CN117265356A - Nuclear-grade FeCrNiAlTi high-entropy alloy jointly reinforced by biphase precipitation and preparation method and application thereof - Google Patents
Nuclear-grade FeCrNiAlTi high-entropy alloy jointly reinforced by biphase precipitation and preparation method and application thereof Download PDFInfo
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- 239000000956 alloy Substances 0.000 title claims abstract description 222
- 238000001556 precipitation Methods 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title abstract description 19
- 238000005097 cold rolling Methods 0.000 claims abstract description 26
- 229910017150 AlTi Inorganic materials 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 23
- 239000000463 material Substances 0.000 claims abstract description 20
- 230000001427 coherent effect Effects 0.000 claims abstract description 19
- 229910052751 metal Inorganic materials 0.000 claims abstract description 12
- 238000005253 cladding Methods 0.000 claims abstract description 11
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 5
- 238000005728 strengthening Methods 0.000 claims abstract 3
- 238000000137 annealing Methods 0.000 claims description 25
- 229910052715 tantalum Inorganic materials 0.000 claims description 13
- 238000003723 Smelting Methods 0.000 claims description 12
- 229910052758 niobium Inorganic materials 0.000 claims description 12
- 238000003825 pressing Methods 0.000 claims description 10
- 238000005096 rolling process Methods 0.000 claims description 10
- 238000005266 casting Methods 0.000 claims description 9
- 238000000265 homogenisation Methods 0.000 claims description 9
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims description 5
- 238000001816 cooling Methods 0.000 claims description 5
- 229910052802 copper Inorganic materials 0.000 claims description 5
- 239000010949 copper Substances 0.000 claims description 5
- 239000002184 metal Substances 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 5
- 238000007789 sealing Methods 0.000 claims description 5
- 239000000446 fuel Substances 0.000 claims description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 4
- 239000012535 impurity Substances 0.000 claims description 3
- 238000002844 melting Methods 0.000 claims description 2
- 230000008018 melting Effects 0.000 claims description 2
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- PXHVJJICTQNCMI-UHFFFAOYSA-N nickel Substances [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 55
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 12
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- 238000011084 recovery Methods 0.000 description 3
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- G—PHYSICS
- G21—NUCLEAR PHYSICS; NUCLEAR ENGINEERING
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- G21C3/00—Reactor fuel elements and their assemblies; Selection of substances for use as reactor fuel elements
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- G21C3/07—Casings; Jackets characterised by their material, e.g. alloys
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
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Abstract
The invention discloses a nuclear-grade FeCrNiAlTi high-entropy alloy with dual-phase precipitation common reinforcement, and a preparation method and application thereof, wherein the high-entropy alloy is formed by coherent L1 2 ‑Ni 3 Al and non-coherent L2 1 ‑Ni 2 An FCC-based FeCrNiAlTi high-entropy alloy with co-strengthening AlTi phase; the high-entropy alloy comprises the following metal elements: fe. Cr, ni, al, ti. The invention adopts the secondary cold rolling and heat treatment process to prepare the high-entropy alloy, and obtains the FCC matrix which is separated out L1 at the same time 2 ‑Ni 3 Al and L2 1 ‑Ni 2 The structure of AlTi ensures that the alloy has excellent oxidation resistance, corrosion resistance, neutron irradiation resistance, room temperature and high temperature mechanical properties, andand also shows good processability, and provides candidate alloy for the supercritical water-cooled reactor cladding material.
Description
Technical Field
The invention relates to the technical field of high-entropy alloy, in particular to a nuclear-grade FeCrNiAlTi high-entropy alloy jointly reinforced by two-phase precipitation, and a preparation method and application thereof.
