A temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder and its application

Abstract

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 a powder hot isostatically pressed titanium aluminum alloy. The method comprises the following steps: first preparing TiAl-(W, Mo, Ta, Nb) alloy powder; then hot isostatically pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminum alloy intermediate billet; then performing heat treatment to obtain a second titanium aluminum alloy intermediate billet; then stress-relief annealing and stabilization treatment on the second titanium aluminum alloy intermediate billet to obtain a third titanium aluminum alloy intermediate billet; finally, removing the surface oxide layer of the third titanium aluminum alloy to obtain a titanium aluminum alloy finished product. This method can avoid the generation of brittle B2 and ω harmful phases in hyperperitectic TiAl alloys under high-temperature and long-term service, and can effectively improve the high-temperature performance of the titanium aluminum alloy, raising its service temperature to 850°C.

Description

Technical Field

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

[0002] γ-titanium aluminum alloy (γ-TiAl alloy) has great advantages as a high-temperature structural material in the aviation, aerospace, gas turbine and other industries due to its light weight, high specific strength and excellent creep resistance at high temperatures. It can be widely used in aircraft engine low-pressure turbine blades, automotive turbocharger impellers, high-temperature nuclear power fields, power generation fields and supersonic transportation systems.

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

[0004] Furthermore, a Chinese invention patent application with application number 201710305177.6 and publication date October 19, 2018, discloses a cast γ-TiAl alloy suitable for temperatures up to 800°C. Composed of Al (aluminum), Nb, Ta, B (boron), and Ti (titanium), this alloy offers excellent oxidation resistance and castability while also improving strength. It is suitable for manufacturing hot-end components such as low-pressure turbine blades for aerospace vehicles, inlet panels for hypersonic vehicles, and supercharger turbines for tanks and automobiles. Due to the addition of the densely packed elements Nb and Ta to the TiAl alloy, this casting process inevitably suffers from compositional segregation and microstructure inhomogeneity. Achieving an ideal, uniform, and fine microstructure requires complex heat treatment, which is not conducive to engineering applications. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and to provide a temperature control treatment method for hot isostatic pressing of powder titanium aluminum alloy and its application.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, such asFigure 1 As shown, the following steps are included:

[0008] Step 1: Prepare TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0009] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium aluminum alloy intermediate billet;

[0010] Step 3: heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0011] 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;

[0012] Step 5: removing the surface oxide layer of the third titanium-aluminum alloy intermediate billet to obtain a titanium-aluminum alloy finished product.

[0013] Specifically, in step 1, the TiAl-(W, Mo, Ta, Nb) alloy powder is prepared by a plasma rotating electrode process as follows: the end of the TiAl-(W, Mo, Ta, Nb) alloy rod is first uniformly melted to form atomized droplets, and 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 a collector at the bottom of the reaction chamber to obtain full-size TiAl-(W, Mo, Ta, Nb) alloy powder.

[0014] In step 2, the hot isostatic pressing treatment is specifically as follows: TiAl-(W, Mo, Ta, Nb) alloy powder is placed in a sheath and then hot isostatically sintered, and then the sheath is removed by processing to obtain a powder metallurgy titanium aluminum alloy with a specific shape; wherein the sheath can be designed into different shapes according to requirements, and the sheath material is carbon steel or pure titanium.

[0015] In summary, the present invention first adopts the ultra-high speed plasma rotating electrode process (SS-PREP ®) can obtain titanium-aluminum alloy powder with low oxygen addition and low hollow powder rate, and then hot isostatic pressing of powder is carried out below the transformation temperature of the α single-phase region. This step can not only reduce the component segregation of W, Mo, Ta and Nb, but also make the titanium-aluminum alloy have an initial uniform and fine structure, showing excellent isotropic characteristics; then, temperature-controlled heat treatment is carried out, specifically, the titanium-aluminum alloy is placed above the α single-phase region for a short time insulation, so that the titanium-aluminum alloy is transformed into the α phase while avoiding excessive grain growth, and then slowly cooled to the two-phase region so that it is fully transformed into a lamellar structure, followed by air cooling to avoid grain size growth and lamellar coarsening, and finally stress relief annealing and stabilization treatment are carried out above the target service temperature to obtain a stabilized structure; unlike the traditional process of casting Ta-containing titanium-aluminum alloy, which requires multiple steps or cyclic heat treatments to form a complex process of fine-grained near-lamellar structure, the heat treatment process proposed in the present invention, by precisely controlling the heat treatment parameters, significantly shortens the process cycle while achieving the refinement and uniform distribution of the lamellar structure, providing an efficient and reliable technical solution for the engineering preparation of the alloy system.

