High impact resistance Ti 2 AlNb alloy medium-thick plates and their preparation methods

Abstract

This invention discloses high impact-resistant Ti 2 The method for preparing medium-thick AlNb alloy plates is as follows: Step 1: Using NbTi master alloy, HTi, Al alloy, and Mo65Al master alloy as raw materials, all raw materials are pressed into an electrode block and subjected to three VAR melting processes; Step 2: Ti alloy is prepared using a free forging method. 2 AlNb alloy free forging slab; Step 3: Using hot rolling method, Ti 2 AlNb alloy free-forged slabs are rolled into Ti 2 AlNb alloy medium-thick slabs are then straightened; Step 4: The straightened Ti... 2 AlNb alloy medium-thick slabs undergo double heat treatment followed by machining to obtain Ti. 2 AlNb alloy medium-thick plate finished product. This method solves the problem of existing Ti 2 AlNb alloy plates suffer from insufficient impact resistance, complex preparation processes, and poor microstructure uniformity. High-impact Ti alloys were also disclosed. 2 AlNb alloy medium-thick plate.

Description

High impact resistant Ti2AlNb alloy medium-thick plate and its preparation method Technical Field

[0001] This invention belongs to the field of alloy processing technology, specifically relating to high impact-resistant Ti2AlNb alloy medium-thick plates, and also to a method for preparing high impact-resistant Ti2AlNb alloy medium-thick plates. Background Technology

[0002] Ti2AlNb alloy, as an intermetallic compound, has become a highly promising lightweight high-temperature structural material in the aerospace field due to its low density, high specific strength, excellent high-temperature creep resistance and good oxidation resistance. Its application can help significantly reduce the weight of aerospace systems and improve the performance of application components.

[0003] However, traditional methods for preparing this alloy face numerous challenges. Casting metallurgy methods easily result in coarse as-cast structures with poor mechanical properties, necessitating forging to refine the grains. Ti2AlNb alloys have a narrow hot working window and low room-temperature plasticity. Rapid temperature drops during hot rolling lead to a sharp increase in deformation resistance and a significant tendency to crack; therefore, cladding rolling is often employed. While this process can alleviate cracking, it suffers from drawbacks such as complex processes, high production costs, and poor surface quality, severely restricting its large-scale industrial application.

[0004] To overcome these limitations, some improved technologies have emerged, such as unencased fabrication, multi-pass hot rolling combined with aging treatment, and additive manufacturing (e.g., selective laser melting). However, they still fall short in achieving high impact resistance. Unencased rolling and optimized thermomechanical treatment can improve strength and plasticity to some extent, but their improvement on impact toughness and crack propagation resistance, which are crucial for medium and thick plates, is limited. Additive manufacturing technology is limited by the challenges of internal stress concentration, crack sensitivity, and oxygen content control during the printing process. It is prone to forming continuous brittle phases at grain boundaries, leading to performance degradation and making it difficult to meet high impact resistance requirements. Aerospace engine blades, casings, aircraft skins, and control wings often operate under extreme impact loads, such as foreign object impacts, high-speed particle impacts, or high thermal shocks, placing extremely high demands on the impact resistance of materials. The impact toughness and crack propagation resistance of traditional Ti2AlNb plates are still insufficient to fully meet these stringent requirements. Therefore, developing an efficient and stable preparation method that can significantly improve the impact resistance of Ti2AlNb alloy medium-thick plates has become a key to promoting its advanced aerospace applications. Summary of the Invention

[0005] The first objective of this invention is to provide a method for preparing medium-thick Ti2AlNb alloy plates with high impact resistance, which solves the problems of insufficient impact resistance, complex preparation process and poor microstructure uniformity of existing Ti2AlNb alloy plates.

[0006] The second objective of this invention is to provide a medium-thick plate of high-impact Ti2AlNb alloy.

[0007] The first technical solution adopted in this invention is: a method for preparing high-impact Ti2AlNb alloy medium-thick plates, which includes the following steps:

[0008] Step 1: Using NbTi master alloy, HTi, Al bean and Mo65Al master alloy as raw materials, press all raw materials into an electrode block, and prepare Ti2AlNb alloy ingot through three VAR melting methods.

[0009] Step 2: Using the free forging method, the Ti2AlNb alloy ingot obtained in Step 1 is forged by cooling down in successive heats to prepare a Ti2AlNb alloy free forging slab.

[0010] Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab, and then straightened.

[0011] Step 4: The straightened Ti2AlNb alloy medium-thick slab is subjected to two heat treatments and then machined to obtain the finished Ti2AlNb alloy medium-thick plate.

[0012] The invention is further characterized in that:

[0013] In step 1, the amount of NbTi master alloy added accounts for 70%-90% of the total mass of the raw materials, the amount of HTi added accounts for 2%-10% of the total mass of the raw materials, the amount of Al bean added accounts for 5%-15% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 0-5% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 45%-50%, with the balance being Nb and other unavoidable impurities.

[0014] In step 1, the specific process conditions for the three-stage VAR melting method are as follows:

[0015] The first VAR melting process used a melting current of 8kA-10kA and a melting voltage of 29V-31V to produce ingots with a diameter of φ260mm-φ300mm.

