Superplastic forming method for accurately controlling titanium alloy casing of aero-engine

Abstract

The invention discloses a superplastic forming method for accurately controlling a titanium alloy casing of an aero-engine, and belongs to the technical field of titanium alloy hot working. The forming method adopted by the invention is an integral technical scheme of synergistically combining multi-section partial pressure control, isothermal forging, deformation control, machining allowance and microstructure regulation and control. According to the forming method, by means of segmented pressure control, mutual cooperation of the deformation amount and the deformation rate and combination of equal-temperature forging of the blank and the die, the casing forge piece is precisely formed, the single-side machining allowance of the forge piece is 3-4 mm, compared with the large machining allowance of common hot die forging, the through quenching range of the forge piece is further widened, and the yield of the casing forge piece is increased. Therefore, the structure uniformity of the final forge piece is improved. The forming process can solve the problems of poor surface quality and non-uniform performance structure in a complex large casing, and realizes improvement of the overall performance of the casing.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy hot processing, and in particular relates to a method for precisely controlling superplastic forming of a titanium alloy casing of an aero-engine. Background Art

[0002] Titanium alloy is a lightweight, high-specific-strength metal widely used in aviation, aerospace, energy, and other fields. It is highly sought after for its excellent high-temperature performance, good mechanical properties, and stable chemical properties. In the aviation field, it is primarily used to manufacture high-temperature components such as engine compressor cases and skins.

[0003] The compressor casing requires sufficient creep resistance and the ability to withstand overloads throughout its lifespan. During operation, the casing primarily withstands gas loads and mass inertia, as well as thermal loads and some stresses. Gas loads and mass inertia act on the casing in the form of axial, transverse, or lateral forces, bending moments, and torque. Reducing the manufacturing cost of complex, large casings while addressing the impact of thermal loads on material strength has become a key research and development focus.

[0004] The existing manufacturing technologies of casings mainly include: (1) special-shaped forming process: the casing is formed by roughing, punching, expanding, multiple prefabrication and heat treatment; (2) multi-step assembly of tire membrane forming: including roughing, punching, horse rod expansion, tire membrane forging and special-shaped ring forming of the casing ring segment into a conical ring shape, and multiple coaxial casing ring segments are connected in sequence from front to back; (3) investment casting: including pressing the wax mold of the casing, opening the process hole on the cavity side of the wax mold, shelling the cavity, filling the cavity with mullite sand and sealing the cavity mouth, and finally shelling the entire back layer of the casing.

[0005] However, the above manufacturing technologies currently have problems such as complex receiver preparation process steps, step-by-step processing that produces more waste, the need to coordinate multiple processes, complex quality control, cumulative errors that lead to reduced accuracy, and the need for secondary processing. These methods are only suitable for small batches of customized receivers. In addition to meeting the support function, the structural design of the receiver also requires the design scheme to ensure strength and stability requirements. The receiver is a typical thin-walled part. Given the above working conditions, its strength requirements are very high. The existing preparation process has not fundamentally solved the problems of processing accuracy and performance improvement of the receiver. Summary of the Invention

[0006] To address the aforementioned technical issues, the present invention provides a method for precisely controlling the superplastic forming of titanium alloy casings for aircraft engines. This method fundamentally addresses the complex processing and dimensional precision control, unstable performance, and waste of raw materials associated with casings. It also addresses the exponentially increasing difficulty in controlling the uniformity of forging structure and performance, often resulting in reduced strength, coarse structure, and failure to meet operational requirements. The superplastic forming method provided by the present invention enables precise, integrated forming of large, complex casings while improving their overall mechanical properties.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] One of the technical solutions of the present invention is to provide a method for precisely controlling the superplastic forming of a titanium alloy casing of an aerospace engine, comprising the following steps:

[0009] Preheat the titanium alloy billet to 30-60°C below its β phase transformation temperature (Tβ). The time for preheating to the limited temperature is the thickness value of the titanium alloy billet H×(0.6-0.9)s, where the thickness value H of the titanium alloy billet is measured in mm;

[0010] Preheating the aircraft engine casing mold to be isothermal with the preheated titanium alloy blank;

[0011] The preheated titanium alloy billet is placed in a preheated mold and subjected to a first-fire die-casting forging process at the preheating temperature. During the first-fire die-casting forging process, the deformation is controlled to be 50% to 70%, and the average strain rate is 0.0002 to 0.00025 s -1 The pressure changes are: increase the pressure for 2 minutes to 500T and then maintain the pressure for 5 minutes; increase the pressure from 500T for 1 minute to 1500T and then maintain the pressure for 5 minutes; increase the pressure from 1500T for 1 minute to 2500T and then maintain the pressure for 5 minutes; increase the pressure from 2500T for 1 minute to 3000T and then maintain the pressure for 20 minutes to 30 minutes before releasing the pressure;

[0012] After the die-casting forging is completed, the forging is taken out and water-cooled within 20 seconds (ensuring a cooling rate of ≥10°C / min), and then annealed to obtain an aircraft engine titanium alloy casing.

[0013] Due to the large size of the titanium alloy casing forgings of aircraft engines, the cooling rate of air cooling is very slow, which is very unfavorable for the uniform control of the casing structure and performance. If only water cooling is performed after solution heat treatment according to conventional processes, it is difficult to reduce the structural differences caused by slow cooling after forging.

[0014] The forming method adopted by the application is a whole technical scheme of the synergistic combination of "multi-stage pressure control + isothermal forging + deformation amount control + machining allowance + microstructure regulation". The multi-stage pressure control can avoid serious die wear and precisely control the forming of the forgings, avoid incomplete filling caused by small pressure and crack generation caused by large pressure. The billet and the forging die are heated to the same temperature in the application, which is based on the negative correlation between the deformation resistance of the material and the temperature. The billet and the die do not appear temperature drop during long time contact, so the deformation resistance of the billet is very small and the plasticity is good. The high plasticity characteristics of the billet under low strain rate are fully utilized to realize large forming of each pass in the forging process of the large-size machine case forgings. The deformation amount control is 50%~70%, because when the forging deformation amount is less than 40%, the grain of the forging is very coarse; with the increase of the deformation amount, the grain size gradually decreases; when the forging deformation amount is greater than 70%, the grain will grow again due to recrystallization and other factors; and when the forging deformation amount is 50%~70%, the anisotropy in the microstructure is the smallest, the grain is the smallest and uniform, and the comprehensive performance is the best. The heat treatment of solid solution is implemented by water cooling process, which can avoid grain growth caused by slow cooling to a certain extent, control the uniformity of the structure and reduce the difference in each water cooling process; at the same time, the high-temperature beta phase in the water cooling process is transformed into martensite, the structure contains a lot of dislocations and twins, which has a serious pinning effect on slip, thereby improving the strength of the material.

[0015] The forming method of the application realizes precise forming of the machine case forgings by the mutual cooperation of the segmented pressure control, deformation amount and deformation rate, and the forging of the billet and the die at the same temperature, so that the single-side machining allowance of the forgings is 3~4mm, which is much larger than the machining allowance of ordinary hot die forging, further improves the hardening range of the forgings, and improves the uniformity of the structure of the final forgings.

[0016] The forming process can solve the problems of poor surface quality and non-uniform performance and structure in the complex large machine case, and realize the improvement of the overall performance of the machine case. The segmented pressure control, temperature control of the billet and the die, and control of the forging rate are very important; the control of the deformation amount is also very important, which can fully break the original grain and obtain uniform and small equiaxed structure.

[0017] The titanium alloy billet has high stability of the structure at the forging temperature, and the high-temperature softening resistance (high melting point) of the alpha phase is retained; if the temperature is too high (entering the beta single-phase region), the beta grain will be coarsened, and coarse lamellar alpha phase will be formed after cooling, reducing the strength.

