Hot working method of fine grain TiAl alloy

Abstract

The invention discloses a hot working method of a fine grain TiAl alloy. According to the method, the TiAl alloy cast ingot with uniform components obtained through vacuum induction melting is subjected to multi-pass hot working, so that the hot working structure uniformity of the TiAl alloy is improved, and a fine grain structure is obtained; in the multi-pass hot working process, the hot working temperature is controlled to be 1150-1250 DEG C, the strain rate is controlled to be 0.001-1 s <-1 >, the single-pass deformation amount is 20%-30%, the heat preservation time between the passes is 10-120 s, and the total deformation amount of all the passes does not exceed 60%. The TiAl alloy blank prepared through the method is good in structure uniformity, the grain size ranges from 20 micrometers to 30 micrometers, the problems that a TiAl alloy hot working structure is poor in uniformity and thick are solved, meanwhile, the technology is simplified, and cracking in the hot working process is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of metal material processing, and in particular relates to a fine-grained TiAl alloy thermal processing method. Background Art

[0002] TiAl alloy is an excellent high-temperature, lightweight structural material. Compared with titanium and nickel-based alloys, it boasts higher specific strength and modulus, showing promising applications in aerospace and has already been used in the rear two-stage turbine blades of aircraft engines. However, its intrinsic brittleness directly limits its widespread application, resulting in poor hot working properties, a narrow hot working window (only 50°C), and susceptibility to cracking during hot working, leading to material scrap. A series of research efforts have been conducted both domestically and internationally to address this issue, addressing its poor hot working properties through alloy composition design, hot isostatic pressing (HIP), canning design, and hot working process optimization, achieving considerable progress. For example, the TNM alloy developed exhibits relatively excellent hot working properties, and TiAl alloy sheets have been produced by combining powder metallurgy with traditional forging and rolling. Deformation temperature and deformation rate are two key parameters during hot working, and they are often strictly controlled. To avoid temperature drops during hot working, canning is often implemented to ensure a smooth hot working process, further increasing the number of TiAl alloy production steps and costs. Hot working often requires multiple passes and re-melting cycles to complete the entire process. How to obtain high-quality TiAl alloy forging billets is a key issue that urgently needs to be solved. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to address the shortcomings of the above-mentioned existing technologies and provide a fine-grained TiAl alloy hot working method. By controlling the deformation amount and holding time of each pass during hot working, the dynamic recovery and dynamic recrystallization effects of the TiAl alloy are fully utilized, thereby improving the hot working performance of the TiAl alloy, avoiding cracking during hot working, and obtaining a uniform fine-grained structure. The present invention solves the problem of TiAl alloy being prone to cracking during hot working and improves the uniformity of the hot-worked structure.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0005] In a first aspect, the present invention provides a fine-grained TiAl alloy hot working method, which comprises the following steps: performing multi-pass hot working on a TiAl alloy ingot having uniform composition obtained by vacuum induction melting, thereby improving the uniformity of the hot working structure of the TiAl alloy and obtaining a fine-grained structure; during the multi-pass hot working process, the hot working temperature is controlled at 1150-1250°C, and the strain rate is controlled at 0.001-1s -1The deformation of a single pass is 20% to 30%, the holding time between passes is 10 to 120s, and the total deformation of all passes does not exceed 60%.

[0006] As a preferred embodiment of the first aspect, the chemical composition of the TiAl alloy is as follows in atomic percentage: Al: 43-48%; Nb: 0-8%; Cr: 0-2%; V: 0-3%; Mo: 0-2%, B≤0.3%, Re≤0.3%, and the rest is Ti.

[0007] As a preferred embodiment of the first aspect, the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re.

[0008] As a preferred embodiment of the first aspect above, the vacuum induction melting process is as follows: take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate the crucible and fill it with argon, then slowly load the current and keep it warm to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot.

[0009] As a preferred embodiment of the first aspect, during the vacuum induction melting process, the recorded current is 200 A and the holding time is 2 min.

[0010] As a preferred embodiment of the first aspect, the ingot obtained by the initial smelting needs to be subjected to vacuum induction melting again before being used for multiple hot working to improve uniformity.

[0011] As a preference of the first aspect above, in the multi-pass hot working process, the total number of hot working passes is 2 to 3 passes.

[0012] As a preferred embodiment of the first aspect, during the multi-pass hot working process, the total deformation of all passes is controlled to be 60%.

[0013] In a second aspect, the present invention provides a TiAl alloy billet obtained by the fine-grained TiAl alloy hot working method according to any one of the solutions of the first aspect.

[0014] As a preferred embodiment of the second aspect, the TiAl alloy billet has a fine-grained structure composed of equiaxed γ+B2 / β+α2, a grain size of 20 to 30 μm, and no individual coarse grains.

