A method for producing a TiAl-based alloy rod based on a pouring type can

Abstract

This invention belongs to the field of alloy material forming technology, specifically relating to a method for preparing TiAl-based alloy rods based on a cast-in-place cladding. The method includes the following steps: providing a cast-in-place integral titanium alloy cladding, the cladding having an extrusion end; placing a TiAl ingot billet inside the cast-in-place integral titanium alloy cladding, sealing it to obtain a cladding / TiAl billet; subjecting the billet to two hot extrusion passes; and machining to obtain TiAl-based alloy rods. This invention uses a cast-in-place integral titanium alloy cladding to encase the ingot billet, forming a two-layer "cladding / TiAl" structure. This reduces the degree of rheological stress mismatch between the cladding and the TiAl alloy during extrusion. After the first hot extrusion deformation, a metallurgical bond is formed between the cladding and TiAl, reducing the friction between the cladding and the TiAl billet during subsequent hot extrusion passes. This further reduces the risk of cladding cracking and TiAl billet oxidation, and the cladding can be reused in multiple hot extrusion passes.

Description

Technical Field

[0001] This invention belongs to the field of alloy material forming technology, specifically relating to a method for preparing TiAl-based alloy rods based on casting-type cladding. Background Technology

[0002] TiAl-based alloys possess characteristics such as high specific strength, high specific stiffness, good creep resistance, and high-temperature oxidation resistance, making them the most promising new type of lightweight high-temperature structural material that is closest to practical application.

[0003] Significant breakthroughs have been made in the research of TiAl alloys, but many challenges remain in practical engineering applications, such as poor thermoplastic deformation capacity, high processing difficulty, microstructural instability during high-temperature service (≥750℃), and insufficient oxidation resistance at high temperatures (≥800℃). Among these, the difficulty of hot processing is particularly prominent. Therefore, exploring reasonable, economical, and efficient preparation and processing technologies for high-performance, large-size TiAl alloys has become an urgent problem to be solved in the field of TiAl alloy research. Analysis of hot processing characteristics shows that during extrusion, the material in the plastic deformation zone is under triaxial compressive stress. This stress state can fully utilize the material's plasticity and suppress crack initiation, making it very suitable for processing difficult-to-deform TiAl alloys.

[0004] However, even at extrusion temperatures of 1150℃~1350℃, the rheological stress of TiAl alloys remains as high as 200MPa~400MPa. Under the rigid coupling effect of such high rheological stress, intrinsic low plasticity, strong extrusion friction, and equipment limits, the extrusion ratio of TiAl alloys can only be selected as 3~5. This single-pass, small-deformation extrusion method is difficult to obtain TiAl alloy bars with fine and uniform microstructure and excellent performance, and multi-pass extrusion is usually required. However, the traditional TiAl alloy clad extrusion billet is a multi-layer assembly structure of stainless steel / metal foil isolation layer / TiAl. When extruding large-size TiAl billets, the interlayer friction is large, the required extrusion pressure is large, and problems such as incoordination between the cladding and the TiAl billet deformation and cladding cracking are very likely to occur. Moreover, the cladding can only be used once, and it must be unpacked and re-clad for subsequent processing, which is a complex and costly process and is not suitable for multi-pass, large-deformation extrusion of large-size TiAl billets. Summary of the Invention

