WO2024187539A1 - Preparation method for in-situ synthesized two-dimensional carbide dispersion toughened molybdenum alloy - Google Patents

Abstract

The present invention relates to a preparation method for an in-situ synthesized two-dimensional carbide dispersion toughened molybdenum alloy, comprising: mixing MoO2 with a two-dimensional MAX ceramic material, sieving, and then carrying out high-temperature hydrogen reduction to prepare molybdenum alloy precursor powder; then compacting by using a cold isostatic press, carrying out pressureless sintering and high-temperature calcination, and carrying out thermoplastic processing; and finally carrying out annealing treatment to obtain a high-strength and high-toughness molybdenum alloy. According to the present invention, the two-dimensional MAX ceramic material is used as a doping phase, and the two-dimensional carbide in-situ synthesized by MAX at a high temperature has large specific surface area and high surface energy, and can promote densification of the material, thereby improving the mechanical properties, such as strength and toughness, of the molybdenum alloy, effectively hindering movement and deformation of a grain boundary at a high temperature, and enabling the microstructure of the material at the high temperature to be more stable. In addition, the high-temperature strength of the molybdenum alloy at 1,200°C is greater than 300 MPa, and the recrystallization temperature of the molybdenum alloy is up to 1,500°C, and thus, the performance of the molybdenum alloy in a high-temperature scenario is improved, and the application range of the molybdenum alloy is expanded.

Description

Preparation method of in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy Technical Field

The present invention belongs to the technical field of powder metallurgy, and in particular relates to a method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy.

Background Art

Molybdenum metal is one of the most widely used refractory metal materials in industry. Due to its high melting point (2620±20℃), high density (10.2g/cm ³ ), high elastic modulus (280～390GPa), low linear thermal expansion coefficient (5.8×10 ^-6 ～6.2×10 ^-6 /K), high wear resistance, good electrical and thermal conductivity, good acid and alkali resistance and liquid metal corrosion resistance, molybdenum and its alloys have broad application prospects as high-temperature resistant structural materials and functional materials in various industrial fields such as steel, metallurgy, machinery, chemical industry, nuclear energy, electronics, aerospace, etc. Although molybdenum metal and its alloys have many performance advantages, their room temperature and high temperature strength are still insufficient to meet the demand for high temperature resistant structural materials for rapid development of science and technology. In particular, the low room temperature ductility of molybdenum metal leads to its poor machinability, which seriously limits its industrial application.

Oxides (La ₂ O ₃ , Ce ₂ O ₃ , Y ₂ O ₃ , ZrO ₂ , Al ₂ O ₃ ) and carbides (TiC, ZrC, HfC, TaC) are commonly used to strengthen molybdenum alloys. For example, adding oxide Al ₂ O ₃ to the molybdenum matrix can significantly improve the hardness and wear resistance of the molybdenum alloy. Adding La ₂ O ₃ to the molybdenum matrix can prepare a high-strength and tough molybdenum alloy with a yield strength of 813MPa, and can also obtain higher fracture toughness (121.5 MPa∙m ² ) and elongation (37.5%). Adding rare earth oxides can also increase the recrystallization temperature of the molybdenum alloy, so that the molybdenum alloy has better high-temperature creep resistance. If carbide TiC particles are added to the TZM alloy, it is found that adding 5vol.% TiC particles can increase the Vickers hardness of the alloy by 50%, and the bending strength by 46%, but the ductility of the alloy will decrease. Adding oxides to improve the performance of molybdenum alloys requires that the size of the oxide particles be at the nanometer level and that the particles be dispersed evenly inside the molybdenum grains. The process is relatively complex and requires high equipment, making it difficult to achieve large-scale application. Adding carbides to improve high-temperature mechanical properties requires that the carbides themselves have a high melting point, high hardness, and high chemical stability. Moreover, their performance is closely related to composition control, deformation process, and heat treatment process, which requires high requirements and is difficult to control.

