Nuclear high-strength and high-toughness tungsten-based plate and preparation method thereof

Abstract

The invention discloses a nuclear high-strength and high-toughness tungsten-based plate which is characterized in that a tantalum layer serves as the center of the tungsten-based plate, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are sequentially arranged on the two sides of the tantalum layer from inside to outside respectively; the invention further discloses a method for preparing the tungsten-based plate. The method comprises the steps that firstly, tungsten powder and titanium powder are mixed, and titanium powder and tantalum powder are mixed to obtain tungsten-titanium mixed powder and titanium-tantalum mixed powder; step 2, ball milling; thirdly, the tungsten powder, the titanium powder, the tantalum powder, the tungsten-titanium mixed powder and the titanium-tantalum mixed powder are subjected to cold isostatic pressing to form metal plate blanks; fourthly, the plate blanks are sequentially put into a mold to be subjected to vacuum pressure sintering; fifthly, cogging rolling and second rolling are conducted; and sixthly, heat treatment is conducted. The titanium-tantalum mixed layer, the titanium layer, the tungsten-titanium mixed layer and the tungsten layer are sequentially arranged on the two sides of the tantalum layer from inside to outside to form a layered structure with the tantalum layer as the center, the tensile strength and toughness of the tungsten-based plate are effectively improved, and the tungsten-based plate is suitable for the technical field of nuclear structural materials.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of nuclear structural materials, and in particular relates to a nuclear high-strength and high-toughness tungsten-based plate material and a preparation method thereof. Background Art

[0002] Tungsten has the advantages of high melting point, high thermal conductivity, high creep resistance, good high temperature strength, low tritium retention and high sputtering resistance, and is considered to be the most promising plasma-facing material in nuclear fusion reactors. The main problem faced by tungsten-based materials in service is brittleness under multi-field coupling conditions, including low-temperature brittleness, recrystallization brittleness and irradiation embrittlement, which makes it impossible to meet the requirements of future fusion reactors. Therefore, improving the brittleness of tungsten or increasing its toughness has become a difficulty in the research of tungsten-based materials.

[0003] Tungsten is a typical body-centered cubic structure metal with the characteristics of non-planar extension of screw dislocations, poor mobility, and intrinsic brittleness. Therefore, the methods to increase the toughness of tungsten mainly include alloying, refinement of tungsten grains, second phase strengthening, fiber toughening, and layered toughening. The first three methods mainly increase the toughness of tungsten by improving the properties of tungsten itself. Since tungsten is very sensitive to impurity elements and is prone to recrystallization in a service environment with high temperature and heat load, the effect of increasing the toughness of tungsten using such methods is not obvious. The fiber toughening method can improve the toughness of tungsten, but the overall strength of the material is low.

[0004] The existing technology toughens tungsten-based materials by layered toughening methods. For example, the Chinese invention patent "A layered gradient structure tungsten-based composite material and its preparation method" (Announcement No. CN110053328B) uses tungsten foil, titanium foil and tantalum foil to form multiple sequentially stacked repeating units, and prepares tungsten-based composite materials through surface treatment, molding, sintering and demolding. However, the tensile strain of the tungsten-based composite material prepared by this method is relatively low, and the strength and plasticity matching is insufficient. Summary of the invention

[0005] The purpose of the present invention is to overcome the deficiencies in the above-mentioned prior art and provide a high-strength and high-toughness tungsten-based plate material for nuclear use. The tungsten-based plate material is formed by taking the tantalum layer as the center, and sequentially arranging a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer on both sides of the tantalum layer from the inside to the outside, so as to form a layered structure, so that the tantalum layer, the titanium layer and the tungsten layer are transitionally connected through the titanium-tantalum mixed layer and the tungsten-titanium mixed layer, which effectively improves the tensile strength and toughness of the tungsten-based plate material, and solves the problem of low tensile strain and insufficient strength-plasticity matching of the tungsten-based material prepared by the prior art.

[0006] To achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a high-strength and high-toughness tungsten-based plate material for nuclear use, characterized in that the tungsten-based plate material is centered on a tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer.

