Low-oxygen high-strength TZM alloy material and preparation method thereof

Abstract

The application provides a low-oxygen high-strength TZM alloy material and a preparation method thereof. The grain of the low-oxygen high-strength TZM alloy material is an equiaxed crystal structure, is randomly oriented, is consistent in performance in all directions, and has an average grain size of 25-35 microns. The TZM alloy material has the advantages of high density, low oxygen content, high strength, strong heat dissipation capacity and good thermal shock resistance.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of powder metallurgy, and particularly relates to a low-oxygen high-strength TZM alloy material and a preparation method thereof. BACKGROUND

[0002] The TZM alloy is formed by adding a certain amount of Ti, Zr, C and other elements in Mo-based, forming Mo-Ti solid solution strengthening phase and dispersed titanium carbide and zirconium carbide reinforcing phase, so that the recrystallization temperature can be improved and the high-temperature performance of the alloy can be improved. Therefore, due to the advantages of high melting point, high strength, stable high-temperature performance, high elastic modulus, small linear expansion coefficient, low vapor pressure and strong corrosion resistance, the TZM alloy is widely used in high-temperature and high-vacuum fields.

[0003] The high-temperature and high-vacuum environment has very strict requirements for the TZM alloy material. For example, the target disc in the CT ball tube in the medical instrument field, the heating body in the high-vacuum welding equipment field, and the base material used in the material brazing field all require high recrystallization temperature, good toughness and high-temperature performance, which is closely related to the gas content and impurity content in the TZM alloy. The performance of the TZM alloy is better when the gas content is low and the purity is high. Therefore, it is extremely critical to prepare a low-oxygen high-strength TZM alloy.

[0004] At present, there are mainly three process routes for preparing the TZM alloy: (1) melting method, which is to mix molybdenum, titanium, zirconium and other elements in a certain proportion for melting, and then to obtain TZM bars or slabs by casting or mechanical pressure processing. The obtained material has the advantages of low gas content, but the grain is coarse, the cost is high, and the yield is low; (2) powder metallurgy + rolling processing, which is to mix molybdenum, titanium, zirconium, carbon powder and other elements in a certain proportion, and then to obtain TZM products by isostatic pressing, high-temperature sintering, rolling or swaging and annealing. The main characteristics are large investment, and the grain structure has obvious grain orientation; (3) powder metallurgy + hot isostatic pressing technology, which is to obtain TZM products by hot isostatic pressing treatment after powder metallurgy. The equipment investment is large, the process cycle is long, and the grain size of the obtained product is large.

[0005] In recent years, the SPS technology has unique advantages in preparing high-strength, high-density and small-grain-size materials, and the equipment is simple to operate, the production cycle is short, and it is energy-saving and environmentally friendly. Therefore, the method of using powder metallurgy + SPS process to prepare low-oxygen high-strength TZM alloy needs to be explored.

[0006] In addition, if the oxygen content of the TZM is too high, it can lead to the generation and aggregation of internal oxides of the alloy, reducing the strength of the material and affecting the durability of the component. The lower the oxygen content of the TZM, the better the toughness and processability of the alloy, and the higher the recrystallization temperature of the alloy and the lower the oxidation rate of the alloy, and the longer the service life of the target disc or other high-temperature components prepared therefrom. SUMMARY

[0007] TECHNICAL PROBLEM

[0008] In view of the deficiencies of the prior art, the present application provides a method for preparing a low-oxygen high-strength TZM alloy material, which realizes low-oxygen content, high strength, high performance, high efficiency and stable manufacturing of the TZM alloy material.

[0009] After careful research by the inventor of the present application, it was found that the microstructure of the TZM has a significant impact on its performance. Figure 1 shows the scanning electron microscope images of the microstructure of the TZM prepared by the powder metallurgy + rolling processing method. Figure 1(a) is a scanning electron microscope image of the microstructure along the rolling direction, and Figure 1(b) is a scanning electron microscope image of the microstructure perpendicular to the rolling direction. As can be seen from the figures, the microstructure along the rolling direction is a long fibrous structure, and the microstructure perpendicular to the rolling direction is an irregular flake. Therefore, along these two different directions, the performance is different, resulting in anisotropic overall performance.

[0010] In order to improve the performance of the TZM, it is necessary to provide a TZM with a more uniform microstructure.

[0011] TECHNICAL SCHEME

[0012] According to a first aspect of the present application, a low-oxygen high-strength TZM alloy material is provided, which has equiaxed crystal grains, random orientation, consistent performance in all directions, and an average grain size of about 25-35 μm.

[0013] Preferably, the density of the TZM alloy material is 10 g / cm 3 The above.

