Temperature control treatment method and application of powder hot isostatic pressing titanium-aluminum alloy

Abstract

The invention belongs to the field of powder metallurgy light high-temperature materials, and relates to a temperature control treatment method and application of a powder hot isostatic pressing titanium-aluminum alloy. The method comprises the following steps: firstly, preparing TiAl-(W, Mo, Ta and Nb) alloy powder; then the TiAl-(W, Mo, Ta and Nb) alloy powder is subjected to hot isostatic pressing treatment, and a first titanium-aluminum alloy intermediate blank is obtained; then carrying out heat treatment to obtain a second titanium-aluminum alloy intermediate blank; then, stress relief annealing and stabilizing treatment are conducted on the second titanium-aluminum alloy intermediate blank, and a third titanium-aluminum alloy intermediate blank is obtained; and finally, a surface oxide layer of the third titanium-aluminum alloy is removed, and a titanium-aluminum alloy finished product is obtained. According to the method, generation of brittle B2 and omega harmful phases under high-temperature long-time service of the over-peritectic TiAl alloy can be avoided, the high-temperature performance of the titanium-aluminum alloy can be effectively improved, and the service temperature of the titanium-aluminum alloy is increased to 850 DEG C.

Description

Technical Field

[0001] The present invention belongs to the field of powder metallurgy lightweight high-temperature materials, and relates to a temperature control treatment method and application of powder hot isostatic pressing titanium aluminide alloy. Background Art

[0002] γ-Titanium aluminide alloy (γ-TiAl alloy) has great advantages in high-temperature structural materials in industries such as aviation, aerospace, and gas turbines due to its light weight, high specific strength, and excellent creep resistance at high temperatures. It can be widely used in low-pressure turbine blades of aeroengines, impellers of automotive turbochargers, high-temperature nuclear power fields, power generation fields, and supersonic transport systems, etc.

[0003] To improve the high-temperature service performance of titanium aluminide alloy, alloying elements can be added to it. W (tungsten), Mo (molybdenum), Ta (tantalum), and Nb (niobium) can all improve the high-temperature strength, creep resistance, and oxidation resistance of titanium aluminide alloy, and promote the formation of metastable structures by reducing the substructure energy, achieving grain refinement and strengthening. However, the addition of heavy elements easily leads to composition segregation and affects the material properties, making high alloying more obvious. Room temperature plasticity is also a basic index that needs to be guaranteed for engineering applications. Although current studies have shown that cast high-Ta titanium aluminide alloy and medium-Nb low-Ta titanium aluminide alloy can obtain fine lamellar structures through cyclic heat treatment or multi-step heat treatment, etc., thereby obtaining excellent room temperature plasticity and high-temperature performance. However, complex heat treatment methods are not suitable for engineering applications.

[0004] In addition, a Chinese invention patent with the application number: 201710305177.6 and the publication date: October 19, 2018 discloses a cast γ-TiAl alloy applicable to 800°C. This alloy is composed of Al (aluminum), Nb, Ta, B (boron), and Ti (titanium), and can ensure good oxidation resistance and casting performance of the alloy while improving the strength of the alloy. It is applicable to manufacturing hot-end components such as low-pressure turbine blades of aerospace aircraft, inlet wall panels of hypersonic aircraft, and turbochargers of tanks and automobiles. In this method, due to the addition of relatively dense Nb and Ta elements to the titanium aluminide alloy, it is difficult to avoid the problems of composition segregation and non-uniform structure in the cast alloy. If an ideal structure with uniform fineness is to be obtained, complex heat treatment regulation is required, and complex heat treatment regulation is not conducive to engineering applications. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned disadvantages of the prior art and propose a temperature control treatment method and application of powder hot isostatic pressing titanium aluminide alloy.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions: A temperature control treatment method of powder hot isostatic pressing titanium aluminide alloy, such as Figure 1As shown, it includes the following steps: Step 1: Prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Step 2: Perform hot isostatic pressing on the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminide alloy intermediate blank; Step 3: Heat-treat the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank; Step 4: Perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank; Step 5: Remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product.

