HIGH-EFFICIENCY SHORT-PROCESS SUPERPLASTIC FORMING METHOD FOR TC4 TITANIUM ALLOY FAN BLISK FORGING

Description

CROSS REFERENCE TO RELATED APPLICATION

This patent application claims the benefit and priority of Chinese Patent Application No. 202411783666.9, entitled “High-efficiency short-process superplastic forming method for TC4 titanium alloy fan blisk forging” filed on Dec. 6, 2024, the disclosure of which is incorporated by reference herein in its entirety as part of the present application.

TECHNICAL FIELD

The present disclosure belongs to the technical field of titanium alloy processing, and specifically relates to a high-efficiency short-process superplastic forming method for a TC4 titanium alloy fan blisk forging.

BACKGROUND

The development of science and technology is driving the rapid iteration of aircraft, and as the “heart” of the aircraft, the performance requirements of the engine are increasing. As a critical component of the aeroengine, the blisk is designed by integrating the blade and the wheel disc, which significantly reduces the rotor mass and improves the operational efficiency. This design not only directly reduces the weight of the engine, but also helps to reduce the airflow loss, thereby increasing the operational efficiency and thrust of the engine. This is essential for improving the flight performance and speed of aircraft. As a result, the blisk is widely used in modern high-performance aeroengines.

TC4 titanium alloy is a lightweight and high-strength metal material, which has become an ideal choice for the aerospace field in pursuit of lightweight design. However, conventional forming processes for TC4 titanium alloy have difficulties such as poor plasticity and a narrow forging temperature window, which leads to the easy formation of defects during the forming process. These issues not only limit comprehensive performance of the material but also adversely affect the production efficiency. Therefore, it is necessary to explore novel forming methods to optimize the processing procedures. Despite the poor processing performance, it has good plasticity and fluidity in the superplastic state, making it suitable for processing into complex shapes, and such characteristic could be utilized to achieve superplastic forming of TC4 titanium alloy.

CN113510207A discloses a method for manufacturing a large-size variable-cross-section TC17 titanium alloy blisk forging, including designing a forged blank based on the shape and size of parts, preparing final forging and pre-forging dies, processing a bar to form a bar blank, then transferring the bar blank to the pre-forging die to prepare into a pre-forged blank, and finally transferring the pre-forged blank to the final forging die to prepare into the forging.

CN110773685A discloses a method for manufacturing a thick and large variable-cross-section Ti-6242 alloy blisk forging, including subjecting a bar to forging to obtain an intermediate blank according to an actual noise level of the bar measured by ultrasonic, subjecting the intermediate blank to die forging to obtain a forged blank, and subjecting the forged blank to a heat treatment to obtain the blisk forging.

Due to the limitation of temperature drop during the conventional forging process, it is generally necessary to return the bar to a furnace for maintaining at the temperature again after upsetting and drawing in each heating-upsetting-drawing cycle. Therefore, the deformation during a single heating-upsetting-drawing cycle of the bar and the forming process of the forging is very limited.

SUMMARY

The present disclosure aims to provide a high-efficiency short-process superplastic forming method for a TC4 titanium alloy fan blisk forging, which fully utilizes the superplasticity of titanium alloy materials to realize super-large deformation in a single heating-upsetting-drawing cycle in a high-temperature deformation environment, which greatly improves the production efficiency, and also reduces the manufacturing cost and cycle, with significant economic and social benefits. The TC4 titanium alloy fan blisk forging at any part has room-temperature tensile properties of: a tensile strength ≥960 MPa, a yield strength ≥880 MPa, an elongation of ≥12.0%, and a section shrinkage ≥25%; the TC4 titanium alloy fan blisk forging at any part has elevated temperature tensile properties at 400° C. of: a tensile strength ≥650 MPa; an elongation ≥15%, and a section shrinkage ≥50%; and the TC4 titanium alloy fan blisk forging exhibits a room temperature impact work ≥28 J, and a fracture toughness ≥60 MPa·m^1/2.

In order to achieve the above object, the present disclosure provides the following technical solutions:

• • Provided is a superplastic forming method for TC4 titanium alloy fan blisk forgings, including or consisting of the steps of:
  • 1) performing vacuum consumable melting to obtain a TC4 titanium alloy ingot having a diameter of Φ820-Φ1020 mm;
  • 2) subjecting the TC4 titanium alloy ingot to forging through at least 3 heating-upsetting-drawing cycles, and after completion of forging through all the at least 3 heating-upsetting-drawing cycles, performing water-cooling to obtain a forged blank, wherein
  • the forging through 3 heating-upsetting-drawing cycles is performed as follows: first heating the TC4 titanium alloy ingot to a temperature of 1100-1200° C. and maintaining at the temperature for 10-15 hours, and taking a heated TC4 titanium alloy ingot out and performing a first upsetting and a first drawing; then returning to a furnace for maintaining at a temperature of 1100-1200° C. for 4-10 hours, and taking a resulting TC4 titanium alloy ingot out and performing a second upsetting and a second drawing; and then returning to the furnace for maintaining at a temperature of 940-980° C. for 2-6 hours, and taking an obtained TC4 titanium alloy ingot out and performing a third upsetting and a third drawing; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.5-0.1 s⁻¹;
  • 3) forging the forged blank through at least 3 heating-upsetting-drawing cycles, and after completion of forging through all the at least 3 heating-upsetting-drawing cycles, performing air-cooling, wherein
  • forging the forged blank through at least 3 heating-upsetting-drawing cycles is performed as follows: first heating the forged blank to a temperature of 1050-1100° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting and a first drawing; then returning to a furnace for heating to a temperature of 940-980° C. and maintaining temperature for 2-6 hours, and taking a resulting forged blank out and performing a second upsetting and a second drawing; and then returning to the furnace for heating to a temperature of 1050-1100° C. and maintaining temperature for 4-10 hours, and taking an obtained forged blank out and performing a third upsetting and a third drawing; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.05-0.005 s⁻¹;
  • 4) subjecting a resulted forged blank to 3-5 heating-upsetting-drawing cycles, and after completion of forging by all the 3-5 heating-upsetting-drawing cycles, performing air-cooling to room temperature to obtain a TC4 titanium alloy rod, wherein
  • the 3-5 heating-upsetting-drawing cycles are performed as follows: first heating the resulted forged blank to a temperature of 940-980° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting and a first drawing; in each subsequent heating-upsetting-drawing cycle, returning a resulting forged blank to a furnace for maintaining at the temperature of 940-980° C. for 2-6 hours, and taking a resulting forged blank out of the furnace, and performing an upsetting and a drawing; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.05-0.005 s⁻¹;
  • 5) spray-coating a glass lubricant onto a surface of the TC4 titanium alloy rod, and heating a coated TC4 titanium alloy rod to a temperature of T_β−(20-60)° C. within a heating time T; wherein the heating time T=D×(0.7-1.0), where T is in a unit of minute, and D represents a diameter of the TC4 titanium alloy rod and is in a unit of mm;
  • spray-coating the glass lubricant onto a contour surface of a blisk forming die, and heating a coated blisk forming die to a temperature of T_β−(20-60)° C. and then maintaining temperature;
  • loading a resulting TC4 titanium alloy rod into a resulting forming die, and performing one-heating forming at a forging pressure of 30-100 MN and a strain rate of 0.005-0.001 s⁻¹ with a deformation of 95% or more to obtain a TC4 titanium alloy fan blisk forging; and after completion of forming forging, water-cooling the TC4 titanium alloy fan blisk forging to room temperature; and
  • 6) subjecting a resulting TC4 titanium alloy fan blisk forging to an annealing treatment at a temperature of 650-750° C., and after the annealing treatment, air-cooling to room temperature.

In some embodiments, in steps 2) to 4) above, a deformation after heating to 1050-1200° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 60-75%, and a deformation after heating to 940-980° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 50-60%.

In an aspect, provided is a high-efficiency short-process superplastic forming method for a TC4 titanium alloy fan blisk forging, including:

• • 1) performing vacuum consumable melting to obtain a TC4 titanium alloy ingot having a diameter of Φ820-Φ1020 mm;
  • 2) subjecting the TC4 titanium alloy ingot to forging with 3 heating cycles, and after completion of forging with all the 3 heating-upsetting-drawing cycles, performing water-cooling to obtain a forged blank, wherein
  • the forging with 3 heating cycles is performed as follows: first heating the TC4 titanium alloy ingot to a temperature of 1100-1200° C. and maintaining at the temperature for 10-15 hours, and taking a heated TC4 titanium alloy ingot out and performing a first upsetting and a first drawing; then returning to a furnace for maintaining at a temperature of 1100-1200° C. for 4-10 hours, and taking a resulting TC4 titanium alloy ingot out and performing a second upsetting and a second drawing; and then returning to the furnace for maintaining at a temperature of 940-980° C. for 2-6 hours, and taking an obtained TC4 titanium alloy ingot out and performing a third upsetting and a third drawing; and
  • a strain rate in each heating cycle is in a range of 0.5-0.1 s⁻¹;
  • 3) forging the forged blank through 3 heating cycles, and after completion of forging through all the 3 heating cycles, performing air-cooling, wherein
  • forging the forged blank through 3 heating cycles is performed as follows: first heating the forged blank to a temperature of 1050-1100° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting and a first drawing; then returning to a furnace for heating to a temperature of 940-980° C. and maintaining temperature for 2-6 hours, and taking a resulting forged blank out and performing a second upsetting and a second drawing; and then returning to the furnace for heating to a temperature of 1050-1100° C. and maintaining temperature for 4-10 hours, and taking an obtained forged blank out and performing a third upsetting and a third drawing; and
  • a strain rate in each heating cycle is in a range of 0.05-0.005 s⁻¹;
  • 4) subjecting a resulted forged blank to 3-5 heating cycles, and after completion of forging by all the 3-5 heating cycles, performing air-cooling to room temperature to obtain a TC4 titanium alloy rod, wherein
  • the 3-5 heating cycles are performed as follows: first heating the resulted forged blank to a temperature of 940-980° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting and a first drawing; in each subsequent heating cycle, returning a resulting forged blank to a furnace for maintaining at the temperature of 940-980° C. for 2-6 hours, and taking a resulting forged blank out of the furnace, and performing an upsetting and a drawing; and
  • a strain rate in each heating cycle is in a range of 0.05-0.005 s⁻¹;
  • wherein in steps 2) to 4) above, a deformation after heating to 1050-1200° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 60-75%, and a deformation after heating to 940-980° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 50-60%;
  • 5) spray-coating a glass lubricant onto a surface of the TC4 titanium alloy rod, and heating a coated TC4 titanium alloy rod to a temperature of T_β−(20-60)° C. within a heating time T; wherein the heating time T=D×(0.7-1.0), where T is in a unit of minute, and D represents a diameter of the TC4 titanium alloy rod and is in a unit of mm;
  • spray-coating the glass lubricant onto a contour surface of a blisk forming die, and heating a coated blisk forming die to a temperature of T_β−(20-60)° C. and then maintaining temperature;
  • loading a resulting TC4 titanium alloy rod into a resulting forming die, and performing one-heating forming at a forging pressure of 30-100 MN and a strain rate of 0.005-0.001 s⁻¹ with a deformation of 95% or more to obtain a TC4 titanium alloy fan blisk forging; and after completion of forging, water-cooling the TC4 titanium alloy fan blisk forging to room temperature; and
  • 6) subjecting a resulting TC4 titanium alloy fan blisk forging to an annealing treatment at a temperature of 650-750° C., and after the annealing treatment, air-cooling to room temperature.

In another aspect, provided is a superplastic forming method for a TC4 titanium alloy fan blisk forging, including or consisting of:

• • 1) performing vacuum consumable melting to obtain a TC4 titanium alloy ingot having a diameter of Φ820-Φ1020 mm;
  • 2) subjecting the TC4 titanium alloy ingot to forging with 3 heating-upsetting-drawing cycles, and after completion of forging with all the 3 heating-upsetting-drawing cycles, performing water-cooling to obtain a forged blank, wherein
  • the forging with 3 heating-upsetting-drawing cycles is performed as follows: first heating the TC4 titanium alloy ingot to a temperature of 1100-1200° C. and maintaining at the temperature for 10-15 hours, and taking a heated TC4 titanium alloy ingot out and performing a first upsetting and a first drawing; then returning to a furnace for maintaining at a temperature of 1100-1200° C. for 4-10 hours, and taking a resulting TC4 titanium alloy ingot out and performing a second upsetting and a second drawing; and then returning to the furnace for maintaining at a temperature of 940-980° C. for 2-6 hours, and taking an obtained TC4 titanium alloy ingot out and performing a third upsetting and a third drawing; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.1-0.5 s⁻¹;
  • 3) forging the forged blank obtained in step 2) through 3 heating-upsetting-drawing cycles, and after completion of forging through all the 3 heating-upsetting-drawing cycles, performing air-cooling, wherein
  • forging the forged blank obtained in step 2) through 3 heating-upsetting-drawing cycles is performed as follows: first heating the forged blank obtained in step 2) to a temperature of 1050-1100° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting I and a first drawing II; then returning to a furnace for heating to a temperature of 940-980° C. and maintaining temperature for 2-6 hours, and taking a resulting forged blank out and performing a second upsetting I and a second drawing II; and then returning to the furnace for heating to a temperature of 1050-1100° C. and maintaining temperature for 4-10 hours, and taking an obtained forged blank out and performing a third upsetting I and a third drawing II; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.005-0.05 s⁻¹;
  • 4) subjecting a resulted forged blank obtained in step 3) to 3-5 heating-upsetting-drawing cycles, and after completion of forging by all the 3-5 heating-upsetting-drawing cycles, performing air-cooling to room temperature to obtain a TC4 titanium alloy rod, wherein
  • the 3-5 heating-upsetting-drawing cycles are performed as follows: first heating the resulted forged blank obtained in step 3) to a temperature of 940-980° C. and maintaining temperature for 10-15 hours, and taking a heated forged blank out and performing a first upsetting A and a first drawing B; in each subsequent heating-upsetting-drawing cycle, returning a resulting forged blank to a furnace for maintaining at the temperature of 940-980° C. for 2-6 hours, and taking a resulting forged blank out of the furnace, and performing an upsetting and a drawing; and
  • a strain rate in each heating-upsetting-drawing cycle is in a range of 0.005-0.05 s⁻¹;
  • wherein in steps 2) to 4) above, a deformation after heating to 1050-1200° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 60-75%, and a deformation after heating to 940-980° C. and maintaining temperature and/or returning to the furnace for maintaining temperature is in a range of 50-60%;
  • 5) spray-coating a glass lubricant onto a surface of the TC4 titanium alloy rod obtained in step 4), and heating a coated TC4 titanium alloy rod to a temperature of T_β−(20-60)° C. within a heating time T; wherein the heating time T=D×(0.7-1.0), where T is in a unit of minute, and D represents a diameter of the TC4 titanium alloy rod and is in a unit of mm, T_β represents a transformation temperature from R phase to a phase of the TC4 titanium alloy ingot;
  • spray-coating the glass lubricant onto a contour surface of a blisk forming die, and heating a coated blisk forming die to a temperature of T_β−(20-60)° C. and then maintaining temperature; and
  • loading a resulting TC4 titanium alloy rod into a resulting forming die, and performing one-heating forming at a forging pressure of 30-100 MN and a strain rate of 0.001-0.005 s⁻¹ with a deformation of 95% or more to obtain a TC4 titanium alloy fan blisk forging; and after completion of forging, water-cooling the TC4 titanium alloy fan blisk forging to room temperature; and
  • 6) subjecting a resulting TC4 titanium alloy fan blisk forging obtained in step 5) to an annealing treatment at a temperature of 650-750° C., and after the annealing treatment, air-cooling an annealed TC4 titanium alloy fan blisk forging to room temperature, thereby obtaining the TC4 titanium alloy fan blisk forging.