[0016] Furthermore, in the TiAl-(W, Mo, Ta, Nb) alloy powder of 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.

[0017] Specifically, when the Al content is between 47.5 and 49 at%, the hyperperitectic titanium-aluminum alloy exhibits exceptional room-temperature ductility and oxidation resistance. This compositional advantage effectively prevents the formation of brittle B2 and ω phases during long-term service at high temperatures, thereby ensuring the stability and reliability of the material structure.

[0018] It should be noted that by adding 3at.% to 6at.% of W, Mo, Ta, and Nb to hyperperitectic titanium-aluminum alloys, their high-temperature performance can be significantly improved, and the service temperature can be successfully increased to 850°C. However, the amount of alloying elements added needs to be precisely controlled. If the addition amount is too small, the improvement in high-temperature performance will be negligible, making it difficult to meet the service requirements above 850°C; conversely, if W, Mo, Ta, and Nb elements are added in excess, a series of negative effects will be triggered, such as increased composition segregation, resulting in uneven material properties; increased density, which brings a burden to practical applications; and a significant increase in cost, which is not conducive to large-scale engineering applications. More importantly, when the temperature exceeds 800°C, brittle B2 and ω harmful phases may be induced, which will seriously affect the material's stable service at higher temperatures and cannot meet the stringent requirements for high-temperature stability of materials in high-end fields such as aerospace, energy and power.

[0019] Furthermore, the atomic ratio of Nb:Ta:(W+Mo) is (2~4):(0.5~2):(0~2).

[0020] Specifically, adding a moderate amount of Nb (2at.%~4at.%) can significantly improve the high-temperature properties of TiAl alloys. At the same time, only a small amount of Ta (0.5at.%~2at.%) can be added to effectively change the interface state of the hyperperitectic titanium-aluminum alloy and significantly reduce the interface energy. This can promote the metastable structural transformation inside the titanium-aluminum alloy by precisely controlling the cooling rate from the single-phase region. By utilizing the specific orientation relationship between the γ phase and the α2 phase, grain refinement is successfully achieved, and a fine-grained near-lamellar structure is obtained. This structure ensures the excellent room-temperature plasticity and high-temperature properties of the titanium-aluminum alloy. However, Ta is more prone to segregation than Nb and is more expensive, so it is not advisable to add too much Ta.

[0021] Furthermore, the particle size of the TiAl-(W, Mo, Ta, Nb) alloy powder is 45 μm to 250 μm.

[0022] Furthermore, in the step 2, the temperature of the hot isostatic pressing is 10°C to 120°C below the α single-phase transition temperature, the pressure is 120MPa to 155MPa, and the time is 2h to 8h.

[0023] Specifically, hot isostatic pressing (HIP) of powders at 10°C to 120°C below the α-phase region effectively reduces the segregation of W, Mo, Ta, and Nb, resulting in a titanium-aluminum alloy with a uniform and fine initial microstructure and excellent isotropy. If the HIP forming temperature is too high, excessive grain growth may occur, adversely affecting the mechanical properties of the material. However, if the HIP forming temperature is too low, sufficient diffusion of W, Mo, Ta, and Nb may result in segregation and insufficient density. The HIP pressure should be between 120 MPa and 155 MPa to ensure that the HIPed part achieves a dense state. Too low a pressure will result in insufficient density, while too high a pressure will not only place higher demands on the HIP furnace but also pose a safety hazard. The HIP time should be controlled between 2 and 8 hours. If the time is too short, the part will not fully densify, while too long a time will result in grain growth.

[0024] Furthermore, the temperature-controlled heat treatment in step three is: first, keeping the temperature at 5°C to 30°C above the transformation temperature of the α single-phase region for 10min to 30min, then furnace cooling to the temperature of the α+γ two-phase region, and finally air cooling to room temperature.

[0025] Specifically, the temperature range of the α+γ two-phase region is between 1250°C and 1380°C, which is determined based on the addition amount of alloying elements. For cast titanium-aluminum alloys with similar compositions, obtaining similar fine, near-lamellar structures requires complex heat treatment regulation. The traditional heat treatment method is high-temperature, long-term homogenization + single-phase region heat preservation + two-phase region tempering + multiple cycles of heat treatment. In contrast, the present invention, based on the uniform and fine initial structure of powder metallurgy, is based on the characteristics of Ta that can reduce the interface energy of hyperperitectic titanium-aluminum alloy, and then produce metastable and lamellar structures during the slow cooling process in the single-phase region. This can greatly simplify the heat treatment process and is conducive to engineering applications.

