CN114058901B

CN114058901B - Submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy and preparation method thereof

Info

Publication number: CN114058901B
Application number: CN202111353849.3A
Authority: CN
Inventors: 武晓刚; 张德良; 张博文; 张彦虎
Original assignee: Northeastern University China
Current assignee: Northeastern University China
Priority date: 2021-11-16
Filing date: 2021-11-16
Publication date: 2022-08-23
Anticipated expiration: 2041-11-16
Also published as: CN114058901A

Abstract

A submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy and a preparation method thereof belong to the field of titanium alloy powder metallurgy. The high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles comprises a titanium alloy matrix and submicron yttrium oxide particles dispersed in the titanium alloy matrix, wherein the submicron yttrium oxide particles account for 0.63-1.9% of the titanium alloy in mass percent. The preparation method comprises using hydrogenated titanium sponge particles as titanium raw material, adding other alloy elements, and adding Y powder or YH powder into the raw material ₂ The powder is subjected to synchronous low-energy ball milling powder mixing and high-energy ball milling mechanical alloying, and then high-temperature rapid induction heating sintering to generate the submicron Y with dispersion distribution in situ ₂ O ₃ And carrying out hot extrusion on the particles to obtain the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy. The preparation method is simple, low in cost and short in production period, and realizes the preparation of the near-alpha powder metallurgy titanium alloy with low cost, low oxygen content and high performance.

Description

Submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy and preparation method thereof

Technical Field

The invention belongs to the technical field of titanium alloy powder metallurgy, and particularly relates to a high-performance near-alpha powder metallurgy titanium alloy toughened by submicron yttrium oxide particles and a preparation method thereof.

Background

The titanium alloy has the advantages of low density, high specific strength, excellent corrosion resistance, good oxidation resistance and the like, is widely applied to the fields of aerospace, ships, automobiles, energy chemical engineering, biomedicine, military industry and the like, and is a structural metal material with wide application prospect. However, since titanium alloys have high-temperature activity and strong affinity with interstitial elements (O, N, C, etc.), the content of impurity elements in the alloys is easily increased during the processing and preparation process, which deteriorates the mechanical properties of the materials. Meanwhile, the titanium alloy has high deformation resistance and poor processing performance, so that the requirements of the titanium alloy on preparation, processing, forming and the like are strict. With the development of production and processing technology, the preparation and research application of titanium alloy have made remarkable progress. The most common and widely applied process for preparing the titanium alloy is Ingot Metallurgy (IM), the titanium alloy obtained by the ingot metallurgy has few holes, high density and low oxygen content, but the ingot is easy to generate component segregation, the production period of the material is long, the energy consumption of smelting and high-temperature forging is large, the equipment expense investment is large, the preparation cost is high, the cost of the titanium alloy prepared by the ingot metallurgy is high, and the method is still widely applied to industries with low cost sensitivity, such as aerospace, military and biomedical fields.

Powder Metallurgy (PM) technology is a method for preparing a metal material having a uniform microstructure without component segregation, and at the same time, the alloy composition design is flexible, the material utilization rate is high, the process flow is short, and the cost is low, and is one of important breakthrough for realizing the low-cost manufacture of titanium alloy and parts thereof. However, the overall mechanical properties of PM titanium alloys have not been satisfactorily achieved compared to Ingot Metallurgy (IM) titanium alloys, particularly in terms of plasticity, toughness and fatigue properties. The high oxygen content and low relative density are the main reasons for the poor comprehensive performance, especially plasticity and fatigue performance of the powder metallurgy titanium alloy, and are also the main obstacles for limiting the engineering application of the powder metallurgy titanium alloy. Thermomechanical consolidation is considered a reliable and effective method to remove residual porosity to increase the density of PM titanium alloys and improve the mechanical properties of titanium alloys. Hot extrusion is a common method for thermo-mechanical consolidation of PM titanium alloy, and hot extrusion of a sintered powder compact not only can eliminate internal pores and improve the compactness of the alloy, but also can crush coarse tissues and drive dynamic recrystallization of beta grains and refine the grains through large plastic deformation, and both can significantly improve the mechanical properties of the alloy.

However, how to realize low oxygen content of PM titanium alloy powder and its alloy, oxygen scavenging and matrix purification, and improving plasticity and toughness of alloy are one of the difficulties and important research directions of powder metallurgy titanium alloy. At present, the oxygen content of powder metallurgy titanium alloy is generally higher, which is mainly because a dense oxidation film is formed on the surface of powder after passivation treatment in the preparation process of raw material powder such as titanium hydride powder, hydrogenated dehydrotitanium powder and intermediate alloy powder, so that the oxygen content of the raw material powder is increased, and further the oxygen content of PM titanium alloy is higher. Although the oxygen content of the commercially available high-purity titanium powder can be controlled within 1000ppm, the high-purity titanium powder is expensive, and the manufacturing cost of the titanium alloy is further increased. Meanwhile, because of the strong affinity of titanium and oxygen, the oxygen is increased in the high-temperature sintering process of the powder, and the oxygen content of the titanium alloy is further increased. Because interstitial solute element oxygen is an effective barrier for dislocation slip and climb, the alloy strength is enhanced with the increase of the content of the interstitial element oxygen in the alloy, but the alloy plasticity is obviously reduced and even brittle failure is caused, so that the engineering application of the powder metallurgy titanium alloy is limited. Oxygen removal by the addition of rare earth elements to the alloy matrix is one of the effective methods to improve the performance of PM titanium alloys. However, the raw material powder used by the current PM titanium alloy is generally subjected to passivation treatment and screening treatment, so that the cost is high, the production period is long, the oxygen content is high, the oxygen removing effect of adding limited rare earth elements is limited and not obvious, and when the content of the rare earth elements is too high, the oxygen removing effect is obvious, but the strength and the plasticity of the alloy are obviously reduced. In addition, the existing addition mode of the rare earth elements is mainly mixed powder, and a rare earth oxide reinforcing phase which is dispersed and distributed cannot be obtained. The powder compact is subjected to long-time high-temperature vacuum sintering, so that the grain size is large, the oxygen content is high, and the production period is still long. In conclusion, the main defects of high oxygen content, large structure, poor comprehensive mechanical property, high cost and long production period in the preparation of the PM titanium alloy material and parts thereof at present are overcome.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy and a preparation method thereof, wherein the high-performance near-alpha powder metallurgy titanium alloy is toughened by solid-phase oxygen removal and purification of a matrix and in-situ generation of submicron yttrium oxide particles, the preparation method is an improved preparation method of powder metallurgy, and the high-performance near-alpha powder metallurgy titanium alloy is hydrogenated sponge with low cost and low oxygen contentTitanium particles and other pure element powder, master alloy powder or particles are used as raw materials, and Y powder or YH is added into the raw materials ₂ Powder, and Y powder or YH powder is obtained by mechanical alloying of the mixed powder and high-energy ball mill through synchronous low-energy ball mill crushing ₂ The powder is uniformly dispersed in the superfine crystal mixed powder, and Y powder or YH powder is obtained in the process of high-temperature rapid induction sintering of the superfine crystal mixed powder pressed compact ₂ The powder absorbs oxygen in the matrix through in-situ reaction to generate the submicron Y in dispersion distribution in situ ₂ O ₃ Particles, which have been found to be submicron Y ₂ O ₃ The particles have obvious toughening effect, so that the high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles with low oxygen content is obtained, the preparation method is simple, the cost is low, the production period is short, and the preparation of the low-cost low-oxygen high-performance near-alpha powder metallurgy titanium alloy is realized.

The technical scheme adopted by the invention is as follows:

the invention relates to a submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, which comprises a titanium alloy matrix and submicron yttrium oxide particles dispersed in the titanium alloy matrix, wherein the mass percentage of the submicron yttrium oxide particles in the total mass of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy is 0.63-1.9 wt.%.

The microstructure of the high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles is a basket structure consisting of fine alpha sheets, discontinuous beta transition structures, beta sheets and the submicron yttrium oxide particles which are distributed in a dispersion manner; wherein the volume percentage of the fine alpha sheet layer is 70-80%; and a nano needle-shaped alpha phase is precipitated in the discontinuous beta transition tissue.