In some embodiments, in step 5), the TC4 titanium alloy fan blisk forging is water-cooled within 30 s after completion of forming forging, at a cooling rate of ≥5° C./min.

The prepared TC4 titanium alloy aeroengine blisk has a microstructure of an (α+β) two-phase region structure, comprising a primary a phase with a content of 40%-60% and a size ≤20 m; the TC4 titanium alloy fan blisk forging at any part has room-temperature tensile properties of: a tensile strength ≥960 MPa, a yield strength ≥880 MPa, an elongation ≥12.0%, and a section shrinkage ≥25%; the TC4 titanium alloy fan blisk forging at any part has elevated temperature tensile properties at 400° C. of: a tensile strength ≥650 MPa; an elongation ≥15%, and a section shrinkage ≥50%; the TC4 titanium alloy fan blisk forging exhibits a room temperature impact work ≥28 J, and a fracture toughness ≥60 MPa·m^1/2.

In the superplastic forming method of the present disclosure:

In the conventional forging process for forged blanks, after a deformation above T_β, continuous upsettings and drawings through multiple heating-upsetting-drawing cycles are generally carried out below T_β. The deformation is generally not large (30%-40%), and the effect on the grain breaking and refinement is slight.

In the method of the present disclosure, the TC4 titanium alloy ingot is subjected to forging through at least 3 heating-upsetting-drawing cycles in step 2), such that the structure of the TC4 titanium alloy ingot is sufficiently broken; the forged blank is subjected to forging through at least 3 heating-upsetting-drawing cycles in step 3), such that the broken structure in the ingot obtained from forging is further subjected to grain refinement and morphology alteration, to create conditions for the subsequent structure breaking; and the forged blank is subjected to upsetting and drawing through 3-5 heating-upsetting-drawing cycles in step 4) to achieve further grain refinement and obtain the desired bar structure of the forging.

In the present disclosure, the TC4 titanium alloy forged blank is designed to be subjected to three times of upsetting and drawing forging following maintaining at T_β or higher, such that the structure grain could be fully broken and refined. The principle is as follow: the first upsetting and drawing forging involves large-deformation upsetting and drawing at T_β or higher to break the coarse as-cast grains within the original ingot; after subsequent upsetting and drawing below T_β, the reserve distortion could increase the nucleation points for subsequent R grain nucleation. The second upsetting and drawing forging and the subsequent, large-deformation upsetting and drawing at T_β or higher both utilize the principle of phase transformation recrystallization to form R grains, which are deformed immediately below T_β to further refine the grains and allow the structure size to be smaller (for example, 20 μm or less), thus providing a good foundation for the subsequent one-heating forming. Since the final one-heating forming has limited adjustment effects on the structural morphology, which requires to have it well adjusted before the one-heating forming. In the existing conventional process, the upsetting and drawing in the single-phase region are not conducted twice or more times. However, in the method of the present disclosure, the upsetting and drawing combined with the isothermal forging process in steps 3) and 4) could control the structural morphology with a small number of heating-upsetting-drawing cycles.

