FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion and preparation method thereof

Abstract

The present application relates to the field of corrosion-resistant alloy materials, and particularly relates to a FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion and a preparation method thereof.The high-entropy alloy has the following chemical components in percentage by weight: Fe: 35-55%; Ni: 20-35%; Cr: 10-20%; Al: 5-15%; and Ti: 1-10%.The method prepares an alloy plate through arc melting and a copper mold casting method, homogenizes and rolls the alloy plate, and then anneals and ages the alloy plate to obtain a dual-phase structure with a face-centered cubic matrix and a body-centered cubic ordered precipitated phase, which makes the FeNiCrAlTi high-entropy alloy have high strength and toughness.In addition, the FeNiCrAlTi high-entropy alloy can form a protective Cr and Al oxide film in a liquid lead-bismuth environment, and the alloy contains a small amount of Ti element to promote the formation of a protective Al2O3 film, hinder the penetration of liquid lead-bismuth into the matrix, and make the alloy have excellent liquid lead-bismuth corrosion resistance.

Description

TECHNICAL FIELD

[0001] The application relates to the field of corrosion-resistant alloy materials, in particular to a FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion and a preparation method thereof. BACKGROUND

[0002] Due to the characteristics of low melting point, high boiling point, chemical inertness and excellent nuclear performance, the lead-bismuth eutectic is regarded as the fourth generation lead-cooled fast reactor coolant and the spallation target and coolant of the accelerator-driven subcritical system, but the serious liquid metal corrosion of the structural material caused by the lead-bismuth eutectic is one of the key factors limiting the application. On the one hand, the structural material contains metal elements (such as Ni, Mn, etc.) with high solubility in high-temperature liquid lead-bismuth, which leads to dissolution corrosion of the structural material and destroys the integrity of the structural material; on the other hand, the structural material is seriously oxidized, which leads to thickening of the oxide film, and the oxide film is prone to peeling. It is urgent to research a structural material with excellent liquid lead-bismuth corrosion resistance.

[0003] The high-entropy alloy is one of the candidate materials for the fuel cladding of the lead-cooled fast reactor, and due to the high-entropy effect in thermodynamics, the lattice distortion effect in structure, the delayed diffusion effect in dynamics and the cocktail effect in performance, the high-entropy alloy can obtain excellent liquid lead-bismuth corrosion resistance through reasonable composition design and preparation process. SUMMARY

[0004] The application aims to provide a FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion and a preparation method thereof, and the high-entropy alloy not only has high strength and toughness, but also has excellent liquid lead-bismuth corrosion resistance.

[0005] The technical scheme of the application is as follows:

[0006] A FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion, and the chemical composition of the high-entropy alloy is as follows in terms of percentage by weight:

[0007] Fe: 35-55%; Ni: 20-35%; Cr: 10-20%; Al: 5-15%; and Ti: 1-10%.

[0008] The FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion has the microstructure characteristics of face-centered cubic and body-centered cubic dual-phase structure.

[0009] The FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion has the microstructure characteristics of face-centered cubic and body-centered cubic dual-phase structure.

[0010] The FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion has a yield strength of 900-1100 MPa, a tensile strength of 1200-1300 MPa and an elongation of 10-20% under room temperature conditions.

[0011] The preparation method of the FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion comprises the following steps:

[0012] (1) The raw materials are weighed according to preset component proportions, and the raw materials are placed into a vacuum chamber to be prepared into alloy ingots through electric arc melting under the protection of a homogeneous atmosphere, and then the alloy ingots are poured into alloy plates through a copper mold casting method;

[0013] (2) The alloy plates are subjected to homogenization treatment, rolling deformation treatment, annealing and aging treatment to obtain the FeNiCrAlTi high-entropy alloy.

[0014] In the step (1) of the preparation method of the FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion, the vacuum chamber is first pre-evacuated to an air pressure lower than 1*10 -2 Pa, then high-purity argon is filled into the vacuum chamber to make the air pressure of the vacuum chamber 3*10 4 ~ 9*10 4 Pa, and then electric arc melting is performed, the melting current is 280-500 A, the alloy melt is poured into a copper mold of a corresponding size, and the alloy plate is obtained.

[0015] In the step (2) of the preparation method of the FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion, the homogenization treatment temperature is 1000-1250 DEG C, the holding time is 1-4 h, and water cooling is performed to room temperature; the rolling deformation treatment is room temperature rolling, the rolling direction of the alloy plate is along the length direction, the alloy plate is rotated by 180 DEG after each rolling pass, the rolling reduction per pass is 0.1-0.3 mm, and the thickness deformation of the alloy plate is 60%-80% until the thickness deformation of the alloy plate is 60%-80%.

