Preparation method of Ti2AlNb-based alloy ring piece

Abstract

The invention provides a preparation method of a Ti2AlNb-based alloy ring piece, which is characterized by comprising the following steps: 1) heating a cast ingot to 1150-1200 DEG C, and completing forging of not less than two upsetting and two drawing; (2) the blank is heated to 10-50 DEG C above the beta phase transformation point, and two-time upsetting and two-time drawing are carried out; (3) the blank is heated for 1-3 times at the temperature of 80-50 DEG C below the beta phase transformation point, and upsetting and drawing are carried out; (4) the blank is heated to 80-50 DEG C below the beta phase transformation point, punching is conducted after upsetting, and pre-rolling shaping is conducted; (5) the blank is heated to 80-50 DEG C below the beta phase transformation point, and ring rolling forming is conducted till the target size is achieved; 6, preheating treatment, solid solution treatment and aging treatment are conducted in sequence, and finally the ring part finished product is obtained.The Ti2AlNb-based alloy ring part prepared through the technology is excellent in heat resistance and heat stability matching, the service requirements of stator parts such as the aero-engine casing ring part are met, the production process is simple, the period is short, and the method is suitable for large-scale industrial production.

Description

Technical Field

[0001] This invention belongs to the field of titanium-based intermetallic compound processing, specifically relating to a method for preparing Ti2AlNb-based alloy rings. Background Technology

[0002] Ti2AlNb-based alloys, as a novel lightweight high-temperature structural material, have broad application prospects in the aerospace field due to their excellent high-temperature performance, and are commonly used in components such as casing rings of aerospace engines. The complex service environment of Ti2AlNb-based alloy rings places stringent requirements on the alloy's performance, especially the matching of thermal strength and thermal stability. Therefore, the microstructure design and preparation process of the alloy are extremely critical.

[0003] The patent "Rolling and Heat Treatment Method of Ti2AlNb-based Alloy Casing Ring" (Patent No.: CN201410305093.9) prepares a basket-structured ring by forging in the high-temperature region below the β phase transformation point and rolling in the α2+B2 two-phase region. However, forging in the high-temperature region below the β phase transformation point easily leads to the formation of coarse α2 phase, which is not conducive to subsequent microstructure and property control. The patent "Large-size Ti2AlNb Alloy Ring and Its Manufacturing Method" (Patent No.: CN202011542728.9) uses large deformation rolling in the temperature region above the β phase transformation point and temperature-controlled cooling to obtain a basket-structured ring. However, during the large deformation in the single-phase region, the surface temperature of the forging billet drops rapidly while the internal temperature is prone to overheating, which is not conducive to the control of microstructure uniformity. Moreover, temperature-controlled cooling requires extremely high temperature control precision. Although the above-mentioned basket-structured Ti2AlNb-based alloys have excellent high-temperature strength, their thermal stability is relatively weak. Both patents, "A Preparation Process of Ti2AlNb-based Alloy Rings" (Patent No.: CN202010882092.6) and "A Preparation Process of Ti2AlNb-based Alloy Rings" (Patent No.: CN202210370252.8), employ a process of cyclic forging in the temperature ranges above and below the β-phase transformation point, followed by rolling in the temperature range below the β-phase transformation point, to prepare rings with a dual-phase structure. However, the "high-low-high-low" cyclic forging process is complex, resulting in high processing losses and a long production cycle. The aforementioned dual-phase Ti2AlNb-based alloys exhibit relatively lower creep and endurance properties compared to basket-weave structures. Therefore, coarse original B2 grains are typically obtained during forging to compensate for this shortcoming. However, this significantly deteriorates the alloy's plasticity, which is also detrimental to the matching of thermal strength and thermal stability.

[0004] Furthermore, the heat treatment of the aforementioned Ti2AlNb-based alloy rings all employs a simple double heat treatment method. For Ti2AlNb-based alloys with complex phase compositions, this method is difficult to effectively and precisely control the alloy microstructure, making it difficult to achieve a match between the alloy's thermal strength and thermal stability.

