CN114672682B

CN114672682B - High-performance powder metallurgy titanium alloy part and preparation method thereof

Info

Publication number: CN114672682B
Application number: CN202210169605.8A
Authority: CN
Inventors: 路新; 潘宇; 况帆
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2022-02-23
Filing date: 2022-02-23
Publication date: 2023-04-07
Anticipated expiration: 2042-02-23
Also published as: CN114672682A

Abstract

The invention provides a high-performance powder metallurgy titanium alloy part and a preparation method thereof, wherein the high-performance powder metallurgy titanium alloy part is structured by a matrix phase and a grain boundary phase distributed among the matrix phases; wherein the matrix phase is an alpha bundle structure; the grain boundary phase is alpha-Ti and is in a discontinuous short rod shape; the length of the grain boundary phase is 5-15 mu m, the length-diameter ratio is 3-8: 1. the titanium alloy product has the structure that discontinuous short rod-shaped grain boundary phase alpha-Ti is formed, and a compact structure with smaller alpha bundle set is formed, so that the density and the toughness of the titanium alloy product are improved, and the high-density, high-toughness and high-toughness powder metallurgy titanium alloy product is obtained.

Description

High-performance powder metallurgy titanium alloy part and preparation method thereof

Technical Field

The invention relates to the technical field of powder metallurgy, in particular to a high-performance powder metallurgy titanium alloy part and a preparation method thereof.

Background

Titanium and titanium alloys have been widely used in the fields of automobiles, aerospace, ocean engineering, biomedical and the like due to their excellent properties of small density, high specific strength, good heat resistance and corrosion resistance and the like, and are known as "strategic metals". The traditional titanium material is generally prepared by a casting-forging process through multiple casting of a vacuum consumable furnace, multiple times of cogging and forging, thermal deformation, thermal treatment and deep processing, and has the disadvantages of long production flow, complex process, high energy consumption and extremely low material utilization rate, so that the cost of the titanium material is high, and the wide application of titanium alloy parts is restricted. The hot processing of the powder blank can avoid solid-liquid phase change in the smelting process, greatly simplify the preparation process flow, solve the problems of easy segregation, thick structure and the like of the alloy, and is the most powerful technical approach for realizing the low-cost preparation of high-performance titanium alloy workpieces.

The preparation method of the powder metallurgy titanium alloy is divided into two methods, namely a prealloying method and a mixed element method. The prealloying method is characterized in that titanium sponge and alloy are smelted into ingots, and then the ingots are prepared by an atomization powder preparation technology, the preparation process is complex, the cost is high, and meanwhile, the powder is prone to defects such as hollow powder and satellite powder. The mixed element method is to mix titanium powder with other alloy element powder, then to cold press and form, sinter and densify to obtain high performance titanium alloy product with high freedom of element system, controllable powder granularity and high performanceThe method has the advantages of short process flow, low cost and the like, but has the problems of high content of interstitial atoms and insufficient sintering driving force, and influences the mechanical property of the titanium alloy product. The common raw material of the titanium alloy mixed element method is titanium hydride powder, and H exists in the powder in the dehydrogenation process ₂ And O is released, so that an oxide film on the surface of the powder can be purified, and the content of interstitial elements of a workpiece is reduced. Due to the hydrogen brittleness characteristic, the powder has small granularity, and is partially crushed in the pressing forming process to fill in gaps, so that a pressed compact with high density is obtained. Meanwhile, in the sintering densification process, active hydrogen can pin the grain boundary, reduce the phase change temperature of the titanium alloy and promote the diffusion of titanium atoms, thereby being beneficial to improving the density of a sintered blank and obtaining a uniform fine grain structure. In addition, when the mixed powder of titanium hydride and alloy is used as a raw material for sintering, two processes of synchronous dehydrogenation and uniform element diffusion exist, so that the driving force provided by the conventional pressureless sintering process is insufficient, and a high-density titanium alloy product is difficult to obtain. The traditional method for improving the compactness mainly comprises the steps of improving the sintering temperature (more than or equal to 1300 ℃) or prolonging the heat preservation time (3-6 h), which can cause the abnormal growth of the original beta phase and influence the mechanical property of the titanium alloy part. In addition, the density of the titanium alloy part is improved through the hot isostatic pressing process, but the manufacturing cost is greatly increased.