[0005] To address the problems of incoordination between the existing cladding and TiAl billet deformation, cladding cracking, and the need for re-cladding in subsequent processing passes, resulting in complex and costly processes, this invention provides a method for preparing TiAl-based alloy bars based on a cast-in-place cladding. By using a cast-in-place integral titanium alloy cladding to encase the billet, a two-layer extrusion billet with a "titanium alloy cladding / TiAl" structure is formed. The extrusion die angle at the extrusion end reduces the degree of rheological stress mismatch between the cladding and the TiAl alloy during extrusion, preventing cladding cracking. The cladding structure is simple, with no circumferential weld at the extrusion end, resulting in low interlayer friction and reducing the risk of cladding cracking during the first hot extrusion pass. Simultaneously, the required extrusion pressure is also lower. After the first hot extrusion deformation, the cladding and TiAl form a good metallurgical bond, making the deformation more uniform during subsequent extrusions, further reducing the risk of cladding cracking and TiAl billet oxidation. No repeated cladding is required for multi-pass extrusion, making the process simple, efficient, and suitable for multi-pass, large-deformation extrusion of large-size TiAl alloys.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] The purpose of this invention is to provide a method for preparing TiAl-based alloy rods based on casting-type cladding, comprising the following steps: S1. A cast integral titanium alloy sheath is provided, wherein the cast integral titanium alloy sheath is provided with an extrusion end, and the angle between the inner wall of the extrusion end and the axis is 50°~70°.

[0008] In this invention, a cast integral titanium alloy sheath is provided through a reasonable sheath design, which reduces the risk of sheath cracking during the first hot extrusion. The cast integral titanium alloy sheath is formed by melting and casting in a vacuum consumable furnace. During the melting and casting process, the vacuum degree is ≤1Pa, the current is 16KA~22KA, the voltage is 25V~40V, and the leakage rate is ≤0.8Pa / min. The outer wall of the extrusion end is at the same bevel angle as the lower die angle during the extrusion process. The angles of the outer wall and the inner wall of the extrusion end can be the same or different, as long as the angle between the inner wall and the axis is 50°~70°. This reduces the degree of rheological stress mismatch between the sheath and the TiAl alloy during extrusion and avoids sheath cracking during extrusion.

[0009] In some embodiments, the material of the cast integral titanium alloy cladding includes, but is not limited to, TC4, TA15, or TC21. The extrusion end of the cast integral titanium alloy cladding has no circumferential weld, and the end furthest from the extrusion end is open. The TiAl ingot is placed inside the cast integral titanium alloy cladding and sealed with a matching end cap. The sealing is performed using vacuum electron beam welding, with a vacuum level not exceeding 5 × 10⁻⁶. -3 Pa. That is, there is no circumferential weld at the extrusion end, only one weld between the top of the billet and the end cap.

[0010] S2. Place the TiAl ingot billet inside a cast integral titanium alloy cladding and seal it to obtain a two-layer structure cladding / TiAl billet. Perform two hot extrusions on the billet in sequence. After the first hot extrusion, a metallurgical bond is formed between the cast integral titanium alloy cladding and the TiAl billet. After the extrusion is completed, perform machining to obtain TiAl-based alloy rods.

[0011] In this invention, a two-layer extruded billet, consisting of a titanium alloy cladding and a TiAl layer, is formed by cladding the billet with a cast integral titanium alloy. The extrusion die angle at the extrusion end reduces the rheological stress mismatch between the cladding and the TiAl alloy during extrusion, thus preventing cladding cracking. The extrusion end has no circumferential weld, resulting in low interlayer friction and reducing the risk of cladding cracking during the first hot extrusion pass, while also requiring less extrusion pressure. After the first hot extrusion deformation, the cladding and TiAl form a good metallurgical bond, leading to more uniform deformation during subsequent extrusions and further reducing the risk of cladding cracking and TiAl billet oxidation. Through multi-pass, high-deformation extrusion, a TiAl alloy bar with good surface quality, fine and uniform microstructure, and excellent performance is finally obtained.

[0012] In this invention, after the first hot extrusion, the oxide layer on the surface of the cladding can be removed by machining, and the remaining cladding can be used directly without secondary cladding. The operation is simple and efficient. That is, the cladding can be reused in multiple extrusions without repeated cladding. The process is simple and efficient, and it is suitable for multi-pass, large deformation extrusion of large-size TiAl alloys.

