A titanium alloy resistant to 700 °C high temperature for aero-engines and its preparation method

Abstract

The present invention relates to the technical field of titanium alloy processing, and particularly to a high-temperature titanium alloy resistant to 700 °C for aero-engines and a preparation method thereof. By weight percentage, the raw materials for preparing the high-temperature titanium alloy include: Al: 5.5 - 7.0%, Sn: 3.0 - 5.0%, Hf: 2.0 - 4.5%, Mo: 0.0 - 1.0%, Si: 0.5 - 0.7%, Nb: 0.2% - 0.5%, Ta: 3.5% - 4.5%, W: 0.6 - 1.2%, C: 0.04 - 0.08%, O ≤ 0.15%, Fe ≤ 0.015%, and the balance is Ti. The method of the present invention designs a traditional solution aging-strengthened high-temperature titanium alloy, which is different from metal intermetallic compounds such as TiB grain boundary-strengthened high-temperature titanium alloy, TiAl-based, and Ti2AlNb-based. The final microstructure state is a duplex structure, and the service temperature range of the traditional solution aging-strengthened high-temperature titanium alloy is raised to 700 °C, and it can be used as a high-temperature component of an aero-engine under the long-term working conditions of 650 - 700 °C.

Description

Technical Field

[0001] The present invention relates to the technical field of titanium alloy processing, and particularly to a high-temperature titanium alloy resistant to 700 °C for aeroengines and a preparation method thereof. Background Art

[0002] Advanced aeroengines are continuously developing towards "three highs", namely high turbine inlet temperature, high thrust-to-weight ratio, and high pressure ratio. The requirements of the "three highs" are mainly achieved by increasing the working stress of components, reducing the weight of components, and increasing the stiffness. Although compared with other commonly used materials, high-temperature titanium alloys have significant advantages in specific strength, specific stiffness, and specific fatigue strength, and are the best choice for compressor weight reduction. However, the new generation of advanced aeroengines has a development trend of reducing the number of compressor disk stages, increasing the rotational speed, advancing the high-temperature section, and integrating the structure, resulting in a decreasing demand for low heat-resistant temperature titanium alloys. There is a general trend for titanium alloys to develop towards higher temperatures and even replace some nickel-based superalloys. At present, the maximum service temperature of traditional solution aging strengthened high-temperature titanium alloys is 600 - 650 °C, which can no longer meet the service requirements of the rear section of the compressor of the new generation of aeroengines.

[0003] There are various criteria for the design of titanium alloy materials. For example, aircraft structural materials need to be designed according to the damage tolerance criterion, some non-rotating engine components need to be designed according to the strength design criterion, and engine rotating components with a service temperature of 600 - 700 °C need to be designed according to the creep and fatigue strength criteria.

[0004] Chinese Patent CN104018027B "A Heat-Resistant Titanium Alloy and Its Processing, Manufacturing Method and Application" designed a high-temperature titanium alloy composition that can be used at 600 - 650 °C for a long time. Through different processing and heat treatment combinations, different matches of tensile strength and plasticity, creep and heat stability can be obtained, and it can be used to manufacture parts such as blades and disks of high-temperature components of advanced aeroengines; it can also be used for a short time on temperature-resistant structural components such as the skin of aerospace vehicles at 700 °C; it can also be used as materials for high-temperature and corrosion-resistant valves in automobiles and boilers. Only the high-temperature tensile properties and creep properties at 700 °C (fracture at 450 MPa for 0.3 h) were partially tested, and the creep and fatigue properties at 700 °C were not involved, which cannot meet the requirements for long-term use at 700 °C.

[0005] Therefore, in order to meet the requirements of the new generation of advanced aeroengines for titanium alloys, it is urgent to design a new high-temperature titanium alloy for long-term use at 700 °C according to the high creep and fatigue performance criteria. Based on the creep residual strain as the evaluation basis, it is 20% higher than the existing high-temperature titanium alloy resistant to 650 °C, and the fatigue life is 20% higher than the existing high-temperature titanium alloy resistant to 650 °C under the same experimental conditions. Summary of the Invention

[0006] The first aspect of the present invention provides a high-temperature titanium alloy resistant to 700 °C for aeroengines. By weight percentage, the raw materials for preparing the high-temperature titanium alloy include: Al: 5.5 - 7.0%, Sn: 3.0 - 5.0%, Hf: 2.0 - 4.5%, Mo: 0.0 - 1.0%, Si: 0.5 - 0.7%, Nb: 0.2% - 0.5%, Ta: 3.5% - 4.5%, W: 0.6 - 1.2%, C: 0.04 - 0.08%, and the balance is Ti and impurities.