[0015] Compared with the prior art, the present invention has the following advantages:

[0016] 1. The present invention utilizes vacuum induction melted TiAl alloy ingots and uses multiple hot working passes to improve the uniformity of the TiAl alloy's hot working structure and obtain a fine-grained structure. This process can be implemented using conventional hydraulic press equipment. By controlling the distribution of deformation per pass and the dwell time between passes, and utilizing the principles of dynamic recrystallization and dynamic recovery, the hot working formability of the TiAl alloy is improved, resulting in a fine-grained structure.

[0017] 2. The present invention can achieve structural control by adjusting the total deformation and the reasonable distribution of the deformation per pass, and can also perform industrial-scale heat processing. The entire process is simple to operate and easy to implement, which enhances the application value of the present method. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a backscattered SEM image (1000×) of the TiAl alloy prepared in Example 1 of the present invention.

[0019] Figure 2 This is a backscattered SEM image (1000×) of the TiAl alloy prepared in Comparative Example 1 of the present invention.

[0020] Figure 3 is a backscattered SEM image (1000×) of the TiAl alloy prepared in Comparative Example 2 of the present invention.

[0021] Figure 4 This is a backscattered SEM image (1000×) of the TiAl alloy prepared in Example 2 of the present invention.

[0022] Figure 5 is a backscattered SEM image (1000×) of the TiAl alloy prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments.

[0024] The present invention provides a method for hot working of a fine-grained TiAl alloy, wherein the TiAl alloy ingot is subjected to vacuum induction melting, and the uniformly composed TiAl alloy ingot obtained by vacuum induction melting is subjected to multi-pass hot working to improve the uniformity of the hot working structure of the TiAl alloy and obtain a fine-grained structure. The present invention fully utilizes the dynamic recovery and dynamic recrystallization effects of the TiAl alloy through multi-pass hot working and controls the deformation amount and holding time of a single pass during the hot working process, thereby improving the hot working performance of the TiAl alloy, avoiding cracking during the hot working process, and obtaining a uniform fine-grained structure. Specifically, the key parameters that need to be controlled in the multi-pass hot working process of the present invention are as follows: the hot working temperature (i.e., the deformation temperature) is controlled to be 1150-1250°C, and the strain rate is controlled to be 0.001-1s -1The deformation of a single pass is 20% to 30%, the holding time between passes is 10 to 120s, and the total deformation of all passes does not exceed 60%.

[0025] The composition of the above-mentioned TiAl alloy is, by atomic percentage, Al: 43-48%; Nb: 0-8%; Cr: 0-2%; V: 0-3%; Mo: 0-2%, B ≤ 0.3%, Re ≤ 0.3%, and the remainder is Ti. In the embodiment of the present invention, the preferred TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re, but the composition of the TiAl alloy in other embodiments can also be optimized and adjusted according to actual conditions. By regulating the composition of the TiAl alloy, the alloy structure can be optimized, which is conducive to improving the hot working performance and obtaining a TiAl alloy with excellent hot working properties.

[0026] During the vacuum induction melting process, the TiAl alloy is prepared according to its chemical composition ratio. Ti is placed at the bottom of the crucible, followed by Al, and the remaining alloy components are placed at the top. The crucible is then placed in a vacuum induction melting furnace, evacuated, and filled with argon. A current is then slowly applied to 200A, held for 2 minutes to melt the alloy components, and then cooled to room temperature to produce an ingot. To ensure uniform composition of the alloy ingot, a secondary melting process is performed. This involves flipping the ingot from the first melting process and performing a second vacuum induction melting process, further improving the quality of the TiAl alloy ingot.

[0027] During the above-mentioned multi-pass hot working process, the total thermal deformation of the TiAl alloy should be controlled to be no more than 60%, the deformation of different passes can be consistent, and the total deformation of all passes needs to be consistent with the total deformation that needs to be controlled in the processing target. In an embodiment of the present invention, during the multi-pass hot working process, the total number of hot working passes n can be controlled to 2 to 3 passes, and the total deformation of all passes is preferably controlled to be 60%, so the deformation of a single pass is 60 / n%, that is, 20% to 30%. In addition, the following multi-pass hot working process parameters can be further preferably adopted: the deformation temperature used in the hot working is controlled to be 1200°C, and the strain rate is 0.01s -1 The deformation passes are 2 to 3 times, the deformation amount of a single pass is 20 to 30%, the insulation time between passes (i.e. the insulation time from the completion of the previous deformation pass to the next deformation pass) is 10 to 120s, and the total deformation amount is 60%.

[0028] The TiAl alloy ingot produced by the aforementioned fine-grained TiAl alloy hot working method exhibits a coarse, near-lamellar microstructure. Multiple hot working passes of the TiAl alloy ingot yield an equiaxed γ+B2 / β+α2 TiAl alloy billet with uniform grain size, no individual coarse grains, and no residual lamellar clusters. This TiAl alloy possesses excellent strength and ductility.

