WO2020235200A1

WO2020235200A1 - Tial alloy and production method therefor

Info

Publication number: WO2020235200A1
Application number: PCT/JP2020/011935
Authority: WO
Inventors: 圭司久布白
Original assignee: 株式会社Ihi
Priority date: 2019-05-23
Filing date: 2020-03-18
Publication date: 2020-11-26
Also published as: EP3974551A4; JP7226535B2; EP3974551B1; US20220017995A1; JPWO2020235200A1; EP3974551A1

Abstract

Provided is a TiAl alloy which contains 48 at% to 50 at% Al, 1 at% to 3 at% Nb, 0.3 at% to 1 at% Zr, and 0.05 at% to 0.3 at% B, with the remainder comprising Ti and unavoidable impurities.

Description

TiAl alloy and its manufacturing method

This disclosure relates to a TiAl alloy and a method for producing the same.

TiAl (titanium aluminide) alloy is an alloy formed of an intermetallic compound of Ti and Al. TiAl alloys have excellent heat resistance, are lighter in weight and have higher specific strength than Ni-based alloys, and are therefore applied to aircraft engine parts such as turbine blades. As such a TiAl alloy, a TiAl alloy containing Cr and Nb is used (see Patent Document 1).

Japanese Unexamined Patent Publication No. 2013-209750

By the way, in order to reduce the weight of TiAl alloy parts such as turbine blades, it is necessary to increase the strength of the TiAl alloy to increase the specific strength. However, with conventional TiAl alloys, it is difficult to improve the mechanical strength and ductility in a well-balanced manner to increase the strength, and increasing the ductility may reduce the mechanical strength.

Therefore, an object of the present disclosure is to provide a TiAl alloy and a method for producing the same, which can improve the mechanical strength and ductility of the TiAl alloy in a well-balanced manner.

The TiAl alloy according to the present disclosure includes Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, Zr of 0.3 atomic% or more and 1 atomic% or less, and 0.05 atom. It contains B of% or more and 0.3 atomic% or less, and the balance is composed of Ti and unavoidable impurities.

In the TiAl alloy according to the present disclosure, the Al content may be 49 atomic% or more and 50 atomic% or less.

In the TiAl alloy according to the present disclosure, the metal structure is composed of lamella grains and γ grains, and it is preferable that there is no segregation of Zr.

In the TiAl alloy according to the present disclosure, the volume fraction of the lamella grains may be 50% by volume or more when the total volume fraction of the lamella grains and the γ grains is 100% by volume.

In the TiAl alloy according to the present disclosure, the room temperature tensile breaking strength may be 400 MPa or more and the room temperature tensile breaking strain may be 1.0% or more.

In the TiAl alloy according to the present disclosure, the creep strain after 200 hours may be 2% or less at 800 ° C. and a load stress of 150 MPa.

The method for producing a TiAl alloy according to the present disclosure includes Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, Zr of 0.3 atomic% or more and 1 atomic% or less, and 0. The present invention comprises a casting step of casting a TiAl alloy raw material containing .05 atomic% or more and 0.3 atomic% or less B, and the balance being Ti and unavoidable impurities.

The method for producing a TiAl alloy according to the present disclosure is to hot-isotropically pressurize the cast TiAl alloy at 1250 ° C. or higher and 1350 ° C. or lower, 1 hour or longer and 5 hours or lower, 158 MPa or higher and 186 MPa or lower. It may be provided with a hot isotropic pressurizing process in which the alloy is later cooled to 900 ° C. and rapidly cooled to 900 ° C. or lower to perform hot isotropic pressurization.

The method for producing a TiAl alloy according to the present disclosure includes a stress removing step of holding the TiAl alloy subjected to hot isotropic pressure treatment at 800 ° C. or higher and 950 ° C. or lower for 1 hour or longer and 5 hours or shorter to relieve stress. May be good.

According to the TiAl alloy having the above configuration and the manufacturing method thereof, it is possible to improve the mechanical strength and ductility of the TiAl alloy in a well-balanced manner.