[0018] The process can accurately control the forming precision of the machine case, realize one-time forging forming, improve the production efficiency by 40% compared with the traditional process, and greatly reduce the waste of materials. Especially, the size of the equiaxed primary alpha phase is small and uniformly distributed, which is beneficial to improve the strength and plasticity of the machine case.

[0019] Preferably, the surface of the titanium alloy blank is coated with glass lubricant before preheating; and the inner surface of the aircraft engine casing mold is coated with glass lubricant before preheating.

[0020] Preferably, the annealing temperature is 710-720° C., and the holding time is 2-5 hours.

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

[0022] The second technical solution of the present invention is to provide an aerospace engine titanium alloy casing manufactured according to the above-mentioned method of precisely controlling the superplastic forming of the aerospace engine titanium alloy casing.

[0023] Any part of the aviation engine titanium alloy casing prepared according to the method of the present invention has a tensile strength of ≥960MPa, a yield strength of ≥880MPa, an elongation of ≥13.0%, and a cross-sectional shrinkage of ≥35% at room temperature; and a tensile strength of ≥650MPa at a high temperature of 400°C.

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

[0025] The method for precisely controlling the superplastic forming of titanium alloy casings for aircraft engines, provided by the present invention, can produce large, complex casing forgings in a single step. This method enables precise, integrated forming of large, complex casings, resulting in forgings with high strength, good plasticity, and excellent stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a macroscopic image of the casing prepared in Example 1.

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

[0028] Figure 3 This is the metallographic structure diagram of the casing prepared in Example 2.

[0029] Figure 4 This is the metallographic structure diagram of the casing prepared in Comparative Example 1. DETAILED DESCRIPTION

[0030] Various exemplary embodiments of the present invention are now described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention. It should be understood that the terms used in the present invention are only for describing specific embodiments and are not intended to limit the present invention.

[0031] It should be pointed out that the matters not described in detail in the present invention are conventional operating means in this field and are not the focus of the present invention.

[0032] In addition, for numerical ranges in the present invention, it is understood that each intervening value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between any stated value or stated range, and any other stated value or intervening value in the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

[0033] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of the present invention.

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

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

[0036] Example 1

[0037] Precisely controlled superplastic forming method for aircraft engine casing:

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

[0039] 2) The mold is coated with a layer of glass lubricant and kept at 930°C for 4 hours;

[0040] 3) Place the blank into the mold and use a hydraulic press to die-cast it into the required casing shape at 930°C in one step, with the deformation controlled to 50%;

[0041] The average strain rate of the hydraulic press under this deformation is 0.00021s -1 The hydraulic press pressure boosting procedure is as follows: boost for 2 minutes to 500T, then maintain pressure for 5 minutes; boost from 500T to 1500T for 1 minute, then maintain pressure for 5 minutes; boost from 1500T to 2500T for 1 minute, then maintain pressure for 5 minutes; boost from 2500T to 3000T for 1 minute, then maintain pressure for 20 minutes, then release pressure;

[0042] 4) Open the forging die, take out the formed titanium alloy casing refined 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°C for 2 h and air cool to room temperature.

[0044] The macroscopic image and metallographic structure diagram of the casing prepared in Example 1 are as follows: Figure 1 and Figure 2 shown.

[0045] Example 2

[0046] Precisely controlled superplastic forming method for aircraft engine casing:

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

[0048] 2) The mold is coated with a layer of glass lubricant and kept at 930°C for 6 hours;

[0049] 3) The blank is placed in a mold and die-cast into the desired casing shape using a hydraulic press at 930°C, with the deformation controlled to 70%;

[0050] The average strain rate of the hydraulic press under this deformation is 0.00023s -1 The hydraulic press pressure boosting procedure is as follows: boost for 2 minutes to 500T, then maintain pressure for 5 minutes; boost from 500T to 1500T for 1 minute, then maintain pressure for 5 minutes; boost from 1500T to 2500T for 1 minute, then maintain pressure for 5 minutes; boost from 2500T to 3000T for 1 minute, then maintain pressure for 30 minutes, then release pressure;

[0051] 4) Open the forging die, take out the formed titanium alloy casing refined 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°C for 4 hours and then air cool to room temperature.

