Low-cost iron-based medium-entropy alloy and preparation and application thereof

Abstract

The invention discloses a low-cost iron-based medium-entropy alloy as well as preparation and application thereof, and aims to solve the technical problem of realizing cost benefit maximization while ensuring the performance of the iron-based medium-entropy alloy. The alloy chemical expression of the medium-entropy alloy is Fe (75-x) Ni (x) Cr (14-16) Si (6.5-7.5) Al (2.5-3.5), and 11 lt, and x is less than or equal to 13. Compared with the prior art, the performance of the FeNiCrSiAl alloy with different Ni contents is compared, and it is found that when the Ni content of the alloy is larger than 11% and smaller than 13%, the basic performance (good strength, hardness and plasticity) of the alloy can be guaranteed, the alloy cost can be greatly reduced, and then application of the alloy is facilitated.

Description

Technical Field

[0001] The present invention relates to the technical field of iron-based alloys, and in particular to a low-cost iron-based medium-entropy alloy and its preparation and application. Background Art

[0002] In the field of alloy material science, FeNiCrSiAl alloy is favored in many industrial applications due to its unique physical and chemical properties, such as excellent corrosion resistance, high temperature stability and good mechanical properties. However, the high cost of raw materials has always been one of the main obstacles restricting its widespread application. In order to meet this challenge, technicians have conducted in-depth research on the specific effects of each element (Fe, Ni, Cr, Si, Al) in the alloy on the properties of the alloy, and carefully designed the composition of the FeNiCrSiAl alloy, striving to achieve effective cost control by adjusting the proportion of elements and adding other low-cost elements while ensuring that the basic properties of the alloy are not reduced.

[0003] The inventors know of a FeNiCrSiAl alloy (CN 116574979 A), which specifically discloses two low-cost, high-strength and ductile iron-based medium-entropy alloys, namely Fe 62 Ni 15 Cr 13 Si 7 Al 3 and Fe 62 Ni 15 Cr 13 Si 3 Al 7 In order to ensure the excellent mechanical properties of the alloy, more Ni elements are added. However, as a precious metal element, the addition of Ni elements significantly increases the cost of the alloy, which in turn restricts the application of the alloy.

[0004] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure, and should not be regarded as acknowledging or suggesting in any form that the information constitutes the prior art known to those skilled in the art. Summary of the invention

[0005] The inventors found through research that when the addition amount of Ni in the FeNiCrSiAl alloy is 13 at. %, both its as-cast structure and the structure after rolling and annealing are BCC (B2) + FCC duplex phases. When the addition amount of Ni in the FeNiCrSiAl alloy is 11 at. %, the as-cast structure of the alloy is a single BCC phase. If the addition amount of Ni in the FeNiCrSiAl alloy is adjusted to 12 at. %, the as-cast structure of the alloy is mainly BCC (B2), and at the same time contains a very small amount of FCC. After rolling and annealing, its structure transforms into BCC (B2) + FCC. Thus, a reasonable addition amount of Ni can further reduce the cost of the alloy while ensuring excellent properties of the alloy (good strength, hardness, and plasticity).

[0006] According to one aspect of the present disclosure, there is provided a low-cost iron-based medium-entropy alloy, and in atomic percentage, its alloy chemical formula is Fe 75-x Ni x Cr 14-16 Si 6.5-7.5 Al 2.5-3.5 , where 11 < x ≤ 13.

[0007] In some embodiments of the present disclosure, the alloy chemical formula is Fe 75-x Ni x Cr 15 Si 7 Al 3 .

[0008] In some embodiments of the present disclosure, the alloy chemical formula is Fe 62 Ni 13 Cr 15 Si 7 Al 3 .

[0009] In some embodiments of the present disclosure, the alloy chemical formula is Fe 63 Ni 12 Cr 15 Si 7 Al 3 .

[0010] According to another aspect of the present disclosure, there is provided a method for preparing a low-cost iron-based medium-entropy alloy, including the following steps: (1) According to the alloy chemical formula Fe 75-x Ni x Cr 14-16 Si 6.5-7.5 Al 2.5-3.5 , where 11 < x ≤ 13, calculate the required amounts of each element, and use high-purity metal elements for proportioning; (2) Mixing the prepared high-purity metal elements and performing vacuum melting to obtain a molten alloy; (3) Casting the alloy liquid to obtain a cast alloy.

[0011] According to a third aspect of the present disclosure, a method for preparing a low-cost iron-based medium-entropy alloy plate is provided, comprising the following steps: (1) performing multiple passes of rolling of the cast alloy to obtain an alloy plate; (2) The alloy plate is annealed at 750-850° C. for 8-12 min, and then immediately water-cooled.

[0012] According to a fourth aspect of the present disclosure, the above-mentioned low-cost iron-based medium-entropy alloy is applied in the preparation of low-temperature resistant products.