[0014] Preferably, the tensile strength of the TZM alloy material at room temperature is 380 MPa or more, more preferably 390 MPa or more.

[0015] Preferably, the oxygen content of the TZM alloy material is 50 ppm or less, more preferably 40 ppm or less.

[0016] According to a second aspect of the present application, a method for preparing a low-oxygen high-strength TZM alloy material is provided, which comprises the following steps:

[0017] S1: According to the composition content requirements of the TZM alloy material, the molybdenum powder, titanium hydride powder or titanium-containing powder, zirconium hydride powder or zirconium-containing powder, and carbon powder are put into a V-type mixer or a drum mixer or a planetary ball mill for powder mixing, and the uniformly mixed powder raw material of the TZM alloy material is obtained through detection;

[0018] S2: The uniformly mixed powder is dried, then molded and pressure formed to obtain a blank, and then put into a high vacuum sintering furnace for high temperature sintering, vacuumized to 1*10 -2 ~1*10 -3 Pa, to obtain a sintered blank; wherein the sintering conditions are as follows:

[0019] Temperature of the sintering: 1750-2000℃; holding time: 0.5-5h; cooling mode: cooling to room temperature with the furnace;

[0020] S3: The sintered blank is taken out and put into a corresponding graphite mold, and then put into an SPS furnace cavity and vacuumized for pressure sintering to obtain the TZM alloy material.

[0021] Preferably, in step S1, the titanium-containing powder is titanium hydride powder with a purity of 99.5% or above and a particle size of 1-4μm.

[0022] Preferably, in step S1, the zirconium-containing powder is: zirconium hydride powder with a purity of 99.5% or above and a particle size of 1-3μm; and / or zirconium carbide powder with a purity of 99.5% or above and a particle size of 0.5-2μm.

[0023] Preferably, the purity of the molybdenum powder is 99.95% or above; and the particle size is 6-7μm.

[0024] Preferably, in step S1, the weight content of titanium, zirconium and carbon elements is 0.4%-0.5%, 0.08%-0.1%, 0.03%-0.04% respectively, more preferably 0.5%, 0.1%, 0.035% respectively, with the balance being Mo, relative to the total weight of molybdenum, titanium, zirconium and carbon elements.

[0025] Preferably, in step S2, the powder is loaded into the mold, and a pressure of 30-80MPa is applied to the powder. By applying pressure, a blank with a certain density can be obtained.

[0026] Preferably, in step S2, the high temperature sintering is carried out in a high temperature vacuum furnace or a medium frequency induction sintering furnace.

[0027] Preferably, in step S3, the pre-sintered blank is put into a graphite mold and then into an SPS furnace cavity, vacuumized, and pressure sintered;

[0028] Wherein, the sintering vacuum is less than 10 Pa, the heating is started; the temperature rising rate is 20-60 ℃ / min; the sintering temperature is 1500-1700 ℃; the holding time is 5-60 min; the pressure range is 20-50 MPa; and the cooling mode is furnace cooling to room temperature and then taken out.

[0029] Preferably, the method for preparing the low-oxygen high-strength TZM alloy material comprises the following steps:

[0030] S4: performing mechanical processing on the TZM alloy material obtained in step S3 to obtain a desired shape.

[0031] The low-oxygen high-strength TZM alloy material with the desired shape can be obtained through the mechanical processing.

[0032] Compared with the prior art, the beneficial effects of the present application are embodied in:

[0033] 1. Compared with the prior art, the present application has the advantages of short sintering time, low energy consumption, simple operation / technology and high efficiency in manufacturing the low-oxygen high-strength TZM alloy material by using powder metallurgy+SPS technology, and can greatly reduce the production cycle and cost.

[0034] 2. The TZM alloy material prepared in the present application has low oxygen content and uniformly distributed second phase, the second matrix strengthening is performed in a vacuum environment, the strengthening sintering time is short, the second item precipitation and oxidation of the material are reduced, and high mechanical strength is obtained.

[0035] 3. The TZM alloy material manufactured in the present application has the advantages of high density, strong heat dissipation capacity and good thermal shock resistance.

[0036] 4. The TZM alloy material manufactured in the present application has equiaxed crystal structure, random orientation, uniform and consistent performance in all directions, and does not need subsequent heat treatment process, and has good mechanical processing performance. BRIEF DESCRIPTION OF DRAWINGS

[0037] Fig. 1(a) is a scanning electron microscope image of the TZM alloy material prepared by the rolling method along the rolling method.

[0038] Fig. 1(b) is a scanning electron microscope image of the TZM alloy material prepared by the rolling method along the vertical rolling method.

