JPH06100973A - Tungsten alloy having fine crystal grains and method for producing the same - Google Patents

Abstract

(57) [Summary] [Object] To provide a tungsten alloy having a fine crystal structure, excellent strength and toughness and at the same time excellent ductility, and having little variation in these properties. [Structure] Ni and 50 to 99% by weight of W are main components, and the content of Fe as an impurity is 3% by weight or less,
A tungsten alloy comprising a fine matrix phase containing Ni and W as main components and spherical or ellipsoidal W particles having an average crystal grain size of 7 μm or less. This tungsten alloy is
It is manufactured by a solid-phase sintering method in which mechanical alloying and extrusion are performed while intentionally suppressing the inclusion of Fe, which is an impurity.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alloy containing tungsten (W) as a main component, and in particular, a tungsten alloy produced by a solid-phase sintering method, which has excellent strength and ductility and has small variations, and a method for producing the same. Regarding

[0002]

2. Description of the Related Art Alloys containing W as a main component, especially 90% by weight
The heavy metal containing W and Ni, Fe, Cr, Re, Cu, etc. as described above is used as a material such as a balancer material that makes use of high specific gravity and as a radiation shielding material.

Since such a tungsten alloy contains W, it has been conventionally manufactured by a sintering method. Typically,
W powder and Ni and / or Fe powder and the like are mixed, and a molded body of the mixed powder is sintered at 1400 ° C. or higher in a hydrogen atmosphere. This method is a so-called liquid phase sintering method, in which Ni and Fe having a lower melting point than W are alloyed with each other to form a liquid phase, and the liquid phase is spread all over the W particles to form Ni around the W particles, A structure in which a matrix phase composed of Fe, W, etc. is uniformly present, and a sintered alloy having a density of 99% or more is obtained.

As described above, since the conventional tungsten alloy is manufactured by the liquid phase sintering method, the Ostwald growth of W particles cannot be avoided in the liquid phase sintering process. as a result,
Even if the particle size of the W raw material powder is several μm, the W particle size abnormally grows up to about 50 μm due to Ostwald ripening. Therefore, the conventional tungsten alloy has a rough crystal structure and is inferior in strength and toughness.

On the other hand, it may be considered to manufacture a tungsten alloy without using the liquid phase sintering method. That is, it is possible to manufacture by a solid-phase sintering method in which a liquid phase does not occur in the sintering process, but the conventional solid-phase sintering method does not sufficiently form the matrix phase, and the matrix phase can sufficiently surround the W particles. Therefore, it is difficult to obtain a tungsten alloy having excellent mechanical properties, and only a tungsten alloy having poor ductility can be obtained.

Japanese Patent Publication No. 2-24882 describes that solid-phase sintering is performed by using a prealloy powder in which a metal forming a matrix phase such as Ni or Fe is wrapped around W particles. . However, since such a prealloyed powder has a polygonal shape instead of a spherical body shape, the W particles have a high degree of proximity (continuity), and thus the obtained tungsten alloy tends to be particularly inferior in ductility. In order to avoid this, as described in JP-A-61-104002, it is necessary to generate a liquid phase for a very short time, but this method is possible in a laboratory. Is extremely difficult to implement on an industrial scale.

[0007]

From such conventional circumstances, the inventors of the present invention basically use the solid phase sintering method instead of the liquid phase sintering method in which W particles grow abnormally. It has been proposed to produce a tungsten alloy having excellent mechanical properties (see Japanese Patent Application No. 3-163172).

The above method is a method in which a mechanical alloying step and a solid phase sintering step are combined, and the W element is supersaturated in Ni or Fe by mechanical alloying and further promoted by mechanical alloying. By utilizing this diffusion phenomenon, W particles are grown in Ostwald in a solid state. Therefore, as a result of suppressing unnecessary growth of the W particles, the W particles have a fine spherical body shape and W
The proximity of particles to each other is lowered, and a tungsten alloy having excellent strength and toughness can be obtained.

However, the tungsten alloy obtained by the above method has a drawback in that it cannot be said that the ductility is good and that the ductility varies greatly. This tendency is greater for alloys having a higher W concentration, and particularly when the W concentration is 90% by weight or more, not only the ductility becomes extremely large, but also the strength often decreases.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the drawbacks of the tungsten alloy obtained by the above method and to provide a tungsten alloy having excellent strength and toughness as well as excellent ductility.

