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

Abstract

The invention relates to the technical field of metallurgy, in particular to a high-toughness and high-density tungsten alloy material and a preparation method thereof. The preparation method of the high-toughness and high-density tungsten alloy material comprises the following steps that raw material powder is subjected to mechanical ball milling, and homogeneous modified composite powder is obtained; the raw material powder is tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder; the homogeneous modified composite powder comprises refined tungsten powder and a nanocrystalline nickel-based supersaturated solid solution; performing cold isostatic pressing on the homogenized modified composite powder to obtain a cold-pressed blank; the cold-pressed blank is subjected to liquid-phase sintering, and a sintered blank is obtained; the temperature of the liquid phase sintering is 1475 to 1530 DEG C, and the heat preservation time is 60 to 130 minutes; and the sintered blank is subjected to circulating vacuum heat treatment, and the high-toughness and high-density tungsten alloy material is obtained. According to the prepared tungsten alloy material, the strength is greatly improved, and meanwhile high plasticity and toughness can still be kept.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a high-strength, high-toughness, high-density tungsten alloy material and a preparation method thereof. Background Art

[0002] High-density tungsten alloy is a kind of alloy with tungsten as the matrix material (tungsten content is 80-97%) and appropriate additions of elements such as Ni, Cu, Fe, Co, Mo, Cr, etc. Because it overcomes the brittleness of tungsten and maintains the excellent properties of tungsten such as high melting point, high density, and low expansion coefficient, it has been widely used in aerospace, military, civilian industry and other industries.

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

[0004] In view of this, the purpose of the present invention is to provide a high-strength, high-toughness, high-density tungsten alloy material and a preparation method thereof. The tungsten alloy material prepared by the present invention can significantly improve the strength while still maintaining high plasticity and toughness.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

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

[0007] Mechanically ball-milling the raw material powder to obtain a homogeneous modified composite powder; the raw material powder comprises tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder; the raw material powder comprises 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 in terms of mass percentage; the homogeneous modified composite powder comprises refined tungsten powder and a nanocrystalline nickel-based supersaturated solid solution;

[0008] cold isostatic pressing the homogeneous modified composite powder to obtain a cold pressed blank;

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

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

[0011] The cyclic vacuum heat treatment includes: first heating the sintered blank to 900-1200° C. under vacuum conditions, keeping the temperature for 2-4 hours, and then cooling it to room temperature; second heating the blank cooled to room temperature to 700-900° C. under vacuum conditions, keeping the temperature for 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; and the process control agent is anhydrous ethanol and / or zinc stearate.

[0013] Preferably, 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; and 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 blank is 75-85%.

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

[0017] Preferably, the relative density of the sintered blank is 99.0-99.9%.

[0018] Preferably, the first heating rate and the second heating rate are independently 10-30°C / min.

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

[0020] The present invention provides a high-strength, toughness, and high-density tungsten alloy material prepared by the preparation method described in the above scheme. The high-strength, toughness, and high-density tungsten alloy material has a tensile strength of ≥1150MPa, an elongation of ≥25%, and an impact toughness of ≥130J / cm at room temperature. 2 .

[0021] The present invention fully mixes tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder through mechanical ball milling, and realizes partial dissolution of tungsten into nickel-based solid solution at the same time, so as to obtain a homogeneous modified composite powder with uniform two-phase distribution, i.e., refined tungsten powder and nanocrystalline nickel-based supersaturated solid solution (referring to tungsten being in a saturated state at low temperature, which is subsequently used as a bonding phase), and then liquid phase sintering is performed to convert the nickel-based solid solution into a liquid phase to infiltrate the tungsten powder, thereby enhancing the bonding between the bonding phase and tungsten. During liquid phase sintering, the tungsten powder is further dissolved and diffused. Since part of the tungsten has been dissolved in the early mechanical ball milling, the solubility of tungsten is greatly increased, which plays a role in solid solution strengthening, and due to the mechanical ball milling The refinement of tungsten powder can effectively inhibit the growth of tungsten particles during liquid phase sintering, inhibit component segregation, and can achieve high density through short-term sintering at relatively low temperature. The tungsten grains are small and the fine grain strengthening is obvious, which makes the comprehensive mechanical properties of the tungsten alloy material high. Through subsequent cyclic vacuum heat treatment, tungsten precipitation strengthening is achieved, eliminating the negative impact of hydrogen embrittlement on the alloy performance, further improving the wettability of the binder phase to the W particles, which is conducive to obtaining a microstructure with uniform distribution of organization and composition, and improving the interface strength between the W phase and the binder phase, effectively improving the comprehensive performance of the high-density tungsten alloy material to meet the application requirements under special environments.

