CN111206164B - Preparation method of high-performance ultra-fine grain molybdenum-lanthanum alloy - Google Patents
Preparation method of high-performance ultra-fine grain molybdenum-lanthanum alloy Download PDFInfo
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- 238000002360 preparation method Methods 0.000 title claims abstract description 12
- 229910000858 La alloy Inorganic materials 0.000 title claims abstract description 11
- CBPOHXPWQZEPHI-UHFFFAOYSA-N [Mo].[La] Chemical compound [Mo].[La] CBPOHXPWQZEPHI-UHFFFAOYSA-N 0.000 title claims abstract description 11
- 238000005245 sintering Methods 0.000 claims abstract description 52
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum oxide Inorganic materials [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims abstract description 38
- 229910001182 Mo alloy Inorganic materials 0.000 claims abstract description 35
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims abstract description 35
- 238000000034 method Methods 0.000 claims abstract description 25
- 239000002245 particle Substances 0.000 claims abstract description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000011812 mixed powder Substances 0.000 claims abstract description 8
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims description 27
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 22
- 239000001257 hydrogen Substances 0.000 claims description 22
- 229910052739 hydrogen Inorganic materials 0.000 claims description 22
- 238000002156 mixing Methods 0.000 claims description 21
- 239000007789 gas Substances 0.000 claims description 18
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 16
- 239000000843 powder Substances 0.000 claims description 15
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 13
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 12
- 230000001681 protective effect Effects 0.000 claims description 12
- 238000001354 calcination Methods 0.000 claims description 10
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 8
- 229910052786 argon Inorganic materials 0.000 claims description 8
- 239000004202 carbamide Substances 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 238000000227 grinding Methods 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- 229910052760 oxygen Inorganic materials 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- 239000006185 dispersion Substances 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 239000000463 material Substances 0.000 claims description 6
- 238000001914 filtration Methods 0.000 claims description 5
- 238000004321 preservation Methods 0.000 claims description 4
- 239000012300 argon atmosphere Substances 0.000 claims description 2
- 239000008367 deionised water Substances 0.000 claims description 2
- 229910021641 deionized water Inorganic materials 0.000 claims description 2
- 238000011946 reduction process Methods 0.000 claims description 2
- 238000003760 magnetic stirring Methods 0.000 claims 1
- 239000013078 crystal Substances 0.000 abstract description 15
- 230000000694 effects Effects 0.000 abstract description 7
- 238000005728 strengthening Methods 0.000 abstract description 5
- KTUFCUMIWABKDW-UHFFFAOYSA-N oxo(oxolanthaniooxy)lanthanum Chemical compound O=[La]O[La]=O KTUFCUMIWABKDW-UHFFFAOYSA-N 0.000 description 28
- 230000000052 comparative effect Effects 0.000 description 19
- 238000002490 spark plasma sintering Methods 0.000 description 16
- 239000000203 mixture Substances 0.000 description 11
- 238000005303 weighing Methods 0.000 description 7
- 239000000956 alloy Substances 0.000 description 6
- 229910017583 La2O Inorganic materials 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 5
- 229910052750 molybdenum Inorganic materials 0.000 description 5
- 239000011733 molybdenum Substances 0.000 description 5
- 238000010587 phase diagram Methods 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
- 238000007789 sealing Methods 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 238000005452 bending Methods 0.000 description 3
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 3
- 238000005516 engineering process Methods 0.000 description 2
- NZPIUJUFIFZSPW-UHFFFAOYSA-H lanthanum carbonate Chemical compound [La+3].[La+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O NZPIUJUFIFZSPW-UHFFFAOYSA-H 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 229910017569 La2(CO3)3 Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000005260 corrosion Methods 0.000 description 1
- 230000007797 corrosion Effects 0.000 description 1
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 1
- 239000010931 gold Substances 0.000 description 1
