A brittle-resistant FeCrAl alloy and a manufacturing method thereof

Abstract

A brittle-resistant FeCrAl alloy and a manufacturing method thereof, belonging to the field of metal materials. The brittle-resistant FeCrAl alloy comprises, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the remainder being Fe and unavoidable impurities. This alloy can effectively reduce the solid solution of Al in the alloy matrix, thereby reducing alloy embrittlement caused by Al segregation under high-temperature irradiation conditions, and improving the service life and reliability of structural parts using this alloy under high-temperature irradiation conditions.

Description

Technical Field

[0001] The invention belongs to the field of metal materials, and in particular relates to an embrittlement-resistant FeCrAl alloy and a manufacturing method thereof. Background Art

[0002] FeCrAl alloys have good high-temperature corrosion resistance and excellent strength-toughness matching properties, and have been widely used as structural materials in advanced nuclear energy systems. However, in order to enhance the corrosion resistance of FeCrAl alloys, a high content of Al is added, which limits the formability of the material. Under high temperature or strong irradiation conditions, the Al element dissolved in the alloy matrix is ​​prone to segregation, resulting in significant high-temperature embrittlement or irradiation embrittlement of the material. Therefore, the current FeCrAl material needs to limit the Al content to below 4.5% to ensure its comprehensive performance for long-term service in high-temperature and irradiation environments. This results in the FeCrAl alloy structural components in advanced nuclear energy systems being unable to fully utilize the corrosion resistance advantages brought by the high Al content, which restricts the further improvement of the mechanical properties and reliability of nuclear energy system structural components. Summary of the Invention

[0003] The present invention aims to provide an embrittlement-resistant FeCrAl alloy, which suppresses the embrittlement of the FeCrAl alloy under high temperature or irradiation conditions by increasing the Al content. The present invention also provides a method for manufacturing the embrittlement-resistant FeCrAl alloy.

[0004] According to an embodiment of one aspect of the present invention, an embrittlement-resistant FeCrAl alloy is provided, comprising, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities.

[0005] Furthermore, in some embodiments, the alloy contains, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities.

[0006] Furthermore, in some embodiments, the embrittlement-resistant FeCrAl alloy matrix includes uniformly dispersed Y-Si-Al-O quaternary oxide particles.

[0007] By controlling the ratios of Y, Si, Al, and O elements, the Al element can be dispersed in the alloy matrix mainly in the form of a precipitated phase, thereby effectively reducing the solid solution of the Al element in the alloy matrix, thereby inhibiting the alloy embrittlement caused by grain boundary segregation of the solid-solution Al under high-temperature irradiation conditions, and thereby improving the strength and reliability of the alloy.

[0008] Furthermore, in some embodiments, the average particle size of the Y-Si-Al-O quaternary oxide particles is ≤25 nm, and the number density is ≥10 23 / m 3 .

[0009] Furthermore, in some embodiments, the embrittlement-resistant FeCrAl alloy has a yield strength of ≥130 MPa, a tensile strength of ≥140 MPa, and an elongation of ≥25% at 850°C; and an elongation of ≥2.5% after 5dpa irradiation treatment at 850°C.

[0010] According to another embodiment of the present invention, a method for manufacturing an embrittlement-resistant FeCrAl alloy is provided, the method comprising the following steps:

[0011] Step a): Providing raw materials, which include, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities, wherein Al and Si are added in the form of SiO2-coated Al powder, Y is added in the form of Y2O3 powder, and the remaining elements are added in the form of pure metal powder or alloy powder;

[0012] Step b): ball milling the raw materials to obtain a mixed powder;

[0013] Step c): performing hot isostatic pressing on the mixed powder to obtain an alloy blank;

[0014] Step d): Forging the alloy blank to obtain a forged blank;

[0015] Step e): Annealing the forged blank to obtain an embrittlement-resistant FeCrAl alloy product.