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

[0023] In addition, the liquid phase sintering temperature of the present invention is low during the period of time, and has the advantage of low energy consumption. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a macroscopic photograph of the refined tungsten powder in Example 1;

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

[0026] Figure 3 This is a transmission electron microscope photograph of the nickel-based supersaturated solid solution of Example 1;

[0027] Figure 4 This is the macroscopic morphology of the homogeneous modified composite powder of Example 1;

[0028] Figure 5 This is the organizational diagram of the high-density tungsten alloy material in Example 1. DETAILED DESCRIPTION

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

[0030] Mechanically ball-milling the raw material powder to obtain a homogeneous modified composite powder; the raw material powder comprises tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder; the raw material powder comprises 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 in terms of mass percentage; the homogeneous modified composite powder comprises refined tungsten powder and a nanocrystalline nickel-based supersaturated solid solution;

[0031] cold isostatic pressing the homogeneous modified composite powder to obtain a cold pressed blank;

[0032] performing liquid phase sintering on the cold pressed blank to obtain a sintered blank;

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

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

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

[0036] The present invention subjects raw material powder to mechanical ball milling to obtain homogeneous modified composite powder.

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

[0038] In the present invention, the content of tungsten powder in the raw material powder is 90-93% by mass, and in specific embodiments, it can be 90%, 91%, 92% or 93%; the content of nickel powder 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 content of iron powder 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 content of cobalt powder 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 content of lanthanum powder 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 the present invention, the rotation speed of the mechanical ball mill is preferably 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 mechanical ball milling time is preferably 5-15 hours, and in specific embodiments, it can be 5 hours, 8 hours, 10 hours, 12 hours, or 15 hours. The ball-to-material ratio of the mechanical ball milling is preferably (5-25):1, and in specific embodiments, it can be 5:1, 10:1, 15:1, 20:1, or 25:1. The mechanical ball milling is preferably carried out under a protective atmosphere, and the protective gas providing the protective atmosphere is preferably high-purity argon (purity ≥99.99%) or nitrogen (purity ≥99.99%). The mechanical ball milling performed under a protective atmosphere in the present invention can prevent the powder from being oxidized during the ball milling process. The present invention has no special requirements for the equipment used for the mechanical ball milling, and any ball milling equipment known in the art can be used, such as a stirred high-energy ball mill. The present invention has no special requirements on the grinding ball material used in the mechanical ball milling, and any grinding ball material known in the art can be used. In the embodiment of the present invention, pure tungsten balls with a diameter of 8 mm are specifically used to avoid the introduction of impurities during mechanical ball milling.

[0040] In the present 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 the process control agent added is preferably 0.5-2% of the total mass of the raw material powder. In the present invention, the addition of an appropriate process control agent can significantly increase the powder yield during mechanical ball milling and facilitate uniform powder mixing and industrial production.

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

[0042] In the present 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 the tungsten particles from growing during subsequent liquid phase sintering, thereby refining the grains and improving the comprehensive mechanical properties of the sintered material.

[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 blank.

