A method for precision control of superplastic forming of a titanium alloy case of an aero-engine

Abstract

The application discloses a method for precisely controlling superplastic forming of a titanium alloy machine case of an aero-engine and belongs to the technical field of titanium alloy hot working. The forming method is a whole technical scheme of a combination of multi-section pressure control, isothermal forging, deformation amount control, machining allowance and microstructure regulation. The forming method is characterized in that, by means of the cooperation of the sectional pressure control, the deformation amount and the deformation rate, and in combination with the blank and the die, isothermal forging is carried out, so that the machine case forging is precisely formed, the single-side machining allowance of the forging is 3-4 mm, compared with the very large machining allowance of the ordinary hot die forging, the hardening range of the forging is further improved, and the uniformity of the structure of the final forging is improved. The forming process can solve the problems of poor surface quality and uneven performance and structure in the complex large machine case, and the overall performance of the machine case is improved.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy hot working technology, specifically relating to a method for precisely controlling the superplastic forming of titanium alloy casings for aero engines. Background Technology

[0002] Titanium alloys are lightweight metals with high specific strength, widely used in aviation, aerospace, and energy fields. They are highly favored for their excellent high-temperature performance, good mechanical properties, and stable chemical properties. In the aerospace field, they are mainly used to manufacture high-temperature components such as engine compressor casings and skins.

[0003] Compressor casings require sufficient creep resistance and overload capacity throughout their entire lifespan. Under operating conditions, the casing primarily bears gas loads and inertial forces, secondarily thermal loads, and various stresses. The gas loads and inertial forces act on the casing in the form of axial forces, lateral forces, bending moments, and torques. How to reduce the manufacturing cost of complex, large casings while addressing the impact of thermal loads on material strength has become an important direction for current research and development.

[0004] The existing manufacturing technologies for the casing mainly include: (1) irregular forming process: the casing is formed by upsetting and punching, expanding and prefabricating multiple times and heat treatment; (2) multi-step assembly of mold forming manufacturing: including the blank is formed by upsetting, punching, expanding the blank with a rod, forging the blank with a mold and forming the casing ring segment in the form of a conical ring, and multiple coaxial casing ring segments are connected from front to back; (3) investment casting forming: including pressing the wax mold of the casing, opening process holes on the cavity side of the wax mold, making the shell of the cavity, filling the cavity with mullite sand and sealing the cavity opening, and finally making the overall back shell of the casing.

[0005] However, the aforementioned manufacturing technologies currently suffer from several drawbacks: complex casing fabrication processes, increased waste due to step-by-step processing, the need to coordinate multiple processes, complex quality control, cumulative errors leading to decreased precision, and the requirement for secondary processing. These methods are only suitable for small-batch, customized casings. Besides fulfilling its supporting function, the casing's structural design must also guarantee strength and stability. As a typical thin-walled component, the casing requires extremely high strength under the aforementioned operating conditions. Existing manufacturing processes have not fundamentally solved the problems of improving casing machining accuracy and performance. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for precisely controlling the superplastic forming of titanium alloy casings for aero-engines. This invention fundamentally solves the problems of complex machining processes, inaccurate dimensional control, unstable performance, and raw material waste in casing manufacturing. Simultaneously, it addresses the significantly increased difficulty in controlling the uniformity of forging microstructure and properties due to larger dimensions, which can easily lead to reduced strength and coarse microstructure in forgings, failing to meet usage requirements. The superplastic forming method provided by this invention enables precise, integrated forming of large, complex casings while simultaneously improving the overall mechanical properties of the casing.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] One of the technical solutions of this invention is to provide a method for precisely controlling the superplastic forming of titanium alloy casings for aero engines, comprising the following steps:

[0009] The titanium alloy billet is preheated to 30~60℃ below its β phase transformation temperature (Tβ). The preheating time to the specified temperature is the thickness value of the titanium alloy billet H×(0.6~0.9)s, where the thickness value of the titanium alloy billet H is in mm.