[0016] By adding Si, Al, and O elements in the form of composite powder, on the one hand, the element ratio can be effectively and accurately controlled, and on the other hand, the precipitation of Y-Si-Al-O quaternary oxide particles can be promoted during the manufacturing process, reducing the solid solution of Al in the alloy matrix; alloy manufacturing through hot isostatic pressing process can reduce the occurrence of liquid phase during the manufacturing process and further reduce the solid solution state of Al element.

[0017] Furthermore, in some embodiments, in step a), the raw material contains, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the remainder being Fe and unavoidable impurities.

[0018] Furthermore, in some embodiments, in the step a), the particle size of the SiO2-coated Al powder is ≤40 μm.

[0019] Furthermore, in some embodiments, in step c), the hot isostatic pressing treatment temperature is 1100° C.-1150° C., the holding time is 1 h-2 h, and the pressure is 120 MPa-170 MPa.

[0020] Furthermore, in some embodiments, in the step e), the annealing treatment is performed at a temperature of 900° C. to 1000° C. and for a time of 1.5 h to 2.5 h.

[0021] Furthermore, in some embodiments, the method is used to manufacture the embrittlement-resistant FeCrAl alloy provided in any of the aforementioned embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is an electron microscope photo of SiO2-coated Al composite powder in one embodiment;

[0023] Figure 2 1 is a transmission electron microscope photograph of the embrittlement-resistant FeCrAl alloy structure in one embodiment and a distribution diagram of elements within the photograph area.

[0024] The purpose of the above drawings is to provide a detailed description of the present invention so that those skilled in the art can understand the technical concept of the present invention, and is not intended to limit the present invention. DETAILED DESCRIPTION

[0025] The present invention will be further described in detail below through specific embodiments with reference to the accompanying drawings.

[0026] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in connection with the embodiment may be included in at least one embodiment herein. The appearance of such phrases in various places in the specification does not necessarily refer to the same embodiment, nor does it limit mutually exclusive independent or alternative embodiments. Those skilled in the art will appreciate that an embodiment herein may be combined with other embodiments as long as no structural conflicts arise.

[0027] In the description herein, "a plurality of" means at least two.

[0028] Conventional FeCrAl alloys currently possess excellent high-temperature mechanical properties and reasonable radiation resistance, making them suitable for use in the manufacture of various reactor structural components. However, for alloys with a Cr content of 10%-18%, Al readily segregates at grain boundaries under high-temperature irradiation conditions, causing significant embrittlement of the alloy. Therefore, studies such as "Alloy design and characterization of arecrystallized FeCrAl-ODS cladding for accident-tolerant BWR fuels: An overview of research activity in Japan." J Nucl Mater, 2023, 583, 154508. indicate that the Al weight ratio should be controlled to 5% or less to mitigate the severe negative impact of Al segregation on material properties due to grain boundary embrittlement. At the time, Al significantly impacted the corrosion resistance of FeCrAl alloys. Reducing the Al content significantly reduced the corrosion resistance of FeCrAl alloys, which in turn negatively impacted the service life and reliability of reactor structural components.

[0029] In order to overcome the above-mentioned shortcomings, an embodiment of one aspect of the present invention provides an embrittlement-resistant FeCrAl alloy, which comprises, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities.

[0030] In a preferred embodiment, the alloy contains, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and not more than 0.05% C, with the balance being Fe and unavoidable impurities.

[0031] The alloy matrix includes uniformly dispersed Y-Si-Al-O quaternary oxide particles. In a preferred embodiment, the distribution of Y-Si-Al-O quaternary oxide particles in the alloy matrix is ​​as follows: Figure 2 By comparison Figure 2 The distribution of different elements in the alloy shows that Fe and Cr are evenly distributed in the alloy matrix, while Y, Si, Al, and O are mainly concentrated in the quaternary precipitated phase particles 1, and there is almost no enrichment of Al element near the grain boundary 2. In a preferred embodiment, the average particle size of the Y-Si-Al-O quaternary oxide particles is ≤25nm, and the number density is ≥10 23 / m 3.

