High-density tungsten alloy and preparation method thereof

Abstract

The invention relates to the technical field of tungsten alloy materials, in particular to a high-density tungsten alloy which is composed of, by mass fraction, 90-97% of tungsten and the balance nickel and iron, the mass ratio of nickel to iron is (0.5-1.5): 1, and a preparation method of the high-density tungsten alloy is disclosed. According to the tungsten alloy material prepared through the preparation method, through multiple cycles of the two-stage heat treatment process, the alloy structure contains 20-40 [mu] m W crystal grains distributed in a bonding phase composed of a tungsten-nickel-iron solid solution, and also contains 10-800 nm ultra-fine W crystal grains which are uniformly distributed in the bonding phase; the nano-scale fine W crystal grains account for 2-15% of the volume percentage of the whole bonding phase, and due to the special organization structure, the alloy has the excellent performance of high strength, high toughness and the like, is particularly suitable for a new generation of armor-piercing bullet cores and has the excellent armor-piercing performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of tungsten alloy materials, in particular to a high-density tungsten alloy and a preparation method thereof. BACKGROUND

[0002] The high-density tungsten alloy has been widely used in many fields such as aerospace, machinery, nuclear industry, electronics and military industry due to its excellent properties such as high density, high strength and good plasticity, and is also one of the main materials for preparing kinetic energy armor-piercing bullet cores. With the progress of science and technology, the protection of various tanks, armored vehicles and warships is getting stronger and stronger, and accordingly the armor-piercing power of armor-piercing bullets is getting higher and higher, so higher requirements are put forward for the strength and toughness of the high-density tungsten alloy as the armor-piercing bullet core material.

[0003] The high-density tungsten alloy after sintering heat treatment, for example, 93W-4.9Ni-2.1Fe, usually has a tensile strength of less than 950 MPa and an impact toughness of less than 120 J / cm 2 Therefore, the strength and toughness of the tungsten alloy prepared by the traditional process method are still not ideal, and in order to meet the needs of the new generation of armor-piercing bullets in the national defense industry, it is necessary to develop high-density tungsten alloys with higher strength and toughness. For example, the patent with publication number CN117102475A provides a rapid low-temperature heat treatment method for a tungsten alloy material, which includes the following preparation steps: S1: rough blank preparation, alloy powder is weighed according to the designed alloy material, the alloy powder is mixed to obtain a mixture, the mixture is pressed into a rough blank using cold isostatic pressing technology; S2: rough blank sintering, the rough blank is sintered at a sintering temperature of 1400-1600 DEG C for 30-60 min to obtain a rough blank; S3: annealing, the rough blank is annealed in an electric resistance furnace at an annealing temperature of 550-850 DEG C for 1-3 h to obtain a tungsten alloy material. The method uses an electric resistance furnace to heat and hold the tungsten alloy at a high temperature after sintering to improve the tensile strength and elongation of the tungsten alloy material.

[0004] However, the existing high-density tungsten alloy and its preparation process as described above have not been fundamentally optimized and improved in the microstructure and morphology of the alloy, so that the improvement in the strength and toughness of the material in the macroscopic aspect is very limited, which cannot meet the higher strength and toughness requirements of the new generation of armor-piercing bullet core materials. SUMMARY

[0005] The present application aims to solve the problem of the insufficient strength and toughness of the existing high-density tungsten alloy, and provides a high-density tungsten alloy and a preparation method thereof. The high-density tungsten alloy of the present application has high strength and high toughness, and has excellent armor-piercing performance when applied to the core of the new generation of armor-piercing bullets.

[0006] The present application is realized by the following technical solutions: The present application provides a kind of high-density tungsten alloy, it is characterized in that, by the following element component composition by mass fraction: 90-97wt% tungsten, remainder nickel and iron, wherein nickel iron mass ratio is (0.5-1.5):1;Tungsten powder is 2-6 μm of Fisher particle size, nickel powder is 1-3 μm of Fisher particle size, and iron powder is 5-10 μm of Fisher particle size.

