JPH0791603B2 - Method for forming Ti-Al intermetallic compound member - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for molding a Ti—Al-based intermetallic compound member by powder metallurgy, more specifically, a hot isostatic pressing process without using a capsule ( Hereinafter, it will be referred to as HIP treatment).

[Background of the Invention is to Solve Problems] Conventionally, TiAl-based intermetallic compound (TiAl, Ti ₃ Al, etc.) are known to have excellent high-temperature strength and oxidation resistance. However, since this member has poor malleability at room temperature and high temperature, it is difficult to mold it by the conventional processing technique, 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% (hereinafter,% means% by weight) Al alloy member by a special extrusion processing method such as a lateral pressure addition extrusion method. , Has not been put to practical use.

Further, as another means, a method of forming a Ti-Al-based intermetallic compound member by a powder metallurgy method, as described in Japanese Patent Application No. 60-213386, and a HIP treatment using a glass capsule as an improvement thereof. The present inventors have proposed a method for producing a Ti—Al-based intermetallic compound by utilizing it. However, in the former case, a large number of holes may be generated in the molded body, while in the latter case, the holes can be eliminated, but the capsule forming process is complicated and the cost is increased.

The present invention has been made as a result of improvement and examination of the above-mentioned prior invention, and an object thereof is to provide a method for forming a Ti-Al-based intermetallic compound member which does not generate voids without using a capsule. To do.

[Means and Actions for Solving Problems] The present invention made to solve the above problems has a ratio of Al 14% by weight to 63% by weight, Mn 0.1% by weight to 5% by weight, and balance Ti. As described above, one or more of Al powder, Al-Mn alloy powder, and Mn powder are selected and mixed with Ti powder, and this mixture is vacuum degassed, densified while maintaining a vacuum, and then a sealed capsule is added to the mixture. Do not cover and heat at high pressure to fire Ti
A forming method for forming an Al-based intermetallic compound, the temperature range in which alloying progresses most during the temperature rise, 550 ° C to 650 ° C
Control the heating rate of 0.01 ℃ / min ~ 20 ℃ / min,
It is characterized in that it is heated and baked at a temperature of 700 ° C. or higher and below the solidus line of the mixture.

Here, the purity of each of Ti powder, Al powder, and Mn powder is
It means 90% or more, 95% or more, 95% or more.

In addition, the temperature range for temperature increase rate control is at least 550 ° C.
It is necessary to control the temperature up to 650 ° C, but it is desirable to control 450 ° C to 700 ° C in order to further improve the effect of the present invention.

Furthermore, it was found from experiments that the addition of Mn has the effect of suppressing the generation of vacancies due to the Kirkendall effect during the alloying of Al and Ti.

In addition, alloy powder of Ti, alloy powder of Al-Mn, alloy powder of Al, alloy of Mn with one or more elements of Mo, V, Zr, B, and Nb in the following ratios: The ductility effect may be added by adding the powder, or the elements alone or as an alloy powder.

1% ≤ Mo ≤ 5%, 1% ≤ V ≤ 5% 1% ≤ Zr ≤ 5%, 0.005% ≤ B ≤ 3% 1% ≤ Nb ≤ 30% Below, the main steps of the present invention are shown in Fig. 1, Furthermore, the modification is shown in FIG.

(Ti Powder Manufacturing Step I) In FIG. 1, the Ti powder may be manufactured by a conventional powder metallurgy method or by cutting an ingot or the like, and the particle size thereof may be 1000 μm or less. Use the adjusted one.

In this case, alloy powder of Ti and Al, V, Nb, B or the like may be used if necessary.

(Production process II of Al and Mn powder) The Al powder is produced by a conventional powder production method, and the gas atomization method is preferable from the viewpoint of cost. Granularity is 1000
Adjust to less than μm.

Mn is alloyed with Al to form an alloy powder, or is formed as a single powder.

If necessary, Al, Al-Mn or Mn, V, Mo,
You may use the alloy powder with Nb, B, etc.

(Mixing Step III) Next, Ti powder, Al powder, Al-Mn alloy powder, and Mn powder are appropriately selected so that the proportions of Al14% to 63%, Mn0.1% to 5%, and the balance Ti are obtained. Mix with a mixer.

The above mixing ratio is used because, if Al is out of the range of 14% to 63%, it does not become a single phase or two phases of Ti ₃ Al, TiAl, and TiAl ₃ -based intermetallic compounds. , Mn
If it is less than 0.1%, it is not possible to suppress the generation of voids due to the Kirkendall effect during high-temperature and high-pressure processing, and a dense molded body cannot be obtained. On the other hand, if the Mn content exceeds 5%, the ductility of the molded product is reduced and the oxidation resistance is deteriorated.

