A triple heat treatment process to improve the comprehensive mechanical properties of TC11 titanium alloy

Abstract

The present invention discloses a triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy, the process comprising: 1. placing the TC11 titanium alloy in a heat treatment furnace at a temperature of 940℃~950℃ for 2.5h~3h for solution treatment, and air cooling after exiting the furnace; 2. keeping the TC11 titanium alloy in a heat treatment furnace at a temperature of 380℃~400℃ for 8h~10h for pre-aging treatment, and air cooling after exiting the furnace; 3. keeping the TC11 titanium alloy in a heat treatment furnace at a temperature of 550℃~580℃ for 4h~6h for aging treatment, and air cooling after exiting the furnace. The present invention controls the organizational evolution process well by controlling the temperature and time of the triple heat treatment process, obtains a small-sized, uniformly distributed and dispersed α-phase organization, effectively improves the comprehensive mechanical properties of the TC11 titanium alloy, greatly improves the strength of the TC11 titanium alloy, has a simple process, is easy to operate, and takes a short time, and solves the problem of difficult organizational regulation of TC11 titanium alloy castings.

Description

Technical Field

[0001] The invention belongs to the technical field of metal heat treatment, and specifically relates to a triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy. Background Art

[0002] With the rapid development of my country's aerospace industry, the requirements for the comprehensive performance of aircraft engines are increasing. The application of titanium alloys can effectively reduce the weight of the engine, improve the thrust-to-weight ratio and extend the service life. TC11 titanium alloy is a Ti-Al-Mo-Zr-Si martensitic heat-resistant titanium alloy with excellent comprehensive performance. The alloy has a good match of room temperature performance, fracture toughness, fatigue and creep performance at 500-550℃. It can solve the over-temperature problem of the integral blade of the engine compressor in the development of China, fill the gap of titanium alloy materials for the integral blade of my country's aero-engine in the temperature range of 500℃-550℃, and has great engineering application significance.

[0003] At present, the prior art discloses some technical solutions for heat treatment of titanium alloy castings. For example, Chinese patent application with application publication number CN114774816A discloses a heat treatment process for TC11 titanium alloy castings: heating the TC11 titanium alloy casting to T β Keep the temperature at 3-5℃ (T1) for t1min, then cool to T2, then keep the temperature for t2min and cool to T3, etc., until the casting cools to T m Keep warm for 60 to 120 minutes; then raise the temperature to T n Keep warm for 60 to 120 minutes, then cool to T m Keep warm for 60 to 120 minutes, then raise the temperature to T n Keep warm for 60 to 120 minutes, repeat this process for 3 to 5 times, and finally cool the casting to T m After keeping warm for 60 to 120 minutes, directly air cool to room temperature. The final casting obtains a dual-state structure, the primary α phase is short rod-shaped or spherical, the content is about 30% to 40%, the room temperature tensile strength is 1050MPa, and the elongation is increased to 8%. Although the above heat treatment process solves the problems such as the difficulty in regulating the structure of TC11 titanium alloy castings, the plasticity of the obtained TC11 titanium alloy castings is poor, and the process is complicated and time-consuming. Therefore, developing a better heat treatment process is one of the keys to improving the comprehensive mechanical properties of TC11 titanium alloy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy in view of the deficiencies of the above-mentioned prior art. The process sequentially performs a triple heat treatment process of solution treatment, pre-aging treatment and aging treatment on TC11 titanium alloy, and controls the organizational evolution process well by controlling the temperature and time of the triple heat treatment process, thereby obtaining a fine-sized, uniformly distributed and dispersed α-phase structure, effectively improving the comprehensive mechanical properties of TC11 titanium alloy, and especially greatly improving the strength of TC11 titanium alloy.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy, characterized in that the process comprises the following steps:

[0006] Step 1: Place the TC11 titanium alloy in a heat treatment furnace at a temperature of 940°C to 950°C for 2.5h to 3h for solution treatment, and then air cool it after it is taken out of the furnace;

[0007] Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 380°C to 400°C for 8h to 10h for pre-aging treatment, and then air cool it after it is taken out of the furnace;

[0008] Step 3: Place the TC11 titanium alloy after air cooling in step 2 in a heat treatment furnace at a temperature of 550° C. to 580° C. for 4 h to 6 h for aging treatment, and then air cool it after being taken out of the furnace.