[0011]

In order to achieve the above object, the tungsten alloy proposed by the present invention comprises Ni and 5
0 to 99% by weight of W as a main component, Fe as an impurity content of 3% by weight or less, a matrix phase of Ni and W as main components, and a spherical body having an average crystal grain size of 7 μm or less It is a tungsten alloy having fine crystal grains, characterized by comprising W particles.

The method for producing a tungsten alloy having fine crystal grains according to the present invention comprises: (a) pure W powder and pure Ni powder, or pure W powder and W-Ni alloy powder, wherein W is 50 to 99% by weight. After blending to a composition of
(b) The obtained mixed powder contains 500 pp of impure gas component.
a step of performing mechanical alloying in an inert gas of m or less or in a vacuum at a temperature of 80 ° C. or less under the condition that the Fe concentration as an impurity is 3% by weight or less, and (c) the obtained mechanical alloying Powder in vacuum at 30
Encapsulating in a container at a temperature of 0 to 1430 ° C., (d)
The mechanical alloying powder enclosed in the container is
Hot extrusion at a extrusion ratio of 2 or more at a temperature of 00 to 1430 ° C.

[0013]

[Function] As a result of repeated studies on the cause of lowering the mechanical properties of the tungsten alloy, particularly the ductility, the presence of Fe ₇ W ₆ and FeWO ₄ which are intermetallic compounds of Fe and W has a great influence, and It has been found that Ni ₄ W, which is an intermetallic compound, does not hinder anything. In addition, Ni ₄ W has an ordered lattice and an irregular lattice, and in both of them, a composite state of them (in many cases, one exists as a precipitate of the other, for example, an ordered lattice). It was found that even if the grains precipitate in the disordered lattice phase), the mechanical properties are not adversely affected.

In the conventional method, Fe is usually used.
Even if a raw material powder not containing is used, most mechanical alloying devices such as attritors and ball mills are made of Fe alloys such as SUS, so that Fe is inevitable when ordinary mechanical alloying is performed. It is mixed in as an impurity, and this Fe becomes an intermetallic compound such as Fe ₇ W ₆ when heated and deteriorates the mechanical properties of the alloy.

Therefore, in the present invention, in order to eliminate or reduce the presence of Fe ₇ W ₆ as much as possible, Fe, which was indispensable for liquid phase formation in the liquid phase sintering method, is not used as an essential component, and the mechanical alloy is used. In the ing process, it is necessary to intentionally avoid mixing Fe as a pollutant. That is, according to the study by the present inventors, if Fe ₇ W ₆ is less than 5% by weight of the alloy, it does not adversely affect the mechanical properties such as ductility, and therefore the contamination by the mechanical alloying step is required. It has been found that it is indispensable to suppress the content of Fe to 3% by weight or less of the whole, and ideally, it is effective to set Fe to 1/100 or less of Ni by weight.

As described above, in the tungsten alloy of the present invention in which the Fe content is suppressed to 3% by weight or less, Ni is a viscous element and has a crimping force, so that mechanical alloying is easily performed and ductility is improved. As a result of excellent extrudability, it became possible to increase the W content up to 99% by weight. Further, the composition of the matrix phase of the alloy is 75 to 85 atomic% of Ni.
And 15 to 25 atomic% of W and 3 atomic% or less of Fe, and the matrix phase in this composition range mainly contains the intermetallic compound Ni ₄ W of Ni and W. It was revealed that Ni ₄ W is usually contained in an amount of 5% by volume or more, and there is an ordered lattice and an irregular lattice, but it does not affect the mechanical properties of the alloy.

Since the tungsten alloy of the present invention is manufactured through solid phase sintering by temperature controlled mechanical alloying and extrusion as described below, a fine crystal structure is obtained and W particles are spherical. The average crystal grain size is 7 μm or less, and the matrix phase containing Ni and W as the main components is also extremely fine, for example, the average crystal grain size is 4 μm or less.

