Heterostructure high strength and toughness tungsten alloy and preparation method thereof

Abstract

The application provides a heterogeneous structure high-strength and high-toughness tungsten alloy and a preparation method thereof, and the preparation method comprises the following steps: mixing tungsten powder, alloying metal powder and rare earth element powder, performing high-energy ball milling to obtain multi-element doped powder; mixing the obtained multi-element doped powder with micron-grade tungsten powder, and sintering to obtain a heterogeneous structure high-strength and high-toughness tungsten alloy with a bimodal grain size distribution; wherein the mass ratio of the multi-element doped powder to the micron-grade tungsten powder is 7:3-9:1. The application adjusts the ratio of the multi-element doped powder to the micron-grade tungsten powder to prepare the heterogeneous structure high-strength and high-toughness tungsten alloy with the bimodal grain size distribution. The method has a better improvement effect on the toughness of the tungsten alloy than the prior art, the raw materials are all micron-grade powders, the preparation process is simple, the method can be completed by using conventional equipment, and subsequent heat treatment is not needed, thereby providing a new idea for the strengthening and toughening of refractory metals.

Description

Technical Field

[0001] This invention relates to the field of refractory metal powder metallurgy preparation technology, and in particular to a heterostructure high-strength and high-toughness tungsten alloy and its preparation method. Background Technology

[0002] Tungsten (W) possesses excellent properties such as high melting point, high hardness, high thermal conductivity, low physical sputtering, and low tritium retention, making it one of the most promising plasma-oriented materials for future nuclear fusion reactors. However, tungsten's BCC crystal structure makes it intrinsically brittle, and its high ductile-brittle transition temperature (DBTT) and low recrystallization temperature result in low-temperature brittleness and recrystallization brittleness, severely limiting its future applications as a plasma-oriented material.

[0003] Currently, methods to improve tungsten toughness mainly include severe plastic deformation, alloying, simple dispersion strengthening, and multi-component doping. Severe plastic deformation can refine grains and improve tungsten toughness, but it is prone to recrystallization and grain growth at high temperatures, losing the toughening effect of fine grain structure. For alloying, the addition of alloying elements forms a plastic phase in tungsten, effectively improving its toughness, but the resulting tungsten alloy grains are generally coarse and have low strength. For simple dispersion strengthening, the addition of oxide and carbide dispersed phases provides a significant dispersion strengthening effect, but during preparation, oxide and carbide dispersed phases easily form large particles at grain boundaries, leading to stress concentration. For multi-component doping, the added alloying elements and carbide or oxide dispersed phases form a fine and complex dispersed phase within the grains, resulting in significant dispersion strengthening. The alloying elements can also absorb oxygen impurities at grain boundaries, improving grain boundary bonding strength, but the improvement effect of multi-component doping on the toughness of tungsten alloys is relatively limited. Summary of the Invention

[0004] This invention provides a heterostructure high-strength and high-toughness tungsten alloy and its preparation method, which solves the defect of the insignificant effect of the low-temperature brittleness improvement of tungsten in the prior art, realizes the high strength and toughness of tungsten, and broadens the service temperature window.

[0005] In a first aspect, the present invention provides a method for preparing a heterostructure high-strength and high-toughness tungsten alloy, comprising: mixing tungsten powder, alloying metal powder and rare earth element powder, and performing high-energy ball milling to obtain multi-element doped powder;

[0006] The obtained multi-doped powder was mixed with micron-sized tungsten powder and sintered to obtain a heterostructure high-strength and high-toughness tungsten alloy with a bimodal grain size distribution.

[0007] The volume ratio of the multi-doped powder to the micron-sized tungsten powder is 7:3-9:1.

[0008] In other words, in the total volume of the multi-component doped powder and the micron-sized tungsten powder, the multi-component doped powder accounts for 70-90% by volume, and the remainder is the micron-sized tungsten powder, which accounts for 30-10% by volume. For example, the multi-component doped powder accounts for 70% by volume, and the micron-sized tungsten powder accounts for 30% by volume. Another example is that the multi-component doped powder accounts for 85% by volume, and the micron-sized tungsten powder accounts for 15% by volume. Yet another example is that the multi-component doped powder accounts for 90% by volume, and the micron-sized tungsten powder accounts for 10% by volume.