[0016] The melting current for the second VAR melting was 13kA-16kA, and the melting voltage was 30V-32V, resulting in ingots with a diameter of φ340mm-φ380mm.

[0017] The melting current for the third VAR melting was 9kA-11kA, and the melting voltage was 29V-31V, resulting in ingots with a diameter of φ420mm-φ460mm.

[0018] Step 2 is as follows:

[0019] First, the blank is opened in the B2 single-phase temperature range of 1090℃-1200℃ with a deformation amount of 40%-50%.

[0020] Then, intermediate forging is carried out in the temperature range of 940℃-1090℃ using a sequential cooling order, with the deformation amount of each forging controlled at 30%-40%, and the forging temperature of each forging not higher than the forging temperature of the previous forging; among them, 990℃-1090℃ is the temperature range of the B2+α2 two-phase region, and 940℃-990℃ is the temperature range of the B2+α2+O three-phase region.

[0021] Finally, the temperature range of 940℃-990℃ in the B2+α2+O three-phase region was controlled for the final forging process, and the deformation was controlled at 10%-20% to prepare a Ti2AlNb alloy free forging slab with a thickness of 80mm-200mm.

[0022] In step 2, during the preparation of Ti2AlNb alloy free forging slabs using the free forging method, the total number of forging passes is 5 to 15.

[0023] In step 3, the full-heat rolling temperature is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in step 2.

[0024] In step 3, the specific parameters of the hot rolling process are as follows: the deformation amount of the first rolling pass is 5%-10%, the deformation amount of the remaining passes is 10%-20%, the cumulative deformation amount is controlled at 30%-90%, and the total number of rolling passes is 8-15; after each 2-3 rolling passes, the slab is reheated in the furnace for 10-30 minutes.

[0025] In step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 15mm-100mm.

[0026] In step 3, the straightening process is as follows: after the final rolling process, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat; or the Ti2AlNb alloy medium-thick slab obtained from the final rolling process is reheated in the furnace to 0.6-0.7 times the rolling temperature, and the obtained Ti2AlNb alloy medium-thick slab is straightened using a high-speed forging machine.

[0027] In step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 940℃-990℃ for 0.5h-2h, followed by air cooling or wind cooling.

[0028] In step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 750℃-800℃ for 12h-24h, followed by air cooling.

[0029] The second technical solution adopted in this invention is: a high impact-resistant Ti2AlNb alloy medium-thick plate, which is prepared by the above method.

[0030] The beneficial effects of this invention are:

[0031] (1) The method of this invention uses a highly alloyed NbTi alloy to prepare a Ti2AlNb alloy with a high Nb content. It avoids using pure Nb with a high melting point as the raw material for adding Nb, effectively preventing the formation of infusible high-melting-point Nb, improving the compositional uniformity of the Ti2AlNb ingot, and enhancing the stability of the microstructure and properties of the prepared medium-thick plate. Compared with Ti2AlNb plates prepared by powder metallurgy, the plates prepared using the method of this invention have a lower oxygen content, avoiding the weakening of the plate's plasticity and impact resistance due to excessive oxygen content.

[0032] (2) The method of this invention adopts a hot working process combining free forging and rolling, and uses a gradually decreasing hot working temperature to promote the dynamic spheroidization of equiaxed O / α2 phases, providing a basis for subsequent heat treatment to control the properties of the finished medium-thick plate. First, the ingot is prepared into a free forging slab using the free forging method, and then the free forging slab is hot rolled to prepare the finished slab, which effectively improves the utilization rate of materials. The free forging process uses a high deformation per pass to quickly refine the grains, and the hot rolling process uses a small deformation per pass and uses a specified number of passes for heat preservation treatment, ensuring the uniformity of the microstructure of the finished slab.

[0033] (3) The method of the present invention employs a solution treatment and aging heat treatment process within a specified temperature range to obtain a dual-phase microstructure with specified dimensional characteristics in the finished Ti2AlNb alloy medium-thick plate. The solution treatment system proposed in the method of the present invention can effectively control the isoaxial O / α2 phase content in the Ti2AlNb alloy, giving the alloy good plasticity; the aging treatment proposed in the method of the present invention can regulate the length and width of the O phase lamellae precipitated in the B2 phase within the micrometer and submicrometer scale, giving the plate both good strength and excellent impact resistance.

[0034] (4) The alloy structure of the finished plate prepared by the method of the present invention is a dual-state structure composed of fine O phase lamellae precipitated in the equiaxed O / α2 phase and B2 phase matrix. The content of equiaxed O / α2 phase is 10%-30%, and the average length of the fine O phase lamellae is 1μm-3μm and the average width is 0.1μm-0.3μm.

[0035] (5) The finished medium-thick plate prepared by the method of the present invention maintains a high level of strength and plasticity while having high impact resistance: tensile strength ≥1000MPa, yield strength ≥850MPa, elongation after fracture ≥6% at room temperature, tensile strength ≥600MPa, yield strength ≥450MPa, elongation after fracture ≥10% at 750℃; impact energy ≥15J at room temperature, and impact energy ≥10J at -55℃. Attached Figure Description

[0036] Figure 1 shows the microstructure of the Ti2AlNb finished plate with a δ95mm specification in Example 1 of the present invention, with a scale bar of 10μm;

[0037] Figure 2 shows the microstructure of the Ti2AlNb finished plate with a δ95mm specification in Example 1 of the present invention, with a scale bar of 5μm;

[0038] Figure 3 shows the microstructure of the Ti2AlNb finished plate with a δ15mm specification in Example 2 of the present invention, with a scale bar of 10μm;

[0039] Figure 4 shows the microstructure of the Ti2AlNb finished plate with a δ15mm specification in Example 2 of the present invention, with a scale bar of 5μm.

