A heat treatment method for improving the strength and plasticity matching of TC10 titanium alloy

Abstract

The application relates to a heat treatment method for matching the strength and plasticity of TC10 titanium alloy. The TC10 titanium alloy is heated at a phase transition point temperature of 940 DEG C and is kept for 1-2 hours, is cooled in a furnace to 800-850 DEG C and is kept for 1.5-2 hours, is immediately water-cooled, is heated to 560 DEG C and is kept for 4-6 hours, and is taken out for room temperature cooling. The alloy has a mixed structure of strip-shaped alpha phase and equiaxed alpha phase, has high tensile strength and elongation, the tensile strength of the alloy is greater than or equal to 1300 MPa, and the elongation after fracture is greater than or equal to 10%.

Description

Technical Field

[0001] This invention relates to the field of titanium alloy technology, and in particular to a heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy. Technical Background

[0002] Titanium and titanium alloys possess numerous excellent characteristics, including high and low temperature resistance, corrosion resistance, and high specific strength, making them widely used in aerospace, marine engineering, biomedicine, and many other fields. TC10 titanium alloy, with a nominal composition of Ti-6Al-6V-2Sn-0.5Fe-0.5Cu, is derived from TC4 titanium alloy (nominal composition Ti-6Al-4V). Compared to TC4, TC10 contains more β-type stabilizing elements, resulting in higher strength and excellent hardenability. This broadens its application range, with extensive use in aerospace, marine, and petroleum engineering. Consequently, the mechanical properties of TC10 titanium alloy are subject to increasingly stringent requirements, demanding a good balance between strength and ductility.

[0003] The main strengthening methods for TC10 titanium alloy are hot working and heat treatment. Among these, heat treatment is the most widely used method due to its low cost and ease of operation. The main heat treatment methods for TC10 titanium alloy include quenching, quenching-aging, ordinary annealing, double annealing, and isothermal annealing. However, it is difficult to simultaneously satisfy both the strength and ductility of the alloy in various heat treatment processes. When the alloy strength increases, the corresponding ductility decreases; conversely, when the alloy ductility is retained, the alloy strength decreases. Therefore, it is necessary to propose a heat treatment process that achieves a good balance between strength and ductility in TC10 titanium alloy after heat treatment. Summary of the Invention

[0004] In view of the shortcomings of the existing technology, the purpose of this invention is to propose a heat treatment method to improve the balance between strength and plasticity of TC10 titanium alloy. By heat treating TC10 titanium alloy, the goal of achieving a good balance between strength and plasticity can be achieved.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A heat treatment method for improving the balance between strength and ductility of TC10 titanium alloy includes the following steps:

[0007] Step 1: Heat the electric furnace to 940℃ and hold for 20 minutes. Then, place the TC10 titanium alloy into the electric furnace and hold for 1 to 2 hours.

[0008] Step 2: Reduce the temperature of the electric furnace to 800℃~850℃, hold for 1.5~2 hours, then remove the TC10 titanium alloy from the electric furnace and immediately water cool it.

[0009] Step 3: Reheat the electric furnace to 560℃ and hold for 20 minutes. Then, put the water-cooled TC10 titanium alloy from Step 2 into the electric furnace and hold for 4-6 hours. After that, take out the TC10 titanium alloy and cool it to room temperature.

[0010] Preferably, the heating rate of the electric furnace in step one is 20°C / min.

[0011] Preferably, the cooling rate of the electric furnace in step two is 15℃ / min to 20℃ / min.

[0012] Preferably, the heating rate of the electric furnace in step three is 20°C / min.

[0013] Preferably, the TC10 titanium alloy contains, by weight percentage: Al: 5.6%–5.85%; V: 5.5%–5.7%; Sn: 2.2%–2.4%; Fe: 0.6%–0.7%; Cu: 0.55%–0.7%; O: 0.16%–0.18%; C: 0–0.05%; N: 0–0.04%; H: 0–0.0015%; with Ti as the balance.

[0014] Preferably, the TC10 titanium alloy is a TC10 titanium alloy with a dual-state structure after forging.