[0007] The present application also provides a kind of preparation method of the above high-density tungsten alloy, comprising the following steps: S1 ingredient: tungsten powder, nickel powder and iron powder are weighed by quantity; S2 ball milling: the raw materials obtained in step S1 are loaded into a ball mill, tungsten alloy balls with a diameter of Φ10 mm are used for ball milling to obtain a ball-mixed powder; S3 press forming: the ball-mixed powder is loaded into a mold, and cold isostatic pressing is used for press forming to obtain a tungsten alloy compact; S4 sintering: the tungsten alloy compact is placed in a sintering furnace, and sintering is carried out under hydrogen protection to obtain a tungsten alloy sintered compact; S5 heat treatment: the tungsten alloy sintered compact is placed in a heat treatment furnace, and multiple cycle heat treatment is carried out under argon protection, and argon is continuously introduced at a flow rate of 1.5-3.5 m 3 / h during the heat treatment, and finally water quenching and cooling are carried out to obtain a heat-treated tungsten alloy; Each heat treatment process includes a precipitation stage and a dissolution stage, the precipitation stage is treated at a temperature of 750-850℃ for 2-4h, and the dissolution stage is treated at a temperature of 1280-1380℃ for 3-5h; S6 rotary forging: the heat-treated tungsten alloy is subjected to rotary forging treatment using a four-hammer head radial rotary forging machine, and the preheating temperature is controlled to be 450-650℃, and the holding time is 30-60 min to obtain the high-density tungsten alloy. The microstructure of the high-density tungsten alloy includes W grains of 20-40 μm and extremely fine W grains of 10-800 nm, and the extremely fine W grains account for 2-15% of the total volume of the bonding phase.

[0008] In the above preparation method, as a preferred embodiment, in step S2, the ball-to-material mass ratio during ball milling is (1-2):1, the ball milling time is 20-24h, and the rotation speed of the ball mill is controlled to be 50-80 r / min, and argon is used as the protective gas.

[0009] In the above preparation method, as a preferred embodiment, in step S3, the pressing pressure is 150-220 MPa, and the holding time is 20-30 s.

[0010] In the above preparation method, as a preferred embodiment, in step S4, the sintering temperature is 1480-1540℃, the sintering holding time is 40-80min, and the hydrogen is continuously introduced at a flow rate of 1.5-3.5m 3 / h during sintering.

[0011] In the above preparation method, as a preferred embodiment, in step S5, the number of times of the multiple cycle heat treatment is 2-6 times.

[0012] In the above preparation method, as a preferred embodiment, in step S6, the total deformation amount of the rotary swaging process is 20-50% according to the sectional area reduction amount.

[0013] In the above high-density tungsten alloy, W, Ni and Fe three kinds of metal powders are used, and the mass ratio of nickel to iron is (0.5-1.5):1, while the mass ratio of nickel to iron in the industry for producing high-performance high-density tungsten alloy is generally controlled to be (2-4):1, because according to the currently disclosed technology and cognition in the field, it is believed that in the nickel-iron ratio range of (2-4):1, it is beneficial to form a face-centered cubic structure with good toughness of the bonding phase, and it is not easy to produce unstable intermetallic compound brittle phase. However, under the component condition of the nickel-iron ratio, the tungsten alloy organizational structure is composed of simple micron-sized tungsten grains and bonding phase, and there is no nano-sized fine W grain with strengthening effect distributed in the bonding phase, and the performance of the tungsten alloy product such as strength and toughness does not perform outstandingly. However, the present application adopts the nickel-iron mass ratio of (0.5-1.5):1, which has a lower nickel-iron mass ratio composition, which can make the alloy form intermetallic compound Fe2W during sintering, and then dissolve the intermetallic compound brittle phase produced in the process in the bonding phase in the heat treatment process, avoid the residual of the intermetallic compound brittle phase in the structure, and prepare the tungsten alloy with special structure of 10-800nm extremely fine tungsten particles uniformly distributed in the bonding phase. The nano-sized fine grains have a significant strengthening effect on the alloy, so that the alloy has excellent tensile strength and impact toughness.

[0014] In step S2 of the above preparation process, the tungsten alloy mixed powder is repeatedly crushed, impacted and broken by the grinding balls in the ball mill, which not only realizes the full and uniform mixing of the material, but also disperses the agglomerated particles of the powder while playing a pre-alloying role, greatly reducing the activation energy of the alloy powder and improving the sintering densification performance of the alloy powder.