[0007] The present invention arranges a titanium layer between the tungsten layer and the tantalum layer, arranges a titanium-tantalum mixed layer between the tantalum layer and the titanium layer, and arranges a tungsten-titanium mixed layer between the titanium layer and the tungsten layer, so as to adjust the structure between the tungsten layer and the tantalum layer, so that the strength between each metal layer changes in a small gradient, so as to improve the strength and toughness of the tungsten-based plate material; tantalum has a high melting point, high thermal conductivity, good room temperature processing performance and plasticity, and has low hydrogen retention and high radiation resistance when facing high-flux helium ion irradiation in a nuclear fusion environment, and can toughen tungsten; however, the strength of the tungsten / tantalum layered composite material is relatively low, and in order to improve the strength of the layered composite material, titanium with the characteristics of high melting point, high strength, low activity, good heat resistance and the like is selected as an intermediate transition layer; at the same time, in order to reduce the strength gradient between the tungsten layer, the tantalum layer and the titanium layer, a tungsten-titanium mixed layer and a titanium-tantalum mixed layer are arranged to play a strength transition role and avoid cracking at the interface under the action of tension.

[0008] The above-mentioned high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the mass percentage of tungsten element in the tungsten-titanium mixed layer is not less than 95%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is not less than 20%.

[0009] The above-mentioned high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the tensile strength of the tungsten-based plate material is not less than 1500 MPa, and the elongation of the tungsten-based plate material is not less than 10%.

[0010] In addition, the present invention also discloses a method for preparing the high-strength and high-toughness tungsten-based plate material for nuclear use, characterized in that the method comprises the following steps:

[0011] Step 1: Mix tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mix titanium powder and tantalum powder to obtain titanium-tantalum mixed powder;

[0012] Step 2: ball mill the tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 respectively:

[0013] Step 3: cold isostatically press the tungsten powder, titanium powder, tantalum powder described in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs;

[0014] Step 4, placing the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and performing vacuum pressure sintering to obtain a tungsten-based composite material blank;

[0015] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence under the protection of an argon atmosphere to obtain a rolled tungsten-based composite material;

[0016] Step 6: heat-treating the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate.

[0017] The above-mentioned method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the mass purity of the tungsten powder in step one is not less than 99.99%, the Fischer-Strauss particle size of the tungsten powder is not greater than 30μm, and the oxygen content of the tungsten powder is not greater than 300ppm; the mass purity of the titanium powder is not less than 99.99%, the Fischer-Strauss particle size of the titanium powder is 30μm~50μm, and the oxygen content of the titanium powder is not greater than 300ppm; the mass purity of the tantalum powder is not less than 99.99%, the Fischer-Strauss particle size of the tantalum powder is 20μm~50μm, and the oxygen content of the tantalum powder is not greater than 300ppm.

[0018] The present invention reduces impurities by controlling the purity of raw materials, thereby preventing a large amount of impurities from becoming nucleation centers to promote particle growth, thereby achieving the purpose of reducing particle size; controls the Fisher particle size of the raw materials to control the dispersibility and reactivity of the raw material powder. The smaller the Fisher particle size and the finer the powder particles, the more conducive to uniform distribution in subsequent chemical reactions, thereby promoting more uniform nucleation growth and reducing the size of oxide and nitride particles finally formed inside the plate; controls the oxygen content of the raw materials to effectively reduce the formation of metal oxides and nitrides, while reducing the growth time of oxide particles, thereby reducing the size of the formed oxide and nitride particles and increasing the dispersion strengthening effect of the second phase; in summary, the processing performance of the plate can be improved by controlling the purity, Fisher particle size and oxygen content of the raw materials, thereby improving the mechanical properties of the plate.

[0019] The above-mentioned method for preparing a high-strength and high-toughness tungsten-based plate for nuclear use is characterized in that the ball milling in step 2 uses titanium balls, the ball milling time is 2h to 10h, and the ball milling speed is 150r / min to 350r / min.

[0020] The above-mentioned method for preparing high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the cold isostatic pressing pressure in step three is 200MPa~300MPa, the cold isostatic pressing time is 10min~20min, and the thickness of the tungsten-titanium mixed powder slab and the titanium-tantalum mixed powder slab is not more than 1mm.

[0021] The present invention adopts tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs with a thickness of no more than 1 mm as transition interfaces between tungsten powder slabs, titanium powder slabs and tantalum powder slabs. Compared with sintering in direct contact between the tungsten layer and the titanium layer, and the titanium layer and the tantalum layer, the addition of the transition interface can effectively enhance the interface bonding ability.