The design principles of new high-performance molybdenum materials include: 1) improving low-temperature brittleness and reducing alloy DBTT; 2) increasing recrystallization temperature, improving mechanical properties and structural stability at high temperatures; 3) improving radiation embrittlement resistance. Traditional non-in-situ synthesized composite materials are often accompanied by the following disadvantages: residual pores, large grain size, non-uniform distribution of reinforcement phase, poor wettability, weak bonding interface between reinforcement phase and matrix, etc.

The Mn _{+ 1AXn} phase (where M is an early transition metal, A is an A-group element, and X is C or N) is a layered hexagonal solid. The unique crystal structure of the MAX phase gives it unique chemical bond characteristics: M and X are bonded by strong covalent bonds and ionic bonds; M and A are bonded by weaker covalent bonds or metallic bonds, which makes it easy for the MAX phase to slip along the basal plane [0001]. This unique bonding configuration enables it to combine many advantages of ceramic materials and metal materials, such as high modulus, low specific gravity, good electrical and thermal conductivity, machinability, thermal shock resistance, high damage tolerance, thermal stability, creep resistance and oxidation resistance. The existing strengthening process of molybdenum alloys, whether adding oxides or carbides, cannot simultaneously have high strength, high toughness and high temperature stability at room temperature and high temperature, which restricts its application in high temperature scenarios such as nuclear reactors. Therefore, in order to meet the requirements of use, it is necessary to further improve the comprehensive mechanical properties and high temperature stability of molybdenum alloys.

Summary of the invention

The purpose of the present invention is to provide a method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy, so as to improve the room temperature and high temperature strength of the molybdenum alloy, increase its elongation, refine the powder particle size, further improve its density, and simultaneously improve the toughness and strength of the molybdenum alloy.

The present invention is specifically implemented through the following technical solutions. According to the present invention, a method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy comprises the following steps:

(1): According to the requirements of the final product, weigh a certain amount of _MoO2 and two-dimensional MAX ceramic material, use a dual-power mixer to dry mix for 10 to 30 hours, and sieve for later use;

(2): The powder prepared in step (1) is subjected to high-temperature reduction in a reducing gas hydrogen atmosphere, wherein the reduction temperature is 700-1000°C, the hydrogen flow rate is 10-20 ^m3 /h, the reduction time is 8-25h, and the powder spreading height is ≤2/3, to prepare a molybdenum alloy precursor powder;

(3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and put it into the rubber mold, and use a cold isostatic press to press the blank;

(4): The green compact obtained in step (3) is subjected to pressureless sintering under a reducing gas, and after cooling in the furnace, a molybdenum alloy sintered green compact is obtained;

(5): heating the molybdenum alloy sintered blank prepared in step (4) to 1100-1600° C. in a protective hydrogen atmosphere (to prevent oxidation of molybdenum), keeping the temperature for 30-60 minutes, and then performing hot plastic processing;

(6): The molybdenum alloy billet prepared in step (5) is annealed in a protective hydrogen atmosphere (the purpose is to prevent molybdenum oxidation) to finally obtain a high-strength and tough molybdenum alloy, that is, an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy.

Preferably, the molybdenum dioxide used in step (1) has a particle size of 8-20 µm and a potassium impurity content of 5-10 ppm; the two-dimensional MAX ceramic material is lamellar Ti ₃ AlC ₂ with 3-10 layers, a purity of not less than 98%, and a particle size of 2-8 µm.

Furthermore, the particle size of the molybdenum alloy precursor powder obtained in step (2) is 1 to 2 µm.

Preferably, the pressure of the cold isostatic pressing of the billet in step (3) is 150 to 230 MPa, and the holding time is 10 to 30 min.

Preferably, the temperature of the pressureless sintering in step (4) is 1700-2100°C, the holding time is 6-10 hours, the hydrogen flow rate is 8-15 ^m3 /h, and the molybdenum alloy sintered blank is obtained after furnace cooling.

Furthermore, in step (5), the thermoplastic processing is one or a combination of rotary forging, rolling, extrusion or drawing; the total number of thermoplastic processing passes is 3 to 10 times, the deformation amount of each pass is 15 to 25%, and the total deformation amount is ≥50%.