As a result, the tungsten alloy of the present invention is
As described above, not only can ductility be prevented from decreasing, but
An excellent strength of about 60 kg / mm ² or more is obtained. On the other hand, even if W particles are finely divided by solid phase sintering, when heated to a temperature at which a liquid phase occurs, the crystal grain size of the matrix phase increases and the strength remains around 110 kg / mm ^2. It has been found that, as with the particles, that the crystal of the matrix phase is fine, which is important for improving the strength.

Next, the method of the present invention will be described. The raw material powders are pure W powder and pure Ni powder or pure W powder and W-Ni.
The alloy powder is used, and the Fe powder is not used. These raw material powders are mixed in a composition such that the W content is 50 to 99% by weight. However, if the W concentration exceeds 99% by weight, only the crushing effect becomes strong during mechanical alloying, and it becomes difficult to obtain a good composite state. In particular, if W-Ni alloy powder is used, the amount of W powder that is difficult to mechanically alloy can be reduced.

The mixed powders which are blended and uniformly mixed as described above are compounded by mechanical alloying.
However, since W easily forms an intermetallic compound, it is harmful to Fe.
First of all, F which is an impurity so as not to generate ₇ W ₆ etc.
It is important that mechanical alloying is performed while suppressing the mixture of e to 3% by weight or less. For that purpose, it is necessary to control the size and amount of the balls, the ratio of the balls to the powder, the volume of the processing container, the processing atmosphere, the processing temperature, the number of revolutions, and the like. It is effective to make it.

As the processing atmosphere, the impure gas component is 50
Both atmospheres may be used alternately, in an inert gas of 0 ppm or less, preferably 50 ppm or less, or in a vacuum. or,
When the treatment temperature exceeds 80 ° C, the powder adheres to the inside of the container, so the upper limit is 80 ° C. If the treatment temperature is high or the concentration of impurities such as oxygen in the atmosphere is high, harmful intermetallic compounds are likely to be produced, and the ductility of the powder is reduced due to the formation, so that only the pulverizing action is required. It becomes stronger and the mechanical alloying phenomenon is less likely to occur.

Since the mechanical alloying powder obtained usually contains an oxygen component as an impurity,
In order to facilitate the sintering phenomenon after removing this,
It is preferable to perform heat treatment at 800 to 1430 ° C. in hydrogen gas or vacuum. Normally, heating is performed in hydrogen gas after reduction, and then heating is performed in vacuum.However, if the concentration of impurities such as oxygen is suppressed to a low level, these heat treatments do not have to be performed, and they are sealed in the next container. It is also possible to substitute heating in the process. The heat treatment and the subsequent encapsulation in a container may be performed after the mechanical alloying powder is cold or hot formed.

If the temperature of the heat treatment is less than 800 ° C., it is not effective, but if it exceeds 1430 ° C., the structure becomes coarse and should be avoided. That is, when the temperature exceeds 1000 ° C., Ostwald growth of W particles is likely to occur and the W particles become spherical, but when the liquid phase generation temperature of 1440 ° C. or higher, the average crystal grain size of the matrix phase exceeds 4 μm. , The strength of the alloy will decrease, so the maximum temperature is 1430 ° C.
And

Next, the mechanical alloying powder is filled in a container in a vacuum and sealed. It is desirable to remove the adsorbed components by heating the whole to a temperature of 300 to 1430 ° C. before sealing the container. The mechanical alloying powder may be hot-molded after being sealed in the container, or the mechanical alloying powder may be cold-molded before being sealed. The mechanical alloying powder enclosed in the container is 800-
Hot extrusion is performed at a temperature of 1430 ° C. and an extrusion ratio of 2 or more. In this encapsulation step and extrusion step, the effect of degassing may not be obtained or extrusion may not be possible if the temperature is lower than the lower limit temperature, but the upper limit temperature is the same as in the case of the heat treatment step. To get 14
Set to 30 ° C.

Further, in the conventional tungsten alloy containing Fe, a sufficient bonding force between powders cannot be obtained unless the extrusion ratio is 10 or more, but in the present invention in which Fe is suppressed to 3% by weight or less, the extrusion ratio is 10%. Even if it is smaller, good ductility and strength can be obtained, and particularly when the mechanical alloying powder is previously molded and solidified, the extrusion ratio can be reduced to 2. However, if the extrusion ratio is less than 2, a sufficiently dense extruded material cannot be obtained. Also, cracking tends to occur when the extrusion ratio becomes large, but the powder sealed in the container before extrusion is subjected to hot isostatic pressing (H
IP) treatment is effective in preventing cracking.

