CN114277274A - Preparation method of bimodal grain molybdenum alloy - Google Patents

Preparation method of bimodal grain molybdenum alloy Download PDF

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Publication number
CN114277274A
CN114277274A CN202111629505.0A CN202111629505A CN114277274A CN 114277274 A CN114277274 A CN 114277274A CN 202111629505 A CN202111629505 A CN 202111629505A CN 114277274 A CN114277274 A CN 114277274A
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molybdenum alloy
bimodal grain
composite powder
preparation
suspension
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徐流杰
魏世忠
宋万里
李洲
赵云超
王喜然
周玉成
王长记
潘昆明
李秀青
田高龙
朱向炜
谢红申
刘伟
李继文
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Henan University of Science and Technology
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Henan University of Science and Technology
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Abstract

The invention relates to a preparation method of a bimodal grain molybdenum alloy, belonging to the technical field of metal materials. The preparation method of the bimodal grain molybdenum alloy comprises the following steps: Mo/Al2O3Pressing and sintering the composite powder to obtain a sintered body, and forging and annealing the sintered body to obtain the composite powder; the sintering temperature is 1920-1980 ℃; the forging deformation is 60-70%. The preparation method of the molybdenum alloy with the double-peak grains of the invention ensures that the molybdenum alloy generates coarse grains by controlling higher sintering temperature and the molybdenum in the molybdenum alloy is recrystallized to generate fine grains and distributed around the coarse grains by controlling larger deformation amount of forging, the microstructure of the double-peak grains appears in the molybdenum alloy, the plasticity of the molybdenum alloy is improved by using the coarse grains, the tensile strength of the molybdenum alloy is improved by using the fine grains, and the molybdenum alloy is improved simultaneouslyTensile strength and plasticity.