Preferably, the annealing temperature of step (6) is 900-1500°C, and the holding time is 30-200 min.

Furthermore, the prepared in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy includes molybdenum grains and nano-TiC _0.67 uniformly distributed in the molybdenum grains, wherein the average particle size of the molybdenum grains is 10-20 μm, and the average particle size of the nano-TiC _0.67 uniformly distributed inside the molybdenum grains is 0.5-3 μm.

The present invention can also replace _MoO2 with _WO3 according to the above method to prepare an in-situ self-generated two-dimensional carbide dispersion-strengthened tungsten alloy; or replace _MoO2 with CuO to prepare an in-situ self-generated two-dimensional carbide dispersion-strengthened copper alloy; or replace _MoO2 with NiO to prepare an in-situ self-generated two-dimensional carbide dispersion-strengthened nickel alloy, thereby expanding the application of the present invention.

Furthermore, the two-dimensional MAX ceramic material in step (1) can also be any one or more of Zr ₃ AlC ₂ , Si ₃ AlC ₂ , Hf ₃ AlC ₂ , Zr ₂ AlC, Si ₂ AlC, Hf ₂ AlC ₂ , Zr ₄ AlC ₃ , Si ₄ AlC ₃ , Hf ₄ AlC ₃ , and is not limited to Ti ₃ AlC ₂ .

Compared with the prior art, the present invention has obvious advantages and beneficial effects, and has at least the following advantages:

(1) The present invention uses a MAX phase material with a high melting point, high hardness and high fracture toughness as a doping phase. By controlling the mass ratio of molybdenum dioxide and two-dimensional MAX material, the initial powder is subjected to hydrogen reduction, cold isostatic pressing, hydrogen pressureless sintering, thermoplastic treatment and annealing to obtain a high-strength and tough molybdenum alloy. The reinforcing phase MAX material selectively etches away Al under high-temperature sintering, and decomposes the original ternary layered structure into Al and two-dimensional Mxene material (TiC _0.67 ). Al generates aluminum oxide by absorbing impurity oxygen, and the aluminum oxide particles and the carbides generated by in-situ reaction decomposition are dispersed in the molybdenum matrix. Among them, the in-situ decomposed Al reduces the brittleness of the alloy by absorbing impurity oxygen to generate alumina, while the other in-situ generated Mxene particles are finer, have a large specific surface area and high surface energy, and can promote the densification of the material, thereby improving the mechanical properties of the molybdenum alloy such as yield strength and fracture toughness; and the Mxene particles generated by the in-situ reaction have better thermal stability and are mainly distributed on the grain boundaries, which effectively hinders the movement and deformation of the grain boundaries at high temperatures, thereby making the material's microstructure more stable at high temperatures, and making the molybdenum alloy have good high-temperature strength and high recrystallization temperature, thereby improving the performance of the molybdenum alloy in high-temperature scenarios and expanding the application range of the molybdenum alloy.

(2) The morphology and particle size of molybdenum powder have hereditary effects on the performance of molybdenum alloy. According to the concept of heredity in biology, the morphological evolution of particle agglomerates has obvious hereditary phenomena and is accompanied by a certain degree of variation. For the morphology of single particles, each generation has its own intrinsic characteristics, and variation is dominant, and there is basically no hereditary phenomenon. The hereditary characteristics of Fisher particle size are that the raw material particles are coarser, and the corresponding product particles are also coarser; the raw material particles are finer, and the corresponding product particles are also finer. The hereditary characteristics of impurity elements also have obvious characteristics. Volatile and easily contaminated elements are mainly subject to variation during the reduction process, while other impurity elements that are not volatile and do not pollute are mainly subject to inheritance. The present invention introduces fine secondary phase elements into _MoO2 to break the hereditary nature of particle agglomerates. The process of controlling the reduction _{of MoO2} to Mo is mainly internal diffusion, and the apparent activation energy of this step is 30.1kJ/mol. The transformation of small particles of _MoO2 follows the chemical vapor migration model. Due to the introduction of secondary phases, Mo powder is overburned, the edges are arced, and the molybdenum powder is nearly spherical. The present invention prepares fine and uniform molybdenum powder, the powder has a Fisher particle size of 1 to 2 μm and a loose density of 0.7 to 0.9 g/cm³.