[0015] Preferably, in step two, during the water cooling process of removing the TC10 titanium alloy from the electric furnace, the time from the opening of the electric furnace door to the TC10 titanium alloy entering the water is ≤2s.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] This invention alters the microstructure of TC10 titanium alloy by selecting appropriate heat treatment temperatures, holding times, and cooling methods. The resulting microstructure is a mixture of strip-shaped and equiaxed α phases. The α phases distributed in the β matrix are predominantly strip-shaped with no obvious directionality. These strip-shaped α phases vary in length and exhibit a serrated morphology, ranging from 7.11 μm to 66.3 μm in length and 1.6 μm to 4.61 μm in width, with a content of approximately 32%. Simultaneously, a certain amount of equiaxed α phase is distributed in the β matrix, with a content of approximately 5%. This mixed microstructure, containing a large amount of strip-shaped and a certain amount of equiaxed α phases, simultaneously improves the strength and plasticity of the TC10 titanium alloy. In other words, the TC10 titanium alloy exhibits a good balance between strength and plasticity, achieving a tensile strength ≥1300 MPa and an elongation after fracture ≥10%. Attached Figure Description

[0018] Figure 1 Metallographic image of TC10 titanium alloy with a dual-state structure after forging;

[0019] Figure 2 Schematic diagram of the heat treatment process of this invention;

[0020] Figure 3 Metallographic image of TC10 titanium alloy in Example 1;

[0021] Figure 4 Metallographic image of TC10 titanium alloy in Example 2;

[0022] Figure 5 Metallographic image of TC10 titanium alloy in Example 3;

[0023] Figure 6 Metallographic image of TC10 titanium alloy in Example 4;

[0024] Figure 7 Metallographic image of TC10 titanium alloy (Comparative Example 1);

[0025] Figure 8 Metallographic image of TC10 titanium alloy (Comparative Example 2);

[0026] Figure 9 Metallographic image of TC10 titanium alloy (Comparative Example 3);

[0027] Figure 10 Metallographic image of TC10 titanium alloy (Comparative Example 4);

[0028] Figure 11 The image shows the metallographic structure of TC10 titanium alloy in Comparative Example 5. Specific Implementation

[0029] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] It should be noted that the TC10 titanium alloy used in the embodiments of the present invention is a forged TC10 titanium alloy with a bimodal structure. Its chemical composition by weight percentage is Al: 5.7%; V: 5.5%; Sn: 2.3%; Fe: 0.7%; Cu: 0.6%; O: 0.17%; C: 0.03%; N: 0.02%; H: 0.001%; ​​Ti balance. Its microstructure morphology is as follows: Figure 1 As shown, there are two types of α phase morphology: one is the primary α phase, which is uniformly distributed on the matrix, and the other is the secondary α phase, which is mainly in the β transformation structure. The original forged microstructure consists of the primary α phase and the β transformation structure (fine strips of secondary α phase, with the black background between the secondary α phases being residual β).

[0031] Example 1

[0032] A heat treatment method for improving the balance between strength and ductility of TC10 titanium alloy includes the following steps:

[0033] Step 1: Heat the electric furnace to 940℃ at a heating rate of 20℃ / min and hold for 20min to stabilize the furnace temperature. Then, place the TC10 titanium alloy in the furnace and hold for 1h.

[0034] Step 2: After holding the temperature and time as described in Step 1, reduce the temperature of the electric furnace to 850°C at a cooling rate of 15°C / min, so that the TC10 titanium alloy is cooled to 850°C with the furnace. After holding the temperature for 1.5 hours, remove the TC10 titanium alloy from the electric furnace and immediately water cool it.

[0035] Step 3: Reheat the electric furnace to 560℃ at a heating rate of 20℃ / min, hold for 20 minutes to stabilize the furnace temperature, then dry the surface of the water-cooled TC10 titanium alloy from Step 2, place it in the electric furnace, hold for 4 hours, and then remove the TC10 titanium alloy for room temperature cooling.

[0036] Example 2

[0037] A heat treatment method for improving the balance between strength and ductility of TC10 titanium alloy includes the following steps:

[0038] Step 1: Heat the electric furnace to 940℃ at a heating rate of 20℃ / min and hold for 20min to stabilize the furnace temperature. Then, place the TC10 titanium alloy in the furnace and hold for 2h.