[0013] In some embodiments, the wall thickness of the cast integral titanium alloy cladding is 6% to 15% of the TiAl ingot diameter D1. In this invention, the cast integral titanium alloy cladding thins after the first hot extrusion pass. If it is too thin, it cannot meet the functional requirements of the cladding during subsequent extrusion passes; if it is too thick, the extrusion strain is mainly concentrated at the cladding, reducing the deformation of TiAl. Within this parameter range, the above two factors can be coordinated.

[0014] In some embodiments, the extrusion ratio of the first hot extrusion pass does not exceed 7. In this invention, during the first hot extrusion pass, the external structure of the TiAl billet and the internal structure of the casing are consistent. TiAl alloy is a low intrinsic brittle alloy. Therefore, the extrusion ratio of the first hot extrusion pass is ≤7. When the extrusion ratio is greater than 7, the required extrusion pressure is too large, exceeding the capacity of existing equipment. The core flow is slow and the surface extrusion speed is fast during the extrusion process, resulting in uneven microstructure, including uneven core and surface microstructure and microstructure anisotropy. If the extrusion ratio is too large, defects such as cracks are easily generated on the surface of the bar, and the extrusion tail phenomenon is aggravated.

[0015] In some embodiments, the extrusion ratio for the second hot extrusion is no more than 10. In this invention, after the first hot extrusion, the as-cast structure is broken up, and the hot working properties of the alloy are improved. Therefore, the extrusion ratio can be increased to 10. However, if it is too high, defects such as uneven structure, anisotropy, surface cracks, and extrusion tails will still occur.

[0016] In some embodiments, during the first and second hot extrusion processes, the heating temperature is 1150℃~1350℃, and the billet holding time is (0.6×D2) min~(0.6×D2+180) min, where D2 is the outer diameter of the cast integral titanium alloy cladding. In this invention, after the first hot extrusion, the oxide scale on the surface of the cladding after the first hot extrusion is removed by machining. The two end faces of the billet need to be machined flat, and then the two ends of the billet are vacuum electron beam sealed with two end caps. The end cap of the extrusion end needs to have the same bevel angle as the extrusion die angle. Then, the second hot extrusion is performed. Before the second hot extrusion, the surface of the billet is coated with an anti-oxidation coating, and after natural drying, it is placed in the furnace for heating.

[0017] Compared with the prior art, the present invention has the following advantages: (2) The method for preparing TiAl-based alloy rods based on casting-type cladding provided by this invention uses a casting-type integral titanium alloy cladding to clad the TiAl ingot, forming a two-layer extrusion billet with a "titanium alloy cladding / TiAl" structure. The casting-type integral titanium alloy cladding has a simple structure and low interlayer friction. By reducing the extrusion die angle at the extrusion end, the degree of rheological stress mismatch between the cladding and the TiAl alloy during extrusion is reduced, avoiding cladding cracking during extrusion. The cladding structure is simple, with no circumferential weld at the extrusion end, resulting in low interlayer friction and reducing the risk of cladding cracking during the first hot extrusion. At the same time, the required extrusion pressure is also lower. After deformation by the first hot extrusion, the cladding and TiAl form a good metallurgical bond, making the deformation of both more uniform during subsequent extrusion, further reducing the risk of cladding cracking and TiAl billet oxidation. The cladding preparation method proposed in this invention does not require repeated cladding during multi-pass hot extrusion. The process is simple and efficient, and suitable for multi-pass, large-deformation extrusion of large-size TiAl alloys.

[0018] (3) The integral cast titanium alloy cladding extrusion end of this invention has no circumferential weld, and is only sealed at the end cap, which reduces the risk of cladding cracking during the first hot extrusion. After the first hot extrusion, the oxide layer on the cladding surface can be removed by machining, and the remaining cladding can be used directly without secondary cladding, making the operation simple and efficient. Through the deformation of the first hot extrusion, a metallurgical bond is formed between the cladding and TiAl, reducing the friction between the cladding and TiAl billet during subsequent extrusions, and significantly improving the deformation coordination between the two. After extrusion, the cladding does not crack and the billet does not oxidize. Through the above-mentioned multi-pass, large deformation extrusion, TiAl alloy rods with good surface quality, fine and uniform structure, and excellent performance are finally obtained. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the integral titanium alloy cladding structure of the present invention.

