment is done in a nonoxidizing atmosphere for >=0.2hr at a temp. in the range between 1170 and <1400 deg.C where Ti3Al is allowed to disappear. By this method, the Ti-Al intermetallic compound having a composition consisting of 40-50 atomic % and the balance essentially Ti can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a Ti-Al intermetallic compound used in fields such as automobile fields, aerospace fields, industrial machinery fields, etc., where light weight heat resistance or high specific rigidity is required. ..

[0002]

2. Description of the Related Art In recent years, for example, in the field of automobiles, there has been a demand for weight reduction and higher performance.
The parts are also required to be lighter. For example, in engine valves, steel or Ni alloy has been conventionally used, but these have a large density of about 8 g / cm ³ . Therefore, if the weight of this valve is reduced, the inertial mass of the valve can be reduced, so that the engine can be rotated at a high speed and the performance of the vehicle is expected to be improved.

Therefore, as a material which is lightweight and has heat resistance, a Ti--Al based intermetallic compound has been attracting attention.
For example, T at 800 ° C near the operating temperature of the exhaust valve
The high temperature strength of the i-Al intermetallic compound is almost the same as that of SUH35, which is a typical valve steel, and the density is about 1/2. Therefore, the Ti-Al-based intermetallic compound is considered to be a powerful lightweight heat resistant material.

[0004]

However, Ti-
Practical use of Al-based intermetallic compounds is hindered mainly due to the following reasons. Since it is a difficult-to-process material, it is difficult to give shape to parts.

The oxidation resistance is not always sufficient. Poor room temperature ductility. Therefore, in order to overcome these problems, various researches and developments have been conducted in recent years. For example, reduction of difficulty in imparting a shape of Ti-Al intermetallic compound (Japanese Patent Publication No. 1-308
98) and improvement of oxidation resistance (Japanese Patent Application No. 3-18).
453)). The contents of this research are specifically Ti powder or Ti alloy powder and Al powder or A powder.
1 alloy powder, mixed, deaerated, and further vacuum sealed,
The present invention relates to a technique for producing a Ti—Al-based intermetallic compound by plastically deforming a vacuum-filled mixed powder at a temperature lower than the reaction synthesis temperature, and heating the plastically deformed mixture at a temperature higher than the reaction synthesis temperature to perform reaction sintering. ..

However, even by the above-mentioned reaction sintering technique, the room temperature ductility is not sufficiently improved, and the oxidation resistance of the above is locally oxidized at a high temperature exceeding 950 ° C. There is not always enough. The present invention has been obtained as a result of conducting multifaceted research on the improvement of the properties of Ti-Al-based intermetallic compounds, and its object is to achieve excellent room temperature ductility by performing a predetermined homogenization treatment. Moreover, it is to provide a method for producing a Ti-Al-based intermetallic compound having excellent oxidation resistance at high temperatures.

[0007]

In order to achieve this object, the invention of claim 1 is to mix the Ti-based material and the Al-based material, perform deaeration and vacuum encapsulation, and then, enclose the mixed powder. Is plastically deformed below the reaction synthesis temperature, and the plastically deformed mixture is heated to the reaction synthesis temperature or higher to perform reaction sintering, and Al: 40-50 at% balance Ti-Al-based intermetallic a method of manufacturing a Ti-Al system intermetallic compound to produce a compound, wherein after the reaction synthesis, in a non-oxidizing atmosphere, 1170 ° C. for Ti ₃ Al disappeared
The gist is a method for producing a Ti—Al-based intermetallic compound, which is characterized by performing homogenizing heat treatment for 0.2 hours or more in a temperature range of 1400 ° C. or higher.

According to the second aspect of the invention, the additional element X is M
0.5 to 3 at% of the final composition after reaction synthesis of at least one or more of n, Cr and V, and / or after reaction synthesis of at least one or more of Nb, Mo, W, Ta and Si as an additional element Y. The final composition of T contains 0.5 to 3 at%
The gist of the method for producing a Ti-Al intermetallic compound according to claim 1 is to produce an i-Al intermetallic compound.

According to the invention of claim 3, Ti-X alloy powder, Al
-X alloy powder, Ti-Y alloy powder, Al-Y alloy powder,
The Ti-Al-based intermetallic compound is produced by using at least one or more of a Ti-XY alloy powder and an Al-XY alloy powder.
A gist is a method of manufacturing an Al-based intermetallic compound.