In the tungsten alloy obtained by such an extrusion process, the W particles and the matrix phase have an extremely fine crystal structure, and the W particles are not in a polygonal shape as shown in FIGS. 1 and 2, but the adjacent W particles are in contact with each other. Except for the part, it is basically spherical. However, depending on the conditions such as the extrusion ratio, spherical W particles are stretched in the extrusion direction at the outer peripheral portion of the extruded material, and as shown in FIG. May be W
The excellent mechanical properties achieved by making the particles spherical are unaffected by the deformation of the W particles into an ellipsoid. However, regarding the hardness, when the W particles have a spherical body shape, the micro Vickers hardness is 300 units, whereas when the W particles have an ellipsoidal shape, the hardness may increase to 400 units.

The extruded material thus obtained can be annealed, if necessary, in order to further improve the mechanical properties. The annealing conditions include a temperature of 700 ° C. or higher, preferably 900 ° C. or higher, and a time of 10 minutes or longer. However, if the annealing temperature exceeds 1350 ° C., the structure tends to coarsen, so the upper limit is 1350 ° C. Further, it has been found that the cooling rate from the annealing temperature is preferably a rapid cooling rate of 14 ° C./minute or more up to 700 ° C. in order to maintain excellent ductility.

The tungsten alloy of the present invention is similar to the conventional heavy metal or tungsten alloy in that Re,
By adding elements such as Co, Cr, Mo, and Cu (excluding Fe), or performing post-processing such as forging and swaging, it is possible to strengthen the alloy and improve the mechanical properties. For example, by adding Re, the alloy is hardened, the strength is increased, and solid solution strengthening can be expected.

[0029]

Example 1 Pure W powder and pure Ni powder were mixed in a W: Ni weight ratio of 9: 1.
After being blended so as to achieve the following, they were mixed for 30 minutes in an Ar gas atmosphere using a ball mill. 2 kg of the obtained mixed powder
To a SUS304 attritor and adjust the oxygen concentration to 8
Mechanical alloying was carried out in an Ar gas atmosphere maintained at 0 ppm or less at a rotation speed of 200 rotations / minute at an average temperature of 73 ° C. The processing time of this mechanical alloying was changed so that the processing time was 10 hours under the condition 1 and 40 hours under the condition 2.

The resulting mechanical alloying powders were all coarse powders containing 5% or more of +150 mesh, and it was considered that the mechanical alloying performed a sufficient pressure bonding action. Also, by observation with an optical microscope, Ni
It turns out that and W are in a composite state. Next, each mechanical alloying powder obtained under the conditions 1 and 2 was heat-treated at 1190 ° C. for 2 hours in vacuum.

After that, the mechanical alloying powder under the condition 1 was analyzed by the X-ray diffraction method. As a result, a peak of (Ni, Fe) was observed in addition to the peak of W.
The analysis detected W and Ni, but not Fe. Therefore, a small amount of Fe component was mixed as an impurity from the inner wall of the attritor treatment tank, but the powder composition was almost W and Ni.
It was found that Fe ₇ W ₆ does not exist.

On the other hand, in the mechanical alloying powder under the condition 2, it was found by the same analysis that 10 wt% or more of Fe ₇ W ₆ was present. Regarding the concentrations of Fe and oxygen in each powder, as a result of chemical analysis, the powder under the condition 1 had 0.18% by weight of Fe and 0.7% by weight of oxygen, and the powder under the condition 2 had 3% by weight of Fe. 0.1% by weight and 0.8 oxygen
% By weight.

1 of these mechanical alloying powders
After holding at 500 ° C. for 3 hours in a vacuum of 0 ⁻⁴ torr, each was filled in a mild steel container and hermetically sealed. The extrusion ratio of each powder enclosed in the container was 12 at 1250 ° C.
Was hot extruded under the conditions. The extruded material obtained from the powder having the mechanical alloying treatment time of 10 hours (condition 1) was designated as sample 1, and the extruded material obtained from the powder having the mechanical alloying treatment time of 40 hours (condition 2) was designated as sample 2.