[0007] Specifically, in Step 1, the preparation of TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process is as follows: First, uniformly melt the end of the TiAl-(W, Mo, Ta, Nb) alloy rod to form atomized droplets. The atomized droplets are thrown out from the end of the TiAl-(W, Mo, Ta, Nb) alloy rod under the action of centrifugal force to form fine droplets. The fine droplets are rapidly cooled into spherical particles in an inert gas environment and fall into the collector at the bottom of the reaction chamber to obtain full-sized TiAl-(W, Mo, Ta, Nb) alloy powder.

[0008] In Step 2, the hot isostatic pressing treatment is specifically as follows: The TiAl-(W, Mo, Ta, Nb) alloy powder is filled into a sheath and then subjected to hot isostatic pressing sintering, and then the sheath is removed by machining to obtain a powder metallurgy titanium aluminide alloy with a specific shape; among them, the sheath can be designed into different shapes according to requirements, and the sheath material is carbon steel or pure titanium.

[0009] In summary, the present invention first adopts the ultra-high speed plasma rotating electrode process (SS-PREP ®)(1) It is possible to obtain Ti-Al alloy powder with low oxygen content and low hollowness rate, and then perform powder hot isostatic pressing below the transformation temperature of the α single-phase region. This step can not only reduce the compositional segregation of W, Mo, Ta, and Nb, but also endow the Ti-Al alloy with an initially uniform and fine microstructure, showing excellent isotropic characteristics. Then, controlled-temperature heat treatment is carried out. Specifically, the Ti-Al alloy is placed above the α single-phase region for short-time heat preservation to transform the Ti-Al alloy into the α phase while avoiding excessive grain growth. After that, it is slowly cooled to the two-phase region to fully transform it into a lamellar structure, and then air-cooled to avoid grain size growth and lamellar coarsening. Finally, stress relief annealing and stabilization treatment are carried out above the target service temperature to obtain a stabilized microstructure. Different from the complex process in the traditional process where casting Ta-containing Ti-Al alloy requires multi-step or cyclic heat treatment to form a fine-grained near-lamellar structure, the heat treatment process proposed by the present invention realizes the refinement and uniform distribution of the lamellar structure while significantly shortening the process cycle by precisely controlling the heat treatment parameters, providing an efficient and reliable technical solution for the engineering preparation of this alloy system.

[0010] Further, in the TiAl-(W, Mo, Ta, Nb) alloy powder in the step (1): the Al content is 47.5 at.% to 49 at.%, the total content of W, Mo, Ta, and Nb is 3 at.% to 6 at.%, and the balance is Ti.

[0011] Specifically, when the Al content is in the range of 47.5 at.% to 49 at.%, the hypereutectoid Ti-Al alloy exhibits extremely excellent room-temperature plasticity and oxidation resistance. This compositional advantage enables it to effectively avoid the formation of brittle B2 and ω harmful phases during long-term high-temperature service, thus ensuring the stability and reliability of the material structure.

[0012] It should be noted that by adding 3 at.% to 6 at.% of elements such as W, Mo, Ta, and Nb to the hypereutectoid Ti-Al alloy, its high-temperature performance can be significantly improved, and the service temperature can be successfully increased to 850 °C. However, the addition amount of alloying elements needs to be accurately controlled. If the addition amount is too small, the improvement of high-temperature performance is minimal, and it is difficult to meet the service requirements above 850 °C; conversely, if excessive amounts of W, Mo, Ta, and Nb elements are added, a series of negative effects will be caused, such as aggravated compositional segregation, resulting in non-uniform material properties; increased density, bringing a burden to practical applications; and a significant increase in cost, which is not conducive to large-scale engineering applications. More critically, when the temperature exceeds 800 °C, brittle B2 and ω harmful phases may be induced, which will seriously affect the stable service of the material at higher temperatures and cannot meet the stringent requirements for high-temperature stability of materials in high-end fields such as aerospace and energy power.

[0013] Further, the atomic ratio of Nb:Ta:(W + Mo) is (2 - 4):(0.5 - 2):(0 - 2).