[0015] In step S3 of the above preparation process, the pressing forming process ensures the strength of the green compact, avoiding defects such as edge and corner dropping, delamination and cracking.

[0016] In step S4 of the above preparation process, the sintering process uses reasonable sintering temperature and holding time, which is beneficial to the complete densification and uniformity of the tungsten alloy composition, and the Fe2W intermetallic compound is generated in the sintered alloy structure.

[0017] In step S5 of the above preparation process, in the first stage of heat treatment, due to the special nickel-iron ratio in the alloy composition, the intermetallic compound Fe2W formed in the sintering process and the supersaturated tungsten grains precipitate and separate out in the binder phase; in the second stage of heat treatment, the high temperature continuously dissolves the unstable intermetallic compound Fe2W brittle phase, and at the same time, the precipitated and separated fine tungsten grains are retained and distributed in the binder phase; with the continuous increase of the heat treatment cycle, the intermetallic compound Fe2W brittle phase continuously precipitates and dissolves, and the number of fine tungsten grains with nanometer size continuously increases, which can account for 2-15% of the volume percentage of the binder phase; after the last heat treatment cycle is completed and the holding is completed, water quenching is carried out to rapidly cool to room temperature, so as to prevent the Fe2W dissolved in the binder phase from re-precipitating and growing at the grain boundary, thereby avoiding the decrease of the alloy performance; if the heat treatment cycle is too few, such as only once, the number of precipitated fine tungsten grains is small, the strengthening effect is not obvious, and the effect of improving the performance of the tungsten alloy is not significant; on the contrary, if the heat treatment cycle is too many, such as more than 6 times, the number of precipitated fine tungsten grains continuously increases, and at the same time, the previously precipitated fine tungsten grains also gradually grow and become coarse, and the effect of improving the performance of the tungsten alloy gradually weakens.

[0018] In step S6 of the above preparation process, the rotary forging process ensures the uniform plastic deformation of the tungsten alloy rod, avoids the generation of defects such as cracks and phase changes in the alloy rod, and improves the tensile strength of the high-density tungsten alloy while maintaining excellent impact toughness.

[0019] The technical scheme of the present application has the following beneficial effects: (1) The high-density tungsten alloy composition provided by the present application uses W, Ni and Fe three kinds of metal powders, and the mass ratio of nickel to iron is (0.5-1.5):1; in the alloy structure, there are micron-sized spherical tungsten grains distributed in the binder phase, and 10-800 nm nanometer-sized fine tungsten grain precipitates uniformly distributed in the binder phase, accounting for 2-15% of the volume percentage of the binder phase; this fine grain structure has a significant strengthening effect on the binder phase, so that the alloy has excellent mechanical properties, the tensile strength is ≥1300 MPa, and the impact toughness is ≥100 J / cm 2 , which has a wide application in military industry, is suitable for rod-shaped kinetic energy armor-piercing ammunition with large length-diameter ratio, and has excellent armor-piercing performance.

[0020] (2) The method of the present application realizes the full and uniform mixing of different metal element materials by ball milling the tungsten alloy mixed powder, disperses the agglomerated particles of the powder, and plays a pre-alloying role, greatly reduces the activation energy of the alloy powder, improves the sintering densification performance of the alloy powder, helps to form a defect-free uniform structure in the sintering process, and greatly improves the bonding strength of the two-phase interface, thereby improving the comprehensive mechanical properties of the alloy.

