Method for strengthening and toughening of multi-stage ordered TiAl single crystal

Abstract

The application discloses a method for strengthening and toughening of multistage sequence structure TiAl single crystal, and belongs to the technical field of metal material strengthening and toughening. The application provides a method for strengthening and toughening of multistage sequence structure TiAl single crystal by hot pressing, and a multistage sequence structure TiAl single crystal with refined gamma phase is obtained by controlling temperature, pressure and holding time. The application provides a method for strengthening and toughening of multistage sequence structure TiAl single crystal by isothermal heat treatment, and a multistage sequence structure TiAl single crystal with refined alpha2 phase is obtained by controlling vacuum degree, temperature and holding time. The application provides a method for combining hot pressing and isothermal heat treatment, and a multistage sequence structure TiAl single crystal with full lamellar structure is obtained. The multistage sequence structure TiAl single crystal after the regulation has great improvement in mechanical properties, and the yield strength is 653-1006 MPa, and the elongation is 13.6-24.5%.

Description

Technical Field

[0001] This invention belongs to the field of metal material strengthening and toughening technology, and specifically relates to a process method for strengthening and toughening TiAl single crystals with multi-level ordered structure. Background Technology

[0002] In recent years, the aerospace technology field has developed rapidly, actively promoting the development of advanced aerospace materials in my country, which is crucial to national defense security, economic transformation, and future strategic planning. Given the excellent high-temperature mechanical properties of nickel-based superalloys, they are currently widely used in aerospace engines. Although nickel-based superalloys possess good high-temperature performance, their relatively high density (8.2–8.9 g / cm³) is a significant factor. 3 This would greatly increase the weight of the engine, and this problem has become a major obstacle to its vigorous development.

[0003] Hierarchical TiAl single crystals possess a fully lamellar structure with parallel phase interfaces and twin interfaces. They have a high initial melting temperature (1585℃) and a density of 3.9 g / cm³. 3 TiAl alloys, with a strength less than half that of nickel-based superalloys, are promising materials for aero-engines. Currently, TiAl-4822 alloy is being used by GE in the low-pressure turbines of their 747 and 787 aircraft, a practice that has yielded significant economic benefits. However, due to the high mechanical property requirements of aero-engines, the strength and ductility of TiAl alloys still lag behind those of nickel-based superalloys.

[0004] Therefore, TiAl single crystals cannot yet be widely used in engines. To further expand the application of TiAl single crystals, it is necessary to strengthen and regulate their toughness to meet more application requirements. Summary of the Invention

[0005] To address the shortcomings of existing technologies and solve the technical problem of low strength and ductility of TiAl single crystals, which cannot meet the material requirements for aero-engines, this invention aims to design and provide three methods for controlling the strengthening and toughening of multi-level ordered TiAl single crystals. These three methods—hot pressing, isothermal heat treatment, and a combination of both—can all improve the strength and toughness of TiAl single crystal materials. The third method, combining hot pressing and isothermal heat treatment, is the most effective, enabling the multi-level ordered TiAl single crystals to achieve full-layer refinement, thus meeting the higher mechanical performance requirements of aerospace engine materials.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] On one hand, the present invention provides a method for strengthening and toughening TiAl single crystals through hot pressing, comprising the following steps:

[0008] Weigh a multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a hot press, raise the temperature to 1050-1200℃ at a heating rate of 10-20℃ / min, gradually increase the pressure to 40-85MPa within 5-60min, hold it at the temperature for 5-20h, cool it to room temperature with the furnace, and take it out to obtain a multi-level ordered TiAl single crystal with refined γ phase.

[0009] The method for strengthening and toughening TiAl single crystals by hot pressing involves placing the blocky TiAl single crystal in a mold, and when the pressure is increased, the compression direction of the pressure is at 90° to the layers of the TiAl single crystal.

[0010] Secondly, the present invention provides a γ-phase refined hierarchical ordered TiAl single crystal prepared by the method described above.

[0011] Thirdly, the present invention provides a method for controlling the isothermal heat treatment to strengthen and toughen multi-level ordered TiAl single crystals, comprising the following steps:

[0012] Weigh out a multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a high-vacuum heat treatment furnace, and evacuate it to 10°C. - 4 After the temperature drops below Pa, the temperature is increased to 1250–1330℃ at a heating rate of 10–20℃ / min, and held for 5–24 hours. The temperature is then cooled to room temperature in the furnace, and the resulting TiAl single crystals with refined α2 phase are obtained.