[0007] Further, the impurities include inevitable O and Fe. In the present invention, O ≤ 0.15% and Fe ≤ 0.015%.

[0008] In some embodiments, the rotating bending fatigue limit of the high-temperature titanium alloy at 700 °C is 300 - 320 MPa, the creep stress at 700 °C is 70 MPa, and the residual strain under the test condition of 100 h is ≤ 0.2%.

[0009] The second aspect of the present invention provides a preparation method of a high-temperature titanium alloy resistant to 700 °C for aeroengines. The preparation method includes the following steps:

[0010] S1. Prepare Ti-Hf master alloy: Mix the first sponge titanium and sponge hafnium evenly and place them at the bottom of the melting crucible. Start the electron beam melting furnace to melt the alloy materials in the crucible, and cool to obtain a Ti-Hf master alloy ingot. Finally, clean, crush, and screen the alloy ingot to obtain granular Ti-Hf master alloy;

[0011] S2. Ingot melting: Add the intermediate alloys of Ti-Sn, Ti-Hf, Al-Mo, Al-Si, Al-Nb, Al-Ta, Al-W, pure aluminum, and carbon powder to granular second sponge titanium, press the electrode, and use the welded electrode block for vacuum consumable melting. After vacuum consumable melting, an alloy ingot is obtained; the Ti-Hf is the granular Ti-Hf master alloy prepared in S1;

[0012] S3. Homogenization heat treatment and cogging forging of the ingot: Perform homogenization heat treatment on the alloy ingot in S2; preheat the ingot after homogenization heat treatment and then perform cogging forging. After forging deformation, air cooling is used for all, and finally a billet after cogging in the β phase region is obtained;

[0013] S4. Preparation of bar blanks or die forging blanks: The blanks in S3 are subjected to deformation in three stages in sequence. In the first stage of deformation, the blanks are heated to a temperature 100 - 20 °C below the β phase transition point, held for heat preservation, and then subjected to deformation for 1 - 3 heats, and are air-cooled after deformation; in the second stage of deformation, the blanks are heated to a temperature 20 - 40 °C above the β phase transition point, held for heat preservation, and then subjected to deformation for 1 - 2 heats. After the last heat of deformation in the second stage, they are water-cooled, and are air-cooled after deformation in the heats before the last heat; in the third stage of deformation, the blanks are heated to a temperature 100 - 20 °C below the β phase transition point, held for heat preservation, and then subjected to deformation for 3 - 8 heats, and are air-cooled after deformation, finally obtaining bar blanks or die forging blanks;

[0014] S5. Heat treatment of bar blanks or die forging blanks: The bar blanks or die forging blanks in S4 are subjected to solution and aging heat treatment to obtain the high-temperature titanium alloy.

[0015] In some embodiments, the particle sizes of the first titanium sponge and the second titanium sponge are both 2 - 12.7 mm, and the particle size of hafnium sponge is 2 - 25.4 mm.

[0016] In the steps of ingot melting, alloy packages are distributed and arranged to press the electrodes, and alloy ingots are prepared by combining multiple vacuum consumable melts. The alloying elements Sn, Hf, Mo, Si, Nb, Ta, and W are all added in the form of master alloys. Part of Al is brought in by the master alloy, and the insufficient part is added with high-purity Al beans and Al foils. Ti is added in the form of titanium sponge, Ti - Sn and Ti - Hf master alloys respectively, and C is added in the form of carbon powder. The electrode blocks are welded and then used for vacuum consumable melting. After vacuum consumable melting the alloy ingots 3 - 4 times, alloy ingots are obtained. The high-temperature titanium alloy designed by the present invention can be used at 700 °C for a long time. Through tests and research, higher mass fractions of Hf, Ta, and Si are added to this alloy. The high-temperature creep and fatigue properties of this alloy are improved by using the high oxidation resistance of the Hf element, the strengthening effect of the Ta element, and the precipitation of fine and dispersed silicides; the upper and lower limits of the C element are precisely controlled, which can not only avoid the reduction of alloy plasticity caused by high C content, but also precisely control the content of equiaxed primary α phase during the subsequent heat treatment process, and obtain the volume fraction of equiaxed primary α phase under the target ideal microstructure; the impurity element Fe is precisely controlled to improve the creep performance of the alloy.