Furthermore, the average thickness of the fine alpha sheet layer is 0.4-0.8 μm, the width of the nano needle-shaped alpha phase is 50-300 nm, and the particle size of the submicron yttrium oxide particles is 300-1000 nm.

The high-performance near-alpha powder metallurgy titanium alloy toughened by submicron yttrium oxide particles has the advantages that the mass percentage content of oxygen in a matrix is less than or equal to 0.2wt%, the relative density is greater than or equal to 99.8%, the yield strength at room temperature is greater than or equal to 1060MPa, the tensile strength is greater than or equal to 1220MPa, the elongation is greater than or equal to 14%, a tensile sample has an obvious necking phenomenon, and the alloy is in a full-toughness fracture mode.

The invention relates to a preparation method of a submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, which comprises the following steps:

step 1: stock preparation

Weighing corresponding raw materials according to the component requirements of the prepared titanium alloy;

step 2: synchronous ball mill

Under the protective atmosphere, carrying out low-energy ball milling on the weighed corresponding raw materials, and crushing and mixing to obtain mixed powder; wherein the ball milling speed of the low-energy ball milling is 100-200 rpm, and the ball milling lasts for 1-5 h; more preferably 150rpm/min for 1 h;

then the mixed powder is subjected to high-energy ball milling mechanical alloying to obtain Y powder and/or YH powder ₂ Ultra-fine grain mixed powder with powder dispersed and distributed; wherein the ball milling speed of the high-energy ball milling mechanical alloying is 500-600 rpm, and the ball milling is carried out for 3-6 h; more preferably: ball milling at 500rpm/min for 3 hr;

and step 3: pressing into a blank

Filling the superfine crystal mixed powder in a mold under a protective atmosphere, vibrating and compacting, and keeping the pressure for 60-900 s under the pressure of 200-900 MPa to perform cold pressing and pressing to form a blank so as to obtain a superfine crystal powder pressed blank;

and 4, step 4: sintering by heating and simultaneous dehydrogenation

Heating the superfine crystal powder pressed compact to 1000-1100 ℃ at a heating rate of 50-100 ℃/min under a protective atmosphere, then heating to 1150-1350 ℃ at a heating rate of 20-50 ℃/min, and preserving heat for 2-15 min to obtain a sintered blank;

and 5: hot extrusion consolidation

And under a protective atmosphere, carrying out hot extrusion on the sintered blank at the temperature of 1150-1350 ℃ to obtain the high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles.

In the step 1, it is preferable that: the titanium alloy comprises the following components in percentage by mass: al: 5.0-7.5%, Sn: 1.0-3.5%, Zr: 3.0-5.5%, Mo: 1-3.5%, Si: 0.05-1.5%, Y: 0.5-1.5%, and the balance of Ti.

More preferably, the titanium alloy comprises the following components in percentage by mass: al: 5.5-7.0%, Sn: 1.5-3.0%, Zr: 3.5-5.0%, Mo: 1.5-3.0%, Si: 0.1 to 1.0%, Y: 0.5-1% and the balance Ti.

In the step 1, the corresponding raw materials are weighed, wherein the raw materials comprise hydrogenated sponge titanium particles, other pure element powder, pure Y powder or YH powder ₂ Powders and master alloys. The master alloy is master alloy powder or master alloy particles.

In the step 1, the corresponding raw materials are weighed, and drying and impurity removal treatment needs to be carried out in advance, and the specific process comprises the following steps: and (3) preserving the heat for 3-5 hours at the temperature of 130-150 ℃ under the vacuum condition.

Further, the pure element powder is pure element powder with the particle size of 100-300 meshes; the master alloy powder is a master alloy powder with a particle size of 100-300 meshes. The master alloy particles are 0.5-5 mm in particle size.

In the step 1, the raw material of Al is preferably gas atomized Al powder, Sn powder as the raw material of Sn, Zr powder and/or ZrH as the raw material of Zr ₂ The powder and Mo are prepared from Mo powder and Al ₄₀ Mo ₆₀ Master alloy powder or Al ₄₀ Mo ₆₀ One or more of the master alloy particles, Si powder as raw material, Y powder and/or YH as raw material ₂ The raw materials of the powder and the Ti are hydrogenated sponge titanium particles.

Furthermore, the mass percentage concentration of each raw material is more than or equal to 99.6 percent.

More preferably, the particle size of the gas atomized Al powder is 200 mesh; the granularity of the Sn powder is 200 meshes; ZrH ₂ The granularity of the powder is 200 meshes; mo is taken as a raw material, and the granularity of the raw material is 0.5-1 mm, and the granularity of the raw material is Al ₄₀ Mo ₆₀ Master alloy particles; the granularity of the Si powder is 300 meshes; the particle size of the raw material of Y is 300 meshes.

The hydrogenated titanium sponge particles are obtained by carrying out high-temperature hydrogenation treatment on the titanium sponge particles, and the high-temperature hydrogenation treatment process comprises the following steps: maintaining the hydrogen pressure of 1-1.5 bar at 400-750 ℃, preserving the heat for 2-5 h, and cooling along with the furnace; more preferably: keeping the temperature at 450-550 ℃ for 3 h.

In the step 2, the ball milling is preferably one of a planetary ball mill or a stirring ball mill.

In the step 2, the high-energy ball milling is continuously carried out after the low-energy ball milling is carried out for mixing the powder, and the ball milling tank is kept in a closed state in the whole ball milling process.

In the step 3, the superfine crystal mixed powder prepared by the high-energy ball milling is carried out under the protection of inert atmosphere all the time in the subsequent powder discharging, packaging, transferring and blank pressing processes, and the powder is not passivated to prevent the powder from being oxidized and even exposed in the air to cause spontaneous combustion.

In the step 3, the pressing formed blank is demoulded by adopting a warm demoulding and reverse ejection mode in the demoulding process, and the specific process comprises the following steps: preheating a die to 100-500 ℃ before reverse ejection and demolding, and more preferably 300-400 ℃, and then performing reverse demolding to obtain an ultrafine-grained powder compact; the relative density of the superfine crystal powder pressed compact is more than or equal to 85 percent.

In the step 4, the heating sintering is preferably induction heating sintering, and more preferably, a medium-frequency electromagnetic induction coil is adopted for induction heating; wherein, the frequency of medium frequency electromagnetic induction coil is 8 ~10 KHz.

More preferably, in the step 4, the following process parameters are preferably selected for the heating and sintering: heating to 1050-1100 ℃ at a heating rate of 60-80 ℃/min, heating to 1200-1350 ℃ at a heating rate of 20-40 ℃/min, and keeping the temperature for 5-10 min.

In the step 5, the preheating temperature of the hot extrusion adopted by the hot extrusion is 200-450 ℃.

In the step 5, the extrusion ratio of hot extrusion is (9-25): 1.

In the preparation method of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, the protective atmosphere is inert gas protective atmosphere, more preferably argon gas protective atmosphere, wherein the volume concentration of oxygen in argon gas is less than 100 ppm.

In the preparation method of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, the thermomechanically consolidated submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium/titanium alloy can be one of bars, pipes, plates or other section parts according to different hot extrusion dies.