[0014] Specifically, adding a moderate amount (2 at.% - 4 at.%) of Nb element can significantly improve the high-temperature performance of TiAl alloys. At the same time, only a small amount (0.5 at.% - 2 at.%) of Ta element needs to be added to effectively change the interface state of the peritectic titanium aluminide alloy, greatly reducing the interface energy. Thus, by precisely controlling the cooling rate from the single-phase region, a metastable microstructure transformation can be induced inside the titanium aluminide alloy. Utilizing the specific orientation relationship between the γ phase and the α 2 phase, grain refinement can be successfully achieved, obtaining a fine-grained near-lamellar microstructure. This microstructure ensures excellent room-temperature plasticity and high-temperature performance of the titanium aluminide alloy. However, Ta element is more prone to segregation and has a higher cost than Nb, so too much Ta element should not be added.

[0015] Further, the particle size of the TiAl-(W, Mo, Ta, Nb) alloy powder is 45 μm - 250 μm.

[0016] Further, in the second step, the temperature of the hot isostatic pressing is 10°C - 120°C below the α single-phase region transformation temperature, the pressure is 120 MPa - 155 MPa, and the time is 2 h - 8 h.

[0017] Specifically, performing powder hot isostatic pressing at 10°C - 120°C below the α single-phase region can effectively reduce the component segregation problems of W, Mo, Ta, and Nb elements, and then obtain a titanium aluminide alloy with a uniform and fine initial microstructure. This titanium aluminide alloy has excellent isotropic characteristics. If the forming temperature of the hot isostatic pressing is too high, it may cause excessive grain growth, having an adverse effect on the mechanical properties of the material. While if the forming temperature of the hot isostatic pressing is too low, it is not conducive to the full diffusion of W, Mo, Ta, and Nb, which may lead to component segregation and insufficient density of the material. The pressure of the hot isostatic pressing is 120 MPa - 155 MPa, which can ensure that the parts after hot isostatic pressing reach a dense state. Too low pressure will result in insufficient density of the parts, while too high pressure will not only pose higher requirements for the hot isostatic pressing furnace but also may bring safety hazards. The time of the hot isostatic pressing is controlled within 2 h - 8 h. If the time is too short, the parts cannot reach a completely dense state. If the time is too long, it will lead to grain growth.

[0018] Further, the temperature-controlled heat treatment in the third step is as follows: first, keep it at a temperature 5°C - 30°C above the α single-phase region transformation temperature for 10 min - 30 min, then furnace cool to the α + γ two-phase region temperature, and finally air cool to room temperature.

[0019] Specifically, the temperature range of the α+γ two-phase region is between 1250°C and 1380°C, which needs to be determined according to the addition amount of alloying elements. For cast titanium aluminides with similar compositions, to obtain similar fine near-lamellar microstructures, complex heat treatment regulation is required. The traditional heat treatment method is high-temperature long-time homogenization + holding in the single-phase region + tempering in the two-phase region + multiple cycle heat treatment. In contrast, based on the initial fine and uniform microstructure of powder metallurgy, and the fact that Ta can reduce the interfacial energy of hypereutectic titanium aluminides, and thus metastable and lamellar microstructures can be generated during slow cooling in the single-phase region, the heat treatment process of the present invention can be greatly simplified, which is beneficial to engineering applications.

[0020] It should be noted that short-time holding is carried out at 5°C to 30°C above the transformation temperature of the α single-phase region, so that the titanium aluminide is fully transformed into the α phase while avoiding excessive grain growth.

[0021] Furthermore, the time of furnace cooling is 8 min to 12 min.

[0022] Specifically, during the temperature-controlled heat treatment, when cooling from the α single-phase region to the α+γ two-phase region by furnace cooling, γ lamellae will precipitate from the α phase, and thus a lamellar microstructure is formed. It is more appropriate to control the furnace cooling time within 8 min to 12 min. On the one hand, it can provide sufficient time for the precipitation of γ lamellae to ensure the formation of sufficient lamellar microstructures. On the other hand, it can avoid excessive growth and coarsening of lamellar clusters due to too long residence time in the two-phase region, thereby reducing the mechanical properties. The heat treatment process proposed by the present invention realizes the refinement and uniform distribution of the lamellar microstructure while significantly shortening the process cycle by precisely controlling the solution parameters, providing an efficient and reliable technical solution for the engineering preparation of this alloy system.