[0022] The method for preparing a high-strength and high-toughness tungsten-based plate for nuclear use is characterized in that the temperature of the vacuum pressure sintering in step 4 is 1300°C to 1600°C, and the vacuum degree of the vacuum pressure sintering is not greater than 10 -4 Pa, the pre-pressure of the vacuum pressure sintering is 30MPa-50MPa.

[0023] The above-mentioned method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the rolling temperature of the blank rolling in step five is 1200℃~1400℃, and the total deformation of the blank rolling is 50%~70%; the temperature of the second rolling is 400℃~600℃, and the deformation of each pass of the second rolling is 10%~15%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is carried out alternately along the length direction and the width direction in turn, and stress relief annealing treatment is carried out in an argon atmosphere between each rolling pass; the time of the stress relief annealing treatment is 10min~15min, and the temperature of the stress relief annealing treatment is 400℃~600℃.

[0024] The present invention adopts a process of first blank rolling and then performing a second rolling with a small deformation amount to improve the strength of the plate. By controlling the blank rolling temperature to 1200°C to 1400°C, which is higher than the recrystallization temperature of tungsten, the tungsten-based composite material blank can obtain a dense coarse equiaxed recrystallization structure under a large deformation reduction. Then, by performing multiple small deformation alternating rolling on the tungsten-based composite material slab, a fine fiber structure distributed along the main deformation direction is formed, so that the plate obtains a significant strengthening effect, thereby improving the strength.

[0025] The above-mentioned method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use is characterized in that the heat treatment in step six is ​​an atmosphere-protected precise temperature-controlled heat treatment process, the heat treatment temperature is 400°C to 600°C, the temperature deviation in the uniform temperature zone is not more than 10°C, and the annealing time of the heat treatment is 10min to 30min.

[0026] The present invention adopts an atmosphere protection and precise temperature control heat treatment process to prevent metal oxidation at high temperatures; the process uses computer simulation to preset a temperature curve, heating rate, insulation time, atmosphere composition, as well as the arrangement of heating elements in the furnace and sufficient circulation of furnace gas to precisely control the atmosphere conditions and temperature in the heat treatment furnace.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] 1. The present invention takes the tantalum layer as the center, and sequentially arranges a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer on both sides of the tantalum layer from the inside to the outside to form a layered structure, so that the tantalum layer, the titanium layer and the tungsten layer are transitionally bonded through the titanium-tantalum mixed layer and the tungsten-titanium mixed layer, thereby improving the interface bonding force between the tantalum layer and the titanium layer, and between the titanium layer and the tungsten layer, thereby improving the tensile strength and toughness of the tungsten-based plate.

[0029] 2. The present invention controls the mass percentage of tungsten in the tungsten-titanium mixed layer to be not less than 95%, and the mass percentage of tantalum in the titanium-tantalum mixed layer to be not less than 20%, so that the tungsten-titanium mixed layer forms a (β-Ti, W) solid solution region, and the titanium-tantalum mixed layer forms a (β-Ti, Ta) solid solution region. These two solid solutions can make the tungsten / titanium interface and the titanium / tantalum interface combine well to form a stable interface structure, so that the composite material has higher strength, and the multiple interfaces existing in the plate can further improve its strength and toughness; at the same time, by forming a solid solution region between the tungsten layer, the titanium layer and the tantalum layer, the thermal expansion coefficient of the composite material is also transitioned, reducing subsequent rolling cracking.

[0030] 3. The present invention adopts a process combining vacuum pressure sintering with multi-stage rolling, which can make the tungsten-titanium mixed powder slab and the titanium-tantalum mixed powder slab form (β-Ti, W) solid solution and (β-Ti, Ta) solid solution, and promote the diffusion of solid solution elements to both sides of the interface under the action of vacuum pressure, effectively improve the interface bonding ability between the slabs, and reduce defects such as holes at the tungsten / titanium interface and the titanium / tantalum interface, so that the tungsten-based plate is not easy to delaminate during the multi-stage rolling process, thereby increasing the machinability of the plate.

