Method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using liquid-liquid doping process

Abstract

This invention discloses a method for synthesizing oxide-dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process, comprising the following steps: S1: Preparation of a molybdenum-rhenium mixed solution; S2: Preparation of the doped molybdenum-rhenium mixed solution: dissolving the oxide precursor nitrate in water and then adding it to the molybdenum-rhenium mixed solution; S3: Heat treatment: mechanically stirring the doped molybdenum-rhenium mixed solution, then evaporating the water by heating to obtain a crystalline product, followed by filtering, drying, and sieving the crystalline product to obtain a composite powder; S4: Calcination and thermal decomposition: calcining the composite powder to obtain a pyrolytic powder; S5: Thermal reduction: introducing hydrogen gas into a muffle furnace to reduce the pyrolytic powder to oxide-doped molybdenum-rhenium alloy powder; S6: Rod preparation: obtaining rods through cold isostatic pressing, high-temperature hydrogen sintering, forging, and rotary forging. In this invention, the oxide is stably dispersed in the molybdenum-rhenium alloy in a nanoscale form, which can significantly improve the alloy's performance at high temperatures.

Description

Technical Field

[0001] This invention relates to the field of alloy technology, and in particular to a method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process. Background Technology

[0002] Pure molybdenum (Mo) and its alloys possess excellent high-temperature mechanical properties, creep resistance, strong corrosion resistance, and excellent electrical and thermal conductivity, making them widely used in key engineering fields such as aerospace (turbines), radar communication (traveling wave tubes), equipment manufacturing (heating elements), and the nuclear industry (fuel cladding). However, the intrinsic brittleness and recrystallization-induced brittleness of molybdenum and its alloys, resulting in poor room-temperature plasticity, low room-temperature strength, and low recrystallization temperature, significantly hinder their widespread application as structural materials under extreme conditions. When rhenium (Re) is added to molybdenum, it can suppress molybdenum's recrystallization brittleness, effectively improve Mo's low-temperature brittleness, increase Mo's recrystallization temperature, and simultaneously improve its strength. This phenomenon of Re comprehensively improving Mo's properties is known as the "Re effect." The excellent properties of molybdenum-rhenium alloys have led to their widespread application in medical equipment, defense industries, and other fields. They also exhibit good compatibility with commonly used nuclear fuels at high temperatures and have been identified as candidates for structural materials in space fission reactors. However, the insufficient strength of Mo-Re alloys at high temperatures limits their application in extreme high-temperature environments.

[0003] Numerous studies have shown that the introduction of second-phase particles (such as oxides like ZrO2) can improve the mechanical properties of Mo and its alloys. ZrO2 has a high melting point of 2715℃, stable chemical properties, and high-temperature resistance, ensuring that the oxides do not melt and form large, bulky particles during high-temperature sintering of molybdenum. ZrO2 can hinder dislocation slip, suppress grain boundary growth, effectively refine Mo grains, and inhibit the growth of second-phase particles, thereby improving the strength and ductility of the material and lowering the ductile-brittle transition temperature. The finer and more uniformly dispersed the ZrO2 particles, the stronger the pinning effect on dislocations, and the higher the strength of the alloy.

[0004] Traditional molybdenum alloy doping methods include solid-solid doping and solid-liquid doping. While these methods are simple to operate, it is difficult to effectively control the uniform distribution of second-phase particles in the alloy during preparation, and the size of the second-phase particles is usually large. Therefore, there is an urgent need for a method that can achieve a uniform distribution of second-phase particles in molybdenum-rhenium alloys, thereby further improving the strength of molybdenum-rhenium alloys at high temperatures. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing oxide-dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process. This addresses the problem that solid-solid and solid-liquid doping methods often struggle to effectively control the uniform distribution of second-phase particles within the alloy, leading to lower strength at high temperatures. This invention reveals that liquid-liquid doping offers significant advantages over solid-solid and solid-liquid doping. Liquid-liquid doping achieves a more uniform and finer distribution of second-phase particles at the molecular level, avoiding the problems of uneven particle distribution and excessively large particles found in solid-solid and solid-liquid doping methods. Through liquid-liquid doping, the second-phase particles of this invention can be refined and uniformly distributed within the molybdenum matrix, thereby improving the material's mechanical and high-temperature properties.

