JP2588890B2 - Forming method of Ti-Al based intermetallic compound member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for forming a Ti—Al-based intermetallic compound member by powder metallurgy, and particularly relates to a method for forming a dense Ti—Al-based intermetallic compound member. It relates to a molding method.

[Prior art and its problems] Conventionally, Ti-Al based intermetallic compounds (Ti ₃ Al, TiAl, TiAl
₃ ) are known to have excellent high-temperature strength and oxidation resistance. However, since this member has poor ductility at normal and high temperatures, it is difficult to form it by conventional processing techniques, and there is a problem that it cannot be used as a practical material.

As a means for solving this, for example, an attempt has been made to realize a Ti-37% Al alloy member (hereinafter,% indicates weight%) by a special extrusion processing method such as a lateral pressure addition extrusion method. Has not been put to practical use.

As another means, the present inventors have proposed a method of forming a Ti-Al-based intermetallic compound member by powder metallurgy as described in Japanese Patent Application No. 60-213386.

The present invention has been made as a result of the improvement and study of the above-mentioned prior application invention, and an object of the present invention is to provide a method for forming a Ti-Al-based intermetallic compound member having more excellent formability.

[Means and Actions for Solving the Problems] The present invention made to solve the above problems is based on Al 1
Al and Ti powders are mixed at a ratio of 4 to 63% by weight and 37 to 86% by weight of Ti, the mixture is degassed, and the relative density of the degassed mixture is compressed to 95% or more by extrusion. To form a powder compact, and the powder compact is subjected to hot isostatic pressing without encapsulation under a pressure condition of 200 atm or more and a temperature condition of forming a Ti-Al-based intermetallic compound. A cross-sectional area ratio R between the mixture before processing and the compacted powder after processing in the above-mentioned extrusion, wherein the powder particle size d of the mixture is
(Μm) and the following equation (1).

R ≧ (d / 44) ² (1) The main steps of the present invention are shown in FIG. 1, and a modification thereof is shown in FIG.

(Ti Powder Manufacturing Process I) In FIG. 1, Ti powder produced by a conventional powder production method or by cutting an ingot can be used, and the particle size is adjusted to 1000 μm or less. Is used. Here, the particle size means a size at which the ratio of particles having a size smaller than the size is 80% by weight or more. For example, the particle size is 105 μm
The particle size of the powder in which the following particles are 80% by weight or more of the whole is 10
5 μm.

In this case, if necessary, Ti and Al, Mo, V, Zr, B, Nb, Y,
An alloy powder with Mn, Si, W or the like may be used.

(Al Powder Manufacturing Step II) The Al powder is produced by a conventional powder manufacturing method, and desirably, the gas atomization method is preferable in terms of cost. Particle size is 1000
μm or less, and if necessary, Al, Ti, Mo, V, Zr,
An alloy powder with B, Nb, Y, Mn, Si, W or the like may be used.

(Mixing Step III) Next, the above Ti powder and Al powder were mixed with 14 to 63% of Al
Mix with a mixer at a ratio of 37-86%.

The above mixing ratio is for Al less than 14%,
If Ti and Ti are more than 86%, the resulting intermetallic compound is not obtained and the heat resistance is insufficient. On the other hand, even if Al is more than 63% and Ti is less than 37%, Ti-Al based metal This is because they do not become inter-compounds.

(Deaeration Step IV) Next, the mixture is stored in a container and deaeration is performed by a vacuum pump or the like. This is to remove the adsorbed gas and adsorbed water on the powder surface and to prevent oxidation in the subsequent steps. This deaeration treatment is preferably performed at a degree of vacuum of 10 Torr or less to prevent oxidation of the powder. In addition, this deaeration treatment is carried out at room temperature to 550 ° C, more preferably at 400 ° C.
It is preferable to carry out at a temperature of up to 550 [deg.] C., because the removal of adsorbed water and adsorbed gas becomes easier. If the temperature exceeds 550 ° C., an alloying reaction between Ti and Al may occur, which is not preferable.

(Extrusion Step V) Next, the degassed mixture is compressed to a relative density of 95% or more by extrusion to obtain a powder compact. Here, the relative density indicates the density of the mixture as a ratio (%) to the density when the mixture is completely densified.

