A method for preparing a titanium alloy functionally graded material

Abstract

The application relates to 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 can be used for preparing titanium alloy materials with different components and different organizational types. The specific implementation process is as follows: firstly, a mechanical polishing method is used to polish the combination surface of titanium alloys with different components or different organizational types; then the titanium alloys are placed in a hot pressing furnace for heat preservation and pressure preservation to realize metallurgical combination between the titanium alloys; a furnace cooling method is used for cooling; and finally, the titanium alloy gradient functional material is obtained. The titanium alloy gradient functional material prepared by the method has no defects at the gradient interface, the transition zone organization is well combined, and the mechanical properties are excellent. The composition and organization of different regions of the titanium alloy material can be controlled and designed, technical support and theoretical guidance are provided for the preparation and application of the titanium alloy gradient functional material.

Description

Technical Field

[0001] This invention relates to the field of advanced processing and preparation of titanium alloy materials, specifically a method for preparing graded functional titanium alloy materials. Background Technology

[0002] Titanium alloys, due to their lightweight, high strength, and excellent corrosion resistance, are widely used in the manufacture of key aerospace components. However, as the requirements for components become increasingly stringent, ordinary strength titanium alloys can no longer meet the development needs. Titanium alloy components with gradient structures have become crucial for driving the development of the aerospace industry. Functionally graded materials (FGMs) are functional composite materials in which the uniform or non-uniform variation of internal composition alters the microstructure and properties of the material. With the continuous development of the aerospace industry, components are increasingly moving towards integration and structural-functional integration, creating a clear demand for dual-performance composites. This requires different parts of the overall component to possess different properties. As a typical non-uniform material, FGMs have excellent designability; by changing the composition and microstructure of the gradient material, different functions can be achieved in different regions. These unparalleled characteristics of traditional materials make gradient materials a promising candidate for development and application in aerospace and other fields, but they are usually difficult to achieve through traditional casting or forging.

[0003] Traditional methods for preparing graded functional materials (JDM) mainly include additive manufacturing and powder metallurgy. These methods are relatively mature and widely used in production, but some problems still exist. For example, NASA's Langley Research Center disclosed a method for preparing titanium alloy JDM using laser melting deposition technology, but ultimately failed to form a complete graded material without cracks or incomplete fusion defects. The Central Institute of Aero-Engine Research in Russia disclosed a scheme for preparing turbine disks using powder metallurgy, but it suffers from high cost, long cycle time, and complex process. Beijing University of Aeronautics and Astronautics disclosed a method for preparing titanium alloy JDM for aero-engine turbine blades and turbine disks using additive manufacturing, but it suffers from the problem of easy cracking at the interface. The physical properties of each layer in a graded material, such as density, coefficient of thermal expansion, melting point, and laser absorptivity, are different. It is difficult to accurately obtain JDM using conventional single-material design theory, which to some extent restricts the application and development of titanium alloy JDM. Therefore, one of the key issues to be addressed is how to prepare titanium alloy graded functional materials with good overall performance, continuous and gradual microstructure at the interface, elimination of abrupt performance changes and mismatches between different types of titanium alloys, and reduction of plastic deformation and cracking tendency under service conditions. Summary of the Invention

[0004] To address the above problems, this invention provides a method for preparing titanium alloy graded functional materials, which utilizes hot pressing technology. The titanium alloy graded functional materials prepared by this invention exhibit defect-free gradient interfaces, tightly bonded transition zones, excellent mechanical properties, and are not limited by the shape of the component. This allows for designable titanium alloy material layout, improves weight reduction efficiency, and achieves multifunctional integration of load-bearing capacity, heat resistance, and corrosion resistance.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows:

[0006] A method for preparing graded functional titanium alloys, the specific process of which is as follows:

[0007] (1) Raw material processing

[0008] The mating surfaces of titanium alloys of different grades and microstructures are machined until the surface roughness is between Ra0.05-1.6μm, and then the oil stains on the mating surfaces are removed and dried.

[0009] (2) Gradient material preparation

[0010] The mating surfaces of the treated titanium alloys are joined together, and the assembled titanium alloy materials are placed in a hot press furnace for hot pressing treatment, thus preparing titanium alloy graded functional materials under an inert atmosphere.

[0011] The method is not limited to titanium alloy grades, microstructure types, and shapes, and can prepare graded functional materials of titanium alloys with arbitrary grades, microstructure types, and shapes.

[0012] The machining process is as follows: First, the mating surfaces are machined using a lathe, and then the mating surfaces are polished to ensure that the mating surfaces are flat and free of machining marks. The surface roughness Ra = 0.05-1.6μm.

[0013] The fit tolerance between the different grades and microstructures of the titanium alloys is less than 0.5 mm.