[0039] Step 2: After holding the temperature and time as described in Step 1, reduce the temperature of the electric furnace to 800℃ at a cooling rate of 20℃ / min, so that the TC10 titanium alloy is cooled to 800℃ with the furnace. After holding the temperature for 2 hours, remove the TC10 titanium alloy from the electric furnace and immediately water cool it.

[0040] Step 3: Reheat the electric furnace to 560℃ at a heating rate of 20℃ / min, hold for 20 minutes to stabilize the furnace temperature, then dry the surface of the water-cooled TC10 titanium alloy from Step 2, place it in the electric furnace, hold for 6 hours, and then remove the TC10 titanium alloy for room temperature cooling.

[0041] Example 3

[0042] A heat treatment method for improving the balance between strength and ductility of TC10 titanium alloy includes the following steps:

[0043] Step 1: Heat the electric furnace to 940℃ at a heating rate of 20℃ / min and hold for 20min to stabilize the furnace temperature. Then, place the TC10 titanium alloy in the furnace and hold for 1.2h.

[0044] Step 2: After holding the temperature and time as described in Step 1, reduce the temperature of the electric furnace to 820°C at a cooling rate of 17°C / min, so that the TC10 titanium alloy is cooled to 820°C with the furnace. After holding the temperature for 1.9 hours, remove the TC10 titanium alloy from the electric furnace and immediately water cool it.

[0045] Step 3: Reheat the electric furnace to 560℃ at a heating rate of 20℃ / min, hold for 20 minutes to stabilize the furnace temperature, then dry the surface of the water-cooled TC10 titanium alloy from Step 2, place it in the electric furnace, hold for 5 hours, and then remove the TC10 titanium alloy for room temperature cooling.

[0046] Example 4

[0047] A heat treatment method for improving the balance between strength and ductility of TC10 titanium alloy includes the following steps:

[0048] Step 1: Heat the electric furnace to 940℃ at a heating rate of 20℃ / min and hold for 20min to stabilize the furnace temperature. Then, place the TC10 titanium alloy in the furnace and hold for 1.8h.

[0049] Step 2: After holding the temperature and time as described in Step 1, reduce the temperature of the electric furnace to 840°C at a cooling rate of 15°C / min, so that the TC10 titanium alloy is cooled to 840°C with the furnace. After holding the temperature for 1.8 hours, remove the TC10 titanium alloy from the electric furnace and immediately water cool it.

[0050] Step 3: Reheat the electric furnace to 560℃ at a heating rate of 20℃ / min, hold for 20min to stabilize the furnace temperature, then dry the surface of the water-cooled TC10 titanium alloy from Step 2, place it in the electric furnace, hold for 5.5h, and then remove the TC10 titanium alloy for room temperature cooling.

[0051] In the above embodiments, during the process of immediately water cooling the TC10 titanium alloy after removing it from the electric furnace in step two, the time from opening the electric furnace door to the TC10 titanium alloy entering the water is ≤2s.

[0052] Comparative Example 1

[0053] In step one, the electric furnace is heated to 920°C, and the rest is the same as in Example 1.

[0054] Comparative Example 2

[0055] In step one, the electric furnace is heated to 960°C, and the rest is the same as in Example 1.

[0056] Comparative Example 3

[0057] In step two, the TC10 titanium alloy is removed from the electric furnace and immediately air-cooled; the rest is the same as in Example 3.

[0058] Comparative Example 4

[0059] In step two, the TC10 titanium alloy is removed from the electric furnace and immediately air-cooled; the rest is the same as in Example 2.

[0060] Comparative Example 5

[0061] In step two, the TC10 titanium alloy is removed from the electric furnace and immediately air-cooled; otherwise, it is the same as in Example 1.