[0031] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a microscopic image of the tungsten-based plate in Example 1 of the present invention. DETAILED DESCRIPTION

[0033] Example 1

[0034] The tungsten-based plate material of this embodiment is centered on the tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer. The mass percentage of tungsten element in the tungsten-titanium mixed layer is 97%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is 25%.

[0035] The method for preparing the tungsten-based plate of this embodiment comprises the following steps:

[0036] Step 1, mixing tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mixing titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; the mass purity of the tungsten powder is 99.995%, the Fischer particle size is 20 μm, and the oxygen content is 245 ppm, the mass purity of the titanium powder is 99.993%, the Fischer particle size is 35 μm, and the oxygen content is 240 ppm, and the mass purity of the tantalum powder is 99.992%, the Fischer particle size is 40 μm, and the oxygen content is 240 ppm; the mass percentage of tungsten powder in the tungsten-titanium mixed powder is 97%, and the mass percentage of tantalum powder in the titanium-tantalum mixed powder is 25%;

[0037] Step 2: The tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 are respectively subjected to ball milling at a speed of 250 r / min for 5 hours; the ball milling uses titanium balls;

[0038] Step 3: cold isostatic pressing the tungsten powder, titanium powder, tantalum powder in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 for 15 minutes respectively to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; the cold isostatic pressing pressure is 280 MPa, and the thickness of the tungsten-titanium mixed powder slabs and the titanium-tantalum mixed powder slabs are both 0.5 mm;

[0039] Step 4: Place the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and perform vacuum pressure sintering to obtain a tungsten-based composite material blank; the vacuum pressure sintering temperature is 1400° C., and the vacuum degree of the vacuum pressure sintering is 10 -4 Pa, the pre-pressure of vacuum pressure sintering is 40MPa;

[0040] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence to obtain a rolled tungsten-based composite material; the rolling temperature of the blanking rolling is 1300°C, and the deformation of the blanking rolling is 55%; the temperature of the second rolling is 450°C, and the deformation of each pass of the second rolling is 10%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is alternately carried out along the length direction and the width direction in sequence, and a stress relief annealing treatment is carried out in an argon atmosphere between each rolling; the time of the stress relief annealing treatment is 10 minutes, and the temperature of the stress relief annealing treatment is 400°C;

[0041] Step 6: Performing atmosphere protection precise temperature control heat treatment on the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate; the heat treatment temperature is 400°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 15 minutes.

[0042] The tungsten-based plate obtained in this embodiment was subjected to microscopic analysis. Figure 1 As shown, the metal layers of the tungsten-based plate are well bonded and no defects such as holes occur.

[0043] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1614 MPa, and the elongation is 15.6%.

[0044] Example 2

[0045] The tungsten-based plate material of this embodiment is centered on the tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer. The mass percentage of tungsten element in the tungsten-titanium mixed layer is 99%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is 20%.

[0046] The method for preparing the tungsten-based plate of this embodiment comprises the following steps:

[0047] Step 1, mixing tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mixing titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; the mass purity of the tungsten powder is 99.993%, the Fischer particle size is 15 μm, and the oxygen content is 264 ppm, the mass purity of the titanium powder is 99.991%, the Fischer particle size is 25 μm, and the oxygen content is 280 ppm, the mass purity of the tantalum powder is 99.995%, the Fischer particle size is 36 μm, and the oxygen content is 278 ppm; the mass percentage of tungsten powder in the tungsten-titanium mixed powder is 99%, and the mass percentage of tantalum powder in the titanium-tantalum mixed powder is 20%;

[0048] Step 2: The tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 are respectively subjected to ball milling at a speed of 350 r / min for 10 hours; the ball milling uses titanium balls;

[0049] Step 3: cold isostatic pressing the tungsten powder, titanium powder, tantalum powder in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 for 20 minutes to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; the cold isostatic pressing pressure is 300 MPa, and the thickness of the tungsten-titanium mixed powder slabs and the titanium-tantalum mixed powder slabs are both 1 mm;

[0050] Step 4: Place the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and perform vacuum pressure sintering to obtain a tungsten-based composite material blank; the vacuum pressure sintering temperature is 1600° C., and the vacuum degree of the vacuum pressure sintering is 10 -4 Pa, the pre-pressure of vacuum pressure sintering is 50MPa;

[0051] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence to obtain a rolled tungsten-based composite material; the rolling temperature of the blanking rolling is 1400°C, and the deformation of the blanking rolling is 70%; the temperature of the second rolling is 600°C, and the deformation of each pass of the second rolling is 15%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is alternately carried out along the length direction and the width direction in sequence, and a stress relief annealing treatment is carried out in an argon atmosphere between each rolling; the time of the stress relief annealing treatment is 15 minutes, and the temperature of the stress relief annealing treatment is 600°C;

[0052] Step 6: Performing atmosphere protection precise temperature control heat treatment on the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate; the heat treatment temperature is 600°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 30 minutes.