Therefore, how to prepare a high-density high-toughness titanium alloy part by using low-cost titanium hydride powder as a raw material through a short process is a core problem to be solved urgently at present.

Disclosure of Invention

Aiming at the defects in the prior art, the invention mainly aims to provide a high-performance powder metallurgy titanium alloy part and a preparation method thereof.

To achieve the above object, according to a first aspect of the present invention, there is provided a high performance powder metallurgy titanium alloy article.

The structure of the high-performance powder metallurgy titanium alloy part is a matrix phase and a grain boundary phase distributed among the matrix phases; wherein, the first and the second end of the pipe are connected with each other,

the matrix phase is an alpha bundle structure;

the grain boundary phase is alpha-Ti and is in a discontinuous short rod shape;

the length of the grain boundary phase is 5-15 mu m, the length-diameter ratio is 3-8: 1.

further, the alpha beam set structure comprises mutually parallel elongated alpha-Ti sheets and residual beta-Ti sheets distributed among the elongated alpha-Ti sheets;

the length of the long alpha-Ti sheet layer is 8-20 mu m.

Furthermore, the sizes of the alpha beam set structures with the same orientation are all 5-20 mu m.

Furthermore, the density of the product is more than or equal to 99.8%, the oxygen content is 0.21-0.25 wt.%, the room-temperature tensile strength is 1179-1260 MPa, and the elongation is 12.6-16%.

In order to achieve the above object, according to a second aspect of the present invention, a method for preparing a high performance powder metallurgy titanium alloy article is provided.

The preparation method of the high-performance powder metallurgy titanium alloy part comprises the following steps:

mixing titanium hydride powder and alloy powder, and then sequentially carrying out cold isostatic pressing, sintering and hot extrusion treatment to obtain the high-performance powder metallurgy titanium alloy part;

wherein, the sintering treatment is carried out under the protective atmosphere, and the sintering process is as follows: heating the powder pressed compact obtained by the cold isostatic pressing to 600-650 ℃ from room temperature at the speed of 1-5 ℃/min, and preserving heat for 1-2 h; then heating to 1100-1250 ℃ at the speed of 1-5 ℃/min, and preserving the heat for 1-4 h; then the temperature is reduced to 800 ℃ at the speed of 1-5 ℃/min, and the furnace is cooled after the temperature is kept for 1-4 h.

Further, the cold isostatic pressing process parameters are as follows: the pressure maintaining pressure is 150-300 MPa, and the pressure maintaining time is 5-60 min.

Further, the hot extrusion treatment process comprises the following steps: heating the sintered blank obtained by the sintering treatment to 1125-1175 ℃ at the speed of 100 ℃/min, preserving the heat for 1-10 min, quickly transferring the sintered blank to a die preheated to 400-500 ℃, and quickly extruding the sintered blank at the extrusion speed of 15-25 mm/s, wherein the extrusion ratio is 9-16: and 1, demolding after the mold is cooled to room temperature.

Further, the hot extrusion treatment is carried out in a sealed glove box under the protection of inert gas, wherein the oxygen content of the box body is less than or equal to 100ppm.

Further, mixing the titanium hydride powder and the alloy powder by using a double-roller ball mill; wherein the mixing speed is 70-200 rpm, and the mixing time is 15-25 h;

preferably, the mixing process adopts a mixing mode of forward rotation for 30min, stopping for 5min and then reverse rotation for 30 min.