[0006] To achieve the above objectives, the present invention provides a method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process, comprising the following steps:

[0007] S1: Preparation of molybdenum-rhenium mixed solution

[0008] Molybdenum salt and rhenium salt are mixed in water, and the pH is adjusted to alkaline using ammonia water to obtain a molybdenum-rhenium mixed solution;

[0009] S2: Preparation of molybdenum-rhenium doped mixed solution

[0010] The precursor nitrate of the oxide is dissolved in water and then added to a molybdenum-rhenium mixed solution to form a molybdenum-rhenium doped mixed solution;

[0011] S3: Heat treatment

[0012] The molybdenum-rhenium mixed solution was mechanically stirred, and then the water was evaporated by heating to obtain a crystallized product. The crystallized product was then filtered, dried and sieved to obtain a composite powder.

[0013] S4: Calcination thermal decomposition

[0014] The composite powder was calcined in a muffle furnace to obtain pyrolytic powder;

[0015] S5: Thermal reduction

[0016] Hydrogen gas is introduced into the muffle furnace to reduce the pyrolysis powder into molybdenum-rhenium alloy powder doped with oxides.

[0017] S6: Bar Preparation

[0018] Molybdenum-rhenium alloy powder doped with oxides was processed by cold isostatic pressing, high-temperature hydrogen sintering, forging and rotary forging to obtain molybdenum-rhenium alloy rods doped with oxides.

[0019] Preferably, in step S1, the proportion of rhenium in the rhenium salt to the total mass of molybdenum in the molybdenum salt and rhenium in the rhenium salt does not exceed 51 wt%.

[0020] Preferably, in step S1, ammonia is added to adjust the pH value to 9-10.

[0021] Preferably, in step S2, the oxide is zirconium oxide.

[0022] Preferably, in step S2, the proportion of oxides to the total mass of molybdenum in molybdenum salt and rhenium in rhenium salt is 0.1~2.0 wt%.

[0023] Preferably, step S2 further includes a heating step during the formation of the molybdenum-rhenium mixed solution, with the heating temperature being 75~85°C, to fully dissolve the mixed solution.

[0024] Preferably, in step S3, the heating and evaporation temperature is 95~105℃; the filtration is performed more than twice; the drying temperature is 80~100℃ and the drying time is 1~2h; and the sieving is performed by passing the material through a 60-mesh sieve and a 40-mesh sieve in sequence.

[0025] Preferably, in step S4, the calcination temperature is 500~600℃, the holding time is 1~5h, the heating rate is 8~12℃ / min, the molybdenum salt is converted into molybdenum trioxide, the rhenium salt is decomposed into rhenium low oxides, and the precursor of the oxides, nitrate, is decomposed into the corresponding oxides.

[0026] Preferably, in step S5, the thermal reduction includes two stages: in the first stage, molybdenum trioxide is reduced to molybdenum dioxide, and in the second stage, molybdenum dioxide is completely reduced to metallic molybdenum, while the low oxide of rhenium is reduced to metallic rhenium.

[0027] Preferably, in step S5, in the first stage, the heating rate is 8~12℃ / min, the reduction temperature is 500~600℃, the holding time is 0.5~1 hour, and the hydrogen flow rate is 80~120ml / s; in the second stage, the heating rate is 3~6℃ / min, the reduction temperature is 1000~1100℃, the holding time is 4~6 hours, and the hydrogen flow rate is 80~120ml / s.

[0028] In step S6, the pressure of cold isostatic pressing is 150MPa~250MPa; the high-temperature hydrogen sintering temperature is 2000℃~3000℃; the forging temperature is 1200℃~1500℃; the rotary forging temperature is 800℃~1200℃, and the deformation is >80%.

[0029] Therefore, the method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using the above-described liquid-liquid doping process has the following beneficial effects:

[0030] (1) The present invention uses molybdenum salt, rhenium salt and nitrate that form oxides as raw materials, and through liquid-liquid doping method, combined with heating crystallization, high temperature conversion and two-stage reduction method, successfully prepared oxide-doped molybdenum-rhenium alloy powder. The oxides are fine and can be uniformly distributed in the alloy powder.

[0031] (2) The oxide-doped molybdenum-rhenium alloy prepared by the present invention has high strength at high temperature, providing a more effective solution for the application of molybdenum-rhenium alloy in the fields of high temperature, radiation resistance and high strength.