(3) The present invention can further refine the grains and improve the density and performance of the molybdenum alloy through the thermoplastic deformation process. The microstructure of the in-situ self-generated two-dimensional carbide dispersion toughened molybdenum alloy prepared by the above method includes molybdenum grains and nano-TiC _0.67 uniformly distributed in the molybdenum grains, wherein the average width of the molybdenum grains is 10 to 20 μm, and the average particle size of the nano-TiC _0.67 particles uniformly distributed inside the molybdenum grains is 0.5 to 3 μm.

(4) The molybdenum alloy of the present invention has excellent comprehensive properties and outstanding high-temperature performance. The preparation method is green and efficient. It can be mass-produced and can produce large-size products. It has great industrial application value and will have very good application prospects in nuclear reactors, key aerospace components, etc.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a SEM image of the molybdenum alloy precursor powder prepared in Example 1.

Figure 2 is an optical microscopy metallographic image of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in Example 1.

Figure 3 is an optical microscopy metallographic image of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in Example 2.

Figure 4 is an optical microscopic metallographic image of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in Example 3.

Figure 5 is the stress-strain curves of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy and pure molybdenum prepared in Examples 1 to 3.

Figure 6 is the high temperature stress-strain curves of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy and pure molybdenum prepared in Example 1 to Example 3 at 1200°C.

Implementation

In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

The preparation method of the in-situ self-generated two-dimensional carbide dispersion toughened molybdenum alloy provided by the present invention mainly comprises the following steps:

(1): According to the requirements of the final product, weigh a certain amount of _MoO2 and _{Ti3AlC2 powder} , use a dual-power mixer to dry mix for 10 to 30 hours, and sieve for use; the molybdenum dioxide used has a particle size of 8 to 20µm and an impurity potassium content of 5 to 10ppm; _{Ti3AlC2 is} lamellar, with 3 to 10 layers, a purity of not less than 98%, and a particle size of 2 to 8µm.

(2): The powder prepared in step (1) is subjected to high-temperature reduction in a reducing gas hydrogen atmosphere, with a reduction temperature of 700-1000°C, a hydrogen flow rate of 10-20 m ³ /h, a reduction time of 8-25h, and a powder spreading height of ≤2/3, to prepare a molybdenum alloy precursor powder with a particle size of 1-2µm.

(3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and load it into the rubber mold, and use a cold isostatic press to press the blank with a pressure of 150-230 MPa and a holding time of 10-30 min.

(4): The pressed green sheet obtained in step (3) is subjected to pressureless sintering in the presence of reducing gas hydrogen at a sintering temperature of 1700-2100°C, a holding time of 6-10 hours, a hydrogen flow rate of 8-15 ^m3 /h, and then cooled in the furnace to obtain a molybdenum alloy sintered green sheet; the particle size of the molybdenum grains in the molybdenum alloy is about 20-50 μm.

(5): Heat the molybdenum alloy billet prepared in step (4) to 1100-1500°C in a protective gas hydrogen atmosphere (to prevent molybdenum oxidation), keep it warm for 15-60 minutes, and then perform thermoplastic processing. The thermoplastic processing is one or a combination of rotary forging, rolling, extrusion or drawing. The total number of thermoplastic deformation processes is 3-10 times, the deformation amount of each process is 15-25%, and the total deformation amount is ≥50%.

(6): Anneal the molybdenum alloy billet prepared in step (5) in a protective hydrogen atmosphere at a temperature of 900-1500°C for 30-200 min to finally obtain a high-strength and tough molybdenum alloy, i.e., an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy.