[0023] It should be noted that if the holding time of the temperature-controlled heat treatment is defined as t and the minimum size of the workpiece is a, then t and a satisfy t≥a / 2, and t∈[5, 30], where the unit of t is min and the unit of a is mm.

[0024] Furthermore, in step four, both stress relief annealing and stabilization treatment are carried out at a temperature of 750°C to 950°C for 2 h to 6 h.

[0025] In addition, the present invention also discloses a powder metallurgy titanium aluminide finished product prepared by a temperature-controlled treatment method of powder hot isostatic pressing titanium aluminide, and the room temperature plasticity of the titanium aluminide finished product is 1.52% to 1.93%.

[0026] Finally, the present invention also discloses an application of a titanium aluminide finished product prepared by a temperature-controlled treatment method of powder hot isostatic pressing titanium aluminide in manufacturing low-pressure turbine blades of engine titanium aluminides.

[0027] Compared with the prior art, the present invention has the following beneficial effects: First, the present invention focuses on the hypoperitectic Ti-Al alloy system with an Al content of 47.5 at.% to 49 at.%. On this basis, adding appropriate amounts of W, Mo, Ta, and Nb elements can bring three significant advantages: First, it can prevent the formation of brittle B2 and ω harmful phases during the long-term high-temperature service of hypoperitectic TiAl alloys; Second, it can effectively improve the high-temperature performance of Ti-Al alloys and increase their service temperature to 850 °C; Third, compared with Nb-TiAl and high-Ta TiAl alloys, the present invention avoids the problem of aggravated segregation caused by the large addition of Nb and Ta by reasonably controlling the element addition amount, and at the same time, effectively reduces the production cost; Second, adding Ta element can change the interface state of hypoperitectic Ti-Al alloys and reduce the interface energy; during the cooling process of the alloy from the single-phase region, the metastable microstructure transformation can be triggered by precisely controlling the cooling rate; by virtue of the special orientation relationship between the γ phase and the α 2 phase, grain refinement can be achieved, and a fine-grained near-lamellar structure can be obtained, ensuring that the finished Ti-Al alloy has excellent room-temperature plasticity and high-temperature performance; In summary, the treatment method of the present invention solves the deficiencies of existing Ti-Al alloys and their preparation processes in terms of composition design, process route, mechanical properties, and engineering operation convenience, and not only meets the high-temperature service requirements but also is convenient and controllable in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings here are incorporated into the specification and form a part of this specification, and are used together with the specification to explain the principles of the present invention.

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 is the flowchart of the temperature control treatment method of the present invention; Figure 2 is the scanning electron microscope microstructural photograph of Example 1 in the present invention; Figure 3 is the scanning electron microscope microstructural photograph of Example 2 in the present invention; Figure 4 is the scanning electron microscope microstructural photograph of Example 3 in the present invention; Figure 5 is the scanning electron microscope microstructural photograph of Example 4 in the present invention; Figure 6SEM micrograph of Example 5 in the present invention; Figure 7 SEM micrograph of Example 1 in the present invention after high-temperature thermal exposure; Figure 8 SEM micrograph of Example 2 in the present invention after high-temperature thermal exposure; Figure 9 SEM micrograph of Example 3 in the present invention after high-temperature thermal exposure; Figure 10 SEM micrograph of Example 4 in the present invention after high-temperature thermal exposure; Figure 11 SEM micrograph of Example 5 in the present invention after high-temperature thermal exposure. Detailed implementation manners

[0031] Here, the exemplary embodiments will be described in detail. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the present invention. On the contrary, they are merely examples consistent with some aspects of the present invention detailed in the appended claims.