Further, the titanium hydride powder has a particle size of 5 to 60 μm and a hydrogen content of 3.7 to 3.95wt.%; the granularity of the alloy powder is 5-48 mu m;

preferably, the alloy powder is 60Al40V powder, or 60Al40V powder, al powder, zr powder, and Mo powder.

Different from the multi-pass casting and machining of the traditional casting alloying, the invention adopts the powder billet hot working process to produce the titanium alloy finished piece, has the advantages of simple process, low cost and the like, and the contents of the interstitial elements and the strong plasticity of the finished piece exceed the level of the traditional powder metallurgy titanium alloy. One of the key factors for the present invention to achieve the above results is the specific sintering process. Specifically, the invention takes hydrogen as a temporary alloy element of the powder blank, and hydrogen removal can occur in the sintering process, and the following effects can be achieved by utilizing the process. Firstly, the purpose of purifying the powder is achieved by utilizing the carrying effect of hydrogen on impurities on the surface of the powder, particularly a surface passivation film, in the removing process. Secondly, in the sintering dehydrogenation process, due to the decomposition of titanium hydride and the diffusion effect of hydrogen atoms, interstitial solid solution of hydrogen is generated on the surface of titanium powder, so that the lattice constant of titanium is changed, the lattice distortion energy is increased, the vacancy concentration and dislocation in the titanium crystal are increased, the surface activity of titanium is improved, and the free energy in the sintering process is reduced. Thirdly, the hydrogen element accelerates the diffusion of alloy elements and has regulation and control effects on the uniformity of the structure, the size of crystal grains and the densification process. Based on the characteristics, the sintering conditions are crucial, and the sintering conditions are as follows: the temperature is 1100-1250 ℃, the heat preservation time is 1-4 h, and the specific sintering process is as follows: heating the powder pressed blank obtained by cold isostatic pressing from room temperature to 600-650 ℃ at the speed of 1-5 ℃/min, and preserving heat for 1-2 h; then heating to 1100-1250 ℃ at the speed of 1-5 ℃/min, and preserving the heat for 1-4 h; then the temperature is reduced to 800 ℃ at the speed of 1-5 ℃/min, and the furnace is cooled after the temperature is preserved for 1-4 h, thereby obtaining a sintered blank with the density of 85-92%. If the sintering temperature is too low or the sintering time is too short, the dehydrogenation is incomplete, the diffusion of alloy powder elements is uneven, and the fracture phenomenon can occur in the thermal deformation process due to insufficient density of a sintered blank. If the sintering temperature is too high or the sintering time is too long, coarse and continuous crystal boundary alpha phase is generated, and the mechanical property of a finished piece is influenced.

In addition, the invention is matched with hot extrusion treatment after sintering, and the strong three-dimensional pressure stress provided in the hot extrusion process can effectively inhibit the cracking tendency of the low-density sintered part, completely close the hole under large deformation and realize tissue recrystallization refinement. The hot extrusion is a common plastic processing method, can complete the full densification of a sintered blank, the material is in a three-dimensional compressive stress state during deformation, the integral plastic deformation is large, and the high-dimensional precision one-step forming of bars and pipes with special shapes is easy to realize. Meanwhile, the extrusion process can provide enough recrystallization driving force, the deformation strengthening effect is exerted, and a new idea is provided for realizing high-performance densification forming of the titanium hydride powder blank.