The present disclosure also utilizes the superplasticity of the TC4 titanium alloy material to achieve deformation of almost 100%. Therefore, compared with the common die forging process with multiple heating-upsetting-drawing cycles and minor deformation, the one-heating forming of the present disclosure could save the time required for die assembly, heating, etc. during the forming forging process, and only one set of die is required to complete tasks that would typically require multiple sets of dies in common die forging process, thus greatly improving the efficiency and economic cost.

Compared with the conventional technology, embodiments of the present disclosure have the following beneficial effects.

For conventional forging at room temperature, permissible upsetting-drawing and forging deformation in each heating-upsetting-drawing cycle is limited due to a significant temperature drop. Moreover, the temperature varies between the core and the surface of the forged blank. Therefore, multi-heating forming is required, and the final control of the primary a phase content also needs to be guaranteed by a solid solution treatment. In the present disclosure, the feasibility of achieving super-large deformation under isothermal conditions is fully utilized, and the original structure is further broken by strictly controlling the strain rate and forging temperature during the upsetting and drawing of the rod as well as during the forging forming process, such that the primary a phase content is 40-60% and the size is ≤20 μm, which is beneficial to the comprehensive performance of the forging.

According to the method by the present disclosure, the overall economy of the whole process is better; the forged blank only undergoes 9-10 heating-upsetting-drawing cycles, which is combined with the large deformation in each heating-upsetting-drawing cycle, such that the refinement degree of structure is substantially comparable to that of conventional forging with more than 20 heating-upsetting-drawing cycles. The forging forming part undergoes one-heating forming by virtue of superplasticity, and when there is no temperature drop on the forging surface after deformation, water-cooling is carried out, such that the forming process is combined with the solid solution treatment, thereby greatly shortening manufacturing cycle and reducing manufacturing cost on the premise of ensuring the comparable product quality.

Existing conventional forgings do not adopt isothermal forging, resulting in temperature variations between the surface and core of the forged blank forged and exposed to air. For example, after forging at 960° C., the core temperature is 920° C. while the surface temperature falls to 860° C. The content of the primary a phase in the structure of a TC4 titanium alloy material ultimately needs to be controlled, which should be retained and reflected through water-cooling at the corresponding temperature. For example, when T_β=1000° C., 40% of the primary a phase could be retained when water-cooling is started from 960° C., and 70% of primary a phase could be obtained when water-cooling is started from 920° C. Conventional solid solution treatments involve reheating to a desired temperature, maintaining at the temperature to control the structure and then rapidly cooling it down. This process is also known as thermomechanical treatment.

According to the forging forming of the present disclosure, the one-heating forming is achieved by virtue of superplasticity, and after deformation, water-cooling is carried out, such that the forming process is combined with the solid solution treatment, such that the manufacturing cycle is greatly shortened and the manufacturing cost is reduced on the premise of ensuring the comparable product quality.

The TC4 titanium alloy aeroengine blisk prepared in the present disclosure has a microstructure of an (α+β) two-phase region structure, comprising a primary a phase with a content of 40%-60% and a size ≤20 μm; the TC4 titanium alloy fan blisk forging at any part has room-temperature tensile properties of: a tensile strength ≥960 MPa, a yield strength ≥880 MPa, an elongation ≥12.0%, and a section shrinkage ≥25%; the TC4 titanium alloy fan blisk forging at any part has elevated temperature tensile properties at 400° C. of: a tensile strength ≥650 MPa; an elongation ≥15%, and a section shrinkage ≥50%; and the TC4 titanium alloy fan blisk forging exhibits a room temperature impact work ≥28 J, and a fracture toughness ≥60 MPa·m^1/2.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a microstructure photograph of the TC4 titanium alloy fan blisk forging in Example 1 of the present disclosure.

FIG. 2 shows a microstructure photograph of the TC4 titanium alloy fan blisk forging in a comparative example of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Definition

In the disclosure, the expression “superplastic forming method” refers to an advanced metal forming process that utilizes the superplasticity exhibited by certain materials under specific conditions (high temperature and extremely low, stable strain rate), i.e., the characteristic of exhibiting abnormally high elongation (usually reaching 200% or more, even 1000%-2000%) without necking or fracture, which is commonly used to manufacture thin-walled parts with complex shapes, great integrity, and high precision.

In the disclosure, the terms “heating cycle” and “heating-upsetting-drawing cycle” have a same definition and could be interchangeable.

