Cyclic creep deformation method for inducing selective precipitation of Ti2Al phase

Abstract

The invention discloses a cyclic creep deformation method for inducing selective precipitation of a Ti2Al phase, and relates to the technical field of high-niobium TiAl alloys. The invention aims to solve the technical problem that a reinforced phase Ti2Al phase precipitated on a B2 / gamma phase interface is difficult to obtain at present. The method comprises: 1, raw material preparation; 2, smelting; 3, homogenizing annealing treatment; and 4, cyclic creep deformation. According to the cyclic creep deformation method in the trapezoidal wave load form, the Ti2Al phase is effectively induced to be selectively separated out at the B2 / gamma phase interface part by utilizing reasonable peak value and valley value stress and load holding time, and the separated-out Ti2Al phase can effectively pinning dislocation and relieve local stress concentration of the B2 / gamma phase interface. The cyclic creep deformation method also activates a dislocation slippage system in the B2 phase, improves the deformability of the brittle B2 phase, and promotes coordinated deformation between the B2 phase and the gamma phase. The method is used for obtaining the high-performance TiAl alloy.

Description

Technical Field

[0001] The present invention relates to the technical field of high-niobium TiAl alloys, and specifically to a cyclic creep deformation method for inducing selective precipitation of Ti2Al phase. Background Art

[0002] Since the development of high-niobium TiAl alloys, due to their advantages such as low density, high specific strength, high specific stiffness, and excellent oxidation resistance, they have been highly favored by researchers and meet the increasingly stringent requirements of the aerospace industry for lightweight and high-temperature-resistant engine blade materials. Therefore, high-niobium TiAl alloys are considered as a new generation of aviation engine blade materials that are expected to replace some nickel-based superalloys.

[0003] To meet the serviceability requirements, it is of great engineering significance to develop TiAl alloys with excellent coordination of strength and toughness. According to a large number of literature searches, TiAl alloys with different microstructures have different properties. Among the four typical microstructures of near-γ microstructure, duplex microstructure, near-lamellar microstructure, and fully lamellar microstructure, the TiAl alloy with a near-lamellar structure still has a certain plasticity on the premise of relatively high strength. The near-lamellar microstructure is mainly composed of α2 / γ lamellar clusters and massive B2 phase and γ phase at the interfaces (grain boundaries) of the lamellar clusters. Among them, the B2 phase is an intrinsically brittle phase. Under the action of external forces during service, the alloy will deform. Since there are more slip systems in the γ phase and they are easy to be activated, the deformation of the alloy is mainly completed by the γ phase. However, the dislocation slip systems in the B2 phase are difficult to be activated. Therefore, during deformation, the massive B2 phase and γ phase at the interfaces of the lamellar clusters are not coordinated in deformation, which is likely to cause voids and cracks to initiate here, and then lead to the fracture and failure of the alloy. Therefore, effectively avoiding or delaying the formation and propagation of cracks at the B2 / γ phase interfaces has become one of the main ways to improve the properties of near-lamellar structured TiAl alloys.

[0004] Currently, the main process for improving the properties of TiAl alloys is to add alloying elements. Insoluble alloying elements will precipitate in the form of a second phase to play a second-phase strengthening role, which can effectively pin dislocations and hinder crack propagation. However, it is difficult to control the specific distribution position of the strengthening phase in the microstructure, and it is difficult to accurately obtain the strengthening phase that precipitates at the B2 / γ phase interface. Therefore, the addition of most alloying elements is difficult to play a role in hindering crack nucleation and propagation at the B2 / γ phase interface. The discovery of the Ti2Al phase provides the possibility for the precipitation of a precipitated phase at the B2 / γ phase interface. The Ti2Al phase is an unstable intermediate phase of the α2→γ phase transformation. It is mainly induced under high temperature or stress, and it is a brittle phase that can play a role in hindering dislocation movement. If it can precipitate at the B2 / γ phase interface, it can effectively relieve the stress concentration at the phase interface and play a role in hindering crack propagation. However, in current research, the Ti2Al phase has only been observed to precipitate in the form of slender strips at the α2 / γ lamellar interface or inside the lamellae in the microstructure after creep and thermal exposure, and the phenomenon of the Ti2Al phase precipitating at the B2 / γ phase interface has rarely been reported. Therefore, developing a reasonable process to induce the precipitation of the Ti2Al phase at the massive B2 / γ phase interface is of significant engineering significance for improving the properties of the alloy. Summary of the Invention