- 229910052737 gold Inorganic materials 0.000 description 1
- 239000005457 ice water Substances 0.000 description 1
- 229960001633 lanthanum carbonate Drugs 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000005272 metallurgy Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 238000010079 rubber tapping Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
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Abstract
The invention discloses a preparation method of a high-performance ultra-fine grain molybdenum-lanthanum alloy, which comprises the following steps: 1) spherical nano La2O3Preparing; 2) preparing molybdenum powder; 3) preparing mixed powder; 4) preparing a molybdenum alloy: after the mixed powder is weighted, SPS rapid sintering is carried out to obtain La2O3-Mo molybdenum alloy. The invention adopts a water bath method to prepare La2O3The second phase can achieve the purpose of controlling the size and appearance of the second phase by controlling the time length of the water bath and the cooling speed, thereby obtaining very fine spherical La2O3And the smaller the second phase particles are, the more uniform the second phase particles are, the easier the second phase particles enter the interior of the Mo alloy crystal grains, and the more obvious strengthening effect is achieved. Spherical La in the present invention2O3The strengthening effect is best, the possibility of microcrack generation is low due to the small stress concentration tendency, the fracture strength can be further improved, cracks deviate from the original main expansion direction to form dislocation loops, and therefore the tensile strength of the yield strength is improved.
Description
Technical Field
The invention belongs to the technical field of molybdenum alloy materials, and particularly relates to a preparation method of a high-performance ultrafine-grained molybdenum lanthanum alloy.
Background
Molybdenum alloys are a commonly used high temperature alloy with many excellent properties, including high melting point, high strength, high creep and corrosion resistance, low coefficient of thermal expansion, and excellent thermal and electronic conductivity. The method has wide application in the fields of aerospace, electronic and electric appliances, machining, military, metallurgy and the like. With the rapid development of economy and industry, the molybdenum alloy with high technical content and high performance inevitably occupies an important position in the aspects of future high and new technology weapons, advanced scientific technology and nuclear energy development, which obviously further increases the requirements on the performance of the molybdenum alloy material.
When the molybdenum alloy is prepared, because the molybdenum alloy powder is very sensitive to temperature and can grow up rapidly at high temperature in the sintering process, the grain size of the rare earth oxide doped molybdenum alloy prepared by the traditional method is always larger (usually about 5-17 mu m), and the large-grain alloy can show larger brittleness, not high yield strength, tensile strength and other problems; the second, coarse second phase aggregates at the grain boundaries, which may reduce the bonding forces between grain boundaries, which may further degrade the performance of the molybdenum alloy.
Disclosure of Invention
The invention aims to provide a preparation method of a high-performance ultra-fine grain molybdenum-lanthanum alloy, which can effectively reduce the grain size of the alloy and improve the comprehensive performance of the alloy.
The preparation method of the high-performance ultra-fine grain molybdenum-lanthanum alloy comprises the following steps:
1) preparation of spherical nano La2O 3: dissolving lanthanum nitrate and urea in deionized water, magnetically stirring and uniformly mixing to obtain a mixed dispersion liquid, heating the mixed dispersion liquid for reaction, cooling in an ice bath after the reaction is finished, filtering and washing to obtain white powder, and calcining the white powder to obtain spherical nano La2O 3;
2) preparing molybdenum powder: grinding ammonium paramolybdate, and then placing the ground ammonium paramolybdate in a muffle furnace for two-step hydrogen reduction to obtain molybdenum powder;
3) preparing mixed powder: putting the spherical nano La2O3 obtained in the step 1) and the molybdenum powder obtained in the step 2) into a mixer for mixing to obtain mixed powder;
4) preparing a molybdenum alloy: after the mixed powder in the step 3) is weighted, SPS rapid sintering is carried out under the set mechanical pressure and argon atmosphere, and the La2O3-Mo molybdenum alloy is obtained.