[0021] (3) In the preparation method of the present application, the tungsten alloy is subjected to multiple two-stage heat treatments. In the first stage of heat treatment, due to the special nickel-iron ratio in the alloy composition, the intermetallic compound Fe2W and the supersaturated tungsten grains formed in the sintering process are precipitated, separated and grown in the adhesive phase. In the second stage of heat treatment, the high temperature continuously dissolves the unstable intermetallic compound Fe2W brittle phase separated in the first stage into the adhesive phase, while the fine tungsten grains precipitated and separated are retained and distributed in the adhesive phase. With the continuous increase of the number of heat treatment cycles, the intermetallic compound Fe2W brittle phase is continuously precipitated and dissolved, and the number of nanoscale size fine tungsten grains continuously precipitated and separated also continuously increases, eventually accounting for 2-15% of the volume percentage of the entire adhesive phase. These extremely fine tungsten grain precipitates are about 10-800 nm in size and are very uniformly distributed in the adhesive phase, which has a significant strengthening effect on the adhesive phase, which helps to improve the tensile strength and impact toughness of the alloy. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The temperature-time change curve of the heat treatment stage in the present application; Figure 2 The SEM image of the tungsten alloy material in Example 1 is magnified 500 times; Figure 3 The SEM image of the tungsten alloy material in Comparative Example 1 is magnified 500 times. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below. Wherein, the specific conditions in the embodiments are not specified, which are carried out according to the conventional conditions or the conditions recommended by the manufacturer; the instruments, devices or reagents, raw materials, etc. not specified by the manufacturer are all conventional products that can be purchased in the market.

[0024] The present application provides a high-density tungsten alloy, the preparation raw materials of which include 90-97% tungsten powder, 3-10% nickel powder and iron powder, and the mass ratio of nickel and iron is (0.5-1.5):1; wherein the Fisher particle size of the tungsten powder is 2-6 μm, the Fisher particle size of the nickel powder is 1-3 μm, and the Fisher particle size of the iron powder is 5-10 μm.

[0025] In the present application, the mass ratio of nickel and iron in the tungsten alloy raw material powder is (0.5-1.5):1. According to the existing technical means, it is considered that the mass ratio of nickel and iron (2-4):1 is beneficial to the formation of a face-centered cubic structure with good toughness of the binder phase, and it is not easy to produce unstable intermetallic compound brittle phase. However, the present application research found that the Ni:Fe (mass ratio) = (0.5-1.5):1 has a lower nickel-iron mass ratio composition than the conventional tungsten alloy, and the alloy is specially formed to form intermetallic compound Fe2W during sintering, and then combined with the two-stage heat treatment process, the intermetallic compound brittle phase produced in the process is dissolved in the binder phase, avoiding the residual of the intermetallic compound brittle phase in the structure, and preparing a tungsten alloy with a special structure of 10-800 nm extremely fine tungsten particles uniformly distributed in the binder phase. The nanoscale fine grains have a significant strengthening effect on the alloy, and the test proves that the alloy has excellent tensile strength and impact toughness. The preparation method of the high-density tungsten alloy of the present application comprises the following steps: (1) batching The tungsten powder, nickel powder and iron powder are weighed according to the amount.

[0026] (2) ball milling The weighed raw material powders are loaded into a ball mill, argon is used as a protective gas, and ball milling is carried out. The ball milling uses tungsten alloy balls with a diameter of Φ10mm, and the ball-to-material mass ratio is controlled to be (1-2):1. The rotation speed during ball milling is 50-80r / min, and the ball milling time is 20-24h. The tungsten alloy mixed ball milling powder is prepared.

[0027] During the ball milling process, the raw materials are continuously crushed, impacted and broken, so that the raw materials can be fully and uniformly mixed. The agglomerated particles of the powder are dispersed at the same time, and also play a pre-alloying role, greatly reducing the activation energy of the tungsten alloy mixed powder and improving the sintering density of the tungsten alloy mixed powder.

[0028] (3) pressing The tungsten alloy mixed ball milling powder is loaded into a mold, and pressed at a pressure of 150-220MPa. The holding time is 20-30s, and the tungsten alloy compact is obtained.

[0029] Under this pressing condition, the compact can be avoided to have defects such as edge drop, corner drop, delamination and cracks.

[0030] (4) sintering The tungsten alloy compact is placed in a sintering furnace and sintered under hydrogen protection. The hydrogen flow is controlled to be 1.5-3.5m 3 / h, the sintering temperature is 1480-1540℃, and the sintering time is 40-80min, so that a dense tungsten alloy sintered blank is obtained, and Fe2W intermetallic compound is produced in the alloy structure of the sintered blank.