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0033] Figure 1 This is a flowchart of the preparation process of the present invention;

[0034] Figure 2 Tensile comparison of the alloy prepared for the example with other comparative alloys at 1100°C;

[0035] Figure 3 Tensile comparison of the alloy prepared for the example with other comparative alloys at 1300°C. Detailed Implementation

[0036] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0037] Example 1

[0038] A method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process includes the following steps:

[0039] S1: Preparation of molybdenum-rhenium mixed solution

[0040] Ammonium molybdate ((NH4)6Mo7O) was weighed according to a Mo:Re mass ratio of 86:14. 24 Molybdenum salt (·4H2O) and ammonia perrhenate (NH4ReO4) are dissolved separately in deionized water. The amount of deionized water added is sufficient to dissolve the molybdenum salt and the rhenium salt, and no special limit is required. The solution is heated to 80°C to fully dissolve them, resulting in ammonium molybdate solution and ammonia perrhenate solution. Ammonia water is added to the ammonium molybdate solution to adjust the pH to 9-10 to ensure that the soluble precursors of ammonium molybdate and ammonium perrhenate exist in ionic form in the solution. Then the ammonium molybdate solution and the ammonia perrhenate solution are mixed to obtain a molybdenum-rhenium mixed solution.

[0041] S2: Preparation of molybdenum-rhenium doped mixed solution

[0042] Weigh out 0.5 wt.% ZrO2 as the precursor of the oxide, zirconium nitrate (Zr(NO3)4·5H2O), and dissolve it in deionized water. The amount of deionized water added is sufficient to dissolve the zirconium salt; no special limit is required. Heat to 80°C to ensure complete dissolution, and then add it to a molybdenum-rhenium mixed solution to form a doped molybdenum-rhenium mixed solution. Here, 0.5 wt.% ZrO2 refers to the total mass of molybdenum in the molybdenum salt and rhenium in the rhenium salt.

[0043] S3: Heat treatment

[0044] The molybdenum-rhenium mixed solution was mechanically stirred to ensure thorough mixing, and then heated at 100°C to evaporate the water. When a small amount of liquid remained, a crystalline product was obtained. The crystalline product was then filtered, followed by a second filtration. The filtered crystalline product was dried at 80°C for 1 hour. After drying, the powder was collected and sieved through 60-mesh and 40-mesh sieves to ensure uniform and fine particle size, finally obtaining a composite powder.

[0045] S4: Calcination thermal decomposition

[0046] The composite powder was placed in a muffle furnace for calcination at a heating rate of 10℃ / min, heated to 550℃ and held for 3 hours, and then cooled with the furnace to obtain pyrolytic powder. At this time, ammonium molybdate ((NH4)2Mo2O7) was converted into molybdenum trioxide (MoO3), ammonium perrhenate was decomposed into low oxides of rhenium, and the zirconium oxide precursor was decomposed into zirconium oxide.

[0047] S5: Thermal reduction

[0048] Hydrogen gas is introduced into the muffle furnace to reduce the pyrolysis powder into molybdenum-rhenium alloy powder doped with oxides. Specifically, a two-stage reduction reaction is carried out by introducing a hydrogen atmosphere.

[0049] First stage: The heating rate is 10℃ / min, the holding temperature is 550℃, the holding time is 1 hour, and the hydrogen flow rate is 100ml / s. At this time, the hydrogen reduces molybdenum trioxide (MoO3) to molybdenum dioxide (MoO2).

[0050] The second stage involved a heating rate of 5℃ / min, a holding temperature of 1050℃ for 5 hours, and a hydrogen flow rate of 100 ml / s. During this stage, molybdenum dioxide (MoO2) was completely reduced to metallic molybdenum (Mo), and simultaneously, the lower oxides of rhenium were reduced to metallic rhenium (Re), yielding a zirconium-doped molybdenum-rhenium alloy powder. The molybdenum-rhenium alloy powder had the following composition: Mo-14wt.%Re-0.5wt.%ZrO2.

[0051] S6: Bar Preparation

[0052] Molybdenum-rhenium alloy powder doped with zirconium oxide was processed by cold isostatic pressing, high-temperature hydrogen sintering, forging and rotary forging to obtain Mo-14wt.%Re-0.5wt.%ZrO2 rods.

[0053] The pressure of cold isostatic pressing is 200 MPa; the high-temperature hydrogen sintering temperature is 2500℃; the forging temperature is 1350℃; the rotary forging temperature is 1100℃, and the deformation is >80%.