In the step 1), the granularity of lanthanum nitrate powder is 0.8-1.2 mu m, the mass ratio of lanthanum nitrate to urea is (0.2-0.5) - (16-20), and the concentration of lanthanum nitrate in the mixed dispersion liquid is 0.5-2.5 mg/mL; the heating is water bath heating, the heating reaction temperature is 80-90 ℃, and the heating time is 0.5-1.5 h; the calcination is carried out in a tubular furnace, the calcination temperature is 900-1000 ℃, the heating rate is 9-11 ℃/min, and the calcination time is 1.5-2.5 h. In the step, water bath reaction and ice water bath cooling ensure that the prepared lanthanum carbonate powder is fine enough and can achieve the purpose of shape control; and calcining at high temperature in a tubular furnace to fully decompose the lanthanum carbonate to obtain the lanthanum oxide.
In the step 1), the prepared La2O3 has a spherical-like microstructure and an average size of 70-95 nm.
In the step 2), the particle size of the grinded ammonium paramolybdate is 0.5-1.1 μm; the first-step hydrogen reduction temperature is 500-600 ℃, the second-step hydrogen reduction temperature is 850-950 ℃, and the first-step hydrogen reduction time is 0.8-1.2 h; the time of the second hydrogen reduction step is 0.8-1.2 h; in the reduction process, the hydrogen flow is 0.5-0.7L/min; the average particle size of the molybdenum powder is 400-600 nm, and the content of oxygen in the molybdenum powder is less than 0.04%. In the step, the full grinding and the two-stage hydrogen reduction before the reduction of the ammonium paramolybdate are performed to ensure that purer and fine molybdenum powder particles are obtained, and the oxygen content in the molybdenum powder is reduced by controlling the hydrogen flow and the tapping temperature, so that the purity of a molybdenum alloy crystal boundary in the subsequent sintering process is improved, and the performance of the molybdenum alloy is further improved.
In the step 3), the mass ratio of the La2O3 to the molybdenum powder is (0.5-1.5) to (98.5-99.5); before mixing, argon is required to be introduced into a mixing bottle of the mixer as protective gas, the ball-material ratio is (1.5-2.0): 1 during mixing, forward and reverse directions are alternately mixed at 70-90 r/min, and the mixing time is 13-15 h. In the step, the mixing process enables the La2O3 powder to be uniformly dispersed and adhered to the surface of molybdenum powder particles, so that a second phase can more easily enter the interior of molybdenum alloy grains in the subsequent sintering process, and optimal conditions are provided for preventing the grains from growing.
In the step 4), the SPS sintering furnace is closed and vacuumized until the vacuum degree is less than 1.0 multiplied by 10 < -1 > Pa before sintering, and then protective gas argon is introduced; the set mechanical pressure is 30-50 MPa, the sintering temperature is 1500-1600 ℃, and 1600 ℃ is preferred; the temperature rising and reducing rate is 90-110 ℃/min, and the heat preservation time is 4-6 min. In the sintering process, the smaller vacuum degree can avoid the increase of oxygen content, the larger mechanical pressure and the lower sintering temperature, and the higher sintering density and the finer grain size can be ensured, so that the performance of the molybdenum alloy can be improved to a great extent.
La2O3-Mo molybdenum alloy is prepared according to the method.
The principle of the invention is as follows: according to the invention, fine nano-scale spherical La2O3 is prepared by a water bath method, more fine spherical La2O3 can more effectively prevent grain boundary migration and refine grains in the sintering process, fine spherical La2O3 can more easily enter molybdenum alloy crystals, so that the grain boundaries are purified, dislocation movement is more effectively hindered, an effective pinning effect is achieved, the stress concentration tendency of spherical La2O3 in the dislocation action is smaller, and the possibility of generating microcracks is smaller; and secondly, the sintering efficiency of the spark plasma sintering is higher, the sintering temperature can be efficiently reduced, the temperature rise and the temperature reduction are fast, the sintering time is shorter, the growth of crystal grains in the sintering process can be effectively avoided, and the crystal grains are further refined.