Background
High/medium entropy alloys are receiving increasing attention from researchers due to their excellent strong plastic bonding, low temperature fracture toughness, corrosion resistance, oxidation resistance, and functional properties. The unique 'delayed diffusion' effect of the high-entropy alloy can slow the diffusion of defects such as vacancies and the like generated in the irradiation process, and improve the irradiation swelling resistance of the alloy. Therefore, the high-entropy alloy is expected to be used as a key site material in a nuclear reactor, such as a fuel cladding material, a cooling water pipeline loop material, and the like. Statistical results show that the types of materials containing Co elements in the existing high-entropy alloy system account for more than 90 percent. The Co element can not only improve the high-temperature strength of the alloy, but also reduce the stacking fault energy of the alloy, so that the alloy triggers deformation mechanisms such as stacking fault, twin crystal, phase change and the like in the deformation process, and simultaneously improves the strength and plasticity of the material. However, the Co element has a large neutron absorption section coefficient, and the addition of the Co element in the nuclear material not only reduces the neutron utilization rate, but also causes the material to be irradiated and swelled to fail. On the other hand, co is taken as a strategic element in China, the price is high, and the large addition of Co greatly improves the alloy cost, so that the industrial scale application of the high-entropy alloy is limited.
The FeCrNi-based high-entropy alloy has similar components with the traditional austenitic stainless steel, the cost is greatly reduced compared with the Co-containing high-entropy alloy, the FeCrNi-based high-entropy alloy also has excellent corrosion resistance, oxidation resistance, processing and other performances, and the components do not contain C element, so that the welding performance of the alloy is better than that of the stainless steel, and the FeCrNi-based high-entropy alloy is expected to be used as a supercritical water-cooled reactor fuel cladding material. However, this material has two problems from industrial applications: 1) The conventional service temperature of the supercritical water cooled reactor can reach 650 ℃, the pressure is 25MPa, and the high-temperature mechanical property of the entropy alloy in the ternary FeCrNi cannot meet the requirement; 2) In FeCrNi alloy, the neutron absorption section coefficient of the three components is far larger than that of active Zr alloy although not 1/10 of Co element, and the neutron irradiation swelling resistance of the FeCrNi alloy is still to be further improved.
The existing research results show that nano particles which are co-produced with the matrix are precipitated in the alloy, so that the irradiation swelling resistance of the alloy can be remarkably improved. Al and Ti elements are added into FeCrNi-based alloy, so that a precipitated phase coherent with a matrix can be formed, and the effect of improving the irradiation resistance is achieved, but the mechanical properties of the alloy, such as brittleness, tensile yield strength and tensile strength, cannot meet the current processing requirements. Namely, the existing alloy still has the problem that the high-temperature mechanical property, the processing property and the irradiation resistance are not compatible.
Disclosure of Invention
In order to overcome the defects in the prior art, one of the purposes of the invention is to provide a nuclear-grade FeCrNiAlTi high-entropy alloy which is jointly strengthened by two-phase precipitation, wherein the high-entropy alloy is composed of L1 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 The FCC-based FeCrNiAlTi high-entropy alloy jointly reinforced by the AlTi phase has excellent corrosion resistance, oxidation resistance and neutron irradiation resistance, and also has the advantages of good high-temperature mechanical property, processability and low cost; the second purpose of the invention is to provide a preparation method of the nuclear-grade FeCrNiAlTi high-entropy alloy with dual-phase precipitation common reinforcement, which adopts a plurality of cold rolling and heat treatment processes to lead the FCC matrix to be completely recovered and recrystallized, while L2 1 Only recovery but no recrystallization occurs, thereby having the effect of improving the alloy strength but not embrittling the alloy; the invention further aims to provide an application of the nuclear-grade FeCrNiAlTi high-entropy alloy with dual-phase precipitation common reinforcement, and the high-entropy alloy can be used for fuel cladding materials in supercritical water-cooled reactors.
One of the purposes of the invention is realized by adopting the following technical scheme:
nuclear-grade FeCrNiAlTi high-entropy alloy jointly strengthened by biphase precipitation, wherein the high-entropy alloy is composed of coherent L1 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 AlTi phase is strong togetherA high entropy alloy of FCC-based FeCrNiAlTi; the high-entropy alloy comprises the following metal elements: fe. Cr, ni, al and Ti; the high-entropy alloy comprises the following metal elements in atomic percent, ni:30.0 to 40.0 percent, cr:18.0 to 25.0 percent, al:5.0 to 8.0 percent, ti:5.0 to 8.0 percent, and the balance of Fe and unavoidable impurity elements.
Further, the high-entropy alloy further includes Nb; the atom percentage of Nb in the high-entropy alloy is as follows: nb:0.01 to 2.0 percent.