Now, the reason for defining the numerical values of each claim will be described. 1) Temperature: 1170 to 1400 ° C. Below the lower limit, all the heterogeneous coarse particles are homogeneous (Ti ₃ A
In some cases, the ductility cannot be improved because the structure cannot be changed to l (α ₂ ) + TiAl (γ)). On the other hand, when the amount exceeds the upper limit, part of the material is dissolved or the crystal grains are abruptly coarsened, resulting in a decrease in strength.

2) Temperature: 0.2 hours or more and less than the lower limit, all the heterogeneous coarse particles are homogeneous (α ₂ +
γ) The structure may not be changed, and the ductility and oxidation resistance may not be improved. Incidentally, usually, if it exceeds 250 hours, the improvement of ductility and oxidation resistance is saturated, which is uneconomical.

3) Al: 40 to 50 at% When the ratio is out of the upper and lower limits, the ductility decreases in all cases. 4) X: 0.5 to 3 at% Addition amounts within this range have the effect of improving room temperature ductility, but below the lower limit the effect is not observed, while above the upper limit the effect saturates. , There is a bad effect of increasing the density. Of these, Mn has the effect of preventing the generation of pores within this range.

5) Y: 0.5 to 3 at% Addition amounts within this range are effective in improving oxidation resistance, but below the lower limit, no such effect is observed, while above the upper limit, the effect is not achieved. Is saturated and has an adverse effect of increasing the density.

That is, the room temperature ductility is further improved by the addition of the X component, and the high temperature oxidation resistance is remarkably improved when the Y component is added. When these are combined, particularly excellent room temperature ductility is obtained. And high temperature oxidation resistance is achieved. When adding each X, Y component, X, Y
When added in the form of alloy powder of the components and Ti, Al,
It is suitable because the intermetallic compound is likely to be homogeneous.

The above-mentioned homogenizing heat treatment can be carried out subsequently to the reaction synthesis, for example, in HIP (hot isostatic pressing).

[0016]

The present invention was obtained as a result of multifaceted research on improvement of ductility and oxidation resistance of Ti-Al intermetallic compounds obtained by the reaction sintering method. By controlling the heat treatment after reaction sintering,
Ti-, which has a uniform composition and excellent room temperature ductility and high temperature oxidation resistance
An Al-based intermetallic compound can be manufactured.

When the Ti-Al material produced by the reaction sintering method was poor in room temperature ductility and poor in high temperature oxidation resistance, it was investigated and examined in detail.
Α-Ti phase surrounded by ₂ (Ti ₃ Al) phase, or Ti
-There are coarse inhomogeneous particles of 50 μm or more (hereinafter abbreviated as coarse particles) consisting of rich α ₂ phase, and these coarse particles serve as the starting point of fracture and reduce the ductility of this material. It was revealed that the oxidation was easy to proceed in the area.

In the present process, the coarse particles are
The powder and the Al powder are mixed, degassed, and vacuum sealed, and then the sealed mixed powder is plastically deformed at a temperature lower than the reaction synthesis temperature, which corresponds to Ti particles of 50 μm or more in the plastically deformed mixture. As a result, it became clear that coarse grains should be eliminated in order to improve the ductility and oxidation resistance of this material.

Therefore, in the present invention, the temperature at which the α ₂ phase disappears, that is, 1170, in the non-oxidizing atmosphere after the reaction synthesis.
By subjecting to a homogenizing heat treatment in a temperature range of ℃ or more and less than 1400 ℃ (refer to the state diagram of FIG. 1) for 0.2 hours or more, coarse particles composed of α-Ti phase or Ti-rich α ₂ are produced. It is eliminated, thereby improving the room temperature ductility and the high temperature oxidation resistance.

Further, since diffusion in an intermetallic compound is generally slow, it takes an extremely long time to convert a heterogeneous coarse grain into a homogeneous phase, which is uneconomical. By the way, according to the Ti-Al system equilibrium phase diagram (Binary Alloy Phase Diagram, ASM, 198
6, p.193), the Ti-rich α ₂ phase disappears at about 1170 ° C. and changes to the β phase. Since this β phase has a disordered structure of bcc, it is expected that diffusion will be extremely faster than that of the α ₂ phase, which has an ordered crystal structure of hcp. In addition, the α-Ti phase, which has a hcp structure and is slow to diffuse, changes to the β phase at 1170 ° C.,
It can be seen from the state diagram of FIG. As a result, by maintaining the temperature at 1170 ° C. or higher, the diffusion in the inhomogeneous coarse grains is promptly achieved, and the homogeneous state (α ₂ + γ at room temperature) of this material is realized in a short time.

