Preparation process of low-cost high-uniform-structure Ti2AlNb-based alloy large-specification bar

Abstract

The invention belongs to the field of titanium-based intermetallic compound processing, and particularly provides a low-cost high-uniform-structure Ti2AlNb-based alloy large-specification bar preparation process which comprises the following steps: step 1, heating a cast ingot to 1100-1200 DEG C to complete forging of not less than three times of upsetting and three times of drawing; 2, the blank is heated to 80-50 DEG C below the beta phase transformation point and subjected to upsetting, then the blank is returned to the furnace and heated to 10-50 DEG C above the beta phase transformation point, and drawing-out is conducted; thirdly, the blank is heated to 50-80 DEG C below the beta phase transformation point, and one-upsetting and one-drawing forging is completed for 2-4 times; and fourthly, the blank is heated to 50-80 DEG C below the beta phase transformation point, and finished product size drawing-out forging is completed. The Ti2AlNb-based alloy large-size bar prepared through the technology is good in structure uniformity, short in production period, low in cost and suitable for industrial production.

Description

Technical Field

[0001] This invention belongs to the field of titanium-based intermetallic compound processing, specifically involving a low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process. Background Technology

[0002] Ti2AlNb-based alloys exhibit higher specific strength compared to traditional nickel-based superalloys and superior high-temperature strength and oxidation resistance compared to traditional titanium-based superalloys, making them highly promising for applications in aerospace and other fields. However, the industrial production of Ti2AlNb-based alloys still faces numerous challenges that need to be addressed, including long production cycles, low yield rates, and high production costs.

[0003] The mixed bonding mechanism of metallic and covalent bonds leads to the brittle nature of Ti2AlNb-based alloys. The ordered structure of the B2, O, and α2 phases results in high deformation resistance, making them highly susceptible to cracking during processing, especially below the β-phase transformation point. The high deformation resistance and low specific heat capacity of Ti2AlNb-based alloys also make them prone to localized temperature rises during processing. Furthermore, the multi-phase composition of this alloy makes its microstructure highly sensitive to temperature, making it relatively difficult to control the microstructure uniformity of alloy bars, especially large-diameter bars. In addition, the high β-phase transformation point and low recrystallization tendency in the single-phase region of Ti2AlNb-based alloys make β-grain and B2-grain refinement difficult, further increasing the challenge of controlling microstructure uniformity.

[0004] The patent "A Ti2AlNb-based alloy rod and its preparation method and application" (Patent No.: 202111592182.2) discloses a method for preparing highly uniform rods using extrusion blanking and extrusion forming processes. However, this method requires sophisticated equipment and is not suitable for preparing large-size rods. The patent "A preparation process for large-size Ti2AlNb-based alloy rods with high uniformity and low loss" (Patent No.: CN202210370245.8) discloses a method for preparing highly uniform rods using multiple upsetting and drawing processes below the β phase transformation point. However, this process requires multiple upsetting and drawing deformations to achieve microstructure uniformity, resulting in numerous upsetting processes, long production cycles, and hindering production efficiency and cost control. Therefore, the key to the widespread application of this alloy lies in significantly reducing the number of forging processes, shortening the production cycle, and lowering production costs while ensuring improved microstructure uniformity in large-size Ti2AlNb-based alloy rods. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar manufacturing process. This method produces large-size bars that meet relevant technical requirements, exhibit good microstructure uniformity, have a short production cycle, and are low-cost. The specific technical solution is as follows: A low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar fabrication process includes the following steps: Step 1: Ingot forging; The Ti2AlNb-based alloy ingot is heated to 1100~1200℃ and subjected to no less than three upsetting and drawing cycles of forging, wherein the upsetting deformation amount is ≥50% each time, the final forging temperature is ≥850℃, and the forging is air-cooled. Step 2: Low-temperature upsetting and high-temperature drawing; The billet obtained in step one is heated to a temperature range of 50~80℃ below its β phase transformation point for low-temperature slow upsetting, requiring upsetting deformation ≥40% and final forging temperature ≥800℃. Then the billet is returned to the furnace and reheated to a temperature range of 10~50℃ below its β phase transformation point for high-temperature reversing elongation forging, with a final forging temperature ≥850℃, followed by air cooling. Step 3: Multi-fire low-temperature forging; The billet obtained in step two is heated to 50-80°C below the β phase transformation point and subjected to 2-4 independent upsetting and drawing forging cycles, wherein the upsetting deformation amount is ≥40% in each cycle and the final forging temperature is ≥750°C. After forging, it is air-cooled. Step 4: Finished product forming and forging; Finally, the billet obtained in step three is heated to a temperature range of 50~80℃ below its β phase transformation point, and then subjected to final elongation forging to obtain finished bar stock. The final forging temperature is ≥750℃, and the billet is air-cooled after forging.