[0017] Further, the master alloy containing Hf in S1 is prepared by an electron beam melting furnace. The raw materials are titanium sponge with a particle size of 2 - 12.7 mm and hafnium sponge with a particle size of 2 - 25.4 mm. 50% by weight of titanium sponge and hafnium are mixed evenly and placed at the bottom of the melting crucible. The electron beam melting furnace is started to increase the current to 500 - 1500 A to melt the alloy materials in the crucible, and the Ti - Hf master alloy ingot is obtained after cooling. Finally, the alloy ingot is cleaned, crushed, and screened to obtain granular Ti - Hf master alloy.

[0018] By retrieving the national and industrial standards for hafnium-containing raw materials in China (YS / T 399-2013 Hafnium Sponge, GB / T 38524-2020 Hafnium Rods and Hafnium Wires), it can be seen that only metallic hafnium and hafnium sponge can be purchased in the domestic market. It is known that vacuum consumable melting process is used in titanium alloy melting. In the conventional melting process, it is difficult for the molten pool temperature to exceed the alloy melting temperature of Hf element by 150-300 °C (it is known that the melting point of Hf element is as high as 2233 °C). And through the experiments of the present invention, it is verified that adding in the form of hafnium sponge and fine chip-shaped metallic hafnium will cause Hf inclusions in the ingot, seriously affecting the compositional uniformity of the ingot and the mechanical properties of the subsequent finished parts. In addition, significantly increasing the molten pool temperature will cause a large amount of low-melting-point elements (Al, Sn) in the alloy to volatilize, failing to reach the designed target composition, resulting in a reduction in the comprehensive mechanical properties of the subsequent finished parts. Therefore, considering other added alloy elements comprehensively in the present invention, preferably, first prepare Ti-Hf master alloy by electron beam melting furnace, and then introduce Hf element in the form of granular Ti-Hf master alloy. The master alloy can significantly reduce defects such as segregation and inclusion of refractory elements, and effectively improve the uniformity and stability of the alloy composition.

[0019] Furthermore, the Si-containing master alloy described in S2 selects Al-Si master alloy, and the mass fraction of Si in the master alloy ≥ 15%. The Ta-containing master alloy described in S2 selects Al-Ta master alloy, and the mass fraction of Ta in the master alloy ≥ 60%. The W-containing master alloy described in S2 selects Al-W master alloy, and the mass fraction of W in the master alloy ≥ 50%.

[0020] In some embodiments, the steps of homogenization heat treatment described in S3 include: preheating the alloy ingot in S2 to 900-1000 °C for heat preservation, then heating up to 1150-1200 °C and keeping it for 12-24 h.

[0021] In some embodiments, the steps of cogging forging described in S3 include: heating the ingot to 30-200 °C above the β phase transformation point for heat preservation and then performing cogging forging for 2-4 heats.

[0022] In some embodiments, the upsetting and drawing ratios of the first, second, and third stage deformations in S4 are both 30-70%.

[0023] In some embodiments, before the last heat of the third deformation in S4, the previous deformation is 1 upsetting and drawing, and the upsetting and drawing ratios are 30-50%. The last heat is upsetting and drawing, or the last heat is die forging forming, and the deformation ratio is 30-70%.

[0024] In some embodiments, the strain rate of die forging forming of the die forging blank in S4 is 0.01-0.1 s -1 .

[0025] Furthermore, the upsetting and drawing deformations described in S2 and S3 are carried out on a quick forging machine or a hydraulic press, and the die forging forming described in S3 is carried out on a hydraulic press.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] 1. The method of the present invention designs a traditional solution aging strengthened high-temperature titanium alloy, which is different from intermetallic compounds such as TiB grain boundary strengthened high-temperature titanium alloy, TiAl-based, and Ti2AlNb-based. The final microstructure state is a duplex structure, and the service temperature range of the traditional solution aging strengthened high-temperature titanium alloy is raised to 700°C, which can be used as high-temperature components of aeroengines under long-term working conditions at 650 - 700°C.