When the extruded materials of the obtained samples 1 and 2 were observed with an optical microscope, FIG. 1 and its enlarged view of FIG.
As shown in Fig. 2, spherical W particles are uniformly compounded in the matrix phase, W particles with a particle size of 2.8 μm or more are not observed, and the average crystal particle size of the matrix phase is about 1.2 μm. Met. No cracks were observed in the extruded material of Sample 1, but cracks having a length of 5 to 10 mm in the extruded material of Sample 2 were about 10 mm in the direction perpendicular to the extrusion direction.
Occurred at the pitch of.

Next, a test piece having a cross-sectional diameter of 4 mm was cut out from each of the extruded materials of Samples 1 and 2 and a tensile test was conducted at room temperature. As a result, Sample 1 has a tensile strength of 170.2 kg /
The mm ² and the elongation were 19.0%, and in the sample 2, the tensile strength was 160 kg / mm ² and the elongation was 11%. or,
Regarding the variation, Sample 1 had a tensile strength of ± 2% and elongation of ± 5%, and Sample 2 had a tensile strength of ± 5% and an elongation of ± 10%.

Example 2 Pure W powder and pure Ni powder were mixed in a W: Ni weight ratio of 7: 3.
After being blended so as to achieve the following, they were mixed for 30 minutes in an Ar gas atmosphere using a ball mill. 4 kg of the obtained mixed powder
Was transferred to another Ni alloy ball mill, and the oxygen concentration was adjusted to 80
Mechanical alloying was carried out at an average temperature of 80 ° C. for 50 hours in an Ar gas atmosphere maintained at a ppm or less.

The mechanical alloying powder obtained is +
It was a coarse powder having 250 mesh of 4% or more, and it was considered that the compression bonding action by mechanical alloying was sufficiently performed. Further, it was found by observation with an optical microscope that Ni and W were in a composite state.

This mechanical alloying powder was cold-molded by a die press, the molded body was sealed in a mild steel container in the same manner as in Example 1, and this was further extruded at 1230 ° C. with an extrusion ratio of 12
Hot extruded. The matrix phase of the obtained extruded material had an average crystal grain size of about 1.1 μm, and the W particles were spherical and had an average crystal grain size of about 1.3 μm. Table 1 shows the results of the TEM-EDX analysis of the composition of this matrix phase.

[0039]

[Table 1] Matrix composition (atomic%) Fe Ni W 0.85 80.10 19.05 0.52 80.12 19.37 0.89 81.07 18.03 0.74 81.60 17.66 0.65 81.18 18.17 1.02 81.27 17.71 0.88 78.76 20.37 0.70 82.07 17.23 1.02 82.83 16.16 0.91 83.27 15.81 From this result, Fe is analyzed. Only a margin of error is mixed, and the matrix phase basically contains Ni and W as main components,
It was found that the composition was close to that of Ni ₄ W.

Next, the matrix phase of this extruded material was treated with TE.
M observation shows that there are innumerable 20-30Å particles and 300
Precipitated particles of about Å were observed, and these particles were confirmed to be a regular lattice Ni ₄ W by electron beam diffraction method in terms of composition almost equal to the composition of the matrix phase. Further, as a result of X-ray diffraction, Fe ₇ W ₆ was not identified.

A test piece similar to that of Example 1 was cut out from the above extruded material and subjected to a tensile test at room temperature. The tensile strength was 162.4 kg / mm ² , the elongation was 15.1%, and the variation was the tensile strength. Was ± 3% and elongation was ± 6%.
The extruded material was held at 1250 ° C. for 2 hours, rapidly cooled at a cooling rate of 14 ° C./min or more using a gas fan, and then subjected to the same test. The tensile strength was 148 kg / mm.
² and elongation reached 18%.