[0032] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] It should be noted that in the following five embodiments, the particle size of the TiAl-(W, Mo, Ta, Nb) alloy powder is 45 μm to 250 μm. Example 1

[0034] This embodiment provides a temperature control method for powder hot isostatic pressing titanium aluminide, which is specifically implemented according to the following steps: Step 1, prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Specifically, in the TiAl-(W, Mo, Ta, Nb) alloy powder: the Al content is 48.3 at.%, the Nb content is 3 at.%, the Ta content is 1 at.%, the W content is 0.5 at.%, and the Mo content is 0; the atomic ratio of Nb:Ta:(W + Mo) is: 3:1:0.5, and the total content of W, Mo, Ta, and Nb is 4.5 at.%; Step 2, perform hot isostatic pressing on the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminide intermediate blank; During hot isostatic pressing, the used envelope is a cylindrical envelope with a diameter of 30 mm and a height of 80 mm. The powder is loaded into the envelope, degassed and sealed by welding, and then hot isostatic pressing sintering is carried out. Subsequently, the envelope is removed by machining to obtain titanium aluminide, and the envelope material is carbon steel; Among them, the hot isostatic pressing temperature is 1270 °C (120 °C below the transformation temperature of the α single-phase region), the pressure is 120 MPa, and the time is 2 h; Step 3: Heat-treat the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank; Among them, the controlled-temperature heat treatment is carried out at a temperature of 1420 °C (30 °C above the transformation temperature of the α single-phase region) for 18 min, then furnace-cooled at a rate of 10 °C / min for 8 min to 1340 °C (the temperature of the α + γ two-phase region), and finally air-cooled to room temperature; Step 4: Perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank; Specifically, both the stress relief annealing and the stabilization treatment are carried out at a temperature of 750 °C for 6 h; Step 5: Remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product. The scanning electron microscope micrograph of this finished titanium aluminide alloy product is as Figure 2 shown, all of which are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of this finished titanium aluminide alloy product after high-temperature thermal exposure is as Figure 7 shown, and it can be seen that the structure is stable after long-term high-temperature thermal exposure; Among them, the room-temperature tensile plasticity of the finished titanium aluminide alloy product is 1.52%, the tensile yield strength at 750 °C is 363 MPa, and the tensile yield strength at 850 °C is 338 MPa; the oxidation weight gain at 750 °C is 0.29 mg / cm 2 , and the oxidation weight gain at 850 °C is 0.84 mg / cm 2 , the creep rupture life at 850 °C / 125 MPa is 129 h, the creep rupture life at 750 °C / 250 MPa is 256 h, and the creep rupture life at 650 °C / 350 MPa is 385 h without interruption or stop. Example 2

[0035] This example provides a method for controlling the temperature of a powder hot isostatic pressing titanium aluminide alloy, which is specifically implemented according to the following steps: Step 1: Prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Specifically, in the TiAl-(W, Mo, Ta, Nb) alloy powder: the Al content is 49.0 at.%, the Nb content is 2 at.%, the Ta content is 0.5 at.%, and the Mo content is 0.5 at.%; the atomic ratio of Nb:Ta:(W + Mo) is: 2:0.5:0.5, and the total content of W, Mo, Ta, and Nb is 3 at.%; Step 2: Perform hot isostatic pressing treatment on the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminide alloy intermediate blank; During the hot isostatic pressing process, the used envelope is a cuboid envelope with a length of 20 mm, a width of 35 mm, and a height of 90 mm. The powder is loaded into the envelope, degassed and sealed by welding, and then hot isostatic pressing sintering is carried out. Subsequently, the envelope is removed by machining to obtain a titanium aluminide alloy, and the envelope material is pure titanium; Among them, the hot isostatic pressing temperature is 1315 °C (70 °C below the α single-phase region transformation temperature), the pressure is 138 MPa, and the time is 5 h; Step 3, heat-treat the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank; Among them, the controlled-temperature heat treatment is to hold for 10 min at a temperature of 1403 °C (18 °C above the α single-phase region transformation temperature), and then furnace-cool at a rate of 10 °C / min for 12 min to 1298 °C (α+γ two-phase region temperature), and finally air-cool to room temperature; Step 4, perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank; Step 5, remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product. The scanning electron microscope microstructural photos of the finished titanium aluminide alloy product are as Figure 3 shown, all of which are uniform and fine near-lamellar structures; the scanning electron microscope microstructural photos of the finished titanium aluminide alloy product after high-temperature thermal exposure are as Figure 8 shown, and it can be seen that the microstructure is stable after long-term high-temperature thermal exposure; Among them, the room-temperature tensile plasticity of the finished titanium aluminide alloy product is 1.93%, the tensile yield strength at 750 °C is 369 MPa, and the tensile yield strength at 850 °C is 341 MPa; the oxidation weight gain at 750 °C is not higher than 0.27 mg / cm 2 , and the oxidation weight gain at 850 °C is not higher than 0.89 mg / cm 2 , the creep life at 850 °C / 125 MPa is not less than 135 h, the creep life at 750 °C / 250 MPa is 263 h, and the creep life at 650 °C / 350 MPa is 385 h without interruption. Example 3