[0009] The present invention firstly performs a solid solution treatment on the TC11 titanium alloy at a temperature below the (α+β) / β transformation temperature, i.e., 940°C to 950°C, for 2.5 to 3 hours, and then takes out of the furnace to air cool. During the cooling process, no shear martensitic phase transformation occurs, but a diffusion transformation from β phase to α phase occurs, and the generated α phase is in the form of lamellar strips. Then, the alloy is pre-aged at a lower temperature, i.e., 380°C to 400°C, for 8 to 10 hours, and then takes out of the furnace to air cool. Due to the lower temperature of the pre-aging treatment, the α phase in the TC11 titanium alloy structure is eliminated. The transition phase β' or ω can be dispersedly nucleated, and the β phase is transformed into the β' or ω transition phase. In the subsequent aging treatment process at 550℃~580℃ for 4h~6h, the transformed β' or ω transition phase provides a high-density nucleation position for the nucleation of the α phase, and finally obtains a more uniform, fine and dispersed α phase structure than that formed by single solid solution. The dispersed distribution of the nano-precipitated phase is used as a dislocation source and an obstacle at the same time, resulting in a sustainable self-hardening deformation mechanism and improving ductility and strength. In summary, the triple heat treatment used in the present invention is more effective than the double heat treatment in improving the comprehensive mechanical properties of the TC11 titanium alloy.

[0010] The above-mentioned triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy is characterized in that in step one, the TC11 titanium alloy is placed in a heat treatment furnace at a temperature of 950° C. for 3 hours for solution treatment, and then air-cooled after being taken out of the furnace.

[0011] The above-mentioned triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy is characterized in that in step 2, the TC11 titanium alloy air-cooled in step 1 is placed in a heat treatment furnace at a temperature of 400°C for 10 hours for pre-aging treatment, and then air-cooled out of the furnace.

[0012] The above-mentioned triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy is characterized in that in step three, the TC11 titanium alloy air-cooled in step two is placed in a heat treatment furnace at a temperature of 580°C for 6 hours for aging treatment, and then air-cooled after being taken out of the furnace.

[0013] Compared with the prior art, the present invention has the following advantages:

[0014] 1. The present invention sequentially performs a triple heat treatment process of solution treatment, pre-aging treatment and aging treatment on the TC11 titanium alloy. By controlling the temperature and time of the triple heat treatment process, the microstructure evolution process is well controlled, and a fine, uniformly distributed and dispersed α-phase structure is obtained, which effectively improves the comprehensive mechanical properties of the TC11 titanium alloy, especially greatly improves the strength of the TC11 titanium alloy.

[0015] 2. The triple heat treatment process of the present invention is simple, easy to operate, has fewer processes, and takes less time, thus solving the problem of difficult microstructure control of TC11 titanium alloy castings.

[0016] 3. The tensile strength of the TC11 titanium alloy after the triple heat treatment process of the present invention is 1165MPa-1166MPa, the yield strength is 1020MPa-1024MPa, the elongation after fracture is 12.5%-13%, and the cross-sectional shrinkage is 47%-51%, which is improved compared with the comprehensive mechanical properties of the TC11 titanium alloy after conventional solution aging heat treatment.

[0017] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a microstructure diagram of the TC11 titanium alloy after triple heat treatment in Example 1 of the present invention.

[0019] Figure 2 This is a microstructure diagram of the TC11 titanium alloy after heat treatment in Comparative Example 1 of the present invention.

[0020] Figure 3This is a microstructure diagram of the TC11 titanium alloy after triple heat treatment in Example 2 of the present invention.

[0021] Figure 4 This is a microstructure diagram of the TC11 titanium alloy after heat treatment in Comparative Example 2 of the present invention.

[0022] Figure 5 1 and 2. The room temperature tensile stress-strain curves of the TC11 titanium alloy after triple heat treatment in Examples 1 and 2 of the present invention and the TC11 titanium alloy after heat treatment in Comparative Examples 1 and 2. DETAILED DESCRIPTION

[0023] Example 1

[0024] This embodiment includes the following steps:

[0025] Step 1: Place the TC11 titanium alloy in a heat treatment furnace at 940°C for 2.5 hours for solution treatment, and then air cool it after it is taken out of the furnace;

[0026] Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 380° C. for 8 hours for pre-aging treatment, and then air cool it after being taken out of the furnace;

[0027] Step 3: Place the TC11 titanium alloy air-cooled in step 2 in a heat treatment furnace at 550° C. for 4 hours for aging treatment, and then air-cool it after being taken out of the furnace.

[0028] Comparative Example 1

[0029] This comparative example comprises the following steps:

[0030] Step 1: Place the TC11 titanium alloy in a heat treatment furnace at 940°C for 2.5 hours for solution treatment, and then air cool it after it is taken out of the furnace;

[0031] Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 550° C. for 4 hours for aging treatment, and then air cool it after being taken out of the furnace.

[0032] Figure 1 The microstructure of the TC11 titanium alloy after triple heat treatment in Example 1 of the present invention is shown in FIG. Figure 1 It can be seen that the TC11 titanium alloy after triple heat treatment is a typical mixed structure with multiple forms: 24% primary α phase + 8% lamellar secondary α phase + 68% aging β transformation structure.

[0033] Figure 2 The microstructure of the TC11 titanium alloy after heat treatment in Comparative Example 1 of the present invention is shown in FIG. Figure 2 It can be seen that the TC11 titanium alloy structure after the traditional solid solution + aging heat treatment in Comparative Example 1 is a dual-state structure.

