JPH05202437A - Production of inter-high-melting-metallic compound-base alloy - Google Patents

Abstract

PURPOSE:To obtain an inter-high-melting-metallic compound-base alloy represented by Nb3Al and excellent in formability and sintering characteristics and further to obtain a homogeneous inter-high-melting-metallic compound-base alloy containing the third high-melting element and excellent in strength at high temp. and toughness. CONSTITUTION:In a method for producing an (inter-high-melting-metallic compound Nb3Al)-base alloy, mechanical deformation is applied to a Nb3Al intermetallic compound having A15 type crystal structure to form a powder of nonequilibrium supersaturated solid solution with bcc type crystal structure by >=50% by volume ratio. The resulting bcc nonequilibrium supersaturated solid solution powder is compacted at a temp. not higher than the temp., 700 deg.C, at which transformation into A15 type crystal structure is brought about and is then heated at >=700 deg.C to undergo sintering and also transformation of a sintered compact into a stable structure. By this method. the (inter-high-melting- metallic compound Nb3Al)-base alloy composed essentially of A15 phase can be produced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention is represented by Nb ₃ Al, which is difficult to synthesize an alloy having an arbitrary shape and a uniform composition by a conventional casting or powder sintering method. The present invention relates to a method for producing a high melting point intermetallic compound-based alloy.

[0002]

2. Description of the Related Art Currently, various high-melting-point materials replacing Ni-base superalloys are being studied. Among these materials, high-melting-point intermetallic compounds, which have high temperature strength and are expected to impart ductility, have been attracting attention. There is. Among these, in particular, from the three points of high-temperature strength due to a high melting point near 2000 ° C., relatively low specific gravity, and A15 type crystal structure in which deformation can be expected to some extent, Nb ₃ Al is a heat-resistant material for ultra-high temperature which replaces Ni-base superalloy. Is being watched as.

However, this refractory intermetallic compound has a high melting point, the melting point difference between Nb and Al is close to 2000 ° C., and the specific gravity difference between Nb and Al is as large as three times or more. It is often difficult to apply conventional alloy manufacturing processes. For example, when trying to obtain an Nb ₃ Al-based alloy by a normal casting technique, it is difficult to obtain an alloy having a uniform and controlled composition due to the difference in the melting point and the specific gravity of Nb and Al, and it is difficult to cool the alloy. The problem has arisen that the alloy cracks due to thermal stress during the process.

Therefore, from the viewpoint of giving a shape and obtaining a sound heat-resistant component, powder metallurgy has attracted attention as a manufacturing process of Nb ₃ Al-based alloys. In Japanese Patent Laid-Open No. 3-229832, a method for producing an Nb-Al intermetallic compound is described as N.
b ₃ Al powder, Nb ₂ Al powder, and Nb powder were mixed and molded so that the atomic ratio of Nb and Al was 3: 1, and sintered at a temperature at which Nb ₂ Al melts to obtain high-density Nb- It is disclosed that an Al intermetallic compound is obtained.

[0005]

In the above-mentioned prior art, the ductility of the powder at the molding stage has not been improved, and it is difficult to manufacture heat-resistant parts of arbitrary complicated shapes. At the stage of molding the powder, it is necessary for each particle to deform and adhere to each other, so the higher the deformability (ductility) of the particle, the better the moldability. In the above-mentioned conventional technique, since the molded body is mainly composed of Nb ₃ Al, Nb ₂ Al particles having a complicated crystal structure, the ductility of the particles themselves is insufficient, and it is difficult to mold them into an arbitrarily complicated shape. It was

In the prior art, Nb,
Although Al or Nb ₂ Al is present, if the sintering is insufficient in the sintering step accompanied by alloying and some of these particles remain, the mechanical properties of the alloy are significantly deteriorated. These Nb ₂ Al and Al having a high melting point and a low melting point
The particles melt and flow out, causing a significant decrease in high-temperature strength.

Further, the prior art does not consider the composition homogeneity in the material when the third element, which is essential when used as a practical material, is added. In order to improve the brittleness or oxidation resistance of the Nb ₃ Al alloy, alloying with a third element is necessary. 1 to 2 of Cr and Ti as the third element
By adding 0 at.%, The brittleness of the Nb ₃ Al alloy is improved to some extent, but at the same time, the strength is reduced and the attractiveness as an ultrahigh temperature heat resistant material is reduced. In order to minimize the strength reduction and improve the brittleness, it is considered that addition of a high melting point transition metal such as Zr, Mo, Hf, Ta, W having a large interatomic bond energy is suitable. However, when an Nb-Al-based alloy containing such a high melting point third element is to be obtained by a usual casting method, Al having a low melting point reaches the boiling point quickly and evaporates, so that an intermetallic compound having a desired composition is formed. It is difficult to obtain a compound-based alloy, and compounds other than the intended composition are precipitated and segregated during the solidification process, so that a uniform alloy cannot be obtained. In addition, elemental element powder or Nb-
When the Al alloy powder and the high melting point third element powder are mixed and simply alloyed by thermal energy, the high melting point third element, for example, Zr, Mo, Hf, Ta, W, etc., is added to Nb-A.
In some cases, it was difficult to form a solid solution in the intermetallic compound.