In order to further increase the strength, heat resistance, and suppression of pores, the mixing ratio is preferably Al25% to 45%, Mn0.
5% to 4%, Ti 51% to 74.5%, particularly preferably Al30
% -42%, Mn1% -3%, Ti55% -69%.

(Deaeration Step IV) Next, the mixture is placed in a container and deaerated by a vacuum pump or the like, or deaerated by a vacuum hot press. Vacuum degree is 10 ^-2 Torr or less, temperature is 200 ℃ ~ 500
It is desirable to carry out at ℃. This is to remove the adsorbed gas and adsorbed water on the surface of the powder and to prevent oxidation in the subsequent steps. The vacuum state after deaeration needs to be maintained until the subsequent densification treatment V.

(Densification treatment V) Next, the mixture after deaeration is densified to a density of 95% or more of the true density. This densification is carried out by extrusion or hot pressing when deaerated using an aluminum can, and by vacuum hot pressing when deaerated using a vacuum hot press machine. This treatment does not cause an alloying reaction.

(High-temperature high-pressure treatment VI) Next, HIP treatment is performed as high-temperature high-pressure treatment. This process is performed without covering the mixture with a closed capsule.

Regarding HIP treatment conditions, the temperature range in which alloying proceeds,
That is, the temperature rise rate in the temperature range of 550 ℃ ~ 650 ℃
The temperature is set to 0.01 ° C / min to 20 ° C / min, and thereafter, the temperature is kept at 700 ° C or higher and below the solidus line for about 10 minutes to 100 hours.

Among such heating conditions, the reason why the temperature range is limited as described above is that alloying is most promoted in this temperature range, and the range of the heating rate is set as described above. The reason is that if it is less than 0.01 ° C / min, it takes a long time and is uneconomical, and if it exceeds 20 ° C / min, many pores are generated.

In addition, the temperature range of the heating rate of 0.01 ℃ / min ~ 20 ℃ / min,
By expanding the range of 450 ° C to 700 ° C, the effect of suppressing pores can be further promoted.

In addition, keeping the temperature above 700 ° C and below the solidus is 700 ° C to accelerate the compound reaction and sintering.
This is because it is necessary to do the above, and at a temperature higher than the solidus, the material partially melts and the shape of the component cannot be maintained.

The pressure of HIP treatment is set to at least 200 kgf / cm ² to crush the holes.

In the above HIP treatment, Ti-A can be obtained by diffusing Al in Ti.
Form an l-based intermetallic compound. At this time, the Kirkendall effect, that is, the state in which vacancies are easily generated due to Al diffusion, but by adding Mn and setting the temperature rising rate as described above, the generation of vacancies is suppressed, The voids generated in the are also crushed by the high pressure treatment.

By the processing steps I to VI described above, an intermetallic compound such as TiAl, Ti ₃ Al or TiAl ₃ is formed.

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

(Powder manufacturing process VII of other metals and alloys) An additive element effective for the Ti-Al-based intermetallic compound member, for example, one or more kinds of Mo, V, Zr, B, and Nb which are effective in improving ductility , Ti powder, Al powder, etc. are mixed at the same time as their simple substance or alloy powder.

At this time, the addition amount of each element is Mo1% to 5%, V1% to 5%
%, Zr1% to 5%, B0.005% to 3%, Nb1% to 30%, and no effect of ductility improvement is observed below the lower limit of any element, and if the upper limit is exceeded, ductility is increased. The improvement effect is almost saturated, and the strength characteristics are also reduced.

(Compression step VIII) The mixture after the mixing step III is subjected to cold isostatic pressing or uniaxial pressing to bring the mixture to 60% to 95% of its true density. At this time, if it is less than 60% of the true density, the shape as a compressed body cannot be maintained after compression, and if it is 95% or more, the effect of degassing treatment IV cannot be obtained.

(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. After the densification process V in the subsequent step, the container such as a can is removed.

(Near Net Shape Forming Step X) The compressed body that has undergone the densification treatment step V is formed into a desired part shape or a shape close thereto by cold or hot forging, or by machining.

(Finishing molding process XI) After the high temperature and high pressure processing process VI, the shape of the final product is finished by machining or the like.