[0013] The method for controlling the isothermal heat treatment to strengthen and toughen multi-level ordered TiAl single crystals, wherein the cooling rate is 10-20℃ / s.

[0014] Fourthly, the present invention provides a multi-level ordered TiAl single crystal with refined α2 phase prepared by the method described above.

[0015] Fifthly, the present invention provides a method for controlling the multi-level ordered structure of TiAl single crystals, comprising the following steps:

[0016] (1) Weigh the multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a hot press, raise the temperature to 1050-1200℃ at a heating rate of 10-20℃ / min, gradually increase the pressure to 40-85MPa in 5-60min, keep it at the temperature for 5-20h, cool it to room temperature with the furnace, and take it out to obtain a multi-level ordered TiAl single crystal with refined γ phase;

[0017] (2) The above-mentioned γ-phase refined hierarchical TiAl single crystal was placed in a high vacuum heat treatment furnace and evacuated to 100°C. -4After the temperature drops below Pa, the temperature is increased to 1250–1330℃ at a heating rate of 10–20℃ / min, and held for 5–24 hours. The temperature is then cooled to room temperature in the furnace, and the resulting TiAl single crystal has a multi-level ordered structure with refined layers.

[0018] In the aforementioned control method, the blocky multi-level ordered TiAl single crystal in step (1) is placed in a mold, and when the pressure is increased, the compression direction of the pressure is at 90° to the layers of the multi-level ordered TiAl single crystal.

[0019] The cooling rate described in step (2) is 10 to 20 °C / s.

[0020] In a sixth aspect, the present invention provides a multi-level ordered TiAl single crystal with fully layered refinement prepared by the aforementioned control method.

[0021] In a seventh aspect, the present invention provides the application of the γ-phase refined hierarchical ordered TiAl single crystal, the α2-phase refined hierarchical ordered TiAl single crystal, or the fully lamellar refined hierarchical ordered TiAl single crystal as aerospace materials with strong plasticity.

[0022] In the first slow hot-pressing control method of this invention, under the action of temperature and pressure, the twin interface (γ / γ) in the γ phase... T The 1 / 6 <11-2> Shockley partial dislocations on both sides slide across the crystal in opposite directions on the {111} plane, which leads to the transformation of FCC to HCP structure at the twin interface. This structural transformation is called stress-induced phase transition. After the phase transition, the average lamellar width of the hierarchical TiAl single crystal will decrease, which is also the reason for its strength improvement.

[0023] In the second isothermal heat treatment control method of this invention, after the temperature is raised to the isothermal phase transition range of TiAl single crystal, the α2 phase in the TiAl single crystal transforms into a disordered α phase. Subsequently, during the cooling process, by controlling the cooling rate, the α phase decomposes into the α2 phase and the secondary γ phase. Through isothermal phase transition control, the final multi-level ordered TiAl single crystal contains the primary γ phase, the α2 phase, and the secondary γ phase, successfully refining the lamellar structure and improving its strength.

[0024] In the third method of the present invention, which combines slow hot pressing control and isothermal heat treatment control, the γ phase is first refined, then the α2 phase is refined, and finally, through the combined control method of the two, a multi-level ordered TiAl single crystal with full-layer refinement is successfully obtained.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention provides a method for strengthening and toughening TiAl single crystals with a multi-level ordered structure. The multi-level ordered TiAl single crystals obtained by the first method after slow hot pressing are subjected to 10°C at room temperature.-4 s -1 At the specified tensile rate, the tensile strength is 653–701 MPa, and the elongation is 11.7–23.5%. The hierarchical TiAl single crystal obtained after the second type of isothermal heat treatment exhibits a tensile strength of 653–701 MPa and an elongation of 11.7–23.5% at room temperature. -4 s -1 At the specified tensile rate, the tensile strength ranged from 653 to 883 MPa, and the elongation ranged from 7.4% to 22.9%. The fully lamellar, multi-level ordered TiAl single crystal obtained by the third method, combining hot pressing and isothermal heat treatment, exhibited a tensile strength of 653–883 MPa and an elongation of 7.4–22.9% at room temperature. -4 s -1 At the specified stretching rate, the tensile strength was 653–1006 MPa, and the elongation was 13.6–24.5%, indicating that the three methods for strengthening and toughening TiAl single crystals according to the present invention are all effective. Attached Figure Description