Further, the high-entropy alloy further comprises Ta, and the atomic percentage of Ta in the high-entropy alloy is as follows: 0.01 to 2.0 percent of TaO;
further, the high-entropy alloy further includes Nb and Ta; the atomic percentages of Nb and Ta in the high-entropy alloy are as follows: nb:0.01 to 2.0 percent, ta:0.01 to 2.0 percent; wherein, al+Ti+Nb+Ta is more than or equal to 12.0 percent and less than or equal to 17.0 percent.
The second purpose of the invention is realized by adopting the following technical scheme:
the preparation method of the nuclear-grade FeCrNiAlTi high-entropy alloy with the dual-phase precipitation common reinforcement comprises the following steps:
1) Smelting a metal raw material used in the high-entropy alloy, and forming into an alloy plate;
2) Carrying out primary cold rolling on the alloy plate;
3) Homogenizing the alloy sheet subjected to primary cold rolling;
4) Performing secondary cold rolling on the alloy plate;
5) And (3) annealing the alloy plate subjected to the secondary cold rolling to obtain the dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy.
Further, in the step 1), smelting is performed in a vacuum arc smelting furnace, and shaping is performed by adopting copper mold rapid cooling for suction casting; the thickness of the alloy plate is 4-6 mm.
Further, in step 2), the parameters of the primary cold rolling are: the pressing amount of each pass is 0.1mm, and the total rolling amount is 15-20%; in step 4), the parameters of the secondary cold rolling are as follows: the pressing amount of each pass is 0.1mm, and the total rolling amount is 20-25%.
Further, in the step 3), the specific steps of the homogenization treatment are as follows: sealing the alloy plate, and heating at 1150-1200 deg.c for 1-2 hr.
Further, in step 5), the parameters of the annealing step are: the annealing temperature is 900-1000 ℃, and the temperature is kept for 0.5-1 h after the temperature is raised. The annealing step allows partial recrystallization of the alloy in which the FCC matrix undergoes complete recovery recrystallization, L2 1 The phase only reverts.
The third purpose of the invention is realized by adopting the following technical scheme:
the application of the nuclear-grade FeCrNiAlTi high-entropy alloy with the dual-phase precipitation common reinforcement is that the nuclear-grade FeCrNiAlTi high-entropy alloy with the dual-phase precipitation common reinforcement is used for preparing fuel cladding materials in supercritical water cooled reactors.
Compared with the prior art, the invention has the beneficial effects that:
(1) The high-entropy alloy of the invention is composed of the coherent L1 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 The FCC-based FeCrNiAlTi high-entropy alloy with the AlTi phase strengthened jointly comprises Fe, cr, ni, al and Ti. Co-precipitated nano L1 in the alloy 2 -Ni 3 Al can improve the high-temperature strength and neutron irradiation resistance of the alloy, but not the co-precipitated L2 1 -Ni 2 The AlTi phase can then increase the yield strength of the alloy. By precipitation of nano-scale L1 in FCC matrix 2 -Ni 3 Al phase to obtain a structure similar to that of the nickel-based superalloy, so that the alloy has excellent high-temperature mechanical properties; nanoscale ordered L1 2 -Ni 3 Al phase is separated out, and ordered and disordered transformation can be generated in the irradiation process, so that point defects generated by irradiation are annihilated, and the alloy is prevented from failure due to irradiation swelling; by precipitation of non-coherent L2 in FCC matrix 1 -Ni 2 The AlTi phase can obviously improve the yield strength of the alloy, further regulate and control the content of the precipitated phase, and ensure that the plasticity of the alloy is not obviously reduced. The FeCrNiAlTi high-entropy alloy provided by the invention contains low-cost elements, so that the alloy cost is obviously reduced, and the FeCrNiAlTi high-entropy alloy can be applied in large-scale commercialization.
(2) The high-entropy alloy of the invention can also comprise Nb and/or Ta, wherein both Nb and Ta are L1 2 -Ni 3 Al phase forming element, when forming composite L1 2 -Ni 3 When the intermetallic compound is (Al, ti, nb, ta), the thermal stability of the intermetallic compound can be greatly improved, so that the precipitated phase can not be seriously coarsened in the long-term high-temperature service process.