The invention has the beneficial effects that:
1) the La2O3 second phase is prepared by adopting a water bath method, the purpose of controlling the size and appearance of the second phase can be achieved by controlling the time length of water bath and the cooling speed, so that the fine spherical La2O3 is obtained, the smaller the second phase particles are, the more uniform the second phase particles are, the more easily the second phase particles enter the interior of the Mo alloy crystal particles, and the more obvious strengthening effect is achieved.
2) Compared with the traditional second-phase rare earth oxide, the second-phase rare earth oxide has the best strengthening effect of the spherical La2O3, the possibility of microcrack generation is low due to the small stress concentration tendency, the fracture strength can be further improved, and the cracks deviate from the original main expansion direction to form dislocation loops, so that the tensile strength of the yield strength is improved.
3) The method controls the size and the shape of the La2O3, simultaneously uses the rapid SPS sintering, can improve the sintering efficiency, and effectively reduces the sintering temperature and the sintering time, thereby reducing the growth time of crystal grains and further refining the crystal grains.
4) The tensile strength, the compressive strength, the bending strength and the compressive strength of the La2O3-Mo molybdenum alloy prepared by the method are respectively improved by more than 16 percent, more than 11 percent and more than 11 percent at room temperature, and the grain size is reduced to about 3.7 mu m from about 10.2 mu m.
Drawings
FIG. 1 scanning electron micrograph of spherical lanthanum oxide prepared in example 1;
FIG. 2 gold phase diagrams of La2O3-Mo molybdenum alloys prepared in example 1 (a), example 2(b) and comparative example 1 (c);
FIG. 3 is a crystal phase diagram of a pure molybdenum phase prepared in comparative example 2;
FIG. 4 is a crystal phase diagram of a pure molybdenum phase prepared in comparative example 3;
FIG. 5 is a crystal phase diagram of La2O3-Mo molybdenum alloy prepared by comparative example 4;
FIG. 6 is a crystal phase diagram of La2O3-Mo molybdenum alloy prepared in comparative example 5.
Detailed Description
Example 1
Weighing 0.325g of lanthanum nitrate and 18g of urea with the particle size of 0.8-1.2 mu m, dissolving in 150mL of water, uniformly stirring by magnetic force, keeping the temperature for 1h at the water bath temperature of 85 ℃, and filtering and washing to obtain white powder. Putting the white powder into a tube furnace, heating to 950 ℃ at the temperature of 10 ℃/min for calcining, keeping the temperature for 2h, and taking out a sample to obtain the spherical La2O3, wherein the microscopic morphology of the spherical La2O3 in the embodiment is shown in figure 1, and the figure shows that the spherical La2O3 is regular spheres, and the average particle size is 85 nm.
Grinding industrial ammonium paramolybdate to the average particle size of 0.8 mu m, then placing the ground industrial ammonium paramolybdate into a muffle furnace, heating the mixture to 550 ℃ in a hydrogen atmosphere, and carrying out first-step reduction for 1 h; after the first-step reduction is finished, heating to 900 ℃ for carrying out second-step reduction, wherein the reduction time is 1 h; after the reaction is finished, molybdenum powder with the thickness of about 500nm is obtained, and the oxygen content is measured to be lower than 0.04%.
Weighing 1% of spherical nano La2O3 and 99% of secondary reduction molybdenum powder according to the weight proportion, introducing argon gas serving as protective gas into a mixing bottle in a mixer, adding nano La2O3 and molybdenum powder according to the ball-to-material ratio of 1.8:1, and mixing at the forward and reverse alternate rotating speed of 80r/min for 14 hours to obtain a mixture.
And putting the mixture into an SPS sintering furnace, sealing the SPS sintering furnace before sintering, vacuumizing until the vacuum degree is less than 1.0 x 10 < -1 > Pa, introducing protective gas Ar, setting the mechanical pressure to be 40MPa, heating to 1600 ℃ at the temperature-reducing rate of 100 ℃/min, and preserving heat for 5min to obtain the La2O 3-Mo-molybdenum alloy.