[0040] Figure 5 shows the microstructure of the Ti2AlNb finished plate with a δ40mm specification in Example 3 of the present invention, with a scale bar of 10μm.

[0041] Figure 6 shows the microstructure of the δ40mm Ti2AlNb finished plate in Example 3 of the present invention, with a scale bar of 5μm. Detailed Implementation

[0042] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0043] This invention provides a method for preparing medium-thick plates of high-impact Ti2AlNb alloy, the method comprising the following steps:

[0044] Step 1: Using NbTi master alloy, HTi, Al bean and Mo65Al master alloy as raw materials, press all raw materials into an electrode block, and prepare a highly uniform Ti2AlNb alloy ingot through a three-stage VAR melting method.

[0045] In step 1, the amount of NbTi master alloy added accounts for 70%-90% of the total mass of the raw materials, the amount of HTi added accounts for 2%-10% of the total mass of the raw materials, the amount of Al bean added accounts for 5%-15% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 0-5% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 45%-50%, with the balance being Nb and other unavoidable impurities.

[0046] In step 1, the specific process conditions for the three-stage VAR melting method are as follows:

[0047] The first VAR melting process used a melting current of 8kA-10kA and a melting voltage of 29V-31V to produce ingots with a diameter of φ260mm-φ300mm.

[0048] The melting current for the second VAR melting was 13kA-16kA, and the melting voltage was 30V-32V, resulting in ingots with a diameter of φ340mm-φ380mm.

[0049] The melting current for the third VAR melting was 9kA-11kA, and the melting voltage was 29V-31V, resulting in ingots with a diameter of φ420mm-φ460mm.

[0050] Step 2: Using the free forging method, the Ti2AlNb alloy ingot obtained in Step 1 is forged by cooling down in successive heats to prepare a Ti2AlNb alloy free forging slab.

[0051] Step 2 is as follows:

[0052] First, the blank is opened in the B2 single-phase region temperature range of 1090℃-1200℃ with a deformation amount of 40%-50% to break up the coarse B2 grains.

[0053] Then, intermediate forging is carried out in the temperature range of 940℃-1090℃ with a cooling sequence, and the deformation of each forging is controlled at 30%-40%, and the forging temperature of each forging is not higher than the forging temperature of the previous forging, to further refine the B2 grains; among them, 990℃-1090℃ is the temperature range of the B2+α2 two-phase region, and 940℃-990℃ is the temperature range of the B2+α2+O three-phase region.

[0054] Finally, the temperature range of 940℃-990℃ in the B2+α2+O three-phase region was controlled for the final forging process, and the deformation was controlled at 10%-20% to promote the full spheroidization of the equiaxed O / α2 phase, thus preparing a Ti2AlNb alloy free forging slab with a thickness of 80mm-200mm.

[0055] In step 2, the Ti2AlNb alloy free forging slab is prepared using a forging process with gradual cooling and large deformation, with a total of 5 to 15 forging cycles.

[0056] Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab with a single rolling temperature and small deformation, and then straightened.

[0057] In step 3, the full-heat rolling temperature is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in step 2.

[0058] In step 3, the specific parameters for the hot rolling process with a single rolling temperature and small deformation are as follows: the deformation of the first rolling pass is 5%-10%, the deformation of the remaining passes is 10%-20%, the cumulative deformation is controlled at 30%-90%, and the total number of rolling passes is 8-15; after each 2-3 rolling passes, the slab is reheated in the furnace for 10-30 minutes.

[0059] In step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 15mm-100mm.

[0060] In step 3, the straightening process is as follows: after the final rolling process, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat; or the Ti2AlNb alloy medium-thick slab obtained from the final rolling process is reheated in the furnace to 0.6-0.7 times the rolling temperature, and the obtained Ti2AlNb alloy medium-thick slab is straightened using a high-speed forging machine.

[0061] Step 4: The straightened Ti2AlNb alloy medium-thick slab is subjected to a dual heat treatment process: solution treatment at the α2+B2+O three-phase region temperature and aging at the B2+O two-phase region temperature. After machining, the finished Ti2AlNb alloy medium-thick plate is obtained.

[0062] In step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 940℃-990℃ for 0.5h-2h, followed by air cooling or wind cooling.

[0063] In step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 750℃-800℃ for 12h-24h, followed by air cooling.

[0064] The present invention also provides a high impact-resistant Ti2AlNb alloy medium-thick plate, which is prepared by the above method.

[0065] Example 1

[0066] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0067] Step 1: Use NbTi alloy chips with a Ti mass fraction of 46.8% (the balance of NbTi alloy chips is Nb and other unavoidable impurities in addition to Ti), HTi and Al beads as raw materials; wherein, the mass of NbTi alloy, HTi and Al beads account for 82%, 4% and 14% of the total mass of raw materials, respectively.