[0053] The metallographic structure of the casing prepared in Example 2 is as follows: Figure 3 shown.

[0054] Comparative Example 1

[0055] Superplastic forming method of engine casing:

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

[0057] 2) The mold is coated with a layer of glass lubricant and kept at 930°C for 4 hours;

[0058] 3) The blank is loaded into the mold, and the desired shape of the engine case is formed by one-step die casting at 930°C using a hydraulic press, with a deformation of 50%;

[0059] The average strain rate of the hydraulic press at this deformation is 0.0042 s -1 The pressure increasing procedure of the hydraulic press is: directly increasing to 8000T, holding for 2 min, and then releasing pressure;

[0060] 4) The forging mold is opened, the formed titanium alloy engine case is taken out, and is moved to water within 20 s for water cooling (water cooling flow rate is 3 m / s);

[0061] 5) The forged piece is annealed at 720°C for 2 h, and is air cooled to room temperature after the treatment.

[0062] The metallographic structure of the engine case prepared in Comparative Example 1 is shown in Figure 4 .

[0063] Comparative Example 2

[0064] Superplastic forming method of the engine case:

[0065] 1) The titanium alloy blank (Tβ=980°C) is coated with a glass lubricant, the titanium alloy blank is heated to 930°C, the thickness of the titanium alloy blank is H=1000 mm, and the heating time is T1=1000×0.9 s=900 s;

[0066] 2) The mold is coated with a layer of glass lubricant and is kept at 930°C for 4 h;

[0067] 3) The blank is loaded into the mold, and the desired shape of the engine case is formed by one-step die casting at 930°C using a hydraulic press, with a deformation of 50%;

[0068] The strain rate of the hydraulic press at this deformation is 0.00021 s -1 The pressure increasing procedure of the hydraulic press is: the pressure is changed to increase to 500T for 2 min, holding for 5 min, increasing to 1500T for 1 min from 500T, holding for 5 min, increasing to 2500T for 1 min from 1500T, holding for 5 min, increasing to 3000T for 1 min from 2500T, holding for 20 min, and then releasing pressure;

[0069] 4) The forging mold is opened, the formed titanium alloy engine case is taken out, and is air cooled to room temperature;

[0070] 5) The forged piece is annealed at 720°C for 2 h, and is air cooled to room temperature after the treatment.

[0071] Comparative Example 3

[0072] Superplastic forming method of the engine case:

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

[0074] 2) The mold is coated with a layer of glass lubricant and kept at 930°C for 4 hours;

[0075] 3) The blank is placed in a mold and die-cast into the desired casing shape using a hydraulic press at 930°C in one step, with the deformation controlled to 80%;

[0076] The average strain rate of the hydraulic press under this deformation is 0.00022s -1 The hydraulic press pressure boosting procedure is as follows: pressure change is: boosting to 500T for 2 minutes and then holding pressure for 5 minutes; boosting from 500T to 1500T for 1 minute and then holding pressure for 5 minutes; boosting from 1500T to 2500T for 1 minute and then holding pressure for 5 minutes; boosting from 2500T to 3000T for 1 minute and then holding pressure for 40 minutes before releasing pressure;

[0077] 4) Open the forging die, take out the formed titanium alloy casing refined 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°C for 2 h and air cool to room temperature.

