Copper-doped titanium-aluminum alloy and preparation method thereof

Abstract

The invention belongs to the technical field of powder metallurgy, and discloses a copper-doped titanium-aluminum alloy and a preparation method thereof. The preparation method comprises the following steps: mixing titanium-aluminum alloy powder with elemental copper powder to prepare mixed metal powder; then adding a binder, and mixing to prepare a feed; and then the feed is sequentially subjected to injection molding, degreasing and pressureless sintering, and then the copper-doped titanium-aluminum alloy is prepared. According to the atomic percent, the proportion of the elementary substance copper powder is 0.5 at%-6.0 at%; the pressureless sintering temperature is equal to or lower than the melting point of the mixed metal powder. The titanium-aluminum alloy is doped with the copper element, through regulation and control of the copper element, the densification temperature of pressureless sintering of the titanium-aluminum alloy can be effectively reduced, deformation of a sintered product is avoided, the aperture of pores in the titanium-aluminum alloy is reduced, and the quality of the titanium-aluminum alloy is improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of powder metallurgy, and particularly relates to a copper-doped titanium-aluminum alloy and a preparation method thereof. BACKGROUND

[0002] Titanium-aluminum alloy is widely used in aerospace, new energy vehicles and other fields as a lightweight high-temperature structural material. Its research and development has gone through the stages of basic research, boom, rise and specific application. At present, it is breaking through to the frontiers of super-elastic alloy and high-heat-resistant alloy. As a near-net forming process, powder injection molding technology realizes the mass production of high-complexity parts at low cost, and continues to innovate in the fields of binder system, numerical simulation technology and micro-forming. Research shows that the two technologies show a trend of coordinated development, and titanium-aluminum powder injection molding will become a key direction in the future.

[0003] Sintering aids, as key additives to improve sintering efficiency and product performance, have applications in material science, process optimization, and industrial demand. With the development of powder metallurgy products towards high performance, complex shape and low cost, the research and application of sintering aids has become an important topic in this field. By analyzing existing research results and patent technologies, this paper reveals how sintering aids solve key bottleneck problems in powder metallurgy and looks forward to its future development trend. Common sintering aids are used in ceramics such as high-thermal-conductivity silicon nitride ceramics, usually multiple metal oxides, and traditional ones such as MgO, Y2O3, Al2O3 for Al2O3, B4C.

[0004] The pressureless sintering after metal injection molding process (MIM) is a core process that makes the porous metal powder body after debinding shrink freely under the surface tension and chemical driving force without external pressure, eliminates pores, and finally forms a dense metal part by precisely controlling temperature, atmosphere and holding time. Since the pressureless sintering process is a process that does not apply external force, the green body shrinks freely under the surface tension and chemical driving force without deformation or damage due to external pressure, perfectly preserving the complex geometric features of injection molding (such as micro-holes, threads, irregular curved surfaces, etc.), and pressureless sintering is almost applicable to all metals and alloys that can be made into fine spherical powder, such as titanium-aluminum alloy. However, due to the high sintering temperature of titanium-aluminum alloy, and the difficulties in shrinkage control, deformation, and process sensitivity during pressureless sintering, the sintered sample will deform after long-time holding at high temperature, and more and larger pores that cannot be eliminated will be produced, resulting in low density. SUMMARY

[0005] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application provides a copper-doped titanium-aluminum alloy and a preparation method thereof. The present application dopes copper elements in the titanium-aluminum alloy, and through the regulation of the copper elements, the temperature for the densification of the titanium-aluminum alloy by pressureless sintering can be effectively reduced, the deformation of the sintered product can be avoided, and the pore size of the internal pores of the titanium-aluminum alloy can be reduced, thereby improving the quality of the titanium-aluminum alloy.

[0006] The present application provides a preparation method of a copper-doped titanium-aluminum alloy.