(3) The preparation method of the high-entropy alloy comprises the following steps in sequence: compared with most of the existing alloy preparation processes, the method adopts the secondary cold rolling and heat treatment processes, and the primary cold rolling can increase defects such as dislocation in the alloy and is beneficial to atomic diffusion in the homogenization treatment stage. Homogenizing to eliminate segregation of components during casting; the annealing treatment can enable the alloy to be partially recrystallized, and enable the FCC matrix to be completely recovered and recrystallized, and L2 1 Only recovery but no recrystallization occurs, thereby having the effect of improving the strength of the alloy but not embrittling the alloy.
(4) The high-entropy alloy has good high-temperature mechanical property, processability and irradiation resistance. In addition, the alloy uses FCC as a matrix, can be subjected to cold working with large deformation, and has good processing capability. The invention obtains the FCC matrix by reasonably matching the components of the alloy and the preparation method, and simultaneously precipitates L1 2 -Ni 3 Al and L2 1 -Ni 2 The organization of AlTi ensures that the alloy has excellent oxidation resistance, corrosion resistance, neutron irradiation resistance, room temperature and high temperature mechanical properties, and also shows good processability, thereby providing candidate alloy for supercritical water cooled reactor cladding materials.
Drawings
FIG. 1 is a Pandat software calculation Ni 35 Fe 30 Cr 2 0Al x Ti 15-x Isothermal cross section of the alloy at 800 ℃;
FIG. 2 is an X-ray diffraction pattern of the high entropy alloy of example 1 after 900 ℃/0.5h annealing;
FIG. 3 is an EBSD result after 900 ℃/0.5h annealing of the high entropy alloy of example 1;
FIG. 4 is a TEM weave diagram of the high entropy alloy of example 1 after 900 ℃/0.5h annealing;
FIG. 5 is a graph showing the room temperature tensile mechanical properties of the high entropy alloy of example 1 after 900 ℃/0.5h annealing;
FIG. 6 is a TEM tissue diagram of the high entropy alloy of example 4 after 1000 ℃/0.5h annealing
FIG. 7 is the room temperature tensile mechanical properties of the high entropy alloy of comparative example 1 after 600 ℃/4h (a) and 800 ℃/1h (b) annealing.
Detailed Description
The present invention will be further described with reference to the accompanying drawings and detailed description, wherein it is to be understood that, on the premise of no conflict, the following embodiments or technical features may be arbitrarily combined to form new embodiments.
The invention aims to solve the problem that the strength, the processability and the neutron irradiation resistance of the existing FeCrNi-based high-entropy alloy cannot be achieved, and provides a nuclear-grade FeCrNiAlTi high-entropy alloy with jointly strengthened dual-phase precipitation and a preparation method thereof. FeCrNiAlTi high-entropy alloy prepared by the specific components and technology has reinforcing phase of nano L1 which is coherent with FCC matrix 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 AlTi two intermetallic compounds, wherein nano L1 2 The precipitated phase not only can improve the high-temperature strength of the alloy, but also can generate order in the irradiation processDisordered cyclic transformation can be performed, so that the neutron irradiation resistance of the alloy is improved, but the processing performance of the alloy is not reduced; and a certain amount of L2 which is not coherent 1 The yield strength of the alloy can be obviously improved by precipitation, so that the room temperature mechanical property of the alloy is improved.
The high-entropy alloy comprises the following metal elements: fe. Cr, ni, al and Ti; the high-entropy alloy comprises the following metal elements in atomic percent, ni:30.0 to 40.0 percent, cr:18.0 to 25.0 percent, al:5.0 to 8.0 percent, ti:5.0 to 8.0 percent, and the balance of Fe and unavoidable impurity elements.
As an embodiment, the high-entropy alloy further includes Nb; the atom percentage of Nb in the high-entropy alloy is as follows: nb:0.01 to 2.0 percent.
As an embodiment, the high-entropy alloy further includes Ta, and the atomic percentage of Ta in the high-entropy alloy is: ta 0.01-2.0%;
as an embodiment, the high entropy alloy further comprises Nb and Ta; the atomic percentages of Nb and Ta in the high-entropy alloy are as follows: nb:0.01 to 2.0 percent, ta:0.01 to 2.0 percent; wherein, al+Ti+Nb+Ta is more than or equal to 12.0 percent and less than or equal to 17.0 percent.
The role of each alloy element in FeCrNiAlTi high-entropy alloy is described below.