[0062] 1. Metallographic image of TC10 titanium alloy

[0063] Metallographic images of TC10 titanium alloys obtained in Comparative Examples 1-5 are shown below. Figures 7-11 As shown, Figures 7-11 It can be seen that, in Comparative Example 1, the content of strip-shaped α phase in the metallographic structure is relatively small, while the content of equiaxed α phase is relatively large; in Comparative Example 2, the metallographic structure is dominated by strip-shaped α phase, and the equiaxed α phase disappears; in Comparative Example 3, the metallographic structure is dominated by strip-shaped α phase, containing a very small amount of equiaxed α phase; in Comparative Example 4, the metallographic structure is dominated by strip-shaped α phase, with relatively wide strip-shaped α phases, containing a very small amount of equiaxed α phase; in Comparative Example 5, the metallographic structure is dominated by strip-shaped α phase, and the equiaxed α phase almost disappears; the metallographic images of the TC10 titanium alloys obtained in Examples 1 to 4 are shown below. Figures 3-6 As shown, from Figures 3-6 It can be seen that the microstructure of the TC10 titanium alloy prepared by this invention is a mixed structure composed of strip-shaped α phase and equiaxed α phase. The α phase morphology distributed on the β matrix is ​​mainly strip-shaped, with a content of about 32%. The strip-shaped α phase has no obvious directionality, varies in length, and some have a serrated morphology. The length ranges from 7.11 μm to 66.3 μm, and the width ranges from 1.6 μm to 4.61 μm. At the same time, a certain amount of equiaxed α phase is distributed on the β matrix, with a content of about 5%. This mixed structure containing a large amount of strip-shaped α phase and a certain amount of equiaxed α phase will simultaneously improve the strength and plasticity of the TC10 titanium alloy.

[0064] 2. Performance Testing

[0065] The mechanical property test results of the TC10 titanium alloys obtained in Examples 1-4 and Comparative Examples 1-5 are shown in Table 1:

[0066] Table 1 Mechanical properties of TC10 titanium alloy

[0067]

[0068]

[0069] As can be seen from Table 1, the TC10 titanium alloys prepared in Examples 1 to 4 have a better match between strength and plasticity than the comparative examples, with tensile strength ≥1300MPa and elongation after fracture ≥10%.

[0070] In summary, this invention provides a heat treatment method to improve the balance between strength and plasticity of TC10 titanium alloy. The method uses a forged TC10 titanium alloy with a dual-phase microstructure. First, the alloy is heated to its phase transformation point of 940°C and held for 1-2 hours. Then, it is furnace cooled to 800-850°C and held for 1.5-2 hours, followed immediately by water cooling. The alloy is then heated to 560°C and held for 4-6 hours. Afterward, the alloy is removed and cooled to room temperature. At this point, the alloy microstructure is a mixture of strip-shaped α phase and equiaxed α phase. After tensile testing, the alloy exhibits a tensile strength ≥1300 MPa and an elongation after fracture ≥10%, meaning the alloy possesses both high tensile strength and elongation.

[0071] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy, characterized in that, Includes the following steps: Step 1: Heat the electric furnace to 940℃ and hold for 20 minutes. Then, place the TC10 titanium alloy into the electric furnace and hold for 1 to 2 hours. The TC10 titanium alloy contains, by weight percentage: Al: 5.6%–5.85%; V: 5.5%–5.7%. Sn: 2.2%–2.4%; Fe: 0.6% ~ 0.7%; Cu: 0.55% ~ 0.7%; O: 0.16%–0.18%; C: 0–0.05%; N: 0–0.04%; H: 0–0.0015%; Ti balance; Step 2: Reduce the temperature of the electric furnace to 800℃~850℃, hold for 1.5~2 hours, then remove the TC10 titanium alloy from the electric furnace and immediately water cool it. Step 3: Reheat the electric furnace to 560℃ and hold for 20 minutes. Then, put the water-cooled TC10 titanium alloy from Step 2 into the electric furnace and hold for 4-6 hours. After that, take out the TC10 titanium alloy and cool it to room temperature.

2. The heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy according to claim 1, characterized in that, The heating rate of the electric furnace in step one is 20℃ / min.

3. The heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy according to claim 1, characterized in that, Step 2: The cooling rate of the electric furnace is 15℃ / min to 20℃ / min.

4. The heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy according to claim 1, characterized in that, The heating rate of the electric furnace in step three is 20℃ / min.

5. The heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy according to claim 1, characterized in that, The TC10 titanium alloy is a TC10 titanium alloy with a dual-state structure after forging.

6. The heat treatment method for improving the balance between strength and plasticity of TC10 titanium alloy according to claim 1, characterized in that, In step two, during the water cooling process of removing the TC10 titanium alloy from the electric furnace, the time from the opening of the electric furnace door to the TC10 titanium alloy entering the water is ≤2s.

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