[0032] In conventional FeCrAl alloys, 80%-90% of the Al element is distributed in the alloy matrix in the form of solid solution, and a small amount exists in the form of ternary oxide precipitation phase. Figure 2 From the comparison, it can be seen that the embrittlement-resistant FeCrAl alloy provided by the embodiment of the present invention effectively reduces the Al content in the solid solution in the alloy matrix, thereby effectively preventing the precipitation of Al elements at the grain boundaries under high temperature and / or irradiation conditions, and inhibiting the catalytic tendency of the alloy.

[0033] The embrittlement-resistant FeCrAl alloy provided in the above embodiments exhibits excellent high-temperature mechanical properties and resistance to radiation embrittlement. At 850°C, the alloy exhibits a yield strength of 130 MPa or greater, a tensile strength of 140 MPa or greater, and an elongation of 25% or greater. After irradiation at 850°C for 5 dpa, the alloy exhibits an elongation of 2.5% or greater.

[0034] According to another embodiment of the present invention, a method for manufacturing an embrittlement-resistant FeCrAl alloy is provided, the method comprising the following steps:

[0035] Step a): Providing a raw material powder. The raw material powder comprises, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities. In a preferred embodiment, the raw material powder comprises, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities. Al and Si are added in the form of SiO2-coated Al powder; Y is added in the form of Y2O3 powder; and the remaining elements are added in the form of pure metal powder or alloy powder. Specifically, in some embodiments, Fe-Cr alloy powder can be prepared by gas atomization powder process; a layer of SiO2 is uniformly coated on the surface of micron-sized pure Al powder by sol-gel method to obtain composite powder. The morphology of SiO2-coated Al composite powder under electron microscope is as follows: Figure 1 As shown, the average particle size is ≤40μm.

[0036] Step b): Fe-Cr alloy powder, SiO2-coated Al composite powder and Y2O3 powder are ball-milled to obtain a mixed powder, with a ball-to-material ratio of 10:1 and a rotation speed of 400 rpm.

[0037] Step c): The mixed powder is loaded into a mold and subjected to hot isostatic pressing treatment in a hot isostatic pressing furnace at a heating temperature of 1100°C-1150°C, a holding time of 1h-2h, and a pressure of 120MPa-170MPa to obtain an alloy billet.

[0038] Step d): Forging the alloy billet to obtain a forged billet. The purpose of the forging treatment is to further densify the structure of the alloy billet and eliminate defects such as pores remaining after the hot isostatic pressing treatment.

[0039] Step e): Annealing the forged blank to stabilize the microstructure and morphology of the alloy, the annealing temperature is 900° C.-1000° C., and the time is 1.5 h-2.5 h, to obtain a brittle-resistant FeCrAl alloy product.

[0040] The above method can be used to manufacture the embrittlement-resistant FeCrAl alloy provided in the above embodiment. Since the hot isostatic pressing process is used for forming, the raw materials do not melt and no liquid phase appears during the forming process, which effectively avoids the occurrence of non-uniform solidification structure and segregation. The addition of Al, Si, and O elements in the form of Al2O3 powder coated with SiO2 further improves the uniformity of the elemental composition, promotes the full participation of Al element in the formation of Y-Si-Al-O quaternary oxide particles, and reduces the solid solution of Al in the alloy structure. The average particle size of the Y-Si-Al-O quaternary oxide particles in the finished alloy is ≤25nm, and the number density is ≥10 23 / m 3 .

[0041] In a first preferred embodiment, the FeCrAl alloy is produced by the following method:

[0042] A raw material powder is provided, wherein, by weight percentage, Cr accounts for 14.5%, Al accounts for 4.8%, Si accounts for 0.35%, Y accounts for 0.95%, O accounts for 0.65%, C <0.05%, and the balance is Fe. Fe and Cr are added in the form of Fe-Cr alloy powder, Al and Si are added in the form of SiO2-coated Al composite powder with a particle size of approximately 20 μm, and Y is added in the form of Y2O3 powder.