[0007] Specifically, the present application provides a preparation method of a copper-doped titanium-aluminum alloy, which comprises the following steps: The titanium-aluminum alloy powder and the elemental copper powder are mixed to obtain a mixed metal powder, a binder is then added, and after mixing and kneading, a feedstock is prepared. After injection molding, debinding, and pressureless sintering of the feedstock, a copper-doped titanium-aluminum alloy is obtained. The proportion of the elemental copper powder in the mixed metal powder is 0.5at%-6.0at% by atomic percentage. The temperature of the pressureless sintering is equal to or lower than the melting point of the mixed metal powder.

[0008] In some embodiments of the present application, the mixing process is ball milling of the titanium-aluminum alloy powder and the elemental copper powder. In the ball milling process, the diameter of the grinding balls is 3-6mm, the ball-to-material ratio is (2-5):1, the rotation speed is 180-250r / min, and the ball milling time is 0.5-2h.

[0009] In some embodiments of the present application, the mixed metal powder comprises 45.0at%-49.0at% Al, 6.0at%-8.0at% Nb, 0.1at%-0.5at% W, 0.5at%-6.0at% Cu, and Ti as the balance by atomic percentage. Preferably, the mixed metal powder comprises 47.0at%-48.0at% Al, 6.5at%-7.0at% Nb, 0.1at%-0.3at% W, 4.5at%-5.5at% Cu, and Ti as the balance by atomic percentage. For example, the mixed metal powder comprises 47.5at% Al, 6.8at% Nb, 0.2at% W, 5.0at% Cu, and Ti as the balance.

[0010] In some embodiments of the present application, the proportion of the elemental copper powder in the mixed metal powder is 4.0at%-6.0at% by atomic percentage, and the temperature of the pressureless sintering is 50-100℃ lower than the melting point of the mixed metal powder. Preferably, the proportion of the elemental copper powder in the mixed metal powder is 4.5at%-5.5at% by atomic percentage, and the temperature of the pressureless sintering is 70-100℃ lower than the melting point of the mixed metal powder.

[0011] In some embodiments of the present application, the proportion of elemental copper powder in the mixed metal powder is 4.0at%-6.0at% by atomic percentage, and the pressureless sintering temperature is 1235-1285℃; preferably, the proportion of elemental copper powder in the mixed metal powder is 4.5at%-5.5at% by atomic percentage, and the pressureless sintering temperature is 1235-1265℃.

[0012] In some embodiments of the present application, the pressureless sintering process is to heat to the pressureless sintering temperature at a heating rate of 1.5-3℃ / min and to keep the temperature for 1-3 hours.

[0013] In some embodiments of the present application, the binder is a polyformaldehyde-based binder. Preferably, the polyformaldehyde-based binder comprises 75%-90% polyoxymethylene (POM), 3%-10% high-density polyethylene (HDPE), 3%-8% ethylene-vinyl acetate copolymer (EVA) and 3%-8% stearic acid. Preferably, the polyformaldehyde-based binder comprises 80%-89% polyoxymethylene, 5%-10% high-density polyethylene, 3%-8% ethylene-vinyl acetate copolymer and 3%-8% stearic acid. For example, the polyformaldehyde-based binder comprises 83% polyoxymethylene, 7% high-density polyethylene, 5% ethylene-vinyl acetate copolymer and 5% stearic acid.

[0014] In some embodiments of the present application, the mixing process is to keep the temperature at 180℃-220℃ for 10-30min, then to perform mixing by gradient cooling, and finally to break at 130-160℃.

[0015] In some embodiments of the present application, the injection molding temperature is 180-200℃, the pressure is 110-130Mpa, the speed is 40-65mm / s, the holding pressure is 75-90Mpa, and the mold temperature is 110-130℃. For example, the injection molding temperature is 195℃, the pressure is 125Mpa, the speed is 55mm / s, the holding pressure is 85Mpa, and the mold temperature is 120℃.

[0016] In some embodiments of the present application, the debinding process comprises oxalic acid catalytic debinding and thermal debinding. The oxalic acid catalytic debinding process is to add oxalic acid in stages at 120-140℃ and to debind for 15-25h. The thermal debinding process is to heat to 150-200℃, 300-380℃ and 400-450℃ in sequence, keep the temperature for 15-45min, 15-45min and 45-90min, respectively. The combination of oxalic acid catalytic debinding and thermal debinding and the control of specific process parameters can effectively remove the binder while ensuring the regularity of the injection blank shape.