[0054] Example 2

[0055] A method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process includes the following steps:

[0056] S1: Preparation of molybdenum-rhenium mixed solution

[0057] Ammonium molybdate ((NH4)6Mo7O) was weighed according to a Mo:Re mass ratio of 86:14. 24 Ammonium perrhenate (NH4ReO4) and ammonium molybdate (NH4ReO4) are mixed and dissolved in deionized water. The amount of deionized water added is sufficient to dissolve the molybdenum and rhenium salts, and no special limit is required. The mixture is heated to 80°C to fully dissolve the molybdenum and rhenium salts. Ammonia water is added to adjust the pH to 9-10 to ensure that the soluble precursors of ammonium perrhenate and ammonium molybdate exist in ionic form in the solution. Then, the ammonium perrhenate solution and the ammonium molybdate solution are mixed to obtain a molybdenum-rhenium mixed solution.

[0058] S2: Preparation of molybdenum-rhenium doped mixed solution

[0059] Weigh out 1.0 wt% ZrO2 as the precursor of the oxide, zirconium nitrate (Zr(NO3)4·5H2O), and dissolve it in deionized water. The amount of deionized water added is sufficient to dissolve the zirconium salt; no special limit is required. Heat to 80°C to ensure complete dissolution, and then add it to a molybdenum-rhenium mixed solution to form a doped molybdenum-rhenium mixed solution. Here, 1.0 wt.% ZrO2 refers to the total mass of molybdenum in the molybdenum salt and rhenium in the rhenium salt.

[0060] S3: Heat treatment

[0061] The molybdenum-rhenium mixed solution was mechanically stirred to ensure thorough mixing, and then heated at 100°C to evaporate the water. When a small amount of liquid remained, a crystalline product was obtained. The crystalline product was then filtered, followed by a second filtration. The filtered crystalline product was dried at 80°C for 1 hour. After drying, the powder was collected and sieved through 60-mesh and 40-mesh sieves to ensure uniform and fine particle size, finally obtaining a composite powder.

[0062] S4: Calcination thermal decomposition

[0063] The composite powder was placed in a muffle furnace for calcination at a heating rate of 10℃ / min, heated to 550℃ and held for 3 hours, and then cooled with the furnace to obtain pyrolytic powder. At this time, ammonium molybdate ((NH4)2Mo2O7) was converted into molybdenum trioxide (MoO3), ammonium perrhenate was decomposed into low oxides of rhenium, and the zirconium oxide precursor was decomposed into zirconium oxide.

[0064] S5: Thermal reduction

[0065] Hydrogen gas is introduced into the muffle furnace to reduce the pyrolysis powder into molybdenum-rhenium alloy powder doped with oxides. Specifically, a two-stage reduction reaction is carried out by introducing a hydrogen atmosphere.

[0066] First stage: The heating rate is 10℃ / min, the holding temperature is 550℃, the holding time is 1 hour, the hydrogen flow rate is 100ml / s, and the hydrogen reduces molybdenum trioxide (MoO3) to molybdenum dioxide (MoO2).

[0067] The second stage involved a heating rate of 5℃ / min, a holding temperature of 1050℃ for 5 hours, and a hydrogen flow rate of 100 ml / s. During this stage, molybdenum dioxide (MoO2) was completely reduced to metallic molybdenum (Mo), and simultaneously, the lower oxides of rhenium were reduced to metallic rhenium (Re), yielding a zirconium-doped molybdenum-rhenium alloy powder. The molybdenum-rhenium alloy powder had the following composition: Mo-14wt.%Re-1.0wt.%ZrO2.

[0068] S6: Bar Preparation

[0069] Molybdenum-rhenium alloy powder doped with zirconium oxide was processed by cold isostatic pressing, high-temperature hydrogen sintering, forging and rotary forging to obtain Mo-14wt.%Re-1.0wt.%ZrO2 rods.

[0070] The pressure of cold isostatic pressing is 200 MPa; the high-temperature hydrogen sintering temperature is 2500℃; the forging temperature is 1350℃; the rotary forging temperature is 1100℃, and the deformation is >80%.

[0071] Test case

[0072] The strength of the alloys prepared in the examples was tested at high temperatures. The tests were conducted using a high-temperature tensile testing machine at tensile temperatures of 1100°C and 1300°C, with a loading rate of 1×10⁻⁶. -3 / s.