On the other hand, the preferable hot pressing condition is organically matched with the specific sintering parameter, so that a titanium alloy part with a lamellar structure and better matching plasticity can be prepared. The basket structure (lamellar structure) has higher strength than the equiaxed structure common in two-phase titanium alloys, but the titanium alloy plasticity is deteriorated by the oversized alpha/beta lamellae and the thick and continuous flat grain boundary alpha phase. Therefore, the size of the lamellar bundle, the thickness of the lamellar and the shape of the alpha crystal boundary can be regulated and controlled, and the strong plasticity of the two-phase titanium alloy can be effectively improved. The grain size also has great influence on the mechanical property, the improvement effect of hydrogen on the structure can be fully exerted through short-time heat preservation at lower temperature, the original beta grains can be effectively prevented from growing due to the existence of holes in a non-fully-compact sintering blank, and the structure can be promoted to be recrystallized and refined by matching with proper processing temperature and deformation in the subsequent hot processing process. According to the Hall-Petch effect, the smaller the size of the lath with the same orientation in the alpha beam concentration of the lamellar structure, the shorter the effective slip length of the dislocation and the higher the strength. According to the invention, the density and the hot extrusion parameters of the sintered blank are regulated and controlled, the grain boundary alpha is intermittently connected (as shown by an arrow in figure 2), a compact structure with a small alpha beam set is formed, and meanwhile, the lath with the anisotropic characteristic has stronger capability of inhibiting crack propagation and improves the fracture toughness.

Experiments prove that the process obtains a non-fully-dense sintered blank with low impurity content by selecting the types of raw materials, controlling the alloy structure, optimizing the preparation process and various parameters, specifically utilizing the purification of hydrogen on titanium alloy powder, the promotion of element diffusion and the regulation and control capability of the structure, and completing the full densification of a titanium alloy workpiece by combining with the subsequent hot extrusion treatment; recrystallization is carried out in the hot extrusion process to generate discontinuous crystal boundary alpha and a smaller alpha beam set, and finally a powder metallurgy titanium alloy part with uniform and fine structure and excellent mechanical property is obtained, wherein the compactness of the titanium alloy part is more than or equal to 99.8 percent, the oxygen content is lower than 0.25wt.%, the room-temperature tensile strength is 1179-1260 MPa, and the elongation is 12.6-16 percent, so that the problems of coarse structure grains, high interstitial element content, insufficient mechanical property and the like of the titanium alloy part in the prior art are solved.

The beneficial effects of the invention include:

(1) The titanium alloy part with a specific discontinuous crystal boundary alpha short rod and a small-size alpha/beta lamellar structure is designed and prepared, and the room-temperature mechanical property of the titanium alloy part is higher than the industrial standard.

(2) A powder metallurgy titanium alloy preparation process with the cooperation of a not-fully-compact sintered blank and hot extrusion is designed, and the preparation of the high-strength and high-toughness titanium alloy is realized by utilizing the promoting effects of hydrogen elements on grain refinement, densification and the like of the titanium alloy.

(3) By using titanium hydride powder as a raw material and adopting a powder blank hot working technology, high-efficiency preparation of high-performance titanium alloy workpieces can be realized, and the cost can be reduced by about 40 percent compared with that of the titanium hydride powder. Compared with the prior art of fusion casting alloying, hot isostatic pressing and the like, the titanium alloy finished piece has low content of interstitial elements, short flow and high efficiency, and is easy to realize the expansion of the application field of the titanium alloy.

Drawings

Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for purposes of illustrating the preferred embodiments and are not to be construed as limiting the invention. Also, like reference numerals are used to refer to like parts throughout the drawings. In the drawings:

FIG. 1 is a microstructure photograph of a Ti-6Al-4V alloy after sintering in example 1 according to the present invention;

FIG. 2 is a photograph showing the microstructure of the Ti-6Al-4V alloy of example 1 according to the present invention after hot extrusion.

Detailed Description

Exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be embodied in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

According to the specific embodiment of the invention, the preparation method of the high-performance powder metallurgy titanium alloy part is provided, the density of the prepared titanium alloy part is not less than 99.8%, the oxygen content is lower than 0.25wt.%, the room-temperature tensile strength is 1179-1260 MPa, and the elongation is 12.6-16%, so that the problems of large texture crystal grains, high interstitial element content, insufficient mechanical properties and the like of the titanium alloy part in the prior art are solved.

s1: preparing raw materials, weighing titanium hydride (TiH) with proper particle size ₂ ) The powder and the corresponding master alloy powder are used as raw materials.