The microstructure of the in-situ self-generated two-dimensional carbide dispersion toughened molybdenum alloy prepared by the above method includes molybdenum grains and nano-TiC _0.67 uniformly distributed in the molybdenum grains, wherein the average width of the molybdenum grains is 10-20 μm, and the average particle size of the nano-TiC _0.67 particles uniformly distributed inside the molybdenum grains is 0.5-3 μm.

As a further preference, in step (1), the mass of _MoO2 accounts for 95-99.5% of the total mass of the mixed powder _{of MoO2 and Ti3AlC2} , and the mass of _Ti3AlC2 accounts for 0.5-5% of the total mass of the mixed powder _of MoO2 and _{Ti3AlC2 .}

The present invention adopts the above method to obtain an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum _alloy . In other embodiments, the two-dimensional MAX ceramic material _Ti3AlC2 can be replaced by any _one or more of 312 phase MAX phase ceramics ( _Zr3AlC2 or _Si3AlC2 or _Hf3AlC2 ), 211 phase MAX phase ceramics ( _Zr2AlC or _Si2AlC or _Hf2AlC2 ) and ₄₁₃ phase MAX phase ceramics ( _Zr4AlC3 or _Si4AlC3 or _{Hf4AlC3 )} , and _an in-situ self-generated two-dimensional carbide dispersion _- strengthened molybdenum alloy can also be obtained, except that the reinforcing phase carbide is changed _. For those skilled in _the art, the replacement scheme is easy to understand and will not be elaborated in the present invention.

At the same time, by replacing the raw material _MoO2 , the above method can also be used to prepare in-situ self-generated two-dimensional carbide dispersion-strengthened tungsten alloy, copper alloy or nickel alloy. For example, the metal matrix material for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened tungsten alloy can be _WO3 , the metal matrix material for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened copper alloy can be CuO, and the metal matrix material for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened nickel alloy can be NiO. The preparation method is the same as the preparation method of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy, which will not be repeated in the present invention.

The following is a detailed explanation with specific embodiments.

(1): According to the requirements of the final product, 99 parts of _MoO2 and 1 part of _{Ti3AlC2 powder} are put into a dual-power mixer and dry mixed for 20 hours, and then sieved through a 300-mesh sieve for use.

(2): The powder obtained in step (1) is subjected to high-temperature reduction in a reducing gas hydrogen atmosphere, with a reduction temperature of 800°C, a hydrogen flow rate of 18 ^m3 /h, a reduction time of 22h, and a powder spreading height of 2/3 to prepare a molybdenum alloy precursor powder with a particle size of 1 to 2µm.

(3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and put it into the rubber mold, and use a cold isostatic press to press the blank with a pressure of 200 MPa and a holding time of 15 minutes.

(4): The pressed blank obtained in step (3) is subjected to pressureless sintering in the presence of reducing gas hydrogen at a sintering temperature of 2000°C and a holding time of 10 h. After cooling in the furnace, a molybdenum alloy sintered blank is obtained; the particle size of the molybdenum grains in the molybdenum alloy is approximately 35~50μm.

(5): Heat the molybdenum alloy billet prepared in step (4) to 1200°C in a protective hydrogen atmosphere, keep it warm for 60 minutes, and then perform thermoplastic processing. The thermoplastic processing is rolling. The total number of thermoplastic deformation processes is 5 times, the deformation amount of each process is 25%, and the total deformation amount is 76.23%.

(6): The molybdenum alloy blank prepared in step (5) is annealed in a protective hydrogen atmosphere at a temperature of 1000°C for 160 minutes to finally obtain a high-strength and toughness molybdenum alloy, namely an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy with a particle size of 12-20 μm, a particle size of secondary phase TiC _0.67 particles uniformly dispersed in the molybdenum grains of 0.5-3 μm, and a density of the molybdenum alloy of 99%.

The room temperature mechanical properties of the in-situ two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in this embodiment were tested using an American INSTRON-5967 universal testing machine, and its high temperature compressive strength was tested using an American Gleeble-1500D thermal simulation testing machine. The in-situ two-dimensional carbide dispersion-strengthened molybdenum alloy obtained in this embodiment had a room temperature tensile strength of 809 MPa, an elongation of 47.8%, and a high temperature compressive strength of 320 MPa at 1200°C, which were respectively increased by 72.1%, 91.2%, and 113.3% compared to pure molybdenum metal, thereby increasing the plastic toughness of the molybdenum alloy without reducing its strength.