Example 2
The process parameters in all the preparation processes are essentially identical to those of example 1, and the temperature for SPS sintering alone is 1500 ℃.
Comparative example 1
The process parameters in all the preparation processes are substantially identical to those of example 1, and the temperature of SPS sintering is 1700 ℃ only.
The metallographic photographs of the La2O3-Mo molybdenum alloys prepared in examples 1 and 2 and comparative example 1 are shown in FIG. 2, and the performance parameters are shown in Table 1. From fig. 2 and table 1, it can be seen that the grain size is below 4 μm at 1500-1600 ℃, the grain size increases significantly when the sintering temperature is raised to 1700 ℃, and the La2O3-Mo molybdenum alloy sintered at 1600 ℃ has better texture and mechanical properties, so 1600 ℃ is determined to be the optimal sintering temperature.
TABLE 1 La at different sintering temperatures2O3Comparison of-Mo molybdenum alloy Properties
Comparative example 2
The molybdenum powder prepared in example 1 was directly sintered according to the sintering process of SPS in example 1 to obtain a pure molybdenum phase, and a metallographic structure picture thereof is shown in fig. 3, and specific parameters thereof are shown in table 2.
As shown in Table 2, in comparison between example 1 and comparative example 2, the La2O3-Mo in example 1 has yield strength increased by about 59.1%, tensile strength increased by about 60.7%, bending strength increased by about 161.4%, and compressive strength increased by about 93.5% compared with SPS sintered pure molybdenum.
Comparative example 3
The molybdenum powder prepared in example 1 was subjected to hydrogen sintering in a tube furnace at 1600 ℃. Repeatedly washing gas before sintering to ensure hydrogen sintering atmosphere, wherein the temperature rising and reducing rate is 10 ℃/min, the heat preservation time is 3h, and pure molybdenum phase is obtained, the specific performance parameters are shown in table 2, and the metallographic structure picture is shown in fig. 4.
Compared with comparative example 3, the yield strength of La2O3-Mo in example 1 is improved by about 80.1%, the tensile strength is improved by about 81.2%, the bending strength is improved by about 190.9%, and the compressive strength is improved by about 114.4%.
Comparative example 4
Comparative example 4 is completely consistent with the first 3 steps of example 1, hydrogen sintering is adopted in the fourth step, the specific sintering process is 1600 ℃ tubular furnace hydrogen sintering, gas washing is carried out repeatedly before sintering, the hydrogen sintering atmosphere is guaranteed, the heating and cooling rate is 10 ℃/min, the heat preservation time is 3h, La2O3-Mo is finally obtained, the metallographic structure picture is shown in figure 5, and the specific performance parameters are shown in Table 2.
Example 1 compared with comparative example 4, the La2O3-Mo prepared in example 1 has a grain size significantly lower than that of comparative example 4, and also has hardness and various strengths significantly better than those of comparative example 4.
Comparative example 5
Weighing 1% of common La2O3 and 99% of secondary reduction molybdenum powder (prepared by the method in example 1) according to the weight proportion, introducing argon gas serving as protective gas into a mixing bottle in a mixer, adding the common La2O3 and the molybdenum powder according to the ball-to-material ratio of 1.8:1, and mixing at the forward and reverse alternate rotating speed of 80r/min for 14 hours to obtain a mixture.
And putting the mixture into an SPS sintering furnace, sealing the SPS sintering furnace before sintering, vacuumizing until the vacuum degree is less than 1.0 x 10 < -1 > Pa, introducing protective gas Ar, setting the mechanical pressure to be 40MPa, heating to 1600 ℃ at the temperature-reducing rate of 100 ℃/min, and preserving heat for 5min to obtain the La2O 3-Mo-molybdenum alloy.
The metallographic structure picture shows specific performance parameters shown in fig. 6 and is shown in table 2.
