Diffusion bonding interface regulation and control method for guiding alpha2 phase to evolve from hindering type to collaborative type

Abstract

The invention discloses a diffusion bonding interface regulation and control method for guiding an alpha2 phase to evolve from a hindering type to a synergetic type, which comprises the following steps of: carrying out chemical mechanical polishing on a to-be-welded surface of a TiAl material to obtain a to-be-welded sample without a damaged layer on the surface of the to-be-welded surface; and diffusion welding is conducted on the two to-be-welded samples. According to the method, the to-be-welded interface is subjected to chemical mechanical polishing, the to-be-welded sample without a damaged layer on the surface is obtained, and the random precipitation behavior of the alpha2 phase in the diffusion bonding process is effectively avoided. According to the method, epitaxial growth of the alpha2 phase at the interface along the orientation of the base material is achieved, crystallographic continuity of the epitaxial alpha2 phase and the base material is kept, the epitaxial alpha2 phase and the gamma sheet layer can slide cooperatively in the deformation process, and the deformation coordination and the mechanical property of the welding interface are remarkably improved. The method is simple in process, high in applicability and particularly suitable for manufacturing and repairing of complex structures of high-end light high-temperature materials such as PST-TiAl single crystals and the like, and has application value in the field of aerospace and national defense equipment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of materials, and particularly relates to a diffusion bonding interface regulation method for guiding the evolution of an alpha2 phase from a barrier type to a synergistic type. BACKGROUND

[0002] Titanium aluminum alloy (TiAl) is an ideal lightweight high-temperature structural material in the fields of aerospace, automobile engines and energy due to its excellent high-temperature performance, low density and excellent oxidation resistance. Compared with traditional nickel-based high-temperature alloys, the density of TiAl alloy is significantly reduced to 3.9 to 4.1 g / cm 3 , which is about half of that of nickel-based high-temperature alloys (8.0 to 9.0 g / cm 3 ). The latest research and development of Ti45Al8Nb (atomic percentage) polycrystalline twin TiAl single crystal (PST-TiAl) in China has improved the room temperature tensile plasticity from <2% to about 7%, doubled the high-temperature strength from room temperature to 900℃, and increased the 900℃ creep resistance by nearly 100 times.

[0003] In high-end equipment manufacturing, TiAl single crystal is particularly suitable for manufacturing key structural components such as gas turbine turbine blades, compressor blade roots, guide vanes and nozzle liners with working temperatures exceeding 750℃, which can achieve significant weight reduction and thrust improvement, and has strategic significance for engine performance improvement, aircraft range expansion and fuel efficiency optimization. In addition, the wide application of PST-TiAl single crystal will also promote the development of high-performance turbomachinery, heat-resistant structures and hot-end functional components, and has an important driving effect on national defense modernization and advanced power system self-controllability, realizing a leap-forward development of high-end national defense equipment with faster performance response, higher mobility, longer range and stronger survival.

[0004] However, in actual engineering applications, PST-TiAl single crystal often needs to be connected through high-quality welding connection technology due to size, geometric morphology or material combination restrictions to build complex components or achieve multi-material collaborative service. Diffusion bonding, as a typical solid-phase welding technology, can avoid problems such as grain coarsening and element segregation in fusion welding, and is particularly suitable for connecting heat-sensitive materials such as TiAl single crystal, and has an irreplaceable position in high-end manufacturing. Research and optimization of the welding process of PST-TiAl single crystal are of great significance to improve its engineering application potential.

[0005] It is well known that one of the key problems in the diffusion bonding process of TiAl alloy is the precipitation behavior of α2 phase at the joint interface. The phase often precipitates randomly without specific crystallographic orientation, which leads to the phase acting as an obstacle for dislocation slip in the service behavior, and thus significantly weakens the deformation ability and overall ductility of the joint. The α2 phase is generally considered to be a brittle phase, and its formation and improper orientation are widely regarded as one of the main reasons for the early failure of TiAl alloy joints. Therefore, how to effectively regulate the precipitation behavior of the α2 phase during the diffusion bonding process, especially its crystallographic orientation, so as to change it from the traditional "obstacle phase" to the "synergistic phase" that can coordinate the deformation of the base material, has become a key scientific problem and engineering challenge to improve the comprehensive performance of TiAl alloy connected joints. SUMMARY