In the disclosure, the terms “first” and “second” do not include any information about sequence, amount, and are used to distinguish two terms.

In the disclosure, the term “T_β” refers to a transformation temperature from R phase to a phase of an alloy.

In the disclosure, the expression “a temperature of T_β−(20-60)° C.” means a temperature ranging from T_β−60° C. to T_β−20° C.

The disclosure will be further described below in conjunction with examples and the accompanying drawings.

The process parameters of the examples of the present disclosure are shown in Tables 1 and 2. The comprehensive performance test results of the examples and comparative examples of the present disclosure are shown in Table 3.

Test results of examples below shown in Table 3 were obtained by the performance test methods below.

• • Room-temperature tensile properties: determined according to GB/T228.1-2021.
  • Elevated temperature tensile properties at 400° C.: determined according to GB/T228.2-2015, using a sample with a working diameter of 5 mm.
  • Room temperature impact work: determined according to GB/T229-2020.
  • Fracture toughness K_IC: determined according to GB/T4161-2007.

Example 1

A TC4 titanium alloy fan blisk forging with a weigh of 580 kg, and T_β=1000° C. was prepared by using a superplastic forming method as follows:

• • 1) A TC4 titanium alloy ingot having a diameter of Φ920 mm was obtained by performing vacuum consumable melting.
  • 2) The TC4 titanium alloy ingot was forged through 3 heating-upsetting-drawing cycles as follows: the ingot was first heated to 1150° C. and maintained at 1150° C. for 13 hours, and then taken out and subjected to a first upsetting and a first drawing, with a deformation of 70%; the resulting ingot was returned to a furnace for maintaining at a temperature of 1150° C. for 7 h, and then taken out and subjected to a second upsetting and a second drawing, with a deformation of 70%; a resulting ingot was returned to the furnace for maintaining at a temperature of 960° C. for 4 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 55%, where a strain rate in each heating-upsetting-drawing cycle was 0.3 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, the resulting forged product was water-cooled to obtain a forged blank.
  • 3) The forged blank was forged through 3 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 1080° C. and maintained for 12 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 72%; the resulting blank was then returned to a furnace for heating to a temperature of 960° C. and maintaining at 960° C. for 4 h, and taken out and subjected to a second upsetting and a second drawing, with a deformation of 55%; the resulting blank was then returned to the furnace for heating to a temperature of 1080° C. and maintaining at 1080° C. for 7 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 70%, where a strain rate in each heating-upsetting-drawing cycle was 0.02 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled.
  • 4) A resulting forged blank was subjected to 4 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 960° C. and maintained for 12 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 55%; in each subsequent heating-upsetting-drawing cycle, a resulting product was returned to a furnace for maintaining at 960° C. for 4 h, and then taken out and subjected to an upsetting and a drawing, with a deformation of 55%; where a strain rate in each heating-upsetting-drawing cycle was 0.02 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled to room temperature to obtain a TC4 titanium alloy rod.
  • 5) A glass lubricant was spray-coated onto a surface of the TC4 titanium alloy rod, followed by heating to 960° C. within 320 minutes. The glass lubricant was spray-coated onto a contour surface of a blisk forming die, followed by heating to 960° C. and then maintaining at 960° C. The TC4 titanium alloy rod was loaded into the blisk forming die, and then subjected to one-heating forming at a forging pressure of 80 MN and a strain rate of 0.002 s⁻¹ with an ultra-large deformation of 96% to obtain a TC4 titanium alloy fan blisk forging. After completion of the forging, the TC4 titanium alloy fan blisk forging was water-cooled to room temperature at a cooling rate of 6° C./min.
  • 6) The TC4 titanium alloy fan blisk forging was subjected to an annealing treatment at 700° C., and after the annealing treatment, an annealed TC4 titanium alloy fan blisk forging was air-cooled to room temperature.

Example 2

A TC4 titanium alloy fan blisk forging with a weigh of 800 kg, and T_β=1006° C. was prepared by using a superplastic forming method as follows:

• • 1) A TC4 titanium alloy ingot having a diameter of Φ1020 mm was obtained by performing vacuum consumable melting.
  • 2) The TC4 titanium alloy ingot was forged through 3 heating-upsetting-drawing cycles as follows: the ingot was first heated to 1200° C. and maintained at 1200° C. for 15 hours, and then taken out and subjected to a first upsetting and a first drawing, with a deformation of 75%; the resulting ingot was returned to a furnace for maintaining at a temperature of 1200° C. for 10 h, and then taken out and subjected to a second upsetting and a second drawing, with a deformation of 75%; the resulting ingot was returned to the furnace for maintaining at a temperature of 980° C. for 6 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 60%, where a strain rate in each heating-upsetting-drawing cycle was 0.5 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, the resulting forged product was water-cooled to obtain a forged blank.
  • 3) The forged blank was forged through 3 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 1100° C. and maintained for 15 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 75%; the resulting blank was then returned to a furnace for heating to a temperature of 980° C. and maintaining at 980° C. for 6 h, and taken out and subjected to a second upsetting and a second drawing, with a deformation of 60%; the resulting blank was then returned to the furnace for heating to a temperature of 1100° C. and maintaining at 1100° C. for of 10 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 75%, where a strain rate in each heating-upsetting-drawing cycle was 0.05 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled.
  • 4) A resulting forged blank was subjected to upsetting and drawing through 5 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 980° C. and maintained for 15 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 60%; in each subsequent heating-upsetting-drawing cycle, a resulting product was returned to a furnace for maintaining at 980° C. for 6 h, and then taken out and subjected to an upsetting and a drawing, with a deformation of 60%; where a strain rate in each heating-upsetting-drawing cycle was 0.05 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled to room temperature to obtain a TC4 titanium alloy rod.
  • 5) A glass lubricant was spray-coated onto a surface of the TC4 titanium alloy rod, followed by heating to 986° C. within 480 minutes. The glass lubricant was spray-coated onto a contour surface of a blisk forming die, followed by heating to 986° C. and then maintaining at 986° C. The TC4 titanium alloy rod was loaded into the blisk forming die, and then subjected to one-heating forming at a forging pressure of 100 MN and a strain rate of 0.005 s⁻¹ with an ultra-large deformation of 95% to obtain a TC4 titanium alloy fan blisk forging. After completion of the forging, the TC4 titanium alloy fan blisk forging was water-cooled to room temperature at a cooling rate of 7° C./min.
  • 6) The TC4 titanium alloy fan blisk forging was subjected to an annealing treatment at 750° C., and after the annealing treatment, an annealed TC4 titanium alloy fan blisk forging was air-cooled to room temperature.

Example 3

A TC4 titanium alloy fan blisk forging with a weigh of 400 kg, and T_β=995° C. was prepared by using a superplastic forming method as follows:

• • 1) A TC4 titanium alloy ingot having a diameter of Φ820 mm was obtained by performing vacuum consumable melting.
  • 2) The TC4 titanium alloy ingot was forged through 3 heating-upsetting-drawing cycles as follows: the ingot was first heated to 1100° C. and maintained at 1100° C. for 10 hours, and then taken out and subjected to a first upsetting and a first drawing, with a deformation of 60%; the resulting ingot was returned to a furnace for maintaining at a temperature of 1100° C. for 4 h, and then taken out and subjected to a second upsetting and a second drawing, with a deformation of 60%; the resulting ingot was returned to the furnace for maintaining at a temperature of 940° C. for 2 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 50%, where a strain rate in each heating-upsetting-drawing cycle was 0.1 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, the resulting forged product was water-cooled to obtain a forged blank.
  • 3) The forged blank was forged through 3 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 1050° C. and maintained for 10 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 60%; the resulting blank was then returned to a furnace for heating to a temperature of 940° C. and maintaining at 940° C. for 2 h, and taken out and subjected to a second upsetting and a second drawing, with a deformation of 50%; the resulting blank was then returned to the furnace for heating to a temperature of 1050° C. and maintaining at 1050° C. for of 4 h, and taken out and subjected to a third upsetting and a third drawing, with a deformation of 60%, where a strain rate in each heating-upsetting-drawing cycle was 0.005 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled.
  • 4) A resulting forged blank was subjected to upsetting and drawing through 3 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 940° C. and maintained for 10 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 50%; in each subsequent heating-upsetting-drawing cycle, a resulting product was returned to a furnace for maintaining at 940° C. for 2 h, and then taken out and subjected to an upsetting and a drawing, with a deformation of 50%; where a strain rate in each heating-upsetting-drawing cycle was 0.005 s⁻¹. After completion of forging through all the heating-upsetting-drawing cycles, a resulting forged product was air-cooled to room temperature to obtain a TC4 titanium alloy rod.
  • 5) A glass lubricant was spray-coated onto a surface of the TC4 titanium alloy rod, followed by heating to 935° C. within 280 minutes. The glass lubricant was spray-coated onto a contour surface of a blisk forming die, followed by heating to 935° C. and then maintaining at 935° C. The TC4 titanium alloy rod was loaded into the blisk forming die, and then subjected to one-heating forming at a forging pressure of 30 MN and a strain rate of 0.001 s⁻¹ with an ultra-large deformation of 97% to obtain a TC4 titanium alloy fan blisk forging. After completion of the forging, the TC4 titanium alloy fan blisk forging was water-cooled to room temperature at a cooling rate of 5° C./min.
  • 6) The TC4 titanium alloy fan blisk forging was subjected to an annealing treatment at 650° C., and after the annealing treatment, an annealed TC4 titanium alloy fan blisk forging was air-cooled to room temperature.