Compared with the prior art, the high-performance near-alpha powder metallurgy titanium alloy toughened by submicron yttrium oxide particles and the preparation method thereof have the characteristics and beneficial effects that:

the invention provides a preparation method of a high-performance near-alpha powder metallurgy titanium alloy toughened by submicron yttrium oxide particles generated by solid-phase deoxygenation and in-situ reaction, which takes hydrogenated sponge titanium particles with low price and low oxygen content and other pure element powder, intermediate alloy powder or particles as raw materials, and adds a small amount of Y powder or YH powder into the alloy ₂ And (3) rapidly preparing the superfine mixed powder by synchronous low-energy ball milling crushing and mixing the powder and high-energy ball milling mechanical alloying. The superfine crystal mixed powder is pressed into a blank, rapidly heated and sintered by induction heating and is formed by hot extrusion, so that the high-performance powder metallurgy titanium alloy bar with fine and uniform tissue, low oxygen content and submicron yttrium oxide particle dispersion toughening is rapidly prepared. The whole process of powder making, green pressing, sintering and hot extrusion forming is carried out under the protection of inert atmosphere, so that the oxygen content of the alloy can be effectively reduced. The titanium hydride powder prepared by the synchronous low-energy ball milling of the titanium hydride sponge particles with low price is used as a raw material, the powder yield is high, the screening is not needed, the material utilization rate is 100 percent, the powder preparation efficiency is high, and the cost is low. Meanwhile, in the ball milling process, no process control agent is needed to be added due to the brittleness of the hydrogenated titanium sponge particles, so that the pollution of powder and further oxygenation are prevented. In addition, because the hydrogen is released in the sintering process of the titanium hydride, the purpose of cleaning the surfaces of titanium powder particles can be achieved, and the oxygen content of the titanium alloy can be effectively reduced by using the titanium hydride powder to replace hydrogenated and dehydrogenated pure titanium powder. More importantly, a small amount of Y powder or YH powder is added to the mixed powder ₂ The powder is subjected to synchronous low-energy and high-energy ball milling, and Y powder or YH powder can be obtained ₂ The powder is uniformly dispersed in the superfine crystal mixed powder, and submicron Y is generated by solid-phase oxygen absorption and in-situ reaction in the process of induction heating and sintering ₂ O ₃ EnhancementThe particles can further reduce the oxygen content of the alloy and simultaneously obtain the high-performance titanium alloy toughened by the sub-micron particles which are dispersed. The preparation method is simple, low in cost, short in production period and high in material utilization rate, the obtained submicron particle toughened high-performance near-alpha powder metallurgy titanium alloy material is low in oxygen content and high in density, has excellent room temperature mechanical properties, shows good feasibility for preparing low-cost powder metallurgy titanium alloys with excellent comprehensive properties, and has extremely high guiding significance and application prospect.

Drawings

FIG. 1: example 1 scanning electron microscope picture of ultra-fine grained powder prepared by synchronous ball milling.

FIG. 2: example 1 XRD pattern of ultrafine grained powder prepared by simultaneous ball milling.

FIG. 3: metallographic pictures of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 1.

FIG. 4: scanning electron micrographs of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 1: (a) a low magnification photograph; (b) high magnification photograph.

FIG. 5: room temperature tensile curve of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 1.

FIG. 6: SEM images of near-fracture longitudinal cross-sections (a) and SEM images of fractures (b) of tensile specimens of submicron-particle toughened high-performance near-alpha powder metallurgy titanium alloy bars prepared in example 1.

FIG. 7 is a schematic view of: metallographic pictures of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 2.

FIG. 8: room temperature tensile curve of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 2.

FIG. 9: metallographic pictures of submicron particle toughened high performance near alpha powder metallurgy titanium alloy bars prepared in example 3.

FIG. 10: the room temperature tensile curve of the submicron particle toughened high performance near alpha powder metallurgy titanium alloy bar prepared in example 3.

FIG. 11: metallographic pictures of near alpha powder metallurgy titanium alloy bars prepared in comparative example 1.

FIG. 12: room temperature tensile curve for near alpha powder metallurgy titanium alloy bars prepared in comparative example 1.

FIG. 13 is a schematic view of: SEM (scanning Electron microscope) image of near-fracture longitudinal section and SEM (fracture) image of near-alpha powder metallurgy titanium alloy bar tensile sample prepared in comparative example 1.

Detailed Description

The following detailed description of the embodiments of the invention refers to the accompanying drawings and technical solutions.

In the following examples, unless otherwise specified, all the raw materials and equipment used were commercially available.

In the following examples, the mass purity of the added raw materials was not less than 99.6%.

In the following examples, the protective atmosphere used is an argon protective atmosphere, with a volume concentration of oxygen in argon of <100 ppm.

Example 1

The preparation method of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy comprises the following steps:

step 1: hydrogenation of titanium sponge

In a high-temperature hydrogenation furnace, carrying out high-temperature hydrogenation treatment on the titanium sponge particles to prepare embrittled hydrogenated titanium sponge particles, wherein the specific process of the high-temperature hydrogenation treatment comprises the following steps: keeping the temperature for 3 hours at 450 ℃ under the hydrogen pressure of 1-1.5 bar, and then cooling the furnace;

step 2: stock preparation

Respectively putting hydrogenated titanium sponge particles, atomized Al powder (-200 meshes), Sn powder (-200 meshes), Zr powder (-200 meshes), Mo powder (-200 meshes), Si powder (-300 meshes) and Y powder (-300 meshes) into a vacuum oven for drying and degassing to remove impurities such as water vapor on the surface of the material, wherein the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

according to the nominal components of the prepared submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, the titanium alloy comprises the following components in percentage by mass: 5.9%, Sn: 2.4%, Zr: 4.1%, Mo: 2.2%, Si: 0.15%, Y: 0.5 percent of Ti, and weighing raw material powder of each element;

and 3, step 3: synchronous ball milling for preparing superfine crystal mixed powder

Under the protective atmosphere, putting the weighed hydrogenated titanium sponge particles and all raw materials of each element powder into a ball milling tank together for sealing, firstly carrying out low-energy ball milling on a planetary ball mill to crush the hydrogenated titanium sponge particles into powder and uniformly mixing the raw material powder, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the ball milling is carried out for 3 hours at 200 rpm; and then carrying out high-energy ball milling after the low-energy ball milling is finished, uniformly mixing the Y powder in the mixed powder and simultaneously preparing ultrafine-grained mixed powder by mechanical alloying, wherein the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 6 hours to obtain uniformly mixed superfine crystal mixed powder;

and 4, step 4: pressing into a blank

The superfine crystal mixed powder after synchronous ball milling does not undergo passivation treatment, in order to avoid the oxidation of the superfine crystal mixed material in the air, under the protective atmosphere, the superfine crystal mixed powder which is uniformly mixed is filled in a cylindrical die, after the superfine crystal mixed powder is compacted by vibration, the pressure is maintained for 300s under the pressure of 800MPa, the superfine crystal mixed powder is cold-pressed and pressed into a blank, after the pressing into the blank, the blank is demoulded by adopting a warm demoulding reverse ejection mode, and the specific process is as follows: preheating a cylindrical die to 400 ℃ before reverse ejection demoulding, and then performing reverse demoulding to obtain an ultra-fine grain powder compact; the relative density of the superfine crystal powder pressed compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 10KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 60 ℃/min, and then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 40 ℃/min and is insulated for 10min, so that a sintered blank is obtained;

step 6: hot extrusion consolidation

Under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion, wherein the extrusion ratio is 16:1, and obtaining a high-performance near-alpha powder metallurgy titanium alloy extrusion bar toughened by submicron yttrium oxide particles;