[0017] The application also provides a copper-doped titanium-aluminum alloy.

[0018] Specifically, the copper-doped titanium-aluminum alloy is prepared by the preparation method, and has a density greater than 93.0%, an average pore size less than 50 μm, and a hardness greater than 41 HRC.

[0019] Preferably, the copper-doped titanium-aluminum alloy has a density greater than 95.0%, an average pore size less than 30 μm, and a hardness greater than 42 HRC.

[0020] Copper is a stable low-melting-point metal with a melting point of 1084℃, and can reach a liquid phase to clean the surface of copper liquid phase particles and preliminarily rearrange before the sintering of the titanium-aluminum alloy is carried out to the middle stage, and then the matrix begins to activate sintering. If the melting point of the selected sintering aid is too low, the liquid phase will be generated in advance, which may cause the green strength to decrease. It is found in the application that when the proportion of doped copper is 0.5at%-6.0at%, the melting point of the mixed metal powder gradually decreases with the increase of the doping amount, thereby reducing the sintering temperature, and the pore size also shows a significant downward trend. Especially when the proportion of doped copper element is 4.5at%-5.5at%, high-quality pressureless sintering can be realized at a temperature lower than the melting point of the mixed metal powder by 50-100℃, which can greatly reduce the sintering temperature while increasing the density of the titanium-aluminum alloy to more than 95.0% and reducing the average pore size to less than 30 μm. In the process of high-temperature sintering densification, on the one hand, the presence of copper can reduce the concentration of trace elements in the titanium-aluminum alloy, thereby forming a continuous protective aluminum oxide layer on the surface; on the other hand, copper can also promote pore spheroidization, reduce pore size, and improve pore distribution uniformity.

[0021] Compared with the prior art, the application has the following beneficial effects: (1) The application dopes copper element in the titanium-aluminum alloy, and through the regulation of the copper element, the temperature for the pressureless sintering densification of the titanium-aluminum alloy can be effectively reduced, the deformation of the sintered product can be avoided, and the pore size of the internal pores of the titanium-aluminum alloy can be reduced, thereby improving the quality of the titanium-aluminum alloy. Especially when the proportion of copper element is 4.5at%-5.5at%, the sintering temperature can be greatly reduced, and the density can be increased to more than 95.0% and the average pore size can be reduced to less than 30 μm.

[0022] (2) Through the synergistic effect of the regulation of the copper content and the sintering temperature, the liquid phase sintering effect generated by copper is utilized to significantly promote the densification of the titanium-aluminum alloy without external pressure, and the application is particularly suitable for preparing high-performance and complex-shaped titanium-aluminum alloy parts by the powder injection molding process. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 FIG. 2 is a macroscopic morphology diagram of the sintered product of the comparative example 1 of the application. Figure 2 This is a microscopic morphology diagram of the sintered product in Comparative Example 1 of the present invention; Figure 3 This is a macroscopic morphology diagram of the sintered product of Example 1 of the present invention; Figure 4 This is a size comparison diagram of the sintered sample (A), degreased sample (B), and injection sample (C) in Example 1 of the present invention; Figure 5 This is a microscopic morphology diagram of the sintered product in Example 4 of the present invention. Detailed Implementation

[0024] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0025] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0026] Comparative Example 1 (1) Based on atomic percentage, with Al 47.5%, Nb 6.8%, W 0.2%, Cu 0%, and the balance Ti, a composition Ti-47.5Al-6.8Nb-0.2W-0%Cu (denoted as TiAl-0%Cu) was added. The above metal powder was weighed and premixed to obtain a premixed powder. The metal powder was then subjected to composite treatment using a planetary ball mill with a grinding ball diameter of 5 mm, a ball-to-material ratio of 3:1, a rotation speed of 210 r / min, and a ball milling time of 1 h to obtain TiAl-0%Cu mixed metal powder (the melting point was determined to be 1450℃ by differential scanning calorimetry (DSC)). It should be noted that in actual operation, TiAl pre-alloy powder containing Al, Nb, W, and Ti was prepared first, and then Cu element (elemental Cu powder) was added or not added according to the situation of each embodiment and comparative example. The raw material parameters and sintering parameters of TiAl pre-alloy powder and elemental Cu powder in Examples 1-4 and Comparative Example 1 are shown in Table 1.