(1) Cr is a main element providing corrosion resistance in the high-entropy alloy, and the law of Tammann indicates that when Cr is added into Fe to form a solid solution, the electrode potential of the Cr is changed suddenly (n/8 rule) along with the increase of the Cr content, namely, when the atomic percentage (at%) of Cr reaches 12.5 percent and 25 percent of Cr reaches … …, the electrode potential of iron is suddenly increased, and corrosion is suddenly weakened; however, the Cr content is too high to induce sigma- (FeCr) and deteriorate the mechanical properties of the alloy, so that the Cr content in the invention is 18.0-25.0at.% from the comprehensive consideration of the corrosion resistance and the mechanical properties of the alloy.
(2) Ni: ni is an essential element for forming FCC solid solutions, and Ni also participates in the formation of L1 2 -Ni 3 Al and L2 1 -Ni 2 The AlTi precipitate phase, combined with Pandat thermodynamic calculation software, determines the Ni content to be 30-40at.%.
(3) Al: the addition of Al element can form compact and continuous Al on the surface of the alloy 2 O 3 The oxidation film improves the high-temperature oxidation resistance of the alloy, the higher the content is, the better the oxidation resistance is, and meanwhile, al also participates in L1 2 -Ni 3 Al and L2 1 -Ni 2 The formation of the AlTi phase, but Al is a strong BCC forming element, and excessive addition can transform the alloy from FCC to BCC, so that the alloy becomes seriously brittle, and the addition content of Al is comprehensively considered to be 5.0-8.0at percent.
(4) Ti: ti is L2 1 -Ni 2 The essential elements of the AlTi phase can promote L1 2 -Ni 3 The formation of Al, taking into account its partition relationship in the two phases, determines its content to be 5.0-8.0at.%.
(5) Nb and Ta: nb and Ta are L1 2 -Ni 3 Al phase forming element, when forming composite L1 2 -Ni 3 When the intermetallic compound is (Al, ti, nb, ta), the thermal stability of the intermetallic compound can be greatly improved, so that the precipitated phase can not be seriously coarsened in the long-term high-temperature service process, but excessive addition of Nb or Ta can promote gamma' -Ni 3 (Nb, ta) and thus both Nb and Ta are added in an amount of 2at.% or less.
The preparation method of the nuclear-grade FeCrNiAlTi high-entropy alloy with the dual-phase precipitation jointly reinforced comprises the following steps in sequence: 1) Smelting and suction casting; 2) Primary cold rolling 3) homogenization treatment; 4) Secondary cold rolling; 5) And (5) annealing treatment.
The step 1) specifically comprises the following steps: firstly, converting atomic percent into mass percent according to alloy components, adopting high-purity metal raw materials to prepare materials according to mass percent, smelting a sample by using a vacuum arc smelting furnace, and adopting a copper mold rapid cooling mode to perform suction casting to form an alloy plate with the thickness of 4-6 mm, preferably 5mm;
the step 2) specifically comprises the following steps: the alloy sheet obtained in the step 1) is cold rolled, the pressing amount of each pass is 0.1mm, the total rolling amount is 15-20%, the process can increase defects such as dislocation and the like in the alloy, and the atomic diffusion in the homogenization treatment stage is facilitated.
The step 3) is specifically as follows: sealing the alloy plate obtained in the step 2) to a quartz tube, and carrying out homogenization treatment for 1-2h at 1150-1200 ℃ to eliminate component segregation in the casting process;
the step 4) is specifically as follows: and 3) cold rolling the alloy obtained in the step 3) again, wherein the pressing amount of each pass is 0.1mm, and the total rolling amount is 20-25%.
The step 5) specifically comprises the following steps: annealing the alloy plate obtained in the step 4) at 900-1000 ℃, putting the alloy plate into a sample after the furnace temperature is raised to the required temperature, and carrying out heat preservation for 0.5-1 h to enable the alloy to be partially recrystallized, wherein the FCC matrix is completely recovered and recrystallized, and L2 1 The phase only reverts.