Compared with the comparative example 5, in the example 1, the La2O3-Mo common La2O3 prepared in the comparative example 5 is difficult to enter crystal, is easier to aggregate at crystal boundaries, has poor effect of purifying the crystal boundaries and has general strengthening effect.
TABLE 2 comparison of properties of various La2O3-Mo molybdenum alloys
Example 3
Weighing 0.2g of lanthanum nitrate with the particle size of 0.8-1.2 mu m and 16g of urea, dissolving in 400mL of water, uniformly stirring by magnetic force, keeping the temperature of water bath at 80 ℃ for 1.5h, filtering and washing to obtain white powder. And (3) putting the white powder into a tube furnace, heating to 900 ℃ at the speed of 11 ℃/min for calcining, keeping the temperature for 1.5h, taking out a sample, namely the spherical La2O3, and measuring the average particle size of the spherical La2O3 to be 70 nm.
Grinding industrial ammonium paramolybdate to the average particle size of 0.8 mu m, then placing the ground industrial ammonium paramolybdate into a muffle furnace, heating the mixture to 500 ℃ in a hydrogen atmosphere, and carrying out first-step reduction for 1.2 h; after the first-step reduction is finished, heating to 850 ℃ for second-step reduction, wherein the reduction time is 1.2 h; after the reaction is finished, molybdenum powder with about 560nm is obtained, and the oxygen content is measured to be lower than 0.04%.
Weighing 0.5% of spherical nano La2O3 and 99.5% of secondary reduction molybdenum powder according to the weight proportion, introducing argon gas serving as protective gas into a mixing bottle in a mixer, adding nano La2O3 and molybdenum powder according to the ball-to-material ratio of 1.5:1, and mixing for 13 hours at the forward and reverse alternate rotating speed of 70r/min to obtain a mixture.
And putting the mixture into an SPS sintering furnace, sealing the SPS sintering furnace before sintering, vacuumizing until the vacuum degree is less than 1.0 x 10 < -1 > Pa, introducing protective gas Ar, setting the mechanical pressure to be 30MPa, heating to 1600 ℃ at the temperature-reducing rate of 90 ℃/min, and preserving heat for 4min to obtain the La2O 3-Mo-molybdenum alloy.
Example 4
Weighing 0.5g of lanthanum nitrate and 20g of urea with the particle size of 0.8-1.2 mu m, dissolving the lanthanum nitrate and the urea in 200mL of water, uniformly stirring by magnetic force, keeping the temperature of a water bath at 90 ℃ for 1.0h, filtering and washing to obtain white powder. And (3) putting the white powder into a tube furnace, heating to 900 ℃ at the speed of 9 ℃/min, calcining, keeping the temperature for 2.5 hours, taking out a sample, namely the spherical La2O3, and measuring the average particle size of the spherical La2O3 to be 95 nm.
Grinding industrial ammonium paramolybdate to the average particle size of 1.1 mu m, then placing the ground industrial ammonium paramolybdate into a muffle furnace, heating the mixture to 600 ℃ in a hydrogen atmosphere, and carrying out first-step reduction for 0.8 h; after the first-step reduction is finished, heating to 950 ℃ for second-step reduction, wherein the reduction time is 0.8 h; after the reaction is finished, molybdenum powder with about 560nm is obtained, and the oxygen content is measured to be lower than 0.04%.
Weighing 1.5% of spherical nano La2O3 and 98.5% of secondary reduction molybdenum powder according to the weight ratio, introducing argon gas serving as protective gas into a mixing bottle in a mixer, adding nano La2O3 and molybdenum powder according to the ball-to-material ratio of 2.0:1, and mixing at the forward and reverse alternate rotation speed of 90r/min for 15 hours to obtain a mixture.