[0027] (2) The mixed metal powder and polyaldehyde-based binder (83% POM + 7% HDPE + 5% EVA + 5% SA) are added to the internal mixer at a loading of 65%. Then, the mixture is kept at 220°C for 15 minutes, and then cooled and mixed at 200°C, 180°C and 160°C. The mixture is then crushed at around 150°C to form a uniform feed.

[0028] (3) The feed material is injected into the injection molding machine under the main process parameters of injection temperature of 195℃, injection pressure of 125Mpa, injection speed of 55mm / s, holding pressure of 85Mpa and mold temperature of 120℃ to obtain a defect-free injection blank.

[0029] (4) The injection blank was degreased by catalytic treatment in an oxalic acid environment at 130°C using three different oxalic acid flow rates and different nitrogen flow rates before and after degreasing. The degreasing time was 1180 min. After degreasing, a degreased blank with a regular shape and a degreasing rate of 12.6% was obtained. Then, the temperature was gradually increased to 180°C, 350°C, and 450°C at a heating rate of 2.5°C / min and held for 30 min, 30 min, and 60 min respectively for thermal degreasing to remove all residual binder. The temperature was then increased to 740°C at 3°C / min and held for 1 h, followed by a heating rate of 2°C / min to 1000°C. At this point, the temperature was close to the melting point of copper, and the alloy was about to enter the initial sintering stage. Finally, the temperature was increased to 1450°C at a rate of 2.5°C / min and held for 2 h, and then cooled to room temperature at 5°C / min.

[0030] Microscopic morphology of sintered products: The pores are relatively well closed, but the average pore size is relatively large (microscopic morphology such as...). Figure 2 As shown, Figure 2 In the middle, (a1) and (a2) are magnified 50 times; Figure 2 (b1) and (b2) are magnified 100 times: Figure 2 (c1 and c2 are magnified 200 times). Due to the high temperature, the grain size is large, and the sintered part exhibits bending and adhesion to the ceramic plate (e.g. Figure 1 (As shown). The density is 93.5%.

[0031] Example 1 (1) Based on atomic percentage, with Al 47.5%, Nb 6.8%, W 0.2%, Cu 1%, and the balance Ti, the composition Ti-47.5Al-6.8Nb-0.2W-1%Cu (denoted as TiAl-1%Cu) was added. The above metal powder was weighed and premixed to obtain premixed powder. The metal powder was then composited using a planetary ball mill with a grinding ball diameter of 5 mm, a ball-to-material ratio of 3:1, a rotation speed of 210 r / min, and a ball milling time of 1 h to obtain the TiAl-1%Cu mixed metal powder (the melting point was determined to be 1395 °C by differential scanning calorimetry (DSC)).

[0032] (2) The mixed metal powder and polyaldehyde-based binder (83% POM + 7% HDPE + 5% EVA + 5% SA) are added to the internal mixer at a loading of 65%. Then, the mixture is first kept at 220°C and then gradually cooled down for mixing. The mixture is then crushed at around 150°C to form a uniform feed.

[0033] (3) The material is injected into the injection molding machine under the main process parameters of injection temperature 195℃, injection pressure 125Mpa, injection speed 55mm / s, holding pressure 85Mpa, and mold temperature 120℃ to obtain the following result. Figure 4 The defect-free injection preform shown in C.

[0034] (4) The injection preform was degreased by catalytic treatment in an oxalic acid environment at 130°C using three different oxalic acid flow rates and different nitrogen flow rates before and after degreasing. The degreasing time was 1180 min. A regularly shaped degreased preform with a degreasing rate of 12.6% was obtained. Then, the preform was thermally degreased by gradient heating at a rate of 2.5°C / min to 180°C, 350°C, and 450°C, and held at these temperatures for 30 min, 30 min, and 60 min respectively, to remove all remaining binder. The resulting degreased sample is shown below. Figure 4 As shown in Figure B. The temperature is then increased to 740℃ at a rate of 3℃ / min and held for 1 hour. Next, the temperature is increased to 1000℃ at a rate of 2℃ / min. At this point, the temperature is close to the melting point of copper, and the alloy is about to enter the early stage of sintering. Finally, the temperature is increased to 1395℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min, resulting in the alloy shown in Figure B. Figure 3 The sintered product shown.

