Regulation and control method for improving consistency of high-temperature fatigue performance of titanium alloy forging stock based on effective strain
By optimizing the heat treatment process through finite element simulation, the effective strain distribution of titanium alloy forging billets was controlled, which solved the problem of non-uniformity of internal structure and properties in large-size forgings, improved the consistency of high-temperature fatigue performance, and made them suitable for aero-engine manufacturing.
Patent Information
- Application Number
- CN202511479325.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-16
- Publication Date
- 2026-01-09
AI Technical Summary
During the hot working and heat treatment of large-size titanium alloy forgings, the inhomogeneity of internal structure and properties, especially the consistency of high-temperature fatigue performance, is difficult to control, resulting in differences in microstructure and unstable mechanical properties, as well as high testing costs and high defect sensitivity.
By quantitatively correlating process parameters with the internal strain distribution of the forging billet through finite element simulation, the hot working and heat treatment processes are optimized, the effective strain distribution is controlled, and specific heat treatment regimes are adopted, including hot deformation processes of single-fire upsetting or multi-fire drawing + upsetting, combined with high-temperature solution treatment and strengthening treatment, to ensure the uniformity of the microstructure of the forging billet.
It achieves a significant and consistent improvement in the high-temperature fatigue performance of large-size titanium alloy forgings, reduces production costs and energy consumption, and is suitable for the manufacture of high-performance disc forgings for large aero-engines.
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Figure CN121295061A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of titanium alloy material processing technology, specifically to a method for combined control of hot working and heat treatment to improve the consistency of high-temperature fatigue performance of large-size titanium alloy forgings by controlling the effective strain distribution. Background Technology
[0002] Titanium alloys are widely used in a wide range of fields, including aerospace, medical and chemical industries, and energy, due to their superior specific strength, high specific stiffness, excellent high-temperature resistance, and corrosion resistance. Particularly in advanced aero engines, the use of titanium alloys plays a crucial role in improving engine thrust-to-weight ratio and aircraft maneuverability, with high-temperature titanium alloys being particularly important as key high-temperature structural materials.
[0003] With the continuous advancement of aero-engine technology, higher requirements have been placed on high-temperature titanium alloy components, including high-temperature resistance, large size, and integrated design. The manufacture of large-size high-temperature titanium alloy integral bladed disk forgings has become the main approach to meeting these requirements. Integral bladed disk structures significantly improve efficiency and reliability by reducing connecting parts and weight, characterized by a non-mechanically integrated design of the turbine disk and drum. This structure is typically achieved using an integral forging process. However, with the increase in the size of components and their forging blanks, higher demands are placed on the microstructure and property uniformity of large-size, thick-section forgings.
[0004] Controlling the microstructure and property uniformity of large-size, thick-section titanium alloy forgings has long been a major challenge in this field. On the one hand, with the increase in forging size, the internal deformation amount and deformation rate distribution during hot working may become uneven, especially in thick-section areas where localized insufficient strain or strain concentration is prone to occur. On the other hand, during the heat treatment of large-size forgings, the uneven temperature distribution across the cross-section leads to differences in holding time and cooling rate. Under the combined influence of multiple factors, the microstructure (such as α-phase morphology, grain size, macro / micro texture, etc.) shows significant differences at different locations, thus affecting the consistency of mechanical properties. High-temperature fatigue performance is particularly sensitive to microstructure, with significant differences in fatigue performance at different locations. Furthermore, the high cost of testing and strong defect sensitivity make consistency control difficult. Summary of the Invention
[0005] The purpose of this invention is to provide a control method for improving the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain. This method uses finite element simulation to quantitatively correlate process parameters with the strain distribution inside the forging, optimizes the process with key strain indicators as the guide, and combines a specific heat treatment regime to achieve homogenization of microstructure and properties.
[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for controlling the uniformity of high-temperature fatigue properties of titanium alloy forgings based on effective strain includes the following steps: (1) Billet preparation: Select forged or α+β heat-treated titanium alloy bars or disc forgings with an equivalent diameter ≥300mm; (2) Process simulation and optimization: The hot deformation process of the forging billet is simulated using finite element simulation software. The optimization target is that the volume of the difficult-to-deform region with a cumulative effective strain ≥1.3mm / mm along the diameter direction of the core of the forging billet after deformation and a cumulative effective strain <0.5mm / mm is less than 20% of the total volume. The final hot deformation process is determined, which is single-fire upsetting or multi-fire drawing + upsetting. (3) Hot deformation treatment: Heat the forging billet to 80~40℃ below the α+β / β phase transformation point, hold it at the temperature, and then carry out forging deformation according to the hot deformation process determined in step (2). The final forging temperature is controlled at 150℃ below the phase transformation point, and the forging is air-cooled to room temperature after forging. (4) High temperature solution treatment: Heat the hot-deformed forging billet to 40~10℃ below the α+β / β phase transformation point, hold for 1~5 hours, and then quench it in water or oil after taking it out of the furnace. (5) Strengthening treatment: Heat the solution-treated forging billet to 600~750℃, hold for 2~50 hours, and then air cool, furnace cool or temperature controlled cool to room temperature.