[0009] This invention reveals that, in order to obtain a bimodal grain size distribution and good strength and toughness, it is necessary to control the ratio of multi-component doped powder to micron-sized tungsten powder. Furthermore, the optimal volume percentage of the micron-sized tungsten powder is 10-15%.

[0010] According to the preparation method of the heterostructure high strength and toughness tungsten alloy provided by the present invention, the heterostructure high strength and toughness tungsten alloy with bimodal grain size distribution has a fine grain size of 0.5-1.5 micrometers and a coarse grain size of 4.0-6.0 micrometers.

[0011] To avoid interference from oxygen during the mixing process, tungsten powder, alloyed metal powder, and rare earth element powder are mixed in a glove box protected by inert gas.

[0012] According to the preparation method of heterostructure high-strength and high-toughness tungsten alloy provided by the present invention, the high-energy ball milling parameters of the multi-element doped powder include a ball-to-powder ratio of 10:1-5:1, a ball milling speed of 400-500 rpm, a ball milling time of 45-60 hours, and a ball milling atmosphere of inert gas. The inert gas can be a commonly used inert gas such as argon or nitrogen, preferably argon.

[0013] According to the preparation method of heterostructure high-strength and high-toughness tungsten alloy provided by the present invention, the high-energy ball milling uses a WC cemented carbide jar and WC cemented carbide balls as the grinding media.

[0014] More preferably, the powder is manually mixed in the glove box at regular intervals during the ball milling process to make the mixture more uniform.

[0015] According to the preparation method of the heterostructure high-strength and high-toughness tungsten alloy provided by the present invention, in the total amount of tungsten powder, alloyed metal powder and rare earth element powder, the mass proportion of the alloyed metal powder is 0.3-0.4%, the mass proportion of the rare earth element powder is 0.8-0.9%, and the balance is tungsten powder.

[0016] By controlling the above-mentioned raw materials within the above-mentioned range, it can be ensured that the volume fraction of complex dispersed phases formed in the alloy does not exceed 5%, so as to avoid excessive dispersed phases from adversely affecting the alloy performance.

[0017] According to the preparation method of heterostructure high-strength and high-toughness tungsten alloy provided by the present invention, the alloying metal powder is one or more of micron-sized zirconium powder, titanium powder and hafnium powder; the rare earth element is micron-sized erbium powder.

[0018] The tungsten powder used in this invention is also micron-sized tungsten powder.

[0019] More preferably, the alloying metal powder is micron-sized zirconium hydride powder, and the rare earth element is micron-sized erbium powder.

[0020] According to the preparation method of heterostructure high strength and toughness tungsten alloy provided by the present invention, the sintering temperature is 1600-1800℃, the sintering pressure is 40-50MPa, and the holding time is 2-5min.

[0021] According to the preparation method of heterostructure high strength and toughness tungsten alloy provided by the present invention, sintering is carried out using a discharge plasma sintering device, and the temperature is increased at a heating rate of 100-200℃ / min during the sintering process.

[0022] Secondly, the present invention provides a heterostructure high-strength and high-toughness tungsten alloy prepared by the above-described preparation method.

[0023] The heterostructure high-strength and high-toughness tungsten alloy provided by the present invention has a relative density of 96-99%, a micro Vickers hardness of 450-700 HV, a compressive strength of 2000-3000 MPa, and a strain of 15-45%.