[0044] In the present invention, the cold isostatic pressing pressure is preferably 200-350 MPa, and in specific embodiments, it can be 200 MPa, 250 MPa, 290 MPa, 300 MPa, or 350 MPa; the cold isostatic pressing time is preferably 20-60 seconds, and in specific embodiments, it can be 20 seconds, 30 seconds, 40 seconds, 50 seconds, or 60 seconds. Under this pressure, the present invention can obtain a cold-pressed blank with a higher density, more uniform density distribution, and porosity, which is conducive to the liquid phase uniformly filling the pores in the subsequent liquid phase sintering process, thereby not easily causing composition segregation. In the present invention, the relative density of the cold-pressed blank is preferably 75-85%, and in specific embodiments, it can be 75%, 77%, 80%, 81%, 83%, or 85%.

[0045] The present invention preferably places the homogeneous modified composite powder into a rubber sleeve for cold isostatic pressing. The present invention has no special requirements for the thickness of the rubber sleeve, and a thickness well known in the art can be used, which is 4 mm in a specific embodiment. In the present invention, the cold pressed blank is preferably a bar stock.

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

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

[0048] In the present invention, when the sintering temperature is lower than the above range or the sintering time is too short, the bonding phase will not wet or wet the tungsten phase poorly, resulting in weak interface bonding between the two phases, which can easily become a source of cracks; and when the sintering temperature is higher than the above range or the sintering time is too long, tungsten grains will aggregate and grow, and the tungsten particles will be uneven in size and the bonding phase will be unevenly distributed in the alloy, which can easily reduce the plasticity and toughness of the alloy.

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

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

[0051] In a specific embodiment, the first heating of the sintered blank to 900-1200°C under vacuum conditions and the first holding temperature for 2-4 hours can be: the first heating of the sintered blank to 900°C, 950°C, 1000°C, 1100°C, 1150°C or 1200°C under vacuum conditions and the first holding temperature for 2 hours, 2.5 hours, 3 hours, 3.5 hours or 4 hours. In the present invention, the first heating rate is preferably 10-30°C / min, and in specific embodiments, it can be 10, 15, 20, 25 or 30°C / min. In the present invention, the first cooling is preferably furnace cooling.

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

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

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

[0055] The present invention precipitates tungsten elements through cyclic vacuum heat treatment, which plays a role of precipitation strengthening. It can control the size and distribution of tungsten grains and the morphology, size and distribution of precipitated phases, avoid the precipitation of brittle intermetallic compounds, and simultaneously inhibit the aggregation and component segregation of impurity elements on the interface of tungsten and bonding phases, thereby obtaining a cleaner phase interface and uniformity of material composition; eliminate residual hydrogen elements after liquid phase sintering, and eliminate or partially eliminate residual stress, which plays an important role in improving the stability of liquid phase sintered material components, thereby improving the comprehensive mechanical properties of the product.

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

[0057] The high-strength, toughness, and high-density tungsten alloy material and its preparation method provided by the present invention are described in detail below with reference to the embodiments, but they 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 of 5 μm), nickel powder (average particle size of 5 μm), iron powder (average particle size of 5 μm), cobalt powder (average particle size of 5 μm) and lanthanum powder (average particle size of 5 μm) were prepared into a mixed powder in a mass ratio of 91:7:1.0:0.6:0.4, and then placed in a high-energy stirring ball mill for mechanical ball milling. During the ball milling, high-purity argon with a purity of 99.9% was used as the protective gas, and 1.5wt% of anhydrous ethanol was added as a process control agent. Pure tungsten balls were used for grinding, with a diameter of 8 mm and a ball-to-material ratio (mass ratio) of 25:1. The ball mill speed was controlled at 550 rpm and the ball milling time was 5 h. At this time, refined tungsten powder with an average size of submicron was obtained (see Figure 1 ) and nickel-based supersaturated solid solution (see Figure 2 and Figure 3 ) of homogeneous modified composite powder (see Figure 4), the powder yield is about 95.6%, the tungsten particles modified by ball milling are significantly refined, the average size has reached the submicron level, about 500nm, the powder particle size is already in the ultrafine particle size range, and the average grain size reaches 14nm. The microstructure of the nickel and iron powders modified by ball milling has not only been refined, but also all formed nanocrystalline nickel-based supersaturated solid solution, the particle size of which is about 0.2μm and the average grain size is about 8nm. Note: The present invention extracts the homogeneous modified composite powder to obtain refined tungsten powder and nickel-based supersaturated solid solution, and observes them separately to obtain 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 seconds to obtain a cold-pressed billet with a relative density of 75%, which is in the shape of a rod; subsequently, the above-mentioned cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1475°C for 60 minutes 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 binding phase, and the distribution of the binding phase is also relatively uniform.