[0053] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1589 MPa, and the elongation is 14.3%.

[0054] Example 3

[0055] The tungsten-based plate material of this embodiment is centered on the tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer. The mass percentage of tungsten element in the tungsten-titanium mixed layer is 95%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is 20%.

[0056] The method for preparing the tungsten-based plate of this embodiment comprises the following steps:

[0057] Step 1, mixing tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mixing titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; the mass purity of the tungsten powder is 99.995%, the Fischer particle size is 20 μm, and the oxygen content is 245 ppm, the mass purity of the titanium powder is 99.993%, the Fischer particle size is 35 μm, and the oxygen content is 250 ppm, the mass purity of the tantalum powder is 99.992%, the Fischer particle size is 40 μm, and the oxygen content is 240 ppm; the mass percentage of tungsten powder in the tungsten-titanium mixed powder is 95%, and the mass percentage of tantalum powder in the titanium-tantalum mixed powder is 20%;

[0058] Step 2: The tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 are respectively subjected to ball milling at a speed of 150 r / min for 2 h; the ball milling uses titanium balls;

[0059] Step 3: cold isostatic pressing the tungsten powder, titanium powder, tantalum powder in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 for 10 minutes respectively to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; the cold isostatic pressing pressure is 200 MPa, and the thickness of the tungsten-titanium mixed powder slabs and the titanium-tantalum mixed powder slabs are both 0.5 mm;

[0060] Step 4: Place the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and perform vacuum pressure sintering to obtain a tungsten-based composite material blank; the vacuum pressure sintering temperature is 1200° C., and the vacuum degree of the vacuum pressure sintering is 10 -4 Pa, the pre-pressure of vacuum pressure sintering is 30MPa;

[0061] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence to obtain a rolled tungsten-based composite material; the rolling temperature of the blanking rolling is 1200°C, and the deformation of the blanking rolling is 50%; the temperature of the second rolling is 400°C, and the deformation of each pass of the second rolling is 10%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is alternately carried out along the length direction and the width direction in sequence, and a stress relief annealing treatment is carried out in an argon atmosphere between each rolling; the time of the stress relief annealing treatment is 10 minutes, and the temperature of the stress relief annealing treatment is 400°C;

[0062] Step 6: Performing atmosphere protection precise temperature control heat treatment on the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate; the heat treatment temperature is 400°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 10 minutes.

[0063] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1567 MPa, and the elongation is 14.8%.

[0064] Example 4

[0065] The tungsten-based plate material of this embodiment is centered on the tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer. The mass percentage of tungsten element in the tungsten-titanium mixed layer is 95%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is 20%.

[0066] The method for preparing the tungsten-based plate of this embodiment comprises the following steps:

[0067] Step 1, mixing tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mixing titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; the mass purity of the tungsten powder is 99.995%, the Fischer particle size is 20 μm, and the oxygen content is 245 ppm, the mass purity of the titanium powder is 99.99%, the Fischer particle size is 50 μm, and the oxygen content is 243 ppm, and the mass purity of the tantalum powder is 99.99%, the Fischer particle size is 20 μm, and the oxygen content is 243 ppm; the mass percentage of tungsten powder in the tungsten-titanium mixed powder is 95%, and the mass percentage of tantalum powder in the titanium-tantalum mixed powder is 20%;

[0068] Step 2: The tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 are respectively subjected to ball milling at a speed of 250 r / min for 5 hours; the ball milling uses titanium balls;

[0069] Step 3: cold isostatic pressing the tungsten powder, titanium powder, tantalum powder in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 for 15 minutes respectively to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; the cold isostatic pressing pressure is 280 MPa, and the thickness of the tungsten-titanium mixed powder slabs and the titanium-tantalum mixed powder slabs are both 0.5 mm;