[0027] Figure 1 The images show the microstructure of TiAl single crystals before and after hot pressing at 1200℃ and 55MPa for 5 hours in Example 1. (a) shows the microstructure of TiAl single crystals before hot pressing; (b) shows the microstructure of TiAl single crystals after hot pressing; (c) shows the average width of the γ-phase layer of TiAl single crystals before hot pressing; and (d) shows the average width of the γ-phase layer of TiAl single crystals after hot pressing.

[0028] Figure 2 The figures show the room temperature tensile curves of TiAl single crystals subjected to different toughening processes in Examples 1, 4, and 7.

[0029] Figure 3 The images show the microstructure of TiAl single crystals before and after hot pressing at 1000℃ and 55MPa for 5 hours in Comparative Example 1. (a) shows the microstructure of TiAl single crystals before hot pressing; (b) shows the microstructure of TiAl single crystals after hot pressing; (c) shows the average width of the γ-phase layer of TiAl single crystals before hot pressing; and (d) shows the average width of the γ-phase layer of TiAl single crystals after hot pressing.

[0030] Figure 4 The images show the microstructure of the samples before and after isothermal heat treatment at 1310℃ for 5 hours in Example 4. (a) is the morphology of the sample before isothermal heat treatment; (b) is the morphology of the sample after isothermal heat treatment; (c) is a statistical diagram of the average width of the α2 phase layer of the sample before isothermal heat treatment; and (d) is a statistical diagram of the average width of the α2 phase layer of the sample before and after isothermal heat treatment at 1310℃ for 5 hours.

[0031] Figure 5The images show the morphology of TiAl single crystals before and after hot pressing at 1200℃ and 55MPa for 5 hours and isothermal heat treatment at 1310℃ for 5 hours in Example 7. (a) is the morphology of the sample before conditioning; (b) is the morphology of the fully refined sample after conditioning; (c) is the statistical diagram of the average width of the γ phase layer before conditioning; and (d) is the statistical diagram of the average width of the γ phase layer of the fully refined sample after conditioning. Detailed Implementation

[0032] The following disclosure provides many different implementations or examples for carrying out different structures of the present invention. To simplify the disclosure of the present invention, the method steps of specific examples are described below. Of course, these are merely examples and are not intended to limit the present invention.

[0033] Example 1:

[0034] Multi-level ordered TiAl single crystal samples (average width of γ-phase lamellar layer 1.42 μm) were prepared into block samples using an electric discharge wire cutter and placed in a hot press. The temperature was then increased to 1200 °C at a rate of 10 °C / min, and the pressure was gradually increased to 55 MPa over 30 min. The samples were held at 1200 °C for 5 h. After the holding period, the samples were cooled to room temperature in the furnace, the power was cut off, and the TiAl single crystal samples were removed from the hot press. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, as shown below. Figure 1 The images show the microstructure of TiAl single crystals before and after hot-pressing. It can be seen that the average width of the γ phase in the TiAl single crystal sample after hot pressing is 611.8 nm, which is significantly reduced compared with the average width of the γ phase laminations in the parent material (1.42 μm).

[0035] The tensile strength and elongation of the TiAl single crystal samples after the above-mentioned regulation were tested. Specifically:

[0036] This invention utilizes an EHF-010-OA fatigue tester manufactured by Shimadzu Corporation of Japan for room temperature tensile testing of TiAl single crystals. The tensile specimens are machined into bone-bar shapes using diamond wire cutting, with a 0° orientation in the tensile direction. The specimen dimensions are 5mm x 8mm, and the gauge length is 1mm x 2mm. To remove surface stress, the specimens are ground with 400# to 3000# sandpaper, followed by mechanical polishing and finally electrolytic polishing. The specimens are then mounted on the fatigue tester fixtures for room temperature tensile testing. To obtain accurate tensile data, samples with different parameters are subjected to at least three tensile tests, and the average of the three data points is selected as representative.

