High-toughness high-density tungsten alloy material and preparation method thereof

Abstract

The application relates to the technical field of metallurgy, in particular to a high-strength and high-toughness high-density tungsten alloy material and a preparation method thereof. The preparation method of the high-strength and high-toughness high-density tungsten alloy material comprises the following steps: mechanically ball-milling raw material powder to obtain homogenized modified composite powder; the raw material powder is tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder; the homogenized modified composite powder comprises refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution; cold isostatic pressing the homogenized modified composite powder to obtain a cold-pressed blank; liquid phase sintering the cold-pressed blank to obtain a sintered blank; the temperature of the liquid phase sintering is 1475-1530 DEG C, and the holding time is 60-130 min; cyclic vacuum heat treatment is conducted on the sintered blank to obtain the high-strength and high-toughness high-density tungsten alloy material. The tungsten alloy material prepared by the application can greatly improve the strength while still maintaining high plasticity and toughness.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, and in particular to a high-strength, high-toughness, high-density tungsten alloy material and its preparation method. Background Technology

[0002] High-density tungsten alloys are a class of alloys with tungsten as the base material (containing 80-97% tungsten) and appropriate amounts of elements such as Ni, Cu, Fe, Co, Mo, and Cr. Because they overcome the brittleness of tungsten and maintain its excellent properties such as high melting point, high density, and low coefficient of expansion, they have been widely used in aerospace, military, and civilian industries.

[0003] Currently, the preparation of high-density tungsten alloys is mainly carried out through traditional mechanical mixing and liquid phase sintering methods. The main disadvantages are poor powder mixing uniformity, serious chemical composition segregation, coarse internal structure, and complex process, which result in low overall performance of tungsten alloy materials, especially in terms of plasticity and toughness, which are difficult to meet the requirements of higher performance in use. Summary of the Invention

[0004] In view of this, the purpose of this invention is to provide a high-strength, high-toughness, high-density tungsten alloy material and its preparation method. The tungsten alloy material prepared by this invention maintains high ductility and toughness while significantly improving strength.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing a high-strength, high-toughness, high-density tungsten alloy material, comprising the following steps:

[0007] The raw material powder is mechanically ball-milled to obtain a homogeneous modified composite powder; the raw material powder is tungsten powder, nickel powder, iron powder, cobalt powder, and lanthanum powder; by mass percentage, the raw material powder contains 90-93% tungsten powder, 4.9-7% nickel powder, 1.0-1.4% iron powder, 0.3-1.2% cobalt powder, and 0.2-0.4% lanthanum powder; the homogeneous modified composite powder comprises refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution;

[0008] The homogeneous modified composite powder is subjected to cold isostatic pressing to obtain a cold-pressed blank;

[0009] The cold-pressed billet is subjected to liquid-phase sintering to obtain a sintered billet; the liquid-phase sintering temperature is 1475-1530℃, and the holding time is 60-130min.

[0010] The sintered billet is subjected to cyclic vacuum heat treatment to obtain the high-strength, high-toughness, high-density tungsten alloy material;

[0011] The cyclic vacuum heat treatment includes: heating the sintered billet to 900-1200°C under vacuum conditions for a first holding time of 2-4 hours, and then cooling it to room temperature; heating the billet cooled to room temperature to 700-900°C under vacuum conditions for a second holding time of 2-4 hours, and then cooling it to room temperature.

[0012] Preferably, a process control agent is added during the mechanical ball milling; the mass of the process control agent is 0.5-2% of the total mass of the raw material powder; the process control agent is anhydrous ethanol and / or zinc stearate.

[0013] Preferably, the conditions for mechanical ball milling include: a ball-to-material ratio of (5-25):1, a ball milling speed of 200-550 r / min, and a ball milling time of 5-15 h; the mechanical ball milling is carried out under a protective atmosphere.

[0014] Preferably, the average particle size of the refined tungsten powder is 500 nm to 5 μm, and the average grain size is 14 to 100 nm; the average particle size of the nanocrystalline nickel-based supersaturated solid solution is 0.2 to 2 μm, and the average grain size is 8 to 100 nm.

[0015] Preferably, the pressure of the cold isostatic pressing is 200-350 MPa, the time of the cold isostatic pressing is 20-60 s, and the relative density of the cold-pressed billet is 75-85%.