[0026] It should be noted that short-term heat preservation at 5°C to 30°C above the transformation temperature of the α single-phase region can fully transform the titanium aluminum alloy into the α phase while avoiding excessive grain growth.

[0027] Furthermore, the furnace cooling time is 8 minutes to 12 minutes.

[0028] Specifically, during the temperature-controlled heat treatment process, when furnace cooling from the α single-phase region to the α+γ two-phase region, the γ laths will precipitate from the α phase, thereby forming a lamellar structure. It is more appropriate to control the furnace cooling time to 8min~12min. On the one hand, it can provide sufficient time for the precipitation of the γ laths to ensure the formation of sufficient lamellar structure. On the other hand, it can avoid the excessive growth of the lamellar clusters and the coarsening of the lamellars due to the long residence time in the two-phase region, thereby reducing the mechanical properties. The heat treatment process proposed in the present invention achieves the refinement and uniform distribution of the lamellar structure while significantly shortening the process cycle by precisely controlling the solid solution parameters, providing an efficient and reliable technical solution for the engineering preparation of the alloy system.

[0029] It should be noted that if the holding time of 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 t is in min and a is in mm.

[0030] Furthermore, in 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.

[0031] In addition, the present invention also discloses a powder metallurgy titanium-aluminum alloy product produced by a temperature control treatment method of powder hot isostatic pressing titanium-aluminum alloy, wherein the room temperature plasticity of the titanium-aluminum alloy product is 1.52% to 1.93%.

[0032] Finally, the present invention also discloses a titanium-aluminum alloy finished product produced by a temperature control treatment method of hot isostatic pressing of titanium-aluminum alloy powder, and the application of the titanium-aluminum alloy finished product in manufacturing titanium-aluminum alloy low-pressure turbine blades of engines.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] First, the present invention focuses on a hyperperitectic titanium-aluminum alloy system with an Al content of 47.5at.% to 49at.% and, on this basis, adds appropriate amounts of W, Mo, Ta, and Nb elements, which can bring three significant advantages: First, it can prevent the hyperperitectic TiAl alloy from generating brittle B2 and ω harmful phases during long-term service at high temperatures; second, it can effectively improve the high-temperature performance of the titanium-aluminum alloy, raising its service temperature to 850°C; third, compared with Nb-TiAl and high-Ta-TiAl alloys, the present invention avoids the problem of aggravated composition segregation caused by the large-scale addition of Nb and Ta by rationally controlling the amount of element addition, while effectively reducing production costs;

[0035] Second, the addition of Ta can change the interface state of the hyperperitectic titanium-aluminum alloy and reduce the interfacial energy. During the cooling process of the alloy from the single-phase region, the cooling rate can be precisely controlled to trigger the metastable microstructure transformation. By leveraging the special orientation relationship between the γ phase and the α2 phase, grain refinement is achieved, resulting in a fine-grained, near-lamellar structure, ensuring that the finished titanium-aluminum alloy has excellent room-temperature plasticity and high-temperature performance.

[0036] In summary, the processing method of the present invention solves the shortcomings of existing titanium aluminum alloys and their preparation processes in terms of composition design, process route, mechanical properties, and engineering operation convenience. It not only meets the high-temperature service requirements but also is convenient and controllable in engineering. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the invention.

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0039] Figure 1 Flow chart of the steps of the temperature control treatment method of the present invention;

[0040] Figure 2 This is a scanning electron microscope microstructure photograph of Example 1 of the present invention;

[0041] Figure 3 This is a scanning electron microscope microstructure photograph of Example 2 of the present invention;

[0042] Figure 4 This is a scanning electron microscope microstructure photograph of Example 3 of the present invention;

[0043] Figure 5 This is a scanning electron microscope microstructure photograph of Example 4 of the present invention;

[0044] Figure 6 This is a scanning electron microscope microstructure photograph of Example 5 of the present invention;

[0045] Figure 7 This is a scanning electron microscope micrograph of Example 1 after high-temperature heat exposure in the present invention;

[0046] Figure 8 This is a scanning electron microscope micrograph of Example 2 after high-temperature heat exposure in the present invention;

[0047] Figure 9 This is a scanning electron microscope micrograph of Example 3 after high-temperature heat exposure in the present invention;

[0048] Figure 10 This is a scanning electron microscope micrograph of Example 4 after high-temperature heat exposure in the present invention;

[0049] Figure 11 This is a scanning electron microscope micrograph of Example 5 after high-temperature heat exposure in the present invention. DETAILED DESCRIPTION

[0050] Here, exemplary embodiments will be described in detail, and the embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are only examples consistent with some aspects of the present invention described in detail in the appended claims.