[0016] In the step (2) of the preparation method of the FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion, the annealing temperature is 900-1100 DEG C, the holding time is 0.5-2.5 h, and air cooling is performed to room temperature; the aging temperature is 500-900 DEG C, the holding time is 1-500 h, and water cooling is performed to room temperature.

[0017] The design idea of the application is:

[0018] The present application is mainly designed from two aspects, one is component design, adding Fe, Cr, Al elements, so that the material can quickly form an oxidation film with good protection on the surface in the high-temperature liquid lead-bismuth environment, but considering that it is difficult for the three elements to make the material quickly form a better protective Al2O3 film, therefore, Ti element is added in the material to promote the formation of Al2O3 film, which greatly improves the liquid lead-bismuth corrosion resistance of the material. In addition, due to the addition of the four elements mentioned above, the strength of the material is high and the plasticity is poor. Therefore, it is necessary to add Ni element to make the high-entropy alloy form a face-centered cubic and body-centered cubic dual-phase structure to achieve better strength and plasticity synergy. At the same time, the content of Ni needs to be controlled to avoid the dissolution of Ni element with high solubility in liquid lead-bismuth and the penetration of lead-bismuth. The other aspect is the design of heat treatment process, through cold rolling, high-temperature recrystallization annealing and low-temperature aging, the appropriate grain size is obtained, which is beneficial to improve the liquid lead-bismuth corrosion resistance and achieve better strength and plasticity synergy.

[0019] In addition, the alloy sheet is prepared by arc melting and copper mold casting method, and after homogenization treatment and rolling deformation, annealing and aging treatment are carried out, a dual-phase structure with face-centered cubic matrix and body-centered cubic ordered precipitated phase is obtained, which makes the FeNiCrAlTi high-entropy alloy have high strength and toughness. In addition, the FeNiCrAlTi high-entropy alloy can form a protective Cr and Al oxide film in the liquid lead-bismuth environment, and the alloy contains a small amount of Ti element to promote the formation of protective Al2O3 film, hinder the penetration of liquid lead-bismuth into the matrix, so that it has excellent liquid lead-bismuth corrosion resistance.

[0020] The advantages and beneficial effects of the present application are:

[0021] 1. The preparation method of the liquid lead-bismuth corrosion resistant FeNiCrAlTi high-entropy alloy of the present application is easy to realize from alloy component allocation, processing method to heat treatment process.

[0022] 2. The FeNiCrAlTi high-entropy alloy of the present application shows excellent corrosion resistance under saturated oxygen and oxygen-poor conditions at 550 DEG C.

[0023] 3. The FeNiCrAlTi high-entropy alloy of the present application has a dual-phase structure of face-centered cubic and body-centered cubic, high strength and good plasticity, and is easy to deform.

[0024] 4. The liquid lead-bismuth corrosion resistant FeNiCrAlTi high-entropy alloy of the present application is a new alloy design scheme based on the existing nuclear structural materials, which can meet the performance requirements of high strength and toughness and liquid lead-bismuth corrosion resistance. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is the surface morphology SEM graph of Example 3 of the present application.

[0026] Figure 2 Engineering stress-strain diagram of the embodiment of the present application.

[0027] Figure 3 SEM image of the cross-sectional morphology of the embodiment 3 of the present application after 1000h immersion in oxygen-saturated liquid lead bismuth at 550℃.

[0028] Figure 4 SEM image of the cross-sectional morphology of the embodiment 3 of the present application after 1000h immersion in oxygen-poor (D O =10 -7 wt.%) liquid lead bismuth at 550℃. DETAILED DESCRIPTION

[0029] In the specific implementation process, the present application provides a FeNiCrAlTi high-entropy alloy resistant to liquid lead bismuth corrosion, the chemical composition, microstructure, preparation method and liquid lead bismuth corrosion experiment steps of the alloy are as follows:

[0030] 1. The chemical composition of the high-entropy alloy is as follows in terms of weight percentage: Fe: 35-55%; Ni: 20-35%; Cr: 10-20%; Al: 5-15%; Ti: 1-10%.

[0031] 2. The microstructure characteristics of the high-entropy alloy are described as follows:

[0032] (1) The microstructure of the alloy is a dual-phase structure of face-centered cubic and body-centered cubic.