[0068] After pressing NbTi alloy shavings, HTi and Al beads into an electrode block, VAR melting was performed; a highly uniform Ti2AlNb alloy ingot was prepared by three VAR melting methods.

[0069] The first VAR melting process involved a melting current of 9kA and a melting voltage of 30V, resulting in a Ti2AlNb alloy ingot with a diameter of 280mm.

[0070] The melting current for the second VAR melting was 14kA and the melting voltage was 31V, resulting in a Ti2AlNb alloy ingot with a diameter of φ360mm.

[0071] The melting current for the third VAR melting was 10kA and the melting voltage was 29V, resulting in a Ti2AlNb alloy ingot with a diameter of φ440mm.

[0072] The compositional uniformity of the φ440mm Ti2AlNb alloy ingot obtained in step 1 is shown in Table 1. Table 1 shows that the ingot exhibits good alloy element uniformity, with the Al range less than 6000ppm and the Nb range less than 4000ppm. The oxygen content is also well controlled, with all values ​​less than 300ppm. After surface finishing, the ingot is transferred to the free forging process.

[0073] Step 2: First, the Ti2AlNb alloy ingot obtained in Step 1 is forged at 1170℃ to form a blank, with a deformation of 45%. Then, the ingot is forged in an intermediate forging process with a cooling sequence of 1070℃-1090℃, 1030℃-1050℃, and 940℃-960℃, with a deformation of 35% per forging. Finally, a final forging is performed at 940℃-960℃, with a deformation of 18%, to obtain a 150mm thick Ti2AlNb alloy free forging slab. The total number of forging processes is 5. After the 150mm thick Ti2AlNb alloy free forging slab is machined, polished, and chamfered, it is transferred to the rolling process.

[0074] Step 3: The Ti2AlNb alloy free-forging slab obtained in Step 2 is rolled into a δ100mm thick Ti2AlNb alloy medium-thick slab at a rolling temperature of 940℃-960℃. The deformation amount of the first rolling pass is 5%, and the deformation amount of the remaining passes is 10%, with a total rolling deformation of 50%. The total number of rolling passes is 8, and the slab is held in the furnace for 15 minutes after every 2 passes. After rolling, the resulting δ100mm thick Ti2AlNb alloy medium-thick slab is heated to 650℃, and then straightened using a high-speed forging mill.

[0075] Step 4: The Ti2AlNb alloy medium-thick slab straightened in Step 3 was first subjected to solution treatment at 960℃ for 1 hour followed by air cooling to room temperature. Then, it was subjected to aging treatment at 770℃ for 12 hours followed by air cooling to room temperature. This resulted in a dual-state microstructure as shown in Figures 1 and 2, consisting of dark gray spherical O / α2 phases and light gray fine O phase lamellars. As can be seen from Figures 1 and 2, the content of equiaxed O / α2 phase is 30%, and the average length of the O phase lamellars is 2.5 μm and the average width is 0.10 μm.

[0076] After heat treatment, a δ100mm thick Ti2AlNb alloy medium-thick slab was mechanically processed to obtain a δ95mm thick finished plate. The plate was tested according to GB / T228.1 and GB / T229, and the performance results are shown in Table 2. The prepared Ti2AlNb plate has room low / temperature impact performance with an impact energy of over 10J, and also has excellent strength-plasticity matching at room temperature and 750℃. This successfully enables Ti2AlNb plate to have the advantages of high strength, toughness and high plasticity at the same time, and solves the problems of insufficient impact resistance, complex preparation process and poor microstructure uniformity of existing Ti2AlNb alloy plates.

[0077] Table 1. Compositional uniformity of the Ti2AlNb alloy ingots prepared in Example 1

[0078]

[0079] Table 2 Mechanical properties of Ti2AlNb finished plates with a δ95mm specification prepared in Example 1

[0080]

[0081] Example 2

[0082] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0083] Step 1: Use NbTi alloy chips with a Ti mass fraction of 47.5% (the balance of NbTi alloy chips is Nb and other unavoidable impurities in addition to Ti), HTi and Al beads as raw materials; wherein, the mass of NbTi alloy, HTi and Al beads account for 80%, 6% and 14% of the total mass of raw materials, respectively.

[0084] After pressing NbTi alloy shavings, HTi and Al beads into an electrode block, VAR melting was performed; a highly uniform Ti2AlNb alloy ingot was prepared by three VAR melting methods.

[0085] The first VAR melting process used a melting current of 8.5kA and a melting voltage of 30.5V to produce a Ti2AlNb alloy ingot with a diameter of 280mm.

[0086] The melting current for the second VAR melting was 15kA and the melting voltage was 31.5V, resulting in a Ti2AlNb alloy ingot with a diameter of φ360mm.

[0087] The melting current for the third VAR melting was 9.5kA and the melting voltage was 28.5V, resulting in a Ti2AlNb alloy ingot with a diameter of φ440mm.