[0010] The aircraft engine casing mold is preheated to the same temperature as the preheated titanium alloy billet;

[0011] The preheated titanium alloy billet is placed into a preheated mold and subjected to single-fire die casting forging at the preheated temperature. During the single-fire die casting forging process, the deformation is controlled at 50%~70%, and the average strain rate is 0.0002~0.00025s. -1 The pressure changes are as follows: pressurize for 2 minutes to 500T and hold for 5 minutes; pressurize from 500T to 1500T and hold for 5 minutes; pressurize from 1500T to 2500T and hold for 5 minutes; pressurize from 2500T to 3000T and hold for 20-30 minutes before releasing pressure.

[0012] After die casting and forging, the forging is removed and water-cooled within 20 seconds (ensuring a cooling rate ≥10℃ / min), and then annealed to obtain the titanium alloy casing for aero-engines.

[0013] Because the titanium alloy casing forgings for aero-engines are large in size, the air cooling rate is very slow, which is very unfavorable for the uniform control of the casing's microstructure and properties. If conventional processes are followed and water cooling is performed only after solution heat treatment, it is difficult to reduce the microstructure differences caused by slow cooling after forging.

[0014] The forming method employed in this invention is an integrated technical solution combining "multi-segment pressure control + isothermal forging + deformation control + machining allowance + microstructure regulation". Multi-segment pressure control avoids severe die wear and precisely controls the forming of the forging, preventing incomplete filling due to low pressure and cracking due to high pressure. This invention heats both the billet and the forging die to the same temperature, based on the negative correlation between the material's deformation resistance and temperature. No temperature drop occurs during prolonged contact between the billet and the die, resulting in very low deformation resistance and good plasticity in the billet. This fully utilizes the high plasticity of the billet at low strain rates to achieve large forming in each pass of the forging process for large-size casing forgings. The deformation amount in this invention is controlled at 50%~70% because when the forging deformation amount is less than 40%, the grains in the forging are very coarse; as the deformation amount increases, the grain size gradually decreases; when the forging deformation amount is greater than 70%, the grains will grow again due to factors such as recrystallization; while when the forging deformation amount is between 50% and 70%, the anisotropy in the microstructure is minimal, the grains are the finest and most uniform, and the overall performance is optimal. The solution heat treatment is carried out using a water-cooling process, which can, to a certain extent, avoid grain growth caused by slow cooling. During each water-cooling process, the uniformity of the microstructure is controlled and the variability is reduced. Simultaneously, during water cooling, the high-temperature β phase undergoes a martensitic transformation, and the microstructure contains many dislocations and twins, which have a severe pinning effect on slip, thereby improving the strength of the material.

[0015] The forming method of the present invention, through the interplay of segmented pressure control, deformation amount and deformation rate, combined with the forging of the billet and the die at the same temperature, enables the casing forging to be precisely formed. The machining allowance on one side of the forging is 3~4mm, which is much larger than the machining allowance of ordinary hot die forging. This further improves the hardening range of the forging, thereby enhancing the uniformity of the final forging structure.

[0016] This forming process can solve the problems of poor surface quality and uneven microstructure in complex large casings, thereby improving the overall performance of the casing. Segmented pressure control, billet and die temperature control, and forging rate control are crucial; control of deformation is also critical, as it can fully break down the original grains and obtain a uniform and fine equiaxed microstructure.

[0017] At the forging temperature of this invention, the titanium alloy billet has high structural stability, and the high-temperature softening resistance (high melting point) of the α phase is preserved; if the temperature is too high (entering the β single-phase region), the β grains will coarsen, and after cooling, coarse lamellar α phase will be formed, reducing the strength.

[0018] This process allows for precise control of the casing's forming accuracy, enabling one-time forging and increasing production efficiency by 40% compared to traditional processes, while significantly reducing material waste. In particular, the small size and uniform distribution of the equiaxed primary α phase contribute to improved casing strength and plasticity.