At the position ofIn the step, powder with proper grain diameter is selected as raw material, tiH ₂ The particle size of the powder is 5-60 mu m, and the hydrogen content is 3.7-3.95 wt.%; the grain size of the alloy powder is 5-48 mu m. The titanium hydride cost is increased and the press forming is difficult by selecting the powder with too small particle size, but the sintering compactness is reduced due to the reduction of the powder activity by selecting the powder with too large particle size, and the alloy powder elements are difficult to diffuse uniformly.

The alloy powder can comprise TC4 (Ti-6 Al-4V), TA15 (Ti-6.5 Al-2Zr-1 Mo-1V), TB2 (Ti-5 Mo-5V-8Cr-3 Al) and other multi-grade powder.

In the present invention, the alloy powder may be 60Al40V powder, or 60Al40V powder, al powder, zr powder, and Mo powder.

S2: and (3) mixing powder, namely mixing (for example, mechanically mixing) raw material powder of each composition according to the target titanium alloy component to obtain uniform mixed powder.

In order to simplify the preparation process, the powder mixing process does not need gas protection based on the cleaning effect of the subsequent hydrogen on the titanium matrix, and meanwhile, the mixed powder prepared by ball milling does not need screening treatment. Wherein, a double-roller ball mill is adopted, the mixing speed is 70-200 rpm, and the actual mixing time is 15-25 h.

In order to obtain uniformly mixed powder, a material mixing mode of forward rotation for 30min, stopping rotation for 5min and then reverse rotation for 30min can be adopted in the material mixing process, namely, the powder mixing is carried out alternately by a forward roller and a reverse roller and is supplemented with zirconia grinding balls, and then the lower rotating speed and certain interval time are adopted, so that the uniform mixed powder is obtained while the powder is not subjected to cold welding.

S3: and (4) forming, filling the mixed powder into a mold, and preparing a powder compact through cold isostatic pressing.

In the step, the pressure maintaining pressure is 150-300 MPa, and the pressure maintaining time is 5-60 min. Two stages of particle rearrangement and adjacent powder plastic deformation mainly exist in the powder pressing process, and titanium hydride particles are brittle, low in strength and poor in fluidity, so that uniform pressing pressure of cold isostatic pressing needs to be kept for a certain pressure maintaining time, and the powder can be guaranteed to obtain high green compact density under low pressure.

S4: and sintering, namely sintering the powder pressed compact to obtain a dehydrogenated not-fully-compact titanium alloy sintered compact.

In the step, the sintering process is carried out under the protection of inert gas, and the specific sintering process is as follows: heating the powder pressed compact from room temperature to 600-650 ℃ at the speed of 2-5 ℃/min, preserving the temperature for 1-2 h, and carrying out first-stage sintering dehydrogenation; heating to 1100-1250 ℃ at the speed of 2-5 ℃/min, preserving the heat for 1-4 h, and carrying out second-stage sintering; then the temperature is reduced to 800 ℃ at the speed of 2-5 ℃/min, and the furnace is cooled after the temperature is kept for 1-4 h.

If the sintering temperature is too low, the added alloy elements are not uniformly diffused, the enrichment phenomenon of individual elements exists, and meanwhile, the compactness of the blank is too low, so that the feasibility of subsequent hot extrusion is influenced; if the sintering temperature is too high, the beta phase is very different and grows, which is not favorable for the subsequent recrystallization.

S5: and (4) hot working, namely performing hot extrusion treatment on the titanium alloy sintered blank to obtain a titanium alloy workpiece.