[0035] The dimensions of sintered samples were statistically analyzed. The sintered sample (A), degreased sample (B), and injection-molded sample (C) are shown below. Figure 4 As shown. The tensile length of the injection sample and the degreased sample is approximately 94 mm, and the size of the sintered sample is approximately 79 mm. The shrinkage rate reaches 16%, and no deformation occurs after pressureless sintering. The shape consistency of the sintered sample with the degreased sample and the injection sample is high.

[0036] Microscopic morphology of the sintered product was examined: the pores were relatively well closed, and the pore size was reduced compared to Comparative Example 1. Due to sintering at a lower temperature, the grains were uniform and lustrous, with a density of 93.3%.

[0037] Example 2 The difference between this embodiment and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-3%Cu (denoted as TiAl-3%Cu), consisting of 47.5% Al, 6.8% Nb, 0.2% W, 3% Cu, and the balance Ti. The melting point of the TiAl-3%Cu mixed metal powder was determined to be 1360℃ by differential scanning calorimetry (DSC). During the sintering process, the temperature was raised to 1360℃ at a rate of 2.5℃ / min and held for 2 hours, followed by cooling to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0038] The sintered product prepared in this embodiment is the same as that in Example 1, and will not undergo deformation. The sintered sample has a high degree of shape consistency with the degreased sample and the injection sample.

[0039] The microstructure of the sintered product was examined: the pores were relatively well closed and uniformly distributed, the pore size was further reduced compared to Example 1, and the density was 93.1%.

[0040] Example 3 The difference between this embodiment and Example 1 is that, based on atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-5%Cu (denoted as TiAl-5%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 5%, and the balance Ti. The melting point of the TiAl-5%Cu mixed metal powder was determined to be 1335℃ by differential scanning calorimetry (DSC). During the sintering process, the temperature was raised to 1335℃ at a rate of 2.5℃ / min and held for 2 hours, followed by cooling to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0041] The sintered product prepared in this embodiment is the same as that in Example 1, and will not undergo deformation. The sintered sample has a high degree of shape consistency with the degreased sample and the injection sample.

[0042] Microscopic morphology of sintered products: The pore size distribution is uniform and the pore size is small. Due to the low temperature of sintering, the product has no defects in shape and the density is 93.4%.

[0043] Example 4 The difference between this embodiment and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-5%Cu (denoted as TiAl-5%Cu), consisting of 47.5% Al, 6.8% Nb, 0.2% W, 5% Cu, and the balance Ti. The melting point of the TiAl-5%Cu mixed metal powder was determined to be 1335℃ by differential scanning calorimetry (DSC). During the sintering process, the temperature was raised to 1250℃ at a rate of 2.5℃ / min and held for 2 hours, followed by cooling to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0044] The sintered product prepared in this embodiment is the same as that in Example 1, and will not undergo deformation. The sintered sample has a high degree of shape consistency with the degreased sample and the injection sample.

[0045] The microstructure of the sintered product was examined: the pore size was significantly reduced, macropores decreased at lower temperatures, and the pore distribution was uniform, with a density of 96.3%. Compared to Example 3, the addition of 5% copper effectively promoted densification during the sintering process, suppressed the formation of macropores, refined the grain structure, and improved the overall uniformity and mechanical properties of the material. Figure 5 This is a microscopic morphology image of the sintered product in Example 4 of the present invention. Figure 5 In the middle, (a1) and (a2) are magnified 50 times; Figure 5 (b1) and (b2) are magnified 100 times: Figure 5 In the diagram, (c1) and (c2) represent magnification of 200 times. Figure 5 It can be seen that the pore shape is complete and highly circular, small and uniformly distributed, and the pore size is significantly reduced.