[0031] (5) Heat treatment The tungsten alloy sintered blank is transferred into a heat treatment furnace, and heat treatment is performed under the protection of argon, and the argon flow is controlled to be 1.5-3.5m 3 / h; as shown in the figure, the heat treatment is a high-temperature heat treatment process repeated for multiple times, and each cycle of high-temperature heat treatment includes the following two stages: Figure 1 The first stage is a precipitation stage, and the tungsten alloy is controlled to be at a temperature of 750-850℃ in the heat treatment furnace, and the heat preservation treatment time is 2-4h; The second stage is a dissolution stage, and the temperature is further increased to 1280-1380℃ on the basis of the temperature of the first stage, and the heat preservation treatment time is 3-5h; After each cycle of high-temperature heat treatment is completed, the next cycle of high-temperature heat treatment is continued, and the cycle is repeated for 2-6 times, and after the last high-temperature heat treatment is completed, water quenching is performed to rapidly cool the tungsten alloy to room temperature, so that a heat-treated tungsten alloy is obtained.

[0032] By using the nickel-iron mass ratio content defined in the application, in the first stage of heat treatment, the intermetallic compound Fe2W formed in the sintering process and the supersaturated tungsten grains are precipitated and separated in the adhesive phase; in the second stage, high temperature can continuously dissolve the unstable intermetallic compound Fe2W brittle phase, while the precipitated and separated nanoscale fine tungsten grains are retained and distributed in the adhesive phase; in the repeated multiple cycle heat treatment process, the intermetallic compound Fe2W brittle phase continuously separates and dissolves, and the total amount of the precipitated and separated nanoscale fine tungsten grains also does not increase significantly, and can account for 2-15% of the volume of the adhesive phase; finally, in the water quenching rapid cooling, the Fe2W dissolved in the adhesive phase is prevented from re-separating, and the finally obtained tungsten alloy material has uniform distribution of extremely fine W grains with a size of about 10-800nm, which has a significant strengthening effect on the adhesive phase, so as to meet the performance requirements of high density, high strength and high toughness.

[0033] (6) Spinning The heat-treated tungsten alloy is subjected to spinning treatment through a four-hammer head radial spinning machine, the preheating temperature is 450-650℃, the heat preservation treatment time is 30-60min, and the spinning deformation amount is 20-50%, so that the tungsten alloy material with high strength, high toughness and high performance is obtained.

[0034] Through the spinning treatment after heat treatment, the uniform plastic deformation of the tungsten alloy material can be ensured, and defects such as cracks and phase changes of the tungsten alloy material can be avoided, so that the high-strength and high-toughness tungsten alloy has excellent impact toughness while the tensile strength is improved.​

[0035] The tungsten alloy material prepared by the above raw materials and the above method has excellent mechanical properties, tensile strength ≥ 1300MPa, impact toughness ≥ 100J / cm 2 .

[0036] Example 1 Step 1: Ingredients The powders of each component in terms of mass percentage are: 90% W, 3.4% Ni, 6.6% Fe, Ni:Fe (mass ratio) = 0.5:1 and weighed; Step 2: Ball milling The powders according to the above mass percentages were loaded into a ball mill, and tungsten alloy balls with a diameter of 10 mm were used for ball milling, with a ball-to-material mass ratio of 1:1. The ball milling time was 20 h, the ball mill speed was 50 r / min, and argon was used as the protective gas to obtain tungsten alloy ball-milled mixed powder; Step 3: Pressing The uniformly mixed ball-milled powder was loaded into a mold and pressed into a semi-finished green compact using a cold isostatic press at a pressing pressure of 150 MPa and a holding time of 20 seconds. Step 4: Sintering The tungsten alloy semi-finished compact is placed in a molybdenum boat covered with alumina powder, and then covered with alumina powder. The boat is pushed into a high-temperature molybdenum wire sintering furnace for sintering. The sintering temperature is 1480℃, the sintering holding time is 80min, and the hydrogen flow rate is 1.5m 3 / h, to produce tungsten alloy sintered blank; Step 5: Heat treatment The obtained tungsten alloy sintered blank was placed in a high temperature heat treatment furnace for two-stage heat treatment. The first stage was kept at 750℃ for 2h, the second stage was kept at 1280℃ for 3h, and the argon flow rate was 1.5m 3 / h, cycle number 2 times, after the last heat treatment cycle is completed, water quenching is performed and rapid cooling is performed to room temperature to obtain heat-treated tungsten alloy; Step 6: Rotary Forging The heat-treated tungsten alloy rod was forged by a four-hammer radial forging machine with a preheating temperature of 450°C, a holding time of 30 minutes, and a forging deformation of 50% to obtain a high-performance tungsten alloy material.

