阅读说明：本技术 一种提高高温氧化性能的TiAl合金及其制备方法 (TiAl alloy for improving high-temperature oxidation performance and preparation method thereof ) 是由 马腾飞 王玉鹏 王晓红 董多 朱冬冬 张元祥 周兆忠 于 2021-08-12 设计创作，主要内容包括：本发明公开了一种提高高温氧化性能的TiAl合金及其制备方法,属于表面防护领域。本发明用放电等离子烧结方法对TiAl预制合金粉和石墨烯粉末进行烧结,制备全片层TiAl合金,在α-(2)和γ片层间原位自生形成微纳米颗粒增强相。片层间弥散分布的微纳米颗粒增强相能够有效抑制氧在片层间的扩散,进而提高其抗氧化性能,850℃氧化增重100h约为普通TiAl合金在的80％。本发明从TiAl合金高温氧化机理出发,进行材料微观结构设计和调控,通过在扩散通道处引入第二相,阻碍氧的扩散,提高TiAl合金高温抗氧化性能,为解决金属材料高温抗氧化问题提供新的解决思路。(The invention discloses a TiAl alloy for improving high-temperature oxidation performance and a preparation method thereof, belonging to the field of surface protection. The invention uses a spark plasma sintering method to sinter TiAl pre-alloy powder and graphene powder to prepare fully lamellar TiAl alloy, and alpha TiAl alloy 2 And forming a micro-nano particle reinforced phase in situ between the gamma sheets. The micro-nano particle reinforced phase which is dispersed and distributed among the lamellas can effectively inhibit the diffusion of oxygen among the lamellas, thereby improving the oxidation resistance of the micro-nano particle reinforced phase, and the oxidation weight gain of the micro-nano particle reinforced phase at 850 ℃ is about 80 percent of that of the common TiAl alloy after 100 hours. The invention starts from the TiAl alloy high-temperature oxidation mechanism,the microstructure design and regulation of the material are carried out, and the second phase is introduced into the diffusion channel to block the diffusion of oxygen, improve the high-temperature oxidation resistance of the TiAl alloy and provide a new solution for solving the problem of high-temperature oxidation resistance of the metal material.)

1. The TiAl alloy for improving the high-temperature oxidation performance is characterized in that the TiAl alloy is of a full lamellar structure and is prepared by adding alpha₂And gamma sheet layer in-situ self-generated form micro-nano particle reinforced phase to block oxygen along alpha₂And gamma interface diffusion, thereby improving the high-temperature oxidation resistance of the TiAl alloy.

2. The TiAl alloy for improving high temperature oxidation properties of claim 1, wherein the particulate reinforcing phase is α₂And gamma sheet layer, with size of 0.01-10 μm, and particle reinforcing phase dispersed in the matrix.

3. The TiAl alloy for improving high-temperature oxidation performance of claim 1, wherein the TiAl alloy is Ti-48Al-2Cr-2 Nb.

4. The TiAl alloy for improving the high-temperature oxidation performance of claim 1, wherein the TiAl alloy is formed by sintering TiAl pre-alloy powder and graphene oxide powder through a spark plasma sintering device.

5. The TiAl alloy for improving high-temperature oxidation performance of claim 4, wherein the chemical composition of the TiAl prealloy powder is Al: 43-48, Nb: 2-8, Cr: 0-2, V: 0-2, Mo: 0-3, trace element B, C and Re content less than 0.1, and Ti as the rest.

6. The TiAl alloy for improving the high-temperature oxidation performance of claim 4, wherein the TiAl pre-alloy powder is prepared by adopting a rotary electrode pulverization method or a gas atomization method, and the particle size is 53-150 μm.

7. A method for preparing the TiAl alloy as set forth in any one of claims 1 to 6, comprising the steps of:

uniformly mixing TiAl prealloy powder and graphene oxide powder by ball milling, drying, sintering by adopting spark plasma sintering equipment, wherein the sintering temperature is 1250-1350 ℃, carbon atoms in the graphene are rapidly diffused and dissolved in interstitial positions of crystal lattices in the sintering process, and Ti precipitated from supersaturated solid solution in the sintering cooling process₂Good coherent characteristics of AlC micro-nano particles and gamma phase are maintained, so that alpha phase and gamma phase are consistent₂And forming a micro-nano particle reinforced phase in situ between the gamma sheets, and finally obtaining the bulk TiAl alloy material with a compact full-sheet structure.

8. The method of claim 7, wherein the temperature is maintained for 5min during the sintering process, and the sintering pressure is 45 MPa.

9. The preparation method of claim 7, wherein the ball-to-material ratio in the ball milling process is less than or equal to 1, the rotation speed of the ball mill is controlled at 300r/min, the ball milling time is 360min, and the uniformly mixed powder obtained after ball milling is dried in a vacuum box at the drying temperature of 300 ℃ for 240 min.