[0013] One or more technical solutions provided in the embodiments of the present application have at least any of the following technical effects or advantages: Fe 62 Ni 15 Cr 13 Si 7 Al 3 The research was based on the alloy and found that when the Ni addition of the alloy was 11%, the alloy was a single BCC phase, which made it impossible to roll due to its high strength and hardness; when the Ni addition of the alloy was 11-13%, the structure after rolling annealing was BCC (B2) + FCC phase, which ensured that the alloy properties (basic mechanical properties at room temperature and liquid nitrogen temperature) were not reduced, and even the plasticity was improved, while the Ni content was reduced to the maximum extent, thereby reducing the cost of alloy raw materials and maximizing cost-effectiveness, which was beneficial to the expanded application of FeNiCrSiAl alloy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 This is a phase distribution diagram of the alloy Ni11, Ni12, and Ni13 in the cast state, tensile state, and electron backscatter diffraction technology (EBSD) in one embodiment of the present application, where AC represents the cast state.

[0015] Figure 2 This is a backscattered electron imaging (BSE) image of the cast state of alloy Ni12 in one embodiment of the present application.

[0016] Figure 3 This is a transmission electron microscope (TEM) image of the cast state of alloy Ni12 in one embodiment of the present application.

[0017] Figure 4 This is a macroscopic diagram of the rolling of alloys Ni11, Ni12, and Ni13 in one embodiment of the present application.

[0018] Figure 5 This is a compression curve diagram of alloy Ni12 in one embodiment of the present application.

[0019] Figure 6 This is a TEM image of alloy Ni12 in the rolled annealed state in one embodiment of the present application.

[0020] Figure 7 This is a tensile curve diagram of alloys Ni12 and Ni13 after 85% rolling + 800℃-10min annealing in an embodiment of the present application, as well as a performance and cost comparison diagram of alloy Ni12, in which R represents rolling and ANN represents annealing. DETAILED DESCRIPTION

[0021] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0022] Unless otherwise specified, the instruments and equipment involved in the following embodiments are all conventional instruments and equipment; the metal raw materials involved are all commercially available conventional metal raw materials unless otherwise specified; the processing and manufacturing methods and testing methods involved are all conventional methods unless otherwise specified.

[0023] Embodiment 1 This example discloses a method for preparing a low-cost iron-based medium-entropy alloy, using metal elements with a purity greater than 99.9 wt.% as raw materials, in terms of atomic percentage, Fe 62~64%, Ni 11~13%, Cr 14~16%, Si6.5~7.5%, Al 2.5~3.5%. Weigh each raw material according to the above atomic percentage, place all raw materials in a high vacuum arc furnace protected by argon gas, and melt at least 4 times under electromagnetic stirring. At the same time, the alloy ingot needs to be turned over after each melting to ensure uniform composition, and then cast it into a 10*10*30mm 3 The cast alloy ingot is obtained in a water-cooled copper mold, and finally the cast alloy ingot is rolled for multiple passes of 85% at room temperature, with a reduction of 0.1 mm in each pass and a rolling speed of 10 rpm. The rolled plate is annealed at 800°C for 10 min, and then water-cooled after annealing to obtain the iron-based medium-entropy alloy.

[0024] Embodiment 2 According to the composition of Fe 64 Ni 11 Cr 15 Si 7 Al 3 The ingredients were prepared according to the alloy preparation method described in Example 1 to obtain alloy Ni11.

[0025] Example 3 According to the composition of Fe63 Ni 12 Cr 15 Si 7 Al 3 The ingredients were prepared according to the alloy preparation method described in Example 1 to obtain alloy Ni12.

[0026] Embodiment 4 According to the composition of Fe 62 Ni 13 Cr 15 Si 7 Al 3 The ingredients were prepared according to the alloy preparation method described in Example 1 to obtain alloy Ni13.

[0027] The mechanical properties and microstructure of the iron-based medium entropy alloys (Ni content of 11%, 12%, and 13% respectively) prepared in the above-mentioned Examples 2 to 4 were tested in the cast state. The results are as follows: Figure 1 As shown, the as-cast tensile results show that Fe 64 Ni 11 Cr 15 Si 7 Al 3 and Fe 63 Ni 12 Cr 15 Si 7 Al 3 All alloys show heterogeneous fracture. 62 Ni 13 Cr 15 Si 7 Al 3 The alloy has a certain plasticity. EBSD phase distribution results show that Fe 62 Ni 13 Cr 15 Si 7 Al 3 The presence of BCC (B2) + FCC in the cast alloy gives it an excellent match between strength and plasticity, as well as good high-temperature stability and damage tolerance. This dual-phase structure effectively improves the comprehensive mechanical properties of the alloy through mechanisms such as heterogeneous deformation-induced hardening and crack propagation barrier. 63 Ni 12 Cr 15 Si 7 Al 3 The alloy is mainly composed of BCC (B2) structure, and there is a very small amount of FCC structure, which makes the alloy have higher strength and hardness, relatively low plasticity, but takes into account the processing performance; Fe 64 Ni 11 Cr 15 Si 7 Al3 The presence of only a single BCC in the alloy makes the alloy very strong and hard, but has low plasticity, is difficult to roll, has poor machinability, and is difficult to process and shape.