[0037] The results are as follows Figure 2 As shown, the structure of the TiAl single crystal sample regulated by the method in Example 1 is as follows: at room temperature for 10...-4 s -1 At the specified tensile rate, the tensile strength is 653–701 MPa, and the elongation is 11.7–23.5%.

[0038] Example 2:

[0039] A multi-level ordered TiAl single crystal sample (average width of γ-phase lamellar layer 1.42 μm) was prepared into a bulk sample using an electrical discharge wire cutter and placed in a hot press. The temperature was then increased to 1200 °C at a rate of 15 °C / min, and the pressure was gradually increased to 40 MPa over 5 min. The sample was held at 1200 °C for 10 h. After the holding period, the sample was cooled to room temperature in the furnace, the power was cut off, and the TiAl single crystal sample was removed from the hot press. The final regulated TiAl single crystal sample retained its two-phase lamellar structure. The average width of the γ-phase was 620.4 nm, successfully achieving effective control of the γ-phase width.

[0040] Example 3:

[0041] A multi-level ordered TiAl single crystal sample (average width of γ-phase lamellar layer 1.42 μm) was prepared into a bulk sample using an electrical discharge wire cutter and placed in a hot press. The temperature was then increased to 1050 °C at a rate of 20 °C / min, and the pressure was gradually increased to 85 MPa over 60 min. The sample was held at 1050 °C for 20 h. After the holding period, the sample was cooled to room temperature in the furnace, the power was cut off, and the TiAl single crystal sample was removed from the hot press. The final regulated TiAl single crystal sample retained its two-phase lamellar structure. The average width of the γ-phase was 616.3 nm, successfully achieving effective control of the γ-phase width.

[0042] Comparative Example 1:

[0043] Multi-level ordered TiAl single crystal samples (average width of γ-phase lamellar layer 1.42 μm) were prepared into block samples using an electric discharge wire cutter and placed in a hot press. The temperature was then increased to 1000 °C at a rate of 10 °C / min, followed by a pressure increase to 55 MPa. The samples were held at 1000 °C for 5 hours. After the holding period, the samples were cooled to room temperature in the furnace, the power was cut off, and the TiAl single crystal samples were removed from the hot press. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, as shown below. Figure 3 The image shows the microstructure of TiAl single crystals before and after hot pressing. The average width of the γ phase is 1.35 μm, which is not much different from the average width of the γ phase laminations in the parent TiAl single crystal sample. This may be because the temperature was too low, and the width of the γ phase could not be effectively controlled.

[0044] Example 4:

[0045] The multi-level ordered TiAl single crystal sample (average width of α2 phase layer 116.82 nm) was prepared into a bulk sample using an electrical discharge wire cutter. It was then placed in a high-vacuum heat treatment furnace, where the vacuum level was evacuated to 1000 nm using a mechanical pump and a molecular pump. -4 Below Pa. Then, the temperature was increased to 1310℃ at a rate of 10℃ / min, and held at 1310℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final conditioned TiAl single crystal sample still maintained a two-phase lamellar structure, as shown... Figure 4 The image shows the microstructure of TiAl single crystals before and after isothermal heat treatment. The average width of the α2 phase is 70.59 nm, which is 39.57% less than that of the parent material, thus successfully refining the width of the α2 phase.

[0046] The tensile strength and elongation of the modified TiAl single crystal sample were tested using the same methods as in Example 1. The results are as follows: Figure 2 As shown, the multi-level ordered TiAl single crystal after isothermal heat treatment regulation exhibits a temperature of 10°C at room temperature. -4 s -1 At the specified tensile rate, the tensile strength is 653–883 MPa, and the elongation is 7.4–22.9%.

[0047] Example 5:

[0048] The multi-level ordered TiAl single crystal sample (average width of α2 phase layer 116.82 nm) was prepared into a bulk sample using an electrical discharge wire cutter. It was then placed in a high-vacuum heat treatment furnace, where the vacuum level was evacuated to 1000 nm using a mechanical pump and a molecular pump. -4 Below Pa. The temperature was then increased to 1250℃ at a rate of 15℃ / min, and held at 1250℃ for 24 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, with the α2 phase having an average width of 72.31 nm, successfully achieving effective refinement of the α2 phase width.