[0005] The present invention provides a cyclic creep deformation method for inducing the selective precipitation of the Ti2Al phase in order to solve the technical problem that it is currently difficult to obtain the strengthening phase Ti2Al phase that precipitates at the B2 / γ phase interface.

[0006] The present invention provides a cyclic creep deformation process with a specific waveform load. By maintaining a certain time at the peak stress and the valley stress respectively, the Ti2Al phase is effectively induced to selectively precipitate at the B2 / γ phase interface. First, a high-niobium TiAl alloy with a near-lamellar structure is prepared; then, a cyclic creep deformation experiment is carried out on the alloy, and thus the Ti2Al phase is effectively induced to selectively precipitate at the B2 / γ phase interface.

[0007] A cyclic creep deformation method for inducing the selective precipitation of the Ti2Al phase is specifically carried out according to the following steps:

[0008] I. Preparation of raw materials: Weigh the raw materials according to the elemental mass percentage of 41% - 49% for Al, 6% - 9% for Nb, Mo ≤ 2%, Cr ≤ 2%, 0.1% - 0.8% for C, and the balance for Ti. The raw materials include pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, pure Cr grains, and C powder;

[0009] II. Melting

[0010] Alcohol cleaning: First, place the pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, and pure Cr grains in an ultrasonic cleaner for cleaning to remove surface impurities;

[0011] Preheating treatment: Put the cleaned pure titanium rod, pure Al block, Al-Mo master alloy, Al-Nb master alloy and pure Cr particles into an oven for preheating.

[0012] Loading: Sequentially put the preheated pure titanium rod, pure Al block, Al-Mo master alloy, Al-Nb master alloy and pure Cr particles into the copper crucible of a water-cooled copper crucible vacuum induction skull melting furnace. Wrap C powder with Al foil paper and put it into the secondary feeding hopper.

[0013] Vacuum pumping treatment: When the vacuum degree in the furnace reaches below 5 Pa, fill it with argon until the pressure in the furnace reaches 800 Pa, and repeat this process many times to remove air.

[0014] Heating and melting: The initial heating power is 30 - 55 kW. When the pure titanium rod melts, increase the power to 60 - 95 kW. After the raw materials are completely melted, conduct electromagnetic stirring. Then reduce the power for secondary feeding and add the C powder wrapped with Al foil paper. Increase the power to 60 - 95 kW and maintain for 15 - 25 min, while conducting electromagnetic stirring for 5 - 10 min to obtain an alloy melt.

[0015] Pour the alloy melt into a mold, take it out after cooling to room temperature to obtain a high-niobium TiAl alloy ingot.

[0016] III. Homogenization annealing treatment: Keep the high-niobium TiAl alloy ingot at 935 - 975 °C for 25 - 40 h, and then cool it to room temperature in the furnace to obtain a as-cast high-niobium TiAl alloy.

[0017] IV. Cyclic creep: ① Prepare a creep specimen from the as-cast high-niobium TiAl alloy and hang the clamping ends on the upper and lower sides of the creep specimen on an electronic creep testing machine. ② Apply a preload to fix the creep specimen. ③ Fix three thermocouples on the upper clamping end, lower clamping end and the area near the middle of the creep specimen respectively to monitor the temperature in real time. ④ Close the heating furnace and start heating up to the creep temperature of 750 - 850 °C and keep it for 25 - 55 min. ⑤ Load at a rate of 95 - 300 N / s to the peak stress of 250 - 400 MPa and hold at the peak stress for 5 - 20 min. Then unload at a rate of 95 - 300 N / s to the valley stress of 50 - 120 MPa and hold at the valley stress for 5 - 20 min. ⑥ Repeat step ⑤ for many times until the creep specimen fractures. ⑦ Cool it to room temperature in the furnace to complete.

