Ultrafine-grained high-density tantalum-tungsten alloy and method for preparing same

Abstract

The application discloses a preparation method of superfine-grain high-density tantalum-tungsten alloy, and the tantalum-tungsten alloy comprises the following components and their mass percentages: 2.5% of tungsten, and the rest is tantalum. The preparation method comprises the following steps: first, preparing nanometer tungsten powder with ultra-low oxygen content; then, mixing tantalum powder and tungsten powder according to a proportion to obtain a composite powder in a vacuum; then, sintering the composite powder loaded in a mold to obtain a tantalum-tungsten sintered body, wherein the sintering temperature is 1355-1395 DEG C, the sintering pressure is 55-65 MPa, the holding time is 3-3.5 min, the vacuum degree is 10 ‑3 ~10 ‑5 Pa, the sintered body is cooled to room temperature in a furnace after sintering is completed, and then, cold rolling is carried out, the reduction is 95-97%, and finally, vacuum heat treatment annealing is carried out, wherein the annealing temperature is 1325-1345 DEG C, the annealing time is 35-45 min, and the vacuum degree is 10 ‑3 ~10 ‑5 Pa, and thus a superfine-grain high-density tantalum-tungsten alloy with a density of 99.93-99.99% and a grain size of 10-35 nm is obtained. The prepared tantalum-tungsten alloy has fine grains and high density, and can be applied to important engineering fields such as space vehicles and weapon equipment, and has very important application value.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tantalum-tungsten alloy, in particular to a kind of ultrafine grain high-density tantalum-tungsten alloy and its preparation method. BACKGROUND

[0002] Tantalum-tungsten alloy is a kind of infinite solid solution with a certain amount of tungsten (W) element added to the tantalum (Ta) matrix, which has excellent physical and chemical properties. Tantalum-tungsten alloy combines the advantages of tantalum and tungsten, mainly in high melting temperature, high density, high hardness, good bending strength, wear resistance, high temperature resistance and corrosion resistance, etc. It is widely used in aerospace, aviation, navigation, military, national defense, medical and other fields.

[0003] Currently, the preparation methods of tantalum-tungsten alloy are mainly electron beam melting and powder metallurgy. The tantalum billet prepared by electron beam melting has coarse grains, obvious anisotropy and poor mechanical properties. Although the tantalum billet prepared by powder metallurgy process has fine grains, relatively uniform structure and no anisotropy, the characteristics of powder metallurgy solid phase sintering determine that the tantalum billet is difficult to achieve near full density, and the impurity content is high, which greatly reduces the room temperature plastic deformation ability of tantalum alloy. From the development trend of materials, ultrafine grain and high density are important characteristics of high-performance materials. Grain nanocrystallization and near full density are important directions for the development of high-tech materials in the future. Therefore, how to realize the nanocrystallization of tantalum-tungsten alloy and improve its density is a great challenge for advanced materials scientists. SUMMARY

[0004] In order to solve the problems in the prior art, the present application provides an ultrafine grain high-density tantalum-tungsten alloy and its preparation method. The tantalum-tungsten alloy prepared by the method has high density, fine grain structure and simple and controllable process.

[0005] In order to achieve the above purpose, the specific scheme adopted by the present application is as follows:

[0006] An ultrafine grain high-density tantalum-tungsten alloy, comprising the following components and their mass percentages: tungsten 2.5%, tantalum 97.5%.

[0007] As a preferred scheme, the density of the tantalum-tungsten alloy is 99.93~99.99%, and the grain size is 10~35nm.

[0008] A preparation method of an ultrafine grain high-density tantalum-tungsten alloy, comprising the following steps:

[0009] S1, preparing a nano-tungsten powder with ultra-low oxygen content;

[0010] S2, the nano-tungsten powder and high-purity tantalum powder are placed in a ball mill jar according to a preset ratio, vacuumized to a vacuum degree of 10-3~10-5Pa, mixed by using a mixer at a rotating speed of 65~70r / min for 5~10h to obtain a composite powder;

[0011] S3, the composite powder is filled into a mold, and then the mold is placed into a vacuum discharge plasma hot-pressing sintering furnace for sintering and forming, the sintering temperature is 1355~1395℃, the sintering pressure is 55~65MPa, the holding time is 3~3.5min, the vacuum degree is 10 -3 ~10 -5 Pa, and the sintering is completed by cooling to room temperature in the furnace to obtain a tantalum-tungsten sintered body;

[0012] S4, the tantalum-tungsten sintered body is cold-rolled with a reduction of 95~97%;

[0013] S5, the tantalum-tungsten alloy after rolling is vacuum heat-treated and annealed, the annealing temperature is 1325~1345℃, the annealing time is 35~45min, and the vacuum degree is 10 -3 ~10 -5 Pa, to obtain an ultra-fine-grained high-density tantalum-tungsten alloy.