[0063] (3) Cyclic vacuum heat treatment

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

[0065] After testing, the room temperature tensile strength of the high-strength, high-density tungsten alloy rod prepared above reached 1150MPa, the elongation reached 30%, and the impact toughness reached 260J / cm 2 .Depend on Figure 5 It can be seen that the high-strength, toughness, and high-density tungsten alloy material prepared by the present invention has a fine and uniform structure without any component segregation.

[0066] Note: In the present invention, the tensile test refers to GB / T 228.1-2021 to obtain the tensile strength and elongation data; the impact test refers to GB / T 229-2020 to obtain the impact toughness data.

[0067] Comparative Example 1

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

[0069] The sintered blank was placed in a vacuum sintering heat treatment furnace, and the temperature of the sintered blank was raised to 900° C. at a heating rate of 10° C. / min. After being kept at this temperature for 2 hours, the blank was cooled to room temperature to obtain a tungsten alloy rod.

[0070] After testing, the room temperature tensile strength of the tungsten alloy rod prepared in Comparative Example 1 is 920 MPa, the elongation is 13%, and the impact toughness is 60 J / cm 2 It is shown that the cyclic vacuum heat treatment adopted in the present invention has an important influence on improving the strength and toughness of tungsten alloy.

[0071] Example 2

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

[0073] Tungsten powder (average particle size of 8 μm), nickel powder (average particle size of 8 μm), iron powder (average particle size of 8 μm), cobalt powder (average particle size of 8 μm) and lanthanum powder (average particle size of 8 μm) were prepared into a mixed powder in a mass ratio of 92:6:1.3:0.4:0.3, and then placed in a high-energy stirring ball mill for mechanical ball milling. During the ball milling, high-purity argon with a purity of 99.9% was used as the protective gas, and 1.5wt% of anhydrous ethanol was added as the process The control agent and grinding balls were pure tungsten balls with a diameter of 8 mm and a ball-to-material ratio (mass ratio) of 15:1. The ball mill speed was controlled at 350 rpm and the ball milling time was 10 hours. At this time, a homogeneous modified composite powder of refined tungsten powder with an average size of submicron and a nickel-based supersaturated solid solution was produced, with a powder yield of approximately 97.2%. The tungsten particles modified by ball milling were significantly refined, with an average size of approximately 1.5 μm and an average grain size of approximately 14 nm. The nickel and iron powders modified by ball milling had all formed a 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 seconds to obtain a cold-pressed billet with a relative density of 80%; subsequently, the above-mentioned cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1495°C for 95 minutes to obtain a sintered billet with a relative density of about 99.5%. The average size of the tungsten particles in the sintered billet was less than 25 μm, and they were spherically distributed in the binding phase, and the distribution of the binding phase was also relatively uniform.

[0076] (3) Cyclic vacuum heat treatment

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

[0078] After testing, the room temperature tensile strength of the high-strength, high-density tungsten alloy rod prepared above reached 1190MPa, the elongation reached 25%, and the impact toughness reached 180J / cm 2 .

[0079] Comparative Example 2

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

[0081] The sintered blank was placed in a vacuum sintering heat treatment furnace, and the temperature of the sintered blank was raised to 1000° C. at a heating rate of 10° C. / min, and the blank was kept at this temperature for 2 h and then cooled to room temperature to obtain a tungsten alloy rod.

[0082] After testing, the room temperature tensile strength of the tungsten alloy rod prepared in Comparative Example 2 is 950 MPa, the elongation is 11%, and the impact toughness is 50 J / cm 2 .