[0049] Example 6:

[0050] The multi-level ordered TiAl single crystal sample (average width of α2 phase layer 116.82 nm) was prepared into a bulk sample using an electrical discharge wire cutter. It was then placed in a high-vacuum heat treatment furnace, where the vacuum level was evacuated to 1000 nm using a mechanical pump and a molecular pump. -4Below Pa. The temperature was then increased to 1330℃ at a rate of 20℃ / min, and held at 1330℃ for 15 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, with the α2 phase having an average width of 70.12 nm, successfully achieving effective refinement of the α2 phase width.

[0051] Comparative Example 2:

[0052] The multi-level ordered TiAl single crystal sample (average width of α2 phase layer 116.82 nm) was prepared into a bulk sample using an electrical discharge wire cutter. It was then placed in a high-vacuum heat treatment furnace, where the vacuum level was evacuated to 1000 nm using a mechanical pump and a molecular pump. -4 Below Pa. The temperature was then increased to 1200℃ at a rate of 10℃ / min, and held at 1200℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final TiAl single crystal sample, after being regulated, still maintained a two-phase lamellar structure. Due to the excessively low temperature, effective regulation of the α2 phase width could not be achieved.

[0053] Example 7:

[0054] The multi-level ordered TiAl single crystal sample was prepared into a block shape using an electrical discharge wire cutter, and then placed in a hot press. The temperature was then raised to 1200℃ at a rate of 10℃ / min, and the pressure was gradually increased to 55MPa over 30 minutes. The sample was held at 1200℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, and then the power was cut off. The TiAl single crystal sample was then removed from the heat treatment furnace. Subsequently, it was placed in a high-vacuum heat treatment furnace, and the vacuum was evacuated to 100 kJ / m³ using a mechanical pump and a molecular pump. - 4 Below Pa. Then, the temperature was increased to 1310℃ at a rate of 10℃ / min, and held at 1310℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final conditioned TiAl single crystal sample still maintained a two-phase lamellar structure, as shown... Figure 5 The morphology diagrams and γ phase layer width statistics of TiAl single crystals before and after the method of combining hot pressing and isothermal heat treatment are shown. It can be seen that the average width of the γ phase layer is refined from 1.42 μm in the growth state to 65.53 nm, and the widths of the two phase layers are uniform, thus successfully achieving full layer refinement.

[0055] The tensile strength and elongation of the modified TiAl single crystal sample were tested using the same methods as in Example 1. The results are as follows: Figure 2As shown, the fully lamellar refined hierarchical TiAl single crystal obtained after regulation exhibits a 10°C temperature at room temperature. -4 s -1 At the specified tensile rate, the tensile strength is 653–1006 MPa; the elongation is 13.6–24.5%.

[0056] Example 8:

[0057] The multi-level ordered TiAl single crystal sample was prepared into a block shape using an electrical discharge wire cutter. It was then placed in a hot press, and the temperature was initially increased to 1200℃ at a rate of 15℃ / min. The pressure was then gradually increased to 40 MPa over 5 minutes, and the sample was held at 1200℃ for 10 hours. After the holding period, the sample was cooled to room temperature in the furnace, and then the power was cut off. The TiAl single crystal sample was then removed from the heat treatment furnace. Subsequently, it was placed in a high-vacuum heat treatment furnace, and the vacuum was evacuated to 10 MPa using a mechanical pump and a molecular pump. - 4 Below Pa. The temperature was then increased to 1250℃ at a rate of 15℃ / min, and held at 1250℃ for 24 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, with an average γ-phase width of 68.53 nm, successfully achieving full lamellar refinement.

[0058] Example 9:

[0059] The multi-level ordered TiAl single crystal sample was prepared into a block shape using an electrical discharge wire cutter, and then placed in a hot press. The temperature was then raised to 1050℃ at a rate of 20℃ / min, and the pressure was gradually increased to 85MPa over 60 minutes. The sample was held at 1050℃ for 20 hours. After the holding period, the sample was cooled to room temperature in the furnace, and then the power was cut off. The TiAl single crystal sample was then removed from the heat treatment furnace. Subsequently, it was placed in a high-vacuum heat treatment furnace, and the vacuum was evacuated to 100 kJ / m³ using a mechanical pump and a molecular pump. - 4 Below Pa. The temperature was then increased to 1330℃ at a rate of 20℃ / min, and held at 1330℃ for 15 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final regulated TiAl single crystal sample still maintained a two-phase lamellar structure, with an average γ-phase width of 67.37 nm, successfully achieving full lamellar refinement.