[0016] Preferably, the liquid phase sintering is performed under a protective atmosphere.

[0017] Preferably, the relative density of the sintered billet is 99.0% to 99.9%.

[0018] Preferably, the rates of the first and second heating are independently 10–30 °C / min.

[0019] Preferably, the vacuum degree of the cyclic vacuum heat treatment is not less than 5.0 × 10⁻⁶. -2 Pa.

[0020] This invention provides a high-strength, high-toughness, high-density tungsten alloy material prepared by the method described above. This high-strength, high-toughness, high-density tungsten alloy material exhibits a tensile strength ≥1150 MPa, elongation ≥25%, and impact toughness ≥130 J / cm² at room temperature. 2 .

[0021] This invention utilizes mechanical ball milling to thoroughly mix tungsten powder, nickel powder, iron powder, cobalt powder, and lanthanum powder, while simultaneously achieving partial dissolution of tungsten into a nickel-based solid solution. This yields a homogeneous modified composite powder with uniform two-phase distribution, consisting of refined tungsten powder and a nanocrystalline nickel-based supersaturated solid solution (referring to tungsten being saturated at low temperatures and subsequently used as a binder phase). Subsequent liquid-phase sintering transforms the nickel-based solid solution into a liquid phase that wets the tungsten powder, enhancing the bond between the binder phase and tungsten. During liquid-phase sintering, the tungsten powder further dissolves and diffuses. Because some tungsten has already dissolved during the initial mechanical ball milling, the amount of tungsten dissolved is significantly increased, resulting in solid solution strengthening. Furthermore, the mechanical ball milling process further enhances the tungsten powder's properties. Refining the tungsten powder effectively inhibits the growth of tungsten particles during liquid-phase sintering, suppresses compositional segregation, and enables high density to be achieved through short-time sintering at relatively low temperatures. The resulting fine tungsten grains and significant grain refinement strengthen the alloy, leading to high overall mechanical properties. Subsequent cyclic vacuum heat treatment achieves precipitation strengthening of tungsten, eliminating the negative impact of hydrogen embrittlement on alloy performance. This further improves the wettability of the binder phase to W particles, facilitating the acquisition of a microstructure with uniform microstructure and composition. Furthermore, it enhances the interfacial strength between the W phase and the binder phase, effectively improving the overall performance of the high-density tungsten alloy and meeting the application requirements in special environments.

[0022] The results of the examples show that the high-density tungsten alloy material prepared by the present invention has a room temperature tensile strength ≥1150MPa, an elongation ≥25%, and an impact toughness ≥130J / cm. 2 It has excellent overall performance.

[0023] In addition, the liquid phase sintering temperature of the present invention is low for a short period of time, which also has the advantage of low energy consumption. Attached Figure Description

[0024] Figure 1 A macroscopic photograph of the refined tungsten powder in Example 1;

[0025] Figure 2 A macroscopic photograph of the nickel-based supersaturated solid solution of Example 1;

[0026] Figure 3 This is a transmission electron microscope (TEM) image of the nickel-based supersaturated solid solution from Example 1.

[0027] Figure 4 The macroscopic morphology of the homogeneous modified composite powder in Example 1 is shown.

[0028] Figure 5 This is a microstructure diagram of the high-density tungsten alloy material in Example 1. Detailed Implementation

[0029] This invention provides a method for preparing a high-strength, high-toughness, high-density tungsten alloy material, comprising the following steps:

[0030] The raw material powder is mechanically ball-milled to obtain a homogeneous modified composite powder; the raw material powder is tungsten powder, nickel powder, iron powder, cobalt powder, and lanthanum powder; by mass percentage, the raw material powder contains 90-93% tungsten powder, 4.9-7% nickel powder, 1.0-1.4% iron powder, 0.3-1.2% cobalt powder, and 0.2-0.4% lanthanum powder; the homogeneous modified composite powder comprises refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution;

[0031] The homogeneous modified composite powder is subjected to cold isostatic pressing to obtain a cold-pressed blank;

[0032] The cold-pressed billet is subjected to liquid-phase sintering to obtain a sintered billet;

[0033] The sintered billet is subjected to cyclic vacuum heat treatment to obtain the high-strength, high-toughness, high-density tungsten alloy material;

[0034] The cyclic vacuum heat treatment includes: heating the sintered billet to 900-1200°C under vacuum conditions for a first holding time of 2-4 hours, and then cooling it to room temperature; heating the billet cooled to room temperature to 700-900°C under vacuum conditions for a second holding time of 2-4 hours, and then cooling it to room temperature.

