A preparation method of ultrafine multi-layered TC4 titanium alloy

Abstract

The present invention relates to a method for preparing a TC4 titanium alloy with an ultrafine multi-layered structure, and more particularly to a method for obtaining an ultrafine multi-layered structure and excellent strong plasticity in the TC4 titanium alloy, belonging to the field of metal material structural performance optimization. The method comprises preparing a TC4 titanium alloy preform, performing surface treatment on the TC4 titanium alloy preform, performing pretreatment after the surface treatment, performing multiple hot rolling deformations on the pretreated TC4 titanium alloy preform by rolling to obtain a hot-rolled and deformed TC4 titanium alloy preform, and subjecting the obtained hot-rolled and deformed TC4 titanium alloy preform to a solution quenching treatment to obtain a TC4 titanium alloy with an ultrafine multi-layered structure.

Description

Technical Field

[0001] The present invention relates to a preparation method of a TC4 titanium alloy with an ultrafine multi-layer structure, and in particular to a method for obtaining an ultrafine multi-layer structure and excellent strength and plasticity in the TC4 titanium alloy, belonging to the field of metal material structural performance optimization. Background Art

[0002] In engineering applications, lightweighting components is key to reducing energy consumption and carbon dioxide emissions. One of the primary approaches to achieving this is to increase the use of structural materials with high specific strength. Among numerous structural materials, titanium alloys have been extensively studied due to their high specific strength, toughness, and corrosion resistance. TC4 titanium alloy, among others, offers excellent overall performance and is the most widely used. Therefore, how to ensure its excellent mechanical properties and maximize its application range are pressing challenges in achieving lightweight components.

[0003] TC4 titanium alloy is a dual-phase titanium alloy that can be heat-treated and strengthened. However, the microstructure of TC4 titanium alloy regulated by heat treatment often has relatively coarse grains. For TC4 titanium alloy, the coarse microstructure makes it difficult for it to have excellent mechanical properties. Microstructure refinement is an important way to improve the mechanical properties of TC4 titanium alloy. The thermomechanical treatment process that combines deformation and heat treatment can regulate the morphology, size, percentage and distribution of each phase in TC4 titanium alloy, thereby making it have better mechanical properties. However, since the microstructure of TC4 titanium alloy before deformation is often relatively coarse, subsequent thermomechanical treatment is difficult to effectively refine it, which limits the improvement of the mechanical properties of TC4 titanium alloy. Therefore, how to make the microstructure of TC4 titanium alloy before deformation as fine as possible and to make the alloy have excellent mechanical properties through subsequent appropriate thermomechanical treatment process is a problem that needs to be solved in this field. Summary of the Invention

[0004] The technical problem solved by the present invention is to overcome the shortcomings of the existing preparation technology and provide a preparation method of an ultrafine multi-layered TC4 titanium alloy.

[0005] The technical solution of the present invention is:

[0006] A method for preparing an ultrafine multi-layered TC4 titanium alloy, wherein the TC4 titanium alloy prepared by the method has an ultrafine multi-layered structure and excellent strength and plasticity;

[0007] The steps of the method include:

[0008] The first step is to prepare a TC4 titanium alloy blank. The specific method is as follows: TC4 fine powder is filled in a cemented carbide mold, and then the cemented carbide mold filled with TC4 fine powder is sintered to obtain a TC4 titanium alloy preformed blank; the diameter of the cemented carbide mold is 20-30 mm, preferably 25 mm, the average particle size of the TC4 fine powder is 30-35 μm, preferably 33 μm, and when the diameter of the cemented carbide mold is 25 mm, the mass of the filled TC4 fine powder is 20-25 g; The sintering furnace used during sintering is a DC power supply rapid hot pressing sintering furnace. The sintering temperature is 450-650°C, preferably 550°C, and the sintering pressure is 280-450 MPa, preferably 400 MPa. After sintering, the TC4 fine powder is consolidated and formed. The diameter of the formed TC4 titanium alloy preform is 20-30 mm, preferably 25 mm, and the height is 10.5-12.5 mm. During the sintering process, the TC4 fine powder can maintain its original size.