In the step, the hot extrusion process is carried out in a sealed glove box with the box body oxygen content less than or equal to 100ppm, and high-purity argon with the purity more than or equal to 99.999 percent is used for protection. Heating the titanium alloy sintered blank to 1125-1175 ℃ at the speed of 100 ℃/min by means of electromagnetic induction heating or discharge plasma heating, preserving the heat for 1-10 min, and preventing the crystal grains from growing on the premise of ensuring the uniform heating of the blank. And (3) quickly transferring the heated mixture into an H13 die, wherein the die needs to be preheated to 400-500 ℃, and the influence on the tissue performance caused by an overlarge temperature gradient along the diameter direction in the extrusion process is prevented. Then rapidly extruding at an extrusion speed of 15-25 mm/s with an extrusion ratio of 9-16, and demoulding after the mould is cooled to room temperature.

The high performance powder metallurgy titanium alloy article and the method of making the same of the present invention are described in detail below with reference to specific examples.

Example 1:

s1: preparing raw materials, and weighing titanium hydride powder (less than or equal to 58 mu m and hydrogen content of 3.80 wt.%) and 60Al40V alloy powder (less than or equal to 30 mu m) according to the proportion of alloy components.

S2: and mixing powder, namely filling the raw materials into a mixing bottle according to a proportion, and mixing at room temperature by using a double-roll ball mill, wherein a grinding ball is a zirconia ball with the diameter of 6mm, the mixing speed is 70rpm, and the mixing time is 22h. Wherein, the whole material mixing process always adopts a positive rotation or reverse rotation mode.

S3: forming, namely filling the uniformly mixed powder into a rubber sheath with the inner diameter of 65mm and the height of 120mm, and continuously compacting during powder filling; and (3) carrying out cold isostatic pressing forming under the pressure of 250MPa for 10min.

S4: sintering, namely sintering the powder pressed compact under the protection of argon atmosphere, wherein the specific sintering process is as follows: heating to 600 ℃ from room temperature at a speed of 5 ℃/min, preserving heat for 2h, and sintering at the first stage; raising the temperature to 1200 ℃ at the speed of 5 ℃/min, keeping the temperature for 2 hours, and carrying out second-stage sintering; cooling to 800 deg.C at 5 deg.C/min, maintaining for 2 hr, and cooling.

S5: and (3) hot extrusion, namely heating the sintered blank to 1150 ℃, quickly placing the sintered blank into a hot extrusion die preheated to 450 ℃, and extruding (extruding a bar with the diameter of 12 mm) at the extrusion ratio of 16.

Examples 2 to 5 all adopt the same preparation process as example 1, except for the raw material powder parameters, the powder mixing, forming, sintering and hot extrusion process parameters, etc., and the preparation process parameters in examples 1 to 5 are summarized as detailed in tables 1 to 3.

TABLE 1 summary of the raw material powder parameters in examples 1-5

Remarking:

in each of examples 1 to 5, each of the raw material powders was weighed in accordance with the required alloy ratio of the obtained article.

Table 2 summary of powder mixing process parameters in examples 1-5

TABLE 3 summary of Cold isostatic pressing, sintering, and Hot extrusion Process parameters for examples 1-5

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Performance comparison experiments will be performed on the titanium alloy articles prepared by the preparation methods of examples 1 to 5 and the titanium alloy articles prepared by other conventional preparation processes.

1. Test object

The titanium alloy articles prepared in examples 1-5 and the titanium alloy articles prepared in comparative examples 1-3, wherein:

comparative example 1:

comparative example 1 the raw material preparation and powder mixing stages were carried out according to the preparation process of example 1. The difference lies in that: and (3) putting the uniformly mixed powder into a metal sheath under the vibration condition, heating to 700 ℃ in a vacuum degree of 3Pa, preserving heat for 5 hours, carrying out hot isostatic pressing treatment after vacuum welding, cooling to below 300 ℃ along with a furnace, taking out the metal sheath, and removing the sheath in a machining mode, wherein the hot isostatic pressing temperature is 1000 ℃, the pressure is 120MPa, and the heat preservation and pressure preservation time is 2 hours.