[0021]

EXAMPLES Examples embodying the present invention will be described below together with comparative examples. (Example 1) Titanium sponge powder (149 μm or less) produced by the Na method and Al alloy powder (149 μm or less) produced by the helium gas atomization method were mixed so that the final composition would be Ti-48 at% Al. After that, it was inserted into an aluminum container, and vacuum evacuated while performing degassing while heating the inside of the container. Then, the container was hot extruded. The extrusion temperature was 430 ° C. and the extrusion ratio was 450. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample Nos. 1 to 4 in Table 1 below)
About, the reaction synthesis (560 ℃) was performed by HIP, and
After forming the i-Al intermetallic compound, the homogenization treatment was subsequently performed in HIP. The HIP conditions were that the atmosphere was argon gas and the pressure was 150 MPa. In addition, some samples (Sample Nos. 2 and 3 in Table 1) are HIP
After that, it was further heated in vacuum to carry out a homogenization treatment. The processing conditions and the like are shown in Table 1 below.

The T obtained by the above manufacturing method
Tensile test pieces were prepared for the i-Al intermetallic compound (diameter of parallel part: φ5 mm, gauge length: 15 mm) and a tensile test (strain rate: 10 ⁻³ / sec) was performed at room temperature. Further, a high temperature oxidation test (950 ° C. × 50 hours) was carried out in the atmosphere. The results of this test are shown in Table 2 below.

As is apparent from Table 2, the samples Nos. 1 to 4 of this example all had a room temperature tensile strength of 370 MPa or more and a room temperature elongation of 0.52% or more. It is excellent in ductility and suitable. Further, the increase in oxidation is as small as 13 g / m ² or less, and the oxidation resistance is excellent.

Example 2 PREP (Plasma Arc Rotat)
Ti powder (2)
(50 μm or less) and Al powder (149 μm or less) produced by an argon gas atomization method with a final composition of Ti
After mixing so as to be -48 at% Al, the mixture was inserted into an aluminum container, and the inside of the container was evacuated while being evacuated to perform deaeration treatment. After mixing, the mixture was inserted into an aluminum container, and the inside of the container was evacuated while heating to perform deaeration. Then, the container was hot extruded. Extrusion temperature is 400
C., extrusion ratio was 450. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample No. 5 in Table 1) was subjected to homogenization by heating in a vacuum after reaction synthesis in HIP. The HIP conditions were such that the atmosphere was argon gas and the pressure was 150 MPa. afterwards,
The homogenization treatment was carried out at 1200 ° C. in vacuum. The processing conditions and the like are shown in Table 1.

A tensile test was conducted on the obtained Ti-Al intermetallic compound at room temperature in the same manner as in Example 1. The results of this test are shown in Table 2. As is clear from Table 2, the sample No. 5 has room temperature tensile strength of 393 MPa.
In addition, the room temperature elongation is 0.89%, and the strength and ductility are further excellent and suitable.

(Example 3) Al powder or Al-XY alloy powder (297 produced by the helium gas atomizing method)
and a sponge titanium powder (149 μm or less) produced by the Na method in the final composition of Sample No. 6 to
After mixing so as to obtain No. 22, the mixture was inserted into an aluminum container, and the inside of the container was evacuated while being evacuated to perform deaeration treatment.
Then, the container was hot extruded. Extrusion temperature is 450
C. and the extrusion ratio was 350. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample Nos. 6 to 22 in Table 1) was subjected to reaction synthesis by HIP (1300 ° C. × 10 hours) to obtain a Ti—Al-based intermetallic compound. That is, the reaction synthesis and the homogenization treatment were continuously performed as a series of treatments. The processing conditions are shown in Table 1. And the obtained Ti-Al
With respect to the intermetallic compound, a tensile test was carried out at room temperature and a high temperature oxidation test was carried out in the same manner as in Example 1.
The results of this test are shown in Table 2.