[0028] 2. The alloy composition designed by the present invention contains a variety of high melting point refractory elements. The ingot alloy composition obtained by optimizing the addition method of master alloy is uniform and stable, and there are no defects such as segregation and inclusion of refractory alloy elements.

[0029] 3. The bars and forgings prepared by the method of the present invention have good matching of strength and plasticity at room temperature and high temperature (tensile strength at room temperature ≥ 1050 MPa, yield strength at room temperature ≥ 950 MPa, tensile strength at 700°C ≥ 580 MPa, yield strength at room temperature ≥ 450 MPa).

[0030] 4. The bars and forgings prepared by the method of the present invention have excellent high-temperature creep performance and high-temperature fatigue performance. Based on the creep residual strain as the evaluation basis, this alloy is improved by 20% compared with the existing 650°C high-temperature titanium alloy (under the test conditions of 650°C, creep stress 120 MPa, 100 h, the residual strain ≤ 0.2%; under the test conditions of 700°C, creep stress 70 MPa, 100 h, the residual strain ≤ 0.2%); the fatigue life is improved by 20% compared with the existing 650°C high-temperature titanium alloy under the same experimental conditions (650°C, 1×10 7 rotating bending fatigue limit ≥ 380 MPa, 700°C, 1×10 7 rotating bending fatigue limit ≥ 290 MPa). BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is the microstructural diagram of a 150 mm diameter bar blank in Example 1.

[0032] Figure 2 It is the microstructural diagram of a forging blank with a diameter of 220 mm and a thickness of 85 mm in Example 2.

[0033] Figure 3 It is the microstructural diagram of a 250 mm diameter bar blank in Example 3.

[0034] Figure 4It is the macrostructure diagram of the 150mm diameter bar in Comparative Example 1. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Example 1

[0037] A titanium alloy resistant to 700°C high temperature for aero-engines. By weight percentage, the raw materials for preparing the high-temperature titanium alloy include: Al: 5.9%, Sn: 3.9%, Hf: 2.5%, Mo: 0.3%, Si: 0.55%, Nb: 0.4%, Ta: 3.5%, W: 0.8%, C: 0.055%, impurities are O: 0.09% and Fe: 0.01%, and the balance is Ti. The measured β phase transformation point is 1048°C.

[0038] A preparation method of a titanium alloy resistant to 700°C high temperature for aero-engines, and the preparation method includes the following steps:

[0039] S1. Prepare Ti-Hf master alloy: The raw materials are the first sponge titanium with a particle size of 2 - 12.7mm (market sales company is Chaoyang Jinda Titanium Industry Co., Ltd.) and sponge hafnium with a particle size of 2 - 25.4mm (market sales company is Beijing Jinboyu Metal Technology Co., Ltd.). Mix 50% by weight of the first sponge titanium and sponge hafnium evenly and place them at the bottom of the melting crucible. Start the electron beam melting furnace to increase the current to 1200A to melt the alloy materials in the crucible, cool to obtain a Ti-Hf master alloy ingot, and finally clean, crush, and screen the alloy ingot to obtain granular Ti-Hf master alloy.

[0040] S2. Ingot melting: Add 2540g of Ti-Sn (Sn content 79%), 2600g of Ti-Hf (Hf content 50%), 245g of Al-Mo (Mo content 64%), 1900g of Al-Si (Si content 15%), 290g of Al-Nb (Nb content 73%), 2600g of Al-Ta (Ta content 70%), 840g of Al-W (W content 50%) master alloy, 70g of Al foil, and 25.2g of carbon powder to 42.2kg of granular second sponge titanium, press the electrode, and use the welded electrode block for vacuum consumable melting. Obtain an alloy ingot by using 3 times of vacuum consumable melting. The ingot has a diameter of 200mm and a weight of 53kg.

[0041] S3. Preheat the ingot in S2 to 950 °C and hold for 60 min, then raise the temperature to 1200 °C and hold for 12 h for homogenization heat treatment; subject the ingot after homogenization heat treatment to cogging forging in two heats. For the first heat, first preheat to 950 °C and hold for 60 min, then heat to 1180 °C and hold for 120 min. For the second heat, first preheat to 950 °C and hold for 60 min, then heat to 1100 °C and hold for 120 min. The deformation in each heat is one upsetting and drawing, and the deformation amounts of upsetting and drawing are 45%. After forging deformation, air cooling is carried out for all, and finally a billet after cogging in the β phase region is obtained.