It is a figure which shows the structure of the turbine blade in the embodiment of this disclosure. In the embodiment of the present disclosure, it is a graph which shows the tensile test result. In the embodiment of the present disclosure, it is a graph which shows the tensile test result. It is a photograph which shows the metal structure observation result in embodiment of this disclosure. In the embodiment of the present disclosure, it is a graph which shows the tensile test result. In the embodiment of the present disclosure, it is a graph which shows the creep test result. In the embodiment of the present disclosure, it is a photograph showing the cross-sectional observation result after the oxidation test. It is a graph which shows the differential thermal analysis result in the embodiment of this disclosure.

The embodiments of the present disclosure will be described in detail below with reference to the drawings. The TiAl (titanium aluminide) alloy according to the embodiment of the present disclosure includes Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, and 0.3 atomic% or more and 1 atomic% or less. It contains Zr and B of 0.05 atomic% or more and 0.3 atomic% or less, and the balance is composed of Ti and unavoidable impurities. Next, the reason for limiting the composition range of each alloy component constituting the TiAl alloy will be described.

Al (aluminum) has a function of improving mechanical strength and ductility such as room temperature ductility. The Al content is 48 atomic% or more and 50 atomic% or less. When the Al content is less than 48 atomic%, the ductility decreases. If the Al content is greater than 50 atomic%, the ductility is reduced. The Al content may be 49 atomic% or more and 50 atomic% or less, and the Al content may be 49 atomic%. Thereby, the mechanical strength and ductility can be further improved.

Nb (niobium) has a function of improving oxidation resistance and mechanical strength. The content of Nb is 1 atomic% or more and 3 atomic% or less. When the Nb content is less than 1 atomic%, the oxidation resistance and the high temperature strength are lowered. When the Nb content is greater than 3 atomic%, ductility such as room temperature ductility decreases.

Zr (zirconium) has a function of improving oxidation resistance and mechanical strength. The Zr content is 0.3 atomic% or more and 1 atomic% or less. When the Zr content is less than 0.3 atomic%, the ductility such as oxidation resistance and room temperature ductility, and the mechanical strength such as high temperature strength are lowered. Further, when the Zr content is less than 0.3 atomic%, the castability is lowered. If the Zr content is greater than 1 atomic%, segregation may occur. When Zr segregation occurs, mechanical strength and ductility may decrease. The Zr content may be 0.3 atomic% or more and 0.5 atomic% or less.

B (boron) has a function of increasing ductility such as room temperature ductility by refining crystal grains. The content of B is 0.05 atomic% or more and 0.3 atomic% or less. When the content of B is smaller than 0.05 atomic%, the crystal grains become coarse and the ductility decreases. If the B content is greater than 0.3 atomic%, the impact characteristics may deteriorate. By setting the content of B to 0.05 atomic% or more and 0.3 atomic% or less, the ductility can be improved because it is composed of fine crystal grains having a crystal grain size of 200 μm or less.

B has a function of precipitating fine boride in crystal grains by hot isotropic pressure treatment, which will be described later, to improve mechanical strength. The fine boride is formed including those having a particle size of 0.1 μm or less. The fine boride is composed of TiB, TiB ₂ , and the like. By precipitating fine boride in the crystal grains, it is possible to improve mechanical strength such as tensile strength, fatigue strength, and creep strength.

The rest of the TiAl alloy is composed of Ti and unavoidable impurities. Inevitable impurities are impurities that can be mixed in without intentional addition. Since the TiAl alloy does not contain Cr (chromium), it is possible to suppress a decrease in mechanical strength. Since the TiAl alloy does not contain V (vanadium), it is possible to suppress a decrease in mechanical strength and a decrease in oxidation resistance. Since the TiAl alloy does not contain Mo (molybdenum), a decrease in specific strength can be suppressed.

Next, a method for producing a TiAl alloy according to the embodiment of the present disclosure will be described.