[0024] This invention provides a heterostructure high-strength and high-toughness tungsten alloy and its preparation method. The method involves high-energy ball milling of tungsten powder, alloying metal powder, and rare earth element powder to obtain multi-component doped powder. Then, the ratio of the multi-component doped powder to micron-sized tungsten powder is adjusted to obtain a multi-component doped tungsten alloy with a bimodal grain size. This method offers superior improvement over existing technologies, produces a highly reproducible bimodal structure, uses only micron-sized powders as raw materials, and features a simple preparation process that can be completed with conventional equipment without subsequent heat treatment. This provides a new approach to strengthening and toughening refractory metals. Attached Figure Description

[0025] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 These are the room temperature compression curves of the tungsten alloys prepared in Examples 1, 2, 3, and Comparative Example 1;

[0027] Figure 2 This is a fracture morphology diagram of the tungsten alloy prepared in Example 1;

[0028] Figure 3 This is a fracture morphology diagram of the tungsten alloy prepared in Example 2;

[0029] Figure 4 This is a fracture morphology diagram of the tungsten alloy prepared in Example 3. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0031] Unless otherwise specified, the technical means used in the embodiments of this invention are all conventional means well known to those skilled in the art. Unless otherwise stated, the materials and reagents used in the embodiments of this invention can be obtained through legitimate commercial channels.

[0032] In the following embodiments, the high-energy ball mill uses a WC cemented carbide jar and WC cemented carbide balls as the grinding media.

[0033] Example 1

[0034] This example provides a heterostructure high-strength and high-toughness tungsten alloy, the preparation steps of which are as follows:

[0035] (1) In a glove box protected by a high-purity argon atmosphere, weigh 165.57 g of tungsten powder, 0.60 g of zirconium hydride powder (0.36 wt.%, based on the total mass of tungsten powder, zirconium hydride powder, and erbium powder, the same below), and 1.42 g of erbium powder (0.85 wt.%), mix them, and load them into a ball mill jar; remove the ball mill jar from the glove box and place it on a high-energy ball mill for ball milling; after ball milling, take out the powder in the glove box protected by a high-purity argon atmosphere, and then mix the extracted multi-doped powder with micron-sized tungsten powder to obtain a tungsten-based composite powder with a bimodal grain size distribution. The content of the multi-doped powder is 85 vol.%; the content of the micron-sized tungsten powder is 15 vol.%.

[0036] The ball milling parameters included a ball-to-powder ratio of 5:1, a ball milling speed of 500 rpm, and a ball milling time of 60 hours. After 30 hours of ball milling, the powder mixed in the ball mill jar was manually remixed in the glove box.

[0037] (2) Weigh 45g of the above tungsten-based composite powder from a glove box protected by a high-purity argon atmosphere, put it into a Ф20mm graphite mold lined with graphite paper, and then put it into a spark plasma sintering equipment. Heat it at a heating rate of 100℃ / min. When the temperature reaches 1800℃, pressurize it to 45MPa and hold it for 3min. After the holding period, unload the pressure and cool it with the furnace to obtain a high-strength and high-toughness tungsten alloy.

[0038] The obtained tungsten alloy has a relative density of 99%, a micro Vickers hardness of 545.2 ± 15.6 HV, a compressive strength of 2745 MPa, and a compressive strain of 40.8%, exhibiting good strength and toughness. The fine grain size of the obtained tungsten alloy is 0.5-1.5 micrometers, and the coarse grain size is 4.0-6.0 micrometers.

[0039] Figure 1 The results include the room temperature compressive stress-strain curve of the tungsten alloy prepared in Example 1 (the test method was as follows: a cylindrical sample with a diameter of 2 mm and a height of 5 mm was used, and the compression rate was 1.0 mm / min; the compression test was completed on a universal testing machine). The compressive strength was 2745 MPa and the compressive strain was 40.8%, indicating that the prepared tungsten alloy has high strength and toughness.

[0040] Figure 2 The fracture morphology of the tungsten alloy prepared in Example 1 shows obvious transgranular fracture and a heterogeneous structure with bimodal grain size, indicating that the prepared tungsten alloy has excellent toughness.

[0041] Example 2

[0042] This example provides a heterostructure high-strength and high-toughness tungsten alloy, the preparation steps of which are as follows:

[0043] (1) In a glove box protected by a high-purity argon atmosphere, weigh 165.57 g of tungsten powder, 0.60 g of zirconium hydride powder (0.36 wt.%), and 1.42 g of erbium powder (0.85 wt.%), mix them, and load them into a ball mill jar. Remove the ball mill jar from the glove box and place it on a high-energy ball mill for ball milling. After ball milling, take out the powder in the glove box protected by a high-purity argon atmosphere, and then mix the extracted multi-component doped powder with micron-sized tungsten powder to obtain a tungsten-based composite powder with a bimodal grain size distribution. The content of the multi-component doped powder is 90 vol.%; the content of the micron-sized tungsten powder is 10 vol.%.