10. The method according to claim 7, wherein the mass percentage of the graphene oxide to the TiAl prealloyed powder is 0.1 to 1 wt.% when the two powders are mixed.

Technical Field

The invention belongs to the field of surface protection, and particularly relates to a TiAl alloy for improving high-temperature oxidation performance and a preparation method thereof.

Background

The TiAl alloy is an advanced light high-temperature structural material, has excellent comprehensive properties such as low density, high specific strength and good creep resistance, and is one of key materials capable of partially replacing nickel-based high-temperature alloy. Currently, TiAl alloy is successfully applied to aeroengine compressor blades and low-pressure turbine blades, and has a good weight reduction effect. With the development of aerospace industry, the service temperature of materials is further increased, the service environment is more complex, higher requirements are put on the materials, and the materials are required to have higher service temperature and more excellent comprehensive performance. Therefore, the increase of the service temperature of the TiAl alloy is an important direction of the development of the alloy, a series of work is mainly carried out from the aspect of alloy component design and surface protection, the service temperature of the TiAl alloy can be increased by 50 ℃ by adding the Nb element with high content, and the direction is indicated for the high-temperature development of the TiAl alloy.

The applicant starts from the oxidation mechanism of the TiAl alloy and finds that the TiAl alloy component is in contact with atoms such as oxygen, nitrogen and the like in the air at high temperature, the atoms form physical adsorption on the surface of the TiAl alloy component, and partial oxygen molecules diffuse into interstitial positions in the matrix or are replaced with metal atoms in the matrix along with the prolonging of time. The interface is often a good diffusion channel, and the TiAl alloy is mainly based on a fully lamellar structure and has a large number of interfaces, which is the root cause of poor high-temperature oxidation resistance. Therefore, how to inhibit the diffusion of oxygen in the diffusion channel is probably the key to improve the high-temperature oxidation resistance of the TiAl alloy, the diffusion channel of oxygen is cut off by in-situ self-generation of the particles with the micro-nano scale at the interface, the high-temperature oxidation resistance is further improved, and a new solution idea is provided for the tissue control and the performance improvement of the TiAl alloy.

Disclosure of Invention

The invention aims to improve the high-temperature oxidation resistance of the TiAl alloy by inhibiting oxygen diffusion through in-situ authigenic micro-nano particles at an interface, provides a new idea for designing the oxidation-resistant TiAl alloy, and provides the TiAl alloy for improving the high-temperature oxidation resistance and the preparation method thereof based on the new idea.

In order to achieve the purpose, the invention adopts the following specific technical scheme:

in a first aspect, the invention provides a TiAl alloy for improving high-temperature oxidation performance, which is characterized in that the TiAl alloy is in a fully lamellar structure and is prepared by alpha₂And gamma sheet layer in-situ self-generated form micro-nano particle reinforced phase to block oxygen along alpha₂And gamma interface diffusion, thereby improving the high-temperature oxidation resistance of the TiAl alloy.

Preferably, the particulate reinforcing phase is at α₂And gamma sheet layer, with size of 0.01-10 μm, and particle reinforcing phase dispersed in the matrix.

Preferably, the TiAl alloy is Ti-48Al-2Cr-2 Nb.

Preferably, the TiAl alloy is formed by sintering TiAl prealloy powder and graphene oxide powder through spark plasma sintering equipment.

Further, the chemical components of the TiAl prealloy powder are Al: 43-48, Nb: 2-8, Cr: 0-2, V: 0-2, Mo: 0-3, trace element B, C and Re content less than 0.1, and Ti as the rest.

Furthermore, the TiAl prealloy powder is prepared by adopting a rotating electrode powder preparation method or a gas atomization method, and the particle size is 53-150 microns.

In a second aspect, the present invention further provides a method for preparing the TiAl alloy according to any one of the first aspect, comprising the steps of:

uniformly mixing TiAl prealloy powder and graphene oxide powder by ball milling, drying, sintering by adopting spark plasma sintering equipment, wherein the sintering temperature is 1250-1350 ℃, carbon atoms in the graphene are rapidly diffused and dissolved in interstitial positions of crystal lattices in the sintering process, and Ti precipitated from supersaturated solid solution in the sintering cooling process₂The good coherent characteristic of AlC micro-nano particles and gamma phase is kept, and the alpha phase is₂And forming a micro-nano particle reinforced phase in situ between the gamma sheets, and finally obtaining the bulk TiAl alloy material with a compact full-sheet structure.

Preferably, the temperature is kept for 5min in the sintering process, and the sintering pressure is 45 MPa.

