A method for optimizing fatigue performance of TC11 forged titanium alloy

Abstract

The application discloses a kind of TC11 forging titanium alloy fatigue performance optimization method, belong to metal material fatigue performance optimization technical field.The method is to the forging state TC11 titanium alloy is carried out two-phase zone solid solution aging or double annealing heat treatment to improve fatigue strength.The two-phase zone solid solution aging heat treatment: first at temperature T1 or T2 processing 1h, water quenching (WQ);Again at 530 DEG C processing 6h, air cooling (AC);The two-phase zone double annealing heat treatment: first at temperature T3 or T4 processing 1h, AC;Again at 530 DEG C processing 6h, AC;T1=T3=960-1000 DEG C, T2=T4=850-930 DEG C.The application eliminates the life two-stage differentiation phenomenon in the fatigue process of TC11 forging titanium alloy by simple heat treatment process, greatly improves fatigue strength, provides direction for other same type titanium alloy fatigue performance optimization, and it is of great significance to engineering application of TC11 titanium alloy.

Description

Technical Field

[0001] This invention relates to the field of fatigue performance optimization technology for metallic materials, specifically to a method for optimizing the fatigue performance of TC11 forged titanium alloy. Background Technology

[0002] Titanium alloys have two significant advantages: high specific strength and excellent corrosion resistance, which is why they are preferred in aerospace, chemical, and medical engineering industries. TC11 titanium alloy is a typical α+β type duplex titanium alloy. Due to its high strength, excellent creep resistance, and good thermal stability, it is widely used in the manufacture of compressor disks, blades, and drums for aero engines, and can also be used in the manufacture of aircraft structural components.

[0003] For aerospace materials, ensuring long-term safe and reliable use while maintaining static mechanical properties is paramount, and fatigue performance under cyclic loading is of utmost importance. Titanium alloys are widely used in the aerospace industry, and optimizing their fatigue performance while ensuring other properties is a key issue in the titanium alloy industry. Optimization of titanium alloy fatigue performance typically involves several aspects: microstructure optimization, alloy composition optimization, and surface strengthening processes. Considering time and cost, microstructure optimization is the most economical approach. As a dual-phase titanium alloy, the microstructure of TC11 titanium alloy is significantly affected by heat treatment. Research on how to optimize the fatigue performance of TC11 titanium alloy by modifying simple heat treatment processes has not yet been reported. The extent to which microstructure optimization contributes to fatigue performance, and which heat treatment process yields the optimal microstructure for fatigue performance, are key questions that remain unknown. Summary of the Invention

[0004] The purpose of this invention is to provide a method for optimizing the fatigue performance of TC11 forged titanium alloy. Based on the fatigue fracture mechanism in the experimental process, this method solves the problem of the polarization of fatigue life of TC11 forged titanium alloy and achieves a significant improvement in the fatigue strength of TC11 forged titanium alloy.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] A method for optimizing the fatigue properties of TC11 forged titanium alloy involves performing two-phase region solution aging heat treatment or two-phase region double annealing heat treatment on the forged TC11 titanium alloy to control the primary α phase (α... p The content and size of the substance can improve fatigue strength.

[0007] The solution aging heat treatment process in the two-phase region is as follows: first, it is treated at temperature T1 or T2 for 1 hour, followed by water quenching (WQ); then, it is treated at 530℃ for 6 hours, followed by air cooling (AC); T1 = 960-1000℃, T2 = 850-930℃.

[0008] Preferably, during the solution aging heat treatment in the two-phase region: T1 = 975-1000℃, T2 = 875-915℃.

[0009] The process of the two-phase region double annealing heat treatment is as follows: first, treat at temperature T3 or T4 for 1 hour, then air cool (AC); then treat at 530℃ for 6 hours, then air cool (AC); T3 = 960-1000℃, T4 = 850-930℃.

[0010] Preferably, during the two-phase region double annealing heat treatment: T3 = 975-1000℃, T4 = 875-915℃.

[0011] During the two-phase solution aging heat treatment or two-phase double annealing heat treatment, the heat treatment furnace is first heated to a specified temperature, and then the sample to be treated is placed in the furnace.

[0012] The design mechanism and beneficial effects of this invention are as follows:

[0013] 1. This invention, through analysis of the fatigue performance mechanism of TC11 forged titanium alloy, clarifies that the commonly used industrial double-annealed state and solution-aged state of TC11 forged titanium alloy utilize the primary α phase (α... p The fatigue cracking mechanism is characterized by preferential fatigue cracking in the weakest link. The polarization phenomenon during the fatigue process of TC11 forged titanium alloy was discovered, which is caused by surface defects or surface α... p Surface fatigue sources of cracking and internal α p The internal fatigue source of cluster cracking is caused by two different cracking modes.