[0044] The ball milling parameters included a ball-to-powder ratio of 5:1, a ball milling speed of 500 rpm, and a ball milling time of 60 hours. After 30 hours of ball milling, the powder mixed in the ball mill jar was manually remixed in the glove box.

[0045] (2) Weigh 45g of the above tungsten-based composite powder from a glove box protected by a high-purity argon atmosphere, put it into a Ф20mm graphite mold lined with graphite paper, and then put it into a spark plasma sintering equipment. Heat it at a heating rate of 100℃ / min. When the temperature reaches 1800℃, pressurize it to 45MPa and hold it for 3min. After the holding period, unload the pressure and cool it with the furnace to obtain a high-strength and high-toughness tungsten alloy.

[0046] Figure 3 The fracture morphology diagram of the tungsten alloy prepared in Example 2 shows obvious transgranular fracture and a heterogeneous structure with bimodal grain size, indicating that the prepared tungsten alloy has excellent toughness.

[0047] Figure 1 The data includes the room temperature compressive stress-strain curve of the tungsten alloy prepared in Example 2.

[0048] The obtained tungsten alloy has a relative density of 99%, a micro Vickers hardness of 545.5 ± 27.3 HV, a compressive strength of 2216 MPa, and a compressive strain of 17.0%, exhibiting good strength and toughness. The fine grain size of the obtained tungsten alloy is 0.5-1.5 μm, and the coarse grain size is 4.0-6.0 μm.

[0049] Example 3

[0050] This example provides a heterostructure high-strength and high-toughness tungsten alloy, the preparation steps of which are as follows:

[0051] (1) In a glove box protected by a high-purity argon atmosphere, 165.57 g of tungsten powder, 0.60 g of zirconium hydride powder (0.36 wt.%), and 1.42 g of erbium powder (0.85 wt.%) were weighed, mixed, and placed in a ball mill jar. The ball mill jar was removed from the glove box and placed on a high-energy ball mill for ball milling. After ball milling, the powder was taken out in the glove box protected by a high-purity argon atmosphere, and then the extracted multi-doped powder was mixed with micron-sized tungsten powder to obtain a tungsten-based composite powder with a bimodal grain size distribution. The content of the multi-doped powder was 70 vol.%; the content of the micron-sized tungsten powder was 30 vol.%.

[0052] The ball milling parameters included a ball-to-powder ratio of 5:1, a ball milling speed of 500 rpm, and a ball milling time of 60 hours. After 30 hours of ball milling, the powder mixed in the ball mill jar was manually remixed in the glove box.

[0053] (2) Weigh 45g of the above tungsten-based composite powder from a glove box protected by a high-purity argon atmosphere, put it into a Ф20mm graphite mold lined with graphite paper, and then put it into a spark plasma sintering equipment. Heat it at a heating rate of 100℃ / min. When the temperature reaches 1800℃, pressurize it to 45MPa and hold it for 3min. After the holding period, unload the pressure and cool it with the furnace to obtain a high-strength and high-toughness tungsten alloy.

[0054] Figure 1 The room temperature compression curve of the tungsten alloy prepared in this example is included. Figure 4 The fracture morphology diagram of the tungsten alloy prepared in Example 3 shows obvious transgranular fracture and a heterogeneous structure with bimodal grain size, indicating that the prepared tungsten alloy has excellent toughness.

[0055] The obtained tungsten alloy has a relative density of 98%, a micro Vickers hardness of 498.1 ± 22.58 HV, a compressive strength of 2370 MPa, and a compressive strain of 43.3%, exhibiting good strength and toughness. The fine grain size of the obtained tungsten alloy is 0.5-1.5 micrometers, and the coarse grain size is 4.0-6.0 micrometers.