[0019] Preferably, the titanium alloy billet is coated with glass lubricant on its surface before preheating; the aero-engine casing mold is coated with glass lubricant on its inner surface before preheating.

[0020] Preferably, the annealing temperature is 710~720℃, and the holding time is 2~5h.

[0021] Preferably, the flow rate of the water cooling is 2m / s to 5m / s.

[0022] The second technical solution of the present invention provides a titanium alloy casing for an aero-engine prepared according to the above-mentioned superplastic forming method for precisely controlling the titanium alloy casing of an aero-engine.

[0023] The titanium alloy casing for aero-engines manufactured according to the method of the present invention has a tensile strength ≥960MPa, yield strength ≥880MPa, elongation ≥13.0%, and reduction of area ≥35% at any part of the casing at room temperature; and a tensile strength ≥650MPa at a high temperature of 400℃.

[0024] The beneficial technical effects of the present invention are as follows:

[0025] The superplastic forming method for precisely controlling the titanium alloy casing of aero-engines provided by this invention can produce large and complex casing forgings in one step. This method enables precise one-piece forming of large and complex casings, resulting in forgings with high strength, good plasticity, and excellent stability. Attached Figure Description

[0026] Figure 1 A macroscopic view of the casing prepared in Example 1.

[0027] Figure 2 The metallographic structure of the casing prepared in Example 1 is shown in Figure 1.

[0028] Figure 3 The metallographic structure of the casing prepared in Example 2 is shown in the figure.

[0029] Figure 4 Metallographic diagram of the casing prepared for Comparative Example 1. Detailed Implementation

[0030] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the present invention.

[0031] It should be noted that any aspects not described in detail in this invention are conventional practices in the field and are not the focus of this invention.

[0032] Furthermore, regarding the numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any stated value or intermediate value within a stated range, as well as each smaller range between any other stated value or intermediate value within said range, are also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0033] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar to or equivalent to those described herein may be used in the implementation or testing of this invention.

[0034] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0035] The titanium alloy used in the embodiments and comparative examples of this invention is TC4 (Ti-6Al-4V) titanium alloy.

[0036] Example 1

[0037] A method for precise control of superplastic forming of aero-engine casings:

[0038] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1000mm, and the heating time T1=1000×0.9s=900s;

[0039] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 4 hours;

[0040] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 50%;

[0041] The average strain rate of the hydraulic press under this deformation is 0.00021 s⁻¹. -1 The hydraulic press press press procedure is as follows: pressurize to 500T for 2 minutes and hold for 5 minutes; pressurize from 500T to 1500T for 1 minute and hold for 5 minutes; pressurize from 1500T to 2500T for 1 minute and hold for 5 minutes; pressurize from 2500T to 3000T for 1 minute and hold for 20 minutes before releasing pressure.

[0042] 4) Open the forging mold, take out the formed titanium alloy casing fine forging and move it into water for water cooling within 20 seconds (water cooling flow rate 3m / s).

[0043] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0044] Macroscopic images and metallographic structures of the casing prepared in Example 1 are shown below. Figure 1 and Figure 2 As shown.

[0045] Example 2

[0046] A method for precise control of superplastic forming of aero-engine casings:

[0047] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1200mm, and the heating time T1=1200×0.9s=1080s;

[0048] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 6 hours;

[0049] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 70%;

[0050] The average strain rate of the hydraulic press under this deformation is 0.00023 s⁻¹. -1 The hydraulic press press press procedure is as follows: pressurize to 500T for 2 minutes and hold for 5 minutes; pressurize from 500T to 1500T for 1 minute and hold for 5 minutes; pressurize from 1500T to 2500T for 1 minute and hold for 5 minutes; pressurize from 2500T to 3000T for 1 minute and hold for 30 minutes before releasing the pressure.