[0070] Step 4: Place the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and perform vacuum pressure sintering to obtain a tungsten-based composite material blank; the vacuum pressure sintering temperature is 1400° C., and the vacuum degree of the vacuum pressure sintering is 10 -4 Pa, the pre-pressure of vacuum pressure sintering is 40MPa;

[0071] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence to obtain a rolled tungsten-based composite material; the rolling temperature of the blanking rolling is 1300°C, and the deformation of the blanking rolling is 55%; the temperature of the second rolling is 450°C, and the deformation of each pass of the second rolling is 10%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is alternately carried out along the length direction and the width direction in sequence, and stress relief annealing treatment is carried out in an argon atmosphere between each rolling; the time of the stress relief annealing treatment is 12 minutes, and the temperature of the stress relief annealing treatment is 450°C;

[0072] Step 6: Performing atmosphere protection precise temperature control heat treatment on the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate; the heat treatment temperature is 500°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 15 minutes.

[0073] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1547 MPa, and the elongation is 13.8%.

[0074] Example 5

[0075] The tungsten-based plate material of this embodiment is centered on the tantalum layer, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer. The mass percentage of tungsten element in the tungsten-titanium mixed layer is 97%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is 40%.

[0076] The method for preparing the tungsten-based plate of this embodiment comprises the following steps:

[0077] Step 1, mixing tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mixing titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; the mass purity of the tungsten powder is 99.995%, the Fischer particle size is 20 μm, and the oxygen content is 245 ppm, the mass purity of the titanium powder is 99.99%, the Fischer particle size is 50 μm, and the oxygen content is 243 ppm, and the mass purity of the tantalum powder is 99.99%, the Fischer particle size is 50 μm, and the oxygen content is 242 ppm; the mass percentage of tungsten powder in the tungsten-titanium mixed powder is 97%, and the mass percentage of tantalum powder in the titanium-tantalum mixed powder is 40%;

[0078] Step 2: The tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 are respectively subjected to ball milling at a speed of 250 r / min for 5 hours; the ball milling uses titanium balls;

[0079] Step 3: cold isostatic pressing the tungsten powder, titanium powder, tantalum powder in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 for 15 minutes respectively to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; the cold isostatic pressing pressure is 280 MPa, and the thickness of the tungsten-titanium mixed powder slabs and the titanium-tantalum mixed powder slabs are both 0.5 mm;

[0080] Step 4: Place the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and perform vacuum pressure sintering to obtain a tungsten-based composite material blank; the vacuum pressure sintering temperature is 1400° C., and the vacuum degree of the vacuum pressure sintering is 10 -4 Pa, the pre-pressure of vacuum pressure sintering is 40MPa;

[0081] Step 5, the tungsten-based composite material blank obtained in step 4 is subjected to blanking rolling and second rolling in sequence to obtain a rolled tungsten-based composite material; the rolling temperature of the blanking rolling is 1300°C, and the deformation of the blanking rolling is 55%; the temperature of the second rolling is 450°C, and the deformation of each pass of the second rolling is 10%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is alternately carried out along the length direction and the width direction in sequence, and a stress relief annealing treatment is carried out in an argon atmosphere between each rolling; the time of the stress relief annealing treatment is 13 minutes, and the temperature of the stress relief annealing treatment is 550°C;

[0082] Step 6: Performing atmosphere protection precise temperature control heat treatment on the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate; the heat treatment temperature is 520°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 20 minutes.

[0083] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1523 MPa, and the elongation is 12.9%.

[0084] Comparative Example 1

[0085] The difference between this comparative example and Example 1 is that the mass purity, Fischer-Matz size and oxygen content of the raw materials in step one are different: the mass purity of the tungsten powder is 99.9wt%, the Fischer-Matz size is 48μm, and the oxygen content is 500ppm; the mass purity of the titanium powder is 99.9wt%, the Fischer-Matz size is 65μm, and the oxygen content is 650ppm; the mass purity of the tantalum powder is 99.9wt%, the Fischer-Matz size is 40μm, and the oxygen content is 500ppm.

[0086] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 1037 MPa, and the elongation is 5.4%.