Comparative example 2:

comparative example 2 the raw material preparation, powder mixing, cold isostatic pressing stages and hot extrusion were carried out according to the preparation process in example 1. The differences are that: during sintering, the temperature is raised to 600 ℃ from room temperature at the speed of 5 ℃/min, and the temperature is kept for 2h; and then raising the temperature to 1000 ℃ at the speed of 5 ℃/min, keeping the temperature for 2h, carrying out second-stage sintering, reducing the temperature to 800 ℃ at the speed of 5 ℃/min, keeping the temperature for 2h again, and then cooling along with the furnace.

Comparative example 3:

the preparation of the raw materials, the powder mixing, the cold isostatic pressing stage and the hot extrusion in comparative example 3 were carried out according to the preparation process in example 1. The difference lies in that: during sintering, the temperature is raised to 600 ℃ from room temperature at the speed of 5 ℃/min, and the temperature is kept for 2h; and then raising the temperature to 1350 ℃ at the speed of 5 ℃/min, preserving the heat for 2h, carrying out second-stage sintering, reducing the temperature to 800 ℃ at the speed of 5 ℃/min, preserving the heat for 2h again, and then cooling along with the furnace.

2. Experimental method

The titanium alloy articles prepared in examples 1-5 and comparative examples 1-3 were tested for their properties using conventional prior art inspection methods.

And (3) performance detection:

(1) And (3) testing the relative density: the relative density measurements were made on the titanium alloy articles prepared in examples 1 to 5 and comparative examples 1 to 3, respectively.

(2) And (3) testing mechanical properties: the titanium alloy articles prepared in examples 1 to 5 and comparative examples 1 to 3 were subjected to room temperature tensile strength and elongation measurement, respectively.

(3) And (3) element distribution test: the titanium alloy article prepared in comparative example 2 was subjected to EMPA measurement.

3. Results of the experiment

Through detection, the titanium alloy parts prepared by the preparation method in the embodiments 1 to 5 have fine crystal grains and uniform tissues, and have discontinuous short rod-shaped grain boundary phase alpha-Ti and a small-size alpha bundle structure, wherein the length of the grain boundary phase alpha-Ti is 5 to 15 μm, and the length-diameter ratio is 3 to 8:1; the long and thin alpha-Ti sheets in the alpha beam set structure are parallel to each other, the length of the alpha-Ti sheets is 8-20 mu m, a few residual beta-Ti sheets are distributed among the alpha-Ti sheets, and the alpha beam set structure with the same orientation, namely the sizes of the areas of the sheets with the same orientation are 5-20 mu m.

The results of the experiments of examples 1 to 5 and comparative examples 1 to 3 are summarized below and shown in Table 4.

TABLE 4 comparison of the properties of the titanium alloys prepared in examples 1 to 5 and comparative examples 1 to 3

From the data analysis in table 4, it can be seen that the titanium alloy prepared by the hot isostatic pressing process in comparative example 1 can also obtain a relatively dense part, but it can be found that the compactness, room temperature tensile strength and post-fracture elongation are much lower than those of the parts prepared in examples 1 to 4 of the present invention. This is because, in the present invention, the hydrogen element is introduced to promote the diffusion of the element, refine the crystal grains, and reduce the content of the impurity element. Meanwhile, the prepared discontinuous short rod-shaped crystal boundary alpha phase and small-size alpha beam set structure are designed, so that the prepared titanium alloy part has excellent comprehensive mechanical property, and meanwhile, the compactness is obviously improved due to large deformation provided by hot extrusion.

In addition, in the comparative example 2, the titanium alloy is prepared by sintering at 1000 ℃ and then combining a hot extrusion process, although a compact part can be obtained, the diffusion of aluminum element in the sintering process increases the local beta phase transition temperature, inhibits the diffusion of vanadium element, has a segregation zone caused by obvious uneven element diffusion, and seriously deteriorates the room-temperature tensile property of the titanium alloy part. In the comparative example 3, the sintered blank with higher density can be obtained by adopting the temperature rise process of sintering at higher temperature and then hot extrusion, but the structure crystal grains excessively grow at high temperature to generate a coarse equiaxed structure, so that the alloy strength is reduced.