[0018] Furthermore, the purity of the pure titanium rod described in Step 1 > 99.9 wt.%, the purity of the pure Al block > 99.9 wt.%, the Mo content in the Al-Mo master alloy is 50.5 wt.%, the Nb content in the Al-Nb master alloy is 52.4 wt.%, and the purity of the pure Cr particles > 99.9 wt.%.

[0019] Furthermore, in Step 2, the preheating temperature is controlled at 150 - 350 °C, and the preheating time is 25 - 55 min.

[0020] Furthermore, after the raw materials in Step 2 are completely melted, the electromagnetic stirring speed is controlled at 500 - 1000 rpm, and stirring is carried out for 5 - 10 min.

[0021] Furthermore, before the secondary feeding in Step 2, the power is reduced to 20 - 50 kW.

[0022] Furthermore, in Step 3, heat preservation is carried out at 940 - 970 °C for 30 - 40 h.

[0023] Furthermore, for the creep specimen in Step 4, the gauge length is 10 mm, the width is 5 mm, and the thickness is 2 mm.

[0024] Furthermore, in Step 4, the applied preload is controlled at 200 - 350 N.

[0025] Furthermore, in Step 4, an RDL-100 electronic creep testing machine is used.

[0026] Furthermore, in Step 4, the temperature is increased at a rate of 25 - 50 °C / min to reach the creep temperature.

[0027] Advantages of the present invention:

[0028] (1) The present invention successfully prepares a high-niobium TiAl alloy with a near-lamellar structure by using a vacuum induction melting process. Based on the secondary feeding of C powder and a long-time electromagnetic stirring, a TiAl alloy ingot with high tissue uniformity is obtained.

[0029] (2) The present invention proposes a cyclic creep deformation method in the form of a trapezoidal wave load. By using reasonable peak and valley stress magnitudes and holding times, the selective precipitation of Ti2Al phase at the B2 / γ phase interface is effectively induced, and the precipitated Ti2Al phase can effectively pin dislocations and relieve the local stress concentration at the B2 / γ phase interface. In addition, this cyclic creep deformation method also activates the dislocation slip system inside the B2 phase, improves the deformation ability of the brittle B2 phase, and promotes the coordinated deformation between the B2 phase and the γ phase.

[0030] (3) The cyclic creep deformation process proposed by the present invention to induce the selective precipitation of Ti2Al phase at the B2 / γ phase interface is simple in operation and low in cost, which can provide new ideas for the research field of regulating the precipitation of reinforcement phases at specific positions, and promote the development of high-performance TiAl alloys.

[0031] The present invention is used to obtain high-performance TiAl alloys. Description of the Drawings

[0032] Figure 1 Microstructure photographs of the as-cast high-niobium TiAl alloy prepared in Example 1, where Fig. (a) is the near-lamellar microstructure morphology diagram, and Fig. (b) is the morphology diagram of massive B2 and γ phases at the lamellar colony interface;

[0033] Figure 2 Curves related to the cyclic creep deformation of the as-cast high-niobium TiAl alloy in Example 1, where Fig. (a) is the stress waveform curve of cyclic creep, Fig. (b) is the creep deformation curve, and Fig. (c) is the partial enlarged view of the cyclic creep deformation curve in Fig. (b);

[0034] Figure 3 Deformed microstructure diagram of the as-cast high-niobium TiAl alloy after cyclic creep deformation in Example 1. Fig. (a) is the microstructure diagram of the Ti2Al phase precipitated at the B2 / γ phase interface, and Fig. (b) is the diffraction spot diagram of the Ti2Al phase. Detailed Embodiments