In this extrusion step, a powder compact having a desired cross-sectional shape is extruded from an extrusion hole provided in the die by placing the mixture in a container and moving a die or a punch.

The extrusion ratio R (the ratio R between the cross-sectional area of the mixture before processing and the cross-sectional area of the powder compact after processing, that is, the opening area of the extrusion hole) in this extrusion step is the powder particle size d (μ) of the mixture.
m) is set to have the relationship of the following equation 1.

R ≧ (d / 44) ² (1) If the extrusion ratio R is out of this range, a sufficiently dense Ti—Al-based intermetallic compound member can be obtained without being encapsulated in the subsequent high-temperature and high-pressure step. Can not. The densification treatment by the extrusion is performed in the subsequent high-temperature and high-pressure step to make the alloying reaction easier. This extrusion process involves
It is performed at 550 ° C. or less so as not to cause an alloying reaction with Al. Therefore, the powder compact is densified, but no Ti-Al-based intermetallic compound is formed.

(High-temperature high-pressure step VI) The powder compact is HIPed.

The HIP processing pressure is set to at least 200 atm or more, preferably 500 to 7000 atm.

The HIP treatment temperature is from 550 ° C to the solidus temperature of the Ti-Al-based intermetallic compound, preferably from 1000 to 1400 ° C. This is 55
If the temperature is lower than 0 ° C, the alloying reaction between Ti and Al does not proceed, while if the temperature is higher than the solidus temperature of the Ti-Al-based intermetallic compound, the material partially dissolves and the shape as a member is maintained. Because it is not.

By the HIP treatment, Al is diffused into Ti to form a Ti-Al intermetallic compound. This HIP treatment is performed without encapsulating the powder compact in a capsule. At this time, a number of vacancies are generated due to the Kirkendall effect, that is, diffusion of Al, and the cavities are formed. These cavities are crushed by the high pressure used in the HIP process.

Through the processing steps I to VI described above, intermetallic compounds such as Ti ₃ Al, TiAl and TiAl ₃ are formed.

As described above, in the present invention, since the particle size d of the raw material powder and the extrusion ratio R in the extrusion step have a fixed relationship, the powder compact can be subjected to the HIP treatment without being encapsulated. The resulting Ti-Al-based intermetallic compound member is dense with suppressed generation of vacancies due to the Kirkendall effect.

Although the main steps of the present invention are as described above, if necessary,
The processing shown in FIG. 2 may be added.

(Process VII for producing powders of other metals and alloys) Additives necessary for Ti-Al intermetallic compound members, for example, Mo, V, Zr, B, Nb, etc., which are effective for improving ductility, are used alone or in alloy powder. And simultaneously with the Ti powder and the Al powder. At this time, the addition amount of each element is Mo 1 to 5%, V 1 to 5%, Zr 1 to 5%, and B 0.005 to 3 in the composition of the final intermetallic compound.
%, Nb1 to 30%, the effect of improving ductility is not seen below the lower limit of any element, and above the upper limit,
The effect of ductility improvement is almost saturated, and the strength characteristics are also reduced. In addition, when 0.1 to 5% of Y is added in addition to the above elements, generation of vacancies due to the Kirkendall effect is suppressed, and when 0.1 to 5% of Mn is added, generation of vacancies due to the Kirkendall effect is suppressed and ductility is suppressed. Improved, Si 0.05-5%, W 1.0-10%
When added, the oxidation resistance is improved.

(Compression Step VIII) The mixture after the mixing step III is subjected to cold isostatic pressing or uniaxial pressing to make the relative density 60% to 95%. At this time,
If the relative density is less than 60%, the shape as a compressed body cannot be maintained after compression, and if it is more than 95%, the deaeration cannot be effectively performed.

(Vacuum sealing step IX) The compressed body after the degassing treatment IV is sealed in a container such as a can in a vacuum state.

(Forging Element Processing Step X) The compressed body that has been subjected to the extrusion step V is formed into a desired part shape or a shape close thereto by cold or hot forging or machining. This step is performed at a temperature lower than 550 ° C. so that an alloying reaction between Ti and Al does not occur. At this stage, since the Ti-Al-based intermetallic compound has not been formed yet, it can be easily processed.