[0037] Through SEM test observation, such as Figure 2 As shown, the metallographic structure of the high-performance tungsten alloy material is that micron-sized nearly spherical W grains and 10-800 nm-sized fine W grain precipitates are distributed in the bonding phase.

[0038] After testing, the density of the high performance tungsten alloy material is 17.0g / cm3 , the tensile strength is 1700 MPa, and the impact toughness is 200 J / cm 2 .

[0039] Example 2 Step 1: ingredient The powders of each component are weighed according to the mass percentage: 93% W, 3.5% Ni, 3.5% Fe, and the mass ratio of Ni:Fe is 1:1; Step 2: ball milling The powders in the above mass percentage are loaded into the ball mill, the ball milling uses tungsten alloy balls with a diameter of Φ10mm, the ball-to-material mass ratio is 1.5:1, the ball milling time is 22h, the ball mill rotation speed is 65r / min, and argon is used as the protective gas to obtain the tungsten alloy ball-mixed powder; Step 3: pressing The uniformly mixed ball-mixed powder is loaded into the mold, and a cold isostatic press is used to press the semi-finished product compact according to a pressing pressure of 185MPa and a holding time of 25s; Step 4: sintering The tungsten alloy semi-finished product compact is placed in a molybdenum boat lined with aluminum oxide powder, then the compact is covered with aluminum oxide powder, and the material boat is pushed into a high-temperature molybdenum wire sintering furnace for sintering, the sintering temperature is 1510℃, the sintering holding time is 60min, the hydrogen flow rate is 2.5m 3 / h, and the tungsten alloy sintered compact is obtained; Step 5: heat treatment The obtained tungsten alloy sintered compact is placed in a high-temperature heat treatment furnace for two-stage heat treatment, the first stage holding temperature is 800℃, the holding time is 3h, the second stage holding temperature is 1330℃, the holding time is 4h, the argon flow rate is 2.5m 3 / h, the cycle number is 4 times, and after the last heat treatment cycle is completed, water quenching is performed to cool to room temperature quickly to obtain the heat-treated tungsten alloy; Step 6: rotary forging The heat-treated tungsten alloy rod is rotary forged by a four-hammer head radial rotary forging machine, the preheating temperature is 550℃, the holding time is 45min, and the rotary deformation is 35%, thereby obtaining the high-performance tungsten alloy material.

[0040] Through SEM observation, the metallographic structure of the high-performance tungsten alloy material is that micron-level near-spherical W grains and 10-800nm size fine W grain precipitates are distributed in the bonding phase.

[0041] Through testing, the density of the high-performance tungsten alloy material is 17.6g / cm 3 , the tensile strength is 1500 MPa, and the impact toughness is 150 J / cm 2 .

[0042] Example 3 Step one: ingredient The powders of each component are weighed according to the mass percentage: 97% W, 1.8% Ni, 1.2% Fe, and the mass ratio of Ni:Fe is 1.5:1; Step two: ball milling The powders with the above mass percentage are loaded into the ball mill, the ball milling uses tungsten alloy balls with a diameter of Φ10mm, the ball-to-material mass ratio is 2:1, the ball milling time is 24h, the ball mill rotation speed is 80r / min, argon gas is used as the protective gas, and tungsten alloy ball-mixed powder is obtained; Step three: pressing The uniformly mixed ball-mixed powder is loaded into the mold, and a cold isostatic press is used to press the semi-finished product compact at a pressing pressure of 220MPa and a holding time of 30s; Step four: sintering The tungsten alloy semi-finished product compact is placed in a molybdenum boat lined with aluminum oxide powder, then the compact is covered with aluminum oxide powder, and the molybdenum boat is pushed into a high-temperature molybdenum wire sintering furnace for sintering, the sintering temperature is 1540℃, the sintering holding time is 80min, the hydrogen flow rate is 3.5m 3 / h, and a tungsten alloy sintered compact is obtained; Step five: heat treatment The obtained tungsten alloy sintered compact is placed in a high-temperature heat treatment furnace for two-stage heat treatment, the first stage holding temperature is 850℃, the holding time is 4h, the second stage holding temperature is 1380℃, the holding time is 5h, the argon flow rate is 3.5m 3 / h, the cycle number is 6 times, and after the last heat treatment cycle is completed, water quenching is performed to rapidly cool to room temperature to obtain a heat-treated tungsten alloy; Step six: rotary forging The heat-treated tungsten alloy rod is rotary forged by a four-hammer head radial rotary forging machine, the preheating temperature is 650℃, the holding time is 60min, and the rotary forging deformation is 20%, thereby obtaining a high-performance tungsten alloy material.