[0034] Will Figure 1 and Figure 2 By comparison, it can be seen that the triple heat treatment of the present invention can effectively regulate the content and morphology of the primary α phase and β transformation structure of the TC11 titanium alloy. The mechanical properties of the TC11 titanium alloy in the mixed structure state are improved compared with the TC11 titanium alloy obtained by the traditional heat treatment process. The main mechanical properties comparison test results are shown in Figure 5 and Table 1. .

[0035] Example 2

[0036] This embodiment includes the following steps:

[0037] Step 1: Place the TC11 titanium alloy in a heat treatment furnace at 950°C for 3 hours for solution treatment, and then air cool it after it is taken out of the furnace;

[0038] Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 400° C. for 10 hours for pre-aging treatment, and then air cool it after it is taken out of the furnace;

[0039] Step 3: Place the TC11 titanium alloy air-cooled in step 2 in a heat treatment furnace at 580° C. for 6 hours for aging treatment, and then air-cool it after being taken out of the furnace.

[0040] Comparative Example 2

[0041] This comparative example comprises the following steps:

[0042] Step 1: Place the TC11 titanium alloy in a heat treatment furnace at 950°C for 3 hours for solution treatment, and then air cool it after it is taken out of the furnace;

[0043] Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 580° C. for 6 hours for aging treatment, and then air cool it after being taken out of the furnace.

[0044] Figure 3 The microstructure of the TC11 titanium alloy after triple heat treatment in Example 2 of the present invention is shown in FIG. Figure 3 It can be seen that the alloy under this heat treatment process is a typical mixed structure with multiple states: 22% primary α phase + 7% lamellar secondary α phase + 70% aging β transformation structure.

[0045] Figure 4 The microstructure of the TC11 titanium alloy after heat treatment in Comparative Example 2 of the present invention is shown in FIG. Figure 4 It can be seen that the structure of the TC11 titanium alloy after the traditional solution + aging heat treatment in Comparative Example 2 is a dual-state structure.

[0046] Will Figure 3 and Figure 4 By comparison, it can be seen that the triple heat treatment of the present invention can effectively regulate the content and morphology of the primary α phase and β transformation structure of the TC11 titanium alloy. The mechanical properties of the TC11 titanium alloy in the mixed structure state are improved compared with the TC11 titanium alloy obtained by the traditional heat treatment process. The main mechanical properties comparison test results are shown in Figure 5 and Table 1.

[0047] The room temperature mechanical properties of the TC11 titanium alloy after triple heat treatment in Examples 1 and 2 of the present invention and the TC11 titanium alloy after heat treatment in Comparative Examples 1 and 2 were tested. The results are as follows: Figure 5 And as shown in Table 1.

[0048] Table 1

[0049] sample UTS(MPa) YS(MPa) EI(%) RA(%) Example 1 1165 1024 12.5 47 Comparative Example 1 1064 970 9 26 Example 2 1166 1020 13 51 Comparative Example 2 1117 988 11 33

[0050] Figure 5 The room temperature tensile stress-strain curves of the TC11 titanium alloy after triple heat treatment in Examples 1 and 2 of the present invention and the TC11 titanium alloy after heat treatment in Comparative Examples 1 and 2 are shown in FIG. Figure 5 It can be seen that compared with the TC11 titanium alloy obtained by the traditional heat treatment process, the room temperature tensile strength and elongation of the TC11 titanium alloy after triple heat treatment of the present invention are improved.

[0051] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy, characterized in that: The process includes the following steps: Step 1: Place the TC11 titanium alloy in a heat treatment furnace at a temperature of 940°C to 950°C for 2.5h to 3h for solution treatment, and then air cool it after it is taken out of the furnace; Step 2: Place the TC11 titanium alloy after air cooling in step 1 in a heat treatment furnace at a temperature of 380°C to 400°C for 8h to 10h for pre-aging treatment, and then air cool it after it is taken out of the furnace; Step 3: Place the TC11 titanium alloy after air cooling in step 2 in a heat treatment furnace at a temperature of 550° C. to 580° C. for 4 h to 6 h for aging treatment, and then air cool it after being taken out of the furnace.

2. A triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy according to claim 1, characterized in that: In step 1, the TC11 titanium alloy is placed in a heat treatment furnace at a temperature of 950° C. and kept at this temperature for 3 hours for solution treatment, and then taken out of the furnace and air-cooled.

3. A triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy according to claim 1, characterized in that: In step 2, the TC11 titanium alloy air-cooled in step 1 is placed in a heat treatment furnace at a temperature of 400° C. for 10 hours for pre-aging treatment, and then air-cooled after being taken out of the furnace.

4. A triple heat treatment process for improving the comprehensive mechanical properties of TC11 titanium alloy according to claim 1, characterized in that: In step 3, the TC11 titanium alloy air-cooled in step 2 is placed in a heat treatment furnace at a temperature of 580° C. for 6 hours for aging treatment, and then air-cooled after being taken out of the furnace.

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