In this process, after the deaeration step, if necessary, a Near Net Shape may be formed by powder forging or the like.

(Heat Treatment Step XI) After the high-temperature and high-pressure step VI, to make the concentration distribution of alloy elements present in the obtained Ti-Al-based intermetallic compound member more uniform, to further improve the relative density, or to make the Ti-Al
For the purpose of reducing the concentration of Cl, Mg or Na in the member which deteriorates the mechanical properties such as the fatigue characteristics of the system-based intermetallic compound member, the Ti-Al-based intermetallic compound is heated at 800 ° C.
To the solidus temperature of the Ti-Al intermetallic compound. During this heating, the pressure of the surrounding atmosphere may be adjusted. For example, when the atmospheric pressure is 10 ^{-10 to} 0.5 Torr, it is effective to reduce Cl, Mg, and Na. When the atmospheric pressure is 200 to 7000 atm, it is effective to make the relative density of the Ti-Al-based intermetallic compound 97% or more. is there.

(Finishing process XII) After the high-temperature and high-pressure treatment process, finish the shape of the final product by machining.

[Effects of the Invention] As described above, according to the present invention in which the particle size of the raw material powder and the extrusion ratio in the extrusion step have a predetermined relationship,
The high-temperature strength and oxidation resistance of the Al-based intermetallic compound member can be utilized, and the member can be easily formed into a desired shape by powder metallurgy.

Moreover, since capsules are not used in HIP processing, Ti-A
Production of the l-based intermetallic compound member becomes easier.

Example An example of the present invention will be described below.

First, Ti powder having the particle size shown in Table 1 and Al powder or Al powder
The alloy powder was mixed with a V-type mixer so as to have the composition shown in Table 1. This mixed powder was compression-molded by a cold isostatic press to make the relative density 68%.

Next, as shown in FIG. 3, the compression-molded body 10 was charged into an aluminum can 11, and a degassing pipe 12 was attached to the can end 11a.
Was welded. Thereafter, in a state that connects the vacuum pump (not shown) and heated for 1 hour at 450 ° C. in the pipe 12, 10 ^-3 Tor
Degassing was performed to a degree of vacuum of r or less.

Next, the compression molded body 10 was vacuum-sealed in the can 11 by crimping the degassing pipe 12. The compression-molded body 11 after the sealing was extruded at an extrusion ratio, an extrusion temperature of 450 ° C., and an extrusion ram speed of 8.3 cm / min in Table 1 to obtain an extruded rod. In this extruded rod, the Ti phase and the Al phase were in a mixed state, almost no Ti-Al-based intermetallic compound phase was found, and no cavities were observed in the structure.

Next, the aluminum member covering the outer periphery of the extruded rod was cut and removed to obtain a rod-shaped member having a diameter of 5 mmφ and a length of 30 mm.

Subsequently, a temperature of 1200 ° C. and a pressure of 1500
HIP processing was performed for 3 hours under the conditions of atm to obtain a sintered member.

In Samples Nos. 20, 21, and 22, the following heat treatments (a), (b), and (c) were performed after the HIP treatment.

(A) The vacuum was maintained at 10 ⁻³ Torr and 1000 ° C. for 10 hours.

(B) It was kept at 1300 ° C. for 3 hours in 1 atm of Ar gas.

(C) It was kept at 10 ^-3 Torr of vacuum and 1300 ° C. for 3 hours.

Thus, the relative density of the obtained sintered member was measured, and it was determined whether or not the obtained sintered member was suitable as a Ti-Al-based intermetallic compound member. It is shown in Table 1. In Table 1, those marked with ◎ have no voids due to the Kirkendale effect and have a relative density of 98% or more, and are particularly preferable. Those marked with ○ have no voids due to the Kirkendale effect and have a relative density of 95% or more. belongs to. In addition, those marked with “x” indicate that pores are observed and the relative density is less than 95%, and are unsuitable as Ti-Al-based intermetallic compound members.

FIG. 4 shows the relationship between the particle size d and the extrusion ratio R. ◎, 、, and × in the figure are the same as those in Table 1, and the number given beside this mark is the sample number.