[0009] In the second step, the TC4 titanium alloy preform obtained in the first step is subjected to surface treatment, and after the surface treatment is completed, a pretreatment is performed, wherein the surface treatment method comprises: turning the surface of the TC4 titanium alloy preform to a bright finish to remove surface defects, and then cutting the TC4 titanium alloy preform in half along the diameter direction by wire cutting; and the pretreatment method comprises: heating the cut TC4 titanium alloy preform to 850-900° C. and holding the temperature for 8-13 minutes;

[0010] The third step is to perform multiple hot rolling deformation on the TC4 titanium alloy preformed blank after the pretreatment in the second step by rolling to obtain a TC4 titanium alloy blank, wherein the hot rolling deformation amount during the multiple hot rolling deformation is 75%-85%, preferably 80%, and the hot rolling deformation is completed in 4-6 passes, preferably 5 passes, and the sample is returned to the furnace for 4-6 minutes between each pass. After the last hot rolling pass, the sample is air-cooled to room temperature;

[0011] In the fourth step, the TC4 titanium alloy blank obtained in the third step is subjected to a solution quenching treatment to obtain a TC4 titanium alloy having an ultrafine multi-layered structure. The method for the solution quenching treatment is as follows: a tensile specimen of the TC4 titanium alloy blank is cut from a hot-rolled plate (the length direction of the specimen is parallel to the rolling direction), the cut tensile specimen is placed in a glass tube, argon is introduced into the tube and then sealed, and the sealed glass tube is heated to 30-50° C. below the phase transition point of the TC4 titanium alloy, kept at this temperature for 5-30 minutes, and then water-cooled to room temperature;

[0012] The room temperature mechanical properties test of the obtained TC4 titanium alloy with ultrafine multi-layer structure showed that the tensile strength was not less than 1100 MPa, the elongation was not less than 20%, and the tensile rate during the room temperature mechanical properties test was 5×10 - 4 s-1 ;

[0013] The microstructure test of the obtained TC4 titanium alloy with ultrafine multi-level structure showed that the ultrafine scale initial α phase (α p ), original β grains (β p ) and martensite (α'), dispersed β phase and nano-twin (Nano-twin) composed of a multi-level structure.

[0014] Beneficial effects

[0015] The present invention provides a method for obtaining an ultrafine multi-layered structure and excellent strong plasticity in TC4 titanium alloy. The method uses a DC power supply to rapidly hot-press sinter fine alloy powder of a certain size to form a sintered shape, then the preformed body is subjected to multiple hot rolling deformations, and then the hot-rolled sample is subjected to a solid solution quenching treatment near the phase transition point. The ultrafine-scale structure obtained by controlling the powder particle size and hot rolling parameters is more conducive to regulating the microstructure of the alloy during the heat treatment after deformation. After the subsequent solid solution quenching, the alloy is formed by ultrafine-scale α p , β p The multi-layered structure consists of a α' phase, a dispersed β phase, and a Nano-twin phase. Furthermore, the TC4 titanium alloy with this structure achieves a tensile strength of 1147 MPa and an elongation of 20.86%. This invention provides a simple method for achieving excellent strength and ductility in the most widely used TC4 titanium alloy, belonging to the field of metal material structural performance optimization technology.

[0016] The rapid heating and cooling at low temperatures during the sintering process prevents the grains from growing in time, which is conducive to obtaining an ideal structure at a smaller scale, thereby giving the alloy excellent mechanical properties.