[0043] The raw material powder is ball-milled to obtain a mixed powder.

[0044] The mixed powder was placed in a mold and hot isostatically pressed at 150 MPa and 1150°C for 2 h to obtain an alloy billet.

[0045] The alloy billet is forged to obtain a forged billet.

[0046] The forged billet is annealed in a muffle furnace at a heating temperature of 900° C. to 1000° C. for 2 hours to obtain a brittle-resistant FeCrAl alloy product.

[0047] The alloy sample has a yield strength of 156 MPa, a tensile strength of 166 MPa, and an elongation of 42% at 850°C; after irradiation treatment at 850°C and 5 dpa, the elongation is 5.8%.

[0048] In a second preferred embodiment, the FeCrAl alloy is manufactured by the following method:

[0049] A raw material powder is provided, wherein, by weight percentage, Cr accounts for 14.2%, Al accounts for 5.5%, Si accounts for 0.61%, Y accounts for 1.18%, O accounts for 1.02%, C <0.05%, and the balance is Fe. Fe and Cr are added in the form of Fe-Cr alloy powder, Al and Si are added in the form of SiO2-coated Al composite powder with a particle size of approximately 20 μm, and Y is added in the form of Y2O3 powder.

[0050] The raw material powder is ball-milled to obtain a mixed powder.

[0051] The mixed powder was placed in a mold and hot isostatically pressed at 150 MPa and 1150°C for 2 h to obtain an alloy billet.

[0052] The alloy billet is forged to obtain a forged billet.

[0053] The forged billet is annealed in a muffle furnace at a heating temperature of 900° C. to 1000° C. for 2 hours to obtain a brittle-resistant FeCrAl alloy product.

[0054] The alloy sample has a yield strength of 152MPa, a tensile strength of 168MPa, and an elongation of 41% at 850°C; after irradiation treatment at 850°C and 5dpa, the elongation is 4.2%.

[0055] In a third preferred embodiment, the FeCrAl alloy is manufactured by the following method:

[0056] A raw material powder is provided, wherein, by weight percentage, Cr accounts for 15.5%, Al accounts for 6.7%, Si accounts for 0.77%, Y accounts for 1.34%, O accounts for 1.24%, C <0.05%, and the balance is Fe. Fe and Cr are added in the form of Fe-Cr alloy powder, Al and Si are added in the form of SiO2-coated Al composite powder with a particle size of approximately 20 μm, and Y is added in the form of Y2O3 powder.

[0057] The raw material powder is ball-milled to obtain a mixed powder.

[0058] The mixed powder was placed in a mold and hot isostatically pressed at 150 MPa and 1150°C for 2 h to obtain an alloy billet.

[0059] The alloy billet is forged to obtain a forged billet.

[0060] The forged billet is annealed in a muffle furnace at a heating temperature of 900° C. to 1000° C. for 2 hours to obtain a brittle-resistant FeCrAl alloy product.

[0061] The alloy sample has a yield strength of 145 MPa, a tensile strength of 152 MPa, and an elongation of 35% at 850°C; after irradiation treatment at 850°C and 5 dpa, the elongation is 3.9%.

[0062] In a comparative example, a FeCrAl alloy was produced by:

[0063] A raw material powder is provided, wherein, by weight percentage, Cr accounts for 15.4%, Al accounts for 6.6%, Si accounts for 0.78%, Y accounts for 1.31%, O accounts for 1.23%, C <0.05%, and the balance is Fe. In the raw material powder, Y is added in the form of Y2O3 powder, and the remaining components are in the form of pure metal powders or homogeneous alloy powders.

[0064] The raw material powders were ball-milled and then loaded into a mold. Hot isostatic pressing was performed at 1150° C. for 2 h under 150 MPa, and then forged and annealed at 900° C.-1000° C. for 2 h to obtain a comparative FeCrAl alloy.

