Preparation method of titanium alloy gradient functional material

Abstract

The invention discloses a preparation method of a titanium alloy gradient functional material and belongs to the field of advanced processing and preparation of titanium alloy materials. The method provided by the invention can be used for preparing titanium alloy materials with different components and different tissue types, and the specific implementation process is as follows: firstly, grinding the titanium alloy bonding surfaces with different components or different tissue types by adopting a mechanical grinding mode, and then putting the titanium alloy bonding surfaces into a hot pressing furnace for heat preservation and pressure preservation to realize metallurgical bonding between titanium alloys; and a furnace cooling mode is adopted for cooling, and finally the titanium alloy gradient functional material is obtained. The titanium alloy gradient functional material prepared through the method is free of defects at the gradient interface, good in transition area structure combination and excellent in mechanical property, controllable design of components and structures of different areas of the titanium alloy material can be achieved, and technical support and theoretical guidance are provided for preparation and application of the titanium alloy gradient functional material.

Description

Technical Field

[0001] The invention relates to the field of advanced processing and preparation of titanium alloy materials, and in particular to a method for preparing a titanium alloy gradient functional material. Background Art

[0002] Titanium alloys are widely used in the manufacture of major aerospace components due to their advantages such as light weight, high strength and good corrosion resistance. However, as the requirements for components become more and more stringent, ordinary strength titanium alloys can no longer meet the development needs, and titanium alloy components with gradient structures have become the key to promoting the development of the aviation industry. Functionally gradient materials (FGM) refer to a functional composite material in which the uniform or non-uniform changes in internal components cause the microstructure, performance and other elements of the material to change accordingly. With the continuous development of the aerospace industry, components are constantly developing towards integration and structural function integration, and a clear demand has been put forward for dual-performance composites, requiring different parts of the overall component to have different properties. Functionally gradient materials, as a typical non-uniform material, have good designability. By changing the components and microstructure of gradient materials, the purpose of having different functions in different areas can be achieved. These characteristics that traditional materials cannot match make gradient materials have important development and application prospects in the fields of aviation and aerospace, but they are usually difficult to achieve through traditional casting or forging.

[0003] The traditional methods for preparing gradient functional materials mainly include additive manufacturing and powder metallurgy. These methods are relatively mature and widely used in production, but there are still some problems. For example, NASA Langley Research Center in the United States disclosed a method for preparing titanium alloy gradient functional materials by laser melting deposition technology, but ultimately failed to form a complete gradient material without cracks or unfused defects; the Russian Central Aviation Engine Research Institute disclosed a solution for preparing turbine disks by powder metallurgy, but there are practical problems such as high cost, long cycle and complex process; Beijing University of Aeronautics and Astronautics disclosed a method for preparing titanium alloy gradient materials for aircraft engine turbine blades and turbine disks by additive manufacturing, but there is a problem of easy cracks at the interface. The physical properties of each layer in the gradient material, such as density, thermal expansion coefficient, melting point and laser absorptivity, are different. It is difficult to accurately obtain gradient functional materials using conventional single material design theory, which to a certain extent restricts the application and development of titanium alloy gradient functional materials. Therefore, how to prepare titanium alloy gradient functional materials with good comprehensive performance, continuous gradient microstructure at the interface, elimination of performance mutation and mismatch problems between different types of titanium alloys, and reduction of plastic deformation and cracking tendency under service conditions is one of the key issues that need to be solved. Summary of the invention

[0004] In order to solve the above problems, the present invention provides a method for preparing a titanium alloy gradient functional material, and the titanium alloy gradient functional material is prepared by hot pressing technology. The titanium alloy gradient functional material prepared by the present invention has no defects at the gradient interface, the transition zone organization is tightly combined, the mechanical properties are excellent, and it is not limited by the shape of the component, so that the layout of the titanium alloy material is designable, the weight reduction efficiency is improved, and the multi-functional integration of load-bearing, heat resistance, corrosion resistance, etc. is achieved.

[0005] In order to achieve the above objectives, the technical solution of the present invention is:

[0006] A method for preparing a titanium alloy gradient functional material, the specific process of the method is as follows:

[0007] (1) Raw material processing

[0008] The bonding surfaces of titanium alloys of different grades and tissue types are machined until the roughness of the bonding surfaces is between Ra0.05-1.6μm, and then the bonding surfaces are degreased and dried;

[0009] (2) Gradient material preparation

[0010] The treated titanium alloy surfaces are butt-jointed and assembled, and the assembled titanium alloy material is placed in a hot pressing furnace for hot pressing treatment to prepare a titanium alloy gradient functional material under an inert atmosphere.