[0087] The tungsten powder, titanium powder and tantalum powder in this comparative example have low quality purity, large Fisher particle size and high oxygen content, which leads to reduced tensile strength and elongation of tungsten-based plates. Since tungsten is a body-centered cubic structure and a brittle material at room temperature, the ductile-brittle transition temperature (DBTT) is an important parameter characterizing the ductility and brittleness of tungsten-based materials; in the temperature range above DBTT, tungsten exhibits toughness and can undergo plastic deformation, and in the range below DBTT, tungsten processing deformation is prone to brittle fracture; and the DBTT of tungsten materials is mainly related to the purity, oxygen content, preparation method and impurity content of the raw materials. Reducing the content of non-metallic interstitial impurities such as oxygen and nitrogen can effectively reduce the DBTT of tungsten-based composite materials and improve the elongation of tungsten-based composite materials; on the other hand, oxygen elements will also reduce the bonding force of tungsten grain boundaries during grain boundary segregation, thereby reducing the mechanical properties of tungsten-based composite materials.

[0088] In summary, it is shown that the quality purity, Fisher particle size and oxygen content of the tungsten powder, titanium powder and tantalum powder provided in the present invention can help improve the strength and toughness of the tungsten-based plate.

[0089] Comparative Example 2

[0090] The difference between this comparative example and Example 1 is that the temperature of vacuum pressure sintering in step 4 is 700°C and the vacuum degree is 10 -3 Pa, the pre-pressure is 20 MPa, and in step 5, the tungsten-based composite material blank is heated to 900° C. under the protection of argon atmosphere and then subjected to blank rolling, and the rolling deformation is 70%.

[0091] The tungsten-based composite material blank of this comparative example cracked after blanking and rolling, and delamination occurred at the interface, resulting in sample failure.

[0092] In this comparative example, the vacuum pressure sintering temperature is 700°C, which is lower than the temperature at which titanium undergoes an allotropic transformation (882°C). Titanium cannot transform from a close-packed hexagonal structure to a body-centered cubic structure, and tungsten and tantalum cannot diffuse through vacancies, resulting in low interface bonding capacity. On the other hand, the sintering temperature is too low and the pressure is too small, only 20MPa, which results in insufficient bonding between the powder particles, affecting the microstructure between the particles and causing the sample to crack during subsequent rolling. In addition, the rolling temperature in step six is ​​relatively low at 900°C. Under this temperature condition, the fluidity and plasticity of tungsten are extremely low, which can also cause the plate to crack.

[0093] In summary, it is shown that the vacuum pressure sintering temperature and pre-pressure set in the present invention are beneficial to improving the bonding strength between the layers of metal sheet blanks.

[0094] Comparative Example 3

[0095] The difference between this comparative example and Example 2 is that the tungsten-based plate material in this comparative example is centered on the tantalum layer, and a titanium layer and a tungsten layer are sequentially arranged on both sides of the tantalum layer from the inside to the outside.

[0096] After testing, the tensile strength of the tungsten-based plate prepared in this embodiment is 714 MPa, and the elongation is 3.3%.

[0097] The tungsten-based sheet material in this comparative example is a sheet material that does not use tungsten-titanium mixed powder and titanium-tantalum mixed powder. The test results show that its tensile strength and elongation are reduced. This is because during sintering, the interface between the tungsten layer and the titanium layer, and the titanium layer and the tantalum layer cannot be completely diffused and infiltrated, and there are defects such as holes at the interface, which affects the subsequent rolling effect; and only a very small solid solution area is generated between the tungsten layer and the titanium layer, and the titanium layer and the tantalum layer, and the number of interfaces in the tungsten-based sheet material is reduced, which will also lead to a decrease in the strength and toughness of the tungsten-based sheet material.

[0098] In summary, it is shown that the present invention provides a titanium-tantalum mixed layer between the tantalum layer and the titanium layer, and a tungsten-titanium mixed layer between the titanium layer and the tungsten layer, which can effectively improve the strength and toughness of the tungsten-based plate material.

[0099] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent structural transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A high-strength and high-toughness tungsten-based plate for nuclear use, characterized in that: The tungsten-based plate material takes the tantalum layer as the center, and a titanium-tantalum mixed layer, a titanium layer, a tungsten-titanium mixed layer and a tungsten layer are arranged in sequence from the inside to the outside on both sides of the tantalum layer.