Figure 1 is a morphology picture of the molybdenum alloy precursor powder prepared in step (2) of this embodiment, which can be seen to be a nearly spherical powder of 1~2μm.

Figure 2 is the microstructure morphology (optical microscopy metallographic image) of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in this embodiment. The particle size of the molybdenum alloy is 12~20μm. The larger secondary phases are evenly distributed at the grain boundaries, and the fine secondary phase particles are evenly distributed inside the grains.

(1): According to the requirements of the final product, 98.5 parts of _MoO2 and 1.5 parts of _{Ti3AlC2 powder} were put into a dual-power mixer and dry mixed for 20 hours, and then passed through a 300-mesh sieve for later use.

(2): The powder obtained in step (1) is subjected to high-temperature reduction in a reducing gas hydrogen atmosphere, with a reduction temperature of 900°C, a hydrogen flow rate of 20 ^m3 /h, a reduction time of 18h, and a powder spreading height of ≤2/3, to prepare a molybdenum alloy precursor powder with a particle size of 1 to 2µm.

(3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and put it into the rubber mold, and use a cold isostatic press to press the blank with a pressure of 200 MPa and a holding time of 15 minutes.

(4): The pressed blank obtained in step (3) is subjected to pressureless sintering in the presence of reducing gas hydrogen at a sintering temperature of 1900°C and a holding time of 10 h. After cooling in the furnace, a molybdenum alloy sintered blank is obtained; the particle size of the molybdenum grains in the molybdenum alloy is approximately 25~35μm.

(5): The molybdenum alloy billet prepared in step (4) is heated to 1300°C in a protective hydrogen atmosphere (to prevent molybdenum oxidation), kept warm for 60 minutes, and then subjected to thermoplastic processing. The thermoplastic processing is one or a combination of rotary forging, rolling, extrusion or drawing. The total number of thermoplastic deformation processes is 8 times, the deformation amount of each process is 20%, and the total deformation amount is 83.22%.

(6): The molybdenum alloy blank prepared in step (5) is annealed in a protective hydrogen atmosphere at a temperature of 1100°C for 160 minutes to finally obtain a high-strength and toughness molybdenum alloy, namely an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy with a particle size of 10-15 μm, a particle size of secondary phase TiC _0.67 particles uniformly dispersed in the molybdenum grains of 0.5-3 μm, and a density of the molybdenum alloy of 99.2%.

The room temperature mechanical properties and high temperature compressive strength of the in-situ self-generated two-dimensional carbide dispersion strengthened molybdenum alloy prepared in this example were tested by the method described in Example 1. The room temperature tensile strength was 1024 MPa, the elongation was 48.5%, and the high temperature compressive strength at 1200°C was 335 MPa, which were respectively increased by 118%, 94% and 123.3% compared with pure molybdenum metal, thereby increasing the plasticity and toughness of the molybdenum alloy without reducing the strength.

Figure 3 is a microstructure morphology image (optical microscopy metallographic image) of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in this embodiment. The particle size of the molybdenum alloy is 10~15μm. The larger secondary phases are evenly distributed at the grain boundaries, and the fine secondary phase particles are evenly distributed inside the grains.

(1): According to the requirements of the final product, 98 parts of _MoO2 and 2 parts of _{Ti3AlC2 powder} are put into a dual-power mixer and dry mixed for 20 hours, and then sieved through a 300-mesh sieve for use.

(2): The powder obtained in step (1) is subjected to high-temperature reduction in a reducing gas hydrogen atmosphere, with a reduction temperature of 1000°C, a hydrogen flow rate of 15 ^m3 /h, a reduction time of 20h, and a powder spreading height of ≤2/3, to prepare a molybdenum alloy precursor powder with a particle size of 1 to 2µm.