[0006] In view of the above technical problems, the present application provides a diffusion bonding interface regulation method for guiding the evolution of α2 phase from obstacle type to synergistic type. Based on the basic understanding that α2 phase promotes crack initiation by obstructing dislocation slip, the present application effectively suppresses the formation of brittle α2 phase that obstructs slip and promotes the generation of synergistic α2 phase that can coordinate the deformation of the base material during the welding process of TiAl alloy by adjusting the surface state (damage layer), induces the transformation of α2 phase at the diffusion bonding interface of TiAl alloy from "obstacle type" structure to "synergistic type" structure, that is, realizes the construction of epitaxial growth α2 phase, and improves the deformation coordination and comprehensive mechanical properties of the joint.

[0007] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0008] On the one hand, the present application provides a diffusion bonding interface regulation method for guiding the evolution of α2 phase from obstacle type to synergistic type, comprising the following steps:

[0009] (1) chemically and mechanically polishing the surface to be welded of TiAl material to obtain a sample with no damage layer on the surface to be welded;

[0010] (2) diffusion welding two pieces of the sample to be welded.

[0011] In the technical scheme of the present application, the damage layer is a damage layer of micro-defect region that destroys the integrity and crystallographic order of single crystal formed on the surface and subsurface of the material during mechanical processing (such as sandpaper polishing, ordinary cutting and turning) or previous treatment (such as wire electrical discharge machining), and the damage layer can be avoided or removed by chemical mechanical polishing.

[0012] As a preferred embodiment, the vacuum degree of the diffusion welding is ≤10 -4 Pa; the temperature of the diffusion welding is 1000-1300℃; and the pressure of the diffusion welding is 10-50MPa.

[0013] As a preferred embodiment, the holding time of the diffusion welding is 1-10 h.

[0014] As a preferred embodiment, the heating rate of the diffusion welding is 5-20℃ / min.

[0015] As a preferred embodiment, the diffusion welding further comprises a process of furnace cooling to room temperature.

[0016] As a preferred embodiment, the TiAl material is a TiA alloy, selected from any one of full lamellar TiAl polycrystal and poly lamella twin TiAl (PST-TiAl) single crystal;

[0017] Preferably, in the diffusion welding, the stress direction of the TiAl material is perpendicular to the lamellar direction.

[0018] In the technical solution of the present application, the poly lamella twin TiAl (PST-TiAl) single crystal has an alternating lamellar structure of γ-TiAl phase and α2-Ti3Al phase; in the diffusion welding, the stress direction of the TiAl material is perpendicular to the alternating lamellar structure.

[0019] As a preferred embodiment, the chemical mechanical polishing comprises rough polishing and fine polishing in sequence.

[0020] Preferably, the rough polishing adopts a silica polishing liquid; the mass fraction of the silica polishing liquid is 20wt.%-30wt.%; in the silica polishing liquid, the particle size of SiO2 abrasive is 80-150nm; the pH of the silica polishing liquid is 10.0-11.5;

[0021] Preferably, the rough polishing is as follows: fixing the polishing pad on the polishing disc and fixing the TiAl material in the polishing carrier; placing the polishing carrier on the polishing pad, so that the welding surface is opposite to the polishing pad; during the polishing, applying the silica polishing liquid; applying a polishing pressure of 3.0-5.0psi through the polishing carrier; the rotation speed of the polishing disc is 60-90rpm; the rotation speed of the polishing carrier is 55-85rpm, and the rotation directions of the polishing disc and the polishing carrier are the same; the polishing time is 3-8min; in the technical solution of the present application, the macro damage layer on the welding surface can be quickly removed and global planarization can be realized through the rough polishing;

[0022] Preferably, the fine polishing adopts a silica polishing liquid; the mass fraction of the silica polishing liquid is 5wt.%-15wt.%; the pH of the silica polishing liquid is 9.5-10.5;

[0023] Preferably, the fine polishing is a step-by-step polishing; in the step-by-step polishing, the maximum particle size of the SiO2 abrasive is 70-80 nm and the minimum particle size is 40-50 nm; in some specific embodiments, the fine polishing is: sequentially polishing with SiO2 abrasives with particle sizes of 70 nm, 60 nm and 50 nm.