From Table 1 and FIG. 4, in order to obtain a preferable Ti-Al-based intermetallic compound member having a relative density of 95% or more without encapsulation, it is necessary to determine the relation between the particle size d (μm) and the extrusion ratio R. It is understood that the relationship of R ≧ (d / 44) ² shown by oblique lines in the drawing needs to be established. Also, without encapsulation, particularly preferred relative density is 98% or more
In order to obtain a Ti-Al-based intermetallic compound member, the particle size d (μ
It is understood that it is necessary that a relationship represented by R ≧ (d / 13.9) ² be established between m) and the extrusion ratio R.

In Table 1, a Ti-Al-based intermetallic compound member is formed assuming that the particle size of Ti powder is the same as the particle size of Al powder or Al alloy powder. Table 2 shows the case where the particle size of the Ti powder and the particle size of the Al powder were changed to form a Ti—Al-based intermetallic compound member.

A Ti powder and an Al powder having the particle sizes shown in Table 2 were mixed in the same manner as in Table 1 to obtain a compression-molded body, and at the extrusion ratio shown in Table 2, the same as in Table 1 An extruded rod was used. This extruded rod was made into a rod-shaped member in the same manner as in Table 1 and HI
P processing was performed. The relative density of the thus obtained sintered member was measured in the same manner as in Table 1, and the result was determined. The determination result has the same meaning as in Table 1.

From Table 2, when the particle size of the raw material powder is various, if the above relationship is established between the maximum particle size d and the extrusion ratio R, the powder should be encapsulated as in Table 1. It was confirmed that a preferable Ti-Al-based intermetallic compound member could be obtained by HIP treatment.

Tables 3 and 4 show the amount of powder that does not satisfy the relationship between the particle size and the extrusion ratio in the raw material powder when the extrusion ratio is fixed at 6, and the determination results of the obtained sintered members. This shows the relationship.

In Tables 3 and 4, since the extrusion ratio is 6 in both cases, the particle size of the raw material powder is determined from the relationship between the particle size and the extrusion ratio.
When it is 105 μm or less, HIP processing becomes possible without encapsulation.

Therefore, the amount of powder larger than 105 μm for each raw material powder was adjusted, and the ratio (% by weight) of the amount of powder larger than 105 μm for the whole raw material powder was calculated, and the raw material powder was sintered in the same manner as in Table 1 above. Processing was performed.

As a result, in the case of the compositions shown in Table 3 and the compositions shown in Table 4, when the total of particles larger than 105 μm is 20% by weight or less, that is, when the particles of 105 μm or less are 80% by weight or more, It was confirmed that HIP treatment could be performed without encapsulating in HIP.

Therefore, even if the particle size of each raw material powder does not satisfy the above relationship, if the overall particle size satisfies the relationship between the particle size and the extrusion ratio, without encapsulation, dense Ti-Al A system-based intermetallic compound member can be obtained.

As described above, from Tables 1 to 4 and FIG.
When a predetermined relationship is established between the particle size d of the raw material powder and the extrusion ratio R in the extrusion process, the Ti-Al-based metal obtained by performing the HIP treatment without encapsulating the compact of the powder in a capsule. It was confirmed that the inter-compound member was suppressed from generating voids due to the Kirkendall effect and became dense.

[Brief description of the drawings]

FIG. 1 is a process diagram showing a molding method of the present invention, FIG. 2 is a process diagram showing a modification of FIG. 1, FIG. 3 is an explanatory diagram for explaining a process according to an embodiment of the present invention, FIG. FIG. 3 is an explanatory diagram for explaining the relationship between the particle size and the extrusion ratio.

Claims (1)

(57) [Claims] An Al and Ti powder are mixed in a ratio of 14 to 63% by weight of Al and 37 to 86% by weight of Ti, the mixture is degassed, and the relative density of the degassed mixture is extruded. To form a powder compact by compressing the powder compact at a pressure of 200 atm or more,
-Ti subjected to hot isostatic pressing without encapsulation under the temperature conditions that form Al-based intermetallic compounds
A method of molding an Al-based intermetallic compound member, wherein the cross-sectional area ratio R of the mixture before processing and the powder compact after processing in the extrusion is determined by the powder particle size d (μ)
m) and the following formula 1
A method for forming a Ti-Al intermetallic compound member. R ≧ (d / 44) ² … (1)