[0088] The compositional uniformity of the φ440mm Ti2AlNb alloy ingot obtained in step 1 is shown in Table 3. Table 3 shows that the aluminum content range of the entire ingot is <3000ppm, the niobium content range is <3500ppm, and the oxygen content is controlled below 250ppm, indicating a high level of compositional uniformity and oxygen content control. After surface machining, the ingot is transferred to the free forging process.

[0089] Step 2: First, the Ti2AlNb alloy ingot obtained in Step 1 is forged at 1170℃ to form a blank, with a deformation of 43%. Then, the ingot is forged in an intermediate forging process with a cooling sequence of 1060℃-1080℃, 1020℃-1040℃, 970℃-990℃, and 940℃-955℃, with deformations of 38%, 35%, 36%, and 30% respectively per forging. Finally, a final forging is performed at 940℃-955℃, with a deformation of 14%, to obtain a Ti2AlNb alloy free forging slab with a thickness of 80mm. The total number of forging processes is 10. After machining and chamfering, the 80mm thick Ti2AlNb alloy free forging slab is transferred to the rolling process.

[0090] Step 3: The Ti2AlNb alloy free forging slab obtained in Step 2 is rolled at a rolling temperature of 940℃-955℃. The deformation amount of the first pass is 6%, and the deformation amount of the remaining passes is 10%. The slab is returned to the furnace for 15 minutes after every two passes. The cumulative deformation amount of rolling is 78%, and the total number of rolling passes is 13. A Ti2AlNb alloy medium-thick slab with a thickness of δ18mm is prepared. After the final rolling pass is completed, the slab is immediately straightened by a multi-roll straightener at residual temperature.

[0091] Step 4: The Ti2AlNb alloy medium-thick slab straightened in Step 3 was first solution-treated by holding at 950℃ for 1.5h and then air-cooled to room temperature. Then, it was aged by holding at 770℃ for 18h and then air-cooled to room temperature, resulting in a bimodal microstructure as shown in Figures 3-4, consisting of dark gray spherical O / α2 phases and light gray O phase lamellars. The equiaxed O / α2 phase content was 10%, and the average length and width of the O phase lamellars were 1.0 μm and 0.18 μm, respectively. After machining, a 15 mm thick finished plate was obtained. The plate was tested according to GB / T 228.1 and GB / T 229, and the performance results are shown in Table 4. Under the condition that the room temperature plasticity of the alloy reached more than 15%, the room temperature impact energy of the alloy reached more than 20 J, achieving a good match between plasticity and impact resistance.

[0092] Table 3. Compositional uniformity of the Ti2AlNb alloy ingots prepared in Example 2

[0093]

[0094] Table 4 Mechanical properties of Ti2AlNb finished plates with a δ15mm specification prepared in Example 2

[0095]

[0096] Example 3

[0097] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0098] Step 1: Use NbTi alloy chips with a Ti mass fraction of 48.2% (the balance of NbTi alloy chips is Nb and other unavoidable impurities in addition to Ti), HTi, Al chips and Mo65Al master alloy as raw materials; wherein the mass of NbTi alloy, Al chips and Mo65Al master alloy account for 78%, 8.5% and 13.2% and 0.5% of the total mass of raw materials, respectively.

[0099] After pressing NbTi alloy shavings, HTi, Al beads and Mo65Al master alloy into an electrode block, VAR melting was performed.

[0100] Highly uniform Ti2AlNb alloy ingots were prepared by a three-stage VAR melting method.

[0101] The first VAR melting process used a melting current of 8.5kA and a melting voltage of 29.5V to produce a Ti2AlNb alloy ingot with a diameter of 280mm.

[0102] The melting current for the second VAR melting was 14.5kA and the melting voltage was 31.2V, resulting in a Ti2AlNb alloy ingot with a diameter of 360mm.

[0103] The melting current for the third VAR melting was 10.5kA and the melting voltage was 29.8V, resulting in a Ti2AlNb alloy ingot with a diameter of φ440mm.

[0104] After smelting, the obtained Ti2AlNb alloy ingot was machined to remove surface defects. Its chemical composition, analyzed by multiple sampling points, is shown in Table 5. The results show that the range of aluminum, niobium, and molybdenum in the Ti2AlNb ingot is <2000 ppm, and the oxygen content is below 300 ppm. The main alloying elements are uniformly distributed, and the oxygen content is well controlled. After machining, the ingot is transferred to the free forging process.

[0105] Step 2: First, the Ti2AlNb alloy ingot obtained in Step 1 is forged at 1160℃ in the B2 single-phase region, with a deformation of 48%. Then, the first intermediate forging is performed at 1080℃ in the B2+α2 two-phase region, with a deformation of 38%; the second intermediate forging is performed at 980℃ in the B2+α2+O three-phase region, with a deformation of 35%; the final forging is performed at 960℃ in the B2+α2+O three-phase region, with a deformation of 15%, promoting dynamic spheroidization of the O / α2 phase. A total of 5 forging operations are performed. After final forging, a 150mm thick Ti2AlNb alloy free-forged slab is obtained. The 150mm thick Ti2AlNb alloy free-forged slab is then machined and chamfered before rolling.