[0006] The preferred embodiment of the low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process is as follows: in step one, the Ti2AlNb-based alloy ingot is held at 1100~1200℃ for ≥15h to ensure that the alloy is fully heated and homogenized.

[0007] The preferred embodiment of the low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process is as follows: In step two, the upsetting direction of the billet is axial upsetting and side upsetting; the upsetting deformation rate is ≤0.02s. -1 Excessive deformation rate can easily lead to temperature rise in the core of the billet, which is not conducive to improving the uniformity of the alloy structure.

[0008] The preferred embodiment of the low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process is as follows: In step three, the upsetting direction of the billet is axial upsetting and side upsetting; the upsetting deformation rate is ≤0.02s. -1To avoid temperature rise in the core of the billet and coarsening of the core structure, the drawing process is carried out in multiple stages, with a single drawing deformation of ≤25%. Excessive single drawing deformation can easily cause cracks on the surface of the billet, thereby increasing the amount of grinding and reducing the yield.

[0009] The preferred embodiment of the low-cost, high-uniformity Ti2AlNb-based alloy large-size bar preparation process is as follows: in step four, the elongation deformation during the preparation of finished size bars is less than 35% to avoid cracking of the bars, which would be detrimental to obtaining a high yield and thus increase production costs.

[0010] The preferred embodiment of the low-cost, high-uniformity Ti2AlNb-based alloy large-size bar preparation process is that steps one, two, and three constitute a complete forging sequence, with a total of 5 to 8 forging cycles throughout the entire process.

[0011] The preferred embodiment of the low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process is as follows: using this process, large-size Ti2AlNb-based alloy bars with a diameter of 300~450mm are obtained, and the size distribution variation coefficient of the α2 / O phase on the cross-section of the bar is ≤15%; after solution aging treatment, its tensile strength at room temperature is ≥1050 MPa, its tensile strength at 750℃ is ≥750 MPa, and its tensile strength at 800℃ is ≥600 MPa. Beneficial effects

[0012] The ingot forging process employs a forging technique involving multiple continuous large deformations to break up the as-cast structure. During the heat recovery period, the distortion generated by the deformation fully promotes element diffusion and simultaneously promotes static recrystallization to refine the grains.

[0013] 2) Low-temperature, slow-speed, large-deformation upsetting effectively suppresses the temperature rise in the core of the bar while refining the microstructure, which is beneficial for controlling the uniformity of the microstructure. Combined with the high-temperature reversing drawing process, static recrystallization of the bar can be promoted during the heating stage; during the drawing stage, the better fluidity of the metal at high temperatures can be utilized to effectively homogenize the microstructure of the alloy, improve the surface quality of the intermediate billet, and reduce grinding wear.

[0014] 3) Strictly control the elongation deformation during forging below the β phase transformation point to avoid excessive deformation that could cause cracks in the bar stock. This will help improve the surface quality of the bar stock, reduce machining losses, and increase the yield.

[0015] 4) The number of forging passes in this process is significantly reduced compared to the traditional process. The finished bar can be formed in 5 to 8 passes, shortening the preparation cycle and reducing production costs.