[Effects of the Invention] As described above, according to the present invention, while utilizing the excellent high temperature strength and oxidation resistance of the Ti-Al-based intermetallic compound member, the Ti-Al-based intermetallic compound member is easily formed into a desired shape by powder metallurgy. be able to. Moreover, even if the encapsulation step with the glass capsule in the HIP process is omitted, the generation of voids can be suppressed, and therefore the manufacturing can be facilitated.

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

First, sponge Ti of 48 mesh or less by the Hunter method
And Al powder of 100 mesh or less, Al-Mn alloy powder, Al-V alloy powder by a gas atomizing method using argon,
A Ti-Mn alloy powder was produced, blended so as to have the composition shown in Table 1, and mixed by a V-type mixer. This powder was compression molded by a uniaxial press to make its true density 80%.

Next, as shown in FIG. 3, the compression molded body 10 was loaded into an aluminum can 11 having a diameter of 68 mm, and a degassing pipe 12 was welded to the can end 11a. Then, connect a vacuum pump (not shown) to the pipe 12 and heat it at 450 ° C for 1 hour.
The degassing process was performed to a vacuum degree of 0 ^-3 Torr 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 encapsulation was densified by extruding at an extrusion temperature of 400 ° C. and an extrusion ratio of 15 to obtain an extruded rod having a diameter of 18 mm. In this extruded rod, the Ti phase and the Al phase were in a mixed state, the Ti-Al intermetallic compound phase was hardly found, and no void was observed in the structure.

Next, after cutting and removing the covering aluminum member, cold forging is performed to form a shape close to the finished product (Near
Net Shape).

Next, HIP without putting the forged material in a closed capsule.
Processed. As a HIP processing condition at this time, a program as shown in FIG. 4 was adopted.

That is, from room temperature to 450 ℃, 30 ℃ / min (01 → A1, 02 → A
2, 03 → A3, 04 → A4) heating at a heating rate of 450 ℃
Up to 700 ℃ under 1000kgf / cm ² pressure, 4 different heating rates, 0.1 ℃ / min (A1 → B), 4 ℃ / min (A2
→ B), 15 ° C / min (A3 → B), 30 ° C / min (A4 → B) heating rate, and further maintained at 1300 ° C for 2 hours under a pressure of 1800 kgf / cm ² (C → D). Next, it was cooled from 1300 ° C. to room temperature at a cooling rate of 30 ° C./min (D → E).

In the above steps, like Samples 1 to 11 shown in Table 1,
A Ti—Al-based intermetallic compound member was formed by changing the composition and the temperature rising rate, and the porosity of the member was measured by an image analyzer, and the results are also shown in Table 1. The porosity of 1% or less was judged as good (◯), and the porosity of more than 1% was judged as bad (x).

As is clear from Table 1, Mn was added and the temperature was 400 ° C.
Therefore, the porosity can be suppressed to 1% or less by setting the temperature rising rate from 750 ° C to 15 ° C / min or less.

That is, when Ti and Al form an intermetallic compound, the addition of Mn, the control of the heating rate, the holes that are easily generated by the Kirkendall effect are suppressed, the slightly generated holes are crushed by pressure. It was not observed, and it was a fine organization.

As a result of inspecting the products obtained by the above treatment, the samples No. 1 to No. 3 showed a tensile strength of 39 kgf / cm ² or more at room temperature.

Also, as shown in Table 2, along with Mn, V, Mo, Zr,
The porosity can be suppressed similarly by adding B.

[Brief description of drawings]

FIG. 1 is a process drawing showing a molding method of the present invention, FIG. 2 is a process drawing showing a modification of FIG. 1, FIG. 3 is an explanatory view explaining a process according to one embodiment of the present invention, and FIG. FIG. 4 is a diagram showing a heating step in high temperature and high pressure processing according to the same example.

Claims (1)

[Claims] 1. Al 14 wt% to 63 wt%, Mn 0.1 wt% to 5
One or more of Al powder, Al-Mn alloy powder, and Mn powder are selected and mixed with Ti powder so that the weight% and the balance Ti are in proportion, and this mixture is vacuum-degassed and the vacuum is maintained. It is a molding method of forming a Ti-Al-based intermetallic compound by heating and firing under high pressure without covering the mixture with a closed capsule after densification. ℃ ~ 650 ℃
Control the heating rate of 0.01 ℃ / min ~ 20 ℃ / min,
A method for forming a Ti-Al-based intermetallic compound member, which comprises heating and firing at a temperature of 700 ° C. or more and a solidus line of the mixture or less.