The method for producing a TiAl alloy is as follows: Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, Zr of 0.3 atomic% or more and 1 atomic% or less, and 0.05 atomic%. The present invention comprises a casting step of melting and casting a TiAl alloy raw material containing B of 0.3 atomic% or less and the balance of Ti and unavoidable impurities. This TiAl alloy raw material is melted and cast in a vacuum induction furnace or the like to form an ingot (ingot) or the like. For casting the TiAl alloy raw material, a casting apparatus used for casting a general metal material can be used.

Since this TiAl alloy has a lower solidification temperature than the conventional TiAl alloy, it is possible to improve the hot water circulation during casting. This TiAl alloy can have a solid-liquid coexistence temperature range of 1440 ° C. to 1510 ° C. as measured by differential thermal analysis (DTA). As a result, TiAl alloy parts such as turbine blades can be formed with a net shape or a near net shape, so that the manufacturing cost can be reduced. Further, according to this TiAl alloy, it is not necessary to take super heat, so that castability is improved.

The TiAl alloy is produced by hot isotropic pressurization (HIP) of the cast TiAl alloy at 1250 ° C. or higher and 1350 ° C. or lower, 1 hour or higher and 5 hours or lower, 158 MPa or higher and 186 MPa or lower, and after hot isotropic pressurization. It may be provided with a hot isotropic pressurizing process in which the alloy is cooled to 900 ° C. and rapidly cooled to 900 ° C. or lower to perform hot isotropic pressurization. By the hot isotropic pressure treatment, casting defects such as voids can be suppressed and the metal structure can be controlled.

More specifically, the cast TiAl alloy is hot and isotropically pressurized at 1250 ° C. or higher and 1350 ° C. or lower, 1 hour or higher and 5 hours or lower, 158 MPa or higher and 186 MPa or lower, so that the voids mainly contained in the cast TiAl alloy are contained. Casting defects such as internal defects such as, etc. can be suppressed. Further, the metal structure can be mainly controlled by releasing the pressure after hot isotropic pressurization, cooling the furnace to 900 ° C., and quenching at 900 ° C. or lower. It should be noted that rapid cooling from 900 ° C. is preferably performed at a cooling rate higher than that of air cooling, and can be performed by gas fan cooling or the like.

The method for producing a TiAl alloy may include a stress removing step of holding the TiAl alloy subjected to hot isotropic pressure treatment at 800 ° C. or higher and 950 ° C. or lower for 1 hour or more and 5 hours or less to remove stress. Residual stress and the like can be removed by heat-treating the TiAl alloy subjected to the hot isotropic pressure treatment to remove the stress. Thereby, the ductility of the TiAl alloy can be further improved.

The hot isotropic pressurization treatment and stress relief should be performed in a vacuum atmosphere or in an inert gas atmosphere such as argon gas to prevent oxidation. For hot isotropic pressurization, a HIP device or the like used for hot isotropic pressurization of a general metal material can be used. For stress relief, an atmosphere furnace or the like used for stress relief annealing of general metal materials can be used.

Next, the metal structure of the TiAl alloy will be described. The metal structure of the TiAl alloy is composed of fine crystal grains having a crystal grain size of 200 μm or less. Thereby, the ductility of the TiAl alloy can be improved. Further, the metal structure of the TiAl alloy is composed of lamella grains and γ grains, and there is no segregation of Zr. The lamella grains are formed by regularly arranging α ₂ phases made of Ti ₃ Al and γ phases made of Ti Al in a layered manner. The γ grains are made of TiAl. Boride having a particle size of 0.1 μm or less is contained in the γ grains. The boride is made of TiB, TiB _2, etc. in a needle shape or the like.