[0051] 4) Open the forging mold, take out the formed titanium alloy casing forging and move it into water for water cooling within 20 seconds (water cooling flow rate 5m / s).

[0052] 5) Anneal the forgings at 715℃ for 4 hours, and then air-cool them to room temperature after the treatment.

[0053] The metallographic structure of the casing prepared in Example 2 is shown in the figure. Figure 3 As shown.

[0054] Comparative Example 1

[0055] Superplastic forming method for engine casing:

[0056] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1000mm, and the heating time T1=1000×0.9s=900s;

[0057] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 4 hours;

[0058] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 50%;

[0059] The average strain rate of the hydraulic press under this deformation is 0.0042 s⁻¹. -1 The hydraulic press press pressure increase procedure is as follows: directly increase the pressure to 8000T, hold the pressure for 2 minutes, and then release the pressure.

[0060] 4) Open the forging mold, take out the formed titanium alloy casing fine forging and move it into water for water cooling within 20 seconds (water cooling flow rate 3m / s).

[0061] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0062] The metallographic structure of the casing prepared in Comparative Example 1 is shown in the figure below. Figure 4 As shown.

[0063] Comparative Example 2

[0064] Superplastic forming method for engine casing:

[0065] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1000mm, and the heating time T1=1000×0.9s=900s;

[0066] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 4 hours;

[0067] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 50%;

[0068] The strain rate of the hydraulic press under this deformation is 0.00021 s. -1 The hydraulic press press pressure increase procedure is as follows: the pressure changes are: increase pressure for 2 minutes to 500T and hold pressure for 5 minutes, increase pressure from 500T to 1500T for 1 minute and hold pressure for 5 minutes, increase pressure from 1500T to 2500T for 1 minute and hold pressure for 5 minutes, increase pressure from 2500T to 3000T for 1 minute and hold pressure for 20 minutes and then release pressure.

[0069] 4) Open the forging die, remove the formed titanium alloy casing forging, and air cool it to room temperature;

[0070] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0071] Comparative Example 3

[0072] Superplastic forming method for engine casing:

[0073] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1100mm, and the heating time T1=1100×0.9s=990s;

[0074] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 4 hours;

[0075] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 80%;

[0076] The average strain rate of the hydraulic press under this deformation is 0.00022 s⁻¹. -1 The hydraulic press press press procedure is as follows: the pressure changes are: pressurize for 2 minutes to 500T and hold for 5 minutes, pressurize from 500T to 1500T and hold for 5 minutes, pressurize from 1500T to 2500T and hold for 5 minutes, pressurize from 2500T to 3000T and hold for 40 minutes and then release the pressure.

[0077] 4) Open the forging mold, take out the formed titanium alloy casing fine forging and move it into water for water cooling within 20 seconds (water cooling flow rate 3m / s).

[0078] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0079] Comparative Example 4

[0080] Superplastic forming method for engine casing:

[0081] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=900mm, and the heating time T1=900×0.9s=810s;

[0082] 2) Coat the mold with a layer of glass lubricant and keep it at 930℃ for 4 hours;

[0083] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 30%;

[0084] The average strain rate of the hydraulic press under this deformation is 0.00017 s⁻¹. -1 The hydraulic press press pressure increase procedure is as follows: the pressure changes are: increase pressure for 2 minutes to 500T and hold pressure for 5 minutes, increase pressure from 500T to 1500T for 1 minute and hold pressure for 5 minutes, increase pressure from 1500T to 2500T for 1 minute and hold pressure for 5 minutes, increase pressure from 2500T to 3000T for 1 minute and hold pressure for 10 minutes and then release pressure.

[0085] 4) Open the forging mold, take out the formed titanium alloy casing fine forging and move it into water for water cooling within 20 seconds (water cooling flow rate 3m / s).