[0036] This example provides a method for controlling the temperature treatment of a powder hot isostatic pressing titanium aluminide alloy, which is specifically implemented according to the following steps: Step 1, prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Specifically, in the TiAl-(W, Mo, Ta, Nb) alloy powder: the Al content is 47.5 at.%, the Nb content is 4 at.%, and the Ta content is 2 at.%; the atomic ratio of Nb:Ta:(W+Mo) is: 4:2:0, and the total content of W, Mo, Ta, and Nb is 6 at.%; Step 2: Subject the TiAl-(W, Mo, Ta, Nb) alloy powder to hot isostatic pressing to obtain a first titanium aluminide alloy intermediate blank; During hot isostatic pressing, the can used is a cylindrical can with a diameter of 35 mm and a height of 90 mm. The powder is loaded into the can, degassed, sealed by welding, and then subjected to hot isostatic pressing sintering. Subsequently, the can is removed by machining to obtain a titanium aluminide alloy. The can material is pure titanium; Among them, the hot isostatic pressing temperature is 1395 °C (10 °C below the α single-phase region transformation temperature), the pressure is 155 MPa, and the time is 8 h; Step 3: Heat-treat the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank; Among them, the controlled-temperature heat treatment is carried out at a temperature of 1410 °C (5 °C above the α single-phase region transformation temperature) for 30 min, and then furnace-cooled at a rate of 10 °C / min for 10 min to 1310 °C (α + γ two-phase region temperature), and finally air-cooled to room temperature; Step 4: Perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank; Step 5: Remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product. The scanning electron microscope micrograph of this finished titanium aluminide alloy product is as Figure 4 shown, all of which are uniform and fine near-lamellar structures; the scanning electron microscope microstructure photograph of this finished titanium aluminide alloy product after high-temperature thermal exposure is as Figure 9 shown, indicating that the microstructure is stable after high-temperature long-term thermal exposure; Among them, the room-temperature tensile plasticity of the finished titanium aluminide alloy product is 1.81%, the tensile yield strength at 750 °C is 377 MPa, and the tensile yield strength at 850 °C is 345 MPa; the oxidation weight gain at 750 °C is 0.26 mg / cm 2 , and the oxidation weight gain at 850 °C is not higher than 0.83 mg / cm 2 , the creep life at 850 °C / 125 MPa is 141 h, the creep life at 750 °C / 250 MPa is 271 h, and the creep life at 650 °C / 350 MPa is 385 h without interruption or stop. Example 4