The lamella grains can improve mechanical strength such as tensile strength, fatigue strength, and creep strength. The γ grains can improve ductility and high temperature strength. A fine boride having a particle size of 0.1 μm or less can improve the mechanical strength. The metal structure of the TiAl alloy is preferably such that the volume fraction of the lamella grains is 50% by volume or more and the balance is γ grains, where the total volume fraction of the lamella grains and the γ grains is 100% by volume. Since the metal structure of the TiAl alloy is mainly composed of lamella grains, the mechanical strength can be improved. Further, since the metal structure of the TiAl alloy does not segregate Zr, it is possible to suppress a decrease in mechanical strength and ductility.

Next, the mechanical properties of the TiAl alloy according to the embodiment of the present disclosure will be described. The mechanical properties of TiAl alloys at room temperature can be such that the room temperature tensile breaking strength is 400 MPa or more and the room temperature tensile breaking strain is 1.0% or more when a tensile test is performed in accordance with JIS, ASTM, etc. .. As for the high temperature creep characteristics of TiAl alloy, when a creep test is performed in accordance with JIS, ASTM, etc., the creep strain after 200 hours can be reduced to 2% or less at 800 ° C. and a load stress of 150 MPa. Further, the high temperature creep characteristic of the TiAl alloy can reduce the creep strain after 400 hours to 5% or less at 800 ° C. and a load stress of 150 MPa. Further, the high temperature creep characteristic of the TiAl alloy can reduce the creep strain after 600 hours to 15% or less at 800 ° C. and a load stress of 150 MPa.

The TiAl alloy according to the embodiment of the present disclosure can be applied to turbine blades and the like of aircraft engine parts. FIG. 1 is a diagram showing a configuration of turbine blades 10. Since this TiAl alloy has high mechanical strength such as high temperature strength, the heat resistance of the turbine blade 10 can be improved. Further, since this TiAl alloy is excellent in ductility such as room temperature ductility, damage to the turbine blade 10 can be suppressed even when the turbine blade 10 is assembled or assembled.

As described above, the TiAl alloy having the above constitution includes Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, Zr of 0.3 atomic% or more and 1 atomic% or less, and 0.05. It contains B of atomic% or more and 0.3 atomic% or less, and the balance is composed of Ti and unavoidable impurities. As a result, the mechanical strength and ductility of the TiAl alloy can be improved in a well-balanced manner.

The method for producing a TiAl alloy having the above constitution is as follows: Al of 48 atomic% or more and 50 atomic% or less, Nb of 1 atomic% or more and 3 atomic% or less, Zr of 0.3 atomic% or more and 1 atomic% or less, and 0. The present invention comprises a casting step of casting a TiAl alloy raw material containing B of 05 atomic% or more and 0.3 atomic% or less, and the balance of which is Ti and unavoidable impurities. As a result, it is possible to manufacture a TiAl alloy having improved mechanical strength and ductility in a well-balanced manner, and it is possible to improve castability because the hot water circulation property is good.

First, the TiAl alloys of Examples 1 to 2, Reference Examples 1 to 8, and Comparative Example 1 will be described. The alloy composition of each TiAl alloy is shown in Table 1.

The TiAl alloy of Example 1 contains 49.5 atomic% Al, 2 atomic% Nb, 0.5 atomic% Zr, and 0.2 atomic% B, and the balance is inevitably Ti. As an impurity. The TiAl alloy of Example 2 contains 49.5 atomic% Al, 2 atomic% Nb, 1 atomic% Zr, and 0.2 atomic% B, and the balance is Ti and unavoidable impurities. And said. The TiAl alloy of Reference Example 1 contained 48 atomic% Al, 1 atomic% Nb, 3 atomic% Zr, and 0.1 atomic% B, and the balance was Ti and unavoidable impurities. .. The TiAl alloy of Reference Example 2 contained 49 atomic% Al, 1 atomic% Nb, 3 atomic% Zr, and 0.1 atomic% B, and the balance was Ti and unavoidable impurities. ..

The TiAl alloy of Reference Example 3 contained 48 atomic% Al and 0.1 atomic% B, and the balance was Ti and unavoidable impurities. The TiAl alloy of Reference Example 4 contained 49 atomic% Al and 0.1 atomic% B, and the balance was Ti and unavoidable impurities. The TiAl alloy of Reference Example 5 contained 50 atomic% Al and 0.1 atomic% B, and the balance was Ti and unavoidable impurities. The TiAl alloy of Reference Example 6 contained 49.5 atomic% Al and 0.2 atomic% B, and the balance was Ti and unavoidable impurities.

The TiAl alloy of Reference Example 7 contains 49.5 atomic% Al, 4 atomic% Nb, 0.2 atomic% Zr, and 0.2 atomic% B, and the balance is inevitably Ti. As an impurity. The TiAl alloy of Reference Example 8 contains 49.5 atomic% Al, 4 atomic% Nb, 0.5 atomic% Zr, and 0.2 atomic% B, and the balance is inevitably Ti. As an impurity. The TiAl alloy of Comparative Example 1 contained 48 atomic% Al, 2 atomic% Nb, and 2 atomic% Cr, and the balance was Ti and unavoidable impurities.

Each TiAl alloy raw material having an alloy composition shown in Table 1 was melted and cast in a high-frequency vacuum melting furnace to form a TiAl alloy ingot having each alloy composition. Each TiAl alloy was subjected to hot isotropic pressure treatment after casting. In the hot isotropic pressurization treatment, the cast TiAl alloy is hot isotropically pressurized at 1300 ± 14 ° C. for 3 ± 0.1 hours at 172 ± 14 MPa, and then cooled to 900 ° C. after hot isotropic pressurization. Then, it was rapidly cooled by gas fan cooling at 900 ° C. or lower for processing.

The effect of Al on the TiAl alloy was evaluated. Tensile tests were performed on the TiAl alloys of Reference Examples 3 to 5 at room temperature. The tensile test was performed in accordance with ASTM E8. FIG. 2 is a graph showing the results of the tensile test. In the graph of FIG. 2, the horizontal axis represents the Al content, the vertical axis represents the strain, and Reference Examples 3 to 5 are represented by white circles. The strain indicates a breaking strain. From the graph of FIG. 2, it was found that the room temperature ductility decreases when the Al content is smaller than 48 atomic% or when the Al content is larger than 50 atomic%. In addition, Reference Examples 4 and 5 had a larger distortion than Reference Example 3. From this, it was found that the room temperature ductility becomes higher when the Al content is 49 atomic% or more and 50 atomic% or less. Reference Example 4 has a larger distortion than Reference Examples 3 and 5. From this, it was found that when the Al content was 49 atomic%, the room temperature ductility was further increased.

The effects of Nb and Zr on the TiAl alloy were evaluated. Tensile tests were performed on the TiAl alloys of Examples 1 and 2 and Reference Examples 6 to 8 at room temperature. The tensile test was performed in accordance with ASTM E8. FIG. 3 is a graph showing the results of the tensile test. In the graph of FIG. 3, the horizontal axis is the Zr content, the vertical axis is the 0.2% proof stress, Reference Example 6 is a black circle, Examples 1 and 2 are black squares, and Reference Examples 7 and 8 are white rhombuses. It is shown by. Examples 1 to 2 and Reference Examples 7 to 8 had a 0.2% higher yield strength than Reference Example 6. From this, it was found that the mechanical strength was increased by adding Nb and Zr. Further, in Reference Example 8, the room temperature ductility was lower than that in Example 1. From this, it was found that when the Nb content is larger than 3 atomic%, the ductility such as room temperature ductility of the TiAl alloy decreases.

The metallographic structure of the TiAl alloy was evaluated. The metallographic structure of the TiAl alloys of Examples 1 and 2 and Reference Examples 1 and 2 was observed. The metallographic structure was observed with an optical microscope or a scanning electron microscope. 4A and 4B are photographs showing the results of observing the metallographic structure, FIG. 4A is a photograph of Example 1, FIG. 4B is a photograph of Example 2, and FIG. 4C is a photograph of Example 2. , It is a photograph of Reference Example 1, and FIG. 4D is a photograph of Reference Example 2.

As shown in FIGS. 4 (a) and 4 (b), the metallographic structures of Examples 1 and 2 were composed of fine crystal grains having a crystal grain size of 200 μm or less. The metallographic structure of Examples 1 and 2 was composed of lamella grains and γ grains, and contained boride having a particle size of 0.1 μm or less in the γ grains. In the metal structures of Examples 1 and 2, when the total volume fraction of the lamella grains and the γ grains is 100% by volume, the volume fraction of the lamella grains is 50% by volume or more, and the balance is composed of γ grains. It was. Regarding the volume fraction of each grain, the area fraction of each grain was calculated by image processing from the contrast information of each grain in the metallographic photograph, and this was used as the volume fraction of each grain.

Further, as shown in FIGS. 4 (a) and 4 (b), no segregation of Zr was observed in the metal structures of Examples 1 and 2. On the other hand, as shown in FIGS. 4 (c) and 4 (d), segregation of Zr was observed in the metallographic structures of Reference Examples 1 and 2 as shown by the white arrows. From this result, it was found that when the Zr content was larger than 1 atomic%, Zr segregated. Therefore, it was clarified that the Zr content should be 1 atomic% or less.

The room temperature mechanical properties of the TiAl alloy were evaluated. The TiAl alloys of Example 1 and Comparative Example 1 were subjected to a tensile test at room temperature. The tensile test was performed in accordance with ASTM E8. FIG. 5 is a graph showing the results of the tensile test. In FIG. 5, strain is taken on the horizontal axis and stress is taken on the vertical axis, and the stress-strain curve of each TiAl alloy is shown. Example 1 had a higher room temperature intensity than Comparative Example 1. In addition, Example 1 had a higher room temperature ductility than Comparative Example 1. More specifically, the room temperature tensile breaking strength of Example 1 was 400 MPa or more, and the room temperature tensile breaking strain was 1.0% or more.

The high temperature mechanical properties of TiAl alloy were evaluated. The TiAl alloys of Example 1 and Comparative Example 1 were subjected to a creep test at a high temperature. The creep test was performed in accordance with ASTM E139. The creep test conditions were a test temperature of 800 ° C. and a load stress of 150 MPa. FIG. 6 is a graph showing the results of the creep test. In FIG. 6, the creep time is taken on the horizontal axis and the creep strain is taken on the vertical axis, and the creep curve of each TiAl alloy is shown. In Example 1, a high temperature creep characteristic of 5 times or more was obtained as compared with Comparative Example 1. Example 1 has improved high temperature creep characteristics as compared with Comparative Example 1. More specifically, in the high temperature creep characteristics of Example 1, when the test temperature was 800 ° C. and the load stress was 150 MPa, the creep strain after 200 hours had passed was 2% or less. Further, as for the high temperature creep characteristics of Example 1, when the test temperature was 800 ° C. and the load stress was 150 MPa, the creep strain after 400 hours was 5% or less. Further, as for the high temperature creep characteristics of Example 1, when the test temperature was 800 ° C. and the load stress was 150 MPa, the creep strain after 600 hours had passed was 15% or less.

As shown in FIGS. 5 and 6, it was clarified that the TiAl alloy of Example 1 was excellent in mechanical strength and ductility, and the mechanical strength and ductility were improved in a well-balanced manner. On the other hand, the TiAl alloy of Comparative Example 1 had lower room temperature mechanical properties and high temperature mechanical properties than the TiAl alloy of Example 1. The reason for this is considered to be the influence of Cr contained in the TiAl alloy of Comparative Example 1.

The oxidation resistance of the TiAl alloy was evaluated. Oxidation tests were carried out on the TiAl alloys of Example 1 and Comparative Example 1. The oxidation test was carried out by continuous oxidation at 750 ° C. for 200 hours in the atmosphere. After the oxidation test, a cross section was observed to evaluate the thickness of the oxide film. FIG. 7 is a photograph showing a cross-sectional observation result after the oxidation test, FIG. 7 (a) is a photograph of Example 1, and FIG. 7 (b) is a photograph of Comparative Example 1. The thickness of the oxide film of Example 1 was 2.1 μm. The thickness of the oxide film of Comparative Example 1 was 4.3 μm. From this result, it was found that Example 1 was superior in oxidation resistance to Comparative Example 1.

The castability of TiAl alloy was evaluated. The solid-liquid coexistence temperature range was evaluated for the TiAl alloys of Example 1 and Comparative Example 1. The evaluation of the solid-liquid coexistence temperature range was performed by differential thermal analysis (DTA). FIG. 8 is a graph showing the results of differential thermal analysis. In FIG. 8, each TiAl alloy is taken on the horizontal axis, the temperature is taken on the vertical axis, and the solid-liquid coexistence temperature range of each TiAl alloy is indicated by a quadrangle. From the graph shown in FIG. 8, it was found that Example 1 had a lower solidification temperature than Comparative Example 1. More specifically, in Example 1, the solid-liquid coexistence temperature range was 1440 ° C to 1510 ° C as measured by differential thermal analysis (DTA). As a result, it was clarified that in Example 1, since the casting temperature can be set lower than that in Comparative Example 1, mold reaction defects can be suppressed.

Since the present disclosure can improve the mechanical strength and ductility of TiAl alloy in a well-balanced manner, it can be applied to turbine blades and the like of aircraft engine parts.

Claims

It is a TiAl alloy
Al of 48 atomic% or more and 50 atomic% or less,
Nb of 1 atomic% or more and 3 atomic% or less,
Zr of 0.3 atomic% or more and 1 atomic% or less,
A TiAl alloy containing B of 0.05 atomic% or more and 0.3 atomic% or less, and the balance of which is Ti and unavoidable impurities.
The TiAl alloy according to claim 1.
A TiAl alloy having an Al content of 49 atomic% or more and 50 atomic% or less.
The TiAl alloy according to claim 1 or 2.
The metallographic structure is a TiAl alloy that is composed of lamella grains and γ grains and has no Zr segregation.
The TiAl alloy according to claim 3, wherein the TiAl alloy is used.
The metal structure is a TiAl alloy having a volume fraction of lamella grains of 50% by volume or more, where the total volume fraction of lamella grains and γ grains is 100% by volume.
The TiAl alloy according to any one of claims 1 to 4.
A TiAl alloy having a room temperature tensile breaking strength of 400 MPa or more and a room temperature tensile breaking strain of 1.0% or more.
The TiAl alloy according to any one of claims 1 to 5.
A TiAl alloy having a creep strain of 2% or less after 200 hours at 800 ° C. and a load stress of 150 MPa.
It is a manufacturing method of TiAl alloy.
Al of 48 atomic% or more and 50 atomic% or less,
Nb of 1 atomic% or more and 3 atomic% or less,
Zr of 0.3 atomic% or more and 1 atomic% or less,
A method for producing a TiAl alloy, comprising a casting step of casting a TiAl alloy raw material containing 0.05 atomic% or more and 0.3 atomic% or less of B, and the balance being Ti and unavoidable impurities.
The method for producing a TiAl alloy according to claim 7.
The cast TiAl alloy is hot isotropically pressurized at 1250 ° C. or higher and 1350 ° C. or lower, 1 hour or longer and 5 hours or lower, 158 MPa or higher and 186 MPa or lower, and after hot isotropic pressurization, the furnace is cooled to 900 ° C. A method for producing a TiAl alloy, which comprises a hot isotropic pressure treatment step of quenching and hot isotropic pressure treatment.
The method for producing a TiAl alloy according to claim 8.
A method for producing a TiAl alloy, comprising a stress removing step of holding the hot isotropic pressure-treated TiAl alloy at 800 ° C. or higher and 950 ° C. or lower for 1 hour or more and 5 hours or less to remove stress.