As is apparent from Table 2, sample No. 6-
No. 22 has room temperature tensile strength of 382 MPa or more,
Moreover, the room temperature elongation is 0.53% or more, which is preferable because it has excellent strength and ductility. Further, the increase in oxidation is as small as 15 g / m ² or less, and the oxidation resistance is excellent. In particular, M indicated by X in the table
In the case of adding n, Cr, and V in a predetermined amount (0.5 to 3 at%) (Sample Nos. 8 to 13 and Nos. 19 to 22), the room temperature tensile strength is all 415 MPa or more and the room temperature elongation is 1 .12
% Or more, which is more excellent in strength and ductility, and is preferable. In addition, in the case where Nb, Mo, W, Ta, and Si shown by Y in the table are added (Sample Nos. 14 to 21), the room temperature tensile strength is 402 MPa or more, and the room temperature elongation is 0.66% or more. In addition to being excellent in strength and ductility, it is suitable, and the increase in oxidation is as small as 6 g / m ² or less, and the oxidation resistance is also very excellent.

(Example 4) Ti produced by the PREP method
-4 at% V alloy powder (250 μm or less) and Al alloy powder (149 μ) produced by an argon gas atomizing method.
m) and the final composition of Ti-48 at% Al-2a
After mixing so that t% V, insert into an aluminum container,
While heating the inside of the container, the container was evacuated and deaerated. After the mixing, it was inserted into an aluminum container, and the interior of the container was evacuated while being heated to be deaerated. Then, the container was hot extruded. Extrusion temperature is 440 ° C,
The extrusion ratio was 350. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample No. 23 in Table 1) was subjected to a reaction synthesis in HIP and then a homogenization treatment. The HIP conditions were such that the atmosphere was argon gas and the pressure was 150 MPa. Then, vacuum homogenization treatment was performed at 1200 ° C. The processing conditions and the like are shown in Table 1.

Then, with respect to the obtained Ti--Al based intermetallic compound, a tensile test was carried out at room temperature in the same manner as in Example 1. The results of this test are shown in Table 2. As is clear from Table 2, the sample No. 23 has a room temperature tensile strength of 435 MPa and a room temperature elongation of 1.20, and is very excellent in strength and ductility and is suitable.

[0034]

[Table 1]

[0035]

[Table 2]

(Example 5) Al powder (297 μm or less) produced by the helium gas atomizing method and sponge titanium powder (149 μm or less) produced by the Na method were used as sample Nos. 24 to 27 in Table 3 in the final composition. After mixing so that
It was inserted into an aluminum container, and the interior of this container was evacuated while heating to degas. Then, the container was hot extruded. The heating temperature of the extrusion conditions was 450 ° C., and the extrusion ratio was 350. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample Nos. 24 to 27 in Table 3)
Was subjected to reaction synthesis by HIP (1300 ° C. × 10 hours) to obtain a Ti—Al-based intermetallic compound. That is, the reaction synthesis and the homogenization treatment were continuously performed as a series of treatments. Table 3 shows the processing conditions and the like.

Then, the Ti--Al based intermetallic compound thus obtained was subjected to a tensile test at room temperature and a high temperature oxidation test in the same manner as in Example 1. The results of this test are shown in Table 4. As is clear from Table 4, sample No.
All of 24-27 have room temperature tensile strength of 397MP.
It is preferable that it is a or more, the room temperature elongation is 0.55% or more, and the oxidation weight increase is 10 g / m ² or less. No remarkable improvement in ductility and oxidation resistance performance is necessarily seen. In addition, in the case of sample Nos. 25 and 27 with a large addition amount,
The effect was saturated.

[0039]

[Table 3]

[0040]

[Table 4]

Comparative Example 1 Using the extruded material (Sample Nos. 28 to 30 in Table 5 below) obtained in Example 1 above, HIP was performed.
A homogenization treatment was carried out after the reaction synthesis in. Table 5 shows the processing conditions. Then, the obtained Ti-Al-based intermetallic compound was subjected to a tensile test at room temperature and a high temperature oxidation resistance test in the same manner as in Example 1. The results are shown in Table 6.

As is clear from Table 6, the sample No. 28 of Comparative Example 1 is not preferable because the room temperature elongation is as small as 0.12 due to the low HIP temperature and the ductility is low, and further, the oxidation amount is increased. Also has a large oxidation resistance of 20 g / m ² . Further, the sample No. 29 is not preferable because the room temperature tensile strength is as low as 290 MPa due to the high HIP temperature and the strength is low. Further, the sample No. 30 is not preferable because the room temperature elongation is as small as 0.33 due to the short HIP temperature treatment time and the ductility is low, and the oxidation weight increase is also 23 g / m 2.
It has a large value of ² and poor oxidation resistance.