[0042] S4. First, subject the billet in S3 to one heat of deformation in the first stage, heat to 1020 °C and hold for 120 min, the deformation is one upsetting and drawing, and the deformation amounts of upsetting and drawing are 40%. After deformation, air cooling is carried out; then subject it to one heat of deformation in the second stage, heat to 1080 °C and hold for 120 min, the deformation is one upsetting and drawing, and the deformation amounts of upsetting and drawing are 50%. After deformation, water cooling is carried out; finally, subject it to five heats of deformation in the third stage. The heating temperatures of the five heats are 1020 °C, 1020 °C, 1010 °C, 1000 °C, and 990 °C respectively, and the holding time is 120 min for all. Before the last heat, the deformation is one upsetting and drawing, and the deformation amounts of upsetting and drawing are 40%. The last heat is one upsetting and drawing, and the deformation amount is 30%. After deformation, air cooling is carried out for all. Finally, a 150 mm diameter bar billet is obtained.

[0043] S5. Cut 50 mm in the length direction of the bar billet in S4 for solution and aging heat treatment. Solution treatment: 1030 °C, hold for 2 h, oil cooling. Aging treatment: 710 °C, hold for 5 h, air cooling.

[0044] For the 150 mm diameter bar billet prepared by the above method, the microstructure is as Figure 1 shown, and the content of equiaxed primary α phase is 6 - 10%. The room temperature and high temperature tensile properties at 650 °C and 700 °C, and the creep and fatigue properties at 650 °C and 700 °C are shown in Table 1, and the comprehensive properties are excellent.

[0045] Table 1

[0046]

[0047] Example 2

[0048] A high temperature titanium alloy for aero - engines resistant to 700 °C high temperature. By weight percentage, the raw materials for preparing the high temperature titanium alloy include: Al: 5.9%, Sn: 3.9%, Hf: 2.5%, Mo: 0.3%, Si: 0.55%, Nb: 0.4%, Ta: 3.5%, W: 0.8%, C: 0.055%, impurities are O: 0.09% and Fe: 0.01%, and the balance is Ti. The measured β phase transformation point is 1048 °C.

[0049] A preparation method of a titanium alloy resistant to 700 °C high temperature for an aeroengine, the preparation method comprising the following steps:

[0050] S1. Prepare the Ti-Hf master alloy: The raw materials are the first sponge titanium with a particle size of 2 - 12.7 mm (the market sales company is Chaoyang Jinda Titanium Industry Co., Ltd.) and sponge hafnium with a particle size of 2 - 25.4 mm (the market sales company is Beijing Jinboyu Metal Technology Co., Ltd.). Mix 50% by weight of each of the first sponge titanium and sponge hafnium evenly and place them at the bottom of the melting crucible. Start the electron beam melting furnace, raise the current to 1200 A to melt the alloy materials in the crucible, cool to obtain the Ti-Hf master alloy ingot, and finally clean, crush, and screen the alloy ingot to obtain granular Ti-Hf master alloy.

[0051] S2. Ingot melting: Add 2540 g of Ti-Sn (Sn content 79%), 2600 g of Ti-Hf (Hf content 50%), 245 g of Al-Mo (Mo content 64%), 1900 g of Al-Si (Si content 15%), 290 g of Al-Nb (Nb content 73%), 2600 g of Al-Ta (Ta content 70%), 840 g of Al-W (W content 50%) master alloy, 70 g of Al foil, and 25.2 g of carbon powder to 42.2 kg of granular second sponge titanium, press the electrode, and use the welded electrode block for vacuum consumable melting. Obtain the alloy ingot by 3 times of vacuum consumable melting. The ingot has a diameter of 200 mm and a weight of 53 kg.

[0052] S3. Preheat the ingot in S2 to 950 °C and hold for 60 min, then raise the temperature to 1200 °C and hold for 12 h for homogenization heat treatment; perform cogging forging on the ingot after homogenization heat treatment in 2 heats. For the first heat, first preheat to 950 °C and hold for 60 min, then heat to 1180 °C and hold for 120 min. For the second heat, first preheat to 950 °C and hold for 60 min, then heat to 1100 °C and hold for 120 min. The deformation for each heat is 1 time of upsetting and drawing out, and the deformation amount of upsetting and drawing out is 45%. After forging deformation, air cooling is used for all, and finally obtain the billet after cogging in the β phase region.