When the extruded material produced in the same manner was held at 1250 ° C. for 2 minutes, the average crystal grain size of the matrix phase was 4.5 μm and the tensile strength was 136.1 kg / mm ^2.
And elongation was 14%. Extruded material produced in the same way
When kept at 470 ° C. for 2 minutes, the average crystal grain size of the matrix phase became 6.5 μm and the tensile strength was 118.1 k.
The g / mm ² and the elongation were 34%. It can be seen that if the heating temperature is raised above the temperature at which the liquid phase is generated, the crystal grain size of the matrix phase increases and the strength sharply decreases.

For comparison, an extruded material was obtained in the same manner as in Example 2 except that mechanical alloying was performed using a SUS304 ball mill. As a result of similarly analyzing this extruded material, the concentration of Fe as an impurity was 3.2% by weight.
It was found that Fe ₇ W ₆ was contained in an amount of 5.4% by weight. The tensile strength of this extruded material is 149.1 kg.
/ Mm ² , elongation is 3%, variation is ± tensile strength
It was 13% and the elongation was ± 14%, which was inferior to the mechanical properties of the extruded material of Example 2.

Example 3 Pure W powder and pure Ni powder were mixed in a W: Ni weight ratio of 8: 2.
After being blended so as to achieve the following, they were mixed for 30 minutes in an Ar gas atmosphere using a ball mill. 3 kg of the obtained mixed powder
To a Ni alloy attritor and adjust the oxygen concentration to 80p
In an Ar gas atmosphere maintained at pm or less, 1 at a temperature of 60 ° C or less at a rotation speed of 175 rpm.
The mechanical alloying was performed for 0 hours.

The mechanical alloying powder thus obtained was kept in a hydrogen stream at a temperature of 1000 ° C. for 3 hours, and then,
The sample was kept at 1000 ° C. for further 2 hours in a vacuum of 0 ⁻⁴ torr. Next, this powder was held in a vacuum of 10 ⁻⁴ torr at 300 ° C. for 3 hours, then separately charged into two mild steel containers and hermetically sealed. The powder thus enclosed in each container was hot extruded under the conditions of an extrusion ratio of 3 at 950 ° C. and an extrusion ratio of 18 at 1250 ° C.

The extruded material obtained under the condition of the extrusion ratio of 3 had no cracks or voids, but the extruded material under the condition of the extrusion ratio of 18 had many fine cracks in the direction perpendicular to the extrusion direction. Admitted. However, the mechanical alloying powder enclosed in the container in the same manner as above was previously treated with HIP at 1300 atm and 1230 ° C. for 2 hours, and then similarly treated at 1250 ° C.
In the case of extrusion processing under the conditions of extrusion ratio of 18, no crack was observed and a good extruded material was obtained.

Example 4 Pure W powder, pure Ni powder, Re powder and Cr powder were mixed with W:
The ingredients were mixed so that the weight ratio of Ni: Re: Cr was 80: 13: 6: 1, and then mixed in an Ar gas atmosphere for 30 minutes using a ball mill. 3 kg of the obtained mixed powder was added to Ni.
The alloy was transferred to an alloy vibration mill, and mechanical alloying was performed at a temperature of 60 ° C. or lower for 30 hours in an Ar gas atmosphere in which the oxygen concentration was kept at 80 ppm or lower.

F in the obtained mechanical alloying powder
The e concentration was 0.38% by weight. This mechanical alloying powder is used in a vacuum of 10 ^-4 torr for 400 times.
After keeping at 0 ° C. for 3 hours, it was filled in a mild steel container and hermetically sealed. Next, the powder enclosed in the container was hot extruded at 1250 ° C. under an extrusion ratio of 14. When the extruded material was observed with an optical microscope, the W particles on the surface portion were in the shape of an ellipsoid having a short diameter of 3 μm or less and an aspect ratio of 3 or more. The micro Vickers hardness of the extruded material was about 430.

A test piece similar to that of Example 1 was cut out from the above extruded material and subjected to a tensile test at room temperature. The tensile strength was 174.0 kg / mm ² , the elongation was 13.0%, and the variation was the tensile strength. Was ± 3% and elongation was ± 7%.
Even when Re was added as a Ni-Re alloy powder, the tensile strength was 173.0 kg / mm ² and the elongation was 1
3.0%, variation is ± 3% in tensile strength and ± 6 in elongation
%, There was no big difference.