[0016] 5) Ti2AlNb alloy bars with diameters of 300~450mm prepared by this process have a uniform distribution of isometric α2 / O phases in the high-magnification microstructure of the forged bars, and the microstructure is well uniform along the diameter direction, i.e. from the core to the edge. After solution aging treatment, the room temperature and high temperature tensile properties are excellent.

[0017] In summary, the Ti2AlNb-based alloy large-size bars prepared using this patented process exhibit uniform equiaxed α2 / O phase distribution, good microstructure uniformity, and excellent mechanical properties at both room temperature and high temperature. Furthermore, the preparation cycle is short and the production cost is low, making it suitable for industrial production and aerospace applications. Attached Figure Description

[0018] Figure 1 This is a high-magnification microstructure photograph of the Ti2AlNb alloy rod in Example 1 of the present invention; Figure 2 This is a high-magnification microstructure photograph of the Ti2AlNb alloy rod in Example 2 of the present invention. Detailed Implementation

[0019] 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 preparation process of the bar material is as follows: Example 1

[0020] The ingot dimensions of the Ti2AlNb-based alloy are Ф345×1320mm, and the chemical composition is Ti-22.3Al-23.9Nb-0.51Mo. The alloy's T... β The phase transition point is 1060℃; A low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar fabrication process includes the following steps: Step 1: Heat the Ti2AlNb-based alloy ingot to 1150℃ using a resistance wire heating furnace and hold it at that temperature for a total of 15 hours. This process completes the three upsetting and three drawing forging in this heat treatment. The specific operation is as follows: Heat the alloy ingot to 1150℃ and hold for 9 hours. After removing it from the furnace, upset it to Φ515×590 with a deformation of 55% and an upsetting rate of 60mm / s. Then draw it to a square shape of 410×L and turn it into an octagonal shape of 440×788. After returning it to the furnace and holding it for 3 hours, upset it to an octagonal shape of D×355 with a deformation of 55% and an upsetting rate of 60mm / s. Then draw it to a square shape of 410×L and turn it into an octagonal shape of 440×788. After returning it to the furnace and holding it for 3 hours, upset it to an octagonal shape of D×355 with a deformation of 55% and an upsetting rate of 60mm / s. Then draw it to a square shape of 410×L and turn it into an octagonal shape of 440×788. The final forging temperature is 870℃, and it is air-cooled after forging. Step 2: Heat the billet obtained in Step 1 to 980℃ using a resistance wire heating furnace, hold for 360 minutes, and then remove from the furnace for axial upsetting. Upset to an octagonal D×470, with a deformation of 40%, and an upsetting reduction rate of 0.017s. -1 The final forging temperature is 820℃; the hot material is returned to the furnace and heated to 1085℃, held for 200 minutes, and then taken out of the furnace for lateral drawing, drawn to a square of 410×L and an octagon of 440×788, with a final forging temperature of 860℃, and then air-cooled after forging. Step 3: Heat the billet obtained in Step 2 to 980℃ using a resistance wire heating furnace, hold for 360 minutes, and then remove from the furnace for upsetting. Axially upset to an octagonal D×470, with a deformation of 40%, and an upsetting reduction rate of 0.017s. -1 Laterally drawn to a square shape of 410×L, and an inverted octagon shape of 440×788, with a final forging temperature of 810℃, followed by air cooling; Step 4: Heat the billet obtained in Step 2 to 980℃ using a resistance wire heating furnace, hold for 360 minutes, and then remove from the furnace for upsetting. Axially upset to an octagonal D×470, with a deformation of 40%, and an upsetting reduction rate of 0.017s. -1 Laterally drawn to a square shape of 410×L, and an octagonal shape of 440×788, with a final forging temperature of 805℃, followed by air cooling; Step 5: Heat the billet obtained in Step 4 to 980℃ using a resistance wire heating furnace, hold it at that temperature for 360 minutes, and then remove it from the furnace for forging into finished bar stock. Draw it to a square shape of 370×L, then draw it to a square shape of 325×L, then turn it into an octagonal shape of 330×L, and roll it to a round shape of Φ315×L. After machining, a Φ300 bar stock is obtained.