[0005] In summary, reasonable design and precise control of the microstructure during the preparation of Ti2AlNb-based alloy rings, along with effective control of microstructure uniformity, are crucial for achieving a good match between the alloy's thermal strength and thermal stability. In addition, the preparation process design should not be too complex, otherwise it will be detrimental to large-scale industrial production. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a method for preparing Ti2AlNb-based alloy ring components. The Ti2AlNb ring components prepared by this method exhibit a tri-phase microstructure composed of large-sized B2 grains and small-sized subgrains, demonstrating excellent microstructure uniformity and achieving a superior balance between thermal strength and thermal stability, thus meeting the service requirements of stator components such as engine casing rings. Furthermore, this method features a simple production process, a short production cycle, and is suitable for large-scale industrial production.

[0007] The specific technical solution is as follows: A method for preparing a Ti2AlNb-based alloy ring includes the following steps: Step 1): Heat the ingot to 1150~1200℃, complete no less than two upsetting and two drawing processes, the upsetting deformation amount is not less than 50%, the final forging temperature is not less than 850℃, and air cool after forging; Step 2): Heat the billet to 10-50°C above the β phase transformation point, perform two upsetting and two drawing processes, and the final forging temperature is not lower than 850°C. After forging, cool it with water or oil. Step 3): Heat the billet to 80~50℃ below the β phase transformation point, perform 1~3 upsetting and drawing cycles, control the upsetting deformation in the range of 40%~50%, and the final forging temperature is not lower than 750℃. After forging, air cool. Step 4): Heat the billet to 80~50℃ below the β phase transformation point, perform upsetting, punching and pre-rolling shaping, and air-cool after forging; Step 5): Heat the billet to 80~50℃ below the β phase transformation point, ring roll it to the target size, and air cool it after forging; Step 6): Perform preheating, solution treatment and aging treatment in sequence to obtain the ring blank, and finally obtain the finished ring by machining.

[0008] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is as follows: in step 1), the ingot is held at 1100~1200℃ for 15~24h, and the deformation speed during the billet opening process is not less than 40mm / s.

[0009] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is that, in step 2), the deformation of the billet is specifically carried out by two consecutive upsetting and two drawing operations, and the deformation speed is not less than 40 mm / s.

[0010] The preferred embodiment of the method for preparing the Ti2AlNb-based alloy ring is as follows: in step 3), forging is performed by shaft upsetting and side drawing, and the upsetting deformation rate is not greater than 0.02 s. -1 The deformation amount in a single elongation is less than 25%.

[0011] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is that, in step 4), the upsetting deformation rate is no greater than 0.02 s⁻¹. -1 The pre-rolling rate is no more than 0.01s. -1 .

[0012] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is that, in step 5), the ring rolling deformation rate is no greater than 0.01 s. -1 The deformation amount per ring rolling cycle is less than 15%.

[0013] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is as follows: In step 6), the preheating temperature is 50-10°C below the phase transformation point, the holding time is 1-4 hours, and then air cooling is performed; the solution treatment temperature is 120-80°C below the phase transformation point, the holding time is 1-4 hours, and then water cooling or oil cooling is performed; the aging treatment temperature is 780-850°C, the holding time is 12-24 hours, and then air cooling is performed.

[0014] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is that the microstructure of the prepared Ti2AlNb-based alloy ring is a three-state structure composed of large-sized B2 grains and small-sized sub-grains, wherein the B2 grain size is 200-300 μm and the α2 grain size is less than 2 μm and uniformly distributed.

[0015] The preferred embodiment of the method for preparing a Ti2AlNb-based alloy ring is that the ring has a room temperature tensile strength of not less than 1070 MPa, a 750℃ tensile strength of not less than 730 MPa, a room temperature tensile elongation of not less than 8%, a room temperature elongation of not less than 3% after heat exposure at 750℃ / 100h, and a creep time of not less than 25h under 750℃ / 250MPa conditions. Beneficial effects

[0016] The process of casting billet preparation combines multiple large deformation upsetting and intermediate furnace heat preservation, which can effectively break up the as-cast structure and promote element diffusion, thus improving the uniformity of the structure.

[0017] The billet is subjected to two consecutive upsetting and two drawing processes in the B2 phase region. By increasing the cumulative deformation, the recrystallization of the original B2 grains is promoted, and the average size is controlled to be 200~300μm. At the same time, water cooling or oil cooling is used for rapid cooling to suppress the precipitation of grain boundary α2 phase and coarse lamellar α2 phase, thereby obtaining fine lamellar α2 phase, which is beneficial to the spheroidization and refinement of α2 phase.