[0106] Step 3: The Ti2AlNb alloy free-forged slab obtained in Step 2 is rolled at a rolling temperature of 955℃-965℃, with an 8% deformation in the first pass and 15% deformation in the subsequent passes, for a total cumulative deformation of 70%. A total of 8 rolling passes are performed, rolling the slab from 150mm to 45mm thickness. After every 3 rolling passes, the slab is reheated in the furnace for 20 minutes. After final rolling, the slab is immediately straightened using a multi-roll straightener, utilizing its residual heat (approximately 600℃).

[0107] Step 4: The Ti2AlNb alloy medium-thick slab straightened in Step 3 was first solution-treated by holding at 975℃ for 1.5h and then air-cooled to room temperature. Then, it was aged by holding at 780℃ for 20h and then air-cooled to room temperature, resulting in a bimodal microstructure as shown in Figures 5-6, consisting of dark gray spherical O / α2 phases and light gray O phase lamellars. The equiaxed O / α2 phase content was 21%, and the average length and width of the O phase lamellars were 3.0 μm and 0.3 μm, respectively. The mechanical properties of the δ40mm finished slab obtained after machining are shown in Table 6. The slab exhibited a room temperature strength exceeding 1000 MPa and a room temperature plasticity exceeding 9%. Simultaneously, it achieved a room temperature and low temperature impact energy exceeding 13 J, demonstrating excellent strength, plasticity, and toughness matching.

[0108] Table 5. Compositional uniformity of the Ti2AlNb alloy ingots prepared in Example 3

[0109]

[0110] Table 6 Mechanical properties of Ti2AlNb finished plates with a δ40mm specification prepared in Example 3

[0111]

[0112] Example 4

[0113] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0114] Step 1: Using NbTi master alloy, HTi, Al bean and Mo65Al master alloy as raw materials, press all raw materials into an electrode block, and prepare a highly uniform Ti2AlNb alloy ingot through a three-stage VAR melting method.

[0115] In step 1, the amount of NbTi master alloy added accounts for 70% of the total mass of the raw materials, the amount of HTi added accounts for 10% of the total mass of the raw materials, the amount of Al bean added accounts for 15% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 5% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 50%, with the balance being Nb and other unavoidable impurities.

[0116] In step 1, the specific process conditions for the three-stage VAR melting method are as follows:

[0117] The first VAR melting process used a melting current of 8kA and a melting voltage of 29V to produce an ingot with a diameter of φ260mm.

[0118] The melting current for the second VAR melting was 13kA, and the melting voltage was 30V, resulting in a φ340mm ingot.

[0119] The melting current for the third VAR melting was 9kA, and the melting voltage was 29V, resulting in an ingot with a diameter of φ420mm.

[0120] Step 2: Using the free forging method, the Ti2AlNb alloy ingot obtained in Step 1 is forged by cooling down in successive heats to prepare a Ti2AlNb alloy free forging slab.

[0121] Step 2 is as follows:

[0122] First, the blank is opened at a temperature range of 1090℃ in the single-phase region of B2 with a deformation of 40% to break up the coarse B2 grains.

[0123] Then, the ingot is subjected to intermediate forging in the order of cooling down to 1070℃-1090℃, 1030℃-1050℃, and 940℃-960℃, with the deformation amount of each forging controlled at 30%, to further refine the B2 grains.

[0124] Finally, the final forging was carried out in the temperature range of 940℃-960℃ in the B2+α2+O three-phase region, with the deformation controlled at 10%, to promote the full spheroidization of the equiaxed O / α2 phase and prepare a Ti2AlNb alloy free forging slab with a thickness of 80mm.

[0125] In step 2, the Ti2AlNb alloy free forging slab is prepared using a forging process with large deformation and gradual cooling, with a total of 5 forging cycles.

[0126] Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab with a single rolling temperature and small deformation, and then straightened.

[0127] In step 3, the full-heat rolling temperature is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in step 2.

[0128] In step 3, the specific parameters for the hot rolling process with a single rolling temperature and small deformation are as follows: the deformation of the first rolling pass is 5%, the deformation of the remaining passes is 10%, the cumulative deformation is controlled at 30%, and the total number of rolling passes is 8; after each 2 rolling passes, the slab is reheated in the furnace for 10 minutes.

[0129] In step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 15mm.

[0130] In step 3, the straightening process is as follows: after the final rolling process is completed, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat.

[0131] Step 4: The straightened Ti2AlNb alloy medium-thick slab is subjected to a dual heat treatment process: solution treatment at the α2+B2+O three-phase region temperature and aging at the B2+O two-phase region temperature. After machining, the finished Ti2AlNb alloy medium-thick plate is obtained.

[0132] In step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 940℃ for 0.5h, followed by air cooling or wind cooling.

[0133] In step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 750℃ for 12 hours, followed by air cooling.

[0134] Example 5

[0135] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0136] Step 1: Using NbTi master alloy, HTi, Al bean and Mo65Al master alloy as raw materials, press all raw materials into an electrode block, and prepare a highly uniform Ti2AlNb alloy ingot through a three-stage VAR melting method.

[0137] In step 1, the amount of NbTi master alloy added accounts for 90% of the total mass of the raw materials, the amount of HTi added accounts for 2% of the total mass of the raw materials, the amount of Al bean added accounts for 5% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 3% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 45%, with the balance being Nb and other unavoidable impurities.