And putting the mixture into an SPS sintering furnace, sealing the SPS sintering furnace before sintering, vacuumizing until the vacuum degree is less than 1.0 x 10 < -1 > Pa, introducing protective gas Ar, setting the mechanical pressure to be 30MPa, heating to 1600 ℃ at the temperature-reducing rate of 110 ℃/min, and preserving heat for 6min to obtain the La2O3-Mo molybdenum alloy.
Claims (7)
1. A preparation method of high-performance ultra-fine grain molybdenum lanthanum alloy comprises the following steps:
1) spherical nano La2O3The preparation of (1): dissolving lanthanum nitrate and urea in deionized water, uniformly mixing by magnetic stirring to obtain a mixed dispersion liquid, heating the mixed dispersion liquid for reaction, cooling in an ice bath after the reaction is finished, filtering and washing to obtain white powder, and calcining the white powder to obtain the spherical nano La powder2O3；
2) Preparing molybdenum powder: grinding ammonium paramolybdate, and then placing the ground ammonium paramolybdate in a muffle furnace for two-step hydrogen reduction to obtain molybdenum powder;
3) preparing mixed powder: will be described in detail1) In the spherical nano La2O3Putting the molybdenum powder obtained in the step 2) into a mixer for mixing to obtain mixed powder;
4) preparing a molybdenum alloy: after the mixed powder in the step 3) is weighted, SPS rapid sintering is carried out under the set mechanical pressure and argon atmosphere, and La is obtained2O3-Mo molybdenum alloy;
in step 3), La2O3The mass ratio of the molybdenum powder to the molybdenum powder is (0.5-1.5) to (98.5-99.5); before mixing, argon is required to be introduced into a mixing bottle of the mixer as protective gas, the ball-to-material ratio is (1.5-2.0): 1 during mixing, forward and reverse directions are alternately mixed at 70-90 r/min, and the mixing time is 13-15 h;
in step 4), the SPS sintering furnace is sealed and vacuumized until the vacuum degree is less than 1.0 multiplied by 10-1Pa, then introducing protective gas argon; the set mechanical pressure is 30-50 MPa, the sintering temperature is 1500-1600 ℃, the heating and cooling rate is 90-110 ℃/min, and the heat preservation time is 4-6 min.
2. The method for preparing the high-performance ultra-fine grain molybdenum lanthanum alloy according to claim 1, wherein in the step 1), the grain size of the lanthanum nitrate powder is 0.8-1.2 μm, the mass ratio of lanthanum nitrate to urea is (0.2-0.5): 16-20, and the concentration of lanthanum nitrate in the mixed dispersion liquid is 0.5-2.5 mg/mL; the heating is water bath heating, the heating reaction temperature is 80-90 ℃, and the heating time is 0.5-1.5 h; the calcination is carried out in a tubular furnace, the sintering temperature is 900-1000 ℃, the heating rate is 9-11 ℃/min, and the sintering time is 1.5-2.5 h.
3. The method for preparing high performance ultra-fine grain molybdenum lanthanum alloy of claim 2, wherein in the step 1), La is prepared2O3The microstructure of (A) is spheroidal, and the average size is 70-95 nm.
4. The method for preparing the high-performance ultra-fine grain molybdenum lanthanum alloy according to claim 1, wherein in the step 2), after grinding, the particle size of ammonium paramolybdate is 0.5-1.1 μm; the first-step hydrogen reduction temperature is 500-600 ℃, the second-step hydrogen reduction temperature is 850-950 ℃, and the first-step hydrogen reduction time is 0.8-1.2 h; the time of the first step hydrogen reduction is 0.8-1.2 h; in the reduction process, the hydrogen flow is 0.5-0.7L/min.
5. The method for preparing the high-performance ultra-fine grain molybdenum-lanthanum alloy according to claim 4, wherein the molybdenum powder has an average particle size of 400-600 nm, and the content of oxygen in the molybdenum powder is less than 0.04%.
6. The method of claim 1, wherein the sintering temperature is 1600 ℃.
7. La prepared by the preparation method according to any one of claims 1 to 62O3-Mo molybdenum alloy.
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