[0086] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0087] Comparative Example 5

[0088] Superplastic forming method for engine casing:

[0089] 1) Coat the surface of the titanium alloy billet (Tβ=980℃) with glass lubricant, heat the titanium alloy billet to 930℃, the thickness of the titanium alloy billet H=1000mm, and the heating time T1=1000×0.9s=900s;

[0090] 2) Coat the mold with a layer of glass lubricant and keep it at 700℃ for 4 hours;

[0091] 3) The blank is loaded into the mold and die-cast into the required casing shape in one go using a hydraulic press at 930℃, with the deformation controlled at 50%;

[0092] The strain rate of the hydraulic press under this deformation is 0.00014 s⁻¹. -1 The hydraulic press press press procedure is as follows: the pressure changes are: pressurize for 2 minutes to 500T and hold for 5 minutes, pressurize from 500T to 1500T and hold for 5 minutes, pressurize from 1500T to 2500T and hold for 5 minutes, pressurize from 2500T to 3000T and hold for 40 minutes and then release the pressure.

[0093] 4) Open the forging mold, take out the formed titanium alloy casing fine forging and move it into water for water cooling within 20 seconds (water cooling flow rate 3m / s).

[0094] 5) Anneal the forgings at 720℃ for 2 hours, and then air-cool them to room temperature after the treatment.

[0095] The mechanical properties of the casings prepared in Examples 1-2 and Comparative Examples 1-5 were tested in accordance with GJB 2744A-2007 "Specification for Titanium and Titanium Alloy Forgings for Aviation". The test results are shown in Table 1.

[0096] Table 1 Mechanical properties of the casings prepared in each group

[0097] Tensile strength (MPa) elongation % Reduction of area % High-temperature tensile strength (MPa, 400℃) Example 1 1000 16 37 700 Example 2 950 18 42 680 Comparative Example 1 900 10 28 500 Comparative Example 2 855 15 35 520 Comparative Example 3 875 13 26 560 Comparative Example 4 860 13 28 560 Comparative Example 5 855 14 33 480 Forging Standard (GJB 2744A-2007) ≥895 ≥10 ≥30 ≥600

[0098] from Figure 2As can be seen from the data, the metallographic structure of the casing prepared in Example 1 is a typical equiaxed structure, with the primary α phase content all exceeding 60%. The α phases are of basically uniform size and distribution, while the secondary α phases are fine and lamellar with a certain aspect ratio. Combined with the mechanical property data in Table 1, it can be seen that the casing possesses high strength and plasticity, exhibiting excellent comprehensive performance. Figure 4 The microstructure of the casing prepared in Comparative Example 1 is a two-phase microstructure, with significantly lower primary α-phase content and equiaxed structure compared to Example 1. The significant difference in microstructure between the two results in performance failure. The stepped pressure loading control technology in Example 1 prevents titanium alloys from oxidizing or absorbing hydrogen at high temperatures. The oxide layer (TiO2) introduces surface brittleness, while hydrogen absorption leads to hydrogen embrittlement, significantly reducing high-temperature load-bearing capacity. The stepped pressure loading control technology effectively improves the service life of forging dies and controls the precision forming and microstructure uniformity of forgings.

[0099] Figure 3 The metallographic structure of the casing prepared in Example 2 is similar to that in Example 1. The mechanical property data in Table 1 also show that the casing has high strength and plasticity and excellent comprehensive performance.

[0100] Comparing the mechanical property data of Example 1 and Comparative Example 1 in Table 1, it can be seen that without gradient pressure increase, excessively rapid pressure increase will cause a decrease in the tensile strength and elongation of the forging, and the high-temperature tensile strength will not meet the usage standards of the casing. The reason is that the lack of gradient pressure increase leads to uneven microstructure distribution, and the primary α phase is in an elongated shape rather than an equiaxed shape, and there are only a small amount of lamellar α phase, resulting in low plasticity and strength.