[0017] Compared with traditional preparation technology, the present invention controls the particle size of the preform matrix through fine powder and low-temperature and high-pressure sintering process. Subsequently, short-term multi-pass hot rolling is carried out in the high-temperature dual-phase region to eliminate sintering defects in the preform on the one hand and further refine the matrix structure on the other hand. In addition, the structure after hot rolling has a high deformation energy storage, and high deformation energy storage can provide a driving force for the subsequent complete recrystallization of the α phase and β phase. This structure can finely control the α phase according to the solution temperature, holding time and cooling method during the subsequent solution quenching heat treatment. p The size and percentage of β pFinally, a tensile specimen (length along the rolling direction) was cut from the hot-rolled plate, and after vacuum sealing, solution treatment was performed at 850-8950°C for 5830 minutes to adjust the initial α phase and β phase percentages. After removal, the specimen was water-cooled to room temperature to obtain a lamellar α' structure. Due to its low stacking fault energy, a large number of Nano-twins will be formed after solution quenching. The present invention can form an ultra-fine multi-layered structure in TC4 titanium alloy, namely α p , β p and α', diffusely distributed β phase and a large number of Nano-twin. Ultrafine scale equiaxed α p The high strength of TC4 alloy is improved by the presence of α, α' and dispersed nano / ultrafine β phase, while a large amount of Nano-twin improves its plasticity. p The good interfacial compatibility between α' and TC4 titanium alloys also effectively improves the alloy's plasticity. Compared to recently reported TC4 titanium alloys and composite materials based on them, the TC4 titanium alloy prepared by this invention exhibits further enhanced performance, promising to further expand its application range and ultimately achieve the goal of lightweight components within a certain range. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 This is a backscattered electron imaging (BSE) image of the sample obtained in the embodiment of the present invention. The equiaxed structure is α p , the lamellar tissue is α';

[0019] Figure 2 is the electron backscatter diffraction (EBSD) grain boundary and inverse pole figure (IPF) of the sample obtained in the embodiment of the present invention, A and B represent α p and α' tissue;

[0020] Figure 3 is a histogram of misorientation obtained from the EBSD data of a sample prepared in an embodiment of the present invention;

[0021] Figure 4 This is a transmission electron (TEM) image of the β phase in the sample obtained in the example of the present invention;

[0022] Figure 5 This is a transmission electron microscope (TEM) image of the Nano-twin in the sample obtained in the example of the present invention;

[0023] Figure 6 It is the room temperature tensile curve of the sample prepared in the example of the present invention. DETAILED DESCRIPTION

[0024] In order to make the objectives and technical solutions of the present invention clearer, the technical solutions of the present invention will be fully described below with reference to specific examples. It should be noted that this example is only a part of the embodiments of the present invention. Based on the embodiments of the present invention, other examples obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0025] In the following embodiments:

[0026] (1) Tensile testing equipment: Zwick Z2.5 TH single-column tabletop electronic universal testing machine (manufactured by ZwickRoell Group, Germany, and equipped with a laser X tens laser extensometer);

[0027] (2) IPF image: Electron backscatter diffraction (EBSD) data were processed using Channel 5 software to obtain grain boundaries and inverse pole figures;

[0028] (3) SEM test: The scanning electron microscope (SEM) was used with a JEOL JSM 7200F instrument.

[0029] (4) TEM test: The transmission electron microscope (TEM) was used as FEI Tecnai G2 F20.

[0030] Example: The process for preparing an ultrafine multi-layer structure in TC4 titanium alloy includes the following steps:

[0031] (1) Weigh 20 g of TC4 titanium alloy powder with an average particle size of 33 μm and place it in a cemented carbide mold with a diameter of 25 mm. The powder is consolidated and formed in a DC power supply rapid hot pressing sintering furnace using a low-temperature high-pressure sintering process at 500°C / 400 MPa to obtain a preform with a diameter of 25 mm and a height of 10.5 mm.