[0035] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0036] This invention involves mechanically ball milling raw material powder to obtain homogeneous modified composite powder.

[0037] In this invention, the raw material powders are tungsten powder, nickel powder, iron powder, cobalt powder, and lanthanum powder. In this invention, the tungsten powder is preferably reduced tungsten powder, with a purity preferably above 99.9% and an average particle size preferably of 1-50 μm. In specific embodiments, the average particle size of the tungsten powder can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 μm. The nickel powder is preferably carbonyl nickel powder, with a purity preferably above 99.5% and an average particle size preferably of 1-50 μm. In specific embodiments, the average particle size of the nickel powder can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45, or 50 μm. The iron powder is preferably carbonyl iron powder, with a purity preferably above 99.5% and an average particle size preferably of 1-50 μm. The average particle size of the iron powder in the embodiments can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 μm; the cobalt powder is preferably water-atomized cobalt powder, with a purity preferably above 99.5% and an average particle size preferably between 1 and 50 μm. In specific embodiments, the average particle size of the cobalt powder can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 μm; the lanthanum powder is preferably high-purity lanthanum powder, with a purity preferably above 99.9% and an average particle size preferably between 1 and 50 μm. In specific embodiments, the average particle size of the lanthanum powder can be 1, 5, 10, 15, 20, 25, 30, 35, 40, 45 or 50 μm.

[0038] In this invention, the tungsten powder content in the raw material powder is 90-93% by mass percentage, and in specific embodiments it can be 90%, 91%, 92%, or 93%; the nickel powder content in the raw material powder is 4.9-7%, and in specific embodiments it can be 4.9%, 5.5%, 6%, 6.5%, or 7%; the iron powder content in the raw material powder is 1.0-1.4%, and in specific embodiments it can be 1.0%, 1.1%, 1.2%, 1.3%, or 1.4%; the cobalt powder content in the raw material powder is 0.3-1.2%, and in specific embodiments it can be 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1.0%, or 1.2%; the lanthanum powder content in the raw material powder is 0.2-0.4%, and in specific embodiments it can be 0.2%, 0.3%, or 0.4%.

[0039] In this invention, the preferred rotational speed of the mechanical ball mill is 200–550 rpm, and in specific embodiments, it can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, 500 rpm, or 550 rpm; the preferred time for the mechanical ball mill is 5–15 hours, and in specific embodiments, it can be 5 hours, 8 hours, 10 hours, 12 hours, or 15 hours; the preferred ball-to-material ratio for the mechanical ball mill is (5–25):1, and in specific embodiments, it can be 5:1, 10:1, 15:1, 20:1, or 25:1; the mechanical ball mill is preferably carried out under a protective atmosphere; the protective gas providing the protective atmosphere is preferably high-purity argon (purity ≥99.99%) or nitrogen (purity ≥99.99%). This invention, by performing mechanical ball milling under a protective atmosphere, can prevent the powder from being oxidized during the ball milling process. This invention does not have special requirements for the equipment used in the mechanical ball mill; any ball milling equipment well known in the art can be used, such as a stirred high-energy ball mill. This invention does not have special requirements for the grinding ball material used in the mechanical ball mill; any grinding ball material well known in the art is acceptable. In the embodiments of this invention, pure tungsten balls with a diameter of 8 mm are specifically used to avoid introducing impurities during mechanical ball milling.

[0040] In this invention, a process control agent is preferably added during the mechanical ball milling process. The process control agent is preferably anhydrous ethanol and / or zinc stearate; the amount of process control agent added is preferably 0.5-2% of the total mass of the raw material powder. In this invention, adding an appropriate process control agent can significantly improve the powder yield of the mechanical ball mill and is beneficial for uniform powder mixing and industrial production.