[0101] Comparing the mechanical property data of Example 1 and Comparative Example 2 in Table 1, it can be seen that the use of air cooling after forging resulted in a decrease in the tensile strength of the forging, and the high-temperature tensile strength did not meet the usage standards of the casing. The reason is that air cooling has a larger degree of undercooling compared to water cooling, which prevents the precipitation of martensite needle-like structures, causes the primary α phase to grow significantly, and weakens the fine grain strengthening effect, thereby leading to a decrease in tensile strength.

[0102] Comparing the mechanical property data of Example 1 and Comparative Example 3 in Table 1, it can be seen that when the forging deformation is too large, the tensile strength and elongation of the forging decrease, and the high-temperature tensile strength does not meet the usage standards of the casing. This is because while increased deformation leads to more complete dynamic recrystallization (DRX), resulting in grain refinement (Hall-Petch effect) and contributing to strength, excessive deformation may cause dislocation density saturation or even the formation of local shear bands, inducing microcracks and thus reducing strength. Moderate deformation (e.g., 50%~70%) promotes uniform recrystallization, forming fine equiaxed grains and improving plasticity. Excessive deformation (e.g., >70%) may hinder grain boundary slip or cause microcrack propagation, reducing elongation.

[0103] Comparing the mechanical property data of Example 1 and Comparative Example 4 in Table 1, it can be seen that when the forging deformation is too small, the degree of recrystallization is insufficient because the critical deformation amount is not reached, the size of the primary α phase does not change much, the grain refinement is not obvious, and the performance does not meet the standards.

[0104] Comparing the mechanical property data of Example 1 and Comparative Example 5 in Table 1, it can be seen that when the forging temperature of the mold and the forging is different, the tensile strength and elongation of the forging will decrease, and the high-temperature tensile strength will not meet the usage standards of the casing. Keeping the mold and billet temperatures the same can avoid the deterioration of material properties caused by abnormal grain growth or precipitation of harmful phases (such as ω phase) due to temperature fluctuations.

[0105] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A method for precisely controlling the superplastic forming of titanium alloy casings for aero-engines, characterized in that, Includes the following steps: The titanium alloy billet is preheated to 30~60℃ below its β phase transformation temperature. The preheating time to the specified temperature is the thickness value of the titanium alloy billet H×(0.6~0.9)s, where the thickness value of the titanium alloy billet H is in mm. The aircraft engine casing mold is preheated to the same temperature as the preheated titanium alloy billet; The preheated titanium alloy billet is placed into a preheated mold and subjected to single-fire die casting forging at the preheated temperature. During the single-fire die casting forging process, the deformation is controlled at 50%~70%, and the average strain rate is 0.0002~0.00025s. -1 The pressure changes are as follows: pressurize for 2 minutes to 500T and hold for 5 minutes; pressurize from 500T to 1500T and hold for 5 minutes; pressurize from 1500T to 2500T and hold for 5 minutes; pressurize from 2500T to 3000T and hold for 20-30 minutes before releasing pressure. After die casting and forging are completed, the forging is removed and water-cooled within 20 seconds, and then annealed to obtain the titanium alloy casing for aero-engines.

2. The method for precisely controlling the superplastic forming of titanium alloy casings for aero-engines according to claim 1, characterized in that, The titanium alloy billet is coated with glass lubricant on its surface before preheating; the aero-engine casing mold is coated with glass lubricant on its inner surface before preheating.

3. The method for precisely controlling the superplastic forming of titanium alloy casings for aero-engines according to claim 1, characterized in that, The annealing temperature is 710~720℃, and the holding time is 2~5h.

4. The method for precisely controlling the superplastic forming of titanium alloy casings for aero-engines according to claim 1, characterized in that, The flow rate of the water cooling is 2m / s to 5m / s.

5. An aero-engine titanium alloy casing prepared by the superplastic forming method for precisely controlling the aero-engine titanium alloy casing according to any one of claims 1 to 4.

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