[0051] In order to enable those skilled in the art to better understand the technical solutions of the present invention, the present invention is described in further detail below with reference to the accompanying drawings and embodiments.

[0052] 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

[0053] This embodiment provides a temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, which is specifically implemented according to the following steps:

[0054] Step 1, preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0055] 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.%;

[0056] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium-aluminum alloy intermediate billet;

[0057] During the hot isostatic pressing process, the package used is a cylindrical package with a diameter of 30 mm and a height of 80 mm. The powder is placed in the package and degassed and sealed before hot isostatic pressing and sintering. The package is then removed by machining to obtain titanium aluminum alloy. The package is made of carbon steel.

[0058] The hot isostatic pressing temperature is 1270°C (120°C below the α single-phase transition temperature), the pressure is 120 MPa, and the time is 2 h.

[0059] Step 3, heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0060] The temperature-controlled heat treatment is carried out at 1420°C (30°C above the transformation temperature of the α single-phase region) for 18 minutes, followed by furnace cooling at a rate of 10°C / min for 8 minutes to 1340°C (the temperature of the α+γ two-phase region), and finally air cooling to room temperature.

[0061] 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;

[0062] Specifically, stress relief annealing and stabilization treatment were both carried out at a temperature of 750°C for 6 h;

[0063] Step 5, remove the surface oxide layer of the third titanium-aluminum alloy intermediate blank to obtain a titanium-aluminum alloy finished product. The scanning electron microscope microstructure photo of the titanium-aluminum alloy finished product is as follows: Figure 2 As shown in the figure, all of them are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of the titanium aluminum alloy finished product after high temperature heat exposure is shown in the figure. Figure 7 As shown, it can be seen that the tissue is stable after long-term heat exposure at high temperature;

[0064] Among them, the room temperature tensile plasticity of the titanium aluminum alloy product is 1.52%, the tensile yield strength at 750℃ is 363MPa, and the tensile yield strength at 850℃ is 338MPa; the oxidation weight gain at 750℃ is 0.29mg / cm 2 , oxidation weight increase at 850℃ is 0.84mg / cm 2, the continuous life is 129h under 850℃ / 125MPa conditions, the continuous life is 256h under 750℃ / 250MPa conditions, and the continuous life is 385h under 650℃ / 350MPa conditions. Example 2

[0065] This embodiment provides a temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, which is specifically implemented according to the following steps:

[0066] Step 1, preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0067] 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.%;

[0068] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium-aluminum alloy intermediate billet;

[0069] During the hot isostatic pressing process, the package used is a rectangular package with a length of 20 mm, a width of 35 mm, and a height of 90 mm. The powder is placed in the package and degassed and sealed before hot isostatic pressing and sintering. The package is then removed by machining to obtain a titanium-aluminum alloy. The package is made of pure titanium.

[0070] The hot isostatic pressing temperature is 1315°C (70°C below the α single-phase transition temperature), the pressure is 138 MPa, and the time is 5 h.

[0071] Step 3, heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0072] The temperature-controlled heat treatment is carried out at 1403°C (18°C above the transformation temperature of the α single-phase region) for 10 minutes, followed by furnace cooling at a rate of 10°C / min for 12 minutes to 1298°C (the temperature of the α+γ two-phase region), and finally air cooling to room temperature.

[0073] 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;

[0074] Step 5, remove the surface oxide layer of the third titanium-aluminum alloy intermediate blank to obtain a titanium-aluminum alloy finished product. The scanning electron microscope microstructure photo of the titanium-aluminum alloy finished product is as follows: Figure 3As shown in the figure, all of them are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of the titanium aluminum alloy finished product after high temperature heat exposure is shown in the figure. Figure 8 As shown, it can be seen that the tissue is stable after long-term heat exposure at high temperature;

[0075] Among them, the room temperature tensile plasticity of the titanium aluminum alloy product is 1.93%, the tensile yield strength at 750℃ is 369MPa, and the tensile yield strength at 850℃ is 341MPa; the oxidation weight gain at 750℃ is not higher than 0.27mg / cm 2 , the oxidation weight gain at 850℃ is not higher than 0.89mg / cm 2 , the continuous life under 850℃ / 125MPa conditions is not less than 135h, the continuous life under 750℃ / 250MPa conditions is 263h, and the continuous life under 650℃ / 350MPa conditions is 385h without interruption. Example 3