[0039] Figure 2 Fig. 2 is a scanning electron microscope image of the low-oxygen high-strength TZM alloy material of the TZM alloy material prepared according to embodiment 1. DETAILED DESCRIPTION

[0040] The application will be described in detail below in conjunction with the embodiments. The embodiments are implemented on the premise of the technical solutions of the application, and detailed implementation modes and specific operation processes are given, but the protection scope of the application is not limited to the following embodiments.

[0041] The discharge plasma sintering furnace used in the following embodiments is a 6020 series discharge plasma sintering system produced by Japan Sinter Land Company, the current type is direct current pulse current, and the pulse sequence is 40:7.

[0042] Raw material sources and properties

[0043] Titanium hydride powder, Zhuzhou Runfeng New Material Co., Ltd., purity greater than 99.5%, particle size 1-3 μm.

[0044] Zirconium hydride powder, Zhuzhou Runfeng New Material Co., Ltd., purity greater than 99.5%, particle size 1-2 μm.

[0045] Molybdenum powder, Xi'an Feilian New Material Co., Ltd., purity greater than 99.95%, particle size 6-7 μm.

[0046] Density measurement method: Archimedes drainage method;

[0047] Tensile strength measurement equipment: in-situ tension and compression mechanical testing system;

[0048] Oxygen content test method: pulse heating inert gas melting-infrared absorption method.

[0049] Example 1

[0050] Prepare Φ30*15mm TZM alloy material according to the following steps:

[0051] (1) Put the titanium hydride powder, zirconium hydride powder, carbon powder and high-purity molybdenum powder into a drum mixer according to the weight ratio of 0.5%, 0.1%, 0.035% and the rest, respectively, add grinding balls, and mix uniformly;

[0052] (2) Take out the uniformly mixed powder, dry it in a vacuum drying box, then take it out and load it into a mold, press it to 30 MPa, get a cold-pressed preform, and then put the pressed preform into a high-vacuum sintering furnace cavity, vacuumize to 1*10 -2 Pa, sinter at a rate of 40℃ / min from room temperature, the final sintering temperature is 1950℃, and the temperature is kept for 2h, then take it out after cooling to room temperature, and get a sintered blank.

[0053] (3) Put the sintered blank into a graphite mold, put it into the SPS furnace cavity, vacuumize to below 5 Pa, sinter at a temperature rising rate of 30 ℃ / min from room temperature, the final sintering temperature is 1700 ℃, the pressure is 30 MPa, the holding time is 5 min, take it out after furnace cooling to room temperature, and a dense TZM material is obtained.

[0054] (4) After removing the surface carbon paper and carbonized layer of the sintered blank, mechanical processing is performed to obtain a TZM alloy material with a desired shape.

[0055] Figure 2 A scanning electron microscope image of the microstructure of the TZM alloy material prepared according to Example 1 shows that the grains are equiaxed, the grain size is small, about 30 μm, uniform and consistent, and there are no holes and the like, and the material is dense.

[0056] The TZM alloy material is subjected to anatomical destructive testing, and the prepared TZM alloy material has a density of 10.05 g / cm 3 ; the tensile strength along the axial direction at room temperature is 395 MPa, the tensile strength perpendicular to the axial direction at room temperature is 390 MPa; the oxygen content of the TZM alloy material is 32 ppm; and the average grain size is about 30 μm.

[0057] Example 2

[0058] A Φ30*15 mm TZM alloy material is prepared according to the following steps:

[0059] (1) Put titanium hydride powder, zirconium hydride powder, carbon powder and high-purity molybdenum powder into a drum mixer according to the proportions of 0.5%, 0.1%, 0.035% and the balance, respectively, add grinding balls, and mix uniformly;

[0060] (2) Take out the uniformly mixed powder, dry it in a vacuum drying box, then take it out and load it into a mold, and press to a pressure of 30 MPa to obtain a cold-pressed preform. Put the pressed blank into a high-vacuum sintering furnace cavity, vacuumize to 1*10 -2 Pa, sinter at a rate of 30 ℃ / min from room temperature, the final sintering temperature is 2000 ℃, the holding time is 2 h, take it out after furnace cooling to room temperature, and a sintered blank is obtained.

[0061] (3) Put the sintered blank into a graphite mold, put it into the SPS furnace cavity, vacuumize to below 5 Pa, sinter at a temperature rising rate of 30 ℃ / min from room temperature, the final sintering temperature is 1700 ℃, the pressure is 30 MPa, the holding time is 5 min, take it out after furnace cooling to room temperature, and a dense TZM material is obtained.