[0021] Conclusion: The microstructure of the rod prepared in Example 1 is a two-phase processed microstructure. The isometric α2 / O phases are uniformly distributed in the high-magnification microstructure, and the microstructure is uniformly distributed along the diameter direction. Figure 1 As shown in Table 1, the Ti2AlNb-based alloy rods prepared in this embodiment exhibit excellent tensile properties after solution treatment and aging. Table 1. Room temperature and high temperature tensile properties of Ti2AlNb alloy rods prepared in Example 1

[0022] Example 2 The ingot size for the Ti2AlNb-based alloy casting is Ф450×715mm, with a chemical composition of Ti-22.0Al-24.2Nb-0.50Mo. The alloy's T... β The phase transition point is 1055℃; A low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar fabrication process includes the following steps: Step 1: Heat the Ti2AlNb alloy ingot to 1160℃ using a resistance wire heating furnace, and hold it at that temperature for a total of 18 hours. This process involves four upsetting and four drawing operations. Specifically, the ingot is heated to 1160℃ and held for 9 hours. After being taken out of the furnace, it is upset to Φ635×358 with a deformation of 50% and an upsetting reduction rate of 55mm / s. It is then drawn to a square length of 400×L and an octagonal length of 410×816. It is then returned to the furnace and held for 3 hours. After being taken out of the furnace, it is upset to an octagonal length of D×370 with a deformation of 55% and an upsetting reduction rate of 55mm / s. The forging process was carried out at a speed of 55 mm / s, drawn to a square shape of 400×L, and then turned into an octagonal shape of 410×816. After being held in the furnace for 3 hours, the forging was upset to an octagonal shape of D×370 with a deformation of 55%. The upset rate was 55 mm / s. The forging process was carried out at a speed of 55 mm / s, drawn to a square shape of 400×L, and then turned into an octagonal shape of 410×816. After being held in the furnace for 3 hours, the forging process was carried out to an octagonal shape of D×370 with a deformation of 55%. The upset rate was 55 mm / s. The forging process was carried out to a square shape of 400×L, and then turned into an octagonal shape of 410×816. The final forging temperature was 835℃, and the forging was air-cooled after forging. Step 2: Heat the billet to 1000℃ using a resistance wire heating furnace, hold for 330 minutes, and then remove from the furnace for upsetting. Axially upset to an octagonal D×450, with a deformation of 45%, and an upsetting reduction rate of 0.02s. -1 The final forging temperature is 845℃; the hot material is returned to the furnace and heated to 1100℃, held for 160 minutes, and then taken out of the furnace for lateral drawing, drawn to a square shape of 400×L, and then turned into an octagonal shape of 410×816. The final forging temperature is 885℃, and the material is air-cooled after forging. Step 3: Heat the billet to 1000℃ using a resistance wire heating furnace, hold for 330 minutes, and then remove from the furnace for upsetting. Axially upset to an octagonal D×450, with a deformation of 45%, and an upsetting reduction rate of 0.02s. -1 Laterally elongated to a square shape of 400×L, then turned into an octagonal shape of 410×816, with a final forging temperature of 785℃, followed by air cooling. Step 4: Heat the raw material to 1000℃ using a resistance wire heating furnace, hold for 330 minutes, then remove from the furnace for upsetting. Axially upset to octagonal D×450, with a deformation of 45%, and an upsetting reduction rate of 0.02s-; laterally draw to square 400×L, then turn to octagonal to 410x816, with a final forging temperature of 792℃, followed by air cooling. Step 5: Heat the raw material to 1000℃ using a resistance wire heating furnace, hold for 330 minutes, then remove from the furnace for upsetting. Axially upset to octagonal D×450, with a deformation of 45%, and an upsetting reduction rate of 0.02s-; laterally draw to square 400×L, then turn to octagonal to 410x816, with a final forging temperature of 777℃, followed by air cooling. Step Six: Heat the raw material to 1000℃ using a resistance wire heating furnace, hold for 330 minutes, then remove from the furnace for upsetting. Axially upset to octagonal D×450, with a deformation of 45%, and an upsetting reduction rate of 0.02s-; laterally draw to square 400×L, then turn to octagonal to 410x816, with a final forging temperature of 777℃, followed by air cooling. Step 7: Heat the billet obtained in Step 6 to 1000℃ using a resistance wire heating furnace, hold it at that temperature for 330 minutes, and then remove it from the furnace to forge the finished bar. Roll it into a diameter of Φ410×L and then machine it to obtain a bar with a diameter of Φ400mm.