The object of the present invention is to provide Nb ₃ A having excellent moldability.
It is an object of the present invention to provide a method for producing a high melting point intermetallic compound-based alloy represented by 1 2. It also has excellent high temperature strength and toughness.
It is intended to provide a method for producing a homogeneous high melting point intermetallic compound-based alloy containing a high melting point third element.

[0009]

In order to achieve the above object, in a method for producing a refractory intermetallic compound Nb ₃ Al-based alloy, Nb ₃ Al intermetallic compound powder mainly having an A15 type crystal structure is mechanically produced. The non-equilibrium supersaturated solid solution powder having a bcc type crystal structure is formed in a volume ratio of 50% or more by applying deformation, and the obtained bcc non-equilibrium supersaturated solid solution powder is
After pressure molding at a temperature of 700 ° C. or lower that transforms into an A15 type crystal structure, sintering is performed by heating at a temperature of 700 ° C. or higher, and at the same time, all of the molded products are stable A1.
A high melting point intermetallic compound N which is transformed into a 5 type crystal structure phase, a bcc phase, and a σ phase, and is finally composed mainly of the A15 phase.
b ₃ Al-based alloy is manufactured.

In order to achieve the above object, in the method for producing an intermetallic compound Nb ₃ Al based alloy, the bcc non-equilibrium supersaturated solid solution powder produced by the above method is alloyed by mechanical mixing. To produce a bcc supersaturated solid solution powder in which the additive element is uniformly distributed in solid solution,
A high melting point intermetallic compound Nb ₃ Al based alloy is produced.

Not only Nb ₃ Al-based alloys but also A1
Refractory intermetallic compound having a type 5 crystal structure Mo ₃ Al,
Ta ₃ Al, V ₃ Al, Mo ₃ Al, Nb ₃ Si, Mo ₃ S
i, Cr ₃ Si, V ₃ Si, Nb ₃ Sn, Nb ₃ Ge, and high melting point intermetallic compound MoS having a complicated crystal structure
The above method can be applied to any one of i ₂ and WSi ₂ .

[0012]

In the method for producing a refractory intermetallic compound-based alloy according to the present invention, a non-equilibrium bcc supersaturated solid solution powder is used in the molding step. The bcc solid solution has a simpler crystal structure than the A15 type structure, and has good ductility and deformability at room temperature. At the stage of molding the powder, it is necessary for each particle to deform and adhere to each other, so the higher the deformability of the particle itself, the better the moldability. The bcc solid solution can be easily molded in a molding step before sintering, and can be molded into a heat-resistant component having an arbitrary shape.

In the present invention, a Bcc supersaturated solid solution powder is obtained by mechanically deforming the A15 type compound powder using a mixer. Conventionally, bc of Nb ₃ Al-based alloy
In order to obtain a c-saturated solid solution, two methods, a rapid solidification method and a mechanical alloying method, have been considered. The method according to the present invention is superior to the rapid solidification method in that it is a solid phase process from beginning to end, so that there is almost no change in composition due to Al evaporation or mixing from a crucible. Further, the former requires two kinds of large equipments for melting and quenching, whereas in the present invention, the equipment mainly for the mixer is sufficient, which is a great economical advantage.

One of the mechanical alloying methods (Mechanic
al Alloying Method: hereinafter referred to as MA method) is an alloying treatment method in which two or more kinds of powder materials are mixed by a mixer to cause solid phase diffusion. It has been mainly used as a method for producing a non-equilibrium phase or an intermetallic compound phase with more stable energy than a simple substance state by alloying the elemental powder as a raw material. A method of alloying Nb and Al powders by the MA method to obtain a bcc supersaturated solid solution has also been reported. However, the present invention is characterized in that the most stable and lowest energy intermetallic compound powder is used as the starting material, without using the constituent element powders of Nb and Al as the starting material.
Whereas alloying from the constituent elements is an exothermic reaction, the present process for transitioning to a higher energy state is an endothermic reaction. Therefore, although the process uses the same mixer, the present invention suppresses excessive heat generation. Since increasing the oxygen concentration significantly deteriorates the mechanical properties of the material, it is necessary to reduce the oxidation as much as possible, but if the temperature is kept low during the mixing process, it is very effective in preventing oxidation. Since the present invention utilizes the endothermic reaction, there is no heat generation due to the chemical reaction, and the temperature rise can be suppressed. In addition, when trying to form a bcc solid solution from the constituent elements, bc
If the production rate of the c solid solution is not 100%, Nb phase, Al phase or other Nb-Al alloy phase which is not the A15 crystal structure phase exists in the finally sintered product. In that case, sufficient characteristics as a heat resistant component cannot be exhibited. On the contrary, in the method according to the present invention, even if the production rate of the bcc solid solution is less than 100%, the residual phase is A1.
Since there are five phases, no residual phase such as Nb or Al is observed in the final product after sintering, and excellent high temperature strength can be expected. In this case, the remaining A15 phase is 50% by volume.
If it is below, there will be no problem in molding.