[0032] (2) The surface of the sintered preform body was milled clean on a lathe, and one half was cut in half along the diameter direction by wire cutting. One half was heated to the high temperature dual phase region at 900°C and kept warm for 8 minutes. The high temperature plastic deformation was carried out 5 times by rolling until the deformation was 80%. After rolling, it was placed on the ground and air-cooled to room temperature. The backscattered electron imaging (BSE) image of the obtained sample is shown as follows: Figure 1 As shown, the equiaxed structure is α p , the lamellar structure is α'; the electron backscatter diffraction (EBSD) grain boundary and inverse pole figure (IPF) of the sample are as follows Figure 2 As shown, A and B represent α p and α' structure; the misorientation histogram obtained from the EBSD data of the sample is shown in Figure 3 As shown, the transmission electron (TEM) image of the β phase in the sample is as follows Figure 4 As shown, the transmission electron microscopy (TEM) image of Nano-twin in the sample is as follows Figure 5 The room temperature tensile curve of the sample is shown in Figure 6 shown.

[0033] (3) Room temperature tensile specimens were cut from the hot-rolled plates, sealed in a glass tube, heated to 950 °C for 25 min, and then taken out and cooled to room temperature. Tensile tests were then performed at room temperature with a strain rate of 5*10 -4 s -1 .

[0034] Tests have shown that the TC4 titanium alloy prepared by the powder metallurgy and subsequent thermomechanical treatment method of the present invention has a multi-layer structure consisting of ultrafine initial α phase, original β grains and martensite, dispersed β phase and twins, and the room temperature tensile strength can reach 1147 MPa and the elongation is 20.86%.

[0035] The above embodiments are only for illustrating the present invention and do not limit the technical solutions of the present invention. Those skilled in the art may modify or replace the present invention to a certain extent, and any modification that does not deviate from the spirit of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A method for preparing an ultrafine multi-layered TC4 titanium alloy, characterized by the following steps: include: The first step is to prepare a TC4 titanium alloy preform; In the second step, the TC4 titanium alloy preform obtained in the first step is subjected to surface treatment, and a pretreatment is performed after the surface treatment is completed; The third step is to perform multiple hot rolling deformation on the TC4 titanium alloy preform body pretreated in the second step by rolling to obtain a hot-rolled TC4 titanium alloy body; The fourth step is to perform a solution quenching treatment on the hot-rolled and deformed TC4 titanium alloy blank obtained in the third step to obtain a TC4 titanium alloy with an ultrafine multi-layered structure; In the first step, the specific method for preparing the TC4 titanium alloy preform is: filling TC4 fine powder in a cemented carbide mold, and then sintering the cemented carbide mold filled with TC4 fine powder to obtain the TC4 titanium alloy preform; The diameter of the cemented carbide die is 20-30 mm, and the average particle size of the TC4 fine powder is 30-35 μm; When the diameter of the cemented carbide die is 25 mm, the mass of the TC4 fine powder filled is 20-25 g; The sintering furnace used during sintering is a DC power supply rapid hot pressing sintering furnace. The sintering temperature is 450-650°C and the sintering pressure is 280-450 MPa. After sintering, the TC4 fine powder is consolidated and formed. The diameter of the formed TC4 titanium alloy preform is 20-30 mm and the height is 10.5-12.5 mm. During the sintering process, the TC4 fine powder can maintain its original size. In the second step, the surface treatment method of the TC4 titanium alloy preform is as follows: the surface of the TC4 titanium alloy preform is turned to be bright to remove surface defects, and then the TC4 titanium alloy preform is cut in half along the diameter direction by wire cutting; In the second step, the pretreatment method is as follows: heating the cut TC4 titanium alloy preform to 850-900° C. and keeping the temperature for 8-13 minutes; In the third step, the hot rolling deformation is 75%-85% when multiple passes are performed, and the hot rolling deformation is completed in 4-6 passes. The sample is returned to the furnace for 4-6 minutes between each pass. After the last hot rolling pass, the sample is air-cooled to room temperature. In the fourth step, the method for performing the solution quenching treatment is as follows: a tensile specimen of the TC4 titanium alloy blank is cut from the hot-rolled plate, with the length direction of the specimen parallel to the rolling direction, the cut tensile specimen is placed in a glass tube, argon is introduced and then sealed, and then the sealed glass tube is heated to 30-50°C below the phase transition point of the TC4 titanium alloy, kept warm for 5-30 minutes, and then water-cooled to room temperature.

Images