[0024] Preferably, the fine polishing involves: fixing a polishing pad onto a polishing disc; fixing the coarsely polished TiAl material into a polishing carrier; placing the polishing carrier onto the polishing pad with the surface to be welded facing the polishing pad; applying silica polishing slurry during polishing; applying a polishing pressure of 1.0–2.5 psi through the polishing carrier; rotating the polishing disc at 30–50 rpm; rotating the polishing carrier at 25–45 rpm; rotating the polishing disc and the carrier in the same direction; and polishing for 5–15 minutes. In this invention, fine polishing eliminates microscopic scratches, resulting in a damage-free, ultra-smooth surface, providing an atomically flat substrate for the subsequent diffusion welding process of α2 phase epitaxial growth.

[0025] In another aspect, the present invention provides the application of the above method in the preparation of TiAl alloy structural parts.

[0026] In another aspect, the present invention provides TiAl alloy structural parts obtained by the above method.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] This invention utilizes chemical mechanical polishing of the interface to be welded to remove the surface damage layer, thus avoiding the random precipitation of the α2 phase during diffusion bonding. This effectively guides the α2 phase to grow epitaxially along the orientation of the base material during diffusion bonding, ensuring crystallographic continuity of the α2 phase at the bonding interface. This improves the deformation compatibility of the α2 phase at the bonding interface, allowing it to slide synergistically with γ-lamellae during deformation, significantly enhancing the deformation compatibility and mechanical properties of the weld interface. This method achieves a transformation from the traditional "obstruction-type" α2 phase to a "synergistic" α2 phase, significantly improving the plasticity of the joint. The method provided by this invention is simple, highly adaptable, requires no additional elements or special welding materials, has a clear structural control mechanism, and shows promising engineering application prospects. It is particularly suitable for the complex structure manufacturing and repair of high-end lightweight high-temperature materials such as PST-TiAl single crystals, and has application value in the aerospace and defense equipment fields. Attached Figure Description

[0029] Figure 1 The following are experimental steps in Example 1; (a) shows the TiAl single crystal rod and sample dimensions; (b) shows a schematic diagram of diffusion welding; and (c) shows the sampling location and dimensions of the mechanical test sample.

[0030] Figure 2 The figures show the surface morphology and subsurface characterization results of the samples after chemical mechanical polishing in Example 1; where (a) is a surface SEM image and (b) is a subsurface TEM image.

[0031] Figure 3 The figures show the EBSD characterization results of the weld interface of the welded sample prepared in Example 1; where (a) is the IPF-Y diagram and (b) is the phase diagram.

[0032] Figure 4 The images show the weld interface morphology of the welded sample prepared in Example 1 after mechanical property testing. In the image, (a) shows the surface slip morphology; (b)-(c) show the EBSD analysis of the weld interface; (d) is an enlarged view of the purple box area in (a); and (e)-(f) show the TEM image, TKD image, and 3D unit cell, respectively. The sampling point is position e in the image (d).

[0033] Figure 5 To illustrate the surface morphology and subsurface characterization of the surfaces to be welded after mechanical polishing in Comparative Example 1, (a) is a surface SEM image; (b) is a subsurface TEM image.

[0034] Figure 6 The EBSD characterization results of the weld interface of the welded parts prepared in Comparative Example 1 are shown; where (a) is the IPF-Y diagram and (b) is the phase diagram.

[0035] Figure 7 Figure 1 shows the morphology of the weld interface after mechanical property testing of the welded parts prepared in Comparative Example 1. Figure 1(a) shows the surface slip morphology; Figures 1(b)-1(d) show the EBSD analysis of the weld interface; Figure 2(e) shows the TEM image with the sampling point located at position e in Figure 1(a); Figure 3(f) is an enlarged view of the area selected by the yellow box in Figure 2(e). Detailed Implementation

[0036] The following embodiments are merely some, not all, of the embodiments of the present invention. Therefore, the detailed descriptions of the embodiments provided below are not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0037] In this invention, unless otherwise specified, all equipment and raw materials are commercially available or commonly used in the industry. The methods described in the following embodiments are conventional methods in the art, unless otherwise specified.