Comparative Example

A TC4 titanium alloy fan blisk forging with a weigh of 580 kg, and T_β=1000° C. was prepared by using a forming method as follows:

• • 1) A TC4 titanium alloy ingot having a diameter of Φ920 mm was obtained by performing vacuum consumable melting.
  • 2) The TC4 titanium alloy ingot was forged through 5 heating-upsetting-drawing cycles as follows: the ingot was first heated to 1150° C. and maintained at 1150° C. for 15 hours, and then taken out and subjected to a first upsetting and a first drawing, with a deformation of 40% for each heating-upsetting-drawing cycle; the resulting ingot was returned to a furnace for maintaining at a temperature of 1150° C. for 4 h, and then taken out and subjected to a second upsetting and a second drawing, with a deformation of 40% for each heating-upsetting-drawing cycle; the resulting ingot was returned to the furnace for maintaining at a temperature of 960° C. for 2 h, and taken out and subjected to a 3-5 heating-upsetting-drawing cycles, with a deformation of 30% for each upsetting and drawing, where a strain rate in each heating-upsetting-drawing cycle was 0.5 s⁻¹. After completion of forging through all the 5 heating-upsetting-drawing cycles, the resulting forged product was water-cooled to obtain a forged blank.
  • 3) The forged blank was forged through 15 heating-upsetting-drawing cycles as follows: the forged blank was first heated to 960° C. and maintained at 960° C. for 15 h, and taken out and subjected to a first upsetting and a first drawing, with a deformation of 40% for each heating-upsetting-drawing cycle; the resulting blank was then returned to a furnace for heating to a temperature of 960° C. and maintaining at 960° C. for 2 h, and taken out and subjected to a deformation upsetting and a drawing, with a deformation of 40% for each heating-upsetting-drawing cycle, where a strain rate was 0.05 s⁻¹. After completion of the upsetting and the drawing, a resulting forged product was air-cooled to obtain a TC4 titanium alloy rod.
  • 4) A glass lubricant was spray-coated onto a surface of the TC4 titanium alloy rod, and a coated TC4 titanium alloy rod was subjected to die-forging forming through at least 3 heating-upsetting-drawing cycles. For each heating-upsetting-drawing cycle, heating to 960° C. within 380 min was performed, and a deformation of 40% at a strain rate of 0.05 s⁻¹ was achieved, to obtain a TC4 titanium-alloy fan blisk forging. After completion of the forging, the TC4 titanium alloy fan blisk forging was air-cooled to room temperature.
  • 5) A resulting TC4 titanium alloy fan blisk forging obtained in step 4) was heated to 960° C. and maintained at 960° C. for 2 h for a solid solution treatment, followed by water-cooling to room temperature at a cooling rate of 6° C./min.
  • 6) A resulting TC4 titanium alloy fan blisk forging was subjected to an annealing treatment at 700° C., and after the annealing treatment, a resulting annealed product was air-cooled to room temperature.

As can be seen from the above examples and comparative examples combined with Tables 1-3, the weight and size of the blisk, T_β of the material thereof, and heating number of upsetting and drawing in comparative example are exactly the same as those in Example 1, but after the first forging at a temperature above T_β, the subsequent upsettings and deformations are conducted below T_β, and the final blisk forming process adopts common die forging multiple times.

By contrast, in Example 1, the forged blank production involved a total number of 10 heating-upsetting-drawing cycles, and the forging was subjected to die-forging forming through one heating-upsetting-drawing cycle. In the comparative example, the forged blank production involved a total number of 20 heating-upsetting-drawing cycles, and the forging was subjected to die-forging forming through not less than 3 heating-upsetting-drawing cycles. Compared with the comparative example, the total number of heating-upsetting-drawing cycles during production in Example 1 of the present disclosure was reduced by about 50%, and the mechanical properties of forgings produced by the two processes were substantially comparable.

FIG. 1 shows a microstructure photograph of the TC4 titanium alloy fan blisk forging in Example 1 of the present disclosure; FIG. 2 shows a microstructure photograph of the TC4 titanium alloy fan blisk forging in comparative example. As shown in FIGS. 1 and 2, the microstructure of the blisk forging in Example 1 is essentially identical to that in the comparative example, but the total number of heating-upsetting-drawing cycles for production in Example 1 of the present disclosure is reduced by around 500 compared with that in the comparative example.

Finally, it should be noted that the above embodiments are only intended to illustrate the technical solutions of the present disclosure but not to limit the scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those ordinary skilled in the art should understand that modifications or equivalent substitutions may be made to the technical solutions of the present disclosure without departing from the essence or the scope of the technical solutions of the present disclosure.