It can also be seen that the change of any process parameter in the invention will directly affect the element diffusion condition and densification process of the titanium alloy, and a uniform structure with good strong plasticity matching cannot be obtained.

While the invention has been described with reference to specific preferred embodiments, it will be understood by those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.

Claims

1. The high-performance powder metallurgy titanium alloy part is characterized in that the structure of the part is a matrix phase and a grain boundary phase distributed among the matrix phases; wherein the content of the first and second substances,

the matrix phase is an alpha bundle structure;

the grain boundary phase is alpha-Ti and is in a discontinuous short rod shape;

the length of the grain boundary phase is 5-15 mu m, the length-diameter ratio is 3-8: 1;

the preparation method of the product comprises the following steps:

wherein, the sintering treatment is carried out under the protective atmosphere, and the sintering process comprises the following steps: heating the powder pressed compact obtained by the cold isostatic pressing to 600-650 ℃ from room temperature at the speed of 1-5 ℃/min, and preserving heat for 1-2 h; then heating to 1100-1250 ℃ at the speed of 1-5 ℃/min, and preserving the heat for 1-4 h; then cooling to 800 ℃ at the speed of 1-5 ℃/min, preserving heat for 1-4 h, and then cooling the furnace;

the density of the product is more than or equal to 99.8 percent, the oxygen content is 0.21 to 0.25wt.%, the room-temperature tensile strength is 1179 to 1260MPa, and the elongation is 12.6 to 16 percent.

2. The high performance powder metallurgy titanium alloy article of claim 1, wherein the alpha bundle structure comprises elongated alpha-Ti sheets parallel to each other and residual beta-Ti sheets distributed between the elongated alpha-Ti sheets;

the length of the long alpha-Ti sheet layer is 8-20 mu m.

3. The high performance powder metallurgy titanium alloy article of claim 1 or 2, wherein the α -bundle structures of the same orientation are each 5 to 20 μm in size.

4. The high performance powder metallurgy titanium alloy article of claim 1, wherein the cold isostatic pressing process parameters are: the pressure maintaining pressure is 150-300 MPa, and the pressure maintaining time is 5-60 min.

5. The high performance powder metallurgy titanium alloy article of claim 1, wherein the hot extrusion process comprises: heating the sintered blank obtained by the sintering treatment to 1125-1175 ℃ at the speed of 100 ℃/min, preserving the heat for 1-10 min, quickly transferring the sintered blank to a die preheated to 400-500 ℃, and quickly extruding the sintered blank at the extrusion speed of 15-25 mm/s, wherein the extrusion ratio is 9-16: and 1, demolding after the mold is cooled to room temperature.

6. The high performance powder metallurgy titanium alloy article of claim 5, wherein the hot extrusion process is conducted in a sealed glove box under inert gas shielding, wherein the box oxygen content is 100ppm or less.

7. The high performance powder metallurgy titanium alloy article of claim 1, wherein the titanium hydride powder and the alloy powder are mixed using a two roll ball mill; wherein the mixing speed is 70-200 rpm, and the mixing time is 15-25 h.

8. The high-performance powder metallurgy titanium alloy part according to claim 7, wherein the mixing process adopts a mixing mode of forward rotation for 30min, stop for 5min and reverse rotation for 30 min.

9. The high performance powder metallurgy titanium alloy article of claim 1, wherein the titanium hydride powder has a particle size of 5 to 60 μm and a hydrogen content of 3.7 to 3.95wt.%; the grain size of the alloy powder is 5-48 mu m.

10. The high performance powder metallurgy titanium alloy article of claim 9, wherein the alloy powder is 60Al40V powder, or 60Al40V powder, al powder, zr powder, and Mo powder.