[0035] Detailed Embodiment 1: A cyclic creep deformation method for inducing the selective precipitation of Ti2Al phase is carried out according to the following steps:

[0036] I. Preparation of raw materials: Weigh the raw materials according to the elemental mass percentage of Al being 41% - 49%, Nb being 6% - 9%, Mo ≤ 2%, Cr ≤ 2%, C being 0.1% - 0.8% and the balance being Ti. The raw materials include pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, pure Cr grains and C powder;

[0037] II. Melting

[0038] Alcohol cleaning: First, place the pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys and pure Cr grains in an ultrasonic cleaning machine for cleaning to remove surface impurities;

[0039] Preheat treatment: Put the cleaned pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys and pure Cr grains into an oven for preheating;

[0040] Feeding: The preheated pure titanium rod, pure Al block, Al-Mo master alloy, Al-Nb master alloy, and pure Cr particles are sequentially placed into the copper crucible of the vacuum induction skull melting furnace with water-cooled copper crucible. The C powder is wrapped with Al foil paper and placed into the secondary feeding hopper.

[0041] Vacuum pumping treatment: When the vacuum degree in the furnace reaches below 5 Pa, argon is filled until the pressure in the furnace reaches 800 Pa, and this is repeated multiple times to remove air.

[0042] Heating and melting: The initial heating power is 30 - 55 kW. When the pure titanium rod melts, the power is increased to 60 - 95 kW. After the raw materials are completely melted, electromagnetic stirring is carried out. Then the power is reduced for secondary feeding, and the C powder wrapped with Al foil paper is added. The power is increased to 60 - 95 kW and maintained for 15 - 25 min, while electromagnetic stirring is carried out for 5 - 10 min to obtain the alloy melt.

[0043] The alloy melt is poured into the mold, taken out after cooling to room temperature, and a high-niobium TiAl alloy ingot is obtained.

[0044] III. Homogenization annealing treatment: The high-niobium TiAl alloy ingot is held at 935 - 975 °C for 25 - 40 h, and then cooled to room temperature with the furnace to obtain the as-cast high-niobium TiAl alloy.

[0045] IV. Cyclic creep: ① Prepare the creep specimen from the as-cast high-niobium TiAl alloy, and hang the clamping ends on the upper and lower sides of the creep specimen on the electronic creep testing machine. ② Apply a preload to fix the creep specimen. ③ Fix three thermocouples on the upper clamping end, lower clamping end, and the area near the middle of the creep specimen respectively to monitor the temperature in real time. ④ Close the heating furnace and start heating up to the creep temperature of 750 - 850 °C, and hold for 25 - 55 min. ⑤ Load at a rate of 95 - 300 N / s to the peak stress of 250 - 400 MPa, and hold at the peak stress for 5 - 20 min. Then unload at a rate of 95 - 300 N / s to the valley stress of 50 - 120 MPa, and hold at the valley stress for 5 - 20 min. ⑥ Repeat step ⑤ multiple times until the creep specimen fractures. ⑦ Cool to room temperature with the furnace to complete.

[0046] Specific embodiment 2: The difference between this embodiment and specific embodiment 1 is that the purity of the pure titanium rod described in step 1 > 99.9 wt.%, the purity of the pure Al block > 99.9 wt.%, the Mo content in the Al-Mo master alloy is 50.5 wt.%, the Nb content in the Al-Nb master alloy is 52.4 wt.%, and the purity of the pure Cr particles > 99.9 wt.%. Others are the same as specific embodiment 1.

[0047] Specific Embodiment 3: The difference between this embodiment and Specific Embodiment 1 or 2 is that in Step 2, the preheating temperature is controlled at 150 - 350°C and the preheating time is 25 - 55 min. Others are the same as Specific Embodiment 1 or 2.

[0048] Specific Embodiment 4: The difference between this embodiment and any one of Specific Embodiments 1 to 3 is that after the raw materials are completely melted in Step 2, the electromagnetic stirring speed is controlled at 500 - 1000 rpm and stirred for 5 - 10 min. Others are the same as any one of Specific Embodiments 1 to 3.