[0020] Figure 2 This is a physical image of the integral titanium alloy sheath cast after sealing and welding according to Embodiment 1 of the present invention.

[0021] Figure 3 This is a surface quality diagram of the billet after the first hot extrusion in Embodiment 1 of the present invention. Figure 3 Figure a shows the result after hot pressing, and Figure b shows the result after hot pressing and cooling.

[0022] Figure 4 This is a cross-sectional view of the billet after the first hot extrusion in Embodiment 1 of the present invention.

[0023] Figure 5 This is a cross-sectional view of the billet after the second hot extrusion in Embodiment 1 of the present invention.

[0024] Figure 6 This is a cross-sectional view of the TiAl-based alloy rod prepared in Example 1 of the present invention.

[0025] Figure 7 The image shows the metallographic structure of the TiAl-based alloy rod prepared in Example 1 of this invention. Detailed Implementation

[0026] 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.

[0027] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0028] The following specific examples will provide further explanation.

[0029] Example 1 A method for preparing TiAl-based alloy rods based on casting-type cladding includes the following steps: S1. Provide a castable integral titanium alloy cladding, using TC4 ingots as raw material, cast in a vacuum solidification furnace. During casting, the vacuum degree is ≤1 Pa, the current is 16 kA~22 kA, the voltage is 25 V~40 V, and the leakage rate is ≤0.8 Pa / min. The castable integral TC4 titanium alloy cladding is as follows: Figure 1 As shown, the cast integral TC4 titanium alloy cladding 1 has an outer diameter of 250 mm and a wall thickness of 25 mm. The upper end cap 3 has a diameter of Ф250 mm and a thickness of 30 mm. The cast integral titanium alloy cladding is equipped with an extrusion end 5, the inner wall of which makes an angle of 60° with the axis, and the end away from the extrusion end is open. γ-TiAl alloy with a diameter of Ф220 mm is prepared by three-stage vacuum consumable arc melting, and then machined to Ф200 mm.

[0030] S2, such as Figure 1 and Figure 2 As shown, the TiAl ingot 2 is placed inside the cast integral titanium alloy sheath 1, and sealed with a matching upper end cap 3. The sealing is performed using vacuum electron beam welding, with a vacuum degree not exceeding 5 × 10⁻⁶. -3 Pa, meaning there is no circumferential weld at the extrusion end, only one weld 4 at the top of the billet and the end cap, and the weld is machined to be consistent with the outer diameter of the cladding, thus obtaining a two-layer cladding / TiAl billet.

[0031] S3. First Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1250℃, and the billet is held at this temperature for 255 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 5500T horizontal extrusion press is used for the first hot extrusion. The extrusion cylinder diameter is 255mm, the extrusion die diameter is 127mm, the die angle is 60°, and the first hot extrusion ratio is 4. The extrusion cylinder is preheated to 280℃, and lubricant is applied to the surfaces of the extrusion cylinder and die. A glass pad is inserted, and the first hot extrusion begins. The extrusion speed is 29mm / s, the upsetting force during the extrusion process is 2800T, and the stabilization stage extrusion force is 2000T. After the first hot extrusion, as follows... Figure 3 As shown, Figure 3In the diagram, 'a' represents the product after hot pressing, and 'b' represents the product after hot pressing and cooling. After extrusion, the casing shows no cracks and has good surface quality. For example... Figure 4 As shown, the integral TC4 titanium alloy cladding, after extrusion and casting, is thinned from 20mm to 8mm, and the TC4 cladding has a good interface with the TiAl billet.