[0014] 2. After summarizing and analyzing the fatigue cracking mechanism, this invention provides a specific heat treatment process. By controlling the heat treatment temperature and cooling rate, α is adjusted. p Different microstructures were obtained by varying the content and size of the alloy, and the microstructures obtained after heat treatment successfully eliminated the polarization of fatigue life. Among them, the heat treatment regime of "875-915℃ / 1h, WQ; 530℃ / 6h, AC" can achieve the highest fatigue strength (R=0.1) of 895MPa for TC11 forged titanium alloy.

[0015] 3. This invention, through a simple heat treatment method, ensures creep performance, eliminates the polarization of fatigue life, and significantly improves fatigue strength. It has significant implications for the engineering application of TC11 forged titanium alloys and provides insights for optimizing the fatigue performance of duplex titanium alloys. Attached Figure Description

[0016] Figure 1 Fatigue stress-life diagrams and fatigue fracture mechanisms of TC11 forged titanium alloys in two commonly used industrial states are presented. Among them: (a) fatigue stress-life diagram of the original double-annealed state; (b) fatigue source of internal cracking; (c) fatigue source of surface defect cracking; (d) fatigue source of surface α phase cracking; (e) fatigue stress-life diagram of the original double-annealed state; (f) fatigue source of internal cracking; (g) fatigue source of surface α phase cracking; (h) fatigue source of surface defect cracking.

[0017] Figure 2 The microstructures of the four heat treatment processes before and after optimization are shown below: (a) original solution-aged microstructure; (b) original double-annealed microstructure; (c) microstructures of T3℃ / 1h, AC; 530℃ / 6h, AC; (d) microstructures of T4℃ / 1h, AC; 530℃ / 6h, AC; (e) microstructures of T1℃ / 1h, WQ; 530℃ / 6h, AC; (f) microstructures of T2℃ / 1h, WQ; 530℃ / 6h, AC.

[0018] Figure 3 The fatigue stress-life diagrams for the four optimized tissue types are shown below: (a) T1℃ / 1h, WQ; 530℃ / 6h, AC fatigue stress-life diagram; (b) T2℃ / 1h, WQ; 530℃ / 6h, AC fatigue stress-life diagram; (c) T3℃ / 1h, AC; 530℃ / 6h, AC fatigue stress-life diagram; (d) T4℃ / 1h, AC; 530℃ / 6h, AC fatigue stress-life diagram.

[0019] Figure 4 Creep strain-time plots of different tissues before and after optimization.

[0020] Figure 5 A comparison diagram of fatigue stress-life of different tissues before and after optimization.

[0021] Figure 6 The mechanical properties of the tissue before and after optimization are compared with those of the double-annealed state. Detailed Implementation

[0022] The present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0023] In the following examples and comparative examples, the fatigue test conditions were as follows: axial loading, R = 0.1; the sample used was a parallel section with a length of 15 mm and a diameter of Φ5; the sample was mechanically polished after machining to a Ra = 0.2. The creep performance test conditions were: 600 MPa load maintained at 500℃ for 100 h.

[0024] During the two-phase solution aging heat treatment or two-phase double annealing heat treatment, the heat treatment furnace is first heated to the specified temperature, and then the sample to be treated is placed in the furnace.

[0025] Comparative Example 1:

[0026] Fatigue Performance Evaluation and Mechanism Analysis of TC11 Forged Titanium Alloy: High-cycle fatigue tests were conducted on the commonly used industrial double-annealed state (950℃ for 1h, AC; 530℃ for 6h, AC) and solution-aged state (950℃ for 1h, WQ; 530℃ for 6h, AC) with R=0.1. The results showed a polarization in their high-cycle fatigue life, and the primary α phase (α...) during fatigue was identified. p Fatigue cracking preferentially occurs in the weakest link. The polarization phenomenon is caused by surface defects or surface α... p Surface fatigue sources of cracking and internal α p The internal fatigue source of cluster cracking is caused by two different cracking mechanisms, such as... Figure 1 As shown. The fatigue strengths of the two states are: 810 MPa for the double-annealed state and 830 MPa for the solution-aged state.