[0138] In step 1, the specific process conditions for the three-stage VAR melting method are as follows:

[0139] The first VAR melting process used a melting current of 9kA and a melting voltage of 30V to produce an ingot with a diameter of 280mm.

[0140] The melting current for the second VAR melting was 15kA, and the melting voltage was 31V, resulting in a φ360mm ingot.

[0141] The melting current for the third VAR melting was 10kA and the melting voltage was 30V, resulting in an ingot with a diameter of φ440mm.

[0142] Step 2: Using the free forging method, the Ti2AlNb alloy ingot obtained in Step 1 is forged by cooling down in successive heats to prepare a Ti2AlNb alloy free forging slab.

[0143] Step 2 is as follows:

[0144] First, the blank is opened at a temperature range of 1100℃ in the single-phase region of B2 with a deformation of 45% to break up the coarse B2 grains.

[0145] Then, the ingot is subjected to intermediate forging in the order of cooling down at 1080℃-1090℃, 1030℃-1050℃, and 940℃-970℃. The deformation of each forging is controlled at 35%, and the forging temperature of each forging is not higher than the forging temperature of the previous forging, so as to further refine the B2 grains.

[0146] Finally, the temperature was controlled within the B2+α2+O three-phase region of 940℃-970℃ for final forging, with the deformation controlled at 15%, to promote the full spheroidization of the equiaxed O / α2 phase and prepare a Ti2AlNb alloy free forging slab with a thickness of 100mm.

[0147] In step 2, the Ti2AlNb alloy free forging slab is prepared using a forging process with large deformation and gradual cooling, with a total of 10 forging cycles.

[0148] Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab with a single rolling temperature and small deformation, and then straightened.

[0149] In step 3, the full-heat rolling temperature is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in step 2.

[0150] In step 3, the specific parameters for the hot rolling process with a single rolling temperature and small deformation are as follows: the deformation of the first rolling pass is 6%, the deformation of the remaining passes is 15%, the cumulative deformation is controlled at 50%, and the total number of rolling passes is 9; after each 3 rolling passes, the slab is reheated in the furnace for 20 minutes.

[0151] In step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 50 mm.

[0152] In step 3, the straightening process is as follows: after the final rolling process is completed, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat.

[0153] Step 4: The straightened Ti2AlNb alloy medium-thick slab is subjected to a dual heat treatment process: solution treatment at the α2+B2+O three-phase region temperature and aging at the B2+O two-phase region temperature. After machining, the finished Ti2AlNb alloy medium-thick plate is obtained.

[0154] In step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 960℃ for 1 hour, followed by air cooling or wind cooling.

[0155] In step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 780℃ for 20 hours, followed by air cooling.

[0156] Example 6

[0157] A method for preparing high-impact-resistant Ti2AlNb alloy medium-thick plates, comprising the following steps:

[0158] Step 1: Using NbTi master alloy, HTi, Al bean and Mo65Al master alloy as raw materials, press all raw materials into an electrode block, and prepare a highly uniform Ti2AlNb alloy ingot through a three-stage VAR melting method.

[0159] In step 1, the amount of NbTi master alloy added accounts for 90% of the total mass of the raw materials, the amount of HTi added accounts for 2% of the total mass of the raw materials, the amount of Al bean added accounts for 5% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 3% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 45%, with the balance being Nb and other unavoidable impurities.

[0160] In step 1, the specific process conditions for the three-stage VAR melting method are as follows:

[0161] The first VAR melting process used a melting current of 10kA and a melting voltage of 31V to produce an ingot with a diameter of φ300mm.

[0162] The melting current for the second VAR melting was 16kA, and the melting voltage was 32V, resulting in a φ380mm ingot.

[0163] The melting current for the third VAR melting was 11kA and the melting voltage was 31V, resulting in an ingot with a diameter of φ460mm.

[0164] Step 2: Using the free forging method, the Ti2AlNb alloy ingot obtained in Step 1 is forged by cooling down in successive heats to prepare a Ti2AlNb alloy free forging slab.

[0165] Step 2 is as follows:

[0166] First, the blank is opened in the B2 single-phase temperature range of 1200℃ with a deformation amount of 50%.

[0167] Then, the ingot is subjected to intermediate forging in the order of cooling down to 1070℃-1090℃, 1030℃-1040℃, and 960℃-990℃. The deformation of each forging is controlled at 40%, and the forging temperature of each forging is not higher than the forging temperature of the previous forging.

[0168] Finally, the temperature range of 960℃-990℃ in the B2+α2+O three-phase region is controlled for the final forging process, and the deformation is controlled at 10%-20% to promote the full spheroidization of the equiaxed O / α2 phase, so as to prepare a Ti2AlNb alloy free forging slab with a thickness of 80mm-200mm.

[0169] In step 2, the Ti2AlNb alloy free forging slab is prepared using a forging process with large deformation and gradual cooling, with a total of 15 forging cycles.

[0170] Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab with a single rolling temperature and small deformation, and then straightened.

[0171] In step 3, the full-heat rolling temperature is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in step 2.

[0172] In step 3, the specific parameters for the hot rolling process with a single rolling temperature and small deformation are as follows: the deformation amount of the first rolling pass is 10%, the deformation amount of the remaining passes is 20%, the cumulative deformation amount is controlled at 90%, and the total number of rolling passes is 15; after each 3 rolling passes, the slab is reheated in the furnace for 30 minutes.