[0018] 3) Strictly control the upsetting and drawing deformation of the billet when it is deformed in the phase region below B2 phase region, effectively suppress the temperature rise of the billet core, which is conducive to improving the uniformity of the structure, improving the surface quality of the billet, and reducing machining losses.

[0019] 4) Pre-rolling and shaping is used to prepare ring-rolled billets. Compared with the scaffolding method, the deformation is more uniform, which is beneficial to improving the uniformity of the microstructure.

[0020] 5) Strictly controlling the deformation of the billet in a single ring rolling process is also beneficial to improving its surface quality and reducing machining losses.

[0021] 6) A triple heat treatment process is adopted. The first preheating treatment improves the uniformity of the forging structure and obtains a uniformly distributed subgrain structure. The second solution treatment obtains a suitable content of coarse lath α2 / O phase. The third aging treatment obtains a uniform fine lath O phase. Finally, a three-state structure composed of large-size B2 grains and small-size subgrain grains is obtained, achieving a good match between the alloy's thermal strength and thermal stability.

[0022] The Ti2AlNb-based alloy ring component prepared by this process exhibits a tri-phase microstructure consisting of large B2 grains and small subgrains, with good uniformity. The B2 grain size is controlled within the range of 200–300 μm, while the α2 grain size is controlled below 2 μm and is uniformly distributed. Based on this microstructure, the Ti2AlNb-based alloy ring component achieves excellent matching of thermal strength and thermal stability. The tensile strength at room temperature and 750℃ is no less than 1070 MPa and 730 MPa, respectively, with a room temperature tensile elongation of no less than 8%, a room temperature elongation of no less than 3% after 750℃ / 100h heat exposure, and a creep rupture time of no less than 25h at 750℃ / 250 MPa, meeting the service requirements of high-performance engines for stator components such as casing rings. Furthermore, the Ti2AlNb ring component manufacturing process is simple, has a short production cycle, and is suitable for large-scale industrial production. Attached Figure Description

[0023] Figure 1 This is a high-magnification microstructure photograph of the Ti2AlNb alloy ring in Example 1; Figure 2 This is a high-magnification microstructure photograph of the Ti2AlNb alloy ring in Example 2. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings. Those skilled in the art can make appropriate adjustments without departing from the spirit of the invention. The following embodiments illustrate the present invention in more detail, but do not limit the present invention in any way. The specific manufacturing process of the ring is as follows: Example 1

[0025] The ingot size of the Ti2AlNb-based alloy is Ф350×500mm, and the chemical composition is Ti-22.2Al-24.3Nb-0.49Mo. The alloy's T β The phase transition point is 1055℃. The specific preparation method for the ring component made from the ingot is as follows: Step 1): Heat the Ti2AlNb-based alloy ingot to 1160℃ using a resistance wire heating furnace, hold for 9 hours, remove from the furnace and shape to octagonal 320×575, upset to octagonal D×260 with a deformation of 55% and a pressing speed of 50mm / s, then draw to square 305×L, and then turn octagonal to 320×575; return to the furnace and hold for 3 hours, upset to octagonal D×260 with a deformation of 55% and a pressing speed of 50mm / s, then draw to square 305×L, and then turn octagonal to 320×575; return to the furnace and hold for 3 hours, upset to octagonal D×260 with a deformation of 55% and a pressing speed of 50mm / s, then draw to square 305×L, and then turn octagonal to 320×575, and then air cool after forging; Step 2): Heat the billet to 1080℃ using a resistance wire heating furnace, hold for 190 minutes, then remove from the furnace and upset to octagonal D×260 with a deformation of 55% at a pressing speed of 50mm / s. Draw it to square 305×L, then turn it to octagonal to 320×575. Continue upsetting to octagonal D×260 with a deformation of 55% at a pressing speed of 50mm / s, then draw it to square 305×L, then turn it to octagonal to 320×575. After forging, oil cool. Step 3): Heat the billet to 970℃ using a resistance wire heating furnace, hold for 260 minutes, and then upset it to an octagonal D×345 with a deformation of 40% and a reduction rate of 0.016s. -1 It was then drawn to a square shape of 305×L, and then turned into an octagonal shape of 320×575. The final forging temperature was 815℃, and it was air-cooled after forging. Step 4): Repeat step 3), with the final forging temperature at 800℃; Step 5): Heat the billet to 970℃ using a resistance wire heating furnace, hold for 260 minutes, then remove from the furnace and upset to an octagonal D×290 with a deformation of 50% and a pressing rate of 0.015s. -1 Punch 180mm holes, reheat in furnace for 60min, pre-roll to Ф460×Ф190×H290, deformation rate 0.008s. -1 After forging, air cool; Step 6): Heat the billet to 980℃ using a resistance wire heating furnace, hold for 110 minutes, and then ring roll it to Ф510×Ф280×H285 with a deformation rate of 0.01s. -1 Return to the furnace and hold for 40 minutes, then continue ring rolling to Ф555×Ф355×H285, with a deformation rate of 0.01s.-1 After forging, air cool; Step 7): Heat the billet to 1020℃ using a resistance wire heating furnace, hold for 140 min, and air-cool to room temperature; reheat to 970℃ in the furnace, hold for 200 min, and oil-cool to room temperature; reheat to 800℃ in the furnace, hold for 24 h, and air-cool. The resulting ring has dimensions Ф535×Ф375×H260.