[0027] Example 1:

[0028] This embodiment utilizes heat treatment to control the microstructure of TC11 forged titanium alloy. Specifically, it employs either solution aging heat treatment or double annealing heat treatment in the two-phase region, adjusting the α-structure by controlling the heat treatment temperature and cooling rate. p Different microstructures are obtained by varying the content and size. Specifically, the following four techniques (1)-(2) are employed:

[0029] (1) Solution aging heat treatment in the two-phase region: first, treat at temperature T1 or T2 for 1 hour, then water quench (WQ); then treat at 530℃ for 6 hours, then air cool (AC); T1 = 985℃, T2 = 895℃.

[0030] (2) Double annealing heat treatment is adopted in the two-phase region: first, it is treated at temperature T3 or T4 for 1 hour and then air-cooled (AC); then it is treated at 530℃ for 6 hours and then air-cooled (AC); T3 = 985℃, T4 = 895℃.

[0031] Microstructure morphology before and after optimization using four heat treatments, as follows: Figure 2 As shown.

[0032] Fatigue creep performance testing and fatigue cracking mechanism observation were conducted on the adjusted microstructure. Fatigue test conditions: axial loading, R = 0.1; the sample used had a parallel section length of 15 mm and a parallel section diameter of Φ5; the sample was mechanically polished after machining to Ra = 0.2. The experimental conditions for creep performance testing were: a temperature environment of 500℃ and a load of 600 MPa for 100 h. The fatigue test results are as follows: Figure 3 As shown, the creep test results are as follows: Figure 4 As shown. From Figure 3 It is evident that the optimization of the structure in this embodiment successfully eliminated the polarization of fatigue life in TC11 forged titanium alloy. Figure 4 It is noted that the tissues before and after optimization in this embodiment did not fracture when subjected to a load of 500℃ and 600MPa for 100 hours, thus meeting the service requirements.

[0033] The fatigue strengths after microstructure optimization are as follows: 847 MPa after two-phase solution aging heat treatment (T1℃ / 1h, WQ; 530℃ / 6h, AC); 895 MPa after two-phase solution aging heat treatment (T2℃ / 1h, WQ; 530℃ / 6h, AC); 709 MPa after two-phase double annealing heat treatment (T3℃ / 1h, AC; 530℃ / 6h, AC); and 829 MPa after two-phase double annealing heat treatment (T4℃ / 1h, AC; 530℃ / 6h, AC). The heat treatment process of "T2℃ / 1h, WQ; 530℃ / 6h, AC" not only eliminated the fatigue polarization phenomenon but also significantly improved the fatigue strength of TC11 forged titanium alloy. The fatigue stress-life comparison chart for various microstructure states is shown below. Figure 5 As shown.

[0034] After heat treatment and microstructure optimization, based on the aforementioned fatigue and creep performance test results, two microstructures with excellent properties were obtained, such as... Figure 6 As shown, the heat treatment regime of "T1℃ / 1h, WQ; 530℃ / 6h, AC" improves tensile strength, eliminates the polarization of lifespan, enhances fatigue strength, and ensures optimal creep performance. The heat treatment regime of "T2℃ / 1h, WQ; 530℃ / 6h, AC" also improves tensile strength, eliminates the polarization of lifespan, significantly enhances fatigue strength, and achieves the highest fatigue strength for TC11 forged titanium alloy.

Claims

1. A method of optimizing the fatigue performance of a TC11 wrought titanium alloy, characterized in that: The method is to carry out two-phase zone solid solution aging heat treatment on the forged TC11 titanium alloy, so as to control the content and size of primary alpha phase (α p ) in the microstructure, and then improve the fatigue strength; The process of the two-phase zone solution aging heat treatment is: first treated at T1 or T2 for 1h, water quenched (WQ); then treated at 530℃ for 6h, air cooled (AC); T1=975-1000℃, T2=875-915℃.

2. The method of claim 1, wherein: The process of the two-phase zone solution aging heat treatment is: first treated at T1 or T2 for 1h, water quenched (WQ); then treated at 530℃ for 6h, air cooled (AC); T1=975-1000℃, T2=875-915℃.

3. A method of optimizing the fatigue properties of a TC11 wrought titanium alloy, characterized in that: The method is two-phase zone double annealing heat treatment for the forged TC11 titanium alloy to regulate the content and size of primary α phase (α p ) in the microstructure and thus improve the fatigue strength; The process of the two-phase zone solution aging heat treatment is: first treated at T1 or T2 for 1h, water quenched (WQ); then treated at 530℃ for 6h, air cooled (AC); T1=975-1000℃, T2=875-915℃.

4. The method of claim 3, wherein: The process of the two-phase zone solution aging heat treatment is: first treated at T1 or T2 for 1h, water quenched (WQ); then treated at 530℃ for 6h, air cooled (AC); T1=975-1000℃, T2=875-915℃.

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