[0046] Table 1. Raw material parameters and sintering parameters of TiAl-Cu mixed metal powder in Examples 1-4

[0047] Comparative Example 2 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-0%Cu (denoted as TiAl-0%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 0%, and the balance being Ti. During sintering, the temperature was raised to 1395℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0048] Comparative Example 3 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-3%Cu (denoted as TiAl-3%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 3%, and the balance being Ti. During sintering, the temperature was raised to 1395℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0049] Comparative Example 4 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-5%Cu (denoted as TiAl-5%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 5%, and the balance being Ti. During sintering, the temperature was raised to 1395℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0050] Comparative Example 5 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-0%Cu (denoted as TiAl-0%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 0%, and the balance being Ti. During sintering, the temperature was raised to 1360℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0051] Comparative Example 6 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-1%Cu (denoted as TiAl-1%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 1%, and the balance being Ti. During sintering, the temperature was raised to 1360℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0052] Comparative Example 7 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-5%Cu (denoted as TiAl-5%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 5%, and the balance being Ti. During sintering, the temperature was raised to 1360℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0053] Comparative Example 8 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-1%Cu (denoted as TiAl-1%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 1%, and the balance being Ti. During sintering, the temperature was raised to 1335℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0054] Comparative Example 9 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-3%Cu (denoted as TiAl-3%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 3%, and the balance being Ti. During sintering, the temperature was raised to 1335℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0055] Comparative Example 10 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-1%Cu (denoted as TiAl-1%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 1%, and the balance being Ti. During sintering, the temperature was raised to 1250℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0056] Comparative Example 11 The difference between this comparative example and Example 1 is that, calculated by atomic percentage, the composition is Ti-47.5Al-6.8Nb-0.2W-3%Cu (denoted as TiAl-3%Cu), with Al 47.5%, Nb 6.8%, W 0.2%, Cu 3%, and the balance being Ti. During sintering, the temperature was raised to 1250℃ at a rate of 2.5℃ / min and held for 2 hours, then cooled to room temperature at a rate of 5℃ / min. The remaining preparation process was the same as in Example 1.

[0057] Product performance testing Performance tests were conducted on the sintered products (titanium-aluminum alloy) of Examples 1-4 and Comparative Examples 1-11. The tests included density (%), average pore size (μm), and hardness (HRC). Density (%) was calculated by comparing the actual density of the sintered samples with the theoretical density values ​​for different additive amounts. Multiple pore size images (50 times the pore size) were imported into ImageJ software to measure the pore size, and the average value was taken to obtain the average pore size (μm). After grinding a sintered sample to a certain size, the Rockwell hardness was measured using a hardness tester. Each group underwent 20 measurements, and the average value was taken to obtain the Rockwell hardness (HRC). The test results are shown in Table 2.

[0058] Table 2 Comparison of the final properties of sintered products from Examples 1-4 and Comparative Examples 1-11

[0059] Testing revealed that the products prepared in Examples 1-4 and Comparative Example 1 at suitable temperatures exhibited significantly different densities compared to Comparative Examples 2-11. The densities of Examples 1-4 were all above 93%, and after the addition of copper, the pore size showed a clear decreasing trend with decreasing sintering temperature. In particular, Example 4, by adding an appropriate amount of copper and lowering the sintering temperature to a suitable range, achieved TiAl-5%Cu with higher density, harderness, and smaller average pore size, demonstrating superior performance.

[0060] Examples 1-4 all involve alloys with added copper. Compared to Comparative Example 1, their sintering temperatures are significantly lower. This is because the introduced copper acts as a sintering aid, generating a liquid phase at low temperatures, forming a transient liquid-phase sintering system. During the densification process, the liquid melt exerts capillary forces on the TiAl powder particles. These capillary forces are equivalent to external pressure. Combined with the multiple diffusion channels formed between the solid TiAl powder and the liquid Cu melt under the influence of the concentration gradient, this accelerates the diffusion and migration of materials, promotes the formation of sintering necks, and drives the densification sintering process of the part. Furthermore, when the copper content is relatively high (4.5%-6.0%), local melting and wetting of TiAl further promotes densification.