The present invention is also extremely effective for alloying a refractory intermetallic compound-based alloy by adding a third element.
The additive element covers all metal elements, but especially high melting point Cr, Ti, Zr, Mo, Hf, Ta, W which does not diffuse sufficiently and is difficult to alloy by a normal powder sintering method. The present invention is suitable when the three elements are added. This is possible because the MA method forces the alloying with mechanical energy. In that case, it is important that the starting material powders for MA be the bcc supersaturated solid solution powder and the third element powder. It is b
Since the cc supersaturated solid solution has a simple crystal structure and is excellent in deformability as compared with the A15 type crystal structure, the powders are mixed with each other by MA, and the third element having a high melting point is very easily alloyed. When MA is performed using Nb, Al, and a powder of the third element as a starting material, Nb which is not the A15 crystal structure phase in the finally sintered product is similar to the above case.
Phase, Al phase, or other Nb-Al alloy phase exists, which is not suitable.

[0016]

【Example】

<Example 1> The following describes the Nb ₃ Al intermetallic compound preparation is the invention according to the flowchart of FIG.

Nb ₃ Al intermetallic compound powder mainly composed of A15 phase having a particle size of 10 μm or less is put in a container of a planetary ball mill. As the Nb ₃ Al intermetallic compound powder, one obtained by crushing an ingot obtained by plasma arc melting or the like or by a gas atomizing method is used. A hard metal or compound such as tungsten, tungsten carbide, or agate is used for the container and the balls used for mixing to prevent impurities from being mixed into the sample from the container and the balls. Increasing the oxygen concentration in the sample significantly degrades the mechanical properties of the alloy. Since the metal powder easily oxidizes in air, MA is vacuum-substituted using a glove box, and then the MA is performed in an inert gas atmosphere. It is also effective to reduce the oxygen concentration by subjecting the raw material powder to deoxidation treatment such as hydrogen reduction treatment. To prevent abnormal heating of the sample during mixing, cool the container with water or provide a ball mill with a down time. For example, after rotating the ball mill for 15 minutes, a stop time of 3 minutes is provided and this is repeated. The rotation speed and rotation time of the ball mill depend on the conditions such as the composition and weight of the sample, and it is necessary to determine the appropriate conditions each time. The rotation speed of the ball mill pot is 100 to 780 rpm, the disk is 50 to 360 rpm, and The rotation time is preferably in the range of 1 hour to 50 hours. M
The X-ray diffraction result of the powder after 10 hours of A is shown in FIG. 2, and it can be seen that most of the powder has changed to the bcc supersaturated solid solution phase. This powder is solidified and molded by CIP, and then sintered by heat treatment. Sintering temperature is bcc supersaturated solid solution is A
It is performed at a temperature at which it is transformed into a 15-type phase, that is, at 700 ° C. or higher. Alternatively, this bcc supersaturated solid solution powder is vacuum-encapsulated in a capsule and then subjected to HIP processing to be molded into a heat-resistant part. Also at this time, the HIP temperature is 700 ° C. or higher.

<Embodiment 2> The flowchart of FIG. 3 shows a method for producing an Nb ₃ Al-based alloy containing a third element according to the present invention. The bcc supersaturated solid solution powder obtained in Example 1 and a third element powder having a particle size of 10 μm, for example, Zr, M
MA is performed using powders of refractory metals such as o, Hf, Ta and W in the same manner as in Example 1 using a planetary ball mill. N
As a result of EPMA surface analysis of MA of b-23 at.% Al-9 at% Ta after 10 hours, it was found that Ta atoms were almost uniformly solid-dissolved in the Nb ₃ Al matrix in a powder state. In this way, by performing MA of the bcc supersaturated solid solution powder and the third element powder, it becomes possible to obtain an alloy in which the solid solution is uniformly formed.