(3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and put it into the rubber mold, and use a cold isostatic press to press the blank with a pressure of 200 MPa and a holding time of 15 minutes.

(4): The pressed blank obtained in step (3) is subjected to pressureless sintering in the presence of reducing gas hydrogen at a sintering temperature of 1800°C and a holding time of 10 h. After cooling in the furnace, a molybdenum alloy sintered blank is obtained; the particle size of the molybdenum grains in the molybdenum alloy is approximately 20~35μm.

(5): The molybdenum alloy billet prepared in step (4) is heated to 1400°C in a protective hydrogen atmosphere (to prevent molybdenum oxidation), kept warm for 60 minutes, and then subjected to thermoplastic processing. The thermoplastic processing is one or a combination of rotary forging, rolling, extrusion or drawing. The total number of thermoplastic deformation processes is 10 times, the deformation amount of each process is 25%, and the total deformation amount is 94.5%.

(6): The molybdenum alloy blank prepared in step (5) is annealed in a protective hydrogen atmosphere at a temperature of 1300°C for 160 minutes to finally obtain a high-strength and toughness molybdenum alloy, namely an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy with a particle size of 10-12 μm, a particle size of secondary phase TiC _0.67 particles uniformly dispersed in the molybdenum grains of 0.5-3 μm, and a density of the molybdenum alloy of 99.4%.

The room temperature mechanical properties and high temperature compressive strength of the in-situ self-generated two-dimensional carbide dispersion strengthened molybdenum alloy prepared in this example were tested by the method described in Example 1. The room temperature tensile strength was 1305 MPa, the elongation was 47.9%, and the high temperature compressive strength at 1200°C was 415 MPa, which were respectively increased by 177.6%, 91.6% and 176.6% compared with pure molybdenum metal, thereby increasing the plasticity and toughness of the molybdenum alloy without reducing the strength.

Figure 4 is a microstructure morphology image (optical microscopy metallographic image) of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy prepared in this embodiment. The particle size of the molybdenum alloy is 10~12μm. The larger secondary phases are evenly distributed at the grain boundaries, and the fine secondary phase particles are evenly distributed inside the grains.

In step (1), Ti ₃ AlC ₂ is not added. The other steps are the same as in Example 1 to obtain a molybdenum product. According to the test method of Example 1, the prepared pure molybdenum has a particle size of 70-100 μm, a density of 96%, a room temperature tensile strength of 470 MPa, an elongation of 25%, and a high temperature compressive strength of 150 MPa at 1200°C.

Figure 5 is the stress-strain curve of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy obtained in each embodiment and the pure molybdenum obtained in Comparative Example 1. The tensile strength of the molybdenum alloys obtained by different processes in the embodiments is slightly different, but as a whole it is higher than pure molybdenum.

Figure 6 is the stress-strain curves of the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy obtained in each embodiment and the pure molybdenum obtained in Comparative Example 1 at a high temperature of 1200°C. The compressive strength of the molybdenum alloys obtained by different processes in the embodiments at 1200°C is greatly improved compared with that of pure molybdenum.

Molybdenum dioxide and lanthanum oxide are added in step (1), and the other steps are the same as in Example 1 to obtain a molybdenum product. The prepared molybdenum alloy has a particle size of 30-50 μm, a density of 97%, a room temperature tensile strength of 653 MPa, an elongation of 20%, and a high temperature compressive strength of 210 MPa at 1200°C. Compared with the pure molybdenum in Comparative Example 1, the strength is improved, but the plasticity and toughness are poor.

The above is only an embodiment of the present invention, and does not impose any form of limitation on the present invention. The present invention can also have other forms of embodiments according to the above structures and functions, which are no longer listed one by one. Therefore, any simple modification, equivalent changes and modifications made to the above embodiments by any technician familiar with the profession based on the technical essence of the present invention without departing from the scope of the technical solution of the present invention, still fall within the scope of the technical solution of the present invention.