[0083] Example 3

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

[0085] Tungsten powder (average particle size of 10 μm), nickel powder (average particle size of 10 μm), iron powder (average particle size of 10 μm), cobalt powder (average particle size of 10 μm) and lanthanum powder (average particle size of 10 μm) were prepared into a mixed powder in a mass ratio of 93:4.9:1.4:0.5:0.2, and then placed in a high-energy stirring ball mill for mechanical ball milling. During the ball milling, high-purity argon with a purity of 99.9% was used as the protective gas, and 1.5wt% of argon was added. % anhydrous ethanol was used as a process control agent, pure tungsten balls with a diameter of 8 mm and a ball-to-material ratio (mass ratio) of 25:1 were used, and the ball mill speed was controlled at 200 rpm. The milling time was 15 hours. A homogeneous modified composite powder of modified tungsten powder with an average submicron size and a nickel-based supersaturated solid solution was obtained at this time. The powder yield was approximately 99.6%. The average size of the ball-milled modified tungsten particles was 1000 nm, and the average tungsten grain size reached approximately 100 nm. The ball-milled modified nickel and iron powders had completely formed a 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 seconds to obtain a cold-pressed billet with a relative density of 85%; subsequently, the above-mentioned cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1510°C for 130 minutes to obtain a liquid-phase sintered billet with a relative density of about 99.9%.

[0088] (3) Cyclic vacuum heat treatment

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

[0090] After testing, the room temperature tensile strength of the high-strength and tough tungsten alloy rod prepared above reached 1200MPa, the elongation reached 25%, and the impact toughness reached 130J / cm 2 .

[0091] Comparative Example 3

[0092] (1) The steps are the same, and (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 approximately 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 approximately 85%. Subsequently, the cold-pressed billet was placed in a hydrogen protective atmosphere sintering furnace and liquid-phase sintered at 1470°C for 120 minutes to obtain a liquid-phase sintered billet with a relative density of approximately 98.6%.

[0094] The test results show that the room temperature tensile strength of the high density tungsten alloy rod prepared above is 910MPa, the elongation is 7%, and the impact toughness is 55J / cm 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 a preparation method thereof, which solves the technical problems in the prior art such as coarse microstructure and component segregation of sintered tungsten alloy materials, and low tensile strength, elongation, and impact toughness of the alloy materials.

[0096] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing a high-strength, high-toughness and high-density tungsten alloy material, characterized in that: The following steps are involved: Mechanically ball-milling the raw material powder to obtain a homogeneous modified composite powder; the raw material powder comprises tungsten powder, nickel powder, iron powder, cobalt powder and lanthanum powder; the raw material powder comprises 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 in terms of mass percentage; the homogeneous modified composite powder comprises refined tungsten powder and a nanocrystalline nickel-based supersaturated solid solution; cold isostatic pressing the homogeneous modified composite powder to obtain a cold pressed blank; The cold pressed blank is subjected to liquid phase sintering to obtain a sintered blank; the liquid phase sintering temperature is 1475-1530° C., and the holding time is 60-130 minutes; The sintered blank is subjected to cyclic vacuum heat treatment to obtain the high-strength, high-toughness and high-density tungsten alloy material; The cyclic vacuum heat treatment includes: first heating the sintered blank to 900-1200° C. under vacuum conditions, keeping the temperature for 2-4 hours, and then cooling it to room temperature; second heating the blank cooled to room temperature to 700-900° C. under vacuum conditions, keeping the temperature for 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; the mass of the process control agent is 0.5-2% of the total mass of the raw material powder; and 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; and 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 average particle size of the refined tungsten powder is 500nm-5μm, and the average grain size is 14-100nm; the average particle size of the nanocrystalline nickel-based supersaturated solid solution is 0.2-2μm, and the average grain size is 8-100nm.

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

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

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

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

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

10. The high-strength, toughness, and 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-density tungsten alloy material has a tensile strength of ≥1150MPa, an elongation of ≥25%, and an impact toughness of ≥130J / cm at room temperature. 2 .

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