[0041] In this invention, after mechanical ball milling, tungsten powder is refined, and nickel powder, iron powder, cobalt powder and lanthanum powder form a solid solution with nickel as the matrix. At the same time, tungsten powder partially dissolves and reaches saturation in the solid solution, resulting in a nanocrystalline nickel-based supersaturated solid solution that is saturated at low temperature. This forms a homogeneous modified composite powder composed of refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution. The average particle size of the refined tungsten powder is preferably 500 nm to 5 μm, and in specific embodiments it can be 500 nm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 4 μm or 5 μm; the average grain size of the refined tungsten powder is preferably 14 to 100 nm, and in specific embodiments it can be 14 nm, 30 nm, 50 nm, 70 nm or 100 nm; the average particle size of the nanocrystalline nickel-based supersaturated solid solution is preferably 0.2 to 2 μm, and in specific embodiments it can be 0.2 μm, 0.5 μm, 1.2 μm, 1.5 μm or 2 μm; the average grain size of the nanocrystalline nickel-based supersaturated solid solution is preferably 8 to 100 nm, and in specific embodiments it can be 8 nm, 20 nm, 40 nm, 60 nm, 80 nm or 100 nm.

[0042] In this invention, a homogeneous modified composite powder formed by mechanically ball-milled and uniformly distributed tungsten powder and nanocrystalline nickel-based supersaturated solid solution can increase the amount of tungsten dissolved in the nickel-based solid solution. At the same time, it can also effectively prevent tungsten particles from growing during subsequent liquid-phase sintering. By refining the grains, the overall mechanical properties of the sintered material are improved.

[0043] After obtaining the homogeneous modified composite powder, the present invention performs cold isostatic pressing on the homogeneous modified composite powder to obtain a cold-pressed billet.

[0044] In this invention, the pressure of the cold isostatic pressing is preferably 200-350 MPa, and in specific embodiments it can be 200 MPa, 250 MPa, 290 MPa, 300 MPa, or 350 MPa; the time of the cold isostatic pressing is preferably 20-60 s, and in specific embodiments it can be 20 s, 30 s, 40 s, 50 s, or 60 s. Under this pressure, the present invention can obtain a cold-pressed billet with higher density and more uniform density distribution and porosity, which is beneficial for the uniform filling of pores by the liquid phase in the subsequent liquid phase sintering process, thus reducing the likelihood of component segregation. In this invention, the relative density of the cold-pressed billet is preferably 75-85%, and in specific embodiments it can be 75%, 77%, 80%, 81%, 83%, or 85%.

[0045] In this invention, the homogeneous modified composite powder is preferably placed in a rubber sleeve and subjected to cold isostatic pressing. This invention does not have special requirements for the thickness of the rubber sleeve; a thickness well-known in the art can be used, which is 4 mm in a specific embodiment. In this invention, the cold-pressed blank is preferably a bar stock.

[0046] After obtaining the cold-pressed billet, the present invention performs liquid-phase sintering on the cold-pressed billet to obtain a sintered billet.

[0047] In this invention, the preferred temperature for liquid phase sintering is 1475–1530°C, and in specific embodiments, it can be 1475°C, 1495°C, 1510°C, or 1530°C; the preferred holding time for liquid phase sintering is 60–130 min, and in specific embodiments, it can be 60 min, 80 min, 95 min, 110 min, or 130 min. In this invention, the liquid phase sintering is preferably carried out under a protective atmosphere; the protective atmosphere is preferably a hydrogen atmosphere. This invention transforms a nickel-based solid solution into a liquid phase through liquid phase sintering, while tungsten powder dissolves and diffuses into the liquid phase, achieving the highest solubility of tungsten in the liquid phase, thus playing a role in solid solution strengthening and enhancing the bonding between the binder phase and the tungsten powder.

[0048] In this invention, when the sintering temperature is below the above range or the sintering time is too short, the binder phase will not wet or will wet poorly, resulting in weak bonding between the two phases and making it easy to become a crack source. When the sintering temperature is above the above range or the sintering time is too long, tungsten grains will aggregate and grow, resulting in uneven tungsten grain size and uneven distribution of the binder phase in the alloy, which will easily reduce the plasticity and toughness of the alloy.

[0049] After obtaining the sintered billet, the present invention performs cyclic vacuum heat treatment on the sintered billet to obtain the high-strength, high-toughness, high-density tungsten alloy material.