[0173] In step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 100 mm.

[0174] In step 3, the straightening process is as follows: after the final rolling process is completed, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat.

[0175] Step 4: The straightened Ti2AlNb alloy medium-thick slab is subjected to a dual heat treatment process: solution treatment at the α2+B2+O three-phase region temperature and aging at the B2+O two-phase region temperature. After machining, the finished Ti2AlNb alloy medium-thick plate is obtained.

[0176] In step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 990℃ for 2 hours, followed by air cooling or wind cooling.

[0177] In step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 800℃ for 24 hours, followed by air cooling.

Claims

1. A method for preparing high-impact Ti2AlNb alloy medium-thick plates, characterized in that, The method includes the following steps: Step 1: Using NbTi master alloy, HTi, Al alloy, and Mo65Al master alloy as raw materials, all raw materials are pressed into an electrode block, and Ti2AlNb alloy ingots are prepared by three-stage VAR melting method; Step 2: The Ti2AlNb alloy ingot obtained in Step 1 is forged by sequential cooling using a free forging method to prepare Ti2AlNb alloy free forging slabs; Step 2 specifically involves: firstly, blanking is performed in the B2 single-phase temperature range of 1090℃-1200℃ with a deformation of 40%-50%; then, the blanking is performed at a temperature of 940℃-1090℃. The intermediate forging process employs a sequential cooling phase, with each forging cycle controlling the deformation at 30%-40%, and the forging temperature of each cycle not exceeding that of the previous cycle. Specifically, 990℃-1090℃ represents the B2+α2 two-phase region, and 940℃-990℃ represents the B2+α2+O three-phase region. Finally, a final forging cycle is performed within the B2+α2+O three-phase region (940℃-990℃), with the deformation controlled at 10%-20%, yielding a Ti2AlNb alloy free-forged slab with a thickness of 80mm-200mm. In step 2, the free forging method is used. In the process of preparing Ti2AlNb alloy free forging slabs, the total number of forging passes is 5-15. Step 3: Using hot rolling, the Ti2AlNb alloy free forging slab is rolled into a Ti2AlNb alloy medium-thick slab, and then straightened. In Step 3, the rolling temperature for all passes is consistent with the final forging temperature used for the Ti2AlNb alloy free forging slab in Step 2. The specific parameters of the hot rolling process in Step 3 are: the deformation amount of the first rolling pass is 5%-10%, the deformation amount of the remaining passes is 10%-20%, the cumulative deformation amount is controlled at 30%-90%, and the total number of rolling passes is 8-15. Every 2-3 passes... After rolling, the slab is reheated in the furnace for 10-30 minutes; in step 3, the thickness of the obtained Ti2AlNb alloy medium-thick slab is 15mm-100mm; in step 4, the straightened Ti2AlNb alloy medium-thick slab undergoes two heat treatments, and after machining, the finished Ti2AlNb alloy medium-thick plate is obtained; in step 4, the solution heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 940℃-990℃ for 0.5h-2h, followed by air cooling or wind cooling; in step 4, the aging heat treatment conditions for the Ti2AlNb alloy medium-thick slab are: heating at 750℃-800℃ for 12h-24h, followed by air cooling.

2. The method for preparing high impact-resistant Ti2AlNb alloy medium-thick plates according to claim 1, characterized in that, In step 1, the amount of NbTi master alloy added accounts for 70%-90% of the total mass of the raw materials, the amount of HTi added accounts for 2%-10% of the total mass of the raw materials, the amount of Al bean added accounts for 5%-15% of the total mass of the raw materials, and the amount of Mo65Al master alloy added accounts for 0-5% of the total mass of the raw materials. The NbTi master alloy includes the following components by mass percentage: Ti: 45%-50%, with the balance being Nb and other unavoidable impurities.

3. The method for preparing high impact-resistant Ti2AlNb alloy medium-thick plates according to claim 1, characterized in that, In step 1, the specific process conditions for the three-stage VAR melting method are as follows: The melting current for the first VAR melting is 8kA-10kA, and the melting voltage is 29V-31V, producing ingots with a diameter of φ260mm-φ300mm; the melting current for the second VAR melting is 13kA-16kA, and the melting voltage is 30V-32V, producing ingots with a diameter of φ340mm-φ380mm; the melting current for the third VAR melting is 9kA-11kA, and the melting voltage is 29V-31V, producing ingots with a diameter of φ420mm-φ460mm.

4. The method for preparing high impact-resistant Ti2AlNb alloy medium-thick plates according to claim 1, characterized in that, In step 3, the straightening process is as follows: after the final rolling process, the Ti2AlNb alloy medium-thick slab obtained from the final rolling is straightened using a multi-roll straightener with residual heat; or the Ti2AlNb alloy medium-thick slab obtained from the final rolling process is reheated in the furnace to 0.6-0.7 times the rolling temperature, and the obtained Ti2AlNb alloy medium-thick slab is straightened using a high-speed forging machine.

5. A high-impact Ti2AlNb alloy medium-thick plate, characterized in that, It is prepared by the method described in any one of claims 1-4.

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