Preferably, the ball-material ratio in the ball milling process is less than or equal to 1, the rotating speed of the ball mill is controlled at 300r/min, the ball milling time is 360min, and the uniformly mixed powder obtained after ball milling is dried in a vacuum box at the drying temperature of 300 ℃ for 240 min.

Preferably, when the two powders are mixed, the mass percentage of the graphene oxide relative to the TiAl prealloy powder is 0.1-1 wt.%.

The invention also aims to provide the TiAl-based composite material obtained by the preparation method.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the method, in-situ self-generated micro-nano particles at the interface are reasonably utilized, so that the diffusion of oxygen is hindered, and the high-temperature oxidation resistance of the TiAl alloy with the full lamellar structure is improved;

(2) the in-situ self-generated micro-nano particles have the characteristics of composite materials, can improve the high-temperature oxidation resistance of the TiAl alloy and improve the mechanical property of the TiAl alloy, and further broadens the use temperature range of the TiAl alloy;

(3) the in-situ self-generated micro-nano particles have great significance for TiAl alloy composition design and tissue structure regulation;

(4) the TiAl alloy material prepared by the method has huge application potential in the fields of aerospace, automobile manufacturing, military industry and the like.

Drawings

FIG. 1 shows a fully lamellar TiAl alloy prepared according to the present invention and having an alpha structure₂And forming micro-nano particles in situ among the gamma sheets.

FIG. 2 is an oxidation kinetics curve for 750 ℃ and 850 ℃ cyclic oxidation resistance.

Detailed Description

The invention will be further elucidated and described with reference to the drawings and the detailed description.

The invention aims to provide a TiAl alloy for improving high-temperature oxidation performance, wherein the TiAl alloy is in a full lamellar structure and is prepared by adding alpha₂And gamma sheet layer in-situ self-generated form micro-nano particle reinforced phase to block oxygen along alpha₂And gamma interface diffusion, thereby improving the high-temperature oxidation resistance of the TiAl alloy.

The TiAl alloy with the fully lamellar structure can be sintered and molded by TiAl prealloy powder and graphene oxide powder through spark plasma sintering equipment. The particle-reinforced phase may be at alpha during sintering₂And gamma sheet layers are formed in situ, the size of the gamma sheet layers is 0.01-10 mu m, the gamma sheet layers belong to the micro-nano grade, and the particle reinforcing phase is dispersed in the matrix.

The preparation method of the TiAl alloy for improving the high-temperature oxidation performance comprises the following steps:

(1) preparing TiAl prefabricated alloy powder by adopting a rotating electrode powder preparation method or a gas atomization method, wherein the chemical components of the TiAl prefabricated alloy powder are as follows by atomic percent: 43-48, Nb: 2-8, Cr: 0-2, V: 0-2, Mo: 0-3, the content of trace element B, C, Re is less than 0.1, the rest is Ti, and the particle size of the powder is 53-150 μm. In this composition, the elements of V and Mo may be absent. In addition, the graphene doped into the TiAl prealloy powder is graphene oxide powder, and the two powders are mixed according to the required proportion (the content of the graphene oxide is 0.1-1 wt.%) and can be dried after being mixed by a mechanical ball mill. In order to avoid the pollution of the ball milling tank, the invention preferably adopts a specially-made titanium alloy ball milling tank. As the room temperature plasticity of the TiAl alloy is poor, agate balls are adopted for ball milling in order to avoid powder crushing in the ball milling process, and the ball-to-material ratio is kept to be less than or equal to 1. The rotation speed of the ball mill is preferably controlled at 300r/min, and the ball milling time is preferably 360 min. And drying the powder which is subjected to ball milling and uniform mixing in a vacuum box, wherein the drying temperature is preferably 300 ℃, the drying time is preferably 240min, and removing water to obtain the mixed powder.

(2) Sintering and molding the dried mixed powder in the step (1) by adopting a spark plasma sintering device, wherein the sintering temperature is 1250-1350 ℃ (the sintering temperature is selected in TiAl alloy T_αAbove the temperature), keeping the temperature for a certain time, and cooling to room temperature to obtain the compact fully lamellar TiAl alloy. The sample size of TiAl alloy is preferably controlled to be phi 10-50mm, and can be adjusted by selecting a corresponding die. The heat preservation in the sintering process is preferably 5min, and the sintering pressure is preferably 45 MPa.

Of course, the specific parameters in the preparation process of the TiAl alloy may be optimized according to actual conditions, and the parameters are only recommended parameters.

The following examples are provided to demonstrate specific effects of the present invention.