Claims (10)

1. A method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy, characterized by comprising the following steps:

   (1): According to the requirements of the final product, weigh a certain amount of _MoO2 and two-dimensional MAX ceramic material, use a dual-power mixer to dry mix for 10 to 30 hours, and sieve for later use;

   (2): The powder prepared in step (1) is subjected to high-temperature reduction in a hydrogen atmosphere, wherein the reduction temperature is 700-1000°C, the hydrogen flow rate is 10-20 m ³ /h, the reduction time is 8-25h, and the powder spreading height is ≤2/3, to prepare a molybdenum alloy precursor powder;

   (3): According to the required size of the final product, select a suitable rubber mold, weigh a certain amount of the prepared molybdenum alloy precursor powder and put it into the rubber mold, and use a cold isostatic press to press the blank;

   (4): The pressed green body obtained in step (3) is subjected to pressureless sintering in a hydrogen atmosphere, and after cooling in the furnace, a molybdenum alloy sintered green body is obtained;

   (5): heating the molybdenum alloy sintered blank obtained in step (4) to 1100-1600° C. in a hydrogen atmosphere, keeping the temperature for 30-60 min, and then performing thermoplastic processing;

   (6): Annealing the molybdenum alloy billet obtained in step (5) in a hydrogen atmosphere to finally obtain an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy.
2. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as claimed in claim 1, characterized in that the molybdenum dioxide used in step (1) has a particle size of 8 to 20 µm and a potassium impurity content of 5 to 10 ppm; the two-dimensional MAX ceramic material is lamellar Ti ₃ AlC ₂ with 3 to 10 layers, a purity of not less than 98%, and a particle size of 2 to 8 µm.
3. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as described in claim 1 or 2 is characterized in that the particle size of the molybdenum alloy precursor powder obtained in step (2) is 1 to 2 µm.
4. The method for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as described in claim 1 is characterized in that the pressure of the cold isostatic pressing of the billet in step (3) is 150 to 230 MPa, and the holding time is 10 to 30 minutes.
5. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as claimed in claim 1, characterized in that the temperature of the pressureless sintering in step (4) is 1700-2100°C, the holding time is 6-10h, the hydrogen flow rate is 8-15 ^m3 /h, and the molybdenum alloy sintered billet is obtained after furnace cooling.
6. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as described in claim 1 is characterized in that the hot plastic processing in step (5) is one or a combination of rotary forging, rolling, extrusion or drawing; the total number of hot plastic processing passes is 3 to 10 times, the deformation amount of each pass is 15 to 25%, and the total deformation amount is ≥50%.
7. The method for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as described in claim 1 is characterized in that the annealing temperature in step (6) is 900-1500°C and the holding time is 30-200 min.
8. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as claimed in claim 1 or 2, characterized in that the prepared in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy comprises molybdenum grains and nano-TiC _0.67 uniformly distributed in the molybdenum grains, the average particle size of the molybdenum grains is 10 to 20 μm, and the average particle size of the nano-TiC _0.67 uniformly distributed in the molybdenum grains is 0.5 to 3 μm.
9. The method for preparing the in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy according to claim 1, characterized in that MoO ₂ is replaced with WO ₃ according to the above method to prepare the in-situ self-generated two-dimensional carbide dispersion-strengthened tungsten alloy;

   Or replace _MoO2 with CuO to prepare in-situ self-generated two-dimensional carbide dispersion-strengthened copper alloy;

   Or replace _MoO2 with NiO to prepare in-situ self-generated two-dimensional carbide dispersion-strengthened nickel alloy.
10. The method for preparing an in-situ self-generated two-dimensional carbide dispersion-strengthened molybdenum alloy as claimed in claim 1 or 9, characterized in that the two-dimensional MAX ceramic material in step (1) is selected from any one or more of Zr ₃ AlC ₂ , Si ₃ AlC ₂ , Hf ₃ AlC ₂ , Zr ₂ AlC, Si ₂ AlC, Hf ₂ AlC ₂ , Zr ₄ AlC ₃ , Si ₄ AlC ₃ , and Hf ₄ AlC ₃ .