2. The high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 1, characterized in that: The mass percentage of tungsten element in the tungsten-titanium mixed layer is not less than 95%, and the mass percentage of tantalum element in the titanium-tantalum mixed layer is not less than 20%.

3. The high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 1, characterized in that: The tensile strength of the tungsten-based plate material is not less than 1500 MPa, and the elongation of the tungsten-based plate material is not less than 10%.

4. A method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use as claimed in any one of claims 1 to 3, characterized in that: The method comprises the following steps: Step 1: Mix tungsten powder and titanium powder to obtain tungsten-titanium mixed powder, and mix titanium powder and tantalum powder to obtain titanium-tantalum mixed powder; Step 2: ball milling the tungsten-titanium mixed powder and the titanium-tantalum mixed powder obtained in step 1 respectively; Step 3: cold isostatically press the tungsten powder, titanium powder, tantalum powder described in step 1 and the tungsten-titanium mixed powder and titanium-tantalum mixed powder after ball milling in step 2 to obtain tungsten powder slabs, titanium powder slabs, tantalum powder slabs, tungsten-titanium mixed powder slabs and titanium-tantalum mixed powder slabs; Step 4, placing the slabs obtained in step 3 into a mold in the order of tungsten powder slab, tungsten-titanium mixed powder slab, titanium powder slab, titanium-tantalum mixed powder slab, tantalum powder slab, titanium-tantalum mixed powder slab, titanium powder slab, tungsten-titanium mixed powder slab, and tungsten powder slab, and performing vacuum pressure sintering to obtain a tungsten-based composite material blank; Step 5, performing blanking rolling and second rolling on the tungsten-based composite material blank obtained in step 4 in sequence to obtain a rolled tungsten-based composite material; Step 6: heat-treating the rolled tungsten-based composite material blank obtained in step 5 to obtain a tungsten-based plate.

5. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The mass purity of the tungsten powder in step one is not less than 99.99%, the Fischer-Strauss particle size of the tungsten powder is not greater than 30 μm, and the oxygen content of the tungsten powder is not greater than 300 ppm; the mass purity of the titanium powder is not less than 99.99%, the Fischer-Strauss particle size of the titanium powder is 25 μm to 50 μm, and the oxygen content of the titanium powder is not greater than 300 ppm; the mass purity of the tantalum powder is not less than 99.99%, the Fischer-Strauss particle size of the tantalum powder is 20 μm to 50 μm, and the oxygen content of the tantalum powder is not greater than 300 ppm.

6. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The ball mill in step 2 uses titanium balls, the ball milling time is 2h to 10h, and the ball milling speed is 150r / min to 350r / min.

7. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The cold isostatic pressing pressure in step three is 200MPa-300MPa, the cold isostatic pressing time is 10min-20min, and the thickness of the tungsten-titanium mixed powder slab and the titanium-tantalum mixed powder slab is not more than 1mm.

8. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The temperature of the vacuum pressure sintering in step 4 is 1200°C to 1600°C, and the vacuum degree of the vacuum pressure sintering is not greater than 10 -4 Pa, the pre-pressure of the vacuum pressure sintering is 30MPa-50MPa.

9. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The rolling temperature of the bloom rolling in step five is 1200°C to 1400°C, and the total deformation of the bloom rolling is 50% to 70%; the temperature of the second rolling is 400°C to 600°C, and the deformation of each pass of the second rolling is 10% to 15%, and the process of the second rolling is: the first rolling is carried out along the width direction, and then the rolling is carried out alternately along the length direction and the width direction in turn, and stress relief annealing treatment is carried out in an argon atmosphere between each rolling pass; the time of the stress relief annealing treatment is 10min to 15min, and the temperature of the stress relief annealing treatment is 400°C to 600°C.

10. The method for preparing a high-strength and high-toughness tungsten-based plate material for nuclear use according to claim 4, characterized in that: The heat treatment in step six is ​​an atmosphere protection precise temperature control heat treatment process, the heat treatment temperature is 400°C to 600°C, the temperature deviation in the uniform temperature zone is no more than 10°C, and the annealing time of the heat treatment is 10min to 30min.

Images