[0014] To remove surface oil stains, petroleum ether and alcohol are used to clean the titanium alloy sequentially until the bonding surface is free of contaminants.

[0015] During the docking and assembly process, ensure that the materials do not deform.

[0016] Before the process begins, the hot press furnace is flushed with inert gas 3-5 times to remove oxygen from the furnace.

[0017] The hot pressing process is as follows: under an inert atmosphere, at a temperature of 700℃-1000℃, a pressure of 120MPa-180MPa, and a holding time of 1h-5h, the material is then cooled in the furnace to below 200℃ and then removed from the furnace to obtain a titanium alloy graded functional material.

[0018] The design concept of this invention is:

[0019] First, the bonding surfaces of titanium alloys with different compositions and microstructures are mechanically polished to ensure a smooth surface. Then, oil stains are removed from the bonding surfaces using petroleum ether and alcohol, respectively. The bonding surfaces are then assembled, ensuring no deformation occurs during the assembly process. Next, the alloys are hot-pressed in a furnace under the following conditions: in an inert gas atmosphere, at a temperature of 700℃-1000℃, a pressure of 120MPa-180MPa, and a holding time of 1-5 hours. After cooling to below 200℃ in the furnace, the alloys are removed from the furnace. This process achieves metallurgical bonding between titanium alloys with different compositions and microstructures, resulting in a titanium alloy functional graded material. In preparing graded functional titanium alloys according to this invention, equal pressure is applied to each surface of the material using an inert gas, while simultaneously applying 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 alloying elements at the interface. Therefore, the graded functional titanium alloys prepared by this invention have no defects at the gradient interface, alloying elements are fully diffused at the interface, the transition zone microstructure is tightly bonded, and the microstructure at the interface exhibits a continuous and gradual change. This eliminates the performance abrupt changes and mismatches between different types and microstructures of titanium alloys, reduces plastic deformation and cracking tendency under service conditions, and produces graded functional titanium alloys with excellent mechanical properties. Furthermore, this invention eliminates the drawbacks of traditional diffusion bonding technology, which only applies pressure axially, resulting in large plastic deformation of the component and a single structural design. The components prepared by this invention are not limited by structure, titanium alloy composition, or microstructure type, making the layout of graded functional titanium alloys designable, improving weight reduction efficiency and fatigue life, and achieving multi-functional integration of load-bearing, heat resistance, and corrosion resistance.

[0020] The advantages and beneficial effects of this invention are as follows:

[0021] This invention provides a method for preparing titanium alloy graded functional materials. First, the bonding surfaces of different types of titanium alloys are polished by mechanical grinding, and the bonding surfaces are then assembled. Subsequently, they are placed in a hot press furnace for heat preservation and pressure preservation to achieve metallurgical bonding. After hot pressing, the materials are cooled by furnace cooling to finally obtain titanium alloy graded functional materials.

[0022] 1. When preparing graded functional titanium alloy materials using the technology of this invention, the titanium alloy material will not be deformed, melted, or moved relative to its position. Complex structures that are difficult to form using conventional processes can be prepared, ensuring the accuracy of the formed components. The design of the components is not limited by shape, and the layout of the titanium alloy material is designable.

[0023] 2. The titanium alloy functionally graded materials prepared by the method provided in this invention have no obvious connecting joints, no defects at the gradient interface, and excellent mechanical properties. They can be used to fabricate complex-shaped parts with high forming precision, providing technical support and theoretical guidance for advancing the application of titanium alloy functionally graded materials. Attached Figure Description

[0024] Figure 1 Functional graded titanium alloys with different compositions: (a) interfacial microstructure; (b) interfacial mechanical properties.

[0025] Figure 2 Functional graded titanium alloys with different microstructures: (a) Widmanstätten alloy; (b) equiaxed alloy.

[0026] Figure 3 Schematic diagrams of graded functionalized titanium alloys under different states: (a) "inside and outside" state; (b) "top and bottom" state. Detailed Implementation

[0027] In the specific implementation process, the present invention first uses mechanical grinding to grind the bonding surfaces of different types of titanium alloys to ensure that the roughness of the bonding surfaces Ra = 0.05-1.6μm. Then, the oil stains on the bonding surfaces are cleaned by petroleum ether and alcohol in sequence. Then, the connecting alloys are welded and then placed in a hot press furnace for hot pressing. The hot pressing regime is as follows: in an inert gas atmosphere, temperature 700℃-1000℃, pressure 120MPa-180MPa, holding temperature for 1-5h. After cooling to below 200℃ in the furnace, it is taken out of the furnace to achieve metallurgical bonding between different types of titanium alloys and obtain titanium alloy graded functional materials.

[0028] The present invention will be further described in detail below through embodiments.