[0026] Conclusion: The ring microstructure prepared in Example 1 is a three-state structure composed of large-sized B2 grains and small-sized subgrains, such as... Figure 1 As shown, the equiaxed α2 / O phase is uniformly distributed, with an average particle size of 1.8 μm, while the original B2 phase grains have an average size of 260 μm. The mechanical properties of the Ti2AlNb-based alloy rings prepared in this embodiment are shown in Table 1. They exhibit excellent short-term and long-term mechanical properties, and a good match between thermal strength and thermal stability.

[0027] Table 1 Mechanical properties of the Ti2AlNb alloy rings prepared in Example 1

[0028] Example 2

[0029] The Ti2AlNb-based alloy ingot has dimensions of Ф400×550mm and a chemical composition of Ti-21.8Al-24.1Nb-0.52Mo. The alloy's T... β The phase transition point is 1052℃. The specific method for preparing the ring from the ingot is as follows: Step 1): Heat the alloy ingot to 1160℃ using a resistance wire heating furnace, hold for 9 hours, remove from the furnace and shape to octagonal 360×645, upset to octagonal D×323 with a deformation of 50% and a pressing speed of 55mm / s, then draw to square 340×L, and then turn to octagonal 360×645; return to the furnace and hold for 3 hours, upset to octagonal D×323 with a deformation of 50% and a pressing speed of 55mm / s, then draw to square 340×L, and then turn to octagonal 360×645; return to the furnace and hold for 3 hours, upset to octagonal D×323 with a deformation of 50% and a pressing speed of 55mm / s, then draw to square 340×L, and then turn to octagonal 360×645, and then air cool after forging. Step 2): Heat the billet to 1090℃ using a resistance wire heating furnace, hold for 220 minutes, then remove from the furnace and upset to octagonal D×323 with a deformation of 50% and a pressing speed of 55mm / s. Then draw it to square 340×L, and turn it to octagonal 360×645. Continue to upset to octagonal D×323 with a deformation of 50% and a pressing speed of 55mm / s. Then draw it to square 340×L, turn it to octagonal 360×645, and water cool after forging. Step 3): Heat the billet to 1000℃ using a resistance wire heating furnace, hold for 290 minutes, then remove from the furnace and upset to an octagonal D×355 with a deformation of 45% and a reduction rate of 0.017s. -1 It was then drawn to a square shape of 340×L, and then turned into an octagonal shape of 360×645. The final forging temperature was 805℃, and it was air-cooled after forging.

[0030] Step 4): Repeat step 3), with the final forging temperature at 810℃; Step 5): Repeat step 3), with the final forging temperature at 800℃; Step 6): Heat the billet to 1000℃ using a resistance wire heating furnace, hold for 260 minutes, then remove from the furnace and upset to an octagonal D×325 with a deformation of 50% and a pressing rate of 0.015s. -1 Punch 200mm holes, reheat in furnace for 60min, pre-roll to Ф520×Ф210×H325, deformation rate 0.009s. -1 After forging, air cool; Step 7): Heat the billet to 1000℃ using a resistance wire heating furnace, hold for 125 minutes, and then ring roll it to Ф585×Ф325×H315 with a deformation rate of 0.009s. -1 Return to the furnace and hold for 45 minutes, then continue ring rolling to Ф615×Ф375×H315, with a deformation rate of 0.01s. -1 After forging, air cool; Step 8): Heat the billet to 1030℃ using a resistance wire heating furnace, hold for 160 min, and air-cool to room temperature; reheat to 960℃ in the furnace, hold for 220 min, and oil-cool to room temperature; reheat to 810℃ in the furnace, hold for 24 h, and air-cool. The resulting ring has a diameter of Ф600×Ф360×H300.