[0056] Comparative Example 1

[0057] This comparative example provides a tungsten alloy, the preparation steps of which are as follows:

[0058] (1) In a glove box protected by a high-purity argon atmosphere, weigh 165.57g of tungsten powder, 0.60g of zirconium hydride powder (0.36wt.%) and 1.42g of erbium powder (0.85wt.%), mix them and put them into a ball mill jar; take the ball mill jar out of the glove box and place it on a high-energy ball mill for ball milling; after ball milling, multi-element doped powder is obtained.

[0059] The ball milling parameters included a ball-to-powder ratio of 5:1, a ball milling speed of 500 rpm, and a ball milling time of 60 hours. After 30 hours of ball milling, the powder mixed in the ball mill jar was manually remixed in the glove box.

[0060] (2) Weigh 45g of the above multi-element doped powder from a glove box protected by a high-purity argon atmosphere, put it into a Ф20mm graphite mold lined with graphite paper, and then put it into a spark plasma sintering equipment. Heat it at a heating rate of 100℃ / min. When the temperature reaches 1800℃, pressurize it to 45MPa and hold it for 3min. After the holding period, unload the pressure and cool it with the furnace to obtain a tungsten alloy.

[0061] Figure 1 The room temperature compression curve of the tungsten alloy prepared in this comparative example is included.

[0062] The obtained tungsten alloy has a relative density of 99%, a micro Vickers hardness of 666.3±12.7HV, a compressive strength of 2460MPa, and the sample exhibits complete brittle fracture.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a heterostructure high-strength and high-toughness tungsten alloy, characterized in that, include: Tungsten powder, alloyed metal powder, and rare earth element powder are mixed and subjected to high-energy ball milling to obtain multi-element doped powder. In the total amount of tungsten powder, alloyed metal powder, and rare earth element powder, the mass percentage of alloyed metal powder is 0.3-0.4%, the mass percentage of rare earth element powder is 0.8-0.9%, and the remainder is tungsten powder. The obtained multi-doped powder was mixed with micron-sized tungsten powder and sintered to obtain a heterostructure high-strength and high-toughness tungsten alloy with a bimodal grain size distribution. The volume ratio of the multi-doped powder to the micron-sized tungsten powder is 7:3-9:

1. The alloying metal powder is micron-sized zirconium hydride powder, and the rare earth element powder is micron-sized erbium powder.

2. The method for preparing heterogeneous high-strength and high-toughness tungsten alloy according to claim 1, characterized in that, In the heterostructure high-strength and high-toughness tungsten alloy with bimodal grain size distribution, the fine grain size is 0.5-1.5 micrometers and the coarse grain size is 4.0-6.0 micrometers.

3. The method for preparing heterogeneous high-strength and high-toughness tungsten alloy according to claim 1, characterized in that, The parameters of the high-energy ball mill include a ball-to-material ratio of 10:1-5:1, a ball milling speed of 400-500 rpm, a ball milling time of 45-60 hours, and an inert gas atmosphere. And / or, the high-energy ball mill uses a WC cemented carbide jar and WC cemented carbide balls as the grinding media.

4. The method for preparing heterostructure high-strength and high-toughness tungsten alloy according to any one of claims 1-3, characterized in that, The sintering temperature is 1600-1800℃, the sintering pressure is 40-50 MPa, and the holding time is 2-5 min.

5. The method for preparing heterogeneous high-strength and high-toughness tungsten alloy according to claim 4, characterized in that, Sintering is carried out using a discharge plasma sintering device, with a heating rate of 100-200℃ / min during the sintering process.

6. A heterostructure high-strength and high-toughness tungsten alloy, characterized in that, It is prepared by the preparation method according to any one of claims 1-5.

7. The heterostructure high-strength and high-toughness tungsten alloy according to claim 6, characterized in that, The high-strength and high-toughness tungsten alloy has a relative density of 96-99%, a micro Vickers hardness of 450-700 HV, a compressive strength of 2000-3000 MPa, and a strain of 15-45%.

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