[0037] This example provides a method for controlling the temperature treatment of a powder hot isostatic pressing titanium aluminide alloy, which is specifically implemented according to the following steps: Step 1: Prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Specifically, in the TiAl-(W, Mo, Ta, Nb) alloy powder: the Al content is 49.0 at.%, the Nb content is 3 at.%, the Ta content is 1 at.%, the W content is 0.5 at.%, and the Mo content is 1 at.%; the atomic ratio of Nb:Ta:(W + Mo) is 3:1:1, and the total content of W, Mo, Ta, and Nb is 5 at.%. Step 2: Perform hot isostatic pressing on the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminide alloy intermediate blank. During the hot isostatic pressing process, the used envelope is a cuboid envelope with a length of 30 mm, a width of 30 mm, and a height of 90 mm. The powder is loaded into the envelope, degassed and sealed by welding, and then subjected to hot isostatic pressing sintering. Subsequently, the envelope is removed by machining to obtain a titanium aluminide alloy. The envelope material is pure titanium. Among them, the hot isostatic pressing temperature is 1320 °C (80 °C below the α single-phase region transformation temperature), the pressure is 140 MPa, and the time is 5 h. Step 3: Heat-treat the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank. Among them, the controlled-temperature heat treatment is carried out at a temperature of 1420 °C (20 °C above the α single-phase region transformation temperature) for 15 min, and then furnace-cooled at a rate of 10 °C / min for 9 min to 1330 °C (α + γ two-phase region temperature), and finally air-cooled to room temperature. Step 4: Perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank. Both the stress relief annealing and the stabilization treatment are carried out at a temperature of 875 °C for 4 h. Step 5: Remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product. The scanning electron microscope micrograph of this finished titanium aluminide alloy product is as Figure 5 shown, all of which are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of this finished titanium aluminide alloy product after high-temperature thermal exposure is as Figure 10 shown, and it can be seen that the structure is stable after long-term high-temperature thermal exposure; Among them, the room-temperature tensile plasticity of the finished titanium aluminide alloy product is 1.72%, the tensile yield strength at 750 °C is 375 MPa, and the tensile yield strength at 850 °C is 342 MPa; the oxidation weight gain at 750 °C is not higher than 0.28 mg / cm 2 , the oxidation weight gain at 850 °C is not higher than 0.86 mg / cm 2 , the creep rupture life at 850 °C / 125 MPa is not less than 135 h, the creep rupture life at 750 °C / 250 MPa is 263 h, and the creep rupture life at 650 °C / 350 MPa is 385 h without interruption or stop. Example 5

[0038] This embodiment provides a temperature control method for powder hot isostatic pressing of titanium aluminide alloy, which is specifically implemented according to the following steps: Step 1, prepare TiAl-(W, Mo, Ta, Nb) alloy powder by the plasma rotating electrode process; Specifically, in the TiAl-(W, Mo, Ta, Nb) alloy powder: the Al content is 49.0 at.%, the Nb content is 3 at.%, the Ta content is 1 at.%, and the W content is 2 at.%; the atomic ratio of Nb:Ta:(W + Mo) is 3:1:2, and the total content of W, Mo, Ta, and Nb is 6 at.%; Step 2, perform hot isostatic pressing on the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminide alloy intermediate blank; During hot isostatic pressing, the used jacket is a cylindrical jacket with a diameter of 35 mm and a height of 90 mm. The powder is filled into the jacket, degassed and sealed by welding, and then hot isostatic pressing sintering is carried out. Subsequently, the jacket is removed by machining to obtain a titanium aluminide alloy, and the jacket material is pure titanium; Among them, the hot isostatic pressing temperature is 1335 °C (70 °C below the α single-phase region transformation temperature), the pressure is 138 MPa, and the time is 5 h; Step 3, perform heat treatment on the first titanium aluminide alloy intermediate blank to obtain a second titanium aluminide alloy intermediate blank; Among them, the temperature control heat treatment is to hold for 20 min at a temperature of 1425 °C (20 °C above the α single-phase region transformation temperature), then furnace cool at a rate of 10 °C / min for 12 min to 1305 °C (α + γ two-phase region temperature), and finally air cool to room temperature; Step 4, perform stress relief annealing and stabilization treatment on the second titanium aluminide alloy intermediate blank to obtain a third titanium aluminide alloy intermediate blank; both the stress relief annealing and the stabilization treatment are carried out at a temperature of 850 °C for 4 h; Step 5, remove the surface oxide layer of the third titanium aluminide alloy intermediate blank to obtain a finished titanium aluminide alloy product. The scanning electron microscope micrographs of the finished titanium aluminide alloy product are as Figure 6 shown, all of which are uniform and fine near-lamellar structures; the scanning electron microscope micrographs of the finished titanium aluminide alloy product after high-temperature thermal exposure are as Figure 11 shown, and it can be seen that the structure is stable after long-term high-temperature thermal exposure; Among them, the room-temperature tensile plasticity of the finished titanium aluminide alloy product is 1.85%, the tensile yield strength at 750 °C is 372 MPa, and the tensile yield strength at 850 °C is 343 MPa; the oxidation weight gain at 750 °C is not higher than 0.27 mg / cm 2 , and the oxidation weight gain at 850 °C is not higher than 0.85 mg / cm 2, the creep rupture life under the conditions of 850°C / 125 MPa is not less than 140 h, the creep rupture life under the conditions of 750°C / 250 MPa is 263 h, and the creep rupture life under the conditions of 650°C / 350 MPa is 385 h without interruption or shutdown.