fig. 1 is a scanning electron microscope picture of the ultrafine grain mixed powder prepared by the synchronous ball milling in this embodiment, which shows that the ultrafine grain mixed powder after the high-energy ball milling has uniform particle size distribution, no sharp edges and large particle size, and no cluster cold welding phenomenon, and a fine and uniform powder particle mixture is generated. FIG. 2 is an XRD phase analysis spectrum of the ultrafine grain mixed powder prepared by the synchronous ball milling in this example, and the result shows that the main phase of the powder raw material after the high-energy ball milling is TiH with face-centered cubic (fcc) structure ₂ Phase and a small amount of diffraction peaks of Y and Al, and TiH was also found ₂ The diffraction peak of phase is obviously broadened, which shows that most alloying elements are mechanically alloyed in the ball milling process. Fig. 3 is a metallographic photograph of a microstructure of a high-performance near- α powder metallurgy titanium alloy toughened with submicron yttria particles prepared in this embodiment, which shows that the material is fully dense, has no residual pores inside, has fine and staggered lamellar layers, has no obvious original β -grain boundary, shows a typical basket structure, and has a large amount of submicron yttria particles dispersed in a matrix. FIG. 4 is a scanning electron micrograph of a microstructure of a high performance near- α powder metallurgy titanium alloy toughened with submicron yttrium oxide particles prepared in this example, the microstructure mainly including fine α lamellae, discontinuous β -transstructures, a small number of β lamellae, and submicron Y lamellae ₂ O ₃ The average thickness of the fine alpha lamella is 0.75 mu m, a large amount of nano needle-shaped alpha is separated out from the beta transformation tissue, the width of the nano needle-shaped alpha phase is 50-300 nm, and the particle size of the submicron Y phase is 300-1000 nm ₂ O ₃ The particles are dispersed on the substrate. Fig. 5 is a room temperature engineering stress-strain curve of the high performance near- α powder metallurgy titanium alloy toughened by submicron yttria particles prepared in this embodiment, where the yield strength at room temperature is 1134MPa, the tensile strength is 1242MPa, and the elongation is 15%, and there is an obvious necking phenomenon. FIG. 6 is a graph of submicron yttria particle toughening prepared in this exampleThe SEM image and the SEM image of the fracture near the longitudinal section of the tensile sample of the high-performance near-alpha powder metallurgy titanium alloy show that the fracture surface is more zigzag, a large number of micropores exist in the longitudinal section, a large number of dimples and submicron yttrium oxide particles exist in the fracture, and the fracture is a typical full-toughness fracture mode and shows that the toughness is high, and the oxygen content in the high-performance near-alpha powder metallurgy titanium alloy matrix toughened by the submicron yttrium oxide particles is low. As can be seen from FIG. 5, compared with the titanium alloy with high oxygen content and low density prepared by the traditional powder metallurgy method, the high-performance near-alpha powder metallurgy titanium alloy toughened by the dispersion-distributed submicron yttrium oxide particles generated by the solid-phase deoxidization and in-situ reaction prepared by the powder metallurgy method has excellent room temperature strength and good plasticity, and has wide application prospect in engineering application with higher requirements on comprehensive mechanical properties. In conclusion, the titanium alloy material with low oxygen content, high compactness, fine and uniform structure and good comprehensive performance can be successfully prepared by the powder metallurgy method for generating the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy through solid-phase deoxygenation and in-situ reaction.

Example 2

The preparation method of the high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles comprises the following steps:

step 1: hydrogenation of titanium sponge

In a high-temperature hydrogenation furnace, carrying out high-temperature hydrogenation treatment on the titanium sponge particles to prepare embrittled hydrogenated titanium sponge particles, wherein the specific process of the high-temperature hydrogenation treatment comprises the following steps: keeping the temperature for 3 hours at 450 ℃ and under the hydrogen pressure of 1-1.5 bar, and then cooling the furnace;

step 2: stock preparation

Respectively putting hydrogenated titanium sponge particles, atomized Al powder (-200 meshes), Sn powder (-200 meshes), Zr powder (-200 meshes), aluminum-molybdenum intermediate alloy particles (smaller than 1mm), Si powder (-300 meshes) and Y powder (-300 meshes) into a vacuum oven for drying and degassing to remove impurities such as water vapor on the surface of the material, wherein the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

according to the nominal components of the prepared high-performance near-alpha powder metallurgy titanium alloy, the high-performance near-alpha powder metallurgy titanium alloy comprises the following components in percentage by mass: 5.9%, Sn: 2.4%, Zr: 4.1%, Mo: 2.2%, Si: 0.15%, Y: 0.5 percent of Ti, and weighing raw material powder of each element;

Under the protective atmosphere, the weighed titanium sponge hydride particles, various element powders and intermediate alloy particles are put into a ball milling tank together for sealing, and on a planetary ball mill, low-energy ball milling is firstly carried out to crush the titanium sponge hydride particles and the aluminum-molybdenum intermediate alloy particles into powder and simultaneously uniformly mix raw material powders, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the ball milling is carried out for 1 hour at 200 rpm; and then carrying out high-energy ball milling after the low-energy ball milling is finished, uniformly mixing Y powder in the mixed powder and preparing ultrafine-grained mixed powder by mechanical alloying, wherein the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 3 hours to obtain uniformly mixed superfine crystal mixed powder;

and 4, step 4: pressing into blank

The superfine crystal mixed powder after synchronous ball milling does not undergo passivation treatment, in order to avoid the oxidation of the superfine crystal mixed material in the air, under the protective atmosphere, the superfine crystal mixed powder which is uniformly mixed is filled in a cylindrical die, after the superfine crystal mixed powder is compacted by vibration, the pressure is maintained for 300s under the pressure of 800MPa, the superfine crystal mixed powder is cold-pressed and pressed into a blank, after the pressing into the blank, the blank is demoulded by adopting a warm demoulding reverse ejection mode, and the specific process is as follows: preheating a cylindrical die to 400 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder compact; the relative density of the superfine crystal powder pressed compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 10KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 60 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 40 ℃/min, and the temperature is kept for 5min, so that a sintered blank is obtained;

step 6: hot extrusion consolidation

And under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion, wherein the extrusion ratio is 16:1, and obtaining the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy extrusion bar.

Fig. 7 is a metallographic photograph of a high-performance near- α powder metallurgy titanium alloy toughened by submicron yttria particles obtained by the present embodiment, which shows that the inside of the structure is fully dense, no residual holes exist, the relative density reaches more than 99.8%, a large number of submicron particles are dispersed on the matrix, no obvious original β crystal grain boundary exists, and the structure is a fine and uniform basket structure. Fig. 8 is a room temperature engineering stress-strain curve of the high performance near- α powder metallurgy titanium alloy toughened by submicron yttria particles prepared in this embodiment, wherein the yield strength is 1074MPa, the tensile strength is 1244MPa, and the elongation is 15.6%, and a significant necking phenomenon exists.

Example 3

step 1: hydrogenation of titanium sponge

step 2: stock preparation

Hydrogenated sponge titanium particles, atomized Al powder (-200 meshes), Sn powder (-200 meshes), Zr powder (-200 meshes), aluminum molybdenum master alloy particles (less than 1mm), Si powder (-300 meshes) and YH ₂ The powder (-300 meshes) is respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor and the like on the surface of the material, and the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

and step 3: synchronous ball milling for preparing superfine crystal mixed powder

Under the protective atmosphere, the weighed hydrogenated titanium sponge particles, various element powders and aluminum-molybdenum intermediate alloy particles are filled into a ball-milling tank together for sealing, and on a planetary ball mill, low-energy ball milling is firstly carried out to crush the hydrogenated titanium sponge particles and the aluminum-molybdenum intermediate alloy particles into powder and simultaneously uniformly mix raw material powders, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the low-energy ball milling is carried out for 1 hour at 200 rpm; high-energy ball milling is carried out on the mixture after the low-energy ball milling is finished, and YH ₂ The powder is uniformly mixed in the mixed powder and simultaneously mechanically alloyed to prepare the ultrafine-grained mixed powder, and the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 3 hours to obtain uniformly mixed ultrafine-grained mixed powder;

and 4, step 4: pressing into blank

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid the oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 8KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 80 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 40 ℃/min and is insulated for 5min, and a sintered blank is obtained;

step 6: consolidation by hot extrusion

Fig. 9 is a metallographic photograph of the high-performance near- α powder metallurgy titanium alloy toughened by submicron yttria particles obtained by the present embodiment, which shows that the inside of the structure is fully dense, no residual holes exist, the relative density reaches more than 99.8%, and a large amount of submicron particles are dispersed on the substrate, so that the submicron powder metallurgy titanium alloy is a fine and uniform basket structure. Fig. 10 is a room temperature engineering stress-strain curve of the submicron yttrium oxide particle toughened high-performance near- α powder metallurgy titanium alloy prepared in this embodiment, wherein the yield strength at room temperature is 1092MPa, the tensile strength is 1234MPa, and the elongation is 16.3%, and an obvious necking phenomenon exists.

Example 4

step 1: hydrogenation of titanium sponge

Carrying out high-temperature hydrogenation treatment on the titanium sponge particles in a high-temperature hydrogenation furnace to prepare embrittled hydrogenated titanium sponge particles, and facilitating subsequent ball milling powder preparation, wherein the specific process comprises the following steps: keeping the temperature for 2 hours at 600 ℃ and 1-1.5 bar of hydrogen pressure, and then cooling the furnace;

step 2: stock preparation

According to the components of the prepared submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, weighing the following raw materials in percentage by mass: al: 7.5%, Sn: 1.0%, Zr: 3.0%, Mo: 1%, Si: 0.05%, Y: 1.5 percent, and the balance being Ti;

wherein, the raw material of the Al is gas atomized Al powder with the granularity of 200 meshes; the raw material of Sn is Sn powder with the granularity of 200 meshes; zr is selected from ZrH with the grain size of 200 meshes ₂ Pulverizing; the raw material of Mo is Al with the granularity of 0.5-1 mm ₄₀ Mo ₆₀ Intermediate alloyParticles; the raw material of Si is Si powder with the granularity of 300 meshes; the raw material of Y is Y powder with the granularity of 300 meshes, and the raw material of Ti is titanium sponge hydride particles.

Before synchronous ball-milling, the raw materials of the components are respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor on the surface of the material, and the specific process comprises the following steps: preserving the heat for 3 hours at 150 ℃ under the vacuum condition;

and step 3: synchronous ball milling preparation of superfine crystal mixed powder

Under the protective atmosphere, the dried raw materials of the components are put into a ball milling tank together and sealed, and in a stirring ball mill, low-energy ball milling is firstly carried out to crush titanium sponge hydride particles and master alloy particles in the raw materials of the components into powder and simultaneously uniformly mix raw material powder, and the specific process comprises the following steps: the revolution and rotation ratio is 1:2, and the low-energy ball milling is carried out for 2 hours at 150 rpm; then carrying out high-energy ball milling mechanical alloying to prepare ultra-fine grain mixed powder with Y powder in dispersion distribution, wherein the specific process comprises the following steps: high-energy ball milling at 600rpm for 5 hours;

and 4, step 4: pressing into blank

Filling the superfine crystal mixed powder in a mold under a protective atmosphere, maintaining the pressure for 60s under the pressure of 900MPa after vibrating compaction to form a blank by cold pressing, and demolding by adopting a warm demolding reverse ejection mode after the pressing is finished, wherein the specific process comprises the following steps of: preheating a die to 400 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder compact; the relative density of the powder pressed compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

Carrying out induction heating in a medium-frequency electromagnetic induction coil under a protective atmosphere, wherein the frequency of the medium-frequency electromagnetic induction coil is 8-10 KHz, heating the superfine crystal powder pressed compact to 1000 ℃ at a heating rate of 100 ℃/min, then heating to 1150 ℃ at a heating rate of 50 ℃/min, and preserving heat for 15min to obtain a sintered blank;

step 6: consolidation by hot extrusion

The submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy prepared by the embodiment has the yield strength of 1100MPa, the tensile strength of 1240MPa and the elongation of 16.1 percent at room temperature, has an obvious necking phenomenon and is in a full-toughness fracture mode.

Example 5

step 1: hydrogenation of titanium sponge

step 2: stock preparation

according to the nominal components of the prepared high-performance near-alpha powder metallurgy titanium alloy, the high-performance near-alpha powder metallurgy titanium alloy comprises the following components in percentage by mass: 5.9%, Sn: 2.4%, Zr: 4.1%, Mo: 2.2%, Si: 0.15%, Y: 0.5 percent of Ti, and the balance of Ti, and weighing raw material powder of each element;

Under the protective atmosphere, the weighed hydrogenated titanium sponge particles, the element powder and the aluminum-molybdenum intermediate alloy particles are filled into a ball milling tank together and sealed, and on a planetary ball mill, low-energy ball milling is firstly carried out to crush the hydrogenated titanium sponge particles and the aluminum-molybdenum intermediate alloy particles into powder and simultaneously uniformly mix the raw material powder, wherein the specific process comprises the following steps: revolution and rotationThe ratio is 1:2, the ball material ratio is 5:1, and the low-energy ball milling is carried out for 2 hours at 200 rpm; high-energy ball milling is carried out on the mixture after the low-energy ball milling is finished, and YH ₂ The powder is uniformly mixed in the mixed powder and simultaneously mechanically alloyed to prepare the ultrafine-grained mixed powder, and the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 6 hours to obtain uniformly mixed superfine crystal mixed powder;

and 4, step 4: pressing into blank

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 8KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 100 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 50 ℃/min and is insulated for 3min, and a sintered blank is obtained;

step 6: hot extrusion consolidation

The submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy prepared by the embodiment has the yield strength of 1110MPa, the tensile strength of 1230MPa and the elongation of 15.5 percent at room temperature, has an obvious necking phenomenon and is in a full-toughness fracture mode.

Example 6

step 1: hydrogenation of titanium sponge

step 2: stock preparation

Under the protective atmosphere, the weighed hydrogenated titanium sponge particles, various element powders and aluminum-molybdenum intermediate alloy particles are filled into a ball-milling tank together for sealing, and on a planetary ball mill, low-energy ball milling is firstly carried out to crush the hydrogenated titanium sponge particles and the aluminum-molybdenum intermediate alloy particles into powder and simultaneously uniformly mix raw material powders, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the low-energy ball milling is carried out for 1 hour at 200 rpm; high-energy ball milling is carried out on the mixture after the low-energy ball milling is finished, and YH ₂ The powder is uniformly mixed in the mixed powder and simultaneously mechanically alloyed to prepare the ultrafine-grained mixed powder, and the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 3 hours to obtain uniformly mixed superfine crystal mixed powder;

and 4, step 4: pressing into blank

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 8KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 100 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 50 ℃/min, and the temperature is kept for 5min, so that a sintered blank is obtained;

and 6: consolidation by hot extrusion

And under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion, wherein the extrusion ratio is 25:1, and obtaining the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy extrusion bar.

The submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy prepared by the embodiment has the yield strength of 1120MPa, the tensile strength of 1245MPa and the elongation of 17.2 percent at room temperature, has an obvious necking phenomenon and is a full-toughness fracture mode.

Example 7

step 1: hydrogenation of titanium sponge

Carrying out high-temperature hydrogenation treatment on the titanium sponge particles in a high-temperature hydrogenation furnace to prepare embrittled hydrogenated titanium sponge particles, and facilitating subsequent ball milling powder preparation, wherein the specific process comprises the following steps: preserving the heat for 3 hours at 550 ℃ and under the hydrogen pressure of 1-1.5 bar, and then cooling the furnace;

and 2, step: stock preparation

According to the components of the prepared submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, weighing the following raw materials in percentage by mass: al: 5.5%, Sn: 3.0%, Zr: 5.0%, Mo: 2.0%, Si: 0.15%, Y: 1% and the balance Ti;

wherein, the raw material of the Al is gas atomized Al powder with the granularity of 200 meshes; the raw material of Sn is Sn powder with the granularity of 200 meshes; the raw material of Zr is Zr powder with the granularity of 200 meshes; the raw material of Mo is Al with the granularity of 0.5-1 mm ₄₀ Mo ₆₀ Master alloy particles; the raw material of Si is Si powder with the granularity of 300 meshes; the raw material of Y is Y powder with the granularity of 300 meshes, and the raw material of Ti is titanium sponge hydride particles.

Before synchronous ball-milling, the raw materials of the components are respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor on the surface of the material, and the specific process comprises the following steps: preserving the heat for 5 hours at 130 ℃ under the vacuum condition;

Under the protection atmosphere, the dried raw materials of the components are put into a ball milling tank together and sealed, and in a stirring ball mill, low-energy ball milling is firstly carried out to crush hydrogenated sponge titanium particles and master alloy particles in the raw materials of the components into powder and simultaneously uniformly mix raw material powder, and the specific process comprises the following steps: the revolution and rotation ratio is 1:2, and the low-energy ball milling is carried out for 1 hour at 150 rpm; then carrying out high-energy ball milling mechanical alloying to prepare ultra-fine grain mixed powder with Y powder in dispersion distribution, wherein the specific process comprises the following steps: 500rpm high-energy ball for 3 hours;

and 4, step 4: pressing into blank

Filling the superfine crystal mixed powder in a mold under a protective atmosphere, keeping the pressure for 800s under the pressure of 300MPa after vibrating compaction to form a blank by cold pressing, and demolding by adopting a warm demolding reverse ejection mode after the pressing is finished, wherein the specific process comprises the following steps: preheating a die to 300 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder compact; the relative density of the powder compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

Carrying out induction heating in a medium-frequency electromagnetic induction coil under a protective atmosphere, wherein the frequency of the medium-frequency electromagnetic induction coil is 9KHz, heating the superfine crystal powder pressed compact to 1050 ℃ at a heating rate of 60 ℃/min, then heating to 1250 ℃ at a heating rate of 40 ℃/min, and preserving heat for 10min to obtain a sintered blank;

step 6: consolidation by hot extrusion

And under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 200 ℃ for hot extrusion, wherein the extrusion ratio is 10:1, and obtaining the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy extrusion bar.

The submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy prepared by the embodiment has the yield strength of 1054MPa, the tensile strength of 1210MPa and the elongation of 14.5 percent at room temperature, has an obvious necking phenomenon and is in a full-toughness fracture mode.

Example 8

step 1: commercially available hydrogenated titanium sponge particles were used.

And 2, step: stock preparation

According to the components of the prepared submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy, weighing the following raw materials in percentage by mass: al: 7.0%, Sn: 1.5%, Zr: 3.5%, Mo: 3.0%, Si: 1.0%, Y: 0.5 percent, and the balance being Ti;

wherein, the raw material of the Al is gas atomized Al powder with the granularity of 200 meshes; the raw material of Sn is Sn powder with the granularity of 200 meshes; zr is prepared fromZrH with particle size of 200 meshes ₂ Pulverizing; the raw material of Mo is Al with the granularity of 0.5-1 mm ₄₀ Mo ₆₀ Master alloy particles; the raw material of Si is Si powder with the granularity of 300 meshes; the raw material of Y is Y powder with the granularity of 300 meshes, and the raw material of Ti is titanium sponge hydride particles.

Before synchronous ball-milling, the raw materials of the components are respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor on the surface of the material, and the specific process comprises the following steps: preserving the heat for 4 hours at 130 ℃ under the vacuum condition;

Under the protective atmosphere, the dried raw materials of the components are put into a ball milling tank together and sealed, and in a stirring ball mill, low-energy ball milling is firstly carried out to crush titanium sponge hydride particles and master alloy particles in the raw materials of the components into powder and simultaneously uniformly mix raw material powder, and the specific process comprises the following steps: the revolution and rotation ratio is 1:2, and the low-energy ball milling is carried out for 1 hour at 200 rpm; then carrying out high-energy ball milling mechanical alloying to prepare ultra-fine grain mixed powder with Y powder in dispersion distribution, wherein the specific process comprises the following steps: high-energy ball milling at 600rpm for 3 hours;

and 4, step 4: pressing into a blank

Under the protective atmosphere, filling the ultrafine-grained mixed powder in a mold, after vibration compaction, maintaining the pressure for 300s under the pressure of 500MPa to perform cold pressing to form a blank, and demolding by adopting a warm demolding reverse ejection mode after the pressing to form the blank is finished, wherein the specific process comprises the following steps of: preheating a die to 100 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder compact; the relative density of the powder compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

Carrying out induction heating in a medium-frequency electromagnetic induction coil under a protective atmosphere, wherein the frequency of the medium-frequency electromagnetic induction coil is 10KHz, heating the superfine crystal powder pressed compact to 1100 ℃ at a heating rate of 80 ℃/min, then heating to 1350 ℃ at a heating rate of 20 ℃/min, and preserving heat for 5min to obtain a sintered blank;

and 6: hot extrusion consolidation

And under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion, wherein the extrusion ratio is 20:1, and obtaining the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy extrusion bar.

The submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy prepared by the embodiment has the yield strength of 1088MPa, the tensile strength of 1210MPa and the elongation of 16.5 percent at room temperature, has an obvious necking phenomenon and is in a full-toughness fracture mode.

Comparative example 1

A preparation method of powder metallurgy titanium alloy comprises the following steps:

step 1: hydrogenation of titanium sponge

Carrying out high-temperature hydrogenation treatment on the titanium sponge particles in a high-temperature hydrogenation furnace to prepare embrittled hydrogenated titanium sponge particles, wherein the specific process of the high-temperature hydrogenation treatment comprises the following steps: keeping the temperature for 3 hours at 450 ℃ and under the hydrogen pressure of 1-1.5 bar, and then cooling the furnace;

step 2: stock preparation

Respectively putting hydrogenated titanium sponge particles, atomized Al powder (-200 meshes), Sn powder (-200 meshes), Zr powder (-200 meshes), Mo powder (-200 meshes) and Si powder (-300 meshes) into a vacuum oven for drying and degassing to remove impurities such as water vapor and the like on the surface of the material, and the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

according to the nominal components of the prepared near-alpha powder metallurgy titanium alloy, the near-alpha powder metallurgy titanium alloy comprises the following components in percentage by mass: 5.9%, Sn: 2.4%, Zr: 4.1%, Mo: 2.2%, Si: 0.15 percent of Ti, and weighing raw material powder of each element;

Under the protective atmosphere, the weighed titanium sponge hydride particles and various element powders are put into a ball milling tank together, firstly, low-energy ball milling is carried out on a planetary ball mill to crush the titanium sponge hydride particles into powder, and meanwhile, the raw material powders are uniformly mixed, and the specific process comprises the following steps: the ball-material ratio is 5:1, and the low-energy ball milling is carried out for 1 hour at 200 rpm; and then carrying out high-energy ball milling after the low-energy ball milling is finished, further uniformly mixing the mixed powder and preparing ultrafine-grained mixed powder by mechanical alloying, wherein the specific process comprises the following steps: carrying out high-energy ball milling at 500rpm for 3 hours to obtain an ultrafine-grained mixed material which is uniformly mixed;

and 4, step 4: pressing into a blank

The superfine crystal mixed material after synchronous ball milling is not subjected to passivation treatment, so that the superfine crystal mixed material is prevented from being oxidized in the air, the uniformly mixed superfine crystal mixed powder is filled in a cylindrical die under the protective atmosphere, and after vibration compaction, the pressure is maintained for 300s under the pressure of 800MPa for cold pressing and pressing to form a blank, so that a superfine crystal powder pressed blank is obtained;

and 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 80 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 40 ℃/min, and the temperature is kept for 5min, so that a sintered blank is obtained;

and 6: hot extrusion consolidation

And under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion, wherein the extrusion ratio is 16:1, and obtaining the high-density titanium alloy extruded bar.

Fig. 11 is a metallographic photograph of the near- α powder metallurgy titanium alloy obtained in the present embodiment, which shows that the inside of the structure is fully dense and has no residual pores, and the original β -grain boundaries are clearly visible and are typical widmannstatten structures. FIG. 12 is the room temperature engineering stress-strain curve of the near α powder metallurgy titanium alloy prepared in this example, wherein the yield strength at room temperature is 1150MPa, the tensile strength is 1315MPa, the elongation is 5.8%, and no necking phenomenon occurs. Fig. 13 is an SEM image of a fracture near a longitudinal cross section and an SEM image of a fracture of the tensile sample of the near- α powder metallurgy titanium alloy prepared in this embodiment, which show that the fracture surface is relatively flat and the micropores of the longitudinal cross section are few, and the fracture has a large number of cleavage surfaces and a small number of dimples, which is a quasi-cleavage fracture mode. Compared with the high-performance near-alpha powder metallurgy titanium alloy toughened by submicron yttrium oxide particles generated by solid-phase deoxygenation and in-situ reaction, the high-performance near-alpha powder metallurgy titanium alloy has the advantages of higher oxygen content, large structure and poor comprehensive mechanical property, particularly plasticity, and cannot meet the use in the industrial field with higher requirements on the comprehensive mechanical property, so that the performance of the PM titanium alloy is greatly influenced by the addition of the rare earth element Y.

Comparative example 2

step 1: commercially available-200 mesh titanium hydride powder was used.

And 2, step: stock preparation

Mix TiH ₂ Powder (-200 mesh), atomized Al powder (-200 mesh), Sn powder (-200 mesh), Zr powder (-200 mesh), Mo powder (-200 mesh), Si powder (-300 mesh) and YH ₂ The powder (-300 meshes) is respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor and the like on the surface of the material, and the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

according to the nominal components of the prepared near-alpha powder metallurgy titanium alloy, the near-alpha powder metallurgy titanium alloy comprises the following components in percentage by mass: 5.9%, Sn: 2.4%, Zr: 4.1%, Mo: 2.2%, Si: 0.15%, Y: 0.5 percent of Ti, and weighing raw material powder of each element;

Under the protective atmosphere, weighing TiH ₂ The powder and each element powder are put into a ball milling tank together for high-energy ball milling in a planetary ball mill, the mixed powder is uniformly mixed, and simultaneously, the superfine crystal mixed powder is prepared by mechanical alloying, and the specific process comprises the following steps: carrying out high-energy ball milling at 500rpm for 3 hours to obtain an ultrafine-grained mixed material which is uniformly mixed;

and 4, step 4: pressing into a blank

and 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid the oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the temperature is heated to 1100 ℃ at the heating rate of 80 ℃/min, then the temperature is heated to 1200 ℃ at the heating rate of 40 ℃/min, and the temperature is kept for 5min, so that a sintered blank is obtained;

step 6: hot extrusion consolidation

A titanium alloy was prepared in the same manner as in example 1, except that commercially available TiH of 200 mesh was used ₂ Powder as a raw material, the TiH ₂ The powder is subjected to ball milling passivation, all the raw materials are added into a ball milling tank, high-energy ball milling is directly carried out, a low-energy ball milling process is avoided, the yield strength of the titanium alloy obtained through subsequent induction heating sintering and hot extrusion is 1080MPa at room temperature, the tensile strength is 1230MPa, the elongation is 6%, and no obvious necking phenomenon exists.

Comparative example 3

step 1: commercially available-200 mesh titanium hydride powder was used.

Step 2: stock preparation

Will TiH ₂ Powder (-200 mesh), atomized Al powder (-200 mesh), Sn powder (-200 mesh), Zr powder (-200 mesh), Mo powder (-200 mesh), and Si powder (-30 mesh)0 mesh) and Y powder (-300 mesh) are respectively put into a vacuum oven for drying and degassing to remove impurities such as water vapor and the like on the surface of the material, and the specific process comprises the following steps: preserving the heat for 3 hours at 130 ℃ under the vacuum condition;

and step 3: mixed powder

And (3) placing the element raw material powder into a double-cone mixer, and fully mixing for 24 hours at the rotating speed of 60r/min under the protection of argon gas to obtain uniformly mixed powder.

And 4, step 4: pressing into blank

Filling the uniformly mixed powder into a cylindrical die, maintaining the pressure for 300s under the pressure of 800MPa after vibration compaction to form a blank by cold pressing, and demoulding by adopting a warm demoulding reverse ejection mode after the blank pressing is finished, wherein the concrete process comprises the following steps of: preheating a cylindrical die to 300 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain a powder compact; the relative density of the powder compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid the oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 10KHz, the powder pressed compact is heated to 1100 ℃ at the heating rate of 60 ℃/min, then the powder pressed compact is heated to 1200 ℃ at the heating rate of 40 ℃/min, and the temperature is kept for 10min, so that a sintered blank is obtained;

step 6: consolidation by hot extrusion

Under the same protective atmosphere as that of induction heating sintering, quickly transferring the sintered blank subjected to induction heating sintering into an extrusion cylinder preheated to 450 ℃ for hot extrusion at an extrusion ratio of 16:1 to obtain a high-density titanium alloy extruded bar.

A method for preparing a titanium alloy, which comprises the following steps,the difference from example 1 is that a commercially available TiH of-200 mesh was used ₂ The powder is used as a raw material, all the raw materials are added into a mixer and fully mixed for 24 hours at the rotating speed of 60r/min to obtain uniformly mixed powder, a high-energy ball milling process is not needed, a mechanical alloying process is not needed, the uniform dispersion effect of the Y powder in the mixed powder cannot be realized, the yield strength of the titanium alloy obtained by subsequent induction heating sintering and hot extrusion at room temperature is 978MPa, the tensile strength is 1150MPa, the elongation is 12%, and no obvious necking phenomenon exists, which is a standard cleavage fracture mode.

Comparative example 4

step 1: hydrogenation of titanium sponge

step 2: stock preparation

and step 3: preparation of mixed powder by synchronous low-energy ball milling

Under the protective atmosphere, putting the weighed titanium sponge hydride particles and all raw materials of each element powder into a ball milling tank together for sealing, carrying out low-energy ball milling on a planetary ball mill to crush the titanium sponge hydride particles into powder, and simultaneously mixing the raw material powder uniformly, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the mixed powder is obtained by low-energy ball milling for 1 hour at 200 rpm;

and 4, step 4: pressing into blank

The mixed powder after the low energy ball-milling does not pass through passivation treatment, avoids the mixing material to take place the oxidation in the air, under protective atmosphere, fills the mixed powder of misce bene in cylindrical die, vibrations are tight real back, and pressurize 300s under 800 MPa's pressure and carry out the cold pressing and press the base, presses to become the base and after finishing, adopts the reverse ejecting mode drawing of patterns of warm drawing of patterns, and concrete technology is: preheating a cylindrical die to 300 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain a powder compact; the relative density of the powder compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

step 6: hot extrusion consolidation

A preparation method of a titanium alloy, which is the same as that in example 1, and is different from that in step 3, all raw materials are added into a ball milling tank, low-energy ball milling is directly carried out, a high-energy ball milling process is not carried out, a mechanical alloying process is not carried out, a uniform dispersion effect of Y powder in mixed powder cannot be realized, the yield strength of the titanium alloy obtained through subsequent induction heating sintering and hot extrusion at room temperature is 990MPa, the tensile strength is 1165MPa, the elongation is 13.7%, and no obvious necking phenomenon exists, the titanium alloy is in a quasi-cleavage fracture mode, the mixed powder is only subjected to low-energy ball milling but not subjected to high-energy ball milling mechanical alloying, and the mechanical property of the titanium alloy prepared through subsequent induction sintering and hot extrusion is poor.

Comparative example 5

step 1: hydrogenation of titanium sponge

and 2, step: stock preparation

Under the protective atmosphere, putting the weighed hydrogenated titanium sponge particles and all raw materials of each element powder into a ball-milling tank together for sealing, firstly carrying out low-energy ball milling on a planetary ball mill to break the hydrogenated titanium sponge particles into powder, and simultaneously uniformly mixing the raw material powder, wherein the specific process comprises the following steps: the revolution and rotation ratio is 1:2, the ball material ratio is 5:1, and the ball milling is carried out for 3 hours at 200 rpm; and then carrying out high-energy ball milling after the low-energy ball milling is finished, uniformly mixing the Y powder in the mixed powder and simultaneously preparing ultrafine-grained mixed powder by mechanical alloying, wherein the specific process comprises the following steps: performing high-energy ball milling at 500rpm for 6 hours to obtain uniformly mixed superfine crystal mixed powder;

and 4, step 4: pressing into blank

After high-energy ball milling, the superfine crystal mixed powder has high activity and is easy to oxidize, and the superfine crystal mixed powder subjected to synchronous ball milling needs to be subjected to slow passivation treatment for 6 hours in a glove box. Filling passivated uniformly mixed superfine crystal mixed powder into a cylindrical die, keeping the pressure for 300s under 800MPa after vibration compaction to form a blank by cold pressing, and demoulding by adopting a warm demoulding reverse ejection mode after the pressing is finished, wherein the specific process comprises the following steps: preheating a cylindrical die to 400 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder compact; the relative density of the superfine crystal powder pressed compact is more than or equal to 85 percent.

And 5: rapid induction heating sintering and synchronous dehydrogenation

In order to avoid the oxidation of the powder pressed compact in the sintering and hot extrusion processes in the air atmosphere, under the protective atmosphere with the oxygen concentration lower than 100ppm, the superfine crystal powder pressed compact is placed in a medium-frequency electromagnetic induction coil of a medium-frequency induction heating system for rapid induction heating, the frequency of the medium-frequency electromagnetic induction coil is 10KHz, the medium-frequency electromagnetic induction coil is heated to 1100 ℃ at the heating rate of 60 ℃/min, then the medium-frequency electromagnetic induction coil is heated to 1200 ℃ at the heating rate of 40 ℃/min and is insulated for 10min, and a sintered blank is obtained;

step 6: hot extrusion consolidation

A titanium alloy preparation method, which is the same as that in the example 1, and is different in that in the step 4, the uniformly mixed ultrafine grain mixed powder prepared by high-energy ball milling is subjected to slow passivation treatment for 6 hours in a glove box, the oxygen content of the ultrafine grain mixed powder is increased in the passivation process, and the titanium alloy obtained by subsequent induction heating sintering and hot extrusion is subjected to stretching at room temperature to generate brittle fracture without plastic deformation and is in a brittle fracture mode; the invention directly presses the superfine crystal mixed powder with large activity after high-energy ball milling into a blank in the argon atmosphere without passivation treatment, thereby avoiding the oxidation of the mixed powder to a limited extent and being beneficial to obtaining the alloy material with excellent performance.

Comparative example 6

The method for preparing the near-alpha powder metallurgy titanium alloy of the embodiment is the same as the embodiment 1, except that: and (3) the hot extrusion process in the step 6 is not carried out, holes are remained in the sintered blank, the density is lower, the sintered blank is brittle at room temperature and has no plastic deformation, and the sintered blank is in a brittle fracture mode.

Comparative example 7

A powder metallurgy preparation method (CN200910308457.8) of a rare earth oxide-containing strengthening phase titanium alloy is different from embodiment 1 of the invention in that a raw material of Ti is hydrogenated and dehydrogenated titanium powder with high cost and high oxygen content, a rare earth element is added in a rare earth hydride mode, the hydrogenated and dehydrogenated titanium powder is fully mixed with other alloy powder, alloy element powder and the rare earth hydride in a mixer to prepare mixed powder, the prepared mixed powder has high oxygen content and large particle size, the mixed powder does not have a mechanical alloying process, and the rare earth element cannot be uniformly dispersed and distributed in the mixed powder. In the material preparation method, the powder compact is subjected to long-time high-temperature vacuum sintering, the structure is large, and the production period is long. In addition, the raw material uses hydrogenated dehydrogenated titanium powder, and the process that the hydrogenated titanium powder is decomposed to release hydrogen in the sintering process is avoided, so that the purpose of cleaning the surfaces of titanium powder particles can be achieved, and the oxygen content of the titanium alloy can be effectively reduced by using the hydrogenated titanium powder instead of the hydrogenated dehydrogenated pure titanium powder. The titanium alloy prepared by subsequent high-temperature deformation has the microstructure of alpha lamella, beta phase and nano yttrium oxide particles, and has the mechanical properties as follows: the tensile strength is 847-980 MPa, and the elongation is 10-22%. Comparative example 6 in the absence of the invention in example 1, low cost low oxygen content hydrogenated titanium sponge particles and other pure elemental powders or master alloy particles were used as starting materials by adding Y powder or YH powder to the starting materials ₂ Powder, and Y powder or YH powder is obtained by mechanical alloying of the mixed powder and high-energy ball mill through synchronous low-energy ball mill crushing ₂ The powder is uniformly dispersed in the ultra-fine grain mixed powder. Ultrafine powder prepared in example 1 of the present inventionPressing into blank without passivation treatment, and optionally pressing Y powder or YH ₂ The powder is uniformly dispersed in the ultra-fine grain mixed powder. In addition, comparative example 6 has no dehydrogenation process in the rapid short-time induction sintering process, the decomposition and release of hydrogen in the induction heating sintering process can clean the surface of titanium powder particles, and submicron Y is generated through solid-phase oxygen absorption and in-situ reaction ₂ O ₃ The reinforcing particles can further reduce the oxygen content of the alloy and simultaneously obtain the high-performance titanium alloy toughened by the submicron particles in dispersed distribution. In addition, the in situ reaction of the present invention produces submicron Y ₂ O ₃ The particles provide mass points for the nucleation of the micropores in the tensile deformation process and continuously release stress concentration at the interface, so that the PM titanium alloy is converted into a full-toughness fracture mode, and the fracture elongation is obviously improved. Therefore, compared with the high-performance near-alpha powder metallurgy titanium alloy material toughened by submicron particles, the high-performance near-alpha powder metallurgy titanium alloy material has the advantages of higher oxygen content, coarse structure, poorer comprehensive mechanical property, higher cost and long production period, and can not meet the use in the industrial field with higher requirement on the comprehensive mechanical property.

Claims

1. A submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy is characterized in that the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy consists of a titanium alloy matrix and submicron yttrium oxide particles dispersed in the titanium alloy matrix;

the mass percentage of the submicron yttrium oxide particles in the total mass of the high-performance near-alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles is 0.63-1.9 wt.%;

the raw material component requirements of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy comprise the following components in percentage by mass: al: 5.0 to 7.5%, Sn: 1.0-3.5%, Zr: 3.0-5.5%, Mo: 1-3.5%, Si: 0.05-1.5%, Y: 0.5-1.5% and the balance Ti;

the microstructure of the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy is a basket structure consisting of a fine alpha sheet layer, a discontinuous beta transition structure, a beta sheet layer and submicron yttrium oxide particles which are distributed in a dispersion manner; wherein the volume percentage of the fine alpha sheet layer is 70-80%; and a nano needle-shaped alpha phase is separated out in the discontinuous beta transition tissue;

the average thickness of the fine alpha sheet layer is 0.4-0.8 mu m, the width of the nano needle-shaped alpha phase is 50-300 nm, and the particle size of the submicron yttrium oxide particles is 300-1000 nm;

2. The method for preparing the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy according to claim 1, is characterized by comprising the following steps:

step 1: stock preparation

Weighing corresponding raw materials according to the raw material component requirements of the high-performance near alpha powder metallurgy titanium alloy toughened by the submicron yttrium oxide particles; the Ti raw material is hydrogenated sponge titanium particles, and is obtained by carrying out high-temperature hydrogenation treatment on the sponge titanium particles, and the high-temperature hydrogenation treatment process comprises the following steps: maintaining the hydrogen pressure of 1-1.5 bar at 400-750 ℃, preserving the heat for 2-5 h, and cooling along with the furnace;

step 2: synchronous ball mill

Under the protective atmosphere, carrying out low-energy ball milling on the weighed corresponding raw materials, and crushing and mixing to obtain mixed powder; wherein the ball milling speed of the low-energy ball milling is 100-200 rpm, and the ball milling lasts for 1-5 h;

then the mixed powder is subjected to high-energy ball milling mechanical alloying to obtain Y powder and/or YH powder ₂ Ultra-fine grain mixed powder with powder dispersed and distributed; wherein the ball milling speed of the high-energy ball milling mechanical alloying is 500-600 rpm, and the ball milling is carried out for 3-6 h;

and step 3: pressing into blank

and 4, step 4: sintering by heating and simultaneous dehydrogenation

and 5: consolidation by hot extrusion

3. The method for preparing a high performance near-alpha powder metallurgy titanium alloy toughened by submicron yttria particles according to claim 2, wherein in the step 2, the ball milling is one of a planetary ball mill or a stirring ball mill.

4. The method for preparing the submicron yttrium oxide particle toughened high-performance near-alpha powder metallurgy titanium alloy according to claim 2, wherein in the step 3, the pressed blank is demoulded by adopting a warm demoulding reverse ejection mode in the demould process, and the specific process is as follows: preheating a die to 100-500 ℃ before reverse ejection and demolding, and then performing reverse demolding to obtain an ultra-fine grain powder pressed blank; the relative density of the superfine crystal powder pressed compact is more than or equal to 85 percent.