[0062] (4) After removing the surface carbon paper and carbonized layer of the sintered blank, mechanical processing is performed to obtain a TZM alloy material with a desired shape.

[0063] The density of the prepared TZM alloy material is 10.08 g / cm 3 ; the room temperature tensile strength along the axial direction is 398 MPa, and the room temperature tensile strength perpendicular to the axial direction is 401 MPa;

[0064] The oxygen content of the TZM alloy material is 22 ppm, and the average grain size is about 33 μm.

[0065] Example 3

[0066] The Φ30*15 mm TZM alloy material is prepared according to the following steps:

[0067] (1) Put the titanium hydride powder, zirconium hydride powder, carbon powder and high-purity molybdenum powder into a drum mixer according to the proportions of 0.5%, 0.1%, 0.035% and the balance respectively, add grinding balls, and stir and mix uniformly;

[0068] (2) Take out the uniformly mixed powder, dry it in a vacuum drying box, then take it out and load it into a mold, and press to 60 MPa to obtain a cold-pressed preform. Put the pressed preform into a high-vacuum sintering furnace cavity, and vacuumize to 1*10 -2 Pa, and sinter at a rate of 50 ℃ / min from room temperature, with a final sintering temperature of 2000 ℃ and a holding time of 2 h. After cooling to room temperature in the furnace, take out the sintered blank.

[0069] (3) Put the sintered blank into a graphite mold and into an SPS furnace cavity, vacuumize to below 5 Pa, and sinter at a rate of 50 ℃ / min from room temperature, with a final sintering temperature of 1700 ℃ and a pressure of 50 MPa, and a holding time of 5 min. After cooling to room temperature in the furnace, take out the dense TZM material.

[0070] (4) After removing the surface carbon paper and carbonized layer of the sintered blank, mechanically process it to obtain a TZM alloy material with the required shape.

[0071] The density of the prepared TZM alloy material is 10.08 g / cm 3 ; the room temperature tensile strength along the axial direction is 398 MPa, and the room temperature tensile strength perpendicular to the axial direction is 401 MPa;

[0072] Comparative Example 1

[0073] The Φ30*15 mm TZM alloy material is prepared according to the following steps:

[0074] (1)Titanium hydride powder, zirconium hydride powder, carbon powder and high-purity molybdenum powder are placed in a drum mixer in proportions of 0.5%, 0.1%, 0.035% and the balance respectively, and grinding balls are added to mix and stir the powders uniformly;

[0075] (2) The mixed and uniform powders are taken out, dried in a vacuum drying box, then taken out and loaded into a graphite mold, and pressed to a pressure of 60 MPa to obtain a cold-pressed preform, which is then placed in an SPS furnace cavity, vacuumed to below 5 Pa, and sintered at a temperature rising rate of 50 ℃ / min from room temperature, with a final sintering temperature of 1700 ℃, a pressure of 50 MPa, and a holding time of 5 min. After cooling to room temperature in the furnace, the dense TZM material is taken out.

[0076] (3) After removing the surface carbon paper and carbonized layer of the sintered blank, mechanical processing is performed to obtain a TZM alloy material with the desired shape.

[0077] The TZM alloy material is subjected to a destructive dissection test, and the density of the prepared TZM alloy material is 10.08 g / cm 3 ; the room temperature tensile strength along the axial direction is 441 MPa, and the room temperature tensile strength perpendicular to the axial direction is 445 MPa; the oxygen content of the TZM alloy material is 500 ppm.

[0078] The following will list the commercially available products and their performance parameters as a comparison.

[0079] Table 1: Commercially available products and their performance

[0080]

[0081] Several commercially available products in the prior art are listed in Table 1, wherein commercially available product 1 is prepared by a rolling process, commercially available product 2 is prepared by a rolling process + annealing treatment at 1600 ℃, and commercially available product 3 is prepared by a hot isostatic pressing process + annealing treatment at 1550 ℃. Compared with the existing processes listed in Table 1, the TZM alloy material prepared according to the present application has a lower oxygen content, the grains are equiaxed, the isotropy is better, and no annealing treatment is required, which simplifies the production process, improves product production efficiency and quality.