[0014] As a preferred solution, in step S1, the particle size of the nano-tungsten powder is 5~8nm, and the oxygen content is 20~30ppm.

[0015] As a preferred solution, in step S1, the preparation method of the nano-tungsten powder is:

[0016] S11, ammonium metatungstate with a purity of ≥99.99% is selected and dissolved in distilled water to form a solution, and the concentration of the solution is controlled at 1~3mol / L;

[0017] S12, a tungsten-containing precursor is formed by gas flow atomization drying, and after calcination and reduction treatment, a nano-tungsten powder with ultra-low oxygen content is obtained.

[0018] As a preferred solution, in step S12, the temperature of the gas flow atomization drying is 280~300℃.

[0019] As a preferred solution, in step S2, the purity of the high-purity tantalum powder is ≥99.99%, and the particle size is 100nm.

[0020] As a preferred solution, in step S3, the thickness of the tantalum-tungsten sintered body is 3~5mm, the density is 94~96%, and the grain size is 200~350nm.

[0021] As a preferred solution, in step S4, the pass of cold rolling is 5.

[0022] Beneficial effects:

[0023] 1)、Firstly, the present application adopts nanometer tungsten powder and high-purity tantalum powder to obtain a composite powder for preparing a tantalum-tungsten alloy. The tungsten powder is nanometer tungsten powder with ultra-low oxygen content, which can play a pinning effect in the powder metallurgy process, thereby refining the matrix grain. Secondly, by process control, the impurity content in the powder is strictly controlled, and the purity of the powder is improved, which is helpful for the densification of sintering, thereby obtaining a high-density material. At the same time, Ta and W are both refractory metal elements, and the sintering densification is difficult. The ordinary sintering method is not feasible. After in-depth study of the related principles of powder metallurgy, it is found that under the conditions of high temperature, high vacuum and high pressure, the deformation and displacement of the powder particles can be greatly promoted, and the spheroidization and disappearance process of the pores can be strongly promoted, thereby realizing the high densification of the tantalum-tungsten alloy. Combined with the characteristics of powder sintering, the sintered material will always have residual pores. Subsequently, through pressure deformation treatment, the grain deforms to a great extent, the dislocation density increases, a large number of fine and broken crystals are generated, and the residual pores are eliminated. Combined with recrystallization annealing treatment, the dislocation movement in the grain is intensified, and new grains with smaller size are generated, thereby realizing ultra-fine crystallization and further improving the density of the material.

[0024] 2)、The process for preparing the tantalum-tungsten alloy material is simple and controllable. The prepared tantalum-tungsten alloy material has excellent main performance indicators (the highest density reaches 99.99%, and the grain size is as low as 10 nm). It can be used in important engineering fields such as space vehicles and weapon equipment, and has very important application value. DETAILED DESCRIPTION

[0025] The technical solutions of the present application will be described clearly and completely in combination with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor belong to the protection scope of the present application.

[0026] The present application discloses a kind of ultra-fine grain high-density tantalum-tungsten alloy and preparation method thereof, wherein the component and its mass percentage of tantalum-tungsten alloy are as follows: tungsten 2.5%, tantalum 97.5%. The preparation method of ultra-fine grain high-density tantalum-tungsten alloy mainly includes the following steps:

[0027] S1, prepare nanometer tungsten powder;

[0028] S11, select ammonium metatungstate with purity ≥99.99%, dissolve it in distilled water to form a solution, and the concentration of the solution is controlled at 1-3 mol / L;

[0029] S12, carry out airflow atomization drying at a temperature of 280-300 DEG C to form a tungsten-containing precursor, and then sinter in a pure hydrogen atmosphere (hydrogen flow is 50 m3 carried out for 5 min at 650 DEG C and for 8 min at 820 DEG C to realize calcination and reduction of the powder, so that the nano-tungsten powder with ultra-low oxygen content is obtained; wherein the particle size of the nano-tungsten powder is 5-8 nm, and the oxygen content is 20-30 ppm;