[0038] Example 1:

[0039] (1) A polylaminar twinned TiAl single crystal (PST-TiAl) of Ti45Al8Nb (atomic percentage) was selected as the base material. This base material contains a layered structure consisting of alternating and parallel γ-TiAl and α2-Ti3Al phases. The base material was prepared into a sample to be welded by electrical discharge machining (EDM). The sample orientation and size diagram in this embodiment are shown in the figure below. Figure 1 As shown in Figure (a);

[0040] (2) Perform chemical mechanical polishing on the surface of the sample to be welded to obtain a sample without a damaged surface layer.

[0041] 1) Rough Polishing Stage: Fix the polishing pad onto the polishing disc and fix the sample to be welded into the polishing carrier; place the polishing carrier onto the polishing pad, with the surface to be welded facing the polishing pad; apply a 25 wt.% silica polishing slurry during polishing; the silica abrasive particles in the polishing slurry have a particle size of 100 nm and a pH of 11.0; set the rotation speed of the polishing disc to 70 rpm and the rotation speed of the polishing carrier to 65 rpm, with the polishing disc and polishing carrier rotating in the same direction; apply a polishing pressure of 4.0 psi through the polishing carrier, and polish for 5 minutes; rough polishing is mainly used to remove surface processing marks and oxide layers formed in the previous wire cutting process, ensuring that the processed surface has basic flatness;

[0042] 2) Fine polishing stage: Fix the polishing pad onto the polishing disc; fix the coarsely polished TiAl material into the polishing carrier, place the polishing carrier on the polishing pad, with the surface to be welded facing the polishing pad; apply a 10 wt.% silica polishing slurry during polishing; sequentially use silica polishing slurries with particle sizes of 70 nm, 60 nm, and 50 nm for progressive polishing; the pH of the polishing slurry is 10.0; set the polishing disc speed to 30 rpm and the carrier speed to 25 rpm, with the polishing disc and carrier rotating in the same direction; apply a polishing pressure of 1.0 psi through the polishing carrier, and polish for 10 min; fine polishing can eliminate micro-ripples and subsurface deformation zones, and obtain a mirror-like high-quality surface; after chemical mechanical polishing, there is no damaged layer on the sample surface.

[0043] The surface and subsurface after chemical mechanical polishing were characterized using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), and the results are as follows: Figure 2 As shown: Thanks to the continuous steps from coarse grinding to fine grinding, the surface to be welded is flat and there is no damaged layer on the subsurface, which meets the requirements of a surface without a damaged layer.

[0044] (3) Figure 1 As shown in Figure (b), the chemically mechanically polished samples with their surfaces to be welded are stacked face to face and placed in the diffusion welding equipment. The mechanical pump is turned on, and the vacuum level is maintained at 10.0 After Pa, turn on the molecular pump until the vacuum level is ≤10. -4 Pa; the temperature was increased to 1100℃ at 10℃ / min, the pressure was set to 20MPa, and the temperature was held for 2h; after the holding period, the sample was cooled to room temperature in the furnace to obtain the welded sample.

[0045] Figure 3 The image shows the EBSD characterization of the weld interface of the weld sample prepared in this embodiment. The α2 phase at the weld interface has the same IPF-Y color as the α2 phase in the base material. The IPF orientation triangle indicates that the α2 phase at the weld interface has achieved epitaxial growth and has the same crystal orientation as the α2 phase in the base material.

[0046] Mechanical properties were tested on the welded specimens (tensile rate of 10). -4 s - 1) To verify whether the epitaxially grown α2 phase can synergistically deform the parent material during service, the sampling location and size of the mechanical test specimens are as follows: Figure 1 The results are shown in Figure (c). The morphology of the weld interface after mechanical property testing is shown in Figure (c). Figure 4 The surface slip morphology characterization results in Figure (a) show that dislocation slip can pass unimpeded through the α2 phase at the weld interface (Region I). Figure (d) is an enlarged view of the purple-boxed area in Figure (a). From the EBSD characterization results of Region I in Figures (b) and (c), the TEM characterization results in Figure (e), the TKD characterization results in Figure (f), and the 3D unit cell, it can be seen that the α2 phase at the weld interface (position ①) is oriented in the same way as the α2 phase in the base material (position ②), thus maintaining a coherent relationship with the closely adjacent γ-TiAl phase lamellars. This structural compatibility facilitates the continuous transfer of slip at the interface and does not lead to stress concentration. Furthermore, the α2 phase at the weld interface not only has the same orientation as the α2 phase in the base material but also retains a lamellar structure (positions ① and ②), thereby enhancing the slip compatibility between the interfaces.