Claims

1. A low-oxygen high-strength TZM alloy material, wherein grains of the TZM alloy material are equiaxed crystal structure, random orientation, and isotropic performance, and an average grain size is 25-35 μm, and an oxygen content of the TZM alloy material is 50 ppm or less, and wherein the low-oxygen high-strength TZM alloy material is prepared by a method comprising the following steps: S1: according to a composition content requirement of the TZM alloy material, molybdenum powder, titanium hydride powder or titanium-containing powder, zirconium hydride powder or zirconium-containing powder, and carbon powder are put into a V-type mixer or a drum mixer or a planetary ball mill for powder mixing, and a mixed uniform powder raw material of the TZM alloy material is obtained through detection; a temperature rising rate of the warm sintering is 10-60 ℃ / min, a sintering temperature is 1750-2000 ℃, a holding time is 0.5-5 h, and a cooling mode is furnace cooling to room temperature; S2: the mixed powder is dried, then is loaded into a mold, is subjected to press forming to obtain a blank, and then is placed into a high-vacuum sintering furnace to be subjected to high-temperature sintering, and vacuum is extracted to 1*10 -2 Pa, to obtain a sintered blank; wherein the sintering conditions are as follows: -3 Pa, to obtain a sintered blank; wherein the sintering conditions are as follows: S3: the sintered blank is taken out, put into a corresponding graphite mold, and put into an SPS furnace cavity for vacuum pressure sintering to obtain the TZM alloy material. In step S1, the weight content of titanium, zirconium, and carbon elements is 0.4%-0.5%, 0.08%-0.1%, and 0.03%-0.04% respectively, and the balance is Mo, relative to the total weight of molybdenum, titanium, zirconium, and carbon elements. 2.The low-oxygen high-strength TZM alloy material according to claim 1, wherein 3.The low-oxygen high-strength TZM alloy material according to claim 1, wherein The TZM alloy material has a density of 10 g / cm 3 The above. The room temperature tensile strength of the TZM alloy material is 380 MPa or more. 4.The low-oxygen high-strength TZM alloy material according to claim 1, wherein The room temperature tensile strength of the TZM alloy material is 390 MPa or more. The oxygen content of the TZM alloy material is 40 ppm or less.

5. The low-oxygen, high-strength TZM alloy material of claim 1, wherein, 6.A method for preparing the low-oxygen high-strength TZM alloy material according to any one of claims 1-5, comprising the following steps: S1: according to a composition content requirement of the TZM alloy material, molybdenum powder, titanium hydride powder or titanium-containing powder, zirconium hydride powder or zirconium-containing powder, and carbon powder are put into a V-type mixer or a drum mixer or a planetary ball mill for powder mixing, and a mixed uniform powder raw material of the TZM alloy material is obtained through detection; a temperature rising rate of the warm sintering is 10-60 ℃ / min, a sintering temperature is 1750-2000 ℃, a holding time is 0.5-5 h, and a cooling mode is furnace cooling to room temperature; S2: the mixed powder is dried, then is loaded into a mold, is subjected to press forming to obtain a blank, and then is placed into a high-vacuum sintering furnace to be subjected to high-temperature sintering, and vacuum is extracted to 1*10 -2 ~1*10 -3 Pa to obtain a sintered body; wherein the sintering conditions are as follows: S3: the sintered blank is taken out, put into a corresponding graphite mold, and put into an SPS furnace cavity for vacuum pressure sintering to obtain the TZM alloy material. 7.The method for preparing the low-oxygen high-strength TZM alloy material according to claim 6, wherein In step S1, the titanium-containing powder is titanium hydride powder with a purity of 99.5% or more and a particle size of 1-4 μm, and / or the titanium carbide powder has a purity of 99.5% or more and a particle size of 0.5-1 μm. wherein In step S1, the zirconium-containing powder is zirconium hydride powder with a purity of greater than 99.5% and a particle size of 1-3 μm, and / or the zirconium carbide powder has a purity of 99.5% or more and a particle size of 0.5-2 μm. ​ The purity of the molybdenum powder is above 99.95%, and the particle size is 6-7 μm.

8. The method for preparing a low-oxygen high-strength TZM alloy material according to claim 6 or 7, wherein After the powder in step S2 is loaded into the mold, a pressure of 30-80 MPa is applied to the powder; and / or The high-temperature sintering in step S2 is performed in a high-temperature vacuum furnace or a medium-frequency induction sintering furnace.

9. The method for preparing a low-oxygen high-strength TZM alloy material according to claim 6 or 7, In step S3, the pre-sintered blank is placed into a graphite mold, placed into an SPS furnace cavity, vacuumized, and subjected to pressure sintering; wherein, The sintering vacuum is less than 10 Pa, heating is started, the heating rate is 20-60 ℃ / min, the sintering temperature is 1500-1700 ℃, the holding time is 5-60 min, the pressure range is 20-50 MPa, and the cooling mode is furnace cooling to room temperature for removal.

10. The method for preparing a low-oxygen high-strength TZM alloy material according to claim 6 or 7, further comprising the following step: S4: The TZM block obtained in step S3 is subjected to mechanical processing of the outer shape.

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