[0049] Specific Embodiment 5: The difference between this embodiment and any one of Specific Embodiments 1 to 4 is that before the secondary feeding in Step 2, the power is reduced to 20 - 50 kW. Others are the same as any one of Specific Embodiments 1 to 4.

[0050] Specific Embodiment 6: The difference between this embodiment and any one of Specific Embodiments 1 to 5 is that in Step 3, it is heat - insulated at 940 - 970°C for 30 - 40 h. Others are the same as any one of Specific Embodiments 1 to 5.

[0051] Specific Embodiment 7: The difference between this embodiment and any one of Specific Embodiments 1 to 6 is that in Step 4, the gage length of the creep specimen is 10 mm, the width is 5 mm, and the thickness is 2 mm. Others are the same as any one of Specific Embodiments 1 to 6.

[0052] Specific Embodiment 8: The difference between this embodiment and any one of Specific Embodiments 1 to 7 is that in Step 4, the applied pre - load is controlled at 200 - 350 N. Others are the same as any one of Specific Embodiments 1 to 7.

[0053] Specific Embodiment 9: The difference between this embodiment and any one of Specific Embodiments 1 to 8 is that in Step 4, an RDL - 100 electronic creep testing machine is used. Others are the same as any one of Specific Embodiments 1 to 8.

[0054] Specific Embodiment 10: The difference between this embodiment and any one of Specific Embodiments 1 to 9 is that in Step 4, the temperature is increased at a rate of 25 - 50°C / min to reach the creep temperature. Others are the same as any one of Specific Embodiments 1 to 9.

[0055] The content of the present invention is not limited to the content of the above - mentioned embodiments. The combination of one or several specific embodiments can also achieve the purpose of the invention.

[0056] Example 1:

[0057] A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase in this example is specifically carried out according to the following steps:

[0058] I. Raw material preparation: Weigh the raw materials according to the nominal composition of the high-niobium TiAl alloy, which is Ti-43Al-6Nb-1Mo-1Cr-0.5C (at.%). The raw materials include pure titanium rods, pure aluminum blocks, Al-Mo master alloy, Al-Nb master alloy, pure chromium granules, and C powder. The purity of the pure titanium rods is >99.9 wt.%, the purity of the pure aluminum blocks is >99.9 wt.%, the Mo content in the Al-Mo master alloy is 50.5 wt.%, the Nb content in the Al-Nb master alloy is 52.4 wt.%, and the purity of the pure chromium granules is >99.9 wt.%.

[0059] II. Melting

[0060] Alcohol cleaning: First, place the pure titanium rods, pure aluminum blocks, Al-Mo master alloy, Al-Nb master alloy, and pure chromium granules in an ultrasonic cleaning machine for cleaning to remove surface impurities.

[0061] Preheat treatment: Put the cleaned pure titanium rods, pure aluminum blocks, Al-Mo master alloy, Al-Nb master alloy, and pure chromium granules into an oven for preheating. The preheating temperature is 200 °C, and the preheating time is 40 min.[[ID=X]] [[ID=X]]

[0062] Charging: Put the preheated pure titanium rods, pure aluminum blocks, Al-Mo master alloy, Al-Nb master alloy, and pure chromium granules into the copper crucible in a water-cooled copper crucible vacuum induction skull melting furnace in sequence. Wrap the C powder with Al foil paper and put it into the secondary feeding hopper.

[0063] Vacuum pumping treatment: When the vacuum degree in the furnace reaches below 5 Pa, fill it with argon until the pressure in the furnace reaches 800 Pa, and repeat this three times to remove air.