[0050] In this invention, the cyclic vacuum heat treatment includes: heating the sintered billet to 900-1200°C under vacuum conditions for a first holding time of 2-4 hours, and then cooling it to room temperature (15-30°C); heating the cooled billet to 700-900°C under vacuum conditions for a second holding time of 2-4 hours, and then cooling it to room temperature.

[0051] In a specific embodiment, heating the sintered billet to 900–1200°C under vacuum conditions and holding it therefor 2–4 hours can be performed by heating the sintered billet to 900°C, 950°C, 1000°C, 1100°C, 1150°C, or 1200°C under vacuum conditions and holding it therefor 2 hours, 2.5 hours, 3 hours, 3.5 hours, or 4 hours. In this invention, the first heating rate is preferably 10–30°C / min, and in a specific embodiment, it can be 10, 15, 20, 25, or 30°C / min. In this invention, the first cooling is preferably furnace cooling.

[0052] In a specific embodiment, the process of heating the billet cooled to room temperature to 700-900°C under vacuum conditions and holding it at that temperature for 2-4 hours can be: heating the billet cooled to room temperature to 700°C, 750°C, 800°C, 850°C or 900°C under vacuum conditions and holding it at that temperature for 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours.

[0053] In this invention, the second heating rate is preferably 10-30°C / min, and in specific embodiments it can be 10, 15, 20, 25, or 30°C / min. In this invention, the second cooling is preferably furnace cooling.

[0054] In this invention, the vacuum degree of the cyclic vacuum heat treatment is preferably not less than 5.0 × 10⁻⁶. -2 Pa.

[0055] This invention uses cyclic vacuum heat treatment to precipitate tungsten, achieving precipitation strengthening. It can control the size and distribution of tungsten grains, as well as the morphology, size, and distribution of the precipitated phase, avoiding the precipitation of brittle intermetallic compounds. At the same time, it inhibits the accumulation of impurity elements and compositional segregation at the interface between tungsten and the binder phase, resulting in a cleaner phase interface and more uniform material composition. It also eliminates residual hydrogen after liquid-phase sintering and eliminates or partially eliminates residual stress, which plays an important role in improving the stability of the composition of liquid-phase sintered materials, thereby improving the overall mechanical properties of the product.

[0056] This invention provides a high-strength, high-toughness, high-density tungsten alloy material prepared by the aforementioned method. This high-strength, high-toughness, high-density tungsten alloy material exhibits a tensile strength ≥1150 MPa, elongation ≥25%, and impact toughness ≥130 J / cm² at room temperature. 2 In a specific embodiment, the high-strength, high-toughness, high-density tungsten alloy material has a tensile strength of 1150 MPa, 1190 MPa, or 1200 MPa at room temperature, an elongation of 25% or 30%, and an impact toughness of 130 J / cm². 2 180J / cm 2 Or 260J / cm 2 .

[0057] The following detailed description of the high-strength, high-toughness, high-density tungsten alloy material and its preparation method provided by the present invention, with reference to specific embodiments, should not be construed as limiting the scope of protection of the present invention.

[0058] Example 1

[0059] (1) Mechanical ball milling modification of raw materials

[0060] Tungsten powder (average particle size 5 μm), nickel powder (average particle size 5 μm), iron powder (average particle size 5 μm), cobalt powder (average particle size 5 μm), and lanthanum powder (average particle size 5 μm) were mixed in a mass ratio of 91:7:1.0:0.6:0.4 to form a mixed powder. This powder was then mechanically ball-milled in a high-energy stirred ball mill. High-purity argon gas (99.9% purity) was used as a protective gas during ball milling, and 1.5 wt% anhydrous ethanol was added as a process control agent. Pure tungsten balls with a diameter of 8 mm were used, with a ball-to-powder ratio (mass ratio) of 25:1. The ball mill speed was controlled at 550 rpm, and the milling time was 5 hours. This yielded refined tungsten powder with an average particle size of submicron (see...). Figure 1 ) and nickel-based supersaturated solid solutions (see Figure 2 and Figure 3 Homogeneous modified composite powder (see) Figure 4The yield was approximately 95.6%. The ball-milled tungsten particles were significantly refined, with an average size reaching the submicron level (approximately 500 nm). The powder particle size was within the ultrafine particle size range, with an average grain size of 14 nm. The ball-milled nickel and iron powders not only had their microstructure refined but also formed entirely nanocrystalline nickel-based supersaturated solid solutions, with a particle size of approximately 0.2 μm and an average grain size of approximately 8 nm. Note: This invention involves extracting homogeneous modified composite powder to obtain refined tungsten powder and nickel-based supersaturated solid solutions for separate observation. Figures 1 to 3 .