On the other hand, the weight ratio of pure W powder, pure Ni powder, Mo powder and Co powder is 90: W: Ni: Mo: Co.
The extruded material mixed in the ratio of 6: 3: 1 and manufactured in the same manner as above had a tensile strength of 172.0 kg / mm ² and an elongation of 14.0%.

[0051]

According to the present invention, W particles are basically formed into a fine spherical surface by the solid phase sintering method in which the mechanical alloying step and the extrusion step are combined while suppressing the incorporation of Fe as an impurity as low as possible. At the same time as forming the body, the matrix phase also becomes finer and adversely affects the mechanical properties of Fe ₇
It is possible to provide a tungsten alloy which is excellent in strength and ductility at the same time, and in which variations in these are extremely small by eliminating or suppressing the generation of W ₆ .

[Brief description of drawings]

FIG. 1 is a diagram schematically showing a metal structure composed of spherical W particles and a matrix phase in the tungsten alloy of the present invention.

FIG. 2 is an enlarged schematic view showing a metal structure composed of spherical W particles and a matrix phase in FIG.

FIG. 3 is a diagram schematically showing a metallographic structure composed of ellipsoidal W particles and a matrix phase in the tungsten alloy of the present invention.

Claims (11)

[Claims] 1. A matrix phase containing Ni and W of 50 to 99% by weight as a main component, Fe as an impurity of 3% by weight or less, a matrix phase containing Ni and W as a main component, and an average crystal grain size. A tungsten alloy having fine crystal grains, characterized in that it is composed of spherical W particles of 7 μm or less. 2. In addition to the spherical W particles, the minor axis is 7
The tungsten alloy having fine crystal grains according to claim 1, characterized in that it contains ellipsoidal W particles having an aspect ratio of 2 or more and having a size of not more than μm. 3. The intermetallic compound Fe ₇ W _{6 of} Fe and W contained in the alloy is less than 5% by weight.
A tungsten alloy having the fine crystal grains according to claim 1. 4. The matrix phase composition according to claim 1, wherein the composition of the matrix phase is 75 to 85 atomic% Ni, 15 to 25 atomic% W, and 3 atomic% or less Fe. A tungsten alloy having fine crystal grains according to claim 1. 5. The tungsten alloy having fine crystal grains according to claim 1, wherein the tungsten alloy has a precipitate in a matrix phase. 6. The tungsten alloy having fine crystal grains according to claim 1, wherein the precipitate is an ordered lattice of Ni ₄ W. 7. The average crystal grain size of the matrix phase is 4 μm.
The tungsten alloy having fine crystal grains according to any one of claims 1 to 6, wherein: 8. A method for producing a tungsten alloy having fine crystal grains according to claim 1, wherein (a) pure W powder and pure Ni powder or pure W powder and W—Ni alloy powder, wherein W is 5
After blending to a composition of 0 to 99% by weight, (b) mixing the obtained mixed powder with an impure gas component of 500 ppm or less in an inert gas or in a vacuum.
At a temperature of 0 ° C or lower, the concentration of Fe as an impurity is 3% by weight.
A step of performing mechanical alloying under the following conditions,
(c) The step of enclosing the obtained mechanical alloying powder in a container at a temperature of 300 to 1430 ° C. in vacuum, and (d) the mechanical alloying powder enclosed in the container at 800 to 1430 ° C. Hot extrusion under conditions of an extrusion ratio of 2 or more at a temperature, and a method for producing a tungsten alloy. 9. The mechanical alloying powder obtained in the step (b) is heated in a hydrogen gas or in a vacuum to a temperature of 800-800.
The method for producing a tungsten alloy having fine crystal grains according to claim 8, wherein the heat treatment is performed at 1430 ° C. 10. The mechanical alloying powder is hot formed after the step (c), or the mechanical alloying powder is cold formed before the step (c).
A method for producing a tungsten alloy having fine crystal grains according to claim 8. 11. The extruded material obtained in the step (d) is
11. Fine crystal grains according to any one of claims 8 to 10, characterized by being annealed at a temperature of 00 to 1350 ° C for 10 minutes or more and rapidly cooling from the annealing temperature to 700 ° C at a rate of 14 ° C / min or more. A method for manufacturing a tungsten alloy having: