US20220010410A1 - TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME - Google Patents
TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME Download PDFInfo
- Publication number
- US20220010410A1 US20220010410A1 US17/449,132 US202117449132A US2022010410A1 US 20220010410 A1 US20220010410 A1 US 20220010410A1 US 202117449132 A US202117449132 A US 202117449132A US 2022010410 A1 US2022010410 A1 US 2022010410A1
- Authority
- US
- United States
- Prior art keywords
- tial alloy
- less
- tial
- isostatic pressing
- hot isostatic
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
- 229910045601 alloy Inorganic materials 0.000 title claims abstract description 173
- 239000000956 alloy Substances 0.000 title claims abstract description 173
- 229910010038 TiAl Inorganic materials 0.000 title claims abstract description 168
- 238000004519 manufacturing process Methods 0.000 title claims description 18
- 239000012535 impurity Substances 0.000 claims abstract description 18
- 229910052751 metal Inorganic materials 0.000 claims description 43
- 239000002184 metal Substances 0.000 claims description 43
- 238000001513 hot isostatic pressing Methods 0.000 claims description 39
- 238000000034 method Methods 0.000 claims description 33
- 238000007711 solidification Methods 0.000 claims description 24
- 230000008023 solidification Effects 0.000 claims description 24
- 238000005266 casting Methods 0.000 claims description 16
- 238000001816 cooling Methods 0.000 claims description 12
- 239000002994 raw material Substances 0.000 claims description 7
- 238000005204 segregation Methods 0.000 claims description 7
- 239000010955 niobium Substances 0.000 description 29
- 230000000052 comparative effect Effects 0.000 description 16
- 239000013078 crystal Substances 0.000 description 14
- 238000007254 oxidation reaction Methods 0.000 description 14
- 230000003647 oxidation Effects 0.000 description 13
- 239000010936 titanium Substances 0.000 description 13
- 238000009864 tensile test Methods 0.000 description 9
- 230000015556 catabolic process Effects 0.000 description 5
- 239000011651 chromium Substances 0.000 description 5
- 238000006731 degradation reaction Methods 0.000 description 5
- 239000000203 mixture Substances 0.000 description 5
- 239000007789 gas Substances 0.000 description 4
- 238000005259 measurement Methods 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 239000007769 metal material Substances 0.000 description 3
- 229910052758 niobium Inorganic materials 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- QYEXBYZXHDUPRC-UHFFFAOYSA-N B#[Ti]#B Chemical compound B#[Ti]#B QYEXBYZXHDUPRC-UHFFFAOYSA-N 0.000 description 2
- 229910033181 TiB2 Inorganic materials 0.000 description 2
- OQPDWFJSZHWILH-UHFFFAOYSA-N [Al].[Al].[Al].[Ti] Chemical compound [Al].[Al].[Al].[Ti] OQPDWFJSZHWILH-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 229910052796 boron Inorganic materials 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 230000001965 increasing effect Effects 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
- 230000008018 melting Effects 0.000 description 2
- 229910021324 titanium aluminide Inorganic materials 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 229910021330 Ti3Al Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000010432 diamond Substances 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000002708 enhancing effect Effects 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910000765 intermetallic Inorganic materials 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000002265 prevention Effects 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000001629 suppression Effects 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C14/00—Alloys based on titanium
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
- B21J5/00—Methods for forging, hammering, or pressing; Special equipment or accessories therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/12—Both compacting and sintering
- B22F3/14—Both compacting and sintering simultaneously
- B22F3/15—Hot isostatic pressing
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/16—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of other metals or alloys based thereon
- C22F1/18—High-melting or refractory metals or alloys based thereon
- C22F1/183—High-melting or refractory metals or alloys based thereon of titanium or alloys based thereon
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F2301/00—Metallic composition of the powder or its coating
- B22F2301/20—Refractory metals
- B22F2301/205—Titanium, zirconium or hafnium
Definitions
- the present disclosure relates to a TiAl alloy and a method of manufacturing the same.
- a TiAl (titanium aluminide) alloy is an alloy formed of an intermetallic compound of Ti and Al.
- the TiAl alloy is excellent in the heat resistance, and has a lighter weight and larger specific strength than an Ni-base alloy, and thus, is applied to aircraft engine components such as turbine blades.
- a TiAl alloy containing Cr and Nb is used for such the TiAl alloy. See Japanese Patent Application Publication No. 2013-209750 (Patent Literature 1).
- an object of the present disclosure is to provide a TiAl alloy capable of improving the mechanical strength and the ductility of the TiAl alloy in a good balance, and a method of manufacturing the same.
- a TiAl alloy according to the present disclosure contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- the content of Al may be 49 at %.
- a metal structure may be formed of lamellar grains and ⁇ grains, and may be free of the segregation of Nb.
- a volume fraction of the lamellar grains may be 80 volume % or more, relative to a total of the volume fraction of the lamellar grain and the volume fraction of the ⁇ grain being 100 volume %.
- Vickers hardness at a room temperature may be 200 HV or more.
- room temperature ultimate tensile strength may be 400 MPa or more and room temperature tensile fracture strain may be 1.0° or more.
- creep strain after the elapse of 200 hours may be 2% or less, when a temperature is 800° C. and applied stress is 150 MPa.
- a method of manufacturing a TiAl alloy according to the present disclosure includes a casting step of casting a TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- a solidification process may pass through an a single phase region.
- the method of manufacturing the TiAl alloy according to the present disclosure may include a hot isostatic pressing process step for performing a hot isostatic pressing process of applying hot isostatic pressing to the cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, at an applied stress range from 158 MPa or higher to 186 MPa or lower, and then furnace cooling the cast TiAl alloy subjected to the hot isostatic pressing to 900° C., followed by rapid cooling of the cast TiAl alloy subjected to the hot isostatic pressing from 900° C.
- the method of manufacturing the TiAl alloy according to the present disclosure may include a stress relieving step of relieving stress by holding the TiAl alloy subjected to the hot isostatic pressing process at a temperature range from 800° C. or higher to 950° C. or lower for a hour range from 1 hour or more to 5 hours or less.
- the mechanical strength and the ductility of the TiAl alloy can be improved in a good balance.
- FIG. 1 shows a constitution of a turbine blade in an embodiment of the present disclosure.
- FIG. 2 is a graph showing results of tensile tests in an embodiment of the present disclosure.
- FIG. 3A is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 4 in an embodiment of the present disclosure.
- FIG. 3B is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 5 in an embodiment of the present disclosure.
- FIG. 3C is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 6 in an embodiment of the present disclosure.
- FIG. 3D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 7 in an embodiment of the present disclosure.
- FIG. 3E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 8 in an embodiment of the present disclosure.
- FIG. 4A is a photograph showing result of the observation of metal structure of TiAl alloy of Example 2 in an embodiment of the present disclosure.
- FIG. 4B is a photograph showing result of the observation of metal structure of TiAl alloy of Example 3 in an embodiment of the present disclosure.
- FIG. 4C is a photograph showing result of the observation of metal structure of TiAl alloy of Example 4 in an embodiment of the present disclosure.
- FIG. 4D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 9 in an embodiment of the present disclosure.
- FIG. 4E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 10 in an embodiment of the present disclosure.
- FIG. 5 is a graph showing results of the measurement of Vickers hardness of TiAl alloys before being subjected to hot isostatic pressing process, in an embodiment of the present disclosure.
- FIG. 6 is a graph showing results of the measurement of Vickers hardness of TiAl alloys subjected to hot isostatic pressing process, in an embodiment of the present disclosure.
- FIG. 7 is a graph showing results of tensile tests in an embodiment of the present disclosure.
- FIG. 8 is a graph showing results of creep tests, in an embodiment of the present disclosure.
- FIG. 9A is a photograph showing result of the observation of cross-sectional area of Example 1 after performing oxidation test, in an embodiment of the present disclosure.
- FIG. 9B is a photograph showing result of the observation of cross-sectional area of Comparative Example 1 after performing oxidation test, in an embodiment of the present disclosure.
- a TiAl (titanium aluminide) alloy according to an embodiment of the present disclosure contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- a composition range of each alloy component contained in the TiAl alloy is limited will be explained.
- Al (aluminium) has a function of improving the mechanical strength and the ductility such as the room temperature ductility.
- the content of Al is in a range from 48 at % or more to 50 at % or less.
- the ductility degrades if the content of Al is less than 48 at %.
- the ductility degrades if the content of Al is more than 50 at %.
- a solidification process changes from an a single phase region (a solidification) to a ⁇ single phase region ( ⁇ solidification), and thus, a columnar crystal is formed, and there is a possibility that the anisotropy occurs.
- the solidification process can be in the ⁇ single phase region (a solidification), and this can suppresses the anisotropy. Further, the mechanical strength and the ductility can be further improved by setting the content of Al to 49 at %.
- Nb (niobium) has a function of improving the oxidation resistance and the mechanical strength.
- the content of Nb is in a range from 3 at % or more to 5 at % or less. If the content of Nb is less than 3 at %, the oxidation resistance and the high-temperature strength degrade. If the content of Nb is more than 5 at %, the ductility such as the room temperature ductility degrades. Further, if the content of Nb is 5 at % or less, the segregation of Nb can be suppressed. The occurrence of the segregation of Nb may degrade the mechanical strength and the ductility.
- B (boron) has a function of enhancing the ductility such as the room temperature ductility by refining crystal grains.
- the content of B is in a range from 0.1 at % or more to 0.3 at % or less. If the content of B is less than 0.1 at %, the crystal grains are coarsened and the ductility degrades. If the content of B is more than 0.3 at %, impact characteristics may be degraded.
- the TiAl alloy comes to be formed of fine crystal grains with a crystal grain size of 200 ⁇ m or less, and accordingly, the ductility can be improved.
- the B has a function of improving the mechanical strength by precipitating fine borides in the crystal grains through the application of a hot isostatic pressing process which will be described later.
- the fine borides are formed by including borides with a grain size of 0.1 ⁇ m or less.
- the fine borides are formed of TiB, TiB 2 or the like. The precipitation of the fine borides in the crystal grains can improve the mechanical strength such as the tensile strength, the fatigue strength, and the creep strength.
- the balance of the TiAl alloy is Ti and inevitable impurities.
- the inevitable impurities are impurities that may be mixed even if a user has no intension to add.
- the TiAl alloy does not contain Cr (chromium), and therefore, the degradation in the mechanical strength can be suppressed.
- the TiAl alloy does not contain V (vanadium) either, and therefore, the degradation in the mechanical strength and the oxidation resistance can be suppressed. Further, the TiAl alloy does not contain Mo (molybdenum) either, and thus, the degradation in the specific strength can be suppressed.
- a method of manufacturing a TiAl alloy includes a casting step of melting and casting a TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy raw material is melted in a vacuum induction furnace or the like and cast to form an ingot or the like.
- the casting of the TiAl alloy raw material may use a casting system which is used for casting a general metallic material.
- a solidification temperature of the TiAl alloy is lower than that of a conventional TiAl alloy, and thus, it is possible to improve running properties during casting. This enables the formation of a TiAl alloy part such as a turbine blade into a net-shape or a near-net-shape, and accordingly, it is possible to reduce a manufacturing cost. Further, according to the TiAl alloy, to take the superheat is not needed, and accordingly, the castability is improved. In this TiAl alloy, the solidification process passes through the ⁇ single phase region (a solidification). This enables the prevention of the occurrence of columnar crystals in the TiAl alloy and the suppression of the anisotropy.
- the method of manufacturing the TiAl alloy may include a hot isostatic pressing process step for performing a hot isostatic pressing process of applying hot isostatic pressing (HIP) to a cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, at an applied stress range from 158 MPa or higher to 186 MPa or lower, and then, furnace cooling the cast TiAl alloy subjected to the hot isostatic pressing to 900° C., followed by rapid cooling of the cast TiAl alloy from 900° C.
- HIP hot isostatic pressing
- the hot isostatic pressing to the cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, and at an applied stress range from 158 MPa or higher to 186 MPa or lower, it is possible to suppress mainly casting defects including internal defects such as voids caused to the cast TiAl alloy.
- pressure is relieved, the cast TiAl alloy subjected to the hot isostatic pressing is furnace cooled to 900° C., and the cast TiAl alloy subjected to the hot isostatic pressing is rapidly cooled from 900° C., and accordingly, the metal structure can be mainly controlled.
- the rapid cooling from 900° C. may be performed at a cooling rate which is equal to or higher than that of air cooling, and can be performed by gas fan cooling or the like.
- the method of manufacturing the TiAl alloy may include a stress relieving step of relieving stress by holding the TiAl alloy subjected to the hot isostatic pressing process at a temperature range from 800° C. or higher to 950° C. or lower, for a hour range from 1 hour or more to 5 hours or less. Residual stress and the like can be relieved by heat-treating the TiAl alloy subjected to the hot isostatic pressing process to relieve stress. This can further improve the ductility of the TiAl alloy.
- the hot isostatic pressing process and the stress relief may be performed in a vacuum atmosphere, or an inert gas atmosphere with gas such as argon gas.
- a vacuum atmosphere or an inert gas atmosphere with gas such as argon gas.
- HIP equipment or the like which is used for the hot isostatic pressing of a general metallic material can be used.
- an atmosphere furnace or the like which is used for stress relief annealing of a general metallic material can be used.
- the metal structure of the TiAl alloy is formed of fine crystal grains with a crystal grain size of 200 ⁇ m or less. This can improve the ductility of the TiAl alloy. Further, the metal structure of the TiAl alloy is formed of lamellar grains and ⁇ grains, and is free of the segregation of Nb.
- the lamellar grains are formed by regularly arranging ⁇ 2 phases formed of Ti 3 Al and ⁇ phases formed of TiAl in a layered structure.
- the ⁇ grains are formed of TiAl. Boride with a grain size of 0.1 ⁇ m or less is contained in the ⁇ grains.
- the boride is formed of TiB, TiB 2 or the like in a needle shape or the like.
- the lamellar grains can improve the mechanical strength such as the tensile strength, the fatigue strength, and the creep strength.
- the ⁇ grains can improve the ductility and the high-temperature strength.
- the fine borides with a grain size of 0.1 ⁇ m or less can improve the mechanical strength. Relative to a total of the volume fraction of the lamellar grain and the volume fraction of the ⁇ grain being 100 volume %, a volume fraction of the lamellar grains may be 80 volume % or more, and the balance may be ⁇ grains.
- the metal structure of the TiAl alloy is mainly formed of the lamellar grains, and thus, the mechanical strength can be improved. Further, the metal structure of the TiAl alloy is free of the segregation of Nb, and thus, the degradation in the mechanical strength and the ductility can be suppressed.
- the mechanical characteristics of the TiAl alloy at room temperature may be such that Vickers hardness at room temperature is 200 HV or more, when Vickers hardness is measured in accordance with JIS, ASTM, and the like. Further, when tensile tests are performed in accordance with JIS, ASTM, and the like, the mechanical characteristics of the TiAl alloy at room temperature may be such that room temperature ultimate tensile strength is 400 MPa or more and room temperature tensile fracture strain is 1.0% or more.
- the high temperature creep characteristics of the TiAl alloy may be such that the creep strain after the elapse of 200 hours is 2% or less, when creep tests are performed in accordance with JIS, ASTM, and the like under a condition where a temperature is 800° C. and applied stress is 150 MPa. Further, the high temperature creep characteristics of the TiAl alloy may be such that the creep strain after the elapse of 400 hours is 7% or less, when tests are performed under a condition where a temperature is 800° C. and applied stress is 150 MPa.
- FIG. 1 is a diagram showing a constitution of a turbine blade 10 .
- the TiAl alloy has high mechanical strength such as high-temperature strength, and thus, the heat resistance of the turbine blade 10 can be improved. Further, the TiAl alloy has excellent room temperature ductility, and thus, damage to the turbine blade 10 can be suppressed even when the turbine blade 10 is assembled or fitted.
- the above described TiAl alloy contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities. Accordingly, the mechanical strength and the ductility of the TiAl alloy can be improved in a good balance.
- the above described method of manufacturing the TiAl alloy includes a casting step of casting the TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 1 at % or more and 3 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 1 at % or more and 3 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy of Example 1 contained 49.5 at % of Al, 4 at % of Nb, 0.2 at % of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy of Example 2 contained 48 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy of Example 3 contained 49 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities.
- the TiAl alloy of Example 4 contained 50 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities.
- the TiAl alloys in Reference Examples 1 to 3 were set as ternary TiAl alloys containing Nb, the content of Nb was 4 at %, and the content of Al was changed from 48 at % to 50 at %.
- the TiAl alloys in Reference Examples 4 to 8 were set as ternary TiAl alloys containing B, the content of B was 0.1 at %, and the content of Al was changed from 48 at % to 52 at %.
- the TiAl alloys in Reference Examples 9 and 10 were set as quaternary TiAl alloys containing Nb and B, the content of Nb was 4 at %, the content of B was 0.1 at %, and the content of Al was changed from 51 at % to 52 at %.
- the TiAl alloy of Comparative Example 1 contained 48 at % of Al, 2 at % of Nb, 2 at % of Cr, and the balance being Ti and inevitable impurities.
- Each TiAl alloy raw material of each alloy composition shown in Table 1 was melted in a high-frequency vacuum melting furnace and cast to form an ingot of each TiAl alloy of each alloy composition.
- Each TiAl alloy was casted, and then, is subjected to the hot isostatic pressing process.
- the hot isostatic pressing process the cast TiAl alloy was subjected to the hot isostatic pressing at a temperature of 1300 ⁇ 14° C., for an hour of 3 ⁇ 0.1 hours, and at applied stress of 172 ⁇ 14 MPa, and then, the cast TiAl alloy subjected to the hot isostatic pressing was furnace cooled to 900° C., followed by rapid cooling of the cast TiAl alloy subjected to the hot isostatic pressing from 900° C. by gas fan cooling.
- FIG. 2 is a graph showing results of the tensile tests.
- a horizontal axis represents the content of Al
- a vertical axis represents the strain
- Reference Examples 1 to 3 are shown in white diamond shapes.
- Strain indicates fracture strain. From the graph of FIG. 2 , it was found that the room temperature ductility degrades if the content of Al is less than 48 at %, or if the content of Al is more than 50 at %. Further, the strain of Reference Example 2 was larger than that of Reference Examples 1 and 3. This indicates that the room temperature ductility becomes higher if the content of Al is 49 at %.
- FIG. 3A is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 4.
- FIG. 3B is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 5.
- FIG. 3C is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 6.
- FIG. 3D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 7.
- FIG. 3E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 8.
- FIG. 3A is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 4.
- FIG. 4A is a photograph showing result of the observation of metal structure of TiAl alloy of Example 2.
- FIG. 4B is a photograph showing result of the observation of metal structure of TiAl alloy of Example 3.
- FIG. 4C is a photograph showing result of the observation of metal structure of TiAl alloy of Example 4.
- FIG. 4D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 9.
- FIG. 4E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 10.
- the metal structures of Examples 2 to 4 were formed of fine crystal grains with a crystal grain size of 200 ⁇ m or less.
- the metal structures of Examples 2 to 4 were formed of lamellar grains and ⁇ grains, and boride with a grain size of 0.1 ⁇ m or less was contained in the ⁇ grains.
- a volume fraction of the lamellar grains is 80 volume % or more, and the balance is the ⁇ grains.
- FIGS. 5 and 6 are graph showing measurement results of Vickers hardness of the TiAl alloys before being subjected to the hot isostatic pressing process.
- FIGS. 5 and 6 are graph showing measurement results of Vickers hardness of the TiAl alloys subjected to the hot isostatic pressing process.
- a horizontal axis represents the content of Al of each TiAl alloy
- a vertical axis represents Vickers hardness
- Vickers hardness of the TiAl alloys of Examples 2 to 4 is indicated by white circles
- Vickers hardness of the TiAl alloys of Examples 4 to 10 is indicated by black circles.
- Vickers hardness of the TiAl alloys of Examples 2 to before and after being subjected to the hot isostatic pressing process was 200 HV or more. Further, if the content of Al of the TiAl alloy was in a range from 48 at % or more to 50 at % or less, Vickers hardness of Examples 2 to 4 was larger than Vickers hardness of Reference Examples 4 to 6. On the other hand, if the content of Al of the TiAl alloy was more than 50 at %, Vickers hardness of Reference Examples 7 and 8 was substantially the same as Vickers hardness of Reference Examples 9 and 10. From this result, it is considered that Nb contributes to the improvement of the mechanical strength, if the content of Al of the TiAl alloy is in a range from 48 at % or more to 50 at % or less.
- Example 1 had greater room temperature strength than Comparative Example 1. Further, the room temperature ductility of Example 1 was substantially the same as that of Comparative Example 1. More specifically, the room temperature ultimate tensile strength of Example 1 was 400 MPa or more, and the room temperature tensile fracture strain of Example 1 was 1.0% or more.
- FIG. 8 is a graph showing results of the creep tests.
- FIG. 8 shows a creep curve of each TiAl alloy, with a horizontal axis representing a creep time and a vertical axis representing creep strain.
- the high temperature creep characteristics of Example 1 were four times or more higher than those of Comparative Example 1. As described above, Example 1 had more improved high temperature creep characteristic than Comparative Example 1.
- Example 1 the high temperature creep characteristics of Example 1 were such that the creep strain after the elapse of 200 hours was % or less, when the tests were performed at a test temperature of 800° C. and applied stress of 150 MPa.
- the high temperature creep characteristics of Example 1 were such that the creep strain after the elapse of 400 hours was 7% or less when the tests were performed at the test temperature of 800° C. and the applied stress of 150 MPa.
- the TiAl alloy of Example 1 had excellent mechanical strength and ductility which were improved in a good balance.
- the TiAl alloy of Comparative Example 1 had more degraded room temperature strength and high temperature mechanical characteristics than the TiAl alloy of Example 1. The reason for the above degradation is considered to be due to the influence or the like of Cr contained in the TiAl alloy of Comparative Example 1.
- FIG. 9A is a photograph showing result of the observation of cross-sectional area of Example 1 after performing oxidation test.
- FIG. 9B is a photograph showing result of the observation of cross-sectional area of Comparative Example 1 after performing oxidation test.
- the thickness of the oxide layer of Example 1 was 2.8 ⁇ m.
- the thickness of the oxide layer of Comparative Example 1 was 4.3 ⁇ m. From this result, it was found that Example 1 had more excellent oxidation resistance than Comparative Example 1.
- the present disclosure can improve the mechanical strength and the ductility of a TiAl alloy in a good balance, and thus, is useful for turbine blades and the like of aircraft engine components.
Landscapes
- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Thermal Sciences (AREA)
- Crystallography & Structural Chemistry (AREA)
- Turbine Rotor Nozzle Sealing (AREA)
Abstract
Description
- This application is a continuation application of International Application No. PCT/JP2020/011936, filed on Mar. 18, 2020, which claims priority to Japanese Patent Application No. 2019-096652, filed on May 23, 2019, the entire contents of which are incorporated by references herein.
- The present disclosure relates to a TiAl alloy and a method of manufacturing the same.
- A TiAl (titanium aluminide) alloy is an alloy formed of an intermetallic compound of Ti and Al. The TiAl alloy is excellent in the heat resistance, and has a lighter weight and larger specific strength than an Ni-base alloy, and thus, is applied to aircraft engine components such as turbine blades. For such the TiAl alloy, a TiAl alloy containing Cr and Nb is used. See Japanese Patent Application Publication No. 2013-209750 (Patent Literature 1).
- In order to reduce the weight of TiAl alloy parts such as turbine blades, to increase the specific strength of the TiAl alloy by increasing the strength of the TiAl alloy is needed. However, in a conventional TiAl alloy, it is difficult to increase the strength by improving the mechanical strength and the ductility in a good balance, and if the ductility is increased, the mechanical strength may degrade.
- Therefore, an object of the present disclosure is to provide a TiAl alloy capable of improving the mechanical strength and the ductility of the TiAl alloy in a good balance, and a method of manufacturing the same.
- A TiAl alloy according to the present disclosure contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- In the TiAl alloy according to the present disclosure, the content of Al may be 49 at %.
- In the TiAl alloy according to the present disclosure, a metal structure may be formed of lamellar grains and γ grains, and may be free of the segregation of Nb.
- In the TiAl alloy according to the present disclosure, a volume fraction of the lamellar grains may be 80 volume % or more, relative to a total of the volume fraction of the lamellar grain and the volume fraction of the γ grain being 100 volume %.
- In the TiAl alloy according to the present disclosure, Vickers hardness at a room temperature may be 200 HV or more.
- In the TiAl alloy according to the present disclosure, room temperature ultimate tensile strength may be 400 MPa or more and room temperature tensile fracture strain may be 1.0° or more.
- In the TiAl alloy according to the present disclosure, creep strain after the elapse of 200 hours may be 2% or less, when a temperature is 800° C. and applied stress is 150 MPa.
- A method of manufacturing a TiAl alloy according to the present disclosure includes a casting step of casting a TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities.
- In the method of manufacturing the TiAl alloy according to the present disclosure, in the casting step, a solidification process may pass through an a single phase region.
- The method of manufacturing the TiAl alloy according to the present disclosure may include a hot isostatic pressing process step for performing a hot isostatic pressing process of applying hot isostatic pressing to the cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, at an applied stress range from 158 MPa or higher to 186 MPa or lower, and then furnace cooling the cast TiAl alloy subjected to the hot isostatic pressing to 900° C., followed by rapid cooling of the cast TiAl alloy subjected to the hot isostatic pressing from 900° C.
- The method of manufacturing the TiAl alloy according to the present disclosure may include a stress relieving step of relieving stress by holding the TiAl alloy subjected to the hot isostatic pressing process at a temperature range from 800° C. or higher to 950° C. or lower for a hour range from 1 hour or more to 5 hours or less.
- According to the thus-configured TiAl alloy and the thus-configured method of manufacturing the same, the mechanical strength and the ductility of the TiAl alloy can be improved in a good balance.
-
FIG. 1 shows a constitution of a turbine blade in an embodiment of the present disclosure. -
FIG. 2 is a graph showing results of tensile tests in an embodiment of the present disclosure. -
FIG. 3A is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 4 in an embodiment of the present disclosure. -
FIG. 3B is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 5 in an embodiment of the present disclosure. -
FIG. 3C is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 6 in an embodiment of the present disclosure. -
FIG. 3D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 7 in an embodiment of the present disclosure. -
FIG. 3E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 8 in an embodiment of the present disclosure. -
FIG. 4A is a photograph showing result of the observation of metal structure of TiAl alloy of Example 2 in an embodiment of the present disclosure. -
FIG. 4B is a photograph showing result of the observation of metal structure of TiAl alloy of Example 3 in an embodiment of the present disclosure. -
FIG. 4C is a photograph showing result of the observation of metal structure of TiAl alloy of Example 4 in an embodiment of the present disclosure. -
FIG. 4D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 9 in an embodiment of the present disclosure. -
FIG. 4E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 10 in an embodiment of the present disclosure. -
FIG. 5 is a graph showing results of the measurement of Vickers hardness of TiAl alloys before being subjected to hot isostatic pressing process, in an embodiment of the present disclosure. -
FIG. 6 is a graph showing results of the measurement of Vickers hardness of TiAl alloys subjected to hot isostatic pressing process, in an embodiment of the present disclosure. -
FIG. 7 is a graph showing results of tensile tests in an embodiment of the present disclosure. -
FIG. 8 is a graph showing results of creep tests, in an embodiment of the present disclosure. -
FIG. 9A is a photograph showing result of the observation of cross-sectional area of Example 1 after performing oxidation test, in an embodiment of the present disclosure. -
FIG. 9B is a photograph showing result of the observation of cross-sectional area of Comparative Example 1 after performing oxidation test, in an embodiment of the present disclosure. - An embodiment of the present disclosure will be described in detail below with reference to the drawings. A TiAl (titanium aluminide) alloy according to an embodiment of the present disclosure contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities. Next, the reason why a composition range of each alloy component contained in the TiAl alloy is limited will be explained.
- Al (aluminium) has a function of improving the mechanical strength and the ductility such as the room temperature ductility. The content of Al is in a range from 48 at % or more to 50 at % or less. The ductility degrades if the content of Al is less than 48 at %. The ductility degrades if the content of Al is more than 50 at %. Further, if the content of Al is more than 50 at %, a solidification process changes from an a single phase region (a solidification) to a γ single phase region (γ solidification), and thus, a columnar crystal is formed, and there is a possibility that the anisotropy occurs. By setting the content of Al in a range from 48 at % or more to 50 at % or less, the solidification process can be in the α single phase region (a solidification), and this can suppresses the anisotropy. Further, the mechanical strength and the ductility can be further improved by setting the content of Al to 49 at %.
- Nb (niobium) has a function of improving the oxidation resistance and the mechanical strength. The content of Nb is in a range from 3 at % or more to 5 at % or less. If the content of Nb is less than 3 at %, the oxidation resistance and the high-temperature strength degrade. If the content of Nb is more than 5 at %, the ductility such as the room temperature ductility degrades. Further, if the content of Nb is 5 at % or less, the segregation of Nb can be suppressed. The occurrence of the segregation of Nb may degrade the mechanical strength and the ductility.
- B (boron) has a function of enhancing the ductility such as the room temperature ductility by refining crystal grains. The content of B is in a range from 0.1 at % or more to 0.3 at % or less. If the content of B is less than 0.1 at %, the crystal grains are coarsened and the ductility degrades. If the content of B is more than 0.3 at %, impact characteristics may be degraded. By setting the content of B in a range from 0.1 at % or more to 0.3 at % or less, the TiAl alloy comes to be formed of fine crystal grains with a crystal grain size of 200 μm or less, and accordingly, the ductility can be improved.
- B has a function of improving the mechanical strength by precipitating fine borides in the crystal grains through the application of a hot isostatic pressing process which will be described later. The fine borides are formed by including borides with a grain size of 0.1 μm or less. The fine borides are formed of TiB, TiB2 or the like. The precipitation of the fine borides in the crystal grains can improve the mechanical strength such as the tensile strength, the fatigue strength, and the creep strength.
- The balance of the TiAl alloy is Ti and inevitable impurities. The inevitable impurities are impurities that may be mixed even if a user has no intension to add. The TiAl alloy does not contain Cr (chromium), and therefore, the degradation in the mechanical strength can be suppressed. The TiAl alloy does not contain V (vanadium) either, and therefore, the degradation in the mechanical strength and the oxidation resistance can be suppressed. Further, the TiAl alloy does not contain Mo (molybdenum) either, and thus, the degradation in the specific strength can be suppressed.
- Next, a method of manufacturing a TiAl alloy according to an embodiment of the present disclosure will be described.
- A method of manufacturing a TiAl alloy includes a casting step of melting and casting a TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities. The TiAl alloy raw material is melted in a vacuum induction furnace or the like and cast to form an ingot or the like. The casting of the TiAl alloy raw material may use a casting system which is used for casting a general metallic material.
- A solidification temperature of the TiAl alloy is lower than that of a conventional TiAl alloy, and thus, it is possible to improve running properties during casting. This enables the formation of a TiAl alloy part such as a turbine blade into a net-shape or a near-net-shape, and accordingly, it is possible to reduce a manufacturing cost. Further, according to the TiAl alloy, to take the superheat is not needed, and accordingly, the castability is improved. In this TiAl alloy, the solidification process passes through the α single phase region (a solidification). This enables the prevention of the occurrence of columnar crystals in the TiAl alloy and the suppression of the anisotropy.
- The method of manufacturing the TiAl alloy may include a hot isostatic pressing process step for performing a hot isostatic pressing process of applying hot isostatic pressing (HIP) to a cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, at an applied stress range from 158 MPa or higher to 186 MPa or lower, and then, furnace cooling the cast TiAl alloy subjected to the hot isostatic pressing to 900° C., followed by rapid cooling of the cast TiAl alloy from 900° C. By performing the hot isostatic pressing process, it is possible to suppress casting defects such as voids and control a metal structure.
- More specifically, by applying the hot isostatic pressing to the cast TiAl alloy at a temperature range from 1250° C. or higher to 1350° C. or lower, for a hour range from 1 hour or more to 5 hours or less, and at an applied stress range from 158 MPa or higher to 186 MPa or lower, it is possible to suppress mainly casting defects including internal defects such as voids caused to the cast TiAl alloy. After performing the hot isostatic pressing to the cast TiAl alloy, pressure is relieved, the cast TiAl alloy subjected to the hot isostatic pressing is furnace cooled to 900° C., and the cast TiAl alloy subjected to the hot isostatic pressing is rapidly cooled from 900° C., and accordingly, the metal structure can be mainly controlled. The rapid cooling from 900° C. may be performed at a cooling rate which is equal to or higher than that of air cooling, and can be performed by gas fan cooling or the like.
- The method of manufacturing the TiAl alloy may include a stress relieving step of relieving stress by holding the TiAl alloy subjected to the hot isostatic pressing process at a temperature range from 800° C. or higher to 950° C. or lower, for a hour range from 1 hour or more to 5 hours or less. Residual stress and the like can be relieved by heat-treating the TiAl alloy subjected to the hot isostatic pressing process to relieve stress. This can further improve the ductility of the TiAl alloy.
- In order to prevent the oxidation, the hot isostatic pressing process and the stress relief may be performed in a vacuum atmosphere, or an inert gas atmosphere with gas such as argon gas. For the hot isostatic pressing, HIP equipment or the like which is used for the hot isostatic pressing of a general metallic material can be used. For the stress relief, an atmosphere furnace or the like which is used for stress relief annealing of a general metallic material can be used.
- Next, the metal structure of the TiAl alloy will be described. The metal structure of the TiAl alloy is formed of fine crystal grains with a crystal grain size of 200 μm or less. This can improve the ductility of the TiAl alloy. Further, the metal structure of the TiAl alloy is formed of lamellar grains and γ grains, and is free of the segregation of Nb. The lamellar grains are formed by regularly arranging α2 phases formed of Ti3Al and γ phases formed of TiAl in a layered structure. The γ grains are formed of TiAl. Boride with a grain size of 0.1 μm or less is contained in the γ grains. The boride is formed of TiB, TiB2 or the like in a needle shape or the like.
- The lamellar grains can improve the mechanical strength such as the tensile strength, the fatigue strength, and the creep strength. The γ grains can improve the ductility and the high-temperature strength. The fine borides with a grain size of 0.1 μm or less can improve the mechanical strength. Relative to a total of the volume fraction of the lamellar grain and the volume fraction of the γ grain being 100 volume %, a volume fraction of the lamellar grains may be 80 volume % or more, and the balance may be γ grains. The metal structure of the TiAl alloy is mainly formed of the lamellar grains, and thus, the mechanical strength can be improved. Further, the metal structure of the TiAl alloy is free of the segregation of Nb, and thus, the degradation in the mechanical strength and the ductility can be suppressed.
- Next, mechanical characteristics of the TiAl alloy according to the embodiment of the present disclosure will be described. The mechanical characteristics of the TiAl alloy at room temperature may be such that Vickers hardness at room temperature is 200 HV or more, when Vickers hardness is measured in accordance with JIS, ASTM, and the like. Further, when tensile tests are performed in accordance with JIS, ASTM, and the like, the mechanical characteristics of the TiAl alloy at room temperature may be such that room temperature ultimate tensile strength is 400 MPa or more and room temperature tensile fracture strain is 1.0% or more. The high temperature creep characteristics of the TiAl alloy may be such that the creep strain after the elapse of 200 hours is 2% or less, when creep tests are performed in accordance with JIS, ASTM, and the like under a condition where a temperature is 800° C. and applied stress is 150 MPa. Further, the high temperature creep characteristics of the TiAl alloy may be such that the creep strain after the elapse of 400 hours is 7% or less, when tests are performed under a condition where a temperature is 800° C. and applied stress is 150 MPa.
- The TiAl alloy according to the embodiment of the present disclosure can be applied to a turbine blade or the like of an aircraft engine component.
FIG. 1 is a diagram showing a constitution of aturbine blade 10. The TiAl alloy has high mechanical strength such as high-temperature strength, and thus, the heat resistance of theturbine blade 10 can be improved. Further, the TiAl alloy has excellent room temperature ductility, and thus, damage to theturbine blade 10 can be suppressed even when theturbine blade 10 is assembled or fitted. - The above described TiAl alloy contains 48 at % or more and 50 at % or less of Al, 3 at % or more and 5 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities. Accordingly, the mechanical strength and the ductility of the TiAl alloy can be improved in a good balance.
- The above described method of manufacturing the TiAl alloy includes a casting step of casting the TiAl alloy raw material which contains 48 at % or more and 50 at % or less of Al, 1 at % or more and 3 at % or less of Nb, 0.1 at % or more and 0.3 at % or less of B, and the balance being Ti and inevitable impurities. As a result, the TiAl alloy with the mechanical strength and the ductility which are improved in a good balance can be manufactured, and also the castability can be improved because running properties are favorable.
- First, TiAl alloys of Examples 1 to 4, Reference Examples 1 to 10, and Comparative Example 1 will be described.
- An alloy composition of each TiAl alloy is shown in Table 1.
-
TABLE 1 ALLOY COMPOSITION (at %) TI AND INEVITABLE Al Nb B Cr IMPURITIES EXAMPLE 1 49.5 4 0.2 — BALANCE EXAMPLE 2 48 4 0.1 — BALANCE EXAMPLE 3 49 4 0.1 — BALANCE EXAMPLE 4 50 4 0.1 — BALANCE REFERENCE 48 4 — — BALANCE EXAMPLE 1 REFERENCE 49 4 — — BALANCE EXAMPLE 2 REFERENCE 50 4 — — BALANCE EXAMPLE 3 REFERENCE 48 — 0.1 — BALANCE EXAMPLE 4 REFERENCE 49 — 0.1 — BALANCE EXAMPLE 5 REFERENCE 50 — 0.1 — BALANCE EXAMPLE 6 REFERENCE 51 — 0.1 — BALANCE EXAMPLE 7 REFERENCE 52 — 0.1 — BALANCE EXAMPLE 8 REFERENCE 51 4 0.1 — BALANCE EXAMPLE 9 REFERENCE 52 4 0.1 — BALANCE EXAMPLE 10 COMPARATIVE 48 2 — 2 BALANCE EXAMPLE 1 - The TiAl alloy of Example 1 contained 49.5 at % of Al, 4 at % of Nb, 0.2 at % of B, and the balance being Ti and inevitable impurities. The TiAl alloy of Example 2 contained 48 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities. The TiAl alloy of Example 3 contained 49 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities. The TiAl alloy of Example 4 contained 50 at % of Al, 4 at % of Nb, 0.1 at % of B, and the balance being Ti and inevitable impurities.
- The TiAl alloys in Reference Examples 1 to 3 were set as ternary TiAl alloys containing Nb, the content of Nb was 4 at %, and the content of Al was changed from 48 at % to 50 at %. The TiAl alloys in Reference Examples 4 to 8 were set as ternary TiAl alloys containing B, the content of B was 0.1 at %, and the content of Al was changed from 48 at % to 52 at %. The TiAl alloys in Reference Examples 9 and 10 were set as quaternary TiAl alloys containing Nb and B, the content of Nb was 4 at %, the content of B was 0.1 at %, and the content of Al was changed from 51 at % to 52 at %. The TiAl alloy of Comparative Example 1 contained 48 at % of Al, 2 at % of Nb, 2 at % of Cr, and the balance being Ti and inevitable impurities.
- Each TiAl alloy raw material of each alloy composition shown in Table 1 was melted in a high-frequency vacuum melting furnace and cast to form an ingot of each TiAl alloy of each alloy composition. Each TiAl alloy was casted, and then, is subjected to the hot isostatic pressing process. In the hot isostatic pressing process, the cast TiAl alloy was subjected to the hot isostatic pressing at a temperature of 1300±14° C., for an hour of 3±0.1 hours, and at applied stress of 172±14 MPa, and then, the cast TiAl alloy subjected to the hot isostatic pressing was furnace cooled to 900° C., followed by rapid cooling of the cast TiAl alloy subjected to the hot isostatic pressing from 900° C. by gas fan cooling.
- Effects of Al in the TiAl alloys were evaluated. Tensile tests were performed at room temperature for the TiAl alloys of Reference Examples 1 to 3. The tensile tests were performed in accordance with ASTM E8.
FIG. 2 is a graph showing results of the tensile tests. In the graph ofFIG. 2 , a horizontal axis represents the content of Al, a vertical axis represents the strain, and Reference Examples 1 to 3 are shown in white diamond shapes. Strain indicates fracture strain. From the graph ofFIG. 2 , it was found that the room temperature ductility degrades if the content of Al is less than 48 at %, or if the content of Al is more than 50 at %. Further, the strain of Reference Example 2 was larger than that of Reference Examples 1 and 3. This indicates that the room temperature ductility becomes higher if the content of Al is 49 at %. - The metal structures of the TiAl alloys were evaluated. The metal structures of the TiAl alloys of Examples 2 to 4 and Reference Examples 4 to 10 were observed. The metal structures were observed by using an optical microscope.