Description

Preparation method of bimodal grain molybdenum alloy
Technical Field
The invention relates to a preparation method of a bimodal grain molybdenum alloy, and particularly belongs to the technical field of metal materials.
Background
Molybdenum and its alloy have the advantages of high hardness, high strength, low thermal expansion coefficient, thermal fatigue resistance and the like, and are widely applied to the fields of aerospace, nuclear industry, electronic industry and the like. However, pure molybdenum is a typical body-centered cubic metal, and the disadvantages of low temperature brittleness and low plasticity still need to be improved. The conventional method for improving the performance of the molybdenum alloy is to change the component structure of the molybdenum alloy, such as work hardening, alloying, second-phase dispersion strengthening and the like, wherein the oxide dispersion strengthening can effectively improve the toughness of the molybdenum alloy. In the research of the oxide-doped molybdenum alloy, besides paying attention to the influence of the type and the content of the oxide on the structure and the performance of the molybdenum alloy, the molybdenum crystal grains need to be refined as much as possible to improve the mechanical property of the molybdenum alloy, but the finer the crystal grain size is, the higher the requirements on the production process are, and the cost problem cannot be ignored.
Disclosure of Invention
The invention aims to provide a preparation method of a low-cost bimodal grain molybdenum alloy.
In order to achieve the purpose, the technical scheme adopted by the invention is as follows:
a preparation method of a bimodal grain molybdenum alloy comprises the following steps:
Mo/Al2O3Pressing and sintering the composite powder to obtain a sintered body, and forging and annealing the sintered body to obtain the composite powder; the sintering temperature is 1920-1980 ℃; the forging deformation is 60-70%.
According to the preparation method of the molybdenum alloy with the double-peak grains, the molybdenum alloy generates the coarse grains by controlling the higher sintering temperature, and the larger deformation amount of forging is controlled, so that molybdenum in the molybdenum alloy is recrystallized to generate the fine grains which are distributed around the coarse grains, the microstructure of the double-peak grains appears in the molybdenum alloy, the plasticity of the molybdenum alloy is improved by using the coarse grains, the tensile strength of the molybdenum alloy is improved by using the fine grains, and the purposes of simultaneously improving the tensile strength and the plasticity of the molybdenum alloy are achieved.
For example, the sintering temperature is 1920 ℃ or 1950 ℃ and the forging deformation amount is 70%.
Further, the heat preservation time for sintering is 3 h.
Further, the Mo/Al2O3The pressing and sintering of the composite powder can be carried out simultaneously or separately: pressing and then sintering.
Further, the Mo/Al2O3When the pressing and sintering of the composite powder are carried out separately, the sintering is pressureless sintering.
Further, the forging is swaging. The sintered body is rod-shaped.
To make Al be2O3More uniform distribution in the molybdenum alloy, said swagedThe temperature is 1100-1200 ℃. For example, the swaging temperature is 1150 ℃.
Further, the swaging is a multi-stage swaging. The multistage rotary swaging can reduce the damage to the blank and has the advantage of energy conservation. The deformation of each stage of rotary swaging is 10-20%. The sintered body was subjected to multi-stage swaging to a swage sample having a diameter of 12.5 mm. Further, the swage pattern is rod-shaped.
To make Al be2O3Has the effect of refining crystal grains and does not generate excessive Al at crystal boundary2O3Particles of the Mo/Al2O3Al in composite powder2O3The volume fraction of (A) is 1.2-2.0%.
Further, the Mo/Al2O3The average particle size of the composite powder is 3-4 μm.
Further, the Mo/Al2O3The preparation method of the composite powder comprises the following steps: 1) adding MoO3Precursor and Al2O3Drying the mixed suspension of the precursor and calcining to obtain MoO3/Al2O3Compounding powder; 2) by hydrogen to MoO3/Al2O3And (4) reducing the composite powder to obtain the composite powder.
Further, the reduction is a two-stage reduction. The temperature of the first-stage reduction is 550-570 ℃. The time for one-stage reduction was 4 h. The temperature of the second-stage reduction is 920-960 ℃. The time of the second reduction is 6 h. For example, the temperature for the first reduction is 560 ℃ and the temperature for the second reduction is 940 ℃.
Further, the preparation method of the mixed suspension comprises the following steps: a) carrying out hydrothermal reaction on tetramolybdate and nitric acid to obtain a first suspension; b) carrying out hydrothermal reaction on aluminum salt and alkali to obtain a second suspension; c) and uniformly mixing the first suspension and the second suspension to obtain the suspension. The temperature of heat preservation in the step a) and the step b) is 160-180 ℃, and the time of heat preservation is 14-16 hours. For example, the temperature for the heat preservation in step a) and step b) is 170 ℃ and the time for the heat preservation is 15 h.
In the step a), the hydrothermal reaction is to carry out heat preservation treatment on tetramolybdate and nitric acid in a closed container. Further, when the first suspension is prepared, the filling degree of the closed container is 85% to 95%. For example, when the first suspension is prepared, the degree of filling of the closed vessel is 90%.
In the step b), the hydrothermal reaction is to perform heat preservation treatment on the mixed aqueous solution of the aluminum salt and the alkali in a closed container. When preparing the second suspension, the filling degree of the closed container is 75-85%. For example, when the second suspension was prepared, the degree of filling of the closed vessel was 80%.
Typically, in said step a), the amount of species of nitric acid is greater than the amount of species of tetramolybdate. Further preferably, the tetramolybdate is ammonium tetramolybdate, the nitric acid has a pH of 0.8, the aluminum salt is aluminum nitrate, and the base is urea.
Further, the calcining temperature of the dried mixed suspension is 480-520 ℃. The calcining time is 3-5 h. For example, the calcination temperature is 500 ℃ and the calcination time is 4 hours.