[0011] The method is not limited to titanium alloy grades, tissue types and shapes, and can prepare titanium alloy gradient functional materials of any grades, tissue types and shapes;

[0012] The mechanical processing process is as follows: firstly, the mating surface is turned by a lathe, and then the mating surface is polished to ensure that the mating surface is flat and has no machining marks left, and the roughness of the mating surface is Ra=0.05-1.6μm;

[0013] The matching tolerance between the titanium alloys of different grades and tissue types that match each other is less than 0.5mm;

[0014] The surface oil stains are removed by using petroleum ether and alcohol to clean the titanium alloy in sequence until there is no contaminant on the bonding surface;

[0015] During the docking assembly process, ensure that the material does not deform during the assembly process;

[0016] Before the treatment begins, flush the hot pressing furnace with inert gas 3-5 times to remove oxygen in the hot pressing furnace;

[0017] The hot pressing system is as follows: in an inert atmosphere, at a temperature of 700°C-1000°C, at a pressure of 120MPa-180MPa, and for a holding time of 1h-5h, followed by cooling to below 200°C with the furnace, and taking out of the furnace to obtain a titanium alloy gradient functional material.

[0018] The design concept of the present invention is:

[0019] First, the bonding surfaces of titanium alloys with different compositions and tissue types are polished by mechanical polishing to ensure that the bonding surfaces are flat. Then, petroleum ether and alcohol are used to clean the oil stains on the bonding surfaces in turn, and the bonding surfaces are butt-jointed and assembled to ensure that the materials do not deform during the assembly process. Then, they are placed in a hot pressing furnace for hot pressing. The hot pressing system is: in an inert gas atmosphere, at a temperature of 700°C-1000°C, a pressure of 120MPa-180MPa, and a heat preservation of 1h-5h. After the furnace is cooled to below 200°C, it is taken out of the furnace. The metallurgical bonding between titanium alloys with different compositions and tissue types is achieved to obtain titanium alloy gradient functional materials. When preparing the titanium alloy gradient functional material, the present invention applies equal pressure to each surface of the material through inert gas, and at the same time applies high temperature. Under the action of high temperature and high pressure, the distance between molecules is reduced without plastic deformation, thereby promoting the diffusion of alloy elements at the interface. Therefore, the gradient interface of the titanium alloy gradient functional material prepared by the present invention is free of defects, the alloy elements are fully diffused at the interface, the transition zone organization is tightly combined, and the microstructure at the interface is continuously gradual, eliminating the performance mutation and mismatch problems of the combination between titanium alloys of different types and organizational types, reducing the tendency of plastic deformation and cracking under service conditions, and preparing titanium alloy gradient functional materials with excellent mechanical properties. In addition, the present invention eliminates the disadvantages of traditional diffusion bonding technology that only applies pressure in the axial direction, the components undergo large plastic deformation, and the structure of the prepared components is single. The components prepared by the present invention are not limited by the structure and titanium alloy composition and organizational type, so that the layout of the titanium alloy gradient functional material has designability, improves weight reduction efficiency and fatigue life, and realizes the integration of multiple functions such as load-bearing, heat resistance, and corrosion resistance.

[0020] The advantages and beneficial effects of the present invention are:

[0021] The present invention provides a preparation method of a titanium alloy gradient functional material. Firstly, mechanical grinding is used to grind the bonding surfaces of different types of titanium alloys, the bonding surfaces are butt-jointed and assembled, and then they are placed in a hot pressing furnace for heat preservation and pressure preservation to achieve metallurgical bonding. After hot pressing, a furnace cooling method is adopted to finally obtain the titanium alloy gradient functional material.

[0022] 1. When preparing titanium alloy gradient functional materials through the technology of the present invention, it will not cause deformation, melting or relative movement of the titanium alloy material. Complex structures that are difficult to form by conventional processes can be prepared, and the accuracy of the formed components can be guaranteed. The design of the components is not restricted by shape, and the layout of the titanium alloy material is designable.

[0023] 2. The titanium alloy gradient functional material prepared by the method provided by the present invention has no obvious joints, no defects at the gradient interface, and excellent mechanical properties. It can prepare parts with complex shapes and high forming precision, providing technical support and theoretical guidance for the application of titanium alloy gradient functional materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Functionally graded materials of titanium alloys with different compositions: (a) is the interface microstructure; (b) is the interface mechanical properties.

[0025] Figure 2 Functionally gradient materials of titanium alloys with different tissue types: (a) is Widmanstätten alloy; (b) is equiaxed alloy.

[0026] Figure 3 Schematic diagram of titanium alloy gradient functional materials in different states: (a) is the "inside-out" state; (b) is the "up-down" state. DETAILED DESCRIPTION

[0027] In the specific implementation process, the present invention firstly grinds the bonding surfaces of different types of titanium alloys by mechanical grinding to ensure that the roughness of the bonding surface is Ra=0.05-1.6μm, and then uses petroleum ether and alcohol to clean the oil stains on the bonding surface in turn, and then welds the connecting alloys, and then places them in a hot pressing furnace for hot pressing. The hot pressing system is: in an inert gas atmosphere, a temperature of 700℃-1000℃, a pressure of 120MPa-180MPa, and insulation for 1-5h. After cooling to below 200℃ in the furnace, the alloys are taken out of the furnace to achieve metallurgical bonding between different types of titanium alloys and obtain a titanium alloy gradient functional material.