[0053] S4. First, subject the blank in S3 to one - fire deformation in the first stage. Heat it to 1020°C and hold for 120 min, and deform it by one upsetting and drawing - out. The deformation amount of upsetting and drawing - out is 40%. After deformation, air - cool it. Then, subject it to one - fire deformation in the second stage. Heat it to 1080°C and hold for 120 min, and deform it by one upsetting and drawing - out. The deformation amount of upsetting and drawing - out is 50%. After deformation, water - cool it. Finally, subject it to six - fire deformation in the third stage. The heating temperatures of the six fires are 1020°C, 1020°C, 1010°C, 1000°C, 990°C, and 1000°C respectively, and the holding time is 120 min for all. Before the last fire, the deformation is one upsetting and drawing - out, and the deformation amount of upsetting and drawing - out is 40%. The last fire is die - forging forming, and the deformation amount is 30%, and the strain rate is 0.02 s -1 , and after deformation, air - cool it for all. Finally, obtain a forging blank with a diameter of 220 mm and a thickness of 85 mm.

[0054] S5. Subject the forging blank in S4 to solution and aging heat treatment. Solution treatment: 1030°C, hold for 2 h, oil - cool. Aging treatment: 710°C, hold for 5 h, air - cool.

[0055] For the forging blank with a diameter of 220 mm and a thickness of 85 mm prepared by the above method, the content of equiaxed primary α - phase is 6 - 8%. The room - temperature and high - temperature tensile properties at 650°C and 700°C, and the creep and fatigue properties at 650°C and 700°C are shown in Table 2, and the comprehensive properties are excellent.

[0056] Table 2

[0057]

[0058] Example 3

[0059] A 700°C - high - temperature - resistant titanium alloy for aero - engines. By weight percentage, the raw materials for preparing the high - temperature titanium alloy include: Al: 6.0%, Sn: 3.8%, Hf: 3.8%, Mo: 0.3%, Si: 0.58%, Nb: 0.4%, Ta: 4.0%, W: 0.9%, C: 0.058%, impurities are O: 0.08% and Fe: 0.01%, and the balance is Ti. The measured β - phase transformation point is 1050°C.

[0060] A preparation method of a 700°C - high - temperature - resistant titanium alloy for aero - engines. The preparation method includes the following steps:

[0061] S1. Preparation of Ti-Hf master alloy: The raw materials are the first sponge titanium with a particle size of 2 - 12.7 mm (market sales company: Chaoyang Jinda Titanium Industry Co., Ltd.) and sponge hafnium with a particle size of 2 - 25.4 mm (market sales company: Beijing Jinboyu Metal Technology Co., Ltd.). Mix 50% by weight of the first sponge titanium and sponge hafnium evenly and place them at the bottom of the melting crucible. Start the electron beam melting furnace and raise the current to 1200 A to melt the alloy materials in the crucible. Cool to obtain the Ti-Hf master alloy ingot. Finally, clean, crush, and screen the alloy ingot to obtain granular Ti-Hf master alloy.

[0062] S2. Ingot melting: Add 19.2 kg of Ti-Sn (Sn content 79%), 3.1 kg of Ti-Hf (Hf content 50%), 1.9 kg of Al-Mo (Mo content 64%), 15.6 kg of Al-Si (Si content 15%), 2.2 kg of Al-Nb (Nb content 73%), 23.0 kg of Al-Ta (Ta content 70%), 6.0 kg of Al-W (W content 60%) master alloy, 299 g of Al foil, and 209 g of carbon powder to 320 kg of granular second sponge titanium. Press the electrodes, and after welding the electrode blocks, use them for vacuum consumable melting. Obtain the alloy ingot through 4 times of vacuum consumable melting. The ingot has a diameter of 320 mm and a weight of 418 kg.

[0063] S3. Preheat the ingot in S2 to 950 °C and hold for 100 min, then raise the temperature to 1200 °C and hold for 18 h for homogenization heat treatment; perform 3 - fire cogging forging on the ingot after homogenization heat treatment. For the first fire, first preheat to 950 °C and hold for 60 min, then heat to 1200 °C and hold for 120 min. For the second fire, first preheat to 950 °C and hold for 60 min, then heat to 1150 °C and hold for 120 min. For the third fire, first preheat to 950 °C and hold for 60 min, then heat to 1100 °C and hold for 120 min. The deformation for each fire is 1 time of upsetting and drawing out, and the deformation amount of upsetting and drawing out is 45%. After forging deformation, air cooling is carried out for all, and finally obtain the billet after cogging in the β-phase region.