[0032] S4. Post-extrusion treatment: Machining removes the oxide scale from the surface of the casing after the first hot extrusion. The outer diameter of the machined billet is 118mm. The two end faces of the billet after the first hot extrusion need to be machined flat. Then, two end caps are used to vacuum electron beam seal the two ends of the billet. The end caps at the extrusion end need to have the same bevel angle as the lower extrusion die angle. The welding vacuum degree is 5×10⁻⁶. -3 Pa, awaiting the second hot extrusion.

[0033] S5. Second Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1250℃, and the billet is held at this temperature for 200 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 2800T horizontal extrusion press is used for the second hot extrusion. The extrusion cylinder diameter is 120mm, the lower die is 45mm, the die angle is 60°, and the second hot extrusion ratio is 7. The extrusion cylinder is preheated to 400℃. Lubricant is applied to the surfaces of the extrusion cylinder and the extrusion die. Upper and lower glass pads are added, and the second hot extrusion begins. The extrusion speed is 30mm / s, and the upsetting force during extrusion is 1230T. After the second hot extrusion, as follows... Figure 5 As shown, the sheath is not cracked, and the TiAl surface still retains part of the sheath, about 1 mm thick.

[0034] S6. After the second hot extrusion, the residual cladding on the TiAl surface is removed by polishing to obtain the finished TiAl bar. Figure 6 As shown. The microstructure of the finished TiAl bar after the second hot extrusion is as follows. Figure 7 As shown, the microstructure is fine and uniform when viewed at 100x magnification.

[0035] The room temperature and high temperature mechanical properties of TiAl bars after two hot extrusions are shown in Table 1. As shown in Table 1, the mechanical properties of the bars after two hot extrusions are excellent.

[0036] Table 1 Mechanical property results of TiAl rods in Example 1 Example 2 A method for preparing TiAl-based alloy rods based on casting-type cladding includes the following steps: S1. A cast-integral titanium alloy cladding is provided, using TC4 ingots as raw materials. The integral TC4 titanium alloy cladding is cast in a vacuum solidification furnace. During casting, the vacuum degree is ≤1 Pa, the current is 16 kA~22 kA, the voltage is 25 V~40 V, and the leakage rate is ≤0.8 Pa / min. The cast-integral TC4 titanium alloy cladding 1 has an outer diameter of 246 mm and a wall thickness of 15 mm. The upper end cap 3 has a diameter of Ф246 mm and a thickness of 30 mm. The cast-integral titanium alloy cladding has an extrusion end 5, with the inner wall of the extrusion end forming an angle of 60° with the axis. The end furthest from the extrusion end is open. γ-TiAl alloy with a diameter of Ф220 mm is prepared by three-stage vacuum consumable arc melting, and then machined to Ф216 mm.

[0037] S2, such as Figure 1 and Figure 2 As shown, the TiAl ingot 2 is placed inside the cast integral titanium alloy sheath 1, and sealed with a matching upper end cap 3. The sealing is performed using vacuum electron beam welding, with a vacuum degree not exceeding 5 × 10⁻⁶. -3 Pa, meaning there is no circumferential weld at the extrusion end, only one weld 4 at the top of the billet and the end cap, and the weld is machined to be consistent with the outer diameter of the cladding, thus obtaining a two-layer cladding / TiAl billet.

[0038] S3. First Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1250℃, and the billet is held at this temperature for 255 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 5500T horizontal extrusion press is used for the first hot extrusion. The extrusion cylinder diameter is 255mm, the extrusion die diameter is 127mm, the die angle is 60°, and the first hot extrusion ratio is 4. The extrusion cylinder is preheated to 280℃, and the surfaces of the extrusion cylinder and die are coated with lubricant. A glass pad is then inserted, and the first hot extrusion begins. The extrusion speed is 29mm / s, the upsetting force during the extrusion process is 2850T, and the stabilization stage extrusion force is 2010T. After the first hot extrusion, the cladding shows no cracking, and the surface quality is good.