[0073] The test results for tensile strength at 1100℃ and 1300℃ are shown below. Figure 2 and Figure 3As can be seen from the figure, the alloy rods prepared in Examples 1 and 2 exhibit good tensile strength at both 1100℃ and 1300℃, while the tensile strength of other comparative alloys (Mo-14Re, Mo-43Re, Mo-14Re-0.2wt%La2O3, CP-Mo, TZM-Mo, Mo-14Re-1.0wt%La2O3, Mo-0.3wt%Y2O3) is lower than that of the alloys prepared in this example. It should also be noted that the comparative alloys Mo-14Re, Mo-14Re-0.2wt%La2O3, and Mo-14Re-1.0wt%La2O3 were synthesized using liquid-liquid doping, while the comparative alloys Mo-43Re, CP-Mo, TZM-Mo, and Mo-0.3wt%Y2O3 were synthesized using solid-solid doping.

[0074] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using a liquid-liquid doping process, characterized in that: Includes the following steps: S1: Preparation of molybdenum-rhenium mixed solution Molybdenum salt and rhenium salt are mixed in water, and the pH is adjusted to alkaline using ammonia water to obtain a molybdenum-rhenium mixed solution; In step S1, the proportion of rhenium in the rhenium salt to the total mass of molybdenum in the molybdenum salt and rhenium in the rhenium salt does not exceed 51 wt%; ammonia is added to adjust the pH to 9-10; S2: Preparation of molybdenum-rhenium doped mixed solution The precursor nitrate of the oxide is dissolved in water and then added to a molybdenum-rhenium mixed solution to form a molybdenum-rhenium doped mixed solution; In step S2, the oxide is zirconium oxide; the oxide accounts for 0.1~2.0 wt% of the total mass of molybdenum in the molybdenum salt and rhenium in the rhenium salt; the process of forming the doped molybdenum-rhenium mixed solution also includes a heating step, with a heating temperature of 75~85℃, to fully dissolve the mixed solution; S3: Heat treatment The molybdenum-rhenium mixed solution was mechanically stirred, and then the water was evaporated by heating to obtain a crystallized product. The crystallized product was then filtered, dried and sieved to obtain a composite powder. S4: Calcination thermal decomposition The composite powder was calcined in a muffle furnace to obtain pyrolytic powder; S5: Thermal reduction Hydrogen gas is introduced into the muffle furnace to reduce the pyrolysis powder into molybdenum-rhenium alloy powder doped with oxides; S6: Bar Preparation Molybdenum-rhenium alloy powder doped with oxides was processed by cold isostatic pressing, high-temperature hydrogen sintering, forging and rotary forging to obtain molybdenum-rhenium alloy rods doped with oxides. In step S3, the heating and evaporation temperature is 95~105℃; the filtration is performed more than twice; the drying temperature is 80~100℃, and the drying time is 1~2 hours; the sieving is performed by passing the material through a 60-mesh sieve and a 40-mesh sieve in sequence. In step S6, the pressure of cold isostatic pressing is 150MPa~250MPa; the high-temperature hydrogen sintering temperature is 2000℃~3000℃; the forging temperature is 1200℃~1500℃; the rotary forging temperature is 800℃~1200℃, and the deformation is >80%.

2. The method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using liquid-liquid doping process according to claim 1, characterized in that: In step S4, the calcination temperature is 500~600℃, the holding time is 1~5h, the heating rate is 8~12℃ / min, the molybdenum salt is converted into molybdenum trioxide, the rhenium salt is decomposed into rhenium low oxides, and the precursor of the oxides, nitrate, is decomposed into the corresponding oxides.

3. The method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using liquid-liquid doping process according to claim 2, characterized in that: In step S5, the thermal reduction includes two stages. In the first stage, molybdenum trioxide is reduced to molybdenum dioxide. In the second stage, molybdenum dioxide is completely reduced to metallic molybdenum. At the same time, the low oxide of rhenium is reduced to metallic rhenium.

4. The method for synthesizing oxide dispersion-strengthened molybdenum-rhenium alloys using the liquid-liquid doping process according to claim 3, characterized in that: In step S5, the first stage has a heating rate of 8~12℃ / min, a reduction temperature of 500~600℃, a holding time of 0.5~1 hour, and a hydrogen flow rate of 80~120ml / s. In the second stage, the heating rate is 3~6℃ / min, the reduction temperature is 1000~1100℃, the holding time is 4~6 hours, and the hydrogen flow rate is 80~120ml / s.

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