[0065] The alloy sample has a yield strength of 188 MPa, a tensile strength of 201 MPa, and an elongation of 16% at 850°C; after 5dpa irradiation treatment at 850°C, the elongation is only 0.8%.

[0066] By comparing the above embodiments with the comparative examples, it can be seen that the embrittlement-resistant FeCrAl alloy provided by the present invention exhibits good mechanical properties and resistance to radiation embrittlement under high-temperature irradiation conditions, and can effectively improve the service life and reliability of nuclear power facility structural parts.

[0067] The purpose of the above embodiments is to provide a further detailed description of the present invention in conjunction with the accompanying drawings so that those skilled in the art can understand the technical concept of the present invention. Within the scope of the present invention, optimization or equivalent replacement of the technical features involved, as well as combination of implementation methods in different embodiments without conflict of principle, all fall within the scope of protection of the present invention.

Claims

1. A FeCrAl alloy resistant to embrittlement, characterized in that: The FeCrAl alloy comprises 10.0% to 18.0% Cr, 3.5% to 7.0% Al, 0.2% to 0.8% Si, 0.6% to 1.4% Y, 0.4% to 1.3% O, and no more than 0.05% C by weight, with the balance being Fe and unavoidable impurities. During the manufacturing process of the embrittlement-resistant FeCrAl alloy, Al and Si are added in the form of Al powder coated with SiO2; the matrix of the embrittlement-resistant FeCrAl alloy comprises uniformly dispersed Y-Si-Al-O quaternary oxide particles, wherein the average particle size of the Y-Si-Al-O quaternary oxide particles is ≤25nm and the number density is ≥10 23 / m 3 .

2. The embrittlement-resistant FeCrAl alloy according to claim 1, characterized in that It contains, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities.

3. The embrittlement-resistant FeCrAl alloy according to claim 1, characterized in that The embrittlement-resistant FeCrAl alloy has a yield strength of ≥130 MPa, a tensile strength of ≥140 MPa, and an elongation of ≥25% at 850° C.; and an elongation of ≥2.5% after irradiation treatment at 850° C. for 5 dpa.

4. A method for manufacturing an embrittlement-resistant FeCrAl alloy, characterized in that: The following steps are involved: Step a): Providing raw materials, which include, by weight, 10.0%-18.0% Cr, 3.5%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities, wherein Al and Si are added in the form of SiO2-coated Al powder, Y is added in the form of Y2O3 powder, and the remaining elements are added in the form of pure metal powder or alloy powder; Step b): ball milling the raw materials to obtain a mixed powder; Step c): performing hot isostatic pressing on the mixed powder to obtain an alloy blank; Step d): Forging the alloy blank to obtain a forged blank; Step e): Annealing the forged blank to obtain an embrittlement-resistant FeCrAl alloy product.

5. The method for producing an embrittlement-resistant FeCrAl alloy according to claim 4, wherein: In step a), the raw material contains, by weight, 10.0%-18.0% Cr, 4.8%-7.0% Al, 0.2%-0.8% Si, 0.6%-1.4% Y, 0.4%-1.3% O, and no more than 0.05% C, with the balance being Fe and unavoidable impurities.

6. The method for producing an embrittlement-resistant FeCrAl alloy according to claim 4 or 5, characterized in that: In the step a), the particle size of the SiO2-coated Al powder is ≤40 μm.

7. The method for producing an embrittlement-resistant FeCrAl alloy according to claim 4 or 5, characterized in that: In the step c), the hot isostatic pressing treatment temperature is 1100° C.-1150° C., the holding time is 1 h-2 h, and the pressure is 120 MPa-170 MPa.

8. The method for producing an embrittlement-resistant FeCrAl alloy according to claim 4 or 5, characterized in that: In the step e), the annealing treatment temperature is 900° C.-1000° C., and the time is 1.5 h-2.5 h.

9. The method for producing an embrittlement-resistant FeCrAl alloy according to claim 4 or 5, characterized in that: Used for producing the embrittlement-resistant FeCrAl alloy according to any one of claims 1 to 3.

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