[0043] Through SEM observation, the microstructure of the high-performance tungsten alloy material is that micron-level near-spherical W grains and 10-800nm size fine W grain precipitates are distributed in the bonding phase.

[0044] Through testing, the density of the high-performance tungsten alloy material is 18.5g / cm 3 , the tensile strength is 1300MPa, and the impact toughness is 100J / cm 2 .

[0045] Comparative Example 1 Step one: ingredient The powders of the components are weighed according to the mass percentage: 90% W, 7.0% Ni, 3.0% Fe, and the mass ratio of Ni:Fe = 2.3:1; The remaining steps two to six are the same as those in Example 1, and a tungsten alloy material is obtained.

[0046] Through SEM observation, the microstructure of the tungsten alloy material is shown in the following figure: Figure 3 The microstructure of the tungsten alloy material is that only micron-sized nearly spherical W grains are distributed in the bonding phase, and there is no fine W grain precipitate.

[0047] It is tested that the density of the tungsten alloy material of the comparative example 1 is 17.0 g / cm 3 , the tensile strength is 1520 MPa, and the impact toughness is 45 J / cm 2 .

[0048] It can be seen from the comparison between the comparative example 1 and the example 1 that when the mass ratio of Ni:Fe is greater than 1.5:1, the microstructure of the alloy is that only micron-sized nearly spherical tungsten grains are distributed in the bonding phase, and there is no fine tungsten grain precipitate, which cannot produce strengthening effect, resulting in that the strength and impact toughness of the alloy are significantly reduced compared with the example 1.

[0049] Comparative example 2 Step one: batching The powders of the components are weighed according to the mass percentage: 90% W, 2.3% Ni, 7.7% Fe, and the mass ratio of Ni:Fe = 0.3:1; The remaining steps two to six are the same as those in Example 1, and a tungsten alloy material is obtained.

[0050] Through SEM observation, the microstructure of the tungsten alloy material is that micron-sized nearly spherical W grains and 10-800 nm size fine W grain precipitates are distributed in the bonding phase.

[0051] It is tested that the density of the tungsten alloy material of the comparative example 2 is 16.4 g / cm 3 , the tensile strength is 1470 MPa, and the impact toughness is 25 J / cm 2 .

[0052] As compared with Example 1, it can be seen from the comparison of the Comparative Example 2 that, when the mass ratio of Ni:Fe is less than 0.5:1, the sintering density of the alloy decreases due to the decrease of the content of Ni and the increase of the content of Fe, the solubility of W in the binder phase decreases, the wettability decreases, the alloy is not easy to be densified, there are a large number of pores in the microstructure, the density decreases, and the tensile strength and impact toughness of the alloy also decrease, although the microstructure of the alloy is distributed with fine tungsten grain precipitates, the tensile strength and impact toughness of the alloy cannot be further improved.

[0053] Comparative Example 3 Steps 1 to 4 are the same as those in Example 1; Step 5: heat treatment The prepared tungsten alloy sintered compact is placed in a high-temperature heat treatment furnace for conventional one-stage heat treatment in the industry, the holding temperature is 1200℃, the holding time is 10h, the argon flow rate is 1.5m 3 / h, after holding, water quenching is performed to rapidly cool to room temperature, and a heat-treated tungsten alloy is obtained; Step 6 is the same as that in Example 1, and a tungsten alloy material is obtained.