[0076] This embodiment provides a temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, which is specifically implemented according to the following steps:

[0077] Step 1, preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0078] 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.%;

[0079] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium-aluminum alloy intermediate billet;

[0080] During the hot isostatic pressing process, the package used is a cylindrical package with a diameter of 35 mm and a height of 90 mm. The powder is loaded into the package and degassed and sealed before hot isostatic pressing and sintering. The package is then removed by machining to obtain a titanium-aluminum alloy. The package is made of pure titanium.

[0081] The hot isostatic pressing temperature is 1395°C (10°C below the α single-phase transition temperature), the pressure is 155 MPa, and the time is 8 h.

[0082] Step 3, heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0083] The temperature-controlled heat treatment is carried out by holding the temperature at 1410°C (5°C above the transformation temperature of the α single-phase region) for 30 minutes, then furnace cooling at a rate of 10°C / min for 10 minutes to 1310°C (the temperature of the α+γ two-phase region), and finally air cooling to room temperature.

[0084] 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;

[0085] Step 5, remove the surface oxide layer of the third titanium-aluminum alloy intermediate blank to obtain a titanium-aluminum alloy finished product. The scanning electron microscope microstructure photo of the titanium-aluminum alloy finished product is as follows: Figure 4 As shown in the figure, all of them are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of the titanium aluminum alloy finished product after high temperature heat exposure is shown in the figure. Figure 9 As shown, it can be seen that the tissue is stable after long-term heat exposure at high temperature;

[0086] Among them, the room temperature tensile plasticity of the titanium aluminum alloy product is 1.81%, the tensile yield strength at 750℃ is 377MPa, and the tensile yield strength at 850℃ is 345MPa; the oxidation weight gain at 750℃ is 0.26mg / cm 2 , the oxidation weight gain at 850℃ is not higher than 0.83mg / cm 2 , the continuous life is 141h under 850℃ / 125MPa conditions, the continuous life is 271h under 750℃ / 250MPa conditions, and the continuous life is 385h under 650℃ / 350MPa conditions. Example 4

[0087] This embodiment provides a temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, which is specifically implemented according to the following steps:

[0088] Step 1, preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0089] 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.%;

[0090] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium-aluminum alloy intermediate billet;

[0091] During the hot isostatic pressing process, the package used is a rectangular package with a length of 30 mm, a width of 30 mm, and a height of 90 mm. The powder is placed in the package and degassed and sealed before hot isostatic pressing and sintering. The package is then removed by machining to obtain a titanium-aluminum alloy. The package is made of pure titanium.

[0092] The hot isostatic pressing temperature is 1320°C (80°C below the α single-phase transition temperature), the pressure is 140 MPa, and the time is 5 h.

[0093] Step 3, heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0094] The temperature-controlled heat treatment is carried out at 1420°C (20°C above the transformation temperature of the α single-phase region) for 15 minutes, followed by furnace cooling at a rate of 10°C / min for 9 minutes to 1330°C (the temperature of the α+γ two-phase region), and finally air cooling to room temperature.

[0095] 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; the stress relief annealing and stabilization treatment are both performed at a temperature of 875° C. for 4 hours;

[0096] Step 5, remove the surface oxide layer of the third titanium-aluminum alloy intermediate blank to obtain a titanium-aluminum alloy finished product. The scanning electron microscope microstructure photo of the titanium-aluminum alloy finished product is as follows: Figure 5 As shown in the figure, all of them are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of the titanium aluminum alloy finished product after high temperature heat exposure is shown in the figure. Figure 10 As shown, it can be seen that the tissue is stable after long-term heat exposure at high temperature;

[0097] Among them, the room temperature tensile plasticity of the titanium aluminum alloy product is 1.72%, the tensile yield strength at 750℃ is 375MPa, and the tensile yield strength at 850℃ is 342MPa; the oxidation weight gain at 750℃ is not higher than 0.28mg / cm 2 , the oxidation weight gain at 850℃ is not higher than 0.86mg / cm 2 , the continuous life under 850℃ / 125MPa conditions is not less than 135h, the continuous life under 750℃ / 250MPa conditions is 263h, and the continuous life under 650℃ / 350MPa conditions is 385h without interruption. Example 5

[0098] This embodiment provides a temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder, which is specifically implemented according to the following steps:

[0099] Step 1, preparing TiAl-(W, Mo, Ta, Nb) alloy powder by plasma rotating electrode process;

[0100] 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.%;

[0101] Step 2: Hot isostatic pressing the TiAl-(W, Mo, Ta, Nb) alloy powder to obtain a first titanium-aluminum alloy intermediate billet;

[0102] During the hot isostatic pressing process, the sleeve used is a cylindrical sleeve with a diameter of 35 mm and a height of 90 mm. The powder is placed in the sleeve and degassed and sealed before hot isostatic pressing and sintering. The sleeve is then removed by machining to obtain a titanium-aluminum alloy. The sleeve is made of pure titanium.

[0103] The hot isostatic pressing temperature is 1335°C (70°C below the α single-phase transition temperature), the pressure is 138 MPa, and the time is 5 h.

[0104] Step 3, heat treating the first titanium-aluminum alloy intermediate billet to obtain a second titanium-aluminum alloy intermediate billet;

[0105] The temperature-controlled heat treatment is carried out at 1425°C (20°C above the transformation temperature of the α single-phase region) for 20 minutes, followed by furnace cooling at a rate of 10°C / min for 12 minutes to 1305°C (temperature of the α+γ two-phase region), and finally air cooling to room temperature.

[0106] 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; the stress relief annealing and stabilization treatment are both performed at a temperature of 850° C. for 4 hours;

[0107] Step 5, removing the surface oxide layer of the third titanium-aluminum alloy intermediate blank to obtain a titanium-aluminum alloy finished product. The scanning electron microscope microstructure photo of the titanium-aluminum alloy finished product is as follows: Figure 6 As shown in the figure, all of them are uniform and fine near-lamellar structures; the scanning electron microscope micrograph of the titanium aluminum alloy finished product after high temperature heat exposure is shown in the figure. Figure 11 As shown, it can be seen that the tissue is stable after long-term heat exposure at high temperature;

[0108] Among them, the room temperature tensile plasticity of the titanium aluminum alloy product is 1.85%, the tensile yield strength at 750℃ is 372MPa, and the tensile yield strength at 850℃ is 343MPa; the oxidation weight gain at 750℃ is not higher than 0.27mg / cm 2 , the oxidation weight gain at 850℃ is not higher than 0.85mg / cm 2, the service life under 850℃ / 125MPa conditions is not less than 140h, the service life under 750℃ / 250MPa conditions is 263h, and the service life under 650℃ / 350MPa conditions is 385h without interruption.

[0109] The performance of Examples 1-5 is shown in the following table:

[0110]

[0111] As can be seen from the table above, in Examples 1-5, the room temperature plasticity (room temperature tensile elongation) of the finished titanium aluminum alloy products is greater than 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 , 850℃ oxidation weight gain is not higher than 0.94mg / cm 2 , 850℃ / 125MPa lasting life is not less than 125h, 750℃ / 250MPa lasting life is not less than 250h, 650℃ / 350MPa lasting life is not less than 380h.

[0112] The foregoing description is intended only to provide specific embodiments of the present invention, which will enable those skilled in the art to understand and implement the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0113] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only 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: Prepare 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; The TiAl-(W, Mo, Ta, Nb) alloy powder of step 1 has an Al content of 47.5 at.% to 49 at.%, a total content of W, Mo, Ta, and Nb of 3 at.% to 6 at.%, and the balance is Ti; 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); In the step 2, the temperature of the hot isostatic pressing treatment is 10°C to 120°C below the α single-phase transition temperature, the pressure is 120MPa to 155MPa, and the time is 2h to 8h; The temperature-controlled heat treatment in step 3 is as follows: first, keep the temperature at 5°C to 30°C above the transition temperature of the α single-phase region for 10 to 30 minutes, then cool the furnace to the temperature of the α+γ two-phase region, and finally air cool to room temperature; 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.

2. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy powder 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.

3. The temperature control treatment method for hot isostatic pressing of titanium-aluminum alloy according to claim 1, characterized in that: The furnace cooling time is 8 minutes to 12 minutes.

4. A titanium-aluminum alloy product obtained by the temperature control treatment method according to any one of claims 1 to 3, characterized in that: The room temperature plasticity of the titanium aluminum alloy product is 1.52% to 1.93%.

5. Use of a titanium-aluminum alloy product obtained by the temperature control treatment method according to any one of claims 1 to 3 in the manufacture of titanium-aluminum alloy low-pressure turbine blades for engines.

Images