[0028] In addition, Fe 63 Ni 12 Cr 15 Si 7 Al 3 BSE and TEM test of alloy casting, BSE results ( Figure 2 ) shows that Fe 62 Ni 13 Cr 15 Si 7 Al 3 The content of as-cast FCC phase is significantly higher than that of Fe 63 Ni 12 Cr 15 Si 7 Al 3 Cast FCC phase, and Fe 63 Ni 12 Cr 15 Si 7 Al 3 The FCC phase in the alloy mainly precipitates at the BCC grain boundaries. Figure 3 TEM results show that massive FCC is distributed on the continuous BCC matrix, and NiAl nano-precipitates (B2 phase) are distributed on the BCC matrix.

[0029] Embodiment 5 In this example, the rolling effects of the iron-based medium entropy alloys (Ni content of 11%, 12%, and 13% respectively) prepared in Examples 2 to 4 are compared. The results are as follows: Figure 4 As shown, the results show that Fe 62 Ni 13 Cr 15 Si 7 Al 3 The alloy exhibits excellent plasticity and surface finish during rolling; while Fe 63 Ni 12 Cr 15 Si 7 Al 3 The alloy is prone to produce metal debris or irregular edges at the edges after rolling; Fe 64 Ni 11 Cr 15 Si 7 Al 3 During rolling, due to insufficient plasticity, breakage easily occurs, resulting in cracks in the material, making it impossible to form through the rolling process.

[0030] Furthermore, Fe 63 Ni 12 Cr 15 Si 7 Al 3 The alloy was subjected to TEM examination in the rolled annealed state and compared with Fe 62 Ni 13 Cr 15 Si 7 Al 3 The mechanical properties were compared and the mechanical properties under compression were tested. The results are shown in Table 1. Figure 5 , Figure 6 , Figure 7 As shown, the results show that Fe 63 Ni 12 Cr 15 Si 7 Al 3 The FCC structure distributed along the grain boundaries in the alloy casting structure makes the alloy brittle when stretched, but has good deformation ability during rolling. 63 Ni 12 Cr 15 Si 7 Al 3 The alloy has good plasticity when compressed. At the same time, compared with other medium / high entropy alloys, Fe 63 Ni 12 Cr 15 Si 7 Al 3 The alloy not only has good mechanical properties but also has lower raw material cost.

[0031] Table 1 Fe 63 Ni 12 Cr 15 Si 7 Al 3 with Fe 62 Ni 13 Cr 15 Si 7 Al 3 Comparison of Alloy Mechanical Properties .

[0032] Although some preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0033] Obviously, those skilled in the art can make various changes and modifications to the present application without departing from the spirit and scope of the inventive concept. Thus, if these modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is also intended to include these modifications and variations.

Claims

1. A low-cost iron-based medium-entropy alloy, characterized in that: In terms of atomic percentage, the alloy chemical formula is Fe 75- x Ni x Cr 14-16 Si 6.5-7.5 Al 2.5-3.5 , of which 11 <x≤13。 2. The low-cost iron-based medium-entropy alloy according to claim 1, characterized in that: Its alloy chemical formula is Fe 75- x Ni x Cr 15 Si7Al3.

3. The low-cost iron-based medium-entropy alloy according to claim 2, characterized in that: Its alloy chemical formula is Fe 62 Ni 13 Cr 15 Si7Al3.

4. The low-cost iron-based medium-entropy alloy according to claim 2, characterized in that: Its alloy chemical formula is Fe 63 Ni 12 Cr 15 Si7Al3.

5. A method for preparing a low-cost iron-based medium-entropy alloy, characterized in that: The steps include: (1)According to the alloy chemical formula Fe 75-x Ni x Cr 14~16 Si 6.5~7.5 Al 2.5~3.5 , where 11 < x ≤ 13, calculate the required amounts of each element, and use high-purity metal elements for proportioning; (2) Mixing the prepared high-purity metal elements and performing vacuum melting to obtain a molten alloy; (3) Casting the alloy liquid to obtain a cast alloy.

6. A method for preparing a low-cost iron-based medium-entropy alloy sheet, characterized in that: The steps include: (1) subjecting the cast alloy obtained in claim 5 to 80-85% multi-pass rolling to obtain an alloy plate; (2) The alloy plate is annealed at 750-850° C. for 8-12 min, and then immediately water-cooled.

7. Use of the low-cost iron-based medium-entropy alloy according to claim 1 in the preparation of low-temperature resistant products.

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