[0029] Example 1

[0030] In this embodiment, the end faces of titanium alloy 1 and titanium alloy 2 rods are first mechanically ground to achieve a surface roughness Ra of 0.8 μm at the joint surface. Then, the oil stains on the end faces of the rods are cleaned with petroleum ether and alcohol in sequence and dried. The joint surfaces of titanium alloy 1 and titanium alloy 2 are then locally spot welded to ensure that the materials do not deform during the sealing process. Then, electron beam welding is used for sealing, with a sealing depth of 5 mm. Subsequently, they are placed in a hot press furnace for connection. The hot pressing regime is as follows: inert atmosphere, temperature 950℃, pressure 160MPa, holding time 4h. After cooling to below 200℃ in the furnace, the material is removed from the furnace to obtain a titanium alloy graded functional material.

[0031] Figure 1 a shows the microstructure at the interface of the titanium alloy functionalized graded material after holding at 950℃ and 160MPa for 4 hours. Figure 1 As can be seen from a, the titanium alloy gradient functional material prepared in this embodiment has no defects at the gradient interface, and the transition region has a tight bond. Meanwhile, from... Figure 1 As can be clearly seen in b, the elongation at the gradient interface of the titanium alloy functionalized material prepared in this embodiment is 15.5%, the strength is 952 MPa, the strength and toughness are well matched, and the mechanical properties are excellent and comparable to forgings, providing an effective solution for the practical application of titanium alloy functionalized materials.

[0032] Example 2

[0033] In this embodiment, as Figure 2 As shown in (a) and (b), the titanium alloy microstructures before preparation were Widmanstätten and equiaxed microstructures, respectively. First, the end faces of the titanium alloy rods with different microstructures were mechanically ground to achieve a surface roughness Ra = 0.8 μm at the interface. Then, the oil stains on the circumference of the rods were removed sequentially using petroleum ether and alcohol, followed by drying. The interface of the titanium alloys with different microstructures was then locally spot-welded to ensure that the material did not deform during the sealing process. Subsequently, it was placed in a hot press furnace for hot pressing under the following conditions: high-purity argon atmosphere, temperature 950℃, pressure 160MPa, holding time 4h. After cooling to below 200℃ in the furnace, the material was removed from the furnace, resulting in functionally graded titanium alloys with different microstructures. The interface microstructure is shown in the figure. Figure 2 As shown in (c), there are no defects at the interface, and the transition zone shows a tight bond.

[0034] Example 3

[0035] In this embodiment, as Figure 3 As shown, "inner-outer" and "upper-lower" shaped titanium alloy graded functional materials were prepared after holding at 950℃ and 160MPa for 4 hours. From... Figure 3It can be clearly seen that the titanium alloy graded functional material prepared in this embodiment solves the problem of shape limitation in the preparation process of titanium alloy graded functional materials, and provides an effective solution for the practical application of titanium alloy graded functional materials.

[0036] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Any simple modifications, alterations, and equivalent changes made to the above embodiments based on the inventive essence shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a graded functional titanium alloy, characterized in that, Specifically, the following steps are included: (1) Raw material processing The mating surfaces of titanium alloys of different grades and microstructures are machined to control the surface roughness Ra=0.05μm-1.6μm, and then the oil stains on the mating surfaces are removed and dried. (2) Gradient material preparation The mating surfaces of the treated titanium alloys are joined together and assembled. The assembled titanium alloy materials are then placed in a hot press furnace for hot pressing treatment, and titanium alloy graded functional materials are prepared under an inert atmosphere. The hot pressing process is specifically as follows: under an inert atmosphere, at a temperature of 700℃-1000℃, a pressure of 120MPa-180MPa, and a holding time of 1h-5h, the material is then cooled in the furnace to below 200℃. After furnace cooling, a titanium alloy graded functional material is obtained. The method is not limited to titanium alloy grade, microstructure type, and shape, and can prepare titanium alloy graded functional materials of any grade, microstructure type, and shape; Before the hot pressing process begins, the hot press furnace is flushed with inert gas 3-5 times to remove oxygen from the furnace. The processing flow is as follows: First, the mating surfaces are machined using a lathe, and then the mating surfaces are polished to ensure that the mating surfaces are flat and free of machining marks. The surface roughness Ra = 0.05μm-1.6μm.

2. The method for preparing a graded functional titanium alloy according to claim 1, characterized in that, The fit tolerance between the different grades and microstructures of the titanium alloys is less than 0.5 mm.

3. The method for preparing a graded functional titanium alloy according to claim 1, characterized in that, To remove surface oil stains, petroleum ether and alcohol are used to clean the titanium alloy sequentially until the bonding surface is free of contaminants.

4. The method for preparing a graded functional titanium alloy according to claim 1, characterized in that, During the docking and assembly process, it is ensured that the materials do not deform.

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