[0031] Conclusion: The ring microstructure prepared in Example 2 is a three-state structure composed of large-sized B2 grains and small-sized subgrains, such as... Figure 2 As shown, the equiaxed α2 / O phase is uniformly distributed, with an average particle size of 1.6 μm, while the original B2 phase grains have an average size of 275 μm. The mechanical properties of the Ti2AlNb-based alloy rings prepared in this embodiment are shown in Table 2. They exhibit excellent short-term and long-term mechanical properties, and a good match between thermal strength and thermal stability.

[0032] Table 2 Mechanical properties of the Ti2AlNb alloy rings prepared in Example 2

[0033] Matters not covered in this invention are common knowledge.

[0034] The above describes some implementation examples of the present invention, which are quite specific. Within the scope of the technical concept of the present invention, various modifications can be made to the technical solution of the present invention. These modifications all fall within the protection scope of the present invention.

Claims

1. A method for preparing a Ti2AlNb-based alloy ring, characterized in that, Includes the following steps: Step 1): Heat the ingot to 1150~1200℃, complete no less than two upsetting and two drawing forgings, the upsetting deformation is not less than 50%, the final forging temperature is not less than 850℃, and air cool after forging; Step 2): Heat the billet to 10-50°C above the β phase transformation point, perform two upsetting and two drawing processes, and the final forging temperature is not lower than 850°C. After forging, cool it with water or oil. Step 3): The billet is subjected to 1 to 3 upsetting and drawing forgings within a temperature range of 80 to 50°C below the β phase transformation point. The upsetting deformation is controlled at 40% to 50%, and the final forging temperature is not lower than 750°C. After forging, the billet is air-cooled. Step 4): Heat the billet to 80~50℃ below the β phase transformation point, perform upsetting, punching and pre-rolling shaping, and air cool after forging; Step 5): Heat the billet to 80~50℃ below the β phase transformation point, ring roll it to the target size, and air cool it after forging; Step 6): Perform preheating, solution treatment and aging treatment in sequence to obtain the ring blank, and finally obtain the finished ring by machining.

2. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: In step 1), the ingot is held at 1150~1200℃ for 15~24h, and the deformation rate during forging is not less than 40mm / s.

3. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: In step 2), the billet is forged using a continuous two-upsetting and two-drawing method, with a deformation speed of not less than 40 mm / s.

4. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: In step 3), forging is performed using a shaft upsetting and side-drawing method, and the upsetting deformation rate is no greater than 0.02s. -1 The deformation amount in a single elongation is less than 25%.

5. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: In step 4), the upsetting deformation rate is no greater than 0.02 s. -1 The pre-rolling rate is no more than 0.01s. -1 .

6. The present invention provides a process for preparing and heat-treating Ti2AlNb-based alloy rings according to claim 1, characterized in that: In step 5), the ring rolling deformation rate is no greater than 0.01 s. -1 The deformation amount in a single ring rolling operation is less than 15%.

7. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: In step 6), the preheating temperature is 50-10℃ below the phase change point, the holding time is 1-4h and then air cooling is performed; the solution treatment temperature is 120-80℃ below the phase change point, the holding time is 1-4h and then water cooling or oil cooling is performed; the aging treatment temperature is 780-850℃, the holding time is 12-24h and then air cooling is performed.

8. The method for preparing a Ti2AlNb-based alloy ring according to claim 1, characterized in that: The microstructure of the prepared Ti2AlNb-based alloy ring is a three-state structure consisting of large B2 grains and small subgrains, wherein the B2 grain size is 200~300μm and the α2 grain size is less than 2μm and uniformly distributed.

9. A method for preparing a Ti2AlNb-based alloy ring according to claim 8, characterized in that: The room temperature tensile strength of the Ti2AlNb-based alloy ring is not less than 1070 MPa, the 750℃ tensile strength is not less than 730 MPa, the room temperature tensile elongation is not less than 8%, the room temperature elongation after 750℃ / 100h heat exposure is not less than 3%, and the 750℃ / 250MPa endurance time is not less than 25h.

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