Further, the pressing is cold isostatic pressing. For Mo/Al2O3And carrying out cold isostatic pressing on the composite powder to obtain a blank, and sintering the blank to obtain a sintered body. The pressure of the cold isostatic pressing is 180-220 MPa. And the pressure maintaining time of the cold isostatic pressing is 20-40 min. For example, the pressure of the cold isostatic pressing is 200MPa, and the dwell time of the cold isostatic pressing is 30 min.
In order to further refine the crystal grains, the annealing temperature is 1040-1060 ℃, and the annealing time is 1-1.5 h. For example, the annealing temperature is 1050 ℃ and the annealing time is 1 h. Further preferably, the annealing is vacuum annealing.
The prepared bimodal grain molybdenum alloy has tensile strength not lower than 628MPa and elongation after fracture not lower than 35.3 percent, and has good application prospect.
Drawings
FIG. 1 shows a bimodal Mo-1.2 vol% Al crystal in example 1 of the present invention2O3SEM tissue map of the alloy;
FIG. 2 shows Mo/Al in example 3 of the present invention2O3SEM texture of the composite powder;
FIG. 3 shows a bimodal Mo-2.0 vol% Al grain in example 3 of the present invention2O3SEM texture of the alloy.
Detailed Description
The present invention will be further described with reference to the following examples.
Example 1
The preparation method of the bimodal grain molybdenum alloy of the embodiment comprises the following steps:
(1) preparing composite powder: 250g of ammonium tetramolybdate are weighed into a 500mL high-pressure reaction kettle, a prepared nitric acid solution with the pH value of 0.8 is added to the high-pressure reaction kettle, the filling degree of the high-pressure reaction kettle is about 90%, and the mixture is stirred uniformly by a glass rod. Weighing 5.08g of aluminum nitrate and 1.22g of urea, putting the mixture into another 100mL high-pressure reaction kettle, adding distilled water until the filling degree is about 80%, and uniformly stirring; and (3) putting the two high-pressure reaction kettles into a drying oven, keeping the temperature at 170 ℃ for 15 hours, taking out the high-pressure reaction kettles, and cooling to room temperature. Mixing and stirring the turbid liquid in the two reaction kettles uniformly, filtering, drying, calcining at 500 ℃ for 4 hours, and cooling along with the furnace; the calcined powder is reduced for two sections to obtain Mo-1.2 vol% Al2O3Composite powder with average grain diameter of 3.95 μm; wherein, the reducing medium of the two-stage reduction is hydrogen, the first-stage reduction temperature is 560 ℃, the reduction time is 4h, the second-stage reduction temperature is 940 ℃, and the reduction time is 6 h;
(2) mo-1.2 vol% Al obtained in step (1)2O3Placing the composite powder into a rubber sleeve with the inner diameter of 30mm, repeatedly vibrating and compacting to ensure that the powder in the rubber sleeve is uniform, sealing the rubber sleeve by using a rubber plug, tightly winding the rubber plug and the rubber sleeve by using an iron wire, placing the treated rubber sleeve into a cold isostatic press, setting the pressure to be 200MPa, and maintaining the pressure for 30min to obtain a green compact;
(3) pressureless sintering is carried out on the pressed blank obtained in the step (2) at the temperature of 1920 ℃, and a sintered body is obtained after heat preservation is carried out for 3 hours;
(4) performing multi-stage rotary swaging on the sintered body obtained in the step (3) at 1150 ℃ to obtain a rod-shaped rotary swaging sample with the diameter of 12.5mm, wherein the total deformation amount of rotary swaging is 70%, and the deformation amount of each stage of rotary swaging is 10-20%;
(5) carrying out vacuum annealing on the rotary swaging sample obtained in the step (4) at 1050 ℃, and preserving heat for 1h to obtain Mo-1.2 vol% Al2O3And (5) alloying to obtain the alloy.
Mo-1.2 vol% Al prepared in this example2O3The microstructure of the alloy is shown in fig. 1, and it can be seen from fig. 1 that fine grains are distributed around coarse grains.
Example 2
This example differs from example 1 only in that: Mo-Al obtained in the production method of this example2O3Al in composite powder2O3Was 1.6% by volume, and the same contents as in example 1 were not mentioned.
Example 3
This example differs from example 1 only in that: Mo-Al obtained in the production method of this example2O3Al in composite powder2O3Was 2.0%, and the same contents as in example 1 were not mentioned.
Mo-2.0 vol% Al after reduction in the present embodiment2O3As shown in FIG. 2, the SEM image of the composite powder is similar to that of a spherical composite powder and is observed from FIG. 2, and the composite powder has a blocking phenomenon, i.e., Mo-2.0 vol% Al2O3The microstructure of the alloy is shown in fig. 3. it can be seen from fig. 3 that fine grains are distributed around coarse grains, which can improve the plasticity of the molybdenum alloy, and fine grains can improve the strength of the molybdenum alloy.
Examples of the experiments
The tensile strength and the elongation after fracture of the bimodal grain molybdenum alloy prepared in the examples 1 to 3 were respectively tested, and the test results are shown in table 1. The test method comprises the following steps: the room temperature tensile test was carried out according to GB/T228.1-2010 part 1 Room temperature test method for tensile testing of metallic materials.
TABLE 1 mechanical properties of bimodal grain molybdenum alloys prepared in examples 1-3
Tensile strength (MPa) Elongation after rupture (%) Product of strength and elongation (MPa%)
Example 1 628 35.3 22168.4
Example 2 631 38.6 24356.6
Example 3 629 40.2 25285.8
As can be seen from table 1, the bimodal grain molybdenum alloy prepared in the embodiments 1 to 3 of the present invention has both higher tensile strength and better ductility, and compared with the prior art, chinese patent with application number CN108145156B discloses a method for preparing a high-performance TZM molybdenum alloy rod, which mainly comprises the processing steps of raw material preparation, material mixing, press forming, sintering, continuous rolling deformation, etc., wherein the tensile strength (MPa) of the molybdenum alloy obtained in the embodiments 8 to 10 of the patent is 820, 912, 925, the elongation (%) after fracture is 17, 20, 23, and the product of strength and elongation (MPa) is 13940, 18240, 21275, respectively. Therefore, compared with the TZM molybdenum alloy disclosed by the patent, the double-peak grain molybdenum alloy disclosed by the invention has the advantages that the plasticity and the product of strength and elongation are greatly improved, and the application range is wider.