[0030] S2, the nano-tungsten powder prepared in step S1 and high-purity tantalum powder with a purity of ≥99.99% and a particle size of 100 nm are weighed accurately according to a preset ratio, and then placed in a tungsten material ball mill tank, vacuumized to a vacuum degree of 10 -3 ~10 -5 Pa, mixed by using a mixer at a speed of 65-70 r / min for 5-10 h to obtain a composite powder;

[0031] S3, the composite powder is filled into a mold made of tungsten steel, and then the mold is placed in a vacuum discharge plasma hot-pressing sintering furnace for sintering and forming, the sintering temperature is 1355-1395 DEG C, the sintering pressure is 55-65 MPa, the holding time is 3-3.5 min, and the vacuum degree is 10 -3 ~10 -5 Pa, and after sintering, the furnace is cooled to room temperature to obtain a tantalum-tungsten sintered body; the thickness of the tantalum-tungsten sintered body is 3-5 mm, the density is 94-96%, and the grain size is 200-350 nm;

[0032] S4, the tantalum-tungsten sintered body is cold-rolled with a reduction of 95-97%;

[0033] S5, the tantalum-tungsten sintered body after rolling is subjected to vacuum heat treatment annealing, the annealing temperature is 1325-1345 DEG C, the annealing time is 35-45 min, and the vacuum degree is 10 -3 ~10 -5 Pa, to obtain an ultra-fine-grained high-density tantalum-tungsten alloy, the density of the ultra-fine-grained high-density tantalum-tungsten alloy is 99.93-99.99%, and the grain size is 10-35 nm.

[0034] The technical solutions of the present application will be described in detail below in conjunction with specific examples.

[0035] Example 1

[0036] S1, ammonium metatungstate with a purity of ≥99.99% is selected, dissolved in distilled water to form a solution, the concentration is controlled at 1 mol / L, and the tungsten-containing precursor is formed by gas flow atomization drying, and the ultra-low oxygen content nano-tungsten powder is obtained by calcination and reduction treatment, the particle size is 5 nm, and the oxygen (O) content is 20 ppm;

[0037] S2, select high purity tantalum (Ta) powder with purity ≥99.99% and particle size of 100 nm, accurately weigh the Ta powder and the obtained W powder according to the predetermined ratio using a balance, and then put them into a ductile iron tank made of tungsten material, extract high vacuum (10 -5 Pa), mix using a mixer at a speed of 70 r / min for 5 h, and obtain a composite powder;

[0038] S3, fill the obtained composite powder into a mold made of tungsten steel material, and then put the mold into a vacuum discharge plasma hot pressing sintering furnace for sintering and forming, the sintering temperature is 1355℃, the sintering pressure is 65MPa, the holding and pressure maintaining time is 3min, the vacuum degree is 10 -5 Pa, after sintering, the furnace is cooled to room temperature, and a tantalum-tungsten sintered body with a thickness of 3mm, a density of 96% and a grain size of 200nm is obtained;

[0039] S4, cold rolling of the tantalum-tungsten sintered body on a rolling mill for 5 passes with a reduction of 97%, and finally vacuum heat treatment annealing at an annealing temperature of 1325℃ for 45min with a vacuum degree of 10-5Pa, to obtain an ultra-fine-grained high-density tantalum-tungsten alloy.

[0040] The density of the ultra-fine-grained high-density tantalum-tungsten alloy prepared in this embodiment is 99.99%, and the grain size is 10nm.

[0041] Example 2

[0042] The process of this embodiment is basically the same as that of Example 1, but the process parameters are different:

[0043] (1) In step S1, the solution concentration is controlled at 3mol / L, the particle size of the nano-tungsten powder is 8nm, and the oxygen (O) content is 30ppm;

[0044] (2) In step S2, high vacuum (10 -3 Pa) is extracted, and mixing is carried out using a mixer at a speed of 65 r / min for 10 h;

[0045] (3) In step S3, the sintering temperature is 1395℃, the sintering pressure is 55MPa, the holding and pressure maintaining time is 3.5min, and the vacuum degree is 10 -3 Pa, and a tantalum-tungsten sintered body with a thickness of 5mm is obtained;

[0046] (4) In step S4, the cold rolling reduction is 95%, the vacuum heat treatment annealing temperature is 1345℃, the annealing time is 35min, and the vacuum degree is 10 -3 Pa.

[0047] The sintered tantalum-tungsten body obtained in the embodiment has a density of 94% and a grain size of 350 nm, and the ultra-fine-grained high-density tantalum-tungsten alloy obtained by rolling and vacuum heat treatment annealing has a density of 99.93% and a grain size of 35 nm.