[0033] (2) The face-centered cubic phase is an unordered structure matrix phase rich in Fe and Cr.

[0034] (3) The body-centered cubic phase is an ordered B2-Ni(Al, Ti) phase, which is dispersedly distributed in the face-centered cubic matrix phase.

[0035] 3. The preparation method of the high-entropy alloy comprises the following steps:

[0036] (1) The metal raw materials with a purity of greater than 99.95wt.% are weighed according to the preset component ratio, the alloy chemical composition is shown in Table 1, the vacuum chamber is first pre-evacuated to an air pressure of 3.5×10 -3 Pa, then high-purity argon gas (volume purity 99.999%) is filled to make the air pressure of the vacuum chamber 4×10 4 Pa. The alloy smelting current is 350A, each smelting is 3 minutes, the alloy is turned over after each smelting and smelted again, at least repeated for 6 times, until the alloy composition is uniform, and the alloy ingot is taken out after cooling; the alloy ingot is heated and melted by arc smelting, the alloy melt is quickly poured into a copper mold of corresponding size by using the copper mold casting method, and the alloy plate with a size of 60mm×24mm×4mm is obtained.

[0037] (2) The alloy plate is homogenized, sealed in a vacuum quartz tube, and the air pressure in the vacuum quartz tube is 2x10 - 3 Pa, the homogenization temperature is 1100℃, the holding time is 2h, and the water cooling is to room temperature; the double-track rolling mill is used to roll to the required thickness at room temperature along the fixed direction with small step and multiple passes, the rolling reduction of each pass is 0.2mm, and a total of 12 passes are rolled, that is, the thickness of the alloy plate is reduced from the original 4mm to 1.6mm.

[0038] (3) The cold-rolled plate is annealed and aged, sealed in a vacuum quartz tube, and the air pressure in the vacuum quartz tube is 2x10 -3 Pa, the annealing temperature is 1000℃, the holding time is 1h, and the air cooling is to room temperature; the aging temperature is 700℃, the holding time is 50h, and the water cooling is to room temperature, to obtain the FeNiCrAlTi high-entropy alloy.

[0039] 4. The liquid lead-bismuth corrosion experiment steps of the high-entropy alloy are as follows:

[0040] (1) First, the temperature of the liquid lead-bismuth soaking furnace is increased to 170-180℃, the cover is opened, the sample is put into the furnace, the cover is closed, and the temperature is increased to 550℃.

[0041] (2) The liquid lead-bismuth soaking furnace for the oxygen-poor condition experiment needs to control the oxygen concentration to about 10 - 7 wt.% by using an oxygen control device, and the experiment starts.

[0042] (3) After soaking for 1000h, the temperature is reduced to 170-180℃, the cover is opened, and the FeNiCrAlTi high-entropy alloy sample is taken out.

[0043] Next, the application is further described in detail through examples.

[0044] Example

[0045] Table 1 Chemical composition of the alloy (wt.%)

[0046] Fe Ni Cr Al Ti Example 1 47.50 29.95 14.74 5.10 2.71 Example 2 47.59 28.90 14.77 5.11 3.63 Example 3 47.69 27.85 14.80 5.12 4.54

[0047] Table 2 Room temperature mechanical properties of the example of the application

[0048] Yield strength (MPa) Tensile strength (MPa) Elongation (%) Example 1 910 1280 19 Example 2 921 1270 14 Example 3 1013 1271 10

[0049] As Figure 1As shown, the three high-entropy alloys of Example 1-Example 3 are all composed of face-centered cubic and body-centered cubic dual-phase structures, and the ordered body-centered cubic phase rich in Ni, Al and Ti is dispersedly distributed in the face-centered cubic matrix phase rich in Fe and Cr. The tensile samples with a gauge length of 16 mm, a cross-section size of 2.5 mm x 1.5 mm and a total length of 38 mm are cut from the high-entropy alloy plate by wire cutting. The room temperature tensile test is performed by using an Instron 5582 universal material testing machine, and the tensile rate is 1 x 10 -3 s -1 The tensile curve of the alloy is shown in Figure 2 , and the room temperature mechanical properties are listed in Table 2. The yield strength of the high-entropy alloy of the present application is above 910 MPa, the tensile strength can reach above 1270 MPa, and the elongation can be maintained above 10%. The liquid lead-bismuth immersion test samples with a size of 15 mm x 10 mm x 1.5 mm are cut from the high-entropy alloy plate, and after these samples are respectively corroded in 550℃ saturated oxygen and oxygen-poor (D O = 10 -7 wt.%) liquid lead-bismuth for 1000 h, the cross-sectional morphology is shown in Figure 3 and 4 . The Example 3 of the present application does not dissolve and corrode under the conditions of saturated oxygen and oxygen-poor.