Claims (10)

1. The preparation method of the bimodal grain molybdenum alloy is characterized by comprising the following steps of: Mo/Al2O3Pressing and sintering the composite powder to obtain a sintered body, and forging and annealing the sintered body to obtain the composite powder; the sintering temperature is 1920-1980 ℃; the forging deformation is 60-70%.
2. The method of making the bimodal grain molybdenum alloy of claim 1, wherein the forging is swaging; the sintered body is rod-shaped; the temperature of the rotary swaging is 1100-1200 ℃.
3. The method of making the bimodal grain molybdenum alloy of claim 2, wherein said swaging is multi-stage swaging; the deformation of each stage of rotary swaging is 10-20%.
4. The method of claim 1, wherein the Mo/Al is in the form of a bimodal grain molybdenum alloy2O3Al in composite powder2O3The volume fraction of (A) is 1.2-2.0%.
5. The method of claim 1, wherein the Mo/Al is in the form of a bimodal grain molybdenum alloy2O3The preparation method of the composite powder comprises the following steps: 1) adding MoO3Precursor and Al2O3Drying the mixed suspension of the precursor and calcining to obtain MoO3/Al2O3Compounding powder; 2) by hydrogen to MoO3/Al2O3And (4) reducing the composite powder to obtain the composite powder.
6. The method for preparing the bimodal grain molybdenum alloy as claimed in claim 5, wherein the method for preparing the mixed suspension liquid comprises the following steps: a) carrying out hydrothermal reaction on tetramolybdate and nitric acid to obtain a first suspension; b) carrying out hydrothermal reaction on aluminum salt and alkali to obtain a second suspension; c) and uniformly mixing the first suspension and the second suspension to obtain the suspension.
7. The preparation method of the bimodal grain molybdenum alloy as claimed in claim 6, wherein the heat preservation temperature in step a) and step b) is 160-180 ℃, and the heat preservation time is 14-16 h; the tetramolybdate is ammonium tetramolybdate; the aluminum salt is aluminum nitrate, and the alkali is urea.
8. The preparation method of the bimodal grain molybdenum alloy as claimed in claim 5, wherein the calcination temperature is 480-520 ℃ and the calcination time is 3-5 h.
9. The method of making the bimodal grain molybdenum alloy of claim 1, wherein said pressing is cold isostatic pressing; the pressure of the cold isostatic pressing is 180-220 MPa, and the pressure maintaining time of the cold isostatic pressing is 20-40 min.
10. The method for preparing the bimodal grain molybdenum alloy as claimed in claim 1, wherein the annealing temperature is 1040-1060 ℃, and the annealing time is 1-1.5 h.
CN202111629505.0A 2021-12-28 2021-12-28 Preparation method of bimodal grain molybdenum alloy Pending CN114277274A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116287833A (en) * 2023-03-14 2023-06-23 河南科技大学 Preparation method of in-situ authigenic two-dimensional carbide dispersion strengthening and toughening molybdenum alloy

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116287833A (en) * 2023-03-14 2023-06-23 河南科技大学 Preparation method of in-situ authigenic two-dimensional carbide dispersion strengthening and toughening molybdenum alloy

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