[0039] S4. Post-extrusion treatment: Machining removes the oxide scale from the surface of the casing after the first hot extrusion. The outer diameter of the machined billet is 118mm. The two end faces of the billet after the first hot extrusion need to be machined flat. Then, two end caps are used to vacuum electron beam seal the two ends of the billet. The end caps at the extrusion end need to have the same bevel angle as the lower extrusion die angle. Finally, the two end caps are vacuum-sealed to the billet with a welding vacuum degree of 5×10⁻⁶. -3 Pa, awaiting the second hot extrusion.

[0040] S5. Second Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1250℃, and the billet is held at this temperature for 200 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 2800T horizontal extrusion press is used for the second hot extrusion. The extrusion cylinder diameter is 120mm, the lower die is 45mm, the die angle is 60°, and the second hot extrusion ratio is 7. The extrusion cylinder is preheated to 400℃, and lubricant is applied to the surfaces of the extrusion cylinder and die. Upper and lower glass pads are added, and the second hot extrusion begins. The extrusion speed is 30mm / s, and the upsetting force during extrusion is 1250T. After the second hot extrusion, the cladding shows no cracking, and a portion of the cladding, approximately 0.5mm thick, remains on the TiAl surface.

[0041] S6. After the second hot extrusion, the residual cladding on the TiAl surface is removed by polishing to obtain the finished TiAl bar with a fine and uniform microstructure.

[0042] The room temperature and high temperature mechanical properties of TiAl bars after two hot extrusions are shown in Table 2. As shown in Table 2, the mechanical properties of the bars after two hot extrusions are excellent.

[0043] Table 2 Mechanical property results of TiAl rods in Example 2 Example 3 A method for preparing TiAl-based alloy rods based on casting-type cladding includes the following steps: S1. Provide a castable integral titanium alloy cladding, using TC4 ingots as raw material, cast in a vacuum solidification furnace. During casting, the vacuum degree is ≤1 Pa, the current is 16 kA~22 kA, the voltage is 25 V~40 V, and the leakage rate is ≤0.8 Pa / min. The castable integral TC4 titanium alloy cladding is as follows: Figure 1 As shown, the cast integral TC4 titanium alloy cladding 1 has an outer diameter of 250 mm and a wall thickness of 25 mm. The upper end cap 3 has a diameter of Ф250 mm and a thickness of 30 mm. The cast integral titanium alloy cladding is equipped with an extrusion end 5, the inner wall of which makes an angle of 60° with the axis, and the end away from the extrusion end is open. γ-TiAl alloy with a diameter of Ф220 mm is prepared by three-stage vacuum consumable arc melting, and then machined to Ф200 mm.

[0044] S2, such as Figure 1 and Figure 2 As shown, the TiAl ingot 2 is placed inside the cast integral titanium alloy sheath 1, and sealed with a matching upper end cap 3. The sealing is performed using vacuum electron beam welding, with a vacuum degree not exceeding 5 × 10⁻⁶. -3Pa, meaning there is no circumferential weld at the extrusion end, only one weld 4 at the top of the billet and the end cap, and the weld is machined to be consistent with the outer diameter of the cladding, thus obtaining a two-layer cladding / TiAl billet.

[0045] S3. First Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1250℃, and the billet is held at this temperature for 255 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 5500T horizontal extrusion press is used for the first hot extrusion. The extrusion cylinder diameter is 255mm, the extrusion die diameter is 127mm, the die angle is 60°, and the first hot extrusion ratio is 4. The extrusion cylinder is preheated to 280℃, and the surfaces of the extrusion cylinder and die are coated with lubricant. A glass pad is then inserted, and the first hot extrusion begins. The extrusion speed is 29mm / s, the upsetting force during the extrusion process is 2800T, and the stabilization stage extrusion force is 2000T. After the first hot extrusion, the cladding shows no cracking, and the surface quality is good.