[0079] Comparative Example 4

[0080] Superplastic forming method of engine casing:

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

[0082] 2) The mold is coated with a layer of glass lubricant and kept at 930°C for 4 hours;

[0083] 3) Place the blank into the mold and use a hydraulic press to die-cast it into the required casing shape at 930°C in one go, with the deformation controlled to 30%;

[0084] The average strain rate of the hydraulic press under this deformation is 0.00017s -1 The hydraulic press pressure boosting procedure is as follows: pressure change is: boosting to 500T for 2 minutes and then holding pressure for 5 minutes; boosting from 500T for 1 minute to 1500T and then holding pressure for 5 minutes; boosting from 1500T for 1 minute to 2500T and then holding pressure for 5 minutes; boosting from 2500T for 1 minute to 3000T and then holding pressure for 10 minutes before releasing pressure;

[0085] 4) The forging die is opened, the shaped titanium alloy engine case finish forging is taken out and moved to water within 20s for water cooling (water cooling flow rate 3m / s);

[0086] 5) The forging is annealed at 720℃, the annealing time is 2h, and after the treatment is finished, air cooling to room temperature.

[0087] Comparative Example 5

[0088] Superplastic forming method of engine case:

[0089] 1) The titanium alloy blank (Tβ=980℃) is coated with glass lubricant, the titanium alloy blank is heated to 930℃, the thickness of the titanium alloy blank H=1000mm, the heating time T1=1000×0.9s=900s;

[0090] 2) The die is coated with a layer of glass lubricant and kept at 700℃ for 4h;

[0091] 3) The blank is loaded into the die, and once pressure casting is performed at 930℃ using a hydraulic machine to form the required case shape, and the deformation amount is controlled to be 50%;

[0092] The strain rate of the hydraulic machine under this deformation amount is 0.00014s -1 ; The hydraulic machine pressure rising program is: the pressure changes to rise to 500T for 2min, keeps pressure for 5min, rises from 500T to 1500T for 1min, keeps pressure for 5min, rises from 1500T to 2500T for 1min, keeps pressure for 5min, rises from 2500T to 3000T, keeps pressure for 40min, and then releases pressure;

[0093] 4) The forging die is opened, the shaped titanium alloy engine case finish forging is taken out and moved to water within 20s for water cooling (water cooling flow rate 3m / s);

[0094] 5) The forging is annealed at 720℃, the annealing time is 2h, and after the treatment is finished, air cooling to room temperature.

[0095] The mechanical properties of each case prepared in Examples 1~2 and Comparative Examples 1~5 are tested according to GJB 2744A-2007 "Specification for Titanium and Titanium Alloy Forgings for Aviation", and the test results are shown in Table 1.

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

[0097] Tensile strength MPa Elongation% Sectional shrinkage% 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 2It can be seen from the table that the metallographic structure of the casing prepared in Example 1 is a typical equiaxed structure, the primary α phase content is greater than 60%, the α phase size is basically consistent and evenly distributed, the secondary α phase is small and flaky, and has a certain aspect ratio. Combined with the mechanical properties data in Table 1, it can be seen that the casing has high strength and plasticity and has excellent comprehensive performance. Figure 4 The metallographic structure of the casing prepared in Comparative Example 1 is a two-phase structure, with significantly lower primary α-phase content and equiaxed degree than in Example 1. The significant differences between the two structures result in substandard performance. The stepped pressure loading control technique 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. This stepped pressure loading control technique effectively increases the service life of forging dies and ensures precise forming and uniform microstructure of forgings.

[0099] Figure 3 It is shown that 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 properties of Example 1 and Comparative Example 1 in Table 1 shows that without the use of a gradient pressurization, excessively rapid pressurization would have resulted in a decrease in the tensile strength and elongation of the forging, and the high-temperature tensile strength did not meet the standards for use in a casing. This is because the lack of a gradient pressurization resulted in uneven microstructure distribution, an elongated primary α phase rather than an equiaxed one, and only a small amount of lamellar α phase, resulting in low plasticity and strength.