[0064] Heating and melting: The initial heating power is 35 kW. When the pure titanium rods are melted, increase the power to 80 kW. After the raw materials are completely melted, conduct electromagnetic stirring, control the stirring speed at 800 rpm, and stir for 8 min. Then reduce the power to 35 kW, conduct secondary feeding, and add the C powder wrapped with Al foil paper. Increase the power to 80 kW and maintain it for 20 min, while conducting electromagnetic stirring for 8 min to obtain the alloy melt.

[0065] Pour the alloy melt into a mold, take it out after cooling to room temperature, and obtain a high-niobium TiAl alloy ingot.

[0066] III. Homogenization annealing treatment: Keep the high-niobium TiAl alloy ingot at 950 °C for 36 h, and then cool it to room temperature in the furnace to obtain the as-cast high-niobium TiAl alloy.

[0067] IV. Cyclic Creep: ① Prepare a creep specimen from the as-cast high-niobium TiAl alloy. The gauge length of the creep specimen is 10 mm, the width is 5 mm, and the thickness is 2 mm. Hang the clamping ends on the upper and lower sides of the creep specimen on an RDL-100 electronic creep testing machine; ② Apply a preload of 300 N to fix the creep specimen; ③ Fix three thermocouples on the upper clamping end, the lower clamping end, and the area near the middle of the creep specimen respectively to monitor the temperature in real time; ④ Close the heating furnace and start heating up at a rate of 40 °C / min until the creep temperature of 800 °C is reached, and keep it warm for 30 min; ⑤ Load at a rate of 200 N / s until the peak stress of 300 MPa is reached, and hold the load for 10 min at the peak stress; then unload at a rate of 200 N / s until the valley stress of 100 MPa is reached, and hold the load for 10 min at the valley stress; ⑥ Repeat step ⑤ multiple times until the creep specimen fractures; ⑦ Cool with the furnace to room temperature to complete.

[0068] Figure 1 Figure 4 is a microstructural photograph of the as-cast high-niobium TiAl alloy prepared in Example 1. Among them, Figure (a) is a morphology diagram of the near-lamellar structure, and Figure (b) is a morphology diagram of the blocky B2 and γ phases at the lamellar colony interface. According to the characterization results of the figure, it is found that the alloy structure is composed of α2 / γ lamellar colonies and blocky B2 and γ phases at the lamellar colony interface, which is a typical near-lamellar structure. In addition, based on Figure 1 (b) of the image, it can be found that no obvious precipitates are formed at the blocky B2 / γ phase interface.

[0069] Figure 2 Figure 10 is a curve diagram related to the cyclic creep deformation of the as-cast high-niobium TiAl alloy in Example 1. Among them, Figure (a) is a stress waveform curve diagram of cyclic creep, Figure (b) is a creep deformation curve diagram, and Figure (c) is a partial enlarged view of the cyclic creep deformation curve in Figure (b). It can be seen from Figure (a) that the as-cast high-niobium TiAl alloy cyclically deforms between the peak stress of 300 MPa and the valley stress of 100 MPa until the specimen fractures and stops. It can be seen from Figure (b) that within one cycle, with the application of the peak stress and the valley stress, the strain of the alloy also rises and falls accordingly.

[0070] Figure 3 Figure 14 is a deformation microstructure diagram of the as-cast high-niobium TiAl alloy after cyclic creep deformation. Among them, Figure (a) is a microstructure diagram of the Ti2Al phase precipitated at the B2 / γ phase interface, and Figure (b) is a diffraction spot diagram of the Ti2Al phase. It can be seen from the figure that after cyclic creep deformation, the Ti2Al phase precipitates at the blocky B2 / γ phase interface, and obvious dislocation pile-ups exist near it, indicating that it can effectively hinder the movement of dislocations. In addition, it can also be found from the figure that some dislocations appear inside the blocky B2 phase.

[0071] Based on the above detection results, it is confirmed that a cyclic creep deformation process of a specific load waveform implemented in the present invention effectively induces the selective precipitation of the Ti2Al phase at the B2 / γ phase interface.