Example 3 FIG. 5 shows b obtained in Example 1.
It is a DTA result of cc supersaturated solid solution powder. Temperature 700
An exothermic peak is seen from around ℃, and the exothermic peak is sharp around 850 ° C. bcc supersaturated solid solution to A1
It can be seen that the starting temperature of the transformation to the 5 phase is around 700 ° C. Therefore, in order to make the powder bcc rich in deformability, it is performed at a temperature of 700 ° C. or less at the time of molding, and sintering is A1.
It is preferable to carry out at a temperature of 700 ° C. or higher in order to transform into 5 phases.

Example 4 Refractory intermetallic compounds having A15 type crystal structure Mo ₃ Al, Ta ₃ Al, V ₃ Al,
Mo ₃ Al, Nb ₃ Si, Mo ₃ Si, Cr ₃ Si, V ₃ S
i, Nb ₃ Sn, Nb ₃ Ge, and the high-melting point intermetallic compounds MoSi ₂ and WSi ₂ having a complicated crystal structure have the same deformability and sinterability by the same method as in Examples 1 and 2. It is possible to form a high melting point intermetallic compound-based alloy product that can form an excellent bcc supersaturated solid solution, has a stable crystal structure in an arbitrary shape, and is uniformly alloyed with additional elements.

[0021]

According to the present invention, a high melting point intermetallic compound-based alloy having excellent high temperature strength and toughness, a controlled composition, a uniform shape and an arbitrary shape can be obtained. Since it is possible to manufacture high-strength heat-resistant parts that can be used even at 1200 ° C or higher, it is possible to improve and develop the performance of high-temperature related equipment using heat-resistant parts.

[Brief description of drawings]

FIG. 1 is a flowchart of a method for producing a refractory intermetallic compound Nb ₃ Al based alloy according to the present invention.

FIG. 2 is an explanatory view of an X-ray diffraction result of Nb-25 at.% Al powder manufactured by the present invention after MA treatment for 10 hours.

FIG. 3 is a flow chart of a method for producing a refractory intermetallic compound Nb ₃ Al-based alloy containing an additive element according to the present invention.

FIG. 4 shows that Nb-25 at. Explanatory drawing of the DTA analysis result of% Al powder.

Front page continued (72) Inventor Hideyo Kodama 4026 Kujimachi, Hitachi City, Hitachi, Ibaraki Prefecture

Claims (6)

[Claims] 1. A method for producing a refractory intermetallic compound Nb ₃ Al-based alloy, wherein Nb ₃ A mainly having an A15 type crystal structure is used.
l By mechanically deforming the intermetallic compound powder, a nonequilibrium supersaturated solid solution powder having a bcc type crystal structure is formed in a volume ratio of 50% or more, molded and sintered to mainly form A15.
A method for producing a refractory intermetallic compound Nb ₃ Al-based alloy, characterized in that an alloy composed of a type phase is obtained. 2. The method according to claim 1, wherein the bcc non-equilibrium supersaturated solid solution powder is pressure-molded at a temperature of 700 ° C. or lower at which it transforms into an A15 type crystal structure, and then sintered and molded by heating at a temperature of 700 ° C. or higher. At the same time, a method for producing a refractory intermetallic compound Nb ₃ Al-based alloy in which all of the formed bodies are transformed into stable A15 type crystal structure phase, bcc phase, and σ phase. 3. The method according to claim 1, wherein the prepared bcc non-equilibrium supersaturated solid solution powder and the additive element powder are alloyed by mechanical mixing, and the additive element is uniformly dissolved in the bcc supersaturated solid solution powder. A method for producing a refractory intermetallic compound Nb ₃ Al-based alloy before the step. 4. The Nb-Al alloy powder according to claim 1, and the bcc non-equilibrium supersaturated solid solution powder prepared are mixed so that the volume ratio of the latter is 50% or more, and the mixture is molded and sintered. A method for producing a high melting point intermetallic compound Nb ₃ Al based alloy. 5. A refractory intermetallic compound having an A15 type crystal structure, Mo ₃ Al, Ta ₃ Al, V ₃ Al, Mo ₃ Al, N.
b ₃ Si, Mo ₃ Si, Cr ₃ Si, V ₃ Si, Nb ₃ S
n, Nb ₃ Ge, or a high melting point intermetallic compound MoSi ₂ or WSi ₂ having a complicated crystal structure is mechanically deformed to give a b content of 50% or more by volume.
cc A non-equilibrium supersaturated metal that forms a non-equilibrium supersaturated solid solution, press-molds at a temperature below the temperature at which it transforms from a bcc structure into a stable crystal structure, and then holds the temperature above the transformation temperature to transform it into a stable crystal structure simultaneously with sintering. Method for producing intermetallic compound base alloy. 6. A process according to claim 5, wherein a step of alloying the prepared bcc non-equilibrium supersaturated solid solution powder and the additive element powder by mechanical mixing to uniformly form a solid solution in the bcc supersaturated solid solution powder before the molding step. A method for producing a high-melting point intermetallic compound according to claim 1.