FIG. 3A is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 4.FIG. 3B is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 5.FIG. 3C is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 6.FIG. 3D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 7.FIG. 3E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 8.FIG. 4A is a photograph showing result of the observation of metal structure of TiAl alloy of Example 2.FIG. 4B is a photograph showing result of the observation of metal structure of TiAl alloy of Example 3.FIG. 4C is a photograph showing result of the observation of metal structure of TiAl alloy of Example 4.FIG. 4D is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 9.FIG. 4E is a photograph showing result of the observation of metal structure of TiAl alloy of Reference Example 10. - As shown in
FIGS. 3A to 3C , in Reference Examples 4 to 6, a metal structure in which the solidification process was in the α single phase region (a solidification) was observed. On the other hand, as shown inFIGS. 3D and 3E , in Reference Examples 7 and 8, a metal structure in which the solidification process was in the γ single phase region (γ solidification) was observed. In the metal structure in which the solidification process was in the γ single phase region (γ solidification), columnar crystals were formed and the anisotropy was observed. As shown inFIGS. 4A to 4C , in Examples 2 to 4, a metal structure in which the solidification process was in the α single phase region (a solidification) was observed. On the other hand, as shown inFIGS. 4D to 4E , in Reference Examples 9 and 10, a metal structure in which the solidification process was in the γ single phase region (γ solidification) was observed. In the metal structure in which the solidification process was in the γ single phase region (γ solidification), columnar crystals were formed, and the anisotropy was observed. From this result, it was found that if the content of Al is more than 50 at %, the solidification process was in the γ single phase region (γ solidification), and the anisotropy occurs. - As shown in
FIGS. 4A to 4C , the metal structures of Examples 2 to 4 were formed of fine crystal grains with a crystal grain size of 200 μm or less. The metal structures of Examples 2 to 4 were formed of lamellar grains and γ grains, and boride with a grain size of 0.1 μm or less was contained in the γ grains. In the metal structures of Examples 2 to 4, relative to a total of the volume fraction of the lamellar grain and the volume fraction of the γ grain being 100 volume °, a volume fraction of the lamellar grains is 80 volume % or more, and the balance is the γ grains. An area ratio of each grain was calculated by applying image processing to information on the contrast of each grain in the photographs of the metal structures, and the thus obtained area ratio was regarded as the volume fraction of each grain. In the metal structures of Examples 2 to 4, the segregation of Nb was not observed. - The hardness of the TiAl alloy before and after being subjected to the hot isostatic pressing process was evaluated. Vickers hardness of the TiAl alloys of Examples 2 to 4 and Reference Examples 4 to 10 was measured at room temperature. Vickers hardness was measured in accordance with ASTM E 92.
FIG. 5 is a graph showing measurement results of Vickers hardness of the TiAl alloys before being subjected to the hot isostatic pressing process.FIG. 6 is a graph showing measurement results of Vickers hardness of the TiAl alloys subjected to the hot isostatic pressing process. InFIGS. 5 and 6 , a horizontal axis represents the content of Al of each TiAl alloy, a vertical axis represents Vickers hardness, Vickers hardness of the TiAl alloys of Examples 2 to 4 is indicated by white circles, and Vickers hardness of the TiAl alloys of Examples 4 to 10 is indicated by black circles. - Vickers hardness of the TiAl alloys of Examples 2 to before and after being subjected to the hot isostatic pressing process was 200 HV or more. Further, if the content of Al of the TiAl alloy was in a range from 48 at % or more to 50 at % or less, Vickers hardness of Examples 2 to 4 was larger than Vickers hardness of Reference Examples 4 to 6. On the other hand, if the content of Al of the TiAl alloy was more than 50 at %, Vickers hardness of Reference Examples 7 and 8 was substantially the same as Vickers hardness of Reference Examples 9 and 10. From this result, it is considered that Nb contributes to the improvement of the mechanical strength, if the content of Al of the TiAl alloy is in a range from 48 at % or more to 50 at % or less.
- The room temperature mechanical characteristics of the TiAl alloys were evaluated. Tensile tests were performed at room temperature for the TiAl alloys of Example 1 and Comparative Example 1. The tensile tests were performed in accordance with ASTM E8.
FIG. 7 is a graph showing results of the tensile tests.FIG. 7 shows a stress-strain curve of each TiAl alloy, with a horizontal axis representing strain and a vertical axis representing stress. Example 1 had greater room temperature strength than Comparative Example 1. Further, the room temperature ductility of Example 1 was substantially the same as that of Comparative Example 1. More specifically, the room temperature ultimate tensile strength of Example 1 was 400 MPa or more, and the room temperature tensile fracture strain of Example 1 was 1.0% or more. - The high temperature mechanical characteristics of the TiAl alloys were evaluated. Creep tests were performed at high temperature for the TiAl alloys of Example 1 and Comparative Example 1. The creep tests were performed in accordance with ASTM E 139. In a creep test condition, a test temperature was 800° C. and applied stress was 150 MPa.
FIG. 8 is a graph showing results of the creep tests.FIG. 8 shows a creep curve of each TiAl alloy, with a horizontal axis representing a creep time and a vertical axis representing creep strain. The high temperature creep characteristics of Example 1 were four times or more higher than those of Comparative Example 1. As described above, Example 1 had more improved high temperature creep characteristic than Comparative Example 1. More specifically, the high temperature creep characteristics of Example 1 were such that the creep strain after the elapse of 200 hours was % or less, when the tests were performed at a test temperature of 800° C. and applied stress of 150 MPa. The high temperature creep characteristics of Example 1 were such that the creep strain after the elapse of 400 hours was 7% or less when the tests were performed at the test temperature of 800° C. and the applied stress of 150 MPa. - As shown in
FIGS. 7 and 8 , it was found that the TiAl alloy of Example 1 had excellent mechanical strength and ductility which were improved in a good balance. On the other hand, the TiAl alloy of Comparative Example 1 had more degraded room temperature strength and high temperature mechanical characteristics than the TiAl alloy of Example 1. The reason for the above degradation is considered to be due to the influence or the like of Cr contained in the TiAl alloy of Comparative Example 1. - The oxidation resistance of the TiAl alloys was evaluated. Oxidation tests were performed for the TiAl alloys of Example 1 and Comparative Example 1. The oxidation tests were performed by continuous oxidization at a temperature of 750° C. for a hour of 200 hours in air atmosphere. After performing the oxidation tests, the observation of cross-sectional areas was performed to evaluate the thickness of oxide layers.
