JPH0445201A - Manufacture of nb-al series intermetallic compound sintered compact body - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing a sintered Nb-Al intermetallic compound body.

[Conventional issues]

Nb-Al based intermetallic compounds (Nb-AI based alloys) have a high melting point and high strength at high temperatures. For example, Nb.

The melting point of Al alloy is 1960℃, and the melting point of Nb2Al alloy is 18
10°C, the NbAl alloy has a melting point of 1550°C.

However, while the melting point of Nb is 2400°C, the melting point of Al is 660°C, and the difference in melting point is extremely large.
Since l evaporates, it is extremely difficult to obtain a Nb-Al alloy with a predetermined composition. Furthermore, methods for manufacturing molded products made of Nb-Al alloy include a method of melting and mixing both Nb and Al, or casting a mixture of Nb and Al.
One possible method is to spray a molten mixture of 30% to obtain Nb-Al alloy powder, and then shape and sinter the alloy powder.
As described above, the difference in melting point between Nb and Al is large, and it is extremely difficult to melt and mix the two. Another possibility is to mold and sinter a mixed powder of Nb powder and Al powder, but the difference in melting point between Nb and Al is large, and melting of AI occurs during sintering, resulting in large deformation of the compact. occurs, and it is extremely difficult to manufacture a shaped sintered body using such a mixed powder.

[Means to solve the problem]

The present invention, as a means for solving the above-mentioned conventional problems,
Nb powder and Al powder, or Nb powder and Nb-Al alloy powder, or Al powder and Nb-Al alloy powder, or N
B powder, Al powder, and Nb-Al alloy powder are mixed raw metal powders by mechanical alloying to produce Nb-Al powder.
The present invention provides a method for producing a sintered compact by injection molding or slurry casting using the intermetallic compound powder.

The Nb powder used in the present invention usually has a particle size of about 300 meshes, preferably about 250 meshes, and the Al powder used in the present invention usually has a particle size of about 350 meshes, preferably about 400 meshes. It is a powder with a particle size of .

The above-mentioned Nb powder and Al powder have an intermetallic compound obtained from Nb powder and Al powder.
b is mixed at a predetermined ratio containing 75% by weight or more. The Nb content of the intermetallic compound obtained is 75
If it is less than % by weight, the melting point of the intermetallic compound becomes low and the strength at high temperature decreases. A mixture of Nb powder and Al powder is made into an intermetallic compound by mechanical pulverization and mixing as described later, and during the mechanical pulverization and mixing, Al having a low melting point preferentially adheres to the pulverization and mixing device. Therefore, the Al ratio in the intermetallic compound obtained by mechanically pulverizing and mixing the mixed powder is smaller than the ratio of Al powder in the mixed powder of Nb powder and Al powder before mechanically pulverizing and mixing. Therefore, in order to obtain an intermetallic compound having a predetermined Nb-Al ratio, the mixing ratio of Nb powder and Al powder must be adjusted. By using Nb as a Nb source and mixing Al powder with it, the Al powder will be less likely to adhere to the grinding and mixing device, and the yield of Al will improve. Of course, in the present invention, Nb-Al alloy powder may be used as an Al source and Nb powder may be mixed therein, or Al powder and Nb powder may be mixed with Nb-Al alloy powder.

The mixed powder may further contain other metal powder (third metal component). Desirable metal powders include Be, Mn, and Si, which form a solid solution with AI.

Cu, Cr, vt Txt Lx* Mg, Zn
There are tAg, etc. The above metal powders may be used alone or in combination of two or more. The above metals are preferably mixed in a total amount of 15% by weight or less in the resulting intermetallic compound. Within the above range, the melting point and strength at high temperatures of the intermetallic compound will not be adversely affected.

The raw metal mixed powder is mechanically pulverized and mixed using a mechanical pulverizing and mixing device such as a grinder or a ball mill. Such mechanical pulverization and mixing causes atoms of the constituent metals of the raw metal mixed powder to penetrate and diffuse each other, and the metals react with each other to form the intermetallic compound. The intermetallic compound is further pulverized by mechanical pulverization and mixing, and the mutual diffusion reaction between the constituent metals further progresses. In this way, Nb-Al based intermetallic compound powder is obtained, which is pulverized until the average particle size of the powder becomes smaller than the average particle size of the raw metal mixed powder. A desirable average particle size is about 2011 m or less. Powders with an average particle size of about 20 μm or less exhibit good moldability.

In order to produce a molded body of the intermetallic compound powder of the present invention, the intermetallic compound powder is mixed with a thermoplastic plastic powder such as polyvinyl chloride, polyethylene, polypropylene, polystyrene, and if desired, wax, paraffin, etc. as a lubricant. The molded product is manufactured by injection molding the pellet. Alternatively, the intermetallic compound powder is dispersed in an organic solvent such as ethanol, isopropanol, n-hexane, etc., and if desired, a binder such as polyvinyl butyral, polyvinyl formal, polyvinyl methyl ether, polyvinylethyl ether, polyvinyl acetate, etc. A peptizing agent such as a sulfonate or an aliphatic sulfonate is added to form a slurry, and the slurry is cast into a casting mold to produce a molded body. The molded body thus obtained is usually heated to a temperature of 1,700 to
It is sintered by heating at a temperature of about 1900°C for about 2 to 4 hours, but if desired, it can be dried and degreased at a temperature of about 50°C before the sintering, and then heated at a temperature of about 1100 to 1300°C. Calculate.

The molded product produced by the slurry casting method described above is brittle and has poor sintering efficiency, especially in the case of a molded product with a complex shape. Therefore, the slurry is filled into a permeable ceramic casting mold and dried and degreased. However, it is desirable that the dried slurry be calcined together with the casting mold at a temperature of about 1100 to 1300°C.

After calcining, the calcined product is loaded together with a casting mold into a pressure vessel filled with pressure medium powder, and sintered by hot isostatic pressing.

[Effect]

Nb powder and Al powder, or Nb powder and Nb-Al alloy powder, or Al powder and Nb-Al alloy powder, or N
When raw metal mixed powders mainly consisting of B powder, Al powder, and Nb-Al alloy powder are mechanically crushed and mixed, interpenetration diffusion of metal atoms constituting the powder occurs between the powders, and Nb
and Al or other metals react with each other to form Nb-Al
A series of intermetallic compounds are formed. This reaction takes place at a relatively low temperature (A
(below the melting point of 1), Al does not substantially evaporate.

Therefore, the composition of the raw metal mixed powder and the composition of the obtained intermetallic compound do not vary widely. During the above reaction, the raw metal mixed powder is simultaneously ground to a smaller diameter, and an intermetallic compound having an average particle size smaller than the average particle size of the raw metal mixed powder is produced. Intermetallic compounds with such small particle sizes provide injection molding materials with good flowability and also provide a dense structure to the sintered bodies.

Furthermore, a solid solution is formed with AI in the raw metal mixed powder.Be, Mn, Si, Cu, Cr, V, Ti+Li, M
When a third metal component such as g, Zn, or Ag is added, sinterability is improved.

The Nb content of the obtained intermetallic compound should be greater than 75% by weight. This is because intermetallic compounds with a Nb content of 75% by weight or less have a low melting point and do not have sufficient strength at high temperatures.

Furthermore, when a third metal component is added, the total amount of the metal is 1
If the amount is 5% by weight or less, the metal will not adversely affect the melting point or strength of the intermetallic compound.

Furthermore, in the case of casting, if a casting mold made of liquid-permeable ceramic is used, it becomes possible to dry and degrease the slurry, calcining, and sintering within the casting mold.

〔Example〕

Example 1 (Production of intermetallic compound) Al powder of 400 meshes and Nb powder of 250 meshes were mixed so that Nb was 87% by weight and Al was 13% by weight, and the mixture was milled by a ball mill using hexane as a medium.
Mixed for 6 hours. The obtained mixed slurry is dried in a nitrogen atmosphere to obtain a raw metal mixed powder. 1 kg of the raw metal mixed powder was put into a ball mill with a diameter of 400 mm, 20 kg of balls were added, and mechanical pulverization and mixing were performed at a speed of 100 rpm. The relationship between the grinding and mixing time and the average particle size of the raw metal mixed powder is shown in FIG. As shown in Figure 1, the average particle size increases to approximately 500 μm at the initial stage of pulverization and mixing, but then gradually decreases to 192 μm.
In time, the particle size becomes about 20 μm or less, which is smaller than the initial particle size. Further, FIGS. 2a to 2f show the relationship between pulverization and mixing time and differential thermal analysis (the dotted line in the figure is a temperature increase curve). As shown in Figure 2a, the raw metal mixed powder has the melting point of Al (6
A remarkable peak indicating a large exotherm was observed near 60°C, but as shown in e, this peak was not observed after 192 hours of pulverization and mixing, indicating that most of Al reacted with Nb to form intermetallic compounds. It is recognized that

Therefore, when the raw metal mixed powder is shaped and sintered in a state before being pulverized and mixed, it is expected that Al will rapidly melt near the melting point, causing large deformation of the compact.
If the pulverization type is used for 92 hours, the reaction will proceed sufficiently, the heat generation near the melting point will be small, and the compact will be able to withstand sintering sufficiently.

The above mechanical grinding and mixing was continued for 384 hours, and the composition of the intermetallic compound obtained was 90.5% by weight of Nb and 9.5% by weight of Al, and the average particle size was about 15 μm.

Example 2 (Injection molding) The intermetallic compound powder obtained in Example 1 was classified using a 350 mesh sieve, and then an injection molding material having the following composition was prepared.

Intermetallic compound powder 58 parts by weight Synthetic resin additive $ 42 parts by weight Umbrella: The composition of the synthetic resin additive is as follows.

Polypropylene 55 parts by weight Paraffin wax 30 parts by weight Carnauba wax 13.5 parts by weight Dioctyl phthalate 1.5 parts by weight The injection molding material having the above composition is kneaded and pelletized by a pelletizer, and the pellets are heated to a cylinder temperature of 190 by an injection molding machine. °C, mold temperature 55 °C, injection pressure 500
A tensile test piece (1) having the shape shown in FIG. 3 was molded under the conditions of kgf/csi. In the test piece (1), the parallel part (2) has a thickness of 3 wn, a width of 4 rm, and a length of 14++.
m, grip part (3) is 3 mm thick, width Low, length 1
It is 2mm.

The above test piece was embedded in 100 meshes of fused alumina powder, and heated for 550 minutes at a heating rate of 5°C/hr in an Ar flow.
After degreasing by heating to 11:1, the temperature was raised to 1200''C in vacuum, and a calcined body was produced.

The obtained calcined body is taken out from the alumina powder, and after removing the alumina powder, it is set in a zirconia setter having a smooth surface, and sintered at 1800° C. for 3 hours in a vacuum.

The density of the obtained sintered body was 93.3%, and qualitative analysis by X-ray diffraction revealed that it was a single phase Nb3Al alloy. In addition, the results of the tensile test were 22 at 1300℃.
, 4 kgf/mm2.

Example 3 (Cast Molding 1) The intermetallic compound powder obtained in Example 1 is classified in the same manner as in Example 2 to prepare a slurry having the following composition.

Intermetallic compound powder 100 parts by weight Peptizer 1 Ammonia 0.05 Polyvinyl butyral 1 Ethyl alcohol 45 The above slurry was cast into a plaster mold with a diameter of 16 m and a length of 60 mm. After releasing the molded product, the molded product was heated at 60°C. Dry with.

The dried samples were sintered at 1800°C in vacuum. The density of the obtained sintered body was 94.2%, and it was a single phase of Nb3Al alloy. The results of the tensile test were 24,1 at 1300'C.
kgf/mn2.

Example 4 (Cast Molding 2) The slurry of Example 3 was cast into an air-permeable casting mold (11) made of ZrO2 as shown in FIG. After degreasing by heating to 550° C. in an air stream at a heating rate of 5° C./hr, evacuation was performed and the temperature was raised to 1200° C. in vacuum for calcining. The obtained sintered body (12) and the mold (11) were loaded into boron nitride (BN) powder (14) filled as a pressure medium in a tantalum container (13) as shown in FIG. ,
After evacuating and sealing the container (13) through the exhaust port (+3) A, hot isostatic pressing is performed at a pressure of 1000 atm and a temperature of 1700° C. for 1 hour to perform shaping and sintering.

The density of the obtained sintered body is 100%.

According to the method of this example, it is easy to obtain a molded article with a complex shape.

Example 5 The following Nb was used as an Al source in the raw metal mixed powder.
-Using Al alloy powder.

That is, alloys with various compositions were produced as ingots by the plasma skull melting method. The ingot was redissolved to produce a powder of 60 meshes by centrifugal spraying,
The powder was pulverized for 24 hours using an attritor to give a
It was classified using a mesh sieve to obtain a Nb-Al alloy powder sample having the composition and average particle size shown in Table 1.

Sample Al analysis value (weight %) average particle size (μm) A
93.7 18.4B 87,
2 16.7C74,315,6 D 29,1 13.1 1st
The above Nb-Al alloy powder was mixed with the Nb powder of Example 1 in the ratio shown in Table 2, and was mechanically pulverized and mixed in the same manner as in Example 1 to obtain a final product of 1:Nb, Al (Al content: 8. 8
The intermetallic compound powder was injection molded in the same manner as in Example 1, and then sintered to obtain a sintered compact. Table 2 shows the density and strength at 1300° C. of the obtained sintered compact.

Table 2 Looking at Table 2, it is found that as the Al content in the raw metal mixed powder increases, the density tends to increase slightly.

Example 6 An intermetallic compound powder was prepared in the same manner as in Example 5 using an alloy having a composition in which the Nb-Al alloy powder used in Example 5 was further added with a third metal component shown in Table 3. Using the intermetallic compound powder, injection molding was performed in the same manner as in Example 5, followed by sintering to obtain a sintered compact. Table 3 shows the degree of grain refinement, density, and strength at 1300° C. of the obtained sintered compact.