[0007] Furthermore, the titanium alloy mentioned in step (1) is a near-α type high-temperature titanium alloy, including Ti55, Ti60 or Ti65 alloy.
[0008] Furthermore, the nominal strain of the single-fire upsetting process in step (2) is controlled at 40%~80%.
[0009] Furthermore, in step (2), the nominal strain of upsetting in the multi-fire drawing and upsetting process is controlled at 40%~80%.
[0010] Furthermore, the heating in steps (3), (4) and (5) is carried out in a resistance furnace with a furnace temperature control accuracy of ±10℃.
[0011] Furthermore, in step (3), the heating rate of the forging billet does not exceed 10℃ / min, and the holding time is 0.5~1.5 hours.
[0012] Furthermore, the single-fire upsetting deformation described in step (3) adopts a two-step upsetting method: first, 50% of the deformation is carried out in the first step, then the forging billet is rotated 180°, and the remaining deformation is carried out until the target size is reached.
[0013] The beneficial effects of this invention are: (1) Quantitative control: For the first time, the core quantitative indicators of process optimization were proposed, namely “cumulative effective strain in the core ≥ 1.3 mm / mm” and “volume of difficult deformation zone < 20%”, so that process design can move from experience to science and ensure the sufficiency and uniformity of deformation.
[0014] (2) Significantly improved performance consistency: By ensuring full deformation of the core, the coarse strip-shaped primary α phase is effectively broken. Combined with optimized heat treatment, the microstructure of the entire forging billet is made uniform and consistent, thereby significantly narrowing the fluctuation range of high temperature fatigue life.
[0015] (3) Cost and efficiency optimization: By using finite element simulation for accurate prediction, we avoid blindly conducting multiple trials and multiple forging processes. While ensuring quality, we reduce the number of forging processes, thereby reducing energy consumption and production costs.
[0016] (4) Strong applicability: This method is specifically designed for the uniformity problem of large-size thick cross-section forging blanks with a diameter ≥ 300mm. It has obvious technical advantages and provides a reliable billet pretreatment solution for the manufacturing of high-performance large disc forgings for aero engines. Attached Figure Description
[0017] Figure 1 This is an effective strain distribution cloud map of the Ti60 alloy forging billet after single-fire upsetting deformation in an embodiment of the present invention.
[0018] Figure 2 These are forged microstructure photographs of Ti60 alloy forging billets that have not been controlled by the method of this invention.
[0019] Figure 3 These are micrographs of the heat-treated Ti60 alloy forging billet that has not been controlled by the method of this invention.
[0020] Figure 4 These are micrographs of the heat-treated Ti60 alloy forging billet with accumulated effective strain in the range of 1.31~1.5 mm / mm after being regulated by the method of this invention.
[0021] Figure 5 These are micrographs of the heat-treated Ti60 alloy forging billet with accumulated effective strain in the range of 0.563~0.75 mm / mm after being controlled by the method of this invention. Detailed Implementation
[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.
[0023] This embodiment addresses the design requirements for the microstructure and key properties of large-size high-temperature titanium alloy forgings used in advanced aero-engines. It proposes a combined control method of hot working and heat treatment to improve the consistency of high-temperature fatigue performance of large-size titanium alloy forgings by controlling the effective strain distribution. By establishing a quantitative relationship between the effective strain inside the forging and its high-temperature fatigue performance, and combining finite element simulation technology to predict the effective strain distribution during the hot working process of the forging, the process parameters are optimized according to the target performance requirements, thereby formulating an economical and effective hot working and heat treatment process.
[0024] The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain, as described in this embodiment, includes the following steps: (1) Preparation of billet; Bars or disc-shaped forgings of near-α type high-temperature titanium alloys such as Ti55, Ti60, and Ti65 are selected, in the forged state or α+β heat-treated state, with an equivalent diameter ≥300mm. Their microstructure at high and low magnification should meet the relevant requirements of GJB2220A-2018 standard.
[0025] (2) Process simulation and optimization; Use finite element software (such as Deform-3D) to build a thermal deformation model.
[0026] First, a single-fire upsetting process is simulated, with the nominal strain controlled between 40% and 80%. Analyzing the simulation results, if the cumulative effective strain along the diameter direction of the forging core is ≥1.3 mm / mm, and the volume ratio of the difficult-to-deform zone (effective strain <0.5 mm / mm) is <20%, then this process is adopted.
[0027] If the above strain conditions are not met, add a "drawing + upsetting" process step and re-simulate until the target is met. The nominal strain of the upsetting step is also controlled between 40% and 80%.