Example 1
FeCrNi of the present exampleThe AlTi high-entropy alloy comprises Ni 35 Fe 30 Cr 20 Al 7.5 Ti 7.5 (at.%) the high entropy alloy is L1 2 -Ni 3 Al and L2 1 -Ni 2 The AlTi dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy. The preparation method comprises the following steps:
1) Predicting the influence of the content of each component on the alloy structure by Pandat thermodynamic calculation software, wherein the typical result is shown in figure 1, so as to determine the addition range of each element of the alloy designed by the invention;
2) Screening out typical component Ni corresponding to expected tissue from the calculated phase diagram 35 Fe 30 Cr 20 Al 7.5 Ti 7.5 (at.%) converting the atomic percentage into mass percentage according to the alloy composition, adopting metal raw material with purity of 99.95% to prepare according to mass percentage, smelting the sample by using a vacuum arc smelting furnace, and adopting a copper mould quick cooling mode to suction cast into an alloy plate with thickness of 5mm;
3) The sheet obtained in the step 2) is subjected to one-time cold rolling, the pressing amount of each pass is 0.1mm, the total rolling amount is 20%, the thickness of the sheet is reduced from 5mm to 4mm, the dislocation density in the alloy can be increased in the process, and the atomic diffusion in the homogenization treatment stage is facilitated;
4) Carrying out uniform treatment on the alloy obtained in the step (3), wherein the method specifically comprises the following steps: sealing the alloy plate to a quartz tube, and heating at 1150 ℃ for 2 hours to eliminate component segregation in the casting process;
5) Carrying out secondary cold rolling on the alloy plate obtained in the step 4), wherein the pressing amount of each pass is 0.1mm, the total rolling amount is 25%, and the thickness of the plate is reduced from 4mm to 3mm;
6) Annealing the alloy plate obtained in the step 5) at 900 ℃, putting the alloy plate into a sample after the furnace temperature is increased to the required temperature, and keeping the temperature for 0.5h to enable the FCC matrix in the alloy to completely recover and recrystallize and L2 1 The phase returns only, so that subsequent plastic deformation can be coordinated.
In order to verify whether the components and the preparation method of the FeCrNiAlTi high-entropy alloy provided by the invention are effective, a sample subjected to 900 ℃/0.5h annealing treatment is subjected to systematic tissue characterization and performance test, including XRD, EBSD, TEM tissue characterization and room-temperature tensile mechanical property characterization. The results are shown in FIGS. 2 to 5.
As can be seen from the XRD results in FIG. 2, the alloy shows three different types of structure after 900 ℃/0.5h annealing, namely FCC, BCC and L2 respectively 1 -Ni 2 AlTi wherein FCC is the matrix phase, BCC and L2 1 The volume fractions are low. It can also be seen from the EBSD results in fig. 3 that the alloy consists mainly of two phases of FCC and BCC structure, where the FCC volume fraction is 90%, BCC (including L2 1 ) The volume fraction is 10%, and the alloy takes FCC as a matrix, so that the plasticity and the processability of the alloy can be ensured.
As can be seen from the TEM results in FIG. 4, L1 with a high density, 10nm in size, is precipitated in the alloy FCC matrix 2 -Ni 3 The existence of the precipitated phase can effectively improve the high-temperature mechanical property of the alloy, and is expected to meet the requirement of the long-term operation of the cladding material at high temperature on the mechanical property; moreover, the nano particles have very low nucleation energy due to very small mismatch degree with the matrix, can quickly change from ordered to disordered in the irradiation process, annihilate vacancies generated by irradiation, improve neutron irradiation swelling resistance of the alloy, and are expected to meet the requirement of the alloy with high Ni content on irradiation performance; in addition, there is Ti-rich L2 with a size ranging from nanometer to micrometer in the alloy 1 -Ni 2 AlTi, also can observe nano-scale Cr-rich BCC phase precipitation, L2 1 -Ni 2 Both the AlTi and alpha-Cr precipitated phases which are non-coherent with the FCC matrix can effectively improve the yield strength of the alloy.
Further, room temperature tensile mechanical properties of the high-entropy alloy of example 1 were tested and the results are shown in fig. 5. The room temperature yield strength of the alloy is as high as 1.4GPa, the tensile strength is close to 1.6GPa, and the uniform elongation rate can reach 8%. As can be seen by comparison, the strength of the alloy prepared by adopting the components and the treatment process is far higher than that of the existing Co-free high-entropy alloy, and meanwhile, the plasticity of the alloy reaches 8 percent, thereby meeting the requirement of engineering materials on the alloy Jin Suxing. Moreover, the alloy can be deformed by adopting a process of multiple times of cold rolling and annealing, and is expected to meet the requirement of the cladding material on the processing performance.