[0054] Through SEM observation, the microstructure of the tungsten alloy material is that only micron-level nearly spherical tungsten grains are distributed in the binder phase, and there are no fine tungsten grain precipitates.

[0055] Through testing, the density of the tungsten alloy material of the Comparative Example 3 is 17.0g / cm 3 , the tensile strength is 1560MPa, and the impact toughness is 32J / cm 2 .

[0056] As compared with Example 1, it can be seen from the comparison of the Comparative Example 3 that, in the case that the processes of batching, pressing, ball milling, sintering and swaging are the same, the heat treatment process adopts a conventional heat treatment process, and the special heat treatment process proposed in the present application is not adopted, so that there is no precipitation-dissolution process in the alloy microstructure, the microstructure of the final alloy is that only micron-level nearly spherical tungsten grains are distributed in the binder phase, and there are no fine tungsten grain precipitates, the strengthening effect cannot be produced, and the strength and impact toughness of the alloy cannot be significantly improved.

[0057] The above only describes the preferred embodiments of the present application and is not used to limit the present application, and for those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A high-density tungsten alloy, characterized in that: The composition of the elements is as follows: 90-97wt% tungsten, the balance nickel and iron, wherein the mass ratio of nickel to iron is (0.5-1.5):1; The method for preparing the high-density tungsten alloy comprises the following steps: S1 Ingredients: Weigh tungsten powder, nickel powder and iron powder according to the amount; S2 Ball milling: The raw materials weighed in step S1 are placed in a ball mill and ball milled using tungsten alloy balls with a diameter of 10 mm to obtain a ball-milled mixed powder; S3 Pressing and molding: The ball milled mixed powder is placed into a mold and pressed using a cold isostatic press to obtain a tungsten alloy compact; S4 Sintering: Place the tungsten alloy compact in a sintering furnace and sinter under hydrogen protection to obtain a tungsten alloy sintered compact; S5 Heat treatment: Place the tungsten alloy sintered billet in a heat treatment furnace and perform multiple cycles of heat treatment under argon protection, with a continuous heat treatment temperature of 1.5-3.5m 3 / h, and finally water quenching and cooling to obtain heat-treated tungsten alloy; Each heat treatment process includes a precipitation stage and a dissolution stage. The treatment temperature of the precipitation stage is 750-850℃, and the heat preservation time is 2-4h; the treatment temperature of the dissolution stage is 1280-1380℃, and the heat preservation time is 3-5h. S6 Rotary forging: Using a four-hammer radial rotary forging machine, the heat-treated tungsten alloy is subjected to rotary forging treatment, and the preheating temperature is controlled at 450-650° C. and the holding time is 30-60 minutes to obtain the high-density tungsten alloy.

2. The high-density tungsten alloy according to claim 1, wherein In step S1 , the Fischer-Tropsch particle size of the tungsten powder is 2-6 μm, the Fischer-Tropsch particle size of the nickel powder is 1-3 μm, and the Fischer-Tropsch particle size of the iron powder is 5-10 μm.

3. The high-density tungsten alloy according to claim 1, wherein In step S2, the ball-to-material mass ratio during ball milling is (1-2):1, the ball milling time is 20-24 h, the ball mill speed is controlled at 50-80 r / min, and argon is used as the protective gas.

4. The high-density tungsten alloy according to claim 1, characterized in that In step S3, the pressing pressure is 150-220 MPa, and the holding time is 20-30 s.

5. The high-density tungsten alloy according to claim 1, characterized in that In step S4, the sintering temperature is 1480-1540°C, the sintering holding time is 40-80 minutes, and the sintering period is continued at 1.5-3.5 minutes. 3 / h hydrogen is introduced.

6. The high-density tungsten alloy according to claim 1, characterized in that In step S5, the number of times of the multi-cycle heat treatment is 2-6 times.

7. The high-density tungsten alloy according to claim 1, characterized in that In step S6, the total deformation amount during the rotary forging process is 20-50% in terms of the reduction in cross-sectional area.

8. The high-density tungsten alloy according to claim 1, characterized in that: The microstructure of the high-density tungsten alloy includes W grains of 20-40 μm and ultra-fine W grains of 10-800 nm, and the ultra-fine W grains account for 2-15% of the total volume of the bonding phase.

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