[0064] S4. The blank in S3 is first subjected to three - fire deformation in the first stage. The heating temperatures for the three fires are 1030°C, 1020°C, and 1010°C respectively, and the holding time for each is 180 min. Each fire deformation is one upsetting and drawing - out process, and the deformation amount of upsetting and drawing - out is 40%. After deformation, it is air - cooled. Then, it is subjected to two - fire deformation in the second stage. The heating temperature for both fires is 1080°C, and the holding time for each is 120 min. Each fire deformation is one upsetting and drawing - out process, and the deformation amount of upsetting and drawing - out is 45%. After the first - fire deformation, it is air - cooled, and after the second - fire deformation, it is water - cooled. Finally, it is subjected to eight - fire deformation in the third stage. The heating temperatures for the eight fires are 1020°C, 1020°C, 1020°C, 1010°C, 1010°C, 1000°C, 1000°C, and 990°C respectively, and the holding time for each is 120 min. Each fire deformation is one upsetting and drawing - out process, and the deformation amount of upsetting and drawing - out is 35%. After deformation, it is air - cooled. Finally, a billet with a diameter of 250 mm is obtained.

[0065] S5. A 40 - mm length is cut from the billet in S4 for solution and aging heat treatment. Solution treatment: 1035°C, holding for 2 h, oil - cooling; aging treatment: 710°C, holding for 5 h, air - cooling.

[0066] For the billet with a diameter of 250 mm prepared by the above method, the content of equiaxed primary α - phase is 6 - 8%. The room - temperature, 650°C, and 700°C high - temperature tensile, 650°C and 700°C creep and fatigue properties are shown in Table 3, and the comprehensive properties are excellent.

[0067] Table 3

[0068]

[0069] Comparative Example 1 (Using pure hafnium metal for ingot melting, with poor results)

[0070] A 700 - °C high - temperature - resistant titanium alloy for aero - engines. By weight percentage, the raw materials for preparing the high - temperature titanium alloy include: Al: 5.8%, Sn: 3.9%, Hf: 4.4%, Mo: 0.3%, Si: 0.42%, Nb: 0.4%, Ta: 3.5%, W: 0.8%, C: 0.058%, impurities are O: 0.08% and Fe: 0.02%, and the balance is Ti. The measured β - phase transformation point is 1060°C.

[0071] A preparation method of a 700 - °C high - temperature - resistant titanium alloy for aero - engines. The specific implementation method is the same as that of Example 2, except that:

[0072] S1. Chip - shaped hafnium metal with a size of 0 - 2 mm is prepared using a hafnium metal rod (market - sold by Beijing Jinboyu Metal Technology Co., Ltd.).

[0073] S2. Add 2,610 g of Ti-Sn (Sn content 79%), 2,290 g of metal hafnium chips (Hf content 99.8%), 245 g of Al-Mo (Mo content 64%), 1,460 g of Al-Si (Si content 15%), 286 g of Al-Nb (Nb content 73%), 2,600 g of Al-Ta (Ta content 70%), 835 g of Al-W (W content 50%) master alloy, 518 g of Al foil and 25.4 g of carbon powder to 41.1 kg of granular sponge titanium. Press the electrodes, and after welding the electrode blocks, use them for vacuum consumable melting. Obtain alloy ingots by 3 times of vacuum consumable melting. The ingot diameter is 200 mm and the weight is 52 kg.

[0074] S3. The specific implementation method is the same as that in Example 1.

[0075] S4. The specific implementation method is the same as that in Example 1.

[0076] S5. Cut a 50-mm section from the bar blank in S4 in the length direction for solution and aging heat treatment. Solution treatment: 1,048 °C, hold for 2 h, oil quench. Aging treatment: 710 °C, hold for 5 h, air cool.

[0077] For the bar blank with a diameter of 150 mm prepared by the above method, the macrostructure of the bar is as Figure 4 shown, and Hf inclusions appear, seriously affecting the compositional uniformity and the mechanical properties of the bar. The properties at the segregation area are shown in Table 4. The room-temperature plasticity at the segregation area is extremely low, and the property dispersion is large.