[0028] (3) Heat deformation treatment; The forged billet is heated in an electric resistance furnace to 80~40℃ below the α+β / β phase transformation point, with a heating rate ≤10℃ / min, and held at that temperature for 0.5~1.5 hours after being fully heated.
[0029] Perform the hot deformation process determined in step (2) on a hydraulic press or oil press. For single-fire upsetting, use a two-step upsetting method, with 50% deformation in each step and a 180° rotation in the middle. For multi-fire processes, perform elongation and two-step upsetting in sequence.
[0030] Control the final forging temperature to be no less than 150°C below the phase transformation point, and air-cool the forged billet to room temperature after forging.
[0031] (4) High-temperature solution treatment; Place the forging billet in a resistance furnace and heat it to 40~10℃ below the α+β / β phase transformation point. Hold it at that temperature for 1~5 hours, and then quickly quench it in water or oil after removing it from the furnace.
[0032] (5) Enhanced treatment; After solution treatment, the forging billet is placed back into the resistance furnace and heated to 600~750℃. It is held for 2~50 hours. After the holding period, it is cooled to room temperature by air cooling, furnace cooling or temperature-controlled cooling.
[0033] Taking a certain batch of Ti60 high-temperature titanium alloy as an example, its α+β / β phase transformation point is 1040℃. The raw material is a forged bar with a diameter of 304mm and a thickness of 140mm, and the microstructure conforms to the GJB2220A-2018 standard.
[0034] Process simulation: Deform-3D software was used to simulate single-fire upsetting at 980℃ (60℃ below the phase transformation point), with a nominal strain of approximately 50% (from 140mm upsetting to 70mm thickness). Simulation results showed that the cumulative effective strain along the diameter direction in the core of the forging billet reached 1.31~1.5mm / mm, and the volume fraction of the difficult-to-deform zone was less than 20%, meeting the target; thus, the single-fire upsetting process was determined.
[0035] Hot deformation treatment: The bar stock is heated to 980℃ in an electric resistance furnace at a rate of 10℃ / min and held for 120 minutes. Two-step upsetting is then performed on a press: first, the stock is upset to a thickness of 102mm, then the forging is rotated 180° and upset again to a final thickness of 70mm, resulting in a billet with a diameter of approximately 430mm. The final forging temperature is above 890℃, followed by air cooling.
[0036] Φ8.5mm×54mm bar samples were cut along the chord direction of the forging billet at different locations (13mm, 39mm, 65mm, 79mm, 112mm, and 139mm from the edge). The hot deformation process was simulated using Deform-3D finite element simulation software. The cumulative effective strain ranges at these locations were found to be 0.375~0.563mm / mm, 0.563~0.75mm / mm, 0.75~0.938mm / mm, 0.938~1.13mm / mm, 1.13~1.31mm / mm, and 1.31~1.5mm / mm, respectively. Figure 1 As shown, after a single upsetting deformation of a forging billet, the effective strain distribution inside the billet is as follows: the effective strain accumulated in the core of the billet along the diameter direction gradually decreases, and there are difficult-to-deform zones on the upper and lower surfaces.
[0037] High-temperature solution treatment: Heat the blank to 1020℃ (20℃ below the phase transformation point) and hold for 2 hours, then remove from the furnace and water quench (WQ).
[0038] Intensification treatment: Hold at 700℃ for 8 hours, then air cool (AC) after removal from the furnace.
[0039] Comparison: Bar samples from different locations were treated using four different heat treatment processes: 1025℃ / 2h, WQ+700℃ / 8h, AC; 1020℃ / 2h, WQ+700℃ / 8h, AC; 1015℃ / 2h, WQ+700℃ / 8h, AC; 1010℃ / 2h, WQ+700℃ / 8h, AC.
[0040] The specimen was then processed into a rotational bending fatigue specimen and tested at a temperature of 600℃, a stress ratio of -1, a sine wave waveform, a test frequency of 83Hz, and a maximum stress of 380N / mm². 2 The high-temperature fatigue performance was tested under the following conditions. Table 1 shows the high-temperature fatigue performance after different heat treatment regimes and different effective strain deformations. The test results are shown in Table 1. The fatigue life at all sampling locations far exceeds the standard requirement of 5×10⁻⁶. 7 The fatigue life data is concentrated and highly consistent, with a high degree of uniformity. Two heat treatment processes, 1020℃ / 2h, WQ+700℃ / 8h, AC and 1015℃ / 2h, WQ+700℃ / 8h, AC, significantly improved fatigue life and demonstrated significant advantages in optimizing the fatigue performance of large-size titanium alloy forgings. This is particularly evident in regions with cumulative effective strain ≥1.31mm / mm, such as... Figure 4 As shown, the primary α phase is fine and uniform, exhibiting excellent and stable fatigue performance. This is consistent with the low strain region ( Figure 5 ) and uncontrolled forging structure ( Figure 2 and Figure 3 This presents a stark contrast.