Table 3 Book □: The weight ratio of alloy powder and Nb powder is 6.4:93.6 as in Table 2 A of Example 6.

*2: The degree of grain refinement was measured using a cross-sectional photograph of the sample.

0: Finer grain than when using Nb-Al alloy powder.

△: Same as when using Nb-Al alloy powder.

x: It became coarser than when Nb-Al alloy powder was used.

Looking at Table 3, Mn, Sl, MgT Cr+ Tj
, V is effective in refining the crystal grains of the sintered compact, and Be, Mn, Si+ Cu, Li, Mgl
It is confirmed that the addition of ZntAg is effective in increasing the density of the sintered compact.

Example 7 (Cast molding 3) The wax matrix (21) of the tensile test piece shown in FIG. 5 (parallel part (22) thickness 10 mo, width 12 aa, length 40
mm.

Grip part (23) (7) Thickness 10+nm, width 20mn
, length 30an casting port (24) diameter 8 sides) Z r O
2 slurry was coated by a dipping method, and dried and sintered at 1800°C to produce an air-permeable casting mold. The slurry of Example 3 was poured into the air-permeable casting mold, and the slurry of Example 3 was deliquid-dried, degreased, and calcined in the same manner as in Example 4. (BN) powder and subjected to hot isostatic pressing under the same conditions as in Example 4. The density of the sintered compact thus obtained is 100%, 1
The strength at 300°C was as high as 38°1 kgf/+m''.

〔Effect of the invention〕

Therefore, in the present invention, Nb-Al of a desired composition
The intermetallic compound powder of the present invention can be easily obtained, and the powder has good injection moldability, and the molded body of the present invention obtained by injection molding or cast molding has excellent sinterability, has high density, and has good properties at high temperatures. A sintered compact with high strength can be obtained. In addition, Be, which forms a solid solution with Al in the intermetallic compound powder,
Mn, Si, Cu.

Addition of a third metal component such as Cr, V, Ti, Li, Mg, Zn, Ag, etc. is effective in refining the crystal grains and/or increasing the density of the sintered compact. Furthermore, if a casting mold made of breathable and liquid-permeable ceramic is used during casting molding, the slurry can be dried, degreased, calcined, and sintered in the casting mold, making it possible to sinter complex shapes. Even formed bodies can be easily produced.

[Brief explanation of drawings]

Fig. 1 is a graph showing the relationship between mechanical pulverization and mixing time and average particle size in Example 1, Fig. 2 a - f are graphs of differential thermal analysis of the composition during mechanical pulverization and mixing treatment, and Fig. 3 is a graph showing the relationship between mechanical pulverization and mixing time and average particle size. FIG. 4 is a perspective view of the test piece molded in Example 2, FIG. 4 is an explanatory diagram of the hot isostatic pressing step of Example 4, and FIG. 5 is a perspective view of the wax matrix of Example 7. In the figure, (1)... Test piece Figure 1 Boiling mill processing time (hrs) ℃

Claims (3)

[Claims] (1) A method for producing an Nb-Al intermetallic compound containing 75% by weight or more of Nb, comprising Nb powder and Al powder, Nb powder and Nb-Al alloy powder, or Al powder and Nb-Al alloy powder. , or Nb powder and Al powder and Nb
- Generating a Nb-Al based intermetallic compound by mechanical alloying of a raw metal mixed powder mainly consisting of -Al alloy powder, and converting the intermetallic compound into particles with an average particle size smaller than the average particle size of the raw metal mixed powder. A sintered shaped body of an Nb-Al based intermetallic compound, characterized in that the shaped body is produced by injection molding or slurry casting using Nb-Al based intermetallic compound powder obtained by pulverizing it until it has a diameter. manufacturing method (2) The raw metal mixed powder includes Be, Mn, Si, Cu, Cr, V, Ti, Li, which easily forms a solid solution with Al,
One or more metals selected from the group consisting of Mg, Zn, and Ag are mixed in the raw metal mixed powder so that the total amount of the metal is 15% by weight or less in the intermetallic compound. N according to claim 1 mixed with
b-Method for producing Al-based intermetallic compound sintered body (3) Step 1 of casting and drying the intermetallic compound powder slurry according to claim 1 into an air-permeable casting mold made of ceramics, the solidified slurry in the casting mold is temporarily removed together with the casting mold. Firing step 2: producing a sintered Nb-Al intermetallic compound body by loading the calcined product together with the casting mold into a pressure vessel filled with pressure medium powder, and sintering it by hot isostatic pressing. Method