[0039] The performance of Examples 1-5 is shown in the following table:

[0040] As can be seen from the above table, in Examples 1-5, the room temperature plasticity (room temperature tensile elongation) of the titanium aluminide alloy finished product is > 1.5%, the tensile yield strength at 750°C is not less than 360 MPa, and the tensile yield strength at 850°C is not less than 330 MPa; the oxidation weight gain at 750°C is not higher than 0.31 mg / cm 2 , the oxidation weight gain at 850°C is not higher than 0.94 mg / cm 2 , the creep rupture life at 850°C / 125 MPa is not less than 125 h, the creep rupture life at 750°C / 250 MPa is not less than 250 h, and the creep rupture life at 650°C / 350 MPa is not less than 380 h.

[0041] The above are only specific embodiments of the present invention, enabling those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0042] It should be understood that the present invention is not limited to the above-described content and can be modified and changed without departing from its scope. The scope of the present invention is only limited by the appended claims.

Claims

1. A temperature control treatment method for hot isostatic pressing of titanium aluminum alloy powder, characterized in that: The following steps are involved: Step 1: preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process; Step 2: hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminum alloy intermediate billet; Step 3: heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet; Step 4: performing stress relief annealing and stabilization treatment on the second titanium-aluminum alloy intermediate billet to obtain a third titanium-aluminum alloy intermediate billet; Step 5: removing the surface oxide layer of the third titanium-aluminum alloy intermediate billet to obtain a titanium-aluminum alloy finished product.

2. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: In the TiAl-(W, Mo, Ta, Nb) alloy powder of step 1, the Al content is 47.5at.%~49at.%, the total content of W, Mo, Ta and Nb is 3at.%~6at.%, and the balance is Ti.

3. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 2, characterized in that: In the TiAl-(W, Mo, Ta, Nb) alloy powder, the atomic ratio of Nb:Ta:(W+Mo) is (2-4):(0.5-2):(0-2).

4. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: The particle size of the TiAl-(W, Mo, Ta, Nb) alloy powder is 45 μm to 250 μm.

5. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: In the step 2, the temperature of the hot isostatic pressing treatment is 10°C to 120°C below the α single-phase region transformation temperature, the pressure is 120MPa to 155MPa, and the time is 2h to 8h.

6. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: The temperature-controlled heat treatment in step three is: first, keep the temperature at 5°C to 30°C above the transformation temperature of the α single-phase region for 10min to 30min, then furnace cool to the temperature of the α+γ two-phase region, and finally air cool to room temperature.

7. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 6, characterized in that: The furnace cooling time is 8min~12min.

8. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: In the step 4, the stress relief annealing and stabilization treatment are both carried out at a temperature of 750° C. to 950° C. for 2 h to 6 h.

9. A titanium aluminum alloy product obtained by the temperature control treatment method according to any one of claims 1 to 8, characterized in that: The room temperature plasticity of the titanium aluminum alloy product is 1.52% to 1.93%.

10. Use of a titanium-aluminum alloy finished product obtained by the temperature control treatment method according to any one of claims 1 to 8 in manufacturing titanium-aluminum alloy low-pressure turbine blades for engines.

Images