In conclusion, the coherent L1 can be obtained by the components and the preparation process of the high-entropy alloy 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 The FeCrNiAlTi high-entropy alloy with the AlTi phase reinforced together has excellent oxidation resistance, corrosion resistance, neutron irradiation resistance, room temperature and high temperature mechanical properties, also has good processing performance, is expected to meet the performance requirement of a supercritical water-cooled reactor fuel cladding on a material, and is a candidate material with great potential.
Example 2
The FeCrNiAlTi high-entropy alloy of the embodiment has the components of Ni 35 Fe 30 Cr 20 Al 7 Ti 7 Nb 1 (at.%) the high entropy alloy is L1 2 -Ni 3 Al and L2 1 -Ni 2 The AlTi dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy. The preparation method comprises the following steps:
the preparation method comprises the following steps:
1) Converting atomic percent into mass percent according to alloy components, proportioning metal raw materials with the purity of 99.95 percent according to mass percent, smelting a sample by a vacuum arc smelting furnace, and carrying out suction casting by adopting a copper mold quick cooling mode to obtain an alloy plate with the thickness of 5mm;
2) The sheet obtained in the step 1) is subjected to one-time cold rolling, the pressing amount of each pass is 0.1mm, the total rolling amount is 25%, the thickness of the sheet is reduced from 5mm to 3.7mm, the dislocation density in the alloy can be increased in the process, and the atomic diffusion in the homogenization treatment stage is facilitated;
3) And (3) carrying out uniform treatment on the alloy obtained in the step (2), wherein the method specifically comprises the following steps: sealing the alloy plate to a quartz tube, and heating at 1200 ℃ for 1h to eliminate component segregation in the casting process;
4) Carrying out secondary cold rolling on the alloy plate obtained in the step 3), wherein the pressing amount of each pass is 0.1mm, the total rolling amount is 20%, and the thickness of the plate is reduced from 3.7mm to 2.2mm;
6) Annealing the alloy plate obtained in the step 5) at 950 ℃, putting the alloy plate into a sample after the furnace temperature is increased to the required temperature, and keeping the temperature for 1h to enable the FCC matrix in the alloy to completely recover and recrystallize and L2 1 The phase returns only, so that subsequent plastic deformation can be coordinated.
Example 3
The FeCrNiAlTi high-entropy alloy of the embodiment has the components of Ni 35 Fe 30 Cr 20 Al 7 Ti 7 Ta 1 (at.%) the high entropy alloy is L1 2 -Ni 3 Al and L2 1 -Ni 2 The AlTi dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy. The alloy sheet was annealed at 950 ℃ for 1 hour, and the other preparation methods were the same as in example 1.
Example 4
The FeCrNiAlTi high-entropy alloy of the embodiment has the components of Ni 35 Fe 30 Cr 20 Al 6.5 Ti 6.5 Nb 1 Ta 1 (at.%) the high entropy alloy is L1 2 -Ni 3 Al and L2 1 -Ni 2 The AlTi dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy. The alloy sheet was annealed at 1000 ℃ for 1 hour, and the other preparation methods were the same as in example 1.
Experimental results indicate that the alloys of examples 2-4 are FCC substrates, wherein L1 is coherent with FCC 2 -Ni 3 Al and non-coherent L21-Ni 2 The typical TEM structure of example 4 is shown in FIG. 6, in which AlTi precipitates. Although the annealing temperature of examples 2-4 is higher than that of example 1, the alloy of example 4 was L1 due to the addition of Nb and Ta alloying elements 2 -Ni 3 Al has higher thermal stability, and the size after annealing is still about 10 nm.
Comparative example 1
The high-entropy alloy of comparative example 1 has the same composition as that of example 1, but differs from the specific preparation method in that the high-entropy alloy of comparative example 1 is still subjected to melting, primary cold rolling, homogenization treatment, secondary cold rolling and annealing treatment, but is annealedThe fire temperature is reduced to below 900 ℃ at 600 ℃/4h and 800 ℃/1h respectively. The mechanical properties of the alloy prepared are shown in FIG. 7, and the lack of annealing temperature results in a matrix and L2 1 The phase is difficult to recover and recrystallize, the alloy does not show any plastic deformation, and the alloy breaks in advance in the elastic deformation stage, so that the performance requirement of the supercritical water-cooled reactor fuel cladding on the material cannot be met
The above embodiments are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereto, but any insubstantial changes and substitutions made by those skilled in the art on the basis of the present invention are intended to be within the scope of the present invention as claimed.