[0046] S4. Post-extrusion treatment: Machining removes the oxide scale from the surface of the casing after the first hot extrusion. The outer diameter of the machined billet is 118mm. The two end faces of the billet after the first hot extrusion need to be machined flat. Then, two end caps are used to vacuum electron beam seal the two ends of the billet. The end caps at the extrusion end need to have the same bevel angle as the lower extrusion die angle. Finally, the two end caps are vacuum-sealed to the billet with a welding vacuum degree of 5×10⁻⁶. -3 Pa, awaiting the second hot extrusion.

[0047] S5. Second Hot Extrusion: The billet surface is coated with an anti-oxidation coating and allowed to dry naturally before being placed in a cold furnace. Heating begins at 1350℃, and the billet is held at this temperature for 200 minutes. After holding, the billet is coated with glass powder lubricant and ready for extrusion. A 2800T horizontal extrusion press is used for the second hot extrusion. The extrusion cylinder diameter is 120mm, the lower die is 38mm, the die angle is 60°, and the second hot extrusion ratio is 10. The extrusion cylinder is preheated to 400℃, and lubricant is applied to the surfaces of the extrusion cylinder and die. Upper and lower glass pads are added, and the second hot extrusion begins. The extrusion speed is 30mm / s, and the upsetting force during extrusion is 1293T. After the second hot extrusion, the cladding shows no cracking, and a portion of the cladding, approximately 1mm thick, remains on the TiAl surface.

[0048] S6. After the second hot extrusion, the residual cladding on the TiAl surface is removed by polishing to obtain the finished TiAl bar with a fine and uniform microstructure.

[0049] The room temperature and high temperature mechanical properties of TiAl bars after two hot extrusions are shown in Table 3. As shown in Table 3, the mechanical properties of the bars after two hot extrusions are excellent.

[0050] Table 3 Mechanical property results of TiAl rods in Example 3 It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0051] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing TiAl-based alloy rods based on casting-type cladding, characterized in that, Includes the following steps: A cast integral titanium alloy sheath is provided, wherein the cast integral titanium alloy sheath is provided with an extrusion end, and the angle between the inner wall of the extrusion end and the axis is 50°~70°. The extrusion end of the cast integral titanium alloy cladding has no circumferential weld, and the end furthest from the extrusion end is open. The TiAl ingot is placed inside the cast integral titanium alloy cladding and sealed with a matching end cap. The sealing is performed using vacuum electron beam welding, with a vacuum degree not exceeding 5×10⁻⁶. -3 Pa, to obtain a two-layer structured cladding / TiAl billet, the billet is subjected to two hot extrusions in sequence, wherein after the first hot extrusion, a metallurgical bond is formed between the cast integral titanium alloy cladding and the TiAl billet, and after the extrusion is completed, machining is performed to obtain TiAl-based alloy rods. The wall thickness of the cast integral titanium alloy cladding is 6% to 15% of the diameter D1 of the TiAl ingot; The first hot extrusion has an extrusion ratio not exceeding 7. The second hot extrusion has an extrusion ratio not exceeding 10. During the first and second hot extrusion processes, the heating temperature is 1150℃~1350℃, and the billet holding time is (0.6×D2)min~(0.6×D2+180)min, where D2 is the outer diameter of the cast integral titanium alloy cladding. The material of the cast integral titanium alloy cladding is TC4, TA15 or TC21.

2. The method for preparing TiAl-based alloy rods based on casting-type cladding according to claim 1, characterized in that, The integral titanium alloy cladding is formed by vacuum arc remelting furnace melting and casting. During the melting and casting process, the vacuum degree is ≤1Pa, the current is 16KA~22KA, the voltage is 25V~40V, and the leakage rate is ≤0.8Pa / min.

3. The method for preparing TiAl-based alloy rods based on casting-type cladding according to claim 1, characterized in that, The outer wall of the extrusion end is at the same bevel angle as the lower die angle during the extrusion process.

4. The method for preparing TiAl-based alloy rods based on casting-type cladding according to claim 1, characterized in that, Before the first and second hot extrusions, an anti-oxidation coating is applied to the surface of the billet. After the heat preservation is completed, glass powder lubricant is applied by roller.

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