Examples

In the embodiment, a TiAl alloy preparation method for improving high-temperature oxidation performance is provided, and the method takes Ti-48Al-2Cr-2Nb prealloy powder and graphene oxide powder prepared by a rotary electrode method as raw materials, wherein the particle sizes of the powder are 53-150 μm, and the addition amount of the graphene oxide relative to the TiAl prealloy powder is about 0.5 wt.%. The preparation method comprises the following specific steps:

(1) 50g of Ti-48Al-2Cr-2Nb powder and 2.5g of graphene oxide powder are weighed and placed in a vacuum bag.

(2) And placing the weighed powder into a titanium alloy ball milling tank, and mechanically ball milling and uniformly mixing the powder, wherein the ball milling time is 360min, the rotating speed of the ball mill is 300r/min, the material ratio is 1:1, and the balls are agate balls.

(3) And (3) placing the powder after ball milling and mixing in a vacuum box for vacuum drying at the drying temperature of 300 ℃ for 240 min.

(4) And (2) performing powder sintering by adopting a spark plasma sintering device, placing the mixed powder after vacuum drying in a graphite die with the diameter of 50mm before sintering, then preserving the heat for 5min at the sintering temperature of 1300 ℃ for sintering, wherein the sintering pressure is 45MPa, and cooling to obtain the TiAl alloy block material with the compact fully lamellar structure.

(5) In order to investigate the tissue structure and the high-temperature oxidation resistance of the obtained TiAl alloy, a sample (marked as 0.5GO) of 0.5cm multiplied by 0.5cm is cut on the TiAl alloy block material by adopting linear cutting so as to facilitate tissue observation and oxidation resistance experiments.

(6) The sample was processed according to the standard preparation method for gold phase, and the microstructure observation of the gold phase and the microstructure observation of the scanning electron microscope were performed as shown in fig. 1. The microstructure in a sintering state is a full-lamellar structure (figure 1a), graphene has the characteristics of self two-dimensional structure and high activity, carbon atoms rapidly diffuse and are dissolved in interstitial positions of crystal lattices at a sintering high temperature, and Ti is separated out from a supersaturated solid solution in the sintering cooling process₂The AlC micro-nano particles and the gamma phase keep good coherent characteristics, micro-nano scale particles (shown in figure 1b) are formed in situ between alpha 2 and gamma sheet layers, and the particle size is 0.1-2 mu m.

(7) And then placing the TiAl alloy sample (0.5GO group) cleaned by ultrasonic waves into different high-purity alumina crucibles, respectively carrying out cyclic high-temperature oxidation experiments at 750 ℃ and 850 ℃, drawing an oxidation weight gain curve, and investigating the high-temperature oxidation resistance of the two materials.

Meanwhile, for comparison, a set of control TiAl alloy samples is also arranged in the embodiment, and the difference between the control set and the preparation method of the embodiment is that graphene oxide powder is not added, only Ti-48Al-2Cr-2Nb prealloy powder is used for sintering, and the rest of the preparation methods are the same as the preparation methods of the 0.5GO group in the embodiment, so that the TiAl alloy samples in the control set are marked as the 0GO group. And (3) carrying out a cyclic high-temperature oxidation experiment on the TiAl alloy sample of the 0GO group at 750 ℃ and 850 ℃ respectively according to the same method, drawing an oxidation weight gain curve, and evaluating the high-temperature oxidation resistance of the alloy.

Finally, the oxidation kinetics curves obtained for the alloys of the 0GO and 0.5GO groups at 750 ℃ and 850 ℃ are shown in fig. 2. As can be seen from figure 2, the micro-nano particle reinforced phase which is self-generated in situ and is dispersed among the sheets can effectively inhibit the diffusion of oxygen among the sheets, and further the high-temperature oxidation resistance of the TiAl alloy is obviously improved. The TiAl alloy without the added graphene oxide powder cannot form a micro-nano particle reinforced phase, so that the high-temperature oxidation resistance of the TiAl alloy is poor. From the quantification result, compared with the common TiAl alloy, the oxidation weight gain of the TiAl alloy prepared by the embodiment at 850 ℃ for 100h is about 80% of that of the common TiAl alloy.

Therefore, the invention starts from the TiAl alloy high-temperature oxidation mechanism, carries out material microstructure design and regulation, and introduces a second phase at a diffusion channel to block the diffusion of oxygen, improve the high-temperature oxidation resistance of the TiAl alloy, and provides a new solution for solving the problem of high-temperature oxidation resistance of metal materials.

The above-described embodiments are merely preferred embodiments of the present invention, which should not be construed as limiting the invention. Various changes and modifications may be made by one of ordinary skill in the pertinent art without departing from the spirit and scope of the present invention. Therefore, the technical scheme obtained by adopting the mode of equivalent replacement or equivalent transformation is within the protection scope of the invention.