[0048] Embodiment 3

[0049] The process of the embodiment is basically the same as that of Embodiment 1, but the process parameters are different.

[0050] (1) In step S1, the solution concentration is controlled at 2 mol / L, the nano-tungsten powder has a particle size of 6.5 nm, and the oxygen (O) content is 25 ppm;

[0051] (2) In step S2, high vacuum (10 -4 Pa) is extracted, and the mixture is mixed by using a mixer at a rotating speed of 68 r / min for 8 h;

[0052] (3) In step S3, the sintering temperature is 1375℃, the sintering pressure is 59 MPa, the holding and pressure-keeping time is 3.2 min, the vacuum degree is 10 -4 Pa, and a tantalum-tungsten sintered body with a thickness of 4 mm is obtained;

[0053] (4) In step S4, the cold rolling reduction is 96%, the vacuum heat treatment annealing temperature is 1335℃, the annealing time is 40 min, and the vacuum degree is 10 -4 Pa.

[0054] The sintered tantalum-tungsten body obtained in the embodiment has a density of 94% and a grain size of 350 nm, and the ultra-fine-grained high-density tantalum-tungsten alloy obtained by rolling and vacuum heat treatment annealing has a density of 99.93% and a grain size of 35 nm.

[0055] The above description is only a preferred embodiment of the present application, and is not intended to limit the present application in any form. Any equivalent transformation or modification based on the essence of the present application should be covered within the protection scope of the present application.

Claims

1. A method for producing an ultrafine-grained high-density tantalum-tungsten alloy, characterized by comprising: The ultra-fine grain high-density tantalum-tungsten alloy has a mass percentage of 2.5% tungsten and 97.5% tantalum. ​ The preparation method of the ultra-fine grain high-density tantalum-tungsten alloy comprises the following steps: S1, preparing nano-tungsten powder with ultra-low oxygen content, wherein the oxygen content of the nano-tungsten powder is 20-30 ppm; S2, the nano-tungsten powder and high-purity tantalum powder are placed in a ball mill jar according to a preset ratio, vacuumized to a vacuum degree of 10 -3 ~10 -5 Pa, mixing is performed by using a mixer, the rotating speed is 65~70 r / min, and the mixing time is 5~10 h, to obtain a composite powder; S3, filling the composite powder into a mold, and then placing the mold into a vacuum discharge plasma hot-pressing sintering furnace to sinter and form, the sintering temperature being 1355-1395℃, the sintering pressure being 55-65MPa, the holding time being 3-3.5min, and the vacuum degree being 10 -3 ~10 -5 Pa, and then cooling to room temperature to obtain a tantalum-tungsten sintered body; S4, cold rolling the tantalum-tungsten sintered body with a reduction of 95-97%; S5, the tantalum-tungsten alloy after rolling is subjected to vacuum heat treatment annealing, the annealing temperature is 1325-1345℃, the annealing time is 35-45min, and the vacuum degree is 10 -3 ~10 -5 Pa, that is, the superfine-grained high-density tantalum-tungsten alloy is obtained.

2. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 1, characterized in that, The density of the tantalum-tungsten alloy is 99.93-99.99%, and the grain size is 10-35 nm.

3. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 1, characterized in that, In step S1, the particle size of the nano-tungsten powder is 5-8 nm.

4. The method for preparing an ultrafine-grained, highly dense tantalum-tungsten alloy according to claim 1 or 3, characterized in that, In step S1, the nano-tungsten powder is prepared by the following method: S11, selecting ammonium metatungstate with a purity of ≥99.99% and dissolving it in distilled water to form a solution, wherein the concentration of the solution is controlled at 1-3 mol / L; S12, forming a tungsten-containing precursor by gas flow atomization drying, and obtaining nano-tungsten powder with ultra-low oxygen content by calcination and reduction treatment.

5. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 4, characterized in that, In step S12, the temperature of the gas flow atomization drying is 280-300℃.

6. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 1, characterized in that, In step S2, the high-purity tantalum powder has a purity of ≥99.99% and a particle size of 100 nm.

7. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 1, characterized in that, In step S3, the thickness of the tantalum-tungsten sintered body is 3-5 mm, the density is 94-96%, and the grain size is 200-350 nm.

8. The method for preparing an ultrafine-grained, high-density tantalum-tungsten alloy according to claim 1, characterized in that, In step S4, the cold rolling is performed for 5 passes.