[0029] The specific technical effects of the present invention are demonstrated below through several embodiments.

[0030] Example 1

[0031] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 2 times, the deformation amount of a single pass is 30%, and the insulation time between passes is 10s.

[0032] Figure 1 The following is a 1000× SEM microstructure image of the TiAl alloy obtained in this embodiment after hot working. Figure 1 It can be seen that after multiple hot working, the TiAl alloy has a three-phase structure composed of equiaxed γ+B2 / β+α2, with an average grain size of 20-30μm. The grain size is uniform, and there are no individual abnormally grown coarse grains and lamellar clusters remaining.

[0033] Comparative Example 1

[0034] In this comparative example, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep warm for 2 minutes to melt the alloy components, turn off the power and cool to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is: the total deformation is controlled at 60%, the deformation temperature is 1200°C, and the strain rate is 0.01s -1 , the deformation pass is 1 pass, and the deformation amount of a single pass is 60%.

[0035] Figure 2 The SEM microstructure of the TiAl alloy obtained in this comparative example after hot working is shown in FIG. Figure 2 It can be seen that after single-pass hot working at 1200℃, the TiAl alloy does not form a three-phase microstructure composed of γ+B2 / β+α2, but a two-phase microstructure composed of equiaxed γ+B2 / β, and the equiaxed γ grains are coarse and the average grain size is greater than 30μm.

[0036] Comparing Comparative Example 1 with Example 1 reveals that the conventional single-pass hot working method employed in the comparative example results in a two-phase microstructure, whereas the multi-pass hot working method employed in the example results in a uniform and fine γ+B2 / β+α2 three-phase microstructure. The study found that this TiAl alloy with a uniform and fine γ+B2 / β+α2 three-phase structure exhibits excellent overall performance. The results demonstrate that, compared to conventional single-pass hot working, multi-pass hot working utilizes the inter-pass dwell phase to partially transform the γ phase into the α2 phase without grain growth, resulting in a uniform and fine γ+B2 / β+α2 three-phase structure, significantly improving the hot working performance of the TiAl alloy.

[0037] Comparative Example 2

[0038] In this comparative example, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep warm for 2 minutes to melt the alloy components, turn off the power and cool to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 2 times, the deformation amount of a single pass is 30%, and the insulation time between passes is 240s.

[0039] Figure 3 The following is a 1000× SEM microstructure image of the TiAl alloy obtained in this embodiment after hot working. Figure 3 It can be seen that after multiple hot working passes and holding for 240s between passes, the TiAl alloy did not form a three-phase microstructure composed of γ+B2 / β+α2, but a two-phase microstructure composed of equiaxed B2 / β+α2, and the α2 grains were coarse and the average grain size was greater than 50μm.

[0040] By comparing Comparative Example 2 with Example 1, it can be seen that when the comparative example also uses multi-pass hot working, the deformed structure is a B2 / β+α2 two-phase structure, and the α2 grains are coarse. This is because the heat preservation between passes is too long, resulting in the γ formed by preferential dynamic recrystallization during the deformation process completely transforming into the α2 phase, and the long heat preservation time causes the α2 phase to grow significantly. However, the example uses multi-pass hot working with a shorter heat preservation time between passes, and only part of the γ is completely transformed into the α2 phase, eventually forming a uniform and fine γ+B2 / β+α2 three-phase structure. The study found that this TiAl alloy with a uniform and fine γ+B2 / β+α2 three-phase structure exhibits excellent comprehensive performance. The results show that using an appropriate heat preservation time during multi-pass hot working can effectively avoid the complete occurrence of phase transformation and grain growth, significantly improving the hot working performance of the TiAl alloy.

[0041] Example 2

[0042] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 2 times, the deformation amount of a single pass is 30%, and the insulation time between passes is 60s.

[0043] Figure 4 The following is a 1000× SEM microstructure image of the TiAl alloy obtained in this embodiment after hot working. Figure 4 It can be seen that after multiple hot working, the TiAl alloy has a three-phase structure composed of equiaxed γ+B2 / β+α2, with an average grain size of 20-30μm. The grain size is uniform, and there are no individual abnormally grown coarse grains and lamellar clusters remaining.

[0044] Example 3

[0045] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 2 times, the deformation amount of a single pass is 30%, and the insulation time between passes is 120s.

[0046] Figure 5 The following is a 1000× SEM microstructure image of the TiAl alloy obtained in this embodiment after hot working. Figure 5It can be seen that after multiple hot working, the TiAl alloy has a three-phase structure composed of equiaxed γ+B2 / β+α2, with an average grain size of 20-30μm. The grain size is uniform, and there are no individual abnormally grown coarse grains and lamellar clusters remaining.