[0061] Examples 1 and Comparative Examples 1-4 are the results of sintering at corresponding temperatures with different amounts of copper. Comparative Example 2 failed to complete sintering without adding copper, while Comparative Examples 3-4 had melting points lower than the temperature used in Example 1, resulting in melting during the sintering process and poor final performance.

[0062] Examples 2 and Comparative Examples 5-7, and Examples 3 and Comparative Examples 8-9 further verified the above results. The melting point of the alloy decreased significantly with the increase of copper addition, and the examples were able to achieve the best effect at this temperature. In the comparative examples, when the sintering temperature was significantly higher or lower than the alloy melting point, incomplete sintering or over-sintering would occur, leading to melting.

[0063] Example 4 further reduced the temperature. Compared with Comparative Examples 10-11, it can be seen that when the Cu addition amount is 5%, the TiAl-5%Cu alloy obtained after sintering at this temperature has a density of 96.3%, while the average pore size is further reduced and the hardness is further improved.

[0064] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a copper-doped titanium-aluminum alloy, characterized in that, Includes the following steps: Titanium-aluminum alloy powder is mixed with elemental copper powder to obtain mixed metal powder; then a binder is added and the mixture is kneaded to form a feedstock; the feedstock is then subjected to injection molding, degreasing and pressureless sintering in sequence to obtain copper-doped titanium-aluminum alloy. On an atomic percentage basis, the elemental copper powder accounts for 0.5 at% to 6.0 at% of the mixed metal powder. The pressureless sintering temperature is equal to or lower than the melting point of the mixed metal powder.

2. The preparation method according to claim 1, characterized in that, The mixed metal powder comprises, by atomic percentage, 45.0 at%-49.0 at% Al, 6.0 at%-8.0 at% Nb, 0.1 at%-0.5 at% W, 0.5 at%-6.0 at% Cu, and Ti as the balance.

3. The preparation method according to claim 1 or 2, characterized in that, The proportion of elemental copper powder in the mixed metal powder is 4.0 at%-6.0 at% by atomic percentage, and the pressureless sintering temperature is 50-100°C lower than the melting point of the mixed metal powder.

4. The preparation method according to claim 3, characterized in that, The proportion of elemental copper powder in the mixed metal powder is 4.0 at%-6.0 at%, and the pressureless sintering temperature is 1235-1285℃.

5. The preparation method according to claim 4, characterized in that, The pressureless sintering process involves heating to the pressureless sintering temperature at a heating rate of 1.5-3℃ / min and holding at that temperature for 1-3 hours.

6. The preparation method according to claim 1 or 2, characterized in that, The adhesive is a polyaldehyde-based adhesive; the polyaldehyde-based adhesive includes 75%-90% polyoxymethylene, 3%-10% high-density polyethylene, 3%-8% ethylene-vinyl acetate copolymer and 3%-8% stearic acid.

7. The preparation method according to claim 1 or 2, characterized in that, The injection molding temperature is 180-200℃, the pressure is 110-130Mpa, the speed is 40-65mm / s, the holding pressure is 75-90Mpa, and the mold temperature is 110-130℃.

8. The preparation method according to claim 1 or 2, characterized in that, The degreasing process includes oxalic acid-catalyzed degreasing and thermal degreasing. The oxalic acid-catalyzed degreasing process is as follows: oxalic acid is added in stages at 120-140℃ for 15-25 hours. The thermal degreasing process is as follows: the temperature is raised to 150-200℃ and held for 15-45 minutes, then to 300-380℃ and held for 15-45 minutes, and finally to 400-450℃ and held for 45-90 minutes.

9. A copper-doped titanium-aluminum alloy, characterized in that, The copper-doped titanium-aluminum alloy prepared by any one of claims 1-8 has a density greater than 93.0%, an average pore size less than 50 μm, and a hardness greater than 41 HRC.

10. The copper-doped titanium-aluminum alloy according to claim 9, characterized in that, The copper-doped titanium-aluminum alloy has a density greater than 95.0%, an average pore size less than 30 μm, and a hardness greater than 42 HRC.

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