[0078] Table 4

[0079]

[0080] The above is the preferred implementation mode of the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the principle described in the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A titanium alloy resistant to 700 °C high temperature for aero-engines, characterized in that, By weight percentage, the raw materials for preparing the high-temperature titanium alloy include: Al: 5.5 - 7.0%, Sn: 3.0 - 5.0%, Hf: 2.0 - 4.5%, Mo: 0.0 - 1.0%, Si: 0.5 - 0.7%, Nb: 0.2% - 0.5%, Ta: 3.5% - 4.5%, W: 0.6 - 1.2%, C: 0.04 - 0.08%, and the balance is Ti and impurities; The rotating bending fatigue limit of the high-temperature titanium alloy at 700°C is 300 - 320 MPa, the creep stress at 700°C is 70 MPa, and the residual strain under the test condition of 100 h is ≤0.2%; The preparation method of the high-temperature titanium alloy includes the following steps: S1. Prepare the Ti-Hf master alloy: Mix the first sponge titanium and sponge hafnium evenly and place them at the bottom of the melting crucible. Start the electron beam melting furnace to melt the alloy materials in the crucible, cool to obtain the Ti-Hf master alloy ingot, and finally clean, crush, and screen the ingot to obtain granular Ti-Hf master alloy; S2. Ingot melting: Add the master alloys of Ti-Sn, Ti-Hf, Al-Mo, Al-Si, Al-Nb, Al-Ta, Al-W, pure Al, and carbon powder to the second sponge titanium, press the electrodes, and use the welded electrode blocks for vacuum consumable melting. After vacuum consumable melting, an alloy ingot is obtained; the Ti-Hf is the granular Ti-Hf master alloy prepared in S1; S3. Homogenization heat treatment and cogging forging of the ingot: Perform homogenization heat treatment on the alloy ingot in S2; preheat the alloy ingot after homogenization heat treatment and then perform cogging forging. After forging deformation, air cooling is used for all, and finally a billet after cogging in the β phase region is obtained; S4. Preparation of bar billet or die forging billet: Deform the billet in S3 in three stages. The first stage of deformation is to heat the billet to 100 - 20°C below the β transformation point, hold for heat preservation, and then perform 1 - 3 fire deformations. After deformation, air cooling is used for all; the second stage of deformation is to heat the billet to 20 - 40°C above the β transformation point, hold for heat preservation, and then perform 1 - 2 fire deformations. Water cooling is used after the last fire deformation in the second stage, and air cooling is used after the deformation before the last fire; the third stage of deformation is to heat the billet to 100 - 20°C below the β transformation point, hold for heat preservation, and then perform 3 - 8 fire deformations. After deformation, air cooling is used for all, and finally a bar billet or die forging billet is obtained; S5. Heat treatment of bar billet or die forging billet: Perform solution and aging heat treatment on the bar billet or die forging billet in S4 to obtain the high-temperature titanium alloy.

2. The high-temperature titanium alloy according to claim 1, wherein The particle sizes of the first sponge titanium and the second sponge titanium are both 0.83 - 12.7 mm, and the particle size of sponge hafnium is 2 - 25.4 mm.

3. The high-temperature titanium alloy according to claim 2, wherein The steps of the homogenization heat treatment in S3 include: Preheat the alloy ingot in S2 to 900 - 1000°C for heat preservation, then raise the temperature to 1150 - 1200°C, and hold for 12 - 24 h.

4. The high-temperature titanium alloy according to claim 3, characterized in that, The steps of the cogging forging in S3 include: Heat the alloy ingot to 30 - 200°C above the β transformation point for heat preservation, and then perform 2 - 4 fire cogging forging.

5. The high-temperature titanium alloy according to claim 3, characterized in that, The upsetting and drawing deformation amounts in the first stage, the second stage, and the third stage of deformation in S4 are all 30 - 70%.

6. The high-temperature titanium alloy according to claim 1, wherein In the third stage of S4, the pre-deformation before the last heating is upsetting and drawing out once, and the deformation amount of upsetting and drawing out is 30% to 50%; the last heating is upsetting and drawing out, or the last heating is die forging forming, and the deformation amount is 30% to 70%.

7. The high-temperature titanium alloy according to claim 6, characterized in that, The strain rate of die forging of the die forging blank in S4 is 0.01 - 0.1 s -1 .

Images