[0047] Example 4

[0048] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 3 times, the deformation amount of a single pass is 20%, and the insulation time between passes is 10s.

[0049] Similarly, the hot-worked TiAl alloy obtained in this embodiment has a three-phase microstructure consisting of equiaxed γ+B2 / β+α2, an average grain size of 20 to 30 μm, and a uniform grain size without individual abnormally grown coarse grains and lamellar clusters remaining.

[0050] Example 5

[0051] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 3 times, the deformation amount of a single pass is 20%, and the insulation time between passes is 60s.

[0052] Similarly, the hot-worked TiAl alloy obtained in this embodiment has a three-phase microstructure consisting of equiaxed γ+B2 / β+α2, an average grain size of 20 to 30 μm, and a uniform grain size without individual abnormally grown coarse grains and lamellar clusters remaining.

[0053] Example 6

[0054] In this embodiment, the chemical composition of the TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re. Take each component element according to the chemical composition ratio of the TiAl alloy, place the Ti element at the bottom of the crucible, then place the Al element, and finally place the remaining alloy component elements on the upper part of the crucible, place the crucible in a vacuum induction melting furnace, evacuate and fill it with argon, then slowly load 200A current and keep it warm for 2 minutes to melt the alloy components, turn off the power and cool it to room temperature to obtain an ingot. The smelted ingot is then turned over and vacuum induction melted again to ensure that the composition of the ingot is uniform. The TiAl alloy ingot obtained by the above-mentioned secondary smelting is subjected to multiple heat treatments using a hot rolling mill. The specific process is as follows: the total deformation is controlled at 60%, the deformation temperature of each pass is 1200°C, and the strain rate of each pass is 0.01s -1 The deformation passes are 3 times, the deformation amount of a single pass is 20%, and the insulation time between passes is 120s.

[0055] Similarly, the hot-worked TiAl alloy obtained in this embodiment has a three-phase microstructure consisting of equiaxed γ+B2 / β+α2, an average grain size of 20 to 30 μm, and a uniform grain size without individual abnormally grown coarse grains and lamellar clusters remaining.

[0056] The embodiment described above is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Persons skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, any technical solution obtained by equivalent substitution or equivalent transformation falls within the scope of protection of the present invention.

Claims

1. A fine-grained TiAl alloy hot working method, characterized in that: The TiAl alloy ingot with uniform composition obtained by vacuum induction melting is subjected to multi-pass hot working to improve the uniformity of the hot working structure of the TiAl alloy and obtain a fine-grained structure; during the multi-pass hot working process, the hot working temperature is controlled at 1150-1250°C and the strain rate is controlled at 0.001-1s -1 The deformation of a single pass is 20% to 30%, the holding time between passes is 10 to 120s, and the total deformation of all passes does not exceed 60%.

2. The fine-grained TiAl alloy hot working method according to claim 1, characterized in that: The chemical composition of the TiAl alloy is calculated as follows in atomic percentage: Al: 43-48%; Nb: 0-8%; Cr: 0-2%; V: 0-3%; Mo: 0~2%, B≤0.3%, Re≤0.3%, and the rest is Ti.

3. The fine-grained TiAl alloy hot working method according to claim 1, characterized in that: The TiAl alloy is Ti-44Al-6Nb-1Mo-0.13B-0.17Re.

4. The fine-grained TiAl alloy hot working method according to claim 1, characterized in that: The vacuum induction melting process comprises the following steps: taking each component element according to the chemical composition ratio of the TiAl alloy, placing Ti element element at the bottom of a crucible, followed by Al element element, and finally placing the remaining alloy component elements at the top of the crucible; placing the crucible in a vacuum induction melting furnace, evacuating the crucible, filling it with argon gas, then slowly applying current and maintaining the temperature to melt the alloy components; and then turning off the power and cooling it to room temperature to obtain an ingot.

5. The fine-grained TiAl alloy hot working method according to claim 4, characterized in that: During the vacuum induction melting process, the recorded current was 200 A and the holding time was 2 min.

6. The fine-grained TiAl alloy hot working method according to claim 4, characterized in that: The ingot obtained from the initial melting needs to be vacuum induction melted again before being used for multiple hot working to improve the uniformity.

7. The fine-grained TiAl alloy hot working method according to claim 1, characterized in that: In the multi-pass hot working process, the total number of hot working passes is 2 to 3 passes.

8. The fine-grained TiAl alloy hot working method according to claim 1, characterized in that: During the multi-pass hot working process, the total deformation of all passes is controlled to be 60%.

9. A TiAl alloy billet obtained by the fine-grained TiAl alloy hot working method according to any one of claims 1 to 8.

10. The TiAl alloy billet according to claim 9, characterized in that: The TiAl alloy billet has a fine-grained structure composed of equiaxed γ+B2 / β+α2, with a grain size of 20 to 30 μm and no individual coarse grains.

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