[0041] Table 1 Fatigue life of Ti60 alloy forgings under different effective strains and heat treatment conditions. Heat treatment state Effective strain, mm / mm Fatigue life, weeks Standard, Week 1025℃ / 2h, WQ+700℃ / 8h, AC 0.375~0.563 2733707 <![CDATA[5×10 8 ]]> 1025℃ / 2h, WQ+700℃ / 8h, AC 0.563~0.75 13198083 <![CDATA[5×10 8 ]]> 1025℃ / 2h, WQ+700℃ / 8h, AC 0.75~0.938 >50000000 <![CDATA[5×10 8 ]]> 1025℃ / 2h, WQ+700℃ / 8h, AC 0.938~1.13 2872591 <![CDATA[5×10 8 ]]> 1025℃ / 2h, WQ+700℃ / 8h, AC 1.13~1.31 921509 <![CDATA[5×10 8 ]]> 1025℃ / 2h, WQ+700℃ / 8h, AC 1.31~1.5 >50000000 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 0.375~0.563 >50000000 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 0.563~0.75 >50000000 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 0.75~0.938 88059114 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 0.938~1.13 99343662 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 1.13~1.31 >50000000 <![CDATA[5×10 8 ]]> 1020℃ / 2h, WQ+700℃ / 8h, AC 1.31~1.5 >50000000 <![CDATA[5×10 8 ]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 0.375~0.563 3743259 <![CDATA[5×10 8 ]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 0.563~0.75 57286495 <![CDATA[5×10 8 <!-- 4 -->]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 0.75~0.938 37584025 <![CDATA[5×10 8 ]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 0.938~1.13 57805294 <![CDATA[5×10 8 ]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 1.13~1.31 104184965 <![CDATA[5×10 8 ]]> 1015℃ / 2h, WQ+700℃ / 8h, AC 1.31~1.5 105605630 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 0.375~0.563 28561 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 0.563~0.75 6003656 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 0.75~0.938 8418052 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 0.938~1.13 470414 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 1.13~1.31 92109 <![CDATA[5×10 8 ]]> 1010℃ / 2h, WQ+700℃ / 8h, AC 1.31~1.5 55526260 <![CDATA[5×10 8 ]]>
[0042] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for controlling the consistency of high-temperature fatigue properties of titanium alloy forgings based on effective strain, characterized in that, Includes the following steps: (1) Billet preparation: Select forged or α+β heat-treated titanium alloy bars or disc forgings with an equivalent diameter ≥300mm; (2) Process simulation and optimization: The hot deformation process of the forging billet is simulated using finite element simulation software. The optimization target is that the volume of the difficult-to-deform region with a cumulative effective strain ≥1.3mm / mm along the diameter direction of the core of the forging billet after deformation and a cumulative effective strain <0.5mm / mm is less than 20% of the total volume. The final hot deformation process is determined, which is single-fire upsetting or multi-fire drawing + upsetting. (3) Hot deformation treatment: Heat the forging billet to 80~40℃ below the α+β / β phase transformation point, hold it at the temperature, and then carry out forging deformation according to the hot deformation process determined in step (2). The final forging temperature is controlled at 150℃ below the phase transformation point, and the forging is air-cooled to room temperature after forging. (4) High temperature solution treatment: Heat the hot-deformed forging billet to 40~10℃ below the α+β / β phase transformation point, hold for 1~5 hours, and then quench it in water or oil after taking it out of the furnace. (5) Strengthening treatment: Heat the solution-treated forging billet to 600~750℃, hold for 2~50 hours, and then air cool, furnace cool or temperature controlled cool to room temperature.
2. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, The titanium alloy mentioned in step (1) is a near-α type high-temperature titanium alloy, including Ti55, Ti60 or Ti65 alloy.
3. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, In step (2), the nominal strain of the single-fire upsetting process is controlled at 40% to 80%.
4. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, In step (2), the nominal strain of upsetting in the multi-fire drawing and upsetting process is controlled at 40%~80%.
5. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, The heating in steps (3), (4) and (5) is carried out in a resistance furnace with a furnace temperature control accuracy of ±10℃.
6. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, The heating rate of the forging billet in step (3) shall not exceed 10℃ / min, and the holding time shall be 0.5~1.5 hours.
7. The method for controlling the consistency of high-temperature fatigue performance of titanium alloy forgings based on effective strain according to claim 1, characterized in that, The single-fire upsetting deformation described in step (3) adopts a two-step upsetting method: first, 50% of the deformation is carried out in the first step, then the forging billet is rotated 180°, and the remaining deformation is carried out until the target size is reached.