[0061] (2) Cold isostatic pressing and liquid phase sintering

[0062] The homogeneous modified composite powder prepared above was placed in a rubber sleeve with a wall thickness of about 4 mm, and then placed in a 200 MPa ultra-high pressure chamber for cold isostatic pressing for 30 s to obtain a cold-pressed billet with a relative density of 75%, which is rod-shaped. Subsequently, the above cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1475 °C for 60 min to obtain a sintered billet with a relative density of about 99.0%. The average size of the tungsten particles in the sintered billet is less than 25 μm, and they are spherically distributed in the binder phase, and the distribution of the binder phase is also relatively uniform.

[0063] (3) Cyclic vacuum heat treatment

[0064] After placing the sintered billet in a vacuum sintering heat treatment furnace, the billet is first heated to 900°C at a heating rate of 10°C / min, held at that temperature for 2 hours, and then cooled to room temperature. The billet, cooled to room temperature, is then second heated to 700°C under vacuum conditions at a heating rate of 10°C / min, held at that temperature for 2 hours, and then cooled to room temperature again to obtain a high-strength, high-toughness, high-density tungsten alloy material (see...). Figure 5 ).

[0065] Testing revealed that the high-strength, high-toughness, high-density tungsten alloy rod prepared above exhibited a room-temperature tensile strength of 1150 MPa, an elongation of 30%, and an impact toughness of 260 J / cm². 2 .Depend on Figure 5 It can be seen that the high-strength, high-toughness, high-density tungsten alloy material prepared by the present invention has a fine and uniform microstructure and no component segregation.

[0066] Note: In this invention, the tensile test was conducted in accordance with GB / T 228.1-2021 to obtain tensile strength and elongation data; the impact test was conducted in accordance with GB / T 229-2020 to obtain impact toughness data.

[0067] Comparative Example 1

[0068] The only difference from Example 1 is that step (3) is replaced with:

[0069] After placing the sintered billet in a vacuum sintering heat treatment furnace, the sintered billet is heated to 900°C at a heating rate of 10°C / min, held at that temperature for 2 hours, and then cooled to room temperature to obtain tungsten alloy rods.

[0070] Testing showed that the tungsten alloy rod prepared in Comparative Example 1 had a room temperature tensile strength of 920 MPa, an elongation of 13%, and an impact toughness of 60 J / cm. 2 This demonstrates that the cyclic vacuum heat treatment employed in this invention has a significant impact on improving the strength and toughness of tungsten alloys.

[0071] Example 2

[0072] (1) Mechanical ball milling modification of raw materials

[0073] Tungsten powder (average particle size 8 μm), nickel powder (average particle size 8 μm), iron powder (average particle size 8 μm), cobalt powder (average particle size 8 μm), and lanthanum powder (average particle size 8 μm) were mixed in a mass ratio of 92:6:1.3:0.4:0.3 to form a mixed powder. This powder was then mechanically ball-milled in a high-energy stirred ball mill. High-purity argon gas (99.9% purity) was used as a protective gas during the ball milling process, and 1.5 wt% anhydrous ethanol was added as a process agent. The grinding media used were pure tungsten balls with a diameter of 8 mm, a ball-to-material ratio (mass ratio) of 15:1, and a ball mill speed of 350 rpm for 10 hours. This resulted in a homogeneous modified composite powder of refined tungsten powder and nickel-based supersaturated solid solution with an average size of submicron, achieving a powder yield of approximately 97.2%. The ball-milled tungsten particles were significantly refined, with an average size of approximately 1.5 μm (submicron level) and an average grain size of approximately 14 nm. The ball-milled nickel and iron powders were completely transformed into nanocrystalline nickel-based supersaturated solid solution with a particle size of approximately 1.2 μm and an average grain size of approximately 40 nm.