FIG. 9A is a photograph showing result of the observation of cross-sectional area of Example 1 after performing oxidation test.FIG. 9B is a photograph showing result of the observation of cross-sectional area of Comparative Example 1 after performing oxidation test. The thickness of the oxide layer of Example 1 was 2.8 μm. The thickness of the oxide layer of Comparative Example 1 was 4.3 μm. From this result, it was found that Example 1 had more excellent oxidation resistance than Comparative Example 1. - The present disclosure can improve the mechanical strength and the ductility of a TiAl alloy in a good balance, and thus, is useful for turbine blades and the like of aircraft engine components.
Claims (11)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2019096652 | 2019-05-23 | ||
JP2019-096652 | 2019-05-23 | ||
PCT/JP2020/011936 WO2020235201A1 (en) | 2019-05-23 | 2020-03-18 | Tial alloy and production method therefor |
Related Parent Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/JP2020/011936 Continuation WO2020235201A1 (en) | 2019-05-23 | 2020-03-18 | Tial alloy and production method therefor |
Publications (1)
Publication Number | Publication Date |
---|---|
US20220010410A1 true US20220010410A1 (en) | 2022-01-13 |
Family
ID=73458590
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US17/449,132 Abandoned US20220010410A1 (en) | 2019-05-23 | 2021-09-28 | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME |
Country Status (4)
Country | Link |
---|---|
US (1) | US20220010410A1 (en) |
EP (1) | EP3974082A4 (en) |
JP (1) | JP7226536B2 (en) |
WO (1) | WO2020235201A1 (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20220017995A1 (en) * | 2019-05-23 | 2022-01-20 | Ihi Corporation | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME |
Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040045644A1 (en) * | 2000-05-17 | 2004-03-11 | Volker Guther | T-tial alloy-based component comprising areas having a graduated structure |
US20220017995A1 (en) * | 2019-05-23 | 2022-01-20 | Ihi Corporation | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME |
Family Cites Families (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP2679109B2 (en) * | 1988-05-27 | 1997-11-19 | 住友金属工業株式会社 | Intermetallic compound TiA-based light-weight heat-resistant alloy |
ATE127860T1 (en) * | 1990-05-04 | 1995-09-15 | Asea Brown Boveri | HIGH TEMPERATURE ALLOY FOR MACHINE COMPONENTS BASED ON DOPED TITANIUM ALUMINIDE. |
US5205875A (en) * | 1991-12-02 | 1993-04-27 | General Electric Company | Wrought gamma titanium aluminide alloys modified by chromium, boron, and nionium |
JPH0649569A (en) * | 1992-07-30 | 1994-02-22 | Sumitomo Light Metal Ind Ltd | High strength tial intermetallic compound |
JPH08283890A (en) * | 1995-04-13 | 1996-10-29 | Nippon Steel Corp | Tial-base intermetallic compound excellent in creep resistance and its production |
JP3459138B2 (en) * | 1995-04-24 | 2003-10-20 | 日本発条株式会社 | TiAl-based intermetallic compound joined body and method for producing the same |
DE102004056582B4 (en) | 2004-11-23 | 2008-06-26 | Gkss-Forschungszentrum Geesthacht Gmbh | Alloy based on titanium aluminides |
CN100425722C (en) * | 2005-11-30 | 2008-10-15 | 济南大学 | Method for improving property of TiAI intermetallic compound based composite material |
US10597756B2 (en) | 2012-03-24 | 2020-03-24 | General Electric Company | Titanium aluminide intermetallic compositions |
CN106987754B (en) * | 2017-05-03 | 2018-10-19 | 西北工业大学 | A kind of Cast γ-TiAl Alloy being suitable for 800 DEG C |
-
2020
- 2020-03-18 EP EP20810724.3A patent/EP3974082A4/en active Pending
- 2020-03-18 WO PCT/JP2020/011936 patent/WO2020235201A1/en unknown
- 2020-03-18 JP JP2021520074A patent/JP7226536B2/en active Active
-
2021
- 2021-09-28 US US17/449,132 patent/US20220010410A1/en not_active Abandoned
Patent Citations (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20040045644A1 (en) * | 2000-05-17 | 2004-03-11 | Volker Guther | T-tial alloy-based component comprising areas having a graduated structure |
US20220017995A1 (en) * | 2019-05-23 | 2022-01-20 | Ihi Corporation | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20220017995A1 (en) * | 2019-05-23 | 2022-01-20 | Ihi Corporation | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME |
Also Published As
Publication number | Publication date |
---|---|
JP7226536B2 (en) | 2023-02-21 |
WO2020235201A1 (en) | 2020-11-26 |
EP3974082A1 (en) | 2022-03-30 |
JPWO2020235201A1 (en) | 2020-11-26 |
EP3974082A4 (en) | 2023-05-31 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US20220017995A1 (en) | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME | |
US20130206287A1 (en) | Co-based alloy | |
US11078563B2 (en) | TiAl alloy and method of manufacturing the same | |
US20120263623A1 (en) | Titanium aluminide based alloy | |
US11692246B2 (en) | Ni-based alloy for hot-working die, and hot-forging die using same | |
US20160145703A1 (en) | HOT-FORGED TiAl-BASED ALLOY AND METHOD FOR PRODUCING THE SAME | |
US20220010410A1 (en) | TiAl ALLOY AND METHOD OF MANUFACTURING THE SAME | |
US20210404042A1 (en) | Titanium aluminide alloy material for hot forging, forging method for titanium aluminide alloy material, and forged body | |
JP2019065344A (en) | Low thermal expansion alloy | |
EP3042973B1 (en) | A nickel alloy | |
WO2020059846A1 (en) | Ni-based alloy for hot die, and hot forging die obtained using same | |
KR20200095413A (en) | High temperature titanium alloy and method for manufacturing the same | |
US20220205075A1 (en) | METHOD OF MANUFACTURING TiAl ALLOY AND TiAl ALLOY | |
WO2017123186A1 (en) | Tial-based alloys having improved creep strength by strengthening of gamma phase | |
KR101346808B1 (en) | The Titanium alloy improved mechanical properties and the manufacturing method thereof | |
EP0634496B1 (en) | High strength and high ductility TiAl-based intermetallic compound | |
WO2022260026A1 (en) | Tial alloy, tial alloy powder, tial alloy component, and method for producing same | |
JPH08337832A (en) | Titanium-aluminium intermetallic compound-base alloy and its production | |
US20220002854A1 (en) | Titanium aluminide alloy material for hot forging and forging method for titanium aluminide alloy material |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
AS | Assignment |
Owner name: IHI CORPORATION, JAPAN Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KUBUSHIRO, KEIJI;REEL/FRAME:057621/0884 Effective date: 20210823 |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: DOCKETED NEW CASE - READY FOR EXAMINATION |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: NON FINAL ACTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: RESPONSE TO NON-FINAL OFFICE ACTION ENTERED AND FORWARDED TO EXAMINER |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: FINAL REJECTION MAILED |
|
STPP | Information on status: patent application and granting procedure in general |
Free format text: ADVISORY ACTION MAILED |
|
STCB | Information on status: application discontinuation |
Free format text: ABANDONED -- FAILURE TO RESPOND TO AN OFFICE ACTION |