[0060] Comparative Example 3:

[0061] The multi-level ordered TiAl single crystal sample was prepared into a block shape using an electrical discharge wire cutter. It was then placed in a hot press, and the temperature was gradually increased to 1150℃ at a rate of 10℃ / min. The pressure was then increased to 55 MPa, and the sample was held at 1150℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, and then the power was cut off. The TiAl single crystal sample was then removed from the heat treatment furnace. Subsequently, it was placed in a high-vacuum heat treatment furnace, and the vacuum was evacuated to 100 kJ / m³ using a mechanical pump and a molecular pump. -4 Below Pa. The temperature was then increased to 1350℃ at a rate of 10℃ / min, and held at 1350℃ for 5 hours. After the holding period, the sample was cooled to room temperature in the furnace, then the power was cut off, and the TiAl single crystal sample was removed from the heat treatment furnace. The final TiAl single crystal sample showed recrystallization, and the full-layer refinement was not successfully controlled.

[0062] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art. The specification and examples are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0063] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for strengthening and toughening TiAl single crystals through hot pressing, characterized in that, Includes the following steps: Weigh a multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a hot press, raise the temperature to 1050-1200 ℃ at a heating rate of 10-20 ℃ / min, gradually increase the pressure to 40-85 MPa within 5-60 min, hold it at that temperature for 5-20 h, cool it to room temperature with the furnace, and take it out to obtain a multi-level ordered TiAl single crystal with refined γ phase; place the block-shaped multi-level ordered TiAl single crystal in a mold, and when the pressure is increased, the compression direction of the pressure is at 90° with the layers of the multi-level ordered TiAl single crystal.

2. A γ-phase refined hierarchical TiAl single crystal prepared by the method as described in claim 1.

3. The application of the γ-phase refined hierarchical TiAl single crystal as described in claim 2 as a highly ductile aerospace material.

4. A method for controlling the isothermal heat treatment to strengthen and toughen multi-level ordered TiAl single crystals, characterized in that, Includes the following steps: Weigh out a multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a high-vacuum heat treatment furnace, and evacuate it to 10 °C. -4 After the temperature drops below Pa, it is increased to 1250-1330℃ at a heating rate of 10-20℃ / min, held for 5-24 h, cooled to room temperature in the furnace, and then removed to obtain a multi-level ordered TiAl single crystal with refined α2 phase; the cooling rate is 10-20℃ / s.

5. A multi-level ordered TiAl single crystal with refined α2 phase prepared by the method described in claim 4.

6. The application of the α2 phase refined hierarchical TiAl single crystal as described in claim 5 as a highly ductile aerospace material.

7. A method for controlling the multi-level ordered structure of TiAl single crystals, characterized in that, Includes the following steps: (1) Weigh the multi-level ordered TiAl single crystal sample, cut it into blocks, place it in a hot press, raise the temperature to 1050~1200 ℃ at a heating rate of 10~20 ℃ / min, gradually increase the pressure to 40~85 MPa in 5~60 min, keep it at the temperature for 5~20 h, cool it to room temperature with the furnace, and take it out to obtain a multi-level ordered TiAl single crystal with refined γ phase; (2) The above-mentioned γ-phase refined hierarchical TiAl single crystal was placed in a high vacuum heat treatment furnace and evacuated to 1000 ℃. -4 After Pa, the temperature is increased to 1250~1330℃ at a heating rate of 10~20℃ / min, and held for 5~24 h. The temperature is then cooled to room temperature in the furnace, and the resulting TiAl single crystal with a multi-level ordered structure and refined layers is obtained. In step (1), the blocky multi-level ordered TiAl single crystal is placed in a mold. When the pressure is increased, the compression direction of the pressure is 90° with the layers of the multi-level ordered TiAl single crystal. The cooling rate described in step (2) is 10~20 ℃ / s.

8. A multi-level ordered TiAl single crystal with fully layered refinement prepared by the control method described in claim 7.

9. The application of the fully lamellar refined multi-level ordered TiAl single crystal as described in claim 8 as a highly ductile aerospace material.

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