[0074] (2) Cold isostatic pressing and liquid phase sintering

[0075] The homogeneous modified composite powder prepared above was placed in a rubber sleeve with a wall thickness of about 4 mm, and then placed in a 290 MPa ultra-high pressure chamber for cold isostatic pressing for 40 s to obtain a cold-pressed blank with a relative density of 80%. Subsequently, the above cold-pressed blank was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1495 °C for 95 min to obtain a sintered blank with a relative density of about 99.5%. The average size of the tungsten particles in the sintered blank was less than 25 μm, and they were spherically distributed in the binder phase, and the distribution of the binder phase was also relatively uniform.

[0076] (3) Cyclic vacuum heat treatment

[0077] After placing the sintered billet in a vacuum sintering heat treatment furnace, the sintered billet is first heated to 1000°C at a heating rate of 10°C / min, held at that temperature for 2 hours, and then cooled to room temperature. The billet cooled to room temperature is then heated to 800°C at a heating rate of 10°C / min under vacuum conditions for a second time and held at that temperature for 3 hours, and then cooled to room temperature for a second time to obtain a high-strength, high-toughness, high-density tungsten alloy rod.

[0078] Testing revealed that the high-strength, high-toughness, high-density tungsten alloy rods prepared above exhibited a room-temperature tensile strength of 1190 MPa, an elongation of 25%, and an impact toughness of 180 J / cm². 2 .

[0079] Comparative Example 2

[0080] The only difference from Example 1 is that step (3) is replaced with:

[0081] After placing the sintered billet in a vacuum sintering heat treatment furnace, the sintered billet is heated to 1000°C at a heating rate of 10°C / min, held at that temperature for 2 hours, and then cooled to room temperature to obtain tungsten alloy rods.

[0082] Testing showed that the tungsten alloy rod prepared in Comparative Example 2 had a room temperature tensile strength of 950 MPa, an elongation of 11%, and an impact toughness of 50 J / cm. 2 .

[0083] Example 3

[0084] (1) Mechanical ball milling modification of raw materials

[0085] Tungsten powder (average particle size 10 μm), nickel powder (average particle size 10 μm), iron powder (average particle size 10 μm), cobalt powder (average particle size 10 μm), and lanthanum powder (average particle size 10 μm) were mixed in a mass ratio of 93:4.9:1.4:0.5:0.2 to form a mixed powder. This powder was then mechanically ball-milled in a high-energy stirred ball mill. High-purity argon gas (99.9% purity) was used as a protective gas during the ball milling process, and 1.5 wt% of [unspecified ingredient] was added. Anhydrous ethanol was used as the process control agent. Pure tungsten balls with a diameter of 8 mm were selected for milling, with a ball-to-material ratio (mass ratio) of 25:1. The ball mill speed was controlled at 200 rpm, and the milling time was 15 hours. This yielded a homogeneous modified composite powder of tungsten powder and nickel-based supersaturated solid solution with an average size of submicron. The powder yield was approximately 99.6%. The average size of the ball-milled tungsten particles was 1000 nm, and the average grain size was approximately 100 nm. The ball-milled nickel and iron powders had all formed nanocrystalline nickel-based supersaturated solid solution with a particle size of approximately 2 μm and an average grain size of approximately 100 nm.

[0086] (2) Cold isostatic pressing and liquid phase sintering

[0087] The homogeneous modified composite powder prepared above was placed in a rubber sleeve with a wall thickness of about 4 mm, and then placed in a 350 MPa ultra-high pressure chamber for cold isostatic pressing for 50 s to obtain a cold-pressed blank with a relative density of 85%; subsequently, the above cold-pressed blank was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1510 °C for 130 min to obtain a liquid-phase sintered blank with a relative density of about 99.9%.

[0088] (3) Cyclic vacuum heat treatment

[0089] After placing the sintered billet in a vacuum sintering heat treatment furnace, the sintered billet is first heated to 1200°C at a heating rate of 10°C / min, held at that temperature for 4 hours, and then cooled to room temperature. The billet cooled to room temperature is then heated to 900°C at a heating rate of 10°C / min under vacuum conditions for a second time, held at that temperature for 4 hours, and then cooled to room temperature for a second time to obtain a high-strength and high-toughness tungsten alloy rod.

[0090] Testing revealed that the high-strength and high-toughness tungsten alloy rod prepared above exhibited a room temperature tensile strength of 1200 MPa, an elongation of 25%, and an impact toughness of 130 J / cm². 2 .