[0050] The experimental results show that the dual-phase structure FeNiCrAlTi high-entropy alloy of the present application not only has good strength and plasticity synergy, but also has excellent corrosion resistance in 550℃ saturated oxygen and oxygen-poor liquid lead-bismuth, and can simultaneously meet the performance requirements of high strength and toughness, high temperature resistance and liquid lead-bismuth corrosion resistance.

Claims

1. A FeNiCrAlTi high-entropy alloy resistant to liquid lead bismuth corrosion, characterized in that, The high-entropy alloy has the following chemical composition in percentage by weight: Fe: 47.69%; Ni: 27.85%; Cr: 14.80%; Al: 5.12%; Ti: 4.54%; the yield strength of the high-entropy alloy under room temperature is 1013 MPa, the tensile strength is 1271 MPa, and the elongation is 10%; The microstructure of the high-entropy alloy is characterized by dual-phase structure of face-centered cubic and body-centered cubic, the face-centered cubic phase is an unordered structure matrix phase rich in Fe and Cr, and the body-centered cubic phase is an ordered B2-Ni(Al, Ti) phase, which is dispersedly distributed in the face-centered cubic matrix phase; The FeNiCrAlTi high-entropy alloy can form a protective Cr and Al oxide film in a liquid lead-bismuth environment, and the alloy contains a small amount of Ti element to promote the formation of a protective Al2O3 film, hinder the infiltration of liquid lead-bismuth into the matrix, and thus has excellent resistance to liquid lead-bismuth corrosion; FeNiCrAlTi high-entropy alloy was saturated in oxygen and oxygen-poor D O =10 -7 No dissolution corrosion occurred after 1000 h of corrosion in liquid lead-bismuth.

2. A method of preparing the FeNiCrAlTi high-entropy alloy resistant to corrosion by liquid lead bismuth according to claim 1, characterized in that, The method comprises the following steps: (1) The raw materials are weighed according to the preset component ratio, and the raw materials are placed in a vacuum chamber to be electric arc melted under the protection of a homogeneous atmosphere to prepare an alloy ingot, and then the copper mold casting method is used to cast the alloy into an alloy plate; (2) The alloy plate is subjected to homogenization treatment, rolling deformation treatment, annealing and aging treatment to obtain the FeNiCrAlTi high-entropy alloy.

3. The method for preparing the FeNiCrAlTi high-entropy alloy resistant to liquid lead-bismuth corrosion according to claim 2, characterized in that, In step (1), the vacuum chamber is first pre-evacuated to an air pressure below 1 × 10 -2 Pa, then high-purity argon is filled to make the air pressure of the vacuum chamber 3 × 10 4 ~ 9 × 10 4 Pa, and then arc melting is performed with a melting current of 280 ~ 500 A, and the alloy melt is poured into a copper mold of a corresponding size to obtain an alloy plate.

4. The method of claim 2, wherein the FeNiCrAlTi high-entropy alloy is prepared by the following steps of: preparing a mixed powder of Fe, Ni, Cr, Al, and Ti; and sintering the mixed powder at a temperature of 1,000°C to 1,200°C for 1 to 10 hours in a vacuum or an inert gas atmosphere. In step (2), the homogenization treatment temperature is 1000-1250 ℃, the holding time is 1-4 h, and the water cooling is to room temperature; the rolling deformation treatment is room temperature rolling, the rolling direction of the alloy plate is along the length direction, the alloy plate is rotated by 180° after each rolling pass, the rolling reduction per pass is 0.1-0.3 mm, and the thickness deformation of the alloy plate is 60%-80% until the thickness deformation of the alloy plate is 60%-80%.

5. The method of claim 2, wherein the FeNiCrAlTi high-entropy alloy is prepared by the following steps of: preparing a mixed powder of Fe, Ni, Cr, Al, and Ti; and sintering the mixed powder at a temperature of 1,000°C to 1,200°C for 1 to 10 hours in a vacuum or an inert gas atmosphere. In step (2), the annealing temperature is 900-1100 ℃, the holding time is 0.5-2.5 h, and the air cooling is to room temperature; the aging temperature is 500-900 ℃, the holding time is 1-500 h, and the water cooling is to room temperature.

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