Claims

1. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase, characterized in that The method is specifically carried out according to the following steps: I. Raw material preparation: Weigh raw materials according to the mass percentage of elements, where Al is 41% - 49%, Nb is 6% - 9%, Mo ≤ 2%, Cr ≤ 2%, C is 0.1% - 0.8%, and the balance is Ti. The raw materials include pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, pure Cr grains, and C powder; II. Melting Alcohol cleaning: First, place the pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, and pure Cr grains in an ultrasonic cleaner for cleaning to remove surface impurities; Preheating treatment: Put the cleaned pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, and pure Cr grains into an oven for preheating; Charging: Put the preheated pure titanium rods, pure Al blocks, Al-Mo master alloys, Al-Nb master alloys, and pure Cr grains into the copper crucible in a water-cooled copper crucible vacuum induction skull melting furnace in sequence. Wrap the C powder with Al foil paper and put it into the secondary feeding hopper; Vacuum pumping treatment: When the vacuum degree in the furnace reaches below 5 Pa, fill it with argon until the pressure in the furnace reaches 800 Pa, and repeat this several times to remove air; Heating and melting: The initial heating power is 30 - 55 kW. When the pure titanium rod melts, increase the power to 60 - 95 kW. After the raw materials are completely melted, conduct electromagnetic stirring; then reduce the power for secondary feeding and add the C powder wrapped with Al foil paper; increase the power to 60 - 95 kW, keep it for 15 - 25 min, and conduct electromagnetic stirring for 5 - 10 min simultaneously to obtain an alloy melt; Pour the alloy melt into a mold, take it out after cooling to room temperature, and obtain a high-niobium TiAl alloy ingot; III. Homogenization annealing treatment: Keep the high-niobium TiAl alloy ingot at 935 - 975 °C for 25 - 40 h, and then cool it to room temperature with the furnace to obtain a as-cast high-niobium TiAl alloy; IV. Cyclic creep: ① Prepare the creep specimens from the as-cast high-niobium TiAl alloy, and hang the clamping ends on the upper and lower sides of the creep specimens on an electronic creep testing machine; ② Apply a preload to fix the creep specimens; ③ Fix three thermocouples on the upper clamping end, lower clamping end, and the area near the middle of the creep specimen respectively to monitor the temperature in real time; ④ Close the heating furnace and start heating up to the creep temperature of 750 - 850 °C, and keep it for 25 - 55 min; ⑤ Load at a rate of 95 - 300 N / s to the peak stress of 250 - 400 MPa, and hold the load at the peak stress for 5 - 20 min; then unload at a rate of 95 - 300 N / s to the valley stress of 50 - 120 MPa, and hold the load at the valley stress for 5 - 20 min; ⑥ Repeat step ⑤ for multiple times until the creep specimen breaks; ⑦ Cool it to room temperature with the furnace to complete.

2. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that The purity of the pure titanium rod described in step I > 99.9 wt.%, the purity of the pure Al block > 99.9 wt.%, the Mo content in the Al-Mo master alloy is 50.5 wt.%, the Nb content in the Al-Nb master alloy is 52.4 wt.%, and the purity of the pure Cr grains > 99.9 wt.%.

3. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 2, control the preheating temperature at 150 - 350 °C and the preheating time at 25 - 55 min.

4. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that After the raw materials in Step 2 are completely melted, control the electromagnetic stirring speed at 500 - 1000 rpm and stir for 5 - 10 min.

5. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that Before the secondary feeding in Step 2, reduce the power to 20 - 50 kW.

6. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 3, keep the temperature at 940 - 970 °C for 30 - 40 h.

7. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 4, the gauge length of the creep specimen is 10 mm, the width is 5 mm, and the thickness is 2 mm.

8. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 4, control the applied preload at 200 - 350 N.

9. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 4, use an RDL-100 electronic creep testing machine.

10. A cyclic creep deformation method for inducing selective precipitation of Ti2Al phase according to claim 1, characterized in that In Step 4, increase the temperature at a rate of 25 - 50 °C / min to reach the creep temperature.

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