[0091] Comparative Example 3

[0092] (1) The steps are the same, (2) The steps are as follows:

[0093] The homogeneous modified composite powder prepared above was placed in a rubber sleeve with a wall thickness of about 4 mm, and then placed in a 350 MPa ultra-high pressure chamber for cold isostatic pressing to obtain a cold-pressed billet with a relative density of about 85%. Subsequently, the cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and sintered in the liquid phase at 1470 °C for 120 min to obtain a liquid phase sintered billet with a relative density of about 98.6%.

[0094] Testing revealed that the high-density tungsten alloy rod prepared above exhibited a room-temperature tensile strength of 910 MPa, an elongation of 7%, and an impact toughness of 55 J / cm². 2 .

[0095] As can be seen from the above embodiments, the present invention provides a high-strength, high-toughness, high-density tungsten alloy material and its preparation method, which solves the technical problems of coarse microstructure, compositional segregation, low tensile strength, elongation, and impact toughness of sintered tungsten alloy materials in the prior art.

[0096] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness, high-density tungsten alloy material, characterized in that, Includes the following steps: The raw material powder is mechanically ball-milled to obtain a homogeneous modified composite powder; the raw material powder is tungsten powder, nickel powder, iron powder, cobalt powder, and lanthanum powder; by mass percentage, the raw material powder contains 90-93% tungsten powder, 4.9-7% nickel powder, 1.0-1.4% iron powder, 0.3-1.2% cobalt powder, and 0.2-0.4% lanthanum powder; the homogeneous modified composite powder comprises refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution; The homogeneous modified composite powder is subjected to cold isostatic pressing to obtain a cold-pressed blank; The cold-pressed billet is subjected to liquid-phase sintering to obtain a sintered billet; the liquid-phase sintering temperature is 1475-1530℃, and the holding time is 60-130min. The sintered billet is subjected to cyclic vacuum heat treatment to obtain the high-strength, high-toughness, high-density tungsten alloy material; The cyclic vacuum heat treatment includes: heating the sintered billet to 900-1200°C under vacuum conditions for a first holding time of 2-4 hours, and then cooling it to room temperature; heating the billet cooled to room temperature to 700-900°C under vacuum conditions for a second holding time of 2-4 hours, and then cooling it to room temperature.

2. The preparation method according to claim 1, characterized in that, A process control agent is added during the mechanical ball milling process; the mass of the process control agent is 0.5-2% of the total mass of the raw material powder; the process control agent is anhydrous ethanol and / or zinc stearate.

3. The preparation method according to claim 1, characterized in that, The conditions for the mechanical ball milling include: a ball-to-material ratio of (5-25):1, a ball milling speed of 200-550 r / min, and a ball milling time of 5-15 h; the mechanical ball milling is carried out under a protective atmosphere.

4. The preparation method according to any one of claims 1 to 3, characterized in that, The refined tungsten powder has an average particle size of 500 nm to 5 μm and an average grain size of 14 to 100 nm; the nanocrystalline nickel-based supersaturated solid solution has an average particle size of 0.2 to 2 μm and an average grain size of 8 to 100 nm.

5. The preparation method according to claim 1, characterized in that, The pressure of the cold isostatic pressing is 200-350 MPa, and the time of the cold isostatic pressing is 20-60 s; the relative density of the cold-pressed billet is 75-85%.

6. The preparation method according to claim 1, characterized in that, The liquid phase sintering is carried out under a protective atmosphere.

7. The preparation method according to claim 1 or 6, characterized in that, The relative density of the sintered billet is 99.0% to 99.9%.

8. The preparation method according to claim 1, characterized in that, The rates of the first and second heating are independently 10–30 °C / min.

9. The preparation method according to claim 1, characterized in that, The vacuum degree of the cyclic vacuum heat treatment shall not be less than 5.0 × 10⁻⁶. -2 Pa.

10. The high-strength, high-toughness, high-density tungsten alloy material prepared by the preparation method according to any one of claims 1 to 9, characterized in that, The high-strength, high-toughness, high-density tungsten alloy material exhibits a tensile strength ≥1150 MPa, elongation ≥25%, and impact toughness ≥130 J / cm² at room temperature. 2 .

Images