[0023] Conclusion: The microstructure of the rod prepared in Example 2 is a two-phase processed microstructure. The isometric α2 / O phases are uniformly distributed in the high-magnification microstructure, and the microstructure is uniformly distributed along the diameter direction. Figure 2 As shown in Table 2, the Ti2AlNb-based alloy rods prepared in this embodiment exhibit excellent tensile properties after solution treatment and aging. Table 2. Room temperature and high temperature tensile properties of the Ti2AlNb-based alloy rods prepared in Example 2

[0024] Matters not covered in this invention are common knowledge.

[0025] 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 low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process, characterized in that, Includes the following steps: Step 1: Ingot forging; The Ti2AlNb-based alloy ingot is heated to 1100~1200℃ and subjected to no less than three upsetting and drawing cycles of forging, wherein the upsetting deformation amount is ≥50% each time, the final forging temperature is ≥850℃, and the forging is air-cooled. Step 2: Low-temperature upsetting and high-temperature drawing; The billet obtained in step one is heated to a temperature range of 50~80℃ below its β phase transformation point for low-temperature slow upsetting, requiring upsetting deformation ≥40% and final forging temperature ≥800℃. Then the billet is returned to the furnace and reheated to a temperature range of 10~50℃ below its β phase transformation point for high-temperature reversing elongation forging, with a final forging temperature ≥850℃, followed by air cooling. Step 3: Multi-fire low-temperature forging; The billet obtained in step two is heated to 50-80°C below the β phase transformation point and subjected to 2-4 independent upsetting and drawing forging cycles, wherein the upsetting deformation amount is ≥40% in each cycle and the final forging temperature is ≥750°C. After forging, it is air-cooled. Step 4: Finished product forming and forging; Finally, the billet obtained in step three is heated to a temperature range of 50~80℃ below its β phase transformation point, and then subjected to final elongation forging to obtain finished bar stock. The final forging temperature is ≥750℃, and the billet is air-cooled after forging.

2. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: In step one, the Ti2AlNb alloy ingot is held at 1100~1200℃ for ≥15h.

3. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: In step two, the billet is upset in the axial direction, and the upsetting deformation rate is ≤0.02s. -1 .

4. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: In step three, the upsetting direction of the billet is axial upsetting and the upsetting deformation rate is ≤0.02s. -1 The elongation process is carried out in multiple stages, with a single elongation deformation amount of ≤25%.

5. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: In step four, the elongation deformation during the preparation of finished size bars shall be ≤35%.

6. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: Steps one, two, and three constitute a complete forging sequence, with a total of 5 to 8 forging cycles throughout the entire process.

7. The low-cost, highly uniform microstructure Ti2AlNb-based alloy large-size bar preparation process according to claim 1, characterized in that: Using this preparation process, large-diameter Ti2AlNb-based alloy bars with diameters of 300~450mm were obtained. The coefficient of variation of the size distribution of the α2 / O phase on the cross-section of the bars was ≤15%. After solution treatment and aging, the tensile strength at room temperature was ≥1050 MPa, the tensile strength at 750℃ was ≥750 MPa, and the tensile strength at 800℃ was ≥600 MPa.

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