(Comparative Example 2) Al powder (297 μm or less) produced by the helium gas atomizing method and sponge titanium powder (149 μm or less) produced by the Na method were used as sample Nos. 31 and 32 in Table 5 in the final composition. After mixing so that
It was inserted into an aluminum container, and the interior of this container was evacuated while heating to degas. Then, the container was hot extruded. The extrusion temperature was 450 ° C. and the extrusion ratio was 350. The aluminum container was removed from the obtained extruded material to obtain a raw material for reaction synthesis.

This extruded material (Sample Nos. 31 and 32 in Table 5)
Was subjected to reaction synthesis by HIP (1300 ° C. × 10 hours) to obtain a Ti—Al-based intermetallic compound. That is, the reaction synthesis and the homogenization treatment were continuously performed as a series of treatments. Table 5 shows the processing conditions and the like.

Then, the Ti--Al based intermetallic compound thus obtained was subjected to a tensile test at room temperature and further to a high temperature oxidation resistance test in the same manner as in Example 1. The results of this test are shown in Table 6. As is clear from Table 6, the sample Nos. 31 and 32 of Comparative Example 2 have room temperature elongation of 0.22% or less and ductility because the Al content is out of the predetermined range. It is unfavorable because it is too low.
No. 1 has a large oxidation gain of 18 g / m ² and is poor in oxidation resistance.

[0046]

[Table 5]

[0047]

[Table 6]

That is, according to the method of manufacturing the Ti-Al intermetallic compound of the present embodiment, the material having the above-mentioned predetermined composition is homogenized under predetermined conditions, so that the properties of normal temperature tensile strength and elongation are improved. T, which is excellent as well as excellent in high temperature oxidation resistance
An i-Al-based intermetallic compound can be produced. On the other hand, in the comparative example, since homogenization treatment is not performed under the material or conditions of such composition, the room temperature tensile strength and elongation properties are poor, the room temperature ductility is not high, and the high temperature oxidation resistance is high. Since it is not so expensive, it is not always preferable as various structural materials.

The present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various modes within the scope of the gist of the present invention.

[0050]

As is clear from the above description, in the method for producing the Ti-Al intermetallic compound according to the first aspect of the present invention, after the reaction synthesis of Al and Ti having a predetermined composition, it is performed in a non-oxidizing atmosphere. Since the homogenization treatment is performed in the temperature range of 1170 to 1400 ° C., a lightweight heat resistant material having excellent room temperature ductility and high temperature oxidation resistance can be obtained.

Further, in the invention of claim 2, since the X component is added, there is an advantage that the room temperature ductility is further improved, and since the Y component is added, there is an advantage that the high temperature oxidation resistance is further improved. .. Moreover, in the invention of claim 3, since various alloys containing the X and Y components are used as the material, the obtained intermetallic compound is easily homogenized to obtain a compound excellent in room temperature ductility and high temperature oxidation resistance. can get.

[Brief description of drawings]

FIG. 1 is a phase diagram of a Ti—Al-based intermetallic compound.

Claims (3)

[Claims] 1. A Ti-based material and an Al-based material are mixed, deaerated, and vacuum sealed, and then the sealed mixed powder is plastically deformed at a temperature lower than the reaction synthesis temperature. Al: 40 to 50 at% balance Ti substantially consisting of Ti by reaction sintering by heating above the reaction synthesis temperature.
A method of manufacturing a Ti-Al system intermetallic compound to produce a -Al-based intermetallic compound, after the reaction synthesis, in a non-oxidizing atmosphere, Ti ₃ Al
A method for producing a Ti-Al-based intermetallic compound, which comprises performing a homogenizing heat treatment for 0.2 hours or more in a temperature range of 1170 ° C. or more and less than 1400 ° C. 2. The final composition after reaction synthesis of at least one of Mn, Cr, and V as the additional element X is 0.5 to 0.5.
3 at% and / or Nb, Mo, or Y as an additional element Y
The Ti-Al-based intermetallic compound according to claim 1, wherein a Ti-Al-based intermetallic compound containing 0.5 to 3 at% of the final composition after reaction synthesis of at least one of W, Ta and Si is produced. Method for producing intermetallic compound. 3. A Ti—X alloy powder, an Al—X alloy powder,
A Ti-Al-based intermetallic compound is manufactured by using at least one or more of Ti-Y alloy powder, Al-Y alloy powder, Ti-XY alloy powder, and Al-XY alloy powder. The method for producing a Ti-Al-based intermetallic compound according to claim 2.