[0101] Comparing the mechanical properties of Example 1 and Comparative Example 2 in Table 1 shows that the use of air cooling after forging resulted in a decrease in the tensile strength of the forgings, and the high-temperature tensile strength did not meet the standards for use in casings. This is because air cooling, compared to water cooling, has a greater degree of undercooling, which prevents the precipitation of martensitic acicular structures. The primary α phase grows significantly, weakening the grain refinement strengthening effect, resulting in a decrease in tensile strength.

[0102] Comparing the mechanical property data of Example 1 and Comparative Example 3 in Table 1 shows that excessive forging deformation can lead to a decrease in the tensile strength and elongation of the forging, and the high-temperature tensile strength does not meet the standards for use in receivers. This is because while increasing deformation enhances dynamic recrystallization (DRX), leading to grain refinement (Hall-Petch effect) and improving strength, excessive deformation can lead to dislocation density saturation and even localized shear band formation, inducing microcracks and ultimately reducing strength. Moderate deformation (e.g., 50%-70%) promotes uniform recrystallization, forming fine equiaxed grains and enhancing plasticity. Excessive deformation (e.g., >70%) can hinder grain boundary sliding 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 critical deformation is not reached, the degree of recrystallization is insufficient, the size of the primary α phase does not change much, and the grain refinement is not obvious, resulting in substandard performance.

[0104] Comparing the mechanical properties of Example 1 and Comparative Example 5 in Table 1 shows that when the die and forging temperatures differ, the tensile strength and elongation of the forging decrease, and the high-temperature tensile strength fails to meet the standards for use in a casing. Maintaining the same die and billet temperature prevents temperature fluctuations from causing abnormal grain growth or the precipitation of harmful phases (such as ω phase), which can lead to material property degradation.

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

Claims

1. A method for precisely controlling the superplastic forming of a titanium alloy casing of an aero-engine, characterized in that: The following steps are involved: Preheating the titanium alloy billet to 30-60°C below its β-phase transformation temperature, and the time for preheating to the limited temperature is the thickness value H of the titanium alloy billet (0.6-0.9)s, wherein the thickness value H of the titanium alloy billet is measured in mm; Preheating the aircraft engine casing mold to be isothermal with the preheated titanium alloy blank; The preheated titanium alloy billet is placed in a preheated mold and subjected to a first-fire die-casting forging process at the preheating temperature. During the first-fire die-casting forging process, the deformation is controlled to be 50% to 70%, and the average strain rate is 0.0002 to 0.00025 s -1 The pressure changes are: increase the pressure for 2 minutes to 500T and then maintain the pressure for 5 minutes; increase the pressure from 500T for 1 minute to 1500T and then maintain the pressure for 5 minutes; increase the pressure from 1500T for 1 minute to 2500T and then maintain the pressure for 5 minutes; increase the pressure from 2500T for 1 minute to 3000T and then maintain the pressure for 20 minutes to 30 minutes before releasing the pressure; After the die-casting forging is completed, the forging is taken out and water-cooled within 20 seconds, and then annealed to obtain an aircraft engine titanium alloy casing.

2. The method for precisely controlling the superplastic forming of an aircraft engine titanium alloy casing according to claim 1, characterized in that: The titanium alloy blank is coated with glass lubricant on its surface before preheating; and the aircraft engine casing mold is coated with glass lubricant on its inner surface before preheating.

3. The method for precisely controlling the superplastic forming of an aircraft engine titanium alloy casing according to claim 1, characterized in that: The annealing temperature is 710-720° C., and the holding time is 2-5 hours.

4. The method for precisely controlling the superplastic forming of an aircraft engine titanium alloy casing according to claim 1, characterized in that: The flow rate of the water cooling is 2m / s~5m / s.

5. An aerospace engine titanium alloy casing manufactured according to the method for precisely controlling the superplastic forming of an aerospace engine titanium alloy casing according to any one of claims 1 to 4.

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