[0028] Below, the present invention is further described in detail by examples.

[0029] Example 1

[0030] In this embodiment, the end faces of the titanium alloy 1 and titanium alloy 2 bars are first mechanically polished by mechanical polishing to make the roughness of the bonding surface of the titanium alloy 1 and titanium alloy 2 Ra = 0.8μm, and then the oil stains on the end faces of the bars are cleaned off with petroleum ether and alcohol in turn and then dried. The bonding surfaces of the titanium alloy 1 and titanium alloy 2 are first locally spot welded to ensure that the material does not deform during the sealing process, and then sealed by electron beam welding with a sealing depth of 5mm. Subsequently, they are placed in a hot pressing furnace for connection. The hot pressing system is: inert atmosphere, temperature 950°C, pressure 160MPa, and insulation for 4h. After cooling to below 200°C in the furnace, the materials are taken out of the furnace to obtain a titanium alloy gradient functional material.

[0031] Figure 1 a is the microstructure of the interface of titanium alloy gradient functional material after being kept at 950℃ and 160MPa for 4h. Figure 1 It can be seen from a that there are no defects at the gradient interface of the titanium alloy gradient functional material prepared in this embodiment, and the transition zone organization is tightly combined. Figure 1 It can be clearly seen from b that the elongation at the gradient interface of the titanium alloy gradient functional material prepared in this embodiment is 15.5%, the strength is 952MPa, the strength and toughness are matched, and the mechanical properties are excellent and comparable to those of forgings, providing an effective solution for the practical application of titanium alloy gradient functional materials.

[0032] Example 2

[0033] In this embodiment, Figure 2 As shown in (a) and (b), the microstructure types of titanium alloys before preparation are Widmanstatten and equiaxed structures, respectively. First, the end faces of titanium alloy bars of different microstructure types are mechanically polished to make the roughness of the bonding surfaces of titanium alloys of different microstructure types Ra = 0.8μm. Then, petroleum ether and alcohol are used to clean the oil stains on the circumferential surface of the bars in turn and then dry them. The bonding surfaces of titanium alloys of different microstructure types are first spot-welded locally to ensure that the material does not deform during the sealing process. Subsequently, they are placed in a hot pressing furnace for hot pressing. The hot pressing system is: under a high-purity argon atmosphere, a temperature of 950°C, a pressure of 160MPa, and a heat preservation of 4h. After cooling to below 200°C in the furnace, the functional gradient materials of titanium alloys of different microstructure types are obtained. The interface microstructure is shown in FIG. Figure 2 As shown in (c), there are no defects at the interface and the transition zone structures are tightly integrated.

[0034] Example 3

[0035] In this embodiment, Figure 3 As shown in the figure, after keeping the temperature at 950℃ and 160MPa for 4h, the "inside-outside" and "up-down" titanium alloy gradient functional materials were prepared. Figure 3It can be clearly seen that the titanium alloy gradient functional material prepared in this embodiment solves the problem of shape limitation in the preparation process of the titanium alloy gradient functional material, and provides an effective solution for the practical application of the titanium alloy gradient functional material.

[0036] The above is only the best example of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiments according to the technical essence of the invention still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing a titanium alloy functional gradient material, characterized in that: The specific steps include: (1) Raw material processing The bonding surfaces of titanium alloys of different grades and tissue types are machined to control the roughness of the bonding surface Ra to 0.05μm-1.6μm, and then the bonding surface is degreased and dried; (2) Gradient material preparation The treated titanium alloy surfaces are butt-jointed and assembled, and the assembled titanium alloy material is placed in a hot pressing furnace for hot pressing treatment to prepare a titanium alloy gradient functional material under an inert atmosphere; The hot pressing process is specifically as follows: in an inert atmosphere, at a temperature of 700°C-1000°C, at a pressure of 120MPa-180MPa, and for a holding time of 1h-5h, followed by furnace cooling to below 200°C, and after furnace cooling, a titanium alloy gradient functional material is obtained.

2. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: The method is not limited to titanium alloy grades, tissue types and shapes, and can prepare titanium alloy gradient functional materials of any grade, tissue type and shape.

3. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: The processing flow is as follows: firstly, the bonding surface is turned by a lathe, and then the bonding surface is polished to ensure that the bonding surface is flat and has no residual processing marks, and the roughness of the bonding surface is Ra=0.05μm-1.6μm.

4. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: The matching tolerance between the titanium alloys of different grades and tissue types is less than 0.5 mm.

5. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: The surface oil stains are removed by using petroleum ether and alcohol to clean the titanium alloy in sequence until there is no contaminant on the bonding surface.

6. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: During the butt-jointed assembly process, it is ensured that the material does not deform during the assembly process.

7. The method for preparing a titanium alloy functional gradient material according to claim 1, characterized in that: Before the hot pressing process begins, the hot pressing furnace is flushed with inert gas for 3-5 times to remove oxygen in the hot pressing furnace.

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