Claims (10)
1. A nuclear-grade FeCrNiAlTi high-entropy alloy jointly strengthened by double-phase precipitation is characterized in that the high-entropy alloy is composed of coherent L1 2 -Ni 3 Al and non-coherent L2 1 -Ni 2 An FCC-based FeCrNiAlTi high-entropy alloy with co-strengthening AlTi phase; the high-entropy alloy comprises the following metal elements: fe. Cr, ni, al, ti; the high-entropy alloy comprises the following metal elements in atomic percent, ni:30.0 to 40.0 percent, cr:18.0 to 25.0 percent, al:5.0 to 8.0 percent, ti:5.0 to 8.0 percent, and the balance of Fe and unavoidable impurity elements.
2. The dual phase precipitation-strengthened nuclear grade fecrniaalti high-entropy alloy of claim 1, wherein the high-entropy alloy further comprises Nb; the atom percentage of Nb in the high-entropy alloy is as follows: nb:0.01 to 2.0 percent.
3. The dual phase precipitation co-strengthened nuclear grade fecrniaalti high-entropy alloy of claim 1, further comprising Ta, the Ta being in atomic percent of the high-entropy alloy: 0.01 to 2.0 percent of Tab.
4. The dual phase precipitation-co-strengthened nuclear grade fecrniaalti high-entropy alloy of claim 1, wherein the high-entropy alloy further comprises Nb and Ta; the atomic percentages of Nb and Ta in the high-entropy alloy are as follows: nb:0.01 to 2.0 percent, ta:0.01 to 2.0 percent; wherein, al+Ti+Nb+Ta is more than or equal to 12.0 percent and less than or equal to 17.0 percent.
5. The method for preparing the dual-phase precipitation co-strengthening nuclear-grade FeCrNiAlTi high-entropy alloy according to any one of claims 1 to 4, which is characterized by comprising the following steps:
1) Smelting a metal raw material used in the high-entropy alloy, and forming into an alloy plate;
2) Carrying out primary cold rolling on the alloy plate;
3) Homogenizing the alloy sheet subjected to primary cold rolling;
4) Performing secondary cold rolling on the alloy plate;
5) And (3) annealing the alloy plate subjected to the secondary cold rolling to obtain the dual-phase precipitation jointly reinforced nuclear-grade FeCrNiAlTi high-entropy alloy.
6. The method for preparing the dual-phase precipitation-strengthened nuclear-grade FeCrNiAlTi high-entropy alloy according to claim 5, wherein in the step 1), smelting is performed in a vacuum arc melting furnace, and shaping is performed by adopting copper die rapid cooling for suction casting; the thickness of the alloy plate is 4-6 mm.
7. The method for preparing a dual phase precipitation co-strengthened nuclear grade fecrniaalti high-entropy alloy according to claim 5, wherein in step 2), the parameters of the primary cold rolling are as follows: the pressing amount of each pass is 0.1mm, and the total rolling amount is 15-20%; in step 4), the parameters of the secondary cold rolling are as follows: the pressing amount of each pass is 0.1mm, and the total rolling amount is 20-25%.
8. The method for preparing a dual phase precipitation co-strengthened nuclear grade fecrniaalti high-entropy alloy according to claim 5, wherein in step 3), the specific steps of the homogenization treatment are as follows: sealing the alloy plate, and heating at 1150-1200 deg.c for 1-2 hr.
9. The method for preparing a dual phase precipitation co-strengthened nuclear grade fecrniaalti high-entropy alloy according to claim 5, wherein in step 5), the parameters of the annealing step are as follows: the annealing temperature is 900-1000 ℃, and the temperature is kept for 0.5-1 h after the temperature is raised.
10. The use of a dual phase precipitation co-strengthened nuclear grade fecrniaalti high entropy alloy according to any one of claims 1 to 4, characterized in that the dual phase precipitation co-strengthened nuclear grade fecrniaalti high entropy alloy is used for preparing fuel cladding materials in supercritical water cooled stacks.
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