[0047] Example 2:

[0048] The preparation process of the welded sample in this embodiment is the same as in Embodiment 1, except that:

[0049] In step (3): replace the heating rate with 5℃ / min; replace the welding temperature with 1000℃; replace the pressure with 10MPa; and replace the holding time with 10h.

[0050] In this embodiment, the α2 phase at the welding interface of the welded sample also achieved epitaxial growth, which can work in tandem with the deformation of the base material.

[0051] Example 3:

[0052] The preparation process of the welded sample in this embodiment is the same as in Embodiment 1, except that:

[0053] In step (3): replace the heating rate with 20℃ / min; replace the welding temperature with 1300℃; replace the pressure with 50MPa; and replace the holding time with 1h.

[0054] In this embodiment, the α2 phase at the welding interface of the welded sample also achieved epitaxial growth, which can work in tandem with the deformation of the base material.

[0055] Comparative Example 1:

[0056] The preparation process of this comparative example is the same as that of Example 1, except that step (2) is different. In this example, step (2) involves mechanically polishing the surface to be welded. The specific steps are as follows:

[0057] 1) Rough grinding stage: First, use 500-grit SiC sandpaper (silicon carbide) to perform preliminary grinding on the surface to be welded, to remove rough marks and oxide layer formed during wire cutting or previous processing, and to initially smooth the surface;

[0058] 2) Gradual fine grinding stage: Based on the coarse grinding, use sandpaper of 1000 grit, 2000 grit, 3000 grit and 5000 grit for gradual fine grinding to reduce surface scratches and dents;

[0059] 3) Fine polishing stage: Using diamond polishing paste with a particle size of 0.5μm in conjunction with polishing cloth, the sample surface is finely polished to remove residual fine scratches and obtain a mirror effect;

[0060] The surface of the comparative sample after mechanical polishing is shown by SEM and TEM. Figure 5 As shown in Figure (a), due to the difference in hardness between the γ phase and α2 phase in the TiAl alloy, the removal rates of the two phases are inconsistent during mechanical polishing, easily leading to stress concentration at the interface between the two phases and resulting in the formation of microcracks. As shown in Figure (b), a micron-sized damage layer exists on the subsurface, the single-crystal structure is broken, and it exhibits characteristics such as dense dislocation accumulation and local plastic deformation bands. Therefore, it can be seen that the surface to be welded in this comparative example has a damage layer.

[0061] Figure 6 The figures show the EBSD characterization results of the weld interface of the welded sample obtained in this comparative example. Figure (a) is the IPF-Y diagram; Figure (b) is the phase diagram. It can be seen from the figures that the IPF-Y color of the α2 phase at the weld interface is different from that of the α2 phase in the base material, indicating that their orientations are inconsistent. It is noteworthy that the α2 phase at the interface also has different orientations, indicating that a randomly oriented α2 phase has precipitated.

[0062] Figure 7The figures show the weld interface morphology after mechanical property testing of the welded samples. Figure (a) shows the surface slip morphology; figures (b)-(d) show the EBSD analysis of the weld interface; figure (e) is a TEM image, with the sampling point located at position e in figure (a); and figure (f) is a magnified view of the area highlighted in yellow in figure (e). The figures show that stress accumulates not only at the γ recrystallization grain boundaries (regions I and III) but also at the α2 phase (region II), indicating that these regions hinder dislocation slip. The 3D unit cell of the α2 phase further illustrates the random orientation of its precipitation and its inability to coordinate with the deformation behavior of the parent material.

[0063] As can be seen from Comparative Example 1 and Example 1, due to the presence of the damaged layer, randomly oriented α2 phase precipitates during the welding process. During service, the randomly oriented α2 phase exhibits characteristics of a brittle phase, hindering dislocation slip, causing stress concentration, and ultimately leading to crack initiation.

[0064] Comparative Example 2:

[0065] The preparation process of the welded sample in this comparative example is the same as that in Comparative Example 1, except that:

[0066] In step (3): replace the heating rate with 5℃ / min; replace the welding temperature with 1000℃; replace the pressure with 10MPa; and replace the holding time with 10h.

[0067] The weld interface of the welded sample obtained in this comparative example is the same as that of comparative example 1, with randomly oriented α2 phase precipitated, which has brittle phase characteristics and cannot deform in tandem with the base material.

[0068] Comparative Example 3:

[0069] The preparation process of the welded sample in this comparative example is the same as that in Comparative Example 1, except that:

[0070] In step (3): replace the heating rate with 20℃ / min; replace the welding temperature with 1300℃; replace the pressure with 50MPa; and replace the holding time with 1h.

[0071] The weld interface of the welded sample obtained in this comparative example is the same as that of comparative example 1, with randomly oriented α2 phase precipitated, which has brittle phase characteristics and cannot deform in tandem with the base material.

[0072] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for regulating the diffusion-connection interface to guide the evolution of the α2 phase from a hindered to a cooperative state, characterized in that, Includes the following steps: (1) Chemical mechanical polishing was performed on the TiAl material to be welded to obtain a sample to be welded without a damaged layer on the surface of the surface to be welded. (2) Diffusion welding is performed on the two samples to be welded.

2. The method according to claim 1, characterized in that, The vacuum degree of the diffusion welding is ≤10. -4 Pa; the temperature of the diffusion welding is 1000-1300℃; the pressure of the diffusion welding is 10-50MPa; Preferably, the heat preservation time for diffusion welding is 1 to 10 hours; Preferably, the heating rate of the diffusion welding is 5–20 °C / min; Preferably, the diffusion welding further includes a process of cooling to room temperature in the furnace.

3. The method according to claim 1, characterized in that, The TiAl material is a TiA alloy, selected from either fully lamellar TiAl polycrystalline or polylamellar twinned TiAl (PST-TiAl) single crystal; Preferably, in diffusion welding, the direction of the force on the TiAl material is perpendicular to the lamellar direction; Preferably, the polylaminated twinned TiAl (PST-TiAl) single crystal has an alternating layered structure of γ-TiAl phase and α2-Ti3Al phase; during diffusion welding, the force direction of the TiAl material is perpendicular to the alternating layered structure.

4. The method according to claim 1, characterized in that, The chemical mechanical polishing process includes rough polishing and fine polishing.

5. The method according to claim 4, characterized in that, The rough polishing is performed using a silica polishing slurry; the mass fraction of the silica polishing slurry is 20 wt.% to 30 wt.%; the particle size of the SiO2 abrasive in the silica polishing slurry is 80 to 150 nm; and the pH of the silica polishing slurry is 10.0 to 11.

5.

6. The method according to claim 4, characterized in that, The rough polishing process involves: fixing a polishing pad onto a polishing disc and fixing the TiAl material into a polishing carrier; placing the polishing carrier onto the polishing pad with the surface to be welded facing the polishing pad; applying silica polishing slurry during polishing; applying a polishing pressure of 3.0–5.0 psi through the polishing carrier; rotating the polishing disc at 60–90 rpm; rotating the polishing carrier at 55–85 rpm, with the polishing disc and polishing carrier rotating in the same direction; and polishing for 3–8 minutes.

7. The method according to claim 4, characterized in that, The fine polishing is performed using a silica polishing slurry; the mass fraction of the silica polishing slurry is 5 wt.% to 15 wt.%; the pH of the silica polishing slurry is 9.5 to 10.

5. Preferably, the fine polishing is a step-by-step polishing; in the step-by-step polishing, the maximum particle size of the SiO2 abrasive is 70-80 nm and the minimum particle size is 40-50 nm.

8. The method according to claim 4, characterized in that, The fine polishing process involves: fixing a polishing pad onto a polishing disc; fixing the coarsely polished TiAl material into a polishing carrier; placing the polishing carrier onto the polishing pad with the surface to be welded facing the polishing pad; applying silica polishing slurry during polishing; applying a polishing pressure of 1.0–2.5 psi through the polishing carrier; rotating the polishing disc at 30–50 rpm; rotating the polishing carrier at 25–45 rpm; rotating the polishing disc and carrier in the same direction; and polishing for 5–15 minutes.

9. The application of the method according to any one of claims 1-8 in the preparation of